Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
216 PM EST Mon Dec 05 2022

Valid 00Z Tue Dec 06 2022 - 00Z Thu Dec 08 2022

...Heavy rain and isolated flash flooding possible from the Southern
Appalachians/Tennessee Valley region into the Lower Mississippi Valley...

...Much above average temperatures on tap from the Central and Southern
Plains, eastward into the east. Below average temperatures expected
across areas west of the Rockies and across the Northern Plains...

...Accumulating snows possible across the Northern Plains and through
portions of the Rockies...

There is a heavy rain threat with isolated flash flooding over the next
few days across a large portion of the nation from the Southern
Appalachians/Tennessee Valley region, west southwestward into the Lower
Mississippi Valley. A slow moving surface frontal boundary
will remain across these areas for the next few days, helping to pool
above average levels of moisture near this front, supporting heavy rains
and the potential for isolated flash flooding. The first round of
potentially heavy rains along this front will be from this afternoon into
early Tuesday across the Tennessee Valley into the Southern Appalachians.
This will be followed by a second round of heavy rain developing Wednesday
from the Southern Plains, across the Lower Mississippi Valley and into the
Tennessee Valley. Portions of these regions have had above average
precipitation over the past few weeks, resulting in increasingly saturated
soils, with heavy rain potential on these saturated soils increasing the
flash flood threat. While not as heavy as across the above mentioned
regions, wet weather also likely from the Mid-Atlantic into the Northeast
during Tuesday and Wednesday.

The overall pattern supporting the wet weather from the Southern Plains
into the Northeast will also support much above average temperatures over
the next few days from the Central to Southern Plains, eastward into the
east. A few record high minimum temperatures possible Tuesday morning
across the Lower Mississippi Valley, with a much more expansive area of
potentially record high minimum temperature possible Wednesday morning
across portions of the Southern Plains, Lower Mississippi Valley,
Tennessee Valley, Mid Atlantic and northeast.

Below average temperatures over the next few days are expected across
areas west of the Rockies and across the Northern Plains. The greatest
below average temperatures are expected across the Northern Plains where
arctic air will keep temperatures 15-20 degrees below average from eastern
Montana, across the Dakotas and into Minnesota. There are, however, not
expected to be any record cold temperatures across this region over the
next two days. This area will also see the threat of periods of
accumulating snows over the next two days. Amounts are not expected to be
very heavy, generally in the 1 to 4 inch range. The heaviest snows over
the next few days expected through the Rockies of Colorado, northwest
Montana and northern Idaho where totals in excess of a foot are possible

Oravec

Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
324 PM EST Mon Dec 05 2022

Valid 12Z Thu Dec 08 2022 - 12Z Mon Dec 12 2022

...Guidance/Predictability Assessment...

The overall pattern for the next week will be transitioning from a
West Coast trough/Southeast ridge to a more broad trough with a
generally southwest flow regime across the CONUS. However due to
the degree of spread with the timing, location, and amplitude
differences shortly after the initial period, confidence in any of
the specifics is below average. The WPC medium range product suite
was primarily derived from a blend of the ECWMF/GFS with lesser
weighting of the CMC/UKMET to start and as the time goes on the
inclusion and weighting of the ECWMF ensemble/GEFS means were
increased- ending the with 50% means/50% deterministic by the end
of the forecast. This helped maintain continuity and reduce the
noise within the guidance. Additionally, it led to a bit of a slow
down in the frontal progression across the central CONUS for Days
5-7 when compared to the previous forecast. As previously noted,
the usage of the ensemble means is more problematic than usual
given the GEFS/ECMWF envelope of forecasts become more out of sync
than normal later period from the east-central Pacific into the
lower 48, with no clear signal to differentiate in a data
sensitive pattern. Accordingly, pattern evolution predictability
seems below normal from the weekend into early next week, mainly
due to small to larger scale differences with aspects of the
digging of trough energy into the West and subsequent downstream
progression.

...Weather/Hazard Highlights...

Energetic impulses are expected to eject from the upper-level
trough across the central U.S and with lead frontal moisture
pooling will spread a swath of moderately heavy rains through the
Ohio Valley states and central Appalachians/Mid-Atlantic Thursday
and Friday. It may linger into Saturday by uncertain/moderate
coastal low genesis. The models seem to reasonably show a
potentially more ample QPF signature than the NBM given support,
albeit with less than stellar run to run axis placement. There is
also some potential for a swath of snow/ice during this period on
the cooled northern periphery of this precipitation shield from
the Midwest through the Northeast. Some of the rains moving across
the Tennessee/Ohio Valleys through Friday morning, have increased
soil saturation from recent rainfall, may reach or exceed local
flash flood guidance and see isolated areas of flash flooding. The
elevated risk for runoff and flash flooding will shift to portions
of the Appalachians and the Delmarva region into Saturday morning
as the area of rain shifts eastward.

Meanwhile upstream, ample system energies digging southeastward
from the Gulf of Alaska are slated to work into the West
Thursday/Friday and renew moderately heavy precipitation chances
into the Northwest and northern California to include a threat for
enhanced terrain/mountain snows that will spread over an unsettled
West/Rockies. The pattern seems to then offer an emerging moderate
setup for rainfall over the east-central U.S. next weekend into
early next week as western U.S. upper trough energies work
uncertainly downstream as return Gulf moisture intercepts a
developing/wavy frontal system. The pattern also seems favorable
for renewed moderately heavy precipitation including
terrain/mountain enhanced snows inland into the Northwest/West
again by next weekend as additional northeast Pacific system
energies work inland into the unsettled region. The spread in the
guidance has persistently been all over the place from run to run
with system focus and/or existence. The rainfall amounts and
location of this precipitation may change significantly over the
next few days as the models work out various issues.

Campbell/Schichtel


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

Hazards:
- Heavy precipitation across portions of the Central Plains, the
Middle Mississippi Valley, the Great Lakes, and the Upper
Mississippi Valley, Thu, Dec 8.
- Heavy precipitation across portions of the Great Lakes, the
Mid-Atlantic, the Northeast, the Central Appalachians, and the
Ohio Valley, Fri, Dec 9.
- Heavy rain across portions of California and the Pacific
Northwest, Thu-Mon, Dec 8-Dec 12.
- Heavy rain across portions of the Middle Mississippi Valley, the
Lower Mississippi Valley, and the Southern Plains, Sat-Sun, Dec
10-Dec 11.
- Heavy rain across portions of the Central Plains, the Middle
Mississippi Valley, the Great Lakes, and the Ohio Valley, Thu, Dec
8.
- Heavy rain across portions of the Lower Mississippi Valley, the
Central Appalachians, the Tennessee Valley, the Middle Mississippi
Valley, the Southern Appalachians, and the Ohio Valley, Thu-Fri,
Dec 8-Dec 9.
- Heavy snow across portions of California, the Central Great
Basin, the Pacific Northwest, and the Northern Great Basin,
Thu-Mon, Dec 8-Dec 12.
- Heavy snow across portions of the Northern Rockies and the
Northern Great Basin, Fri-Sat, Dec 9-Dec 10.
- Heavy snow across portions of the Central Great Basin and the
Northern Great Basin, Sat-Sun, Dec 10-Dec 11.
- Much below normal temperatures across portions of the Alaska
Panhandle and mainland Alaska, Fri-Mon, Dec 9-Dec 12.

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, experimental excessive rainfall
outlook, winter weather outlook probabilities and heat indices are
at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
201 AM EST Mon Dec 05 2022

Valid 00Z Tue Dec 06 2022 - 00Z Tue Dec 13 2022

...Kona low development just northwest of the state favors a
early-midweek heavy rain threat...

The GFS/ECMWF/UKMET/Canadian models and supportive ensembles offer
a similar pattern evolution for the coming week, bolstering
forecast confidence. There is a strong signal to carve out a Kona
low to settle just to the northwest of the islands early week and
linger into midweek before ejecting northwestward away from the
state. A well defined surface front stalls just west of the
islands early week and a lead shift to southeasterly/southerly
winds into the islands will bring increasingly deep and sustained
moisture into the state. This will fuel a period favorable for
some heavy downpours that may lead to local runoff issues.

High pressure building strongly in guidance to the northeast of
the state in the wake of closed lo departure later week into next
weekend should then support a return moderate to breezy easterly
trades and revert to a pattern with more limited moisture and
windward terrain focusing showers under an amplifying upper ridge.
There is a growing guidance signal to monitor that shows
separated/closed low energy working southwestard and underneath
the upper ridge to just south of the islands late weekend into
early next week that if manifested could renew some shower fueling
moisture back into the state.

Schichtel

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
728 PM EST Mon Dec 05 2022

Day 1
Valid 16Z Mon Dec 05 2022 - 12Z Tue Dec 06 2022

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR TENNESSEE,
PORTIONS OF NORTHERN MISSISSIPPI, ALABAMA, AND GEORGIA AS WELL AS
ADJACENT COUNTIES OF THE CAROLINAS...


...Northern GA...Eastern TN...into Western Carolinas...
Favorable upper-level forcing along/ahead of weak shortwave
directly below the apex of the anticyclonically curved subtropical
jet streak (as noted in GOES-WV) continues to progress eastward
through Northern GA into the Carolinas over the next few hours.
This combined with weak isentropic ascent with the anomalously
higher total PWAT values (still over 1.5") continues to support
increased rates particularly along the leading edge of the
shortwave, but this is expected to wane quickly over the next 2-3
hours moving further away from the source region, as well as
falling into the drier low level environment east of the
Appalachian ridge. As such, have pulled the Slight Risk in favor
of a continued Marginal Risk.


...Delta Region of MS Valley into Central TN...
Further upstream, a pocket of enhanced mid-level instability due
to higher theta-E surge through LA and the Lower MS valley with
numerous Hi-Res CAMs and global guidance supporting 500-750 J/kg
of CAPE. As the air lifts north and impinges with the wavy warm
front across Southern AR across NW MS into N AL, deep layer flow
flattens and becomes more parallel to the boundary while
concurrently boundary layer is expected to ascend isentropically
across the boundary. This may allow for shallow/narrow convective
features across the Delta Region after 06z, slowly strengthening
toward 12z. While rainfall rates will continue to be generally low
given the updrafts probably will also be narrow in
appearance/coverage, there is some lower probabilities for streaks
of enhanced rainfall totals with possibilities of 1-1.5" totals
mainly along/north of the front across W TN. Given enhanced
rainfall totals today, there remains a non-zero risk for excessive
rainfall and isolated flooding concerns through the end of the
outlook period. As such, have contoured the western edges of the
Marginal Risk to account for Hi-Res CAMs and best HREF
probabilities, up to the central KY/TN boarder.

Gallina

Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
329 PM EST Mon Dec 05 2022

Day 2
Valid 12Z Tue Dec 06 2022 - 12Z Wed Dec 07 2022

The probability of excessive rainfall exceeding flash flood
guidance is less than 5 percent.

Putnam


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
330 PM EST Mon Dec 05 2022

Day 3
Valid 12Z Wed Dec 07 2022 - 12Z Thu Dec 08 2022

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
OZARKS TO THE LOWER OHIO AND TENNESSEE VALLEYS...

...16Z Update...

Increasing upper-level energy and a meandering surface boundary
will help to promote widespread continuous thunderstorms Wednesday
with anomalously high moisture increasing the chance for heavy
rainfall. Uncertainty on where impactful heavy rainfall will
occur, and the subsequent coverage of the current Slight Risk
area, is tied to the eventual location of the surface front. The
model guidance is in agreement on the potential for 2-4" of rain
over eastern Oklahoma, northern Arkansas, and southern Missouri
where storms are most likely to last through the period.
Uncertainty increases with eastward extent into the lower Ohio and
Tennessee Valleys due to both the eventual location of the surface
front and associated axis of heaviest rainfall, as well as the
duration of rainfall, which may end sooner on Wednesday evening.
The eastward extent of the Slight Risk captures where there is
enough overlap in the latest model guidance to narrow down a
region most likely to see higher rain totals, and where rain from
the prior days will lead to wetter antecedent conditions. A small
adjustment was made to include metro Nashville given the locally
higher risk for flooding in urban areas. There is a chance for
higher rainfall totals in the 2-3" range further east into
northeastern Tennessee and southeastern Kentucky, as well as
similar rain rates to areas within the Slight Risk, and an
eastward extension of the Slight Risk may be necessary in future
outlooks as confidence increases. A portion of the southwestern
extent of the Slight Risk was removed in coordination with the
OUN/Norman, OK office while the Marginal Risk was extended
southwest into northwest Texas. There was a trend in the latest
guidance for the axis of higher rainfall to extend further to the
southwest. However, there is still a good bit of uncertainty in
the eventual location of the surface front to further narrow down
an area of increased risk, and dry antecedent conditions should
also keep any instances of flash flooding isolated.

Putnam

...Previous Discussion...

The Slight Risk inherited from Day 4 was expanded for this
forecast update. A stalled out front will get a large invigoration
of upper level energy moving over it with a hyperactive 140 kt jet
streak. The southwesterly jet streak will start out the day
stretched over the Plains to the Midwest. By Thursday morning it
will extend into the Northeast. This will put the Slight Risk area
in the favorable right entrance region of the jet streak.
Meanwhile, a strengthening shortwave will race eastward in that
jet streak from the Southwest to the central Plains, intensifying
all the while. This shortwave will dip the jet stream and support
cyclogenesis across Kansas Wednesday night. This will draw polar
air over much of the northern tier of the country southward down
the lee of the Rockies. This cold air will clash with a continued
supply of Gulf moisture streaming northward across Texas into the
Slight Risk area. The moisture remains very highly anomalous for
this time of year. PWATs to 1.5 inches is 4 standard deviations
above the climatological normal...representing 95-99%
climatological percentile range.

As with previous days, while moisture will not be an issue
precluding heavy rainfall, instability sure will be. At most
instability in the Slight Risk area gets to around 500 J/kg,
particularly in OK, with lesser values further east. With that
said, unlike Tuesday, the aforementioned factors should work to
overcome this, resulting in 2-4 inches of rain in OK & AR. Further
east, rainfall totals will be lower...in the 1-3" range, but
previous days rainfall may make up for that with more saturated
soils. Confidence is still somewhat low on where the axis of
heaviest rainfall will set up. The cyclogenesis over KS supports
the area over OK & AR, a southwestward expansion in the Slight
Risk from previous forecasts...but it's much lower further east,
partly due to uncertainties in antecedent conditions across KY &
TN. It's likely further adjustments will be needed in this region.
The expansion across OK was coordinated with the TSA/Tulsa, OK
forecast office. The uncertainty with the eastward extent of the
rainfall was coordinated with the JKL/Jackson, KY, LMK/Louisville,
KY, and OKX/Nashville, TN forecast offices.

The inherited Marginal Risk across Maine was dropped in
coordination with the CAR/Caribou, ME forecast office. Rainfall
amounts of 1-1.5" are not expected to be enough to cause flash
flooding despite the saturated soils.

Wegman



Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
309 PM EST Mon Dec 05 2022

Valid 00Z Tue Dec 06 2022 - 00Z Fri Dec 09 2022

...Great Basin through the Central Rockies...
Days 1-3...

A slow moving positively tilted trough will shift onshore
California Tuesday and then drift slowly eastward Wednesday while
amplifying across the Four Corners. This feature may deepen into a
closed mid-level low over the Central Plains by Friday. Downstream
of this wave, persistent divergence will drive ascent, while
downstream confluence helps to advect moisture west to east across
the region. At the same time, a subtropical jet streak of Pacific
origin will gradually amplify and arc to the northeast, placing at
least modest LFQ ascent into the Four Corners and Great Basin
while acting in tandem with the mid-level confluence to increase
moisture downstream with PW anomalies reaching +1 to +1.5 sigma on
Wednesday. While the highest PW anomalies may be just south of the
likely region of heaviest snow, there will still be sufficient
moisture to wring out as heavy snow, especially where the presence
of a stationary front wavering across CO/UT helps to enhance fgen,
resulting in heavier snow rates of 0.5" to 1" per hour. The
guidance has slowed the advance of the mid-level energy and
associated weak surface wave that may develop in the lee of the
Rockies, which has resulted in yet another increase in snowfall,
especially in the terrain of the CO Rockies. WPC probabilities
feature a high risk for more than 4 inches each of the 3 days
across the CO Rockies, and for Days 1-2 in the southern Wasatch,
Kaibab Plateau, and terrain across central NV. The heaviest snow
during the period is likely in CO, especially atop the higher
terrain of the Flat Tops, Sawatch, and San Juans, where 3-day
total snowfall will likely exceed 1 foot above 5000 ft, with snow
levels crashing D3 finally as the precip begins to wane and extend
to the east.


...Montana/northern Idaho...
Days 1-2...

Expansive mid-level low centered over northern Manitoba will spin
nearly in place through Wednesday before weakening and ejecting to
the east on Thursday. Around this feature, spokes of vorticity
will rotate cyclonically through pinched flow, driving periods of
PVA and pushing a cold front southward on Tuesday into MT. This
front will then likely waver nearly in place Wednesday while a
secondary lobe of vorticity swings around the upper gyre and the
Canadian surface high sinks southeast across Saskatchewan. A
northern stream jet streak progged to dive out of British Columbia
will place favorable LFQ ascent into MT Tuesday into Wednesday,
which will combine with at least modest low-level fgen and upslope
flow to enhance snowfall from the Northern Rockies through the
High Plains of MT, with lighter snows extending eastward into the
Northern Plains embedded within the jet streak aloft. Total
snowfall should be modest, generally less than 4 inches outside of
terrain features, but WPC probabilities for more than 4 inches are
above 80% in the Northern Rockies D1, with heavy snow likely
impacting Marias Pass, and 30-50% farther east into the area
around the Bears Paw Mountains and Little Belts/Big Snowy range.
For D2, lingering heavy snow accumulating more than 4 inches is
likely to be confined to the Northern Rocky Mountain front. More
than 2 inches of snow, with locally more than 4 inches possible,
is likely in a band from central MT through much of ND.


...Pacific Northwest...
Day 3...

A closed low exiting the Gulf of Alaska late Thursday will impinge
onto the Pacific Northwest coast producing height falls and PVA
into the area. Downstream of this low, confluent flow will
transport moisture eastward within a modest AR characterized by
GEFS IVT exceeding 250 kg/m/s. This will be accompanied by
increased WAA as mid-level flow backs to the SW ahead of the
trough axis, and at least subtle upper diffluence as a Pacific jet
streak surges towards the coast. The WAA will raise snow levels,
but only modestly to around 3000 ft, and generally west of the
Cascades, with snow levels east into the Columbia Basin and
Willamette Valley remaining less than 500-1000 ft. WPC
probabilities for more than 4 inches of snow are above 80% in the
WA Cascades and Olympics, and 40-60% as far south as the
Shasta/Trinity ranges in northern CA, with more than 10 inches of
snow likely in the higher terrain, especially of WA state. While
lowland snow is not currently progged to be significant D3,
moderate to heavy accumulations are likely at or below pass levels
in the Cascades. Additionally, more widespread and even lower
snowfall accumulations are likely just beyond this forecast period.


For Days 1-3, the probability of significant icing exceeding 0.10
inch is less than 10%.

Weiss

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
324 PM EST Mon Dec 05 2022

Valid 12Z Thu Dec 08 2022 - 12Z Mon Dec 12 2022

...Guidance/Predictability Assessment...

The overall pattern for the next week will be transitioning from a
West Coast trough/Southeast ridge to a more broad trough with a
generally southwest flow regime across the CONUS. However due to
the degree of spread with the timing, location, and amplitude
differences shortly after the initial period, confidence in any of
the specifics is below average. The WPC medium range product suite
was primarily derived from a blend of the ECWMF/GFS with lesser
weighting of the CMC/UKMET to start and as the time goes on the
inclusion and weighting of the ECWMF ensemble/GEFS means were
increased- ending the with 50% means/50% deterministic by the end
of the forecast. This helped maintain continuity and reduce the
noise within the guidance. Additionally, it led to a bit of a slow
down in the frontal progression across the central CONUS for Days
5-7 when compared to the previous forecast. As previously noted,
the usage of the ensemble means is more problematic than usual
given the GEFS/ECMWF envelope of forecasts become more out of sync
than normal later period from the east-central Pacific into the
lower 48, with no clear signal to differentiate in a data
sensitive pattern. Accordingly, pattern evolution predictability
seems below normal from the weekend into early next week, mainly
due to small to larger scale differences with aspects of the
digging of trough energy into the West and subsequent downstream
progression.

...Weather/Hazard Highlights...

Energetic impulses are expected to eject from the upper-level
trough across the central U.S and with lead frontal moisture
pooling will spread a swath of moderately heavy rains through the
Ohio Valley states and central Appalachians/Mid-Atlantic Thursday
and Friday. It may linger into Saturday by uncertain/moderate
coastal low genesis. The models seem to reasonably show a
potentially more ample QPF signature than the NBM given support,
albeit with less than stellar run to run axis placement. There is
also some potential for a swath of snow/ice during this period on
the cooled northern periphery of this precipitation shield from
the Midwest through the Northeast. Some of the rains moving across
the Tennessee/Ohio Valleys through Friday morning, have increased
soil saturation from recent rainfall, may reach or exceed local
flash flood guidance and see isolated areas of flash flooding. The
elevated risk for runoff and flash flooding will shift to portions
of the Appalachians and the Delmarva region into Saturday morning
as the area of rain shifts eastward.

Meanwhile upstream, ample system energies digging southeastward
from the Gulf of Alaska are slated to work into the West
Thursday/Friday and renew moderately heavy precipitation chances
into the Northwest and northern California to include a threat for
enhanced terrain/mountain snows that will spread over an unsettled
West/Rockies. The pattern seems to then offer an emerging moderate
setup for rainfall over the east-central U.S. next weekend into
early next week as western U.S. upper trough energies work
uncertainly downstream as return Gulf moisture intercepts a
developing/wavy frontal system. The pattern also seems favorable
for renewed moderately heavy precipitation including
terrain/mountain enhanced snows inland into the Northwest/West
again by next weekend as additional northeast Pacific system
energies work inland into the unsettled region. The spread in the
guidance has persistently been all over the place from run to run
with system focus and/or existence. The rainfall amounts and
location of this precipitation may change significantly over the
next few days as the models work out various issues.

Campbell/Schichtel


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

Hazards:
- Heavy precipitation across portions of the Central Plains, the
Middle Mississippi Valley, the Great Lakes, and the Upper
Mississippi Valley, Thu, Dec 8.
- Heavy precipitation across portions of the Great Lakes, the
Mid-Atlantic, the Northeast, the Central Appalachians, and the
Ohio Valley, Fri, Dec 9.
- Heavy rain across portions of California and the Pacific
Northwest, Thu-Mon, Dec 8-Dec 12.
- Heavy rain across portions of the Middle Mississippi Valley, the
Lower Mississippi Valley, and the Southern Plains, Sat-Sun, Dec
10-Dec 11.
- Heavy rain across portions of the Central Plains, the Middle
Mississippi Valley, the Great Lakes, and the Ohio Valley, Thu, Dec
8.
- Heavy rain across portions of the Lower Mississippi Valley, the
Central Appalachians, the Tennessee Valley, the Middle Mississippi
Valley, the Southern Appalachians, and the Ohio Valley, Thu-Fri,
Dec 8-Dec 9.
- Heavy snow across portions of California, the Central Great
Basin, the Pacific Northwest, and the Northern Great Basin,
Thu-Mon, Dec 8-Dec 12.
- Heavy snow across portions of the Northern Rockies and the
Northern Great Basin, Fri-Sat, Dec 9-Dec 10.
- Heavy snow across portions of the Central Great Basin and the
Northern Great Basin, Sat-Sun, Dec 10-Dec 11.
- Much below normal temperatures across portions of the Alaska
Panhandle and mainland Alaska, Fri-Mon, Dec 9-Dec 12.

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, experimental excessive rainfall
outlook, winter weather outlook probabilities and heat indices are
at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml