Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
336 AM EDT Sat Apr 19 2025

Valid 12Z Sat Apr 19 2025 - 12Z Mon Apr 21 2025

...Moderate to heavy snow over parts of the Central/Southern Rockies on
Saturday...

...There is a Moderate Risk of excessive rainfall over parts of the Middle
Mississippi Valley to the Southern Plains on Saturday...

...There is a Slight Risk of severe thunderstorms over parts of the
Middle/Lower Mississippi Valley and the Southern Plains on Saturday and an
Enhanced Risk of severe thunderstorms over parts of the Middle/Lower
Mississippi Valley on Sunday...

A front extending from the Great Lakes/Ohio Valley and then across the
Middle/Lower Mississippi Valley into the Southern Plains will move
eastward off the Northeast Coast and from the Mid-Atlantic to the Southern
Plains by Sunday morning. On Saturday, the system will produce showers and
thunderstorms from parts of the Northeast to the Southern Plains and
severe thunderstorms from the Middle/Lower Mississippi Valley to the
Southern Plains. Therefore, the SPC has issued a Slight Risk (level 2/5)
of severe thunderstorms over parts of the Middle/Lower Mississippi Valley
to the Southern Plains through Sunday morning. The hazards associated
with these thunderstorms are frequent lightning, severe thunderstorm wind
gusts, hail, and a few tornadoes. Furthermore, there is an added threat of
hail, two inches or greater, over the Southern Plains.

In addition, the showers and thunderstorms will produce heavy rain over
parts of the Middle Mississippi Valley and the Southern Plains on
Saturday. Therefore, the WPC has issued a Moderate Risk (level 3/4) of
excessive rainfall over parts of the Middle Mississippi Valley into the
Southern Plains through Sunday morning. Numerous flash flooding events are
possible and many streams may flood, potentially affecting larger rivers.

Further, an upper-level low associated with the western end of the front
will produce moderate to heavy snow over parts of the Central/Southern
Rockies. Rain will also develop over the lower elevations of the Southwest
and Central High Plains. The snow will end over the region by Sunday
morning.

On Sunday, a wave of low pressure along the boundary moves northward from
the Southern Plains to the Upper Mississippi Valley by Monday morning.
The front will produce showers and severe thunderstorms over parts of the
Middle/Lower Mississippi Valley. Therefore, the SPC has issued an Enhanced
Risk (level 3/5) of severe thunderstorms over the Middle/Lower Mississippi
Valley from Sunday into Monday morning. The hazards associated with these
thunderstorms are frequent lightning, severe thunderstorm wind gusts,
hail, and a few tornadoes.

In addition, the threat of excessive rainfall will decrease on Sunday over
parts of the Middle/Lower Mississippi Valley to a Marginal Risk. Moreover,
showers and thunderstorms will expand into the Great Lakes/ Ohio Valley.
Furthermore, an area of wet snow will develop near Lake Superior on Monday
morning.

Meanwhile, on Saturday, a front over the Pacific Northwest will move
eastward to the Northern High Plains to the Northern Intermountain
Region/Great Basin and dissipate by Sunday morning. The system will
produce light rain over parts of the Northwest, moving into the Northern
Intermountain Region by Saturday evening. By Sunday morning, additional
light rain will move into the Pacific Northwest. As the associated energy
moves eastward, rain and highest elevation snow will develop over parts of
the Northern Intermountain Region and Northern Rockies overnight Sunday.


Ziegenfelder


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 19 2025

Valid 12Z Tue Apr 22 2025 - 12Z Sat Apr 26 2025


...Heavy rain threat for the South-Central U.S. next week...


...Guidance/Predictability Assessment...

Tonight's WPC medium range 500mb and surface progs were mainly
derived from a composite of best clustered mass field and QPF
guidance of the 12 UTC ECMWF/UKMET/Canadian models valid Tuesday
into Wednesday. Switched to best compatible 12 UTC ECMWF/NAEFS
ensemble means and the 12 UTC ECMWF model for better details for
the remainder of next week amid growing forecast spread, but still
with seemingly near normal predictability beyond local convective
foci. In addition to smaller scale embedded system differences,
this solution in particular offers stronger than concensus upper
trough amplification and wavy surface system support from the
eastern Pacific through the West Coast heading Friday into next
weekend. This is strongly supported by machine learning guidance.

...Weather/Hazards Highlights...

A protracted series of generally progressive upper features and
associated surface based systems are set to work over the lower 48
next week in multiple stream flows to locally focus April weather,
but there is a growing signal to amplify the flow from the eastern
Pacific into the West heading into and through next weekend.

A WPC Excessive Rainfall Marginal Risk area for portions of the
Southern Plains for Day 4/Tuesday and Day 5/Wednesday have been
introduced given the potential for repeat/training of cells during
the day and with overnight activity with emerging moist and
unstable return flow into and over several frontal boundaries.
Portions of this area are also forecast to have enhanced rainfall
this weekend that would lead to wet soil conditions. Heavy rain and
runoff threats along with strong convective potential in this
region and into the Mississippi Valley will also be monitored for
mid-later next week given lingering support and multi-day
potential, albeit with greater uncertainty on the details.

An expectation for upper trough amplification, wavy surface system
genesis and slow translation from the eastern Pacific to the West
Coast Friday into next weekend has the potential to offer increased
moderate rain chances with unsettled/cooling weather conditions.

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 forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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
https://www.wpc.ncep.noaa.gov/#page=ovw

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
317 AM EDT Sat Apr 19 2025

Valid 00Z Sun 20 Apr 2025 - 00Z Sun 27 Apr 2025

Models and ensembles again seem reasonably well clustered,
bolstering forecast confidence in a favored composite solution
that again should tend to mitigate lingering smaller scale
variances consistent with individual predictability. An upper
trough lingering atop Hawaii will slowly lose influence today
along with trade disrupting inverted troughing. Winter weather
advisories for the Big Island summits linger in the short term.
For the weekend, the upper trough is forecast to further weaken
and slowly shift away to the east, while Pacific surface high
pressure develops/bridges well to the north of the state and allow
trades to gradually increase. Expect a generally wet trade
pattern through early next week as fueled by lingering moisture.
Then from around the middle to later next week, another upper
trough and possible closed low is forecast to dig just to the west
of the state. This will once again cause the mean flow to veer
for southeasterly/southerly winds that may be stronger this round
so there is potential for moisture and showers to again increase.

Schichtel

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
354 AM EDT Sat Apr 19 2025
Day 1
Valid 12Z Sat Apr 19 2025 - 12Z Sun Apr 20 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM NORTH-
CENTRAL TEXAS THROUGH MUCH OF SOUTHERN MISSOURI...

A narrow corridor of 4 to 6+ inches of rainfall likely today
across southern Missouri to North-central Texas as thunderstorms
train and backbuild along a slow moving/stalled frontal boundary.
There has been a consistent and persistent westward trend of the
placement of the heaviest rainfall both in the model runs and the
deterministic WPC QPF. Once again the risk areas were expanded
south and west. The Moderate Risk spans from north-central Texas to
the Missouri Ozarks; which had a minor reduction in coverage out of
Illinois given the decrease in QPF from the Mid-Mississippi Valley
to Ohio. The Slight Risk was also reduced over parts of Illinois
and Indiana while extended further into central Texas. The Marginal
was trimmed southward across Illinois, Indiana and Ohio while
adjusted westward of west-central Texas.

On the north side the cold, dry northeasterly flow will be
weakening while in the warm sector there will be an ever increasing
supply of hot and humid air straight out of the Gulf being
advected northward on up to 50 kt winds across Texas and into the
frontal interface from north Texas through Oklahoma and Missouri.
An upper low ejecting from the mountains into this hot, moist
airmass will lead to robust cyclogenesis over Oklahoma by Sunday
morning.

Campbell


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
354 AM EDT Sat Apr 19 2025
Day 1
Valid 12Z Sat Apr 19 2025 - 12Z Sun Apr 20 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM NORTH-
CENTRAL TEXAS THROUGH MUCH OF SOUTHERN MISSOURI...

A narrow corridor of 4 to 6+ inches of rainfall likely today
across southern Missouri to North-central Texas as thunderstorms
train and backbuild along a slow moving/stalled frontal boundary.
There has been a consistent and persistent westward trend of the
placement of the heaviest rainfall both in the model runs and the
deterministic WPC QPF. Once again the risk areas were expanded
south and west. The Moderate Risk spans from north-central Texas to
the Missouri Ozarks; which had a minor reduction in coverage out of
Illinois given the decrease in QPF from the Mid-Mississippi Valley
to Ohio. The Slight Risk was also reduced over parts of Illinois
and Indiana while extended further into central Texas. The Marginal
was trimmed southward across Illinois, Indiana and Ohio while
adjusted westward of west-central Texas.

On the north side the cold, dry northeasterly flow will be
weakening while in the warm sector there will be an ever increasing
supply of hot and humid air straight out of the Gulf being
advected northward on up to 50 kt winds across Texas and into the
frontal interface from north Texas through Oklahoma and Missouri.
An upper low ejecting from the mountains into this hot, moist
airmass will lead to robust cyclogenesis over Oklahoma by Sunday
morning.

Campbell


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
354 AM EDT Sat Apr 19 2025
Day 2
Valid 12Z Sun Apr 20 2025 - 12Z Mon Apr 21 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL
PLAINS AND PORTIONS OF THE MIDDLE AND LOWER MISSISSIPPI VALLEY...

The system responsible for the scattered to widespread
heavy/excessive rainfall on Saturday will begin to accelerate to
the northeast as the upper trough begins to fill. Rainfall amounts
should not rival amounts that are expected on Saturday, but
additional rainfall on top recently flooded areas remains a
potential concern. General model consensus shows a broad footprint
of up to 1.25 inches with isolated maximums of 1.5 to 2+ inches
anywhere from eastern Nebraska to southern Minnesota and Wisconsin.
The exact location of the heaviest amounts has the greatest
uncertainty.

A Marginal Risk is in place for the Middle and Lower
Mississippi Valley and eastern portions of the Central Plains.
These areas are north and west of the most sensitive areas of the
Mississippi/Ohio River Valleys where streamflows remain high after
recent flooding. However, some rain atop recently flooded areas,
and runoff from other areas into these rivers, could exacerbate
ongoing flooding issues in some areas, so continue to monitor.

Campbell/Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
354 AM EDT Sat Apr 19 2025
Day 3
Valid 12Z Mon Apr 21 2025 - 12Z Tue Apr 22 2025

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

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sat Apr 19 2025


A protracted series of generally progressive upper features and
associated surface based systems are set to work over the lower 48
next week in multiple stream flows to locally focus April weather,
but there is a growing signal to amplify the flow from the eastern
Pacific into the West heading into and through next weekend.

A WPC Excessive Rainfall Marginal Risk area for portions of the
Southern Plains for Day 4/Tuesday and Day 5/Wednesday have been
introduced given the potential for repeat/training of cells during
the day and with overnight activity with emerging moist and
unstable return flow into and over several frontal boundaries.
Portions of this area are also forecast to have enhanced rainfall
this weekend that would lead to wet soil conditions. Heavy rain and
runoff threats along with strong convective potential in this
region and into the Mississippi Valley will also be monitored for
mid-later next week given lingering support and multi-day
potential, albeit with greater uncertainty on the details.

An expectation for upper trough amplification, wavy surface system
genesis and slow translation from the eastern Pacific to the West
Coast Friday into next weekend has the potential to offer increased
moderate rain chances with unsettled/cooling weather conditions.

Schichtel

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sat Apr 19 2025


A protracted series of generally progressive upper features and
associated surface based systems are set to work over the lower 48
next week in multiple stream flows to locally focus April weather,
but there is a growing signal to amplify the flow from the eastern
Pacific into the West heading into and through next weekend.

A WPC Excessive Rainfall Marginal Risk area for portions of the
Southern Plains for Day 4/Tuesday and Day 5/Wednesday have been
introduced given the potential for repeat/training of cells during
the day and with overnight activity with emerging moist and
unstable return flow into and over several frontal boundaries.
Portions of this area are also forecast to have enhanced rainfall
this weekend that would lead to wet soil conditions. Heavy rain and
runoff threats along with strong convective potential in this
region and into the Mississippi Valley will also be monitored for
mid-later next week given lingering support and multi-day
potential, albeit with greater uncertainty on the details.

An expectation for upper trough amplification, wavy surface system
genesis and slow translation from the eastern Pacific to the West
Coast Friday into next weekend has the potential to offer increased
moderate rain chances with unsettled/cooling weather conditions.

Schichtel

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
210 AM EDT Sat Apr 19 2025

Valid 12Z Sat Apr 19 2025 - 12Z Tue Apr 22 2025


...Southern Rockies...
Day 1...

Significant mid-April winter storm continues for one additional day
across the Rockies of southern CO and northern NM.

As of early this morning, the amplified but positively tilted
trough is clearly evident on GOES-E WV and IR imagery, centered
across northern Arizona. This trough will continue to amplify, and
as the northern portion of this trough ejects to the east, the
southern portion will close off across the Four Corners. This
amplification will result in pronounced downstream synoptic lift,
as mid-level divergence intensifies and at least peripherally
overlaps with the LFQ of a poleward arcing jet streak into the
Central Plains. At the same time, the cold front being driven south
by the amplified trough will dig into Texas and reach the Rio
Grande Valley by this afternoon, leaving impressive 850-600mb fgen
in its wake tilted north into NM and CO. This even more enhanced
ascent will overlap with upslope flow on post-frontal E/NE winds,
to drive intense snow rates across the Sangre de Cristos and San
Juans through the first half of D1.

This deep layer ascent (and additional mesoscale dynamics through
fgen/upslope) will occur within a moistening column as 700-300mb
flow remains out of the SW downstream of the primary trough axis.
Although PWs progged by NAEFS will be around normal values, this
will be sufficient to be wrung out as heavy snow, with rates
possibly (30-60% chance) exceeding 1"/hr, especially in the
Sangres and San Juans. Snow levels will begin to slowly rise today
as the cold airmass once in place begins to modify, rising from
around 5,000 ft to 7,000 ft.

For the tail end of this event, the heaviest snow is likely across
the Sangre de Cristos and the San Juans, where WPC probabilities
D1 are high (>70%) for more than 8 inches of snow, and locally over
1 foot is possible despite rapidly waning coverage and intensity
of snow after 00Z Sunday.


...Washington Cascades & Northern Rockies...
Days 2-3...

Shortwave entering the Northwest Sunday evening and crossing over
the northern Rockies on Monday will be accompanied by favorable
upper jet dynamics, with the LFQ situated over the region.
Associated height falls will also be coincident with lowering snow
levels, starting out around 3,500 ft in the WA Cascades before
crashing to 2,500 ft briefly. For the northern Rockies, snow levels
around 6,000 ft will fall to around 4,000 ft in northwest MT and
5,000 ft near Yellowstone. The heaviest snowfall is expected across
the northern WA Cascades and parts of western MT into Yellowstone
Country, where 6-12 inches are possible in the higher peaks. WPC
probabilities are high (>70%) through D3 for at least 6 inches of
snow across parts of the WA Cascades and the western/south-central
MT ranges above 7,000 ft.


The probability of at least 0.10" of freezing rain across CONUS is
less than 10%.


Snell

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sat Apr 19 2025

Valid 12Z Tue Apr 22 2025 - 12Z Sat Apr 26 2025


...Heavy rain threat for the South-Central U.S. next week...


...Guidance/Predictability Assessment...

Tonight's WPC medium range 500mb and surface progs were mainly
derived from a composite of best clustered mass field and QPF
guidance of the 12 UTC ECMWF/UKMET/Canadian models valid Tuesday
into Wednesday. Switched to best compatible 12 UTC ECMWF/NAEFS
ensemble means and the 12 UTC ECMWF model for better details for
the remainder of next week amid growing forecast spread, but still
with seemingly near normal predictability beyond local convective
foci. In addition to smaller scale embedded system differences,
this solution in particular offers stronger than concensus upper
trough amplification and wavy surface system support from the
eastern Pacific through the West Coast heading Friday into next
weekend. This is strongly supported by machine learning guidance.

...Weather/Hazards Highlights...

A protracted series of generally progressive upper features and
associated surface based systems are set to work over the lower 48
next week in multiple stream flows to locally focus April weather,
but there is a growing signal to amplify the flow from the eastern
Pacific into the West heading into and through next weekend.

A WPC Excessive Rainfall Marginal Risk area for portions of the
Southern Plains for Day 4/Tuesday and Day 5/Wednesday have been
introduced given the potential for repeat/training of cells during
the day and with overnight activity with emerging moist and
unstable return flow into and over several frontal boundaries.
Portions of this area are also forecast to have enhanced rainfall
this weekend that would lead to wet soil conditions. Heavy rain and
runoff threats along with strong convective potential in this
region and into the Mississippi Valley will also be monitored for
mid-later next week given lingering support and multi-day
potential, albeit with greater uncertainty on the details.

An expectation for upper trough amplification, wavy surface system
genesis and slow translation from the eastern Pacific to the West
Coast Friday into next weekend has the potential to offer increased
moderate rain chances with unsettled/cooling weather conditions.

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 forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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
https://www.wpc.ncep.noaa.gov/#page=ovw