Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
430 PM EDT Mon Oct 03 2022

Valid 00Z Tue Oct 04 2022 - 00Z Thu Oct 06 2022

...Rainy, breezy, and cool conditions expand from Mid-Atlantic to southern
New England coast...

...Showers and thunderstorms expected across much of New Mexico...

...Above average temperatures forecast for the West Coast, Great Plains
and Mississippi Valley...

A stagnant upper-level low will slowly rotate from the Mid-Atlantic coast
into the western Atlantic over the next couple of days. Showers and
thunderstorms will slowly spread across the Mid-Atlantic coast today
before shifting northward into parts of the New Jersey and New England
coasts on Tuesday. The prolonged nature of this rain event may cause
coastal flooding from southeast Virginia up into Long Island where Coastal
Flood Advisories and Warnings are in effect. Cool and breezy conditions
are expected to continue due to clouds and northerly flow into the region
paired with a sharp isobaric gradient along the coast. High temperature
records may be tied or broken across the Mid-Atlantic coast on Tuesday as
highs fail to make it out of the 50s.

Elsewhere, shortwave energy will supply sufficient moisture and
instability to support shower and thunderstorm activity across much of New
Mexico through Tuesday. Isolated flash flooding is possible over
susceptible land surfaces. Light showers may focus along a weak cold front
which is forecast to move through the Northern/Central Plains on Tuesday.
An amplifying upper ridge will keep things clear and warm across much of
the West with high temperatures likely to be between 10-20 degrees above
average over the next few days. An upper trough swinging through the
mid-section of the country will draw warm southerly air into the Plains
and Mississippi Valley through Wednesday.

Kebede

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
432 PM EDT Mon Oct 03 2022

Valid 12Z Thu Oct 06 2022 - 12Z Mon Oct 10 2022

...Overview...

A stubborn compact upper low/shortwave stuck over the Mid-Atlantic
region during the short range period will finally be departing off
the Northeast coast as the medium range forecast starts on
Thursday. In its wake, larger scale mean troughing should prevail
over eastern North America (led by a shortwave diving into the
Upper Great Lakes from Canada, possibly followed by a weaker
shortwave by Sunday-Monday) while a persistent upper ridge just
inland from the West Coast gradually retrogrades offshore. Despite
the somewhat amplified pattern, expect relatively quiet weather
conditions across most of the CONUS into the start of next week.
Exceptions will include some Southwest rainfall in response to
monsoonal moisture and a weak upper low settling just south of the
region, and a potent central/eastern U.S. cold front producing
some rain especially in the Great Lakes region along with
considerably cooler temperatures after its passage. The western
U.S./eastern Pacific upper ridge will support very warm
temperatures through the period.

...Guidance Evaluation/Predictability Assessment...

Latest models and ensembles maintain agreement for the general
pattern consisting of the western U.S. ridge retrograding into the
eastern Pacific as initial weak energy settles over parts of the
West, the mean trough prevailing over the eastern two-thirds of
the lower 48, and a weak Arizona/New Mexico upper low settling
over northern Gulf of California for a time before opening up by
Sunday or Monday.

Embedded details are more uncertain though. Models develop 12-24
hours or so of timing spread for the system affecting the
northeastern U.S. and southeastern Canada late this week into the
weekend. The 00Z ECMWF was fastest while the 00Z/06Z GFS were
slowest. Latest UKMET runs lean much closer to the slow side while
the 12Z CMC has trended somewhat faster than its 00Z run (now
closer to the ECMWF) and 12Z GFS accelerated to a compromise. Thus
it will take additional time to determine any conclusive trends.
Behind this system, 00Z through 12Z runs are showing an increasing
signal for another shortwave (possibly closed per the 12Z
UKMET/CMC) reaching the far northern tier by early day 6 Sunday.
This feature originates from around southern Alaska/northwestern
Canada on Sunday. There is enough agreement on its existence but
favor a conservative open wave depiction at this time since models
are inconsistent in its evolution. A blended approach looks good
for the weak energy dropping into the West (00Z CMC was extreme
with forming a closed low). Finally, current spread/run-to-run
variability suggest an intermediate solution for how late-period
Gulf of Alaska into Canada energy may break down the northern part
of the mean ridge. Based on guidance through 06Z, the updated
forecast started with an operational model composite for the first
half of the period and then trended to a half models/half ensemble
means blend by day 7 Monday. The primary continuity change was
introduction of the Sunday-Monday northern tier wave/frontal
system. QPF adjusted the 13Z National Blend of Models to reflect a
wider footprint for light amounts (mostly in the Great
Lakes/Northeast and southwestern U.S.) given the typically low
bias for light precipitation in the NBM.

...Weather/Hazards Highlights...

The combination of persistent monsoonal moisture and an upper low
settling over the northern Gulf of California will produce diurnal
showers and thunderstorms over parts of the Southwest/southern
Rockies, with locally heavy rainfall possible in some spots.
Intensity and coverage may vary from day to day, with some
eastward expansion of rainfall possible by early next week as the
upper low opens up. To the north, a cold front shifting across the
Midwest and Great Lakes may bring some light rain mainly around
Thursday, and then lake enhanced showers in the westerly flow
behind the front Friday and perhaps Saturday.

Temperatures out West will be warm into early next week underneath
a blocky upper ridge, with daytime highs over the Northwest 10 to
15 degrees or so above normal. Despite the anomalies, the
resulting temperatures peaking in the 70s and 80s (90s for parts
of California) are unlikely to create any heat related hazards.
Conversely, Canadian high pressure spilling into the north-central
U.S. and expanding eastward behind the cold front will result in
much below normal temperatures shifting from the northern Plains
into the Midwest and into much of the East Thursday-Monday.
Daytime highs in some locations could be 15 to 20 degrees below
average (mainly Thursday-Saturday) while overnight temperatures
are forecast to drop into the 30s for many locations from the
northern half of the Plains into central Appalachians, and even
20s for North Dakota and northern Minnesota particularly Friday
morning.

Rausch/Santorelli


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:
- Flooding occurring or imminent across portions of the Southeast.
- High winds across portions of the Great Lakes and the Upper
Mississippi Valley, Thu-Fri, Oct
6-Oct 7.
- Much below normal temperatures across portions of the Central
Plains, the Central Appalachians,
the Northern Plains, the Middle Mississippi Valley, the Southern
Appalachians, the Upper
Mississippi Valley, the Great Lakes, and the Ohio Valley, Sat-Sun,
Oct 8-Oct 9.

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
304 AM EDT Mon Oct 03 2022

Valid 00Z Tue Oct 04 2022 - 00Z Tue Oct 11 2022

A closed low currently to the northeast of Hawaii today will
weaken and shift northward. The associated cold front will
eventually dissipate into Tuesday over the state with east to
northeast trade winds returning behind. Behind this system,
another deep closed low will move across the Alaska Peninsula with
guidance showing good agreement it should shift due south to about
40N before becoming nearly stationary the rest of the
week/weekend, due to a blocky ridge setting up downstream over the
western U.S., although its cold front looks to remain just to the
north of Hawaii. Meanwhile, an area of tropical moisture is
forecast to move in from the east this week, setting up a wet
pattern later this week across the Big Island and possibly Maui as
well. Models overall show very good agreement in this pattern
set-up over/near Hawaii the next week. The main uncertainties lie
with the exact placement of the upper low north of Hawaii (and
whether this cold front sags south enough to affect at least the
northern islands), but these are details which could until the
short range period to resolve. A blend of the ensemble means later
in the period should provide a good starting point for now.

Santorelli

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
708 PM EDT Mon Oct 03 2022

Day 1
Valid 01Z Tue Oct 04 2022 - 12Z Tue Oct 04 2022

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST AND THE COASTAL MID-ATLANTIC STATES...


...Coastal Mid-Atlantic States...
A strong coastal low that is nearly stationary centered off the
coast of the Delmarva continues to wrap bands of mostly light to
moderate rain into portions of the Mid-Atlantic. The bands could
develop some convective elements across the Eastern Shore
overnight, and some of the activity over Long Island has shown
some modest convective tendency recently. Most of the convection
has been confined to areas over the ocean east of center. There
is greater uncertainty than usual as to where the core of the
heaviest rain will set up, so the Marginal Risk area is focused on
where rain is ongoing now along with some of the mesoscale
guidance projections, which have been shifty as of late.


...Southwest...
A shortwave dropping into the base of the upper-level trough will
encounter a rather moist airmass has triggered rounds of diurnally
driven convection. Any of these thunderstorms may produce moderate
to heavy rainfall with the potential for flash flooding over the
next several hours, especially across areas of complex terrain and
burn scar areas. QPF amounts may be as high was 1 to 2 inches
therefore the Marginal Risk remains in effect for the Four Corners
region and into parts of the lower Colorado Basin. The risk area
was expanded per recently issued Mesoscale Precipitation
Discussion #1073.

Roth/Wegman/Campbell

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
356 PM EDT Mon Oct 03 2022

Day 2
Valid 12Z Tue Oct 04 2022 - 12Z Wed Oct 05 2022

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST AND THE SOUTHERN ROCKIES/HIGH PLAINS...

...2030Z Update...

No changes made with this update. The expected precipitation
across much of NM and small portions of the neighboring states
remains unchanged.

Across the mid-Atlantic through southern New England, there
remains significant disagreement among the guidance on rainfall
locations and intensity. Thus far today, rainfall rates have been
unimpressive even in the areas getting the heaviest rain, largely
staying under 1/4 inch per hour. Thus, despite continued large
differences on where the core of the heaviest rain will be, think
rainfall rates on the whole will remain under values needed for
flash flooding. Note that portions in today's MRGL risk (southern
NJ, northern DE & Philadelphia) have low FFGs, such that rapid
training may result in an isolated flash flooding risk. Thus, a
future upgrade to a MRGL in this area may be needed for Tuesday,
but is not expected at this time.

Wegman

...Previous Discussion...

The shortwave trough will continue to dip southeast across the
southwestern U.S., pushing a cold front farther south and east
into the southern Rockies and High Plains during this period. The
anomalously moist airmass will remain pooled near the boundary
which will continue to maintain and support diurnal thunderstorms.
Some of these storms may reach or exceed 0.50 inch/hr intensities
which increases the risk for potential flash flooding. A Marginal
Risk for excessive rainfall remains in effect from southern
Arizona/New Mexico to central Colorado and the panhandles of
Oklahoma and Texas.

Campbell

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Mon Oct 03 2022

Day 3
Valid 12Z Wed Oct 05 2022 - 12Z Thu Oct 06 2022

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST AND THE SOUTHERN ROCKIES/HIGH PLAINS...

...2030Z Update...

No changes to the previous forecast were made with this update.
Expected precipitation across much of NM remains unchanged from
the previous. There is certainly some room for a localized upgrade
to a SLGT along the mountains, particularly the Sacramento
Mountains, but that will be dependent on how much rain is picked
up in this area both today and Tuesday.

For the Northeast, the coastal low will finally begin to move out
to sea on Wednesday. There will likely be lingering rain along the
Jersey Shore north to coastal RI/MA, but rainfall amounts should
stay below FFG thresholds.

Wegman

...Previous Forecast...

The frontal boundary will continue to press southward into the
Southern Plains. Showers and thunderstorms will persist along this
boundary, producing moderate to heavy rainfall across parts of the
Southwest and Southern Rockies. The threat for excessive rainfall
will remain elevated given the recent wet pattern and available
moisture to tap into. A Marginal Risk covers New Mexico, eastern
Arizona, southern Colorado and parts of western Texas.

Campbell

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
354 PM EDT Mon Oct 03 2022

Valid 00Z Tue Oct 04 2022 - 00Z Fri Oct 07 2022


The probability of significant snow or icing is less than 5%.

Mullinax

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
432 PM EDT Mon Oct 03 2022

Valid 12Z Thu Oct 06 2022 - 12Z Mon Oct 10 2022

...Overview...

A stubborn compact upper low/shortwave stuck over the Mid-Atlantic
region during the short range period will finally be departing off
the Northeast coast as the medium range forecast starts on
Thursday. In its wake, larger scale mean troughing should prevail
over eastern North America (led by a shortwave diving into the
Upper Great Lakes from Canada, possibly followed by a weaker
shortwave by Sunday-Monday) while a persistent upper ridge just
inland from the West Coast gradually retrogrades offshore. Despite
the somewhat amplified pattern, expect relatively quiet weather
conditions across most of the CONUS into the start of next week.
Exceptions will include some Southwest rainfall in response to
monsoonal moisture and a weak upper low settling just south of the
region, and a potent central/eastern U.S. cold front producing
some rain especially in the Great Lakes region along with
considerably cooler temperatures after its passage. The western
U.S./eastern Pacific upper ridge will support very warm
temperatures through the period.

...Guidance Evaluation/Predictability Assessment...

Latest models and ensembles maintain agreement for the general
pattern consisting of the western U.S. ridge retrograding into the
eastern Pacific as initial weak energy settles over parts of the
West, the mean trough prevailing over the eastern two-thirds of
the lower 48, and a weak Arizona/New Mexico upper low settling
over northern Gulf of California for a time before opening up by
Sunday or Monday.

Embedded details are more uncertain though. Models develop 12-24
hours or so of timing spread for the system affecting the
northeastern U.S. and southeastern Canada late this week into the
weekend. The 00Z ECMWF was fastest while the 00Z/06Z GFS were
slowest. Latest UKMET runs lean much closer to the slow side while
the 12Z CMC has trended somewhat faster than its 00Z run (now
closer to the ECMWF) and 12Z GFS accelerated to a compromise. Thus
it will take additional time to determine any conclusive trends.
Behind this system, 00Z through 12Z runs are showing an increasing
signal for another shortwave (possibly closed per the 12Z
UKMET/CMC) reaching the far northern tier by early day 6 Sunday.
This feature originates from around southern Alaska/northwestern
Canada on Sunday. There is enough agreement on its existence but
favor a conservative open wave depiction at this time since models
are inconsistent in its evolution. A blended approach looks good
for the weak energy dropping into the West (00Z CMC was extreme
with forming a closed low). Finally, current spread/run-to-run
variability suggest an intermediate solution for how late-period
Gulf of Alaska into Canada energy may break down the northern part
of the mean ridge. Based on guidance through 06Z, the updated
forecast started with an operational model composite for the first
half of the period and then trended to a half models/half ensemble
means blend by day 7 Monday. The primary continuity change was
introduction of the Sunday-Monday northern tier wave/frontal
system. QPF adjusted the 13Z National Blend of Models to reflect a
wider footprint for light amounts (mostly in the Great
Lakes/Northeast and southwestern U.S.) given the typically low
bias for light precipitation in the NBM.

...Weather/Hazards Highlights...

The combination of persistent monsoonal moisture and an upper low
settling over the northern Gulf of California will produce diurnal
showers and thunderstorms over parts of the Southwest/southern
Rockies, with locally heavy rainfall possible in some spots.
Intensity and coverage may vary from day to day, with some
eastward expansion of rainfall possible by early next week as the
upper low opens up. To the north, a cold front shifting across the
Midwest and Great Lakes may bring some light rain mainly around
Thursday, and then lake enhanced showers in the westerly flow
behind the front Friday and perhaps Saturday.

Temperatures out West will be warm into early next week underneath
a blocky upper ridge, with daytime highs over the Northwest 10 to
15 degrees or so above normal. Despite the anomalies, the
resulting temperatures peaking in the 70s and 80s (90s for parts
of California) are unlikely to create any heat related hazards.
Conversely, Canadian high pressure spilling into the north-central
U.S. and expanding eastward behind the cold front will result in
much below normal temperatures shifting from the northern Plains
into the Midwest and into much of the East Thursday-Monday.
Daytime highs in some locations could be 15 to 20 degrees below
average (mainly Thursday-Saturday) while overnight temperatures
are forecast to drop into the 30s for many locations from the
northern half of the Plains into central Appalachians, and even
20s for North Dakota and northern Minnesota particularly Friday
morning.

Rausch/Santorelli


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:
- Flooding occurring or imminent across portions of the Southeast.
- High winds across portions of the Great Lakes and the Upper
Mississippi Valley, Thu-Fri, Oct
6-Oct 7.
- Much below normal temperatures across portions of the Central
Plains, the Central Appalachians,
the Northern Plains, the Middle Mississippi Valley, the Southern
Appalachians, the Upper
Mississippi Valley, the Great Lakes, and the Ohio Valley, Sat-Sun,
Oct 8-Oct 9.

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