Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
355 AM EDT Sat Apr 01 2023

Valid 12Z Sat Apr 01 2023 - 12Z Mon Apr 03 2023

...Strong winds and severe thunderstorms possible across the Ohio Valley,
Northeast, and Mid-Atlantic today...

...Heavy snow to diminish across the Upper Midwest and Great Lakes this
morning before the next winter storm begins to develop over the central
High Plains Monday night...

...Heavy mountain snow continues across the Pacific Northwest...

...Critical Fire Weather persists over parts of the Central/Southern
Plains for the next several days...

An elongated and strong area of low pressure over the Great Lakes this
morning, combined with both a leading and secondary cold front extending
to the south-southwest, will produce a large area of potentially damaging
wind gusts from the Ohio Valley to the Mid-Atlantic through tonight.
Maximum wind gusts could approach 60 mph throughout much of the
Appalachians, upper Ohio Valley, and Mid-Atlantic today. Winds of this
magnitude are likely to blow down numerous trees and potentially lead to
widespread power outages. High Wind Warnings and Wind Advisories are in
effect. Additionally, severe thunderstorms are possible this afternoon and
evening as the secondary cold front and newly developing low pressure
system swing into the Interior Northeast. Warming temperatures this
afternoon are expected to help lead to an environment conducive for severe
thunderstorm development along the secondary cold front as it pushes from
the Ohio Valley to the Northeast, with storms capable of containing
damaging wind gusts, large hail, and a few tornadoes. A few severe
thunderstorms are also possible further to the south as the aforementioned
cold front reaches the Southeast today. On the cold side of this system,
heavy snow and gusty winds are expected to come to an end across the Upper
Midwest and Great Lakes this morning as the area of low pressure quickly
slides east.

The next major winter storm (not an April Fools' joke) is set to begin
forming across the central Great Basin and Rockies on Monday before
eventually swinging into the central/northern High Plains on Monday night.
A deep upper-level low diving into the West will be responsible for the
potential widespread area of heavy snow, as well as the likelihood of
strong winds. The greatest potential for over 8 inches of snow through
early Tuesday is forecast to stretch from the mountainous terrain of Utah
to southeast Wyoming, western South Dakota, and northwest Nebraska. The
combination of heavy snowfall rates and gusty winds in these regions are
likely to make travel very dangerous. Strong southwesterly winds across
the Southwest are also likely to lead to travel impacts on Monday,
especially for high profile vehicles, as wind gusts potentially exceed 60
mph.

For the Pacific Northwest, continued onshore flow underneath the
deep-upper level trough is expected to produce very heavy snow across much
of the Cascades through early next week. Total snowfall amounts are likely
to approach 3 to 4 feet, with slightly lesser amounts further inland
across the northern Rockies.

Unsettled and warm weather is forecast throughout much of the
south-central U.S. and Deep South to kick off the month of April. A warm
front lifting into the southern Plains and Lower Mississippi Valley on
Sunday will combine with an approaching shortwave trough to produce
numerous showers and thunderstorms Sunday night. A few storms could
contain intense rainfall rates between northeast Texas and central
Mississippi, leading to potential flash flooding concerns. Otherwise, well
above average temperatures are also set to build into the region by Monday
and include widespread highs into the 90s and upper 80s across the Lone
Star State. The warm temperatures combined with gusty winds and low
relative humidity will contribute to produce Critical Fire Weather
conditions throughout the central/southern High Plains.

Snell


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sat Apr 01 2023

Valid 12Z Tue Apr 04 2023 - 12Z Sat Apr 08 2023

...Blizzard threat across the northern Plains and Upper Midwest
into Tuesday/Wednesday...
...Heavy rainfall and severe thunderstorms from the South into the
Midwest Tuesday, lingering rest of the week over the South...
...Winter cold for the West and North-central U.S. next week to
starkly contrast summer heat that shifts east from the South to
the East/Southeast next week...

...Synoptic Overview...

Energetic closed upper trough ejection out from thr West/Rockies
will foster deep storm genesis and track from the central Plains
to the Upper Midwest Tuesday into Wednesday. Winter cold, heavy
snow and high winds to the north of the track of the powerful low
presure system offer a threat for blizzard conditions. This is in
stark contrast to widespread convective warm sector
showers/thunderstorms to develop and spread across the eastern
half of the country that includes a threat for severe weather with
a Mid-South focus Tuesday as per the Storm Prediction Center
(SPC). Upper ridging over the Gulf Coast should build northward
over the eastern U.S. and support anomalous warmth ahead of the
storm's associated cold front. This pattern may lead to the
stalling of the trailing front into later next week across the
U.S. southern tier. Frontal wave enhancements with the ejection of
southern stream upper energies may focus convergence/convection
and potential training/flash flooding issues, especially with the
front aligned with the upper flow across the moist and unstable
lower Mississippi Valley in the favorable right entrance region of
the upper jet. Accordingly, the experiental WPC medium range
Excessive Rainfall Outlook (ERO) plans to introduce a "Slight
Risk" threat area by next midweek.

...Model Guidance/Predictability Assessment...

Confidence remains above normal for the main weather threats next
week. Forecast clustering is best Tuesday-Thursday with the 18 UTC
GFS and 12 UTC ECMWF/UKMET and a composite blend seems to provide
a good forecast basis that is well supported by ensembles.
Forecast spread slowly increases heading into next weekend,
particularly with the placement and strength of reinforcing trough
energies chaotically into/out from the West. This lends a gradual
transition to a preference for the more run to run consistent
GEFS/ECENS ensemble means along with the 01 UTC National Blend of
Models (NBM). WPC product continuity is well maintained in this
manner and the latest 00 UTC models and ensembles are in line
overall.

...Weather/Hazards Highlights...

The big headline is the deepening Plains low that tracks from the
central Plains through the Upper Midwest Tuesday/Wednesday.
Probabilities for heavy snow have steadily increased from the
north-central Plains through the northern Plains and Upper
Midwest. This storm will also produce strong winds so blizzard
conditions are likely. Other areas farther east may see brisk to
strong winds even if to a less extreme degree. There is also
another substantial threat of strong to severe storms in the
expansive warm sector, with the Storm Prediction Center
highlighting and area over the Mid-South on Tuesday. Numerous
showers and thunderstorms are likely from the Gulf Coast to the
Midwest Tuesday, continuing next week over the South as
reinforcing southern stream trough energies suggest a continued
advection of copious Gulf moisture and instability, especially
with a wavy/stalling front.

A pronounced temperature contrast will persists across the nation
early-mid week with well below average readings spreading across
much of the western U.S. and central/northern Plains, and well
above average temperatures expanding from the southern Plains/Gulf
Coast through much of the eastern U.S. Tuesday-Wednesday look to
be the coldest days versus normal over the West/Plains with some
areas seeing highs as much as 20-30F below normal. The reverse
will hold true over the southern Plains early in the week and
farther eastward thereafter, with highs generally 10-20F above
normal and lows 15-25F above normal. Daily records mainly for cold
highs will be possible over the West during the first half of the
week. Farther east in the warm sector, Tuesday-Thursday will offer
the best potential for some daily records, with warm lows tending
to be more numerous than record highs until the cold frontal
passage.

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

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
319 AM EDT Sat Apr 01 2023

Valid 00Z Sun Apr 02 2023 - 00Z Sun Apr 09 2023

The closed upper low associated with an deep surface low off to
the northwest of Hawaii has finally begun to slowly lift north and
away from the northwestern Islands. The majority of the showers
and thunderstorms associated with a trailing front may linger into
the weekend over the western islands within a plume of deeper
moisture. The central and eastern Islands will continue to be on
the southwestern periphery of the subtropical high through most of
the forecast period, and as the low lifts north well away from the
state, the high then builds back westward centered near 35 degrees
north. Accordingly, trades should then become more easterly going
into early next week as the ridge axis builds in to the north, and
there will likely be in increase in showers over most of the
Islands as a weak upper trough works into and lingers over the
region next week that may act to pool moisture and instability.
Prefer a composite of reasonably well clustered model guidance for
a pattern that seems to have good ensemble support.

Schichtel

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1156 AM EDT Sat Apr 01 2023

Day 1
Valid 16Z Sat Apr 01 2023 - 12Z Sun Apr 02 2023

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

Locally heavy rainfall remains probable across portions of AL/GA
into the FL panhandle. However amounts exceeding flash flood
guidance appear unlikely, and thus we opted to remove the Marginal
risk with this update.

A line of strong to severe thunderstorms is expected to move
across portions of PA/NY this afternoon. While these storms will
produce briefly heavy rain, the quick movement of the cells should
generally prevent a flood threat. There is some chance we could
see localized urban high water across portions of eastern PA
towards NYC as storms enter a slightly more unstable environment
with higher lower level dewpoints. However, even here storms will
be moving so quick that the flood risk should be low. The overall
environment certainly favors severe weather as the main impact
with this activity, and thus while the urban minor flood threat is
non-zero, we will continue to go with no areas in the ERO.

Chenard

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
323 AM EDT Sat Apr 01 2023

Day 2
Valid 12Z Sun Apr 02 2023 - 12Z Mon Apr 03 2023

A southern stream shortwave interacting with a Gulf Coast warm
front along with sufficient moisture/instability is expected to
produce locally heavy rainfall from eastern Texas into the Lower
Mississippi Valley. Its general progression should keep amounts
from becoming particularly extreme. Some low- to mid-level
frontogenesis tracking roughly between the ArkLaTex, near the
AR/LA border, and through the ArkLaMiss into MS, but even amongst
the GFS and NAM guidance the axis of such is different. As the
placement remains a question mark due to the north-south spread in
the guidance, with the 00z Canadian Regional unusually on the
southern side and the 00z NAM remaining up north. The ECMWF has
been steadily shifting northward. Instability and low-level
inflow/effective bulk shear should be sufficient for convective
organization. Hourly rain totals up to 2" with local amounts in
the 2-4" range are expected in this region. A couple narrow
swaths of 1-2" of rainfall fell Friday into Friday Night across
southern AR and from northeast TX across northern LA and should
have saturated soils to some degree. The Slight Risk remains in
place and like the QPF splits the difference in the guidance.

Roth

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
323 AM EDT Sat Apr 01 2023

Day 3
Valid 12Z Mon Apr 03 2023 - 12Z Tue Apr 04 2023

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL IN AND AROUND
SOUTHERN AL & THE FLORIDA PANHANDLE...

While there are differences amongst the guidance mass fields,
there is a general signal for a moisture plume with precipitable
water values at or above 1.5" to become stuck vaguely near the FL
border with AL and GA. Instability, low-level inflow, and
effective bulk shear appear sufficient for convective
organization. The flow should be fairly unidirectional with
height from the west-southwest, leading to concerns for cell
training. With low-level inflow slightly convergent, cell mergers
can't be ruled out either. The low- to mid-level frontogenesis
seen on Sunday should be exiting to the east and northeast. The
guidance spread in amounts is fairly wide, with the 00z NAM the
driest and the 00z ECMWF the wettest, showing local amounts of 5".
Soil moisture across portions of southern AL and the FL Panhandle
and Big Bend is elevated, and rainfall during the day Saturday
(and possibly Sunday) could lead to further saturation. The model
guidance has a general signal for 1-3" in this area, which could
fall as quickly as an hour or two. Considering the above, a
Marginal Risk area was added for this region.

Roth

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
415 AM EDT Sat Apr 01 2023

Valid 12Z Sat Apr 01 2023 - 12Z Tue Apr 04 2023

...Northern Great Lakes...
Day 1...

The storm system responsible for the heavy snow and blizzard
conditions Friday and into Friday night will quickly track east
throughout the rest of the morning. The heaviest snowfall will
reside beneath the TROWAL tracking from northern WI to the U.P. of
MI. The latter of which will also have the benefit of some modest
lake enhancement. Snowfall rates of 2-3"/hr are expected beneath
this band with the eastern portions of the U.P. seeing the longest
duration of heavy snowfall. The forecast calls for another 6-12"
of snow in the eastern U.P. with a few inches also possible in the
central U.P. and far northern mainland MI. Strong wind gusts will
continue during the periods of heavy snow and on the backside of
the storm once snow diminishes in the afternoon. The heavy/wet
consistency of the snow weighing down tree branches and power
lines, along with the 40-50 mph wind gusts themselves, could
result in blowing snow and power outages. Updated Key Messages for
this system are below.

...Pacific Northwest to the northern High Plains...
Days 1-3...

...A major winter storm will produce heavy snow and strong winds
from the central Rockies to the northern High Plains early next
week...

The Pacific Northwest will be under siege from a strong and
persistent northeast Pacific jet stream that will introduce not
one but two different upper level disturbances to the region, as
well as into the northern Rockies. The left exit region associated
with this 250mb jet streak will remain positioned over the Pacific
Northwest and northern Rockies Saturday and into early Sunday,
which combined with ample Pacific moisture and strong upslope
enhancement into some mountain ranges, will result in heavy
snowfall. The second and more intense upper level feature arrives
Sunday morning as an amplifying upper low dives south into the
Pacific Northwest. Snow levels will drop below 1,000 feet in some
cases, while at the same time pushing the conveyor belt of Pacific
moisture south into northern California, the northern Great Basin,
and into the Wasatch and western WY mountain ranges. The heaviest
snowfall is set to occur along the Cascade Range of WA and OR
where snowfall will be measured in feet; anywhere from 1-4 feet is
expected with locally higher amounts possible in the tallest
peaks. Farther east, the northern Rockies mountain ranges which
include the Bitterroots, Boise, Sawtooth, and the Lewis Range can
also expect anywhere between 1-2 feet (locally higher).

Snow really begins to ramp up in the Wasatch, Tetons, Wind River,
and other central Rockies ranges of WY late Sunday night and into
Monday morning. It is during this time that the amplifying upper
trough produce strong PVA over the central Rockies while vertical
ascent atop the atmosphere increases while located beneath the
diffluent right-entrance region of a jet streak strengthening over
the northern High Plains. In addition, frontogenesis in the
700-500mb layer will support banded precipitation from these
aforementioned mountain ranges into eastern WY. By Monday
afternoon, an organizing and deepening 700mb low will form over
eastern UT and make its way northeast into southern WY. As ESE
winds in the 850-700mb layer pick up, it will introduce a large
quantity of moisture into the northern High Plains and wrap around
the northern periphery of the 700mb low. Meanwhile, temperatures
will be plenty cold enough to support snow, aided by the arrival
of a cold Canadian air-mass from the north. Heavy snow then looks
to engulf much of WY on east into western NE and western SD on the
northern periphery of a sub 990mb low in lee of the Rockies in
eastern CO late Monday and into Tuesday.

The pressure gradient will be impressive with the development of a
sub 990mb low in the central High Plains and a dome of 1030mb+
high pressure over southern Canada. The strong easterly component
in the central High Plains will cause strong upslope flow into the
front range of the Rockies, as well as 40-50 mph wind gusts by
Tuesday morning. With all the ingredients in place, this has all
the makings of a classic late season major winter storm in
portions of the central Rockies and High Plains. The question
marks involving this set up revolve around storm track and storm
motion. The slower the storm, the more time there is for heavier
snowfall accumulations, and vice versa for a faster storm. Latest
experimental PWSSI shows an expansive areas of 60-70% Moderate
impacts late Monday and into Tuesday from the Wasatch and Uinta
mountains to central and eastern WY. In fact, there are 60%
probabilities or Major impacts in portions of eastern WY,
southwest SD, and western NE late Monday into Tuesday. While there
is still some lingering uncertainty regarding the track, there is
increasing confidence in a high impact winter storm unfolding
beginning Sunday night and lasting into the first half of next
week. Key Messages are below.

The probability of significant icing Days 1-3 is less than 5%.


...Key Messages for Mar 30 - Apr 1 Winter Storm...

-Intense snow rates (1-2â€/hr, locally higher) combined with
strong winds may cause extensive tree damage and power outages
through Saturday morning across the Upper Midwest and into the
northern Great Lakes.

-Hazardous travel conditions due to a combination of snow covered
roads and whiteout conditions are expected.

-Periods of snow will taper off Saturday afternoon with gusty
winds potentially still capable of causing blowing snow and
possible power outages.

...Key Messages for Apr 3-5 Blizzard...

-A powerful storm will track across the Intermountain West and
central Rockies early next week before moving through the High
Plains and Upper Midwest mid next week.

-Confidence is increasing in a multi-hazard storm with significant
snow accumulations and strong winds. The combination of heavy
snowfall and strong winds could result in blizzard conditions
across portions of the central Rockies and the Plains.

-Widespread hazardous travel conditions and disruptions are
expected, including snow covered roads and reduced visibility,
particularly from Monday through Wednesday.

-In the wake of the storm, much below normal temperatures and wind
chill values near or below zero are likely, creating a dangerous
situation for those who may become stranded due to the heavy snow
and strong winds.


Mullinax

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sat Apr 01 2023

Valid 12Z Tue Apr 04 2023 - 12Z Sat Apr 08 2023

...Blizzard threat across the northern Plains and Upper Midwest
into Tuesday/Wednesday...
...Heavy rainfall and severe thunderstorms from the South into the
Midwest Tuesday, lingering rest of the week over the South...
...Winter cold for the West and North-central U.S. next week to
starkly contrast summer heat that shifts east from the South to
the East/Southeast next week...

...Synoptic Overview...

Energetic closed upper trough ejection out from thr West/Rockies
will foster deep storm genesis and track from the central Plains
to the Upper Midwest Tuesday into Wednesday. Winter cold, heavy
snow and high winds to the north of the track of the powerful low
presure system offer a threat for blizzard conditions. This is in
stark contrast to widespread convective warm sector
showers/thunderstorms to develop and spread across the eastern
half of the country that includes a threat for severe weather with
a Mid-South focus Tuesday as per the Storm Prediction Center
(SPC). Upper ridging over the Gulf Coast should build northward
over the eastern U.S. and support anomalous warmth ahead of the
storm's associated cold front. This pattern may lead to the
stalling of the trailing front into later next week across the
U.S. southern tier. Frontal wave enhancements with the ejection of
southern stream upper energies may focus convergence/convection
and potential training/flash flooding issues, especially with the
front aligned with the upper flow across the moist and unstable
lower Mississippi Valley in the favorable right entrance region of
the upper jet. Accordingly, the experiental WPC medium range
Excessive Rainfall Outlook (ERO) plans to introduce a "Slight
Risk" threat area by next midweek.

...Model Guidance/Predictability Assessment...

Confidence remains above normal for the main weather threats next
week. Forecast clustering is best Tuesday-Thursday with the 18 UTC
GFS and 12 UTC ECMWF/UKMET and a composite blend seems to provide
a good forecast basis that is well supported by ensembles.
Forecast spread slowly increases heading into next weekend,
particularly with the placement and strength of reinforcing trough
energies chaotically into/out from the West. This lends a gradual
transition to a preference for the more run to run consistent
GEFS/ECENS ensemble means along with the 01 UTC National Blend of
Models (NBM). WPC product continuity is well maintained in this
manner and the latest 00 UTC models and ensembles are in line
overall.

...Weather/Hazards Highlights...

The big headline is the deepening Plains low that tracks from the
central Plains through the Upper Midwest Tuesday/Wednesday.
Probabilities for heavy snow have steadily increased from the
north-central Plains through the northern Plains and Upper
Midwest. This storm will also produce strong winds so blizzard
conditions are likely. Other areas farther east may see brisk to
strong winds even if to a less extreme degree. There is also
another substantial threat of strong to severe storms in the
expansive warm sector, with the Storm Prediction Center
highlighting and area over the Mid-South on Tuesday. Numerous
showers and thunderstorms are likely from the Gulf Coast to the
Midwest Tuesday, continuing next week over the South as
reinforcing southern stream trough energies suggest a continued
advection of copious Gulf moisture and instability, especially
with a wavy/stalling front.

A pronounced temperature contrast will persists across the nation
early-mid week with well below average readings spreading across
much of the western U.S. and central/northern Plains, and well
above average temperatures expanding from the southern Plains/Gulf
Coast through much of the eastern U.S. Tuesday-Wednesday look to
be the coldest days versus normal over the West/Plains with some
areas seeing highs as much as 20-30F below normal. The reverse
will hold true over the southern Plains early in the week and
farther eastward thereafter, with highs generally 10-20F above
normal and lows 15-25F above normal. Daily records mainly for cold
highs will be possible over the West during the first half of the
week. Farther east in the warm sector, Tuesday-Thursday will offer
the best potential for some daily records, with warm lows tending
to be more numerous than record highs until the cold frontal
passage.

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

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