Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Fri May 30 2025

Valid 12Z Fri May 30 2025 - 12Z Sun Jun 01 2025

...A low pressure system will bring a round of moderate to heavy rain and
gusty winds from the Ohio Valley to the Mid-Atlantic states today then
across New England on Saturday...

...Severe thunderstorms possible later today for the Mid-Atlantic and the
Southeast...

...Heat risk expected to reach major level for interior California and
portions of the Southwest Friday and Saturday...

A low pressure system currently developing over the Midwest is forecast to
track across the northern Mid-Atlantic by tonight and intensify to a
rather strong system for late May as it reaches New England on Saturday.
A round of moderate to heavy rain along with increasingly gusty wind can
be expacted along the track of this low pressure system. The highest
chance of heavy rain will be across the Ohio Valley today and then into
the northern Mid-Atlantic by tonight. Some thunderstorms embedded within
the rain can be strong to severe, possibly resulting in local areas of
flash flooding. The low is forecast to deepen further as the center
tracks northeastward through New England on Saturday with a swath of
moderate to heavy rain across the interior sections, along with gusty wind
expanding across the Northeast. From the Mid-Atlantic southward into the
Southeast, lines of thunderstorms could contain severe weather as a cold
front associated with the intensifying system sweeps across the region
later today into tonight. The cold front will move off the East Coast
later tonight but the instability associated with a cold upper-level
trough could trigger scattered thunderstorms across the Mid-Atlantic
region even though temperatures will be cooler behind the cold front on
Saturday. By Saturday night into Sunday morning, a reinforcing cold front
will bring temperatures further down into the 40s and 50s from all of the
Great Lakes through the Northeast and down into the Mid-Atlantic.

Meanwhile, scattered thunderstorms associated with the trailing cold front
are expected across the Deep South today before pushing off the Gulf Coast
by tonight. In contrast to the rain and cooling trend in the eastern
U.S., a strong ridge of high pressure will bring heat and persistent dry
weather across the western U.S. and into the northern Plains. In fact,
record high temperatures will be threatened across interior northern
California today, expanding into the Great Basin, Idaho, and as far north
as western Montana on Saturday. The anticipated heat in the Southwest for
the next couple of days has led to the issuance of Extreme Heat Warnings
for the dangerous heat for portions of southernmost Nevada, southeast
California, and northwestern most Arizona. Drinking plenty of water,
wearing light colored clothing, and staying in air conditioned areas is
advised as temperatures soar as high as the mid 110s Fahrenheit in lower
desert locations like Death Valley, California. A cold front from the
Pacific is forecast to bring marked cooling into the Pacific Northwest
later on Saturday into Sunday but with minimal rainfall expected through
early on Sunday with the commencement of June.

Kong


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
249 AM EDT Fri May 30 2025

Valid 12Z Mon Jun 02 2025 - 12Z Fri Jun 06 2025


...Pattern Overview and Guidance/Predictability Assessment...

Through the duration of the extended period there will be an
amplified split flow pattern across the CONUS with below average
predictability. In general model consensus depicts troughs in the
West and East with potential to close off as the week progresses.
There has been persist run-to-run differences that impact the
location, strength and timing of fronts, weather conditions and
precipitation totals.

The preferred model blend for this cycle comprised of the 00Z
ECMWF/CMC/UKMET and the EC and GEFS ensemble means. The weighting
of means increased to 50% for the latter half of the forecast
period. As previously noted, the GFS continued to hang on to the
notion of lagging behind and being stronger shortwave/vort max
descending down the eastern flank of a Western U.S. ridge at the
start of the period.


...Weather/Hazards Highlights...

As an amplified upper trough tracks slowly off the East Coast a
series of shortwaves will dig through the flow; which may
potentially develop into a separated closed low. A wavy trailing
front will settle nearby from the western Atlantic southwestward to
the Gulf. While uncertain lows could act to bring some activity
from the coastal areas up the Eastern Seaboard Sunday and into next
week, particular runoff issues may develop with time for south
Florida urban areas given deeper lower latitude moisture
availability and support to monitor.

While differences on the details persist with time, the general
consensus favors upper trough amplification with multiple systems
into the West along with lead ejection of a southern stream closed
system from offshore Baja through the Southwest into the Rockies.
This pattern change will be a welcomed relief to recent heat across
the West as well as transitioning to a more unsettled and
increasingly wet flow pattern farther inland and downstream over
the Intermountain West and especially the Northern Rockies through
midweek. This will support the possibility for enhanced mountain
snow in the highest elevations of the Northern Rockies. Favorable
upper support, frontal translation, and anomalous moisture along
with downstream cycle-/frontogenesis over the Plains should also
act to enhance precipitation and an emerging convective pattern
from portions of the Northern Rockies to the Northern Plains by
the start of the new week. Maintained the broad Marginal Risk for
the Day 4 ERO from portions of Minnesota, the Dakotas, eastern
Wyoming and northeast Colorado. A broad Marginal Risk was
introduced for the day 5 period as the precipitation advances over
the central part of the country and encompasses the eastern
Dakotas, Minnesota, western Wisconsin, Iowa, eastern Nebraska,
Kansas, western missouri and northeast Oklahoma.


Campbell/Miller/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
412 AM EDT Fri May 30 2025

Valid 00Z Sat 31 May 2025 - 00Z Sat 07 Jun 2025

High pressure building to the north/northeast of the islands will
help trade winds rebound by the weekend. An upper trough will be
positioned northwest of the state this weekend into next week and
will keep a majority of the pooling moisture offshore however
should initiate a downstream response to veer lingering island
trades southeastward that may provide a protracted tap of shower
fueling moisture.


Campbell/Schichtel

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Fri May 30 2025
Day 1
Valid 12Z Fri May 30 2025 - 12Z Sat May 31 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER THE MID
ATLANTIC/OHIO VALLEY AND A PORTION OF ADJACENT NEW YORK STATE...

Maintained a Slight Risk area over portions of the Ohio Valley and
the Mid-Atlantic region as well as a portion of adjacent New York
state as low pressure forms and deepens/strengthens across the area
today in response to ample upper forcing. The resulting showers
and thunderstorms should be capable of producing heavy rainfall
along the immediate track of the surface low pressure center and in
the unstable airmass in the warm sector of the low later today and
tonight. The risk of flash flooding will be greatest where there
is overlap of the heavier rainfall and where soil has been made
prone to run off by recent heavy rainfall. With the convection
tracking from west to east...the portion of the Slight risk area in
Kentucky really focuses early today while the portion in northern
New Jersey is primarily focused during the overnight hours from
late tonight into very early Saturday morning.

Repeating rounds of heavy rain today interacting with the terrain
and full rivers should cause onset of flash flooding to occur
sooner to the start of the rainfall...making any potential
flooding more hazardous in West Virginia while flooding concerns
farther east will be based around urbanization. The storms will
also occur in the afternoon and evening, during the diurnal warmest
time of day, which will add more instability for the storms to
feed upon.

Bann

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Fri May 30 2025
Day 2
Valid 12Z Sat May 31 2025 - 12Z Sun Jun 01 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
NEW ENGLAND...

A surface low pressure system across the Mid Atlantic on Friday
will continue to strengthen as it makes its way to the northeast on
Saturday. Concern for heavy rains lingers across parts of New
England with the heaviest rainfall likely over Northern NH and ME,
especially within the northeastern flank of the low where the warm
conveyor belt advects deeper moisture poleward with weak buoyancy
likely remaining over the region into Saturday evening. Additional
rainfall amounts of 1 to 2 inches...with locally higher
amounts...remain in the forecast. That amount of rain could lead to localized
flash flooding given the complex terrain impacted and relatively
good dynamics at play.

Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Fri May 30 2025
Day 3
Valid 12Z Sun Jun 01 2025 - 12Z Mon Jun 02 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHWEST UNITED STATES...

Showers and thunderstorms will become more numerous over parts of
the Southwest US as a plume of moisture overspreads the region
from the south...with the anomalous moist airmass allowing some of
the storms to produce locally heavy rainfall and the risk of flash
flooding. Precipitable water values of an inch or greater should
already be in place across southwest Arizona and adjacent areas of
the California deserts at the start of the Day 3 period...90+
percentile values for this time of year...with moisture continuing
to stream into the region. With the flow aloft becoming
increasingly diffluent to the east of closed low off the California
coast at the same time that moisture continues to stream into the
region...storms should be in an environment conducive for heavy
rainfall and the potential for repeat convection/training storms
leading to the risk of flash flooding. One concern is the
increasing moisture may result in sufficient cloud cover to delay
or inhibit the convective initiation...but there is enough support
in the guidance to support a Marginal risk at this time frame.

Bann

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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
249 AM EDT Fri May 30 2025


As an amplified upper trough tracks slowly off the East Coast a
series of shortwaves will dig through the flow; which may
potentially develop into a separated closed low. A wavy trailing
front will settle nearby from the western Atlantic southwestward to
the Gulf. While uncertain lows could act to bring some activity
from the coastal areas up the Eastern Seaboard Sunday and into next
week, particular runoff issues may develop with time for south
Florida urban areas given deeper lower latitude moisture
availability and support to monitor.

While differences on the details persist with time, the general
consensus favors upper trough amplification with multiple systems
into the West along with lead ejection of a southern stream closed
system from offshore Baja through the Southwest into the Rockies.
This pattern change will be a welcomed relief to recent heat across
the West as well as transitioning to a more unsettled and
increasingly wet flow pattern farther inland and downstream over
the Intermountain West and especially the Northern Rockies through
midweek. This will support the possibility for enhanced mountain
snow in the highest elevations of the Northern Rockies. Favorable
upper support, frontal translation, and anomalous moisture along
with downstream cycle-/frontogenesis over the Plains should also
act to enhance precipitation and an emerging convective pattern
from portions of the Northern Rockies to the Northern Plains by
the start of the new week. Maintained the broad Marginal Risk for
the Day 4 ERO from portions of Minnesota, the Dakotas, eastern
Wyoming and northeast Colorado. A broad Marginal Risk was
introduced for the day 5 period as the precipitation advances over
the central part of the country and encompasses the eastern
Dakotas, Minnesota, western Wisconsin, Iowa, eastern Nebraska,
Kansas, western missouri and northeast Oklahoma.


Campbell/Miller/Schichtel

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
249 AM EDT Fri May 30 2025


As an amplified upper trough tracks slowly off the East Coast a
series of shortwaves will dig through the flow; which may
potentially develop into a separated closed low. A wavy trailing
front will settle nearby from the western Atlantic southwestward to
the Gulf. While uncertain lows could act to bring some activity
from the coastal areas up the Eastern Seaboard Sunday and into next
week, particular runoff issues may develop with time for south
Florida urban areas given deeper lower latitude moisture
availability and support to monitor.

While differences on the details persist with time, the general
consensus favors upper trough amplification with multiple systems
into the West along with lead ejection of a southern stream closed
system from offshore Baja through the Southwest into the Rockies.
This pattern change will be a welcomed relief to recent heat across
the West as well as transitioning to a more unsettled and
increasingly wet flow pattern farther inland and downstream over
the Intermountain West and especially the Northern Rockies through
midweek. This will support the possibility for enhanced mountain
snow in the highest elevations of the Northern Rockies. Favorable
upper support, frontal translation, and anomalous moisture along
with downstream cycle-/frontogenesis over the Plains should also
act to enhance precipitation and an emerging convective pattern
from portions of the Northern Rockies to the Northern Plains by
the start of the new week. Maintained the broad Marginal Risk for
the Day 4 ERO from portions of Minnesota, the Dakotas, eastern
Wyoming and northeast Colorado. A broad Marginal Risk was
introduced for the day 5 period as the precipitation advances over
the central part of the country and encompasses the eastern
Dakotas, Minnesota, western Wisconsin, Iowa, eastern Nebraska,
Kansas, western missouri and northeast Oklahoma.


Campbell/Miller/Schichtel

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
214 PM EDT Wed May 7 2025

Valid 00Z Thu May 08 2025 - 00Z Sun May 11 2025


...Colorado...
Day 1...

Lingering vorticity on the western side of the departing upper low
will still trigger some light snow over the San Juans this evening
before tapering off tonight/early Thursday. WPC probabilities for
at least an additional 4 inches of snow after 00Z are low (10-40%)
above 11,000ft.

For days 2-3, the probability of at least 4 inches of snow is less
than 10%.

The probability of significant freezing rain across the CONUS is
less than 10%.

Note - this is the last regularly scheduled discussion (QPFHSD)
for the 2024-2025 winter season. Unless a significant winter
weather threat emerges, this discussion will next be updated on or
about September 25, 2025.


Fracasso

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
249 AM EDT Fri May 30 2025

Valid 12Z Mon Jun 02 2025 - 12Z Fri Jun 06 2025


...Pattern Overview and Guidance/Predictability Assessment...

Through the duration of the extended period there will be an
amplified split flow pattern across the CONUS with below average
predictability. In general model consensus depicts troughs in the
West and East with potential to close off as the week progresses.
There has been persist run-to-run differences that impact the
location, strength and timing of fronts, weather conditions and
precipitation totals.

The preferred model blend for this cycle comprised of the 00Z
ECMWF/CMC/UKMET and the EC and GEFS ensemble means. The weighting
of means increased to 50% for the latter half of the forecast
period. As previously noted, the GFS continued to hang on to the
notion of lagging behind and being stronger shortwave/vort max
descending down the eastern flank of a Western U.S. ridge at the
start of the period.


...Weather/Hazards Highlights...

As an amplified upper trough tracks slowly off the East Coast a
series of shortwaves will dig through the flow; which may
potentially develop into a separated closed low. A wavy trailing
front will settle nearby from the western Atlantic southwestward to
the Gulf. While uncertain lows could act to bring some activity
from the coastal areas up the Eastern Seaboard Sunday and into next
week, particular runoff issues may develop with time for south
Florida urban areas given deeper lower latitude moisture
availability and support to monitor.

While differences on the details persist with time, the general
consensus favors upper trough amplification with multiple systems
into the West along with lead ejection of a southern stream closed
system from offshore Baja through the Southwest into the Rockies.
This pattern change will be a welcomed relief to recent heat across
the West as well as transitioning to a more unsettled and
increasingly wet flow pattern farther inland and downstream over
the Intermountain West and especially the Northern Rockies through
midweek. This will support the possibility for enhanced mountain
snow in the highest elevations of the Northern Rockies. Favorable
upper support, frontal translation, and anomalous moisture along
with downstream cycle-/frontogenesis over the Plains should also
act to enhance precipitation and an emerging convective pattern
from portions of the Northern Rockies to the Northern Plains by
the start of the new week. Maintained the broad Marginal Risk for
the Day 4 ERO from portions of Minnesota, the Dakotas, eastern
Wyoming and northeast Colorado. A broad Marginal Risk was
introduced for the day 5 period as the precipitation advances over
the central part of the country and encompasses the eastern
Dakotas, Minnesota, western Wisconsin, Iowa, eastern Nebraska,
Kansas, western missouri and northeast Oklahoma.


Campbell/Miller/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