Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
358 PM EDT Fri Jun 28 2024

Valid 00Z Sat Jun 29 2024 - 00Z Mon Jul 01 2024

...Severe thunderstorms and flash flooding possible across portions of the
central Plains and Midwest today...

...Unsettled weather with the potential for heavy rain and strong storms
enter the Lower Great Lakes and Upper Ohio Valley on Saturday...

...Dangerously hot conditions will continue from parts of the southern
Plains to the Southeast this weekend...


A low pressure system is pushing across the northern and central Plains
this afternoon. The low pressure center is moving east along the
U.S.-Canada border with a trailing cold front extending south and west
from the Upper Mississippi Valley through the Central Plains and a warm
front lifting north across the Midwest ahead of the system. Conditions
will be favorable for scattered severe thunderstorms to develop through
this evening, and potential storm hazards may include large hail, damaging
winds, and a couple of tornadoes. Strong storms may also produce locally
heavy rainfall that could lead to instances of flash flooding,
particularly in areas where soils are saturated from recent heavy rains
and areas where training/repeating storms develop.

The low pressure system will track eastwards on Saturday, slowly moving
across the Upper Great Lakes region, with the trailing cold front
extending back through the Ohio and Middle Mississippi Valleys to the
central Plains and southern Rockies and with the leading warm front
lifting across the Mid-Atlantic into the Northeast. Shower and
thunderstorm chances will shift east with the system, and some storms may
become severe on Saturday. The main storm hazards will include scattered
damaging winds, a couple of tornadoes, and locally heavy downpours. Due to
the slow moving nature of the showers and storms, isolated to scattered
instances of flash flooding will be possible along the entire length of
the cold front.

On Sunday, the system will gain a bit more momentum, and the central low
will push into southeastern Canada while the trailing cold front moves
towards the East Coast. Meanwhile, another low pressure system will
develop over the Pacific Northwest/southern Canada, which will bring
precipitation chances back to the Pacific Northwest on Sunday that will
spread into the northern and central Plains on Monday.

Dangerous heat will continue to be a major weather story through the last
couple days of June as an upper level ridge strengthens over the
south-central U.S. and the Southeast. This will lead to above average
temperatures impacting areas from the central/southern Plains to the
Southeast, with summer heat also building across the Southwest and
northern High Plains by Sunday. High temperatures are forecast to reach
the upper 90s and low 100s in the southern Plains and Lower Mississippi
Valley today, where Excessive Heat Warnings and Heat Advisories are in
effect. Scattered afternoon thunderstorms may keep the sizzling heat at
bay across the Southeast, but highs into the mid-90s can still be expected
this weekend. If spending time outdoors be sure to follow proper heat
safety by taking frequent breaks, staying hydrated, and checking on
neighbors.

Dolan


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
305 PM EDT Fri Jun 28 2024

Valid 12Z Mon Jul 01 2024 - 12Z Fri Jul 05 2024


...Hazardous heat from the South and vicinity next week to
portions of the East/Southeast and California into the Fourth...


...Overview...

An active summer weather pattern will continue to feature a
pattern of energetic and progressive northern stream shortwaves
through the northern states as a strong ridge shifts slowly over
the South, eventually building back into the East and West Coasts.
A threat for heavy rains will be across the Upper Midwest Monday-
Tuesday, with focus slowly working over the Mid-Mississippi/Ohio
Valleys and vicinity through the holiday.It should also remain a
wet pattern across the Southwest with a continuous and highly
anomalous moisture feed around the western periphery of the ridge.
Hazardous heat threats will focus across much of the southern
Plains to Southeast/East over the period, building into parts of
the Southwest and interior California by mid to later next week.

...Guidance/Predictability Assessment...

Guidance forecast spread continues a trend of being lower than
normal through medium range time scales in a pattern with above
average predictability overall. The WPC product suite was mainly
derived for the Monday-Wednesday timeframe from a blend of the 06
UTC GFS and 00 UTC ECMWF/UKMET/Canadian along with the generally
compatible 13 UTC National Blend of Models (NBM) and WPC
continuity. Applied most blend weighting to the ECMWF/UKMET that
depict a stronger and more resilient southern upper ridge that may
prove slow to dissipate. Opted to switch the favored blend to best
clustered guidance from the ECMWF and GEFS/ECMWF ensemble means
along with the NBM for later next week amid slowly growing, but
manageable variances.

...Weather/Hazards Highlights...

It generally remains the case that widespread showers and storms
are expected to be ongoing across the Upper Midwest on Monday ahead
of a frontal boundary and an upper level impulse moving through
the region. Although the overall forecast rainfall totals are
currently expected to be in the 1-2 inch range, this would be
falling on highly saturated grounds in many cases, which would be
an aggravating factor when it comes to flooding potential.
Therefore, the Slight Risk remains valid for the new Day 4 ERO
across much of Minnesota and portions of adjacent states. Marginal
and slight risk ERO areas are planned for Day 5 as the signal for
a main
axis of heavy convection shifts to/from Kansas/Iowa through
Wisconsin/Illinois into the Great Lakes, possible spreading across
the Ohio Valley toward the Mid-Atlantic over the holiday period.
Elsewhere, moisture pooling ahead of the cold front approaching the
Southeast U.S. coast may lead to some repeated rounds of storms
with high rainfall rates on Monday, where a Day 4 Marginal Risk
area is planned.

Monsoonal flow into the Southwest states will continue the daily
threat for showers and storms through much of the period. Marginal
risks remain in place across parts of Arizona, New Mexico, and
southern Colorado for both the Day 4 and 5 EROs, with the
potential for upgrades to a Slight Risk in subsequent updates
depending on short range rainfall. This pattern is likely to
persist into next Wednesday as well given the lingering and
deepened moisture channel on the upper ridge western periphery.

It will continue to remain hot and humid across the Southern U.S.
for much of next week, with the hottest conditions centered across
Texas and Oklahoma where triple digit high temperatures are likely.
Some of this heat likely reaches the Mid-Atlantic region by the
end of the week with highs in the middle to upper 90s. It will also
be getting hotter for the inland lower elevations of California and
into the Arizona Deserts with widespread 100-110 degree readings
likely, and locally higher for the normally warmer locations.

Hamrick/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
345 AM EDT Fri Jun 28 2024

Valid 00Z Sat Jun 29 2024 - 00Z Sat Jul 06 2024

The latest guidance continues to show a typical easterly trade
wind pattern through the upcoming week, supported by high pressure
meandering to the north of the state. Winds should be on the
lighter side through the weekend as an upper trough/low moves just
north of Hawaii. Some increase in moisture is possible with the
upper low approaching, with any enhanced rainfall focused in the
typical windward areas. An upper level high looks to build back in
to the northeast of Hawaii by mid to later next week with some
uptick in wind speeds expected. Models show good overall agreement
on the large scale pattern through the period.

Hamrick

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
859 PM EDT Fri Jun 28 2024
Day 1
Valid 01Z Sat Jun 29 2024 - 12Z Sat Jun 29 2024


...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN KANSAS
INTO THE MID MISSISSIPPI VALLEY TONIGHT...

...01Z Update...
Local radar shows backbuilding convection centered near a slow-
moving wave over eastern Kansas, and near the intersection of a
cold front sliding southeast through the Missouri Valley and a warm
front extending southeast across Missouri. These storms are being
fueled by a deep moisture pool (PWs ~2 inches), fed by southerly
low level inflow. The hi-res guidance members which have a
reasonable handle on the current conditions, including the 12Z ARW2
and recent runs of the HRRR, indicate some additional backbuilding
before cells begin to slowly train to the southeast during the
overnight hours. The result is a northwest to southeast axis of
heavy accumulations from eastern Kansas into western Missouri.
These moisture-robbing storms along with more progressive flow to
the north will likely lessen the potential for slow-moving, heavy-
rainfall producers further to the north. Therefore, trimmed away
some of the Slight Risk, but maintained a Marginal Risk further
northeast through the mid Mississippi Valley into the Great Lakes.

Elsewhere, expanded the Marginal Risk across eastern Arizona and
western New Mexico, where scattered storms and an isolated threat
for flash flooding will continue before storms diminish with the
loss of daytime heating.

Pereira

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
859 PM EDT Fri Jun 28 2024
Day 2
Valid 12Z Sat Jun 29 2024 - 12Z Sun Jun 30 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE LOWER GREAT LAKES AND UPSTATE NEW YORK AS WELL AS NORTHEAST NEW
MEXICO...

...2000Z Update...

The main change to the Day 2 ERO was to add a Slight Risk into
northeastern New Mexico. A stalling/meandering front in that area
will combine with PWs increasing to above the 90th or 95th
percentile. Hi-res models are focusing on that area for convection
with high rain rates, and thus the 12Z HREF has probabilities of
30-40 percent chance of exceeding FFG, with higher probabilities to
70 percent of exceeding 10-year ARI. This all warrants a Slight
Risk that was coordinated with the Albuquerque WFO.

The reasoning below remains valid for the Marginal to Slight Risks
in the northeastern quadrant of the U.S., with some expansion of
the southern Slight Risk northward into far southwestern New York
and eastward into more of Pennsylvania, per recent model trends
(especially the hi-res). Continued to hold off on any embedded
Slight Risk in the south-central Plains/Mississippi Valley due to
considerable model spread in the highest QPF.

Tate

...Previous Discussion...

Coverage of showers and thunderstorms should be increasing over
portions of the Ohio Valley prior to the start of the Day 2 outlook
period at 29/12Z. Precipitable water values look to be approaching
2 inches over parts of the Ohio Valley will be in place by the
time height falls from a sharpening mid-level trough approaching
from Canada arrives. The broad-scale ascent afforded by the
approaching shortwave...the deep moisture and wet bulb zero values
at or above 10 kft suggest some intense downpours are possible.
With at least some risk of cell training and perhaps some
interaction with terrain...felt an upgrade to Slight Risk was
needed...although the antecedent conditions may mitigate the
flooding potential somewhat. A second Slight Risk was introduced
across portions of upstate New York which was more hydrologic
sensitivity than the Ohio Valley given recent rains. Concern for
excessive rainfall extends southward and westward from these Slight
Risk areas along/near a cold front making its way into the
Tennessee Valley/Central Plains and southern Rockies. Precipitable
water values in the 2 to 2.25 inch range should be pooling along
the front from the eastern seaboard as far west as Arkansas and
Oklahoma by 30/00Z. Model guidance shows a lot of spread in this
region and a Marginal Risk was maintained due to the potential for
any cells that form to be efficient rain makers.

Bann

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
859 PM EDT Fri Jun 28 2024
Day 3
Valid 12Z Sun Jun 30 2024 - 12Z Mon Jul 01 2024

...THERE IS A MARGINAL RISK OVER PORTIONS OF THE EASTERN SEABOARD,
SOUTHWEST U.S., CENTRAL PLAINS, AND NORTHERN HIGH PLAINS...

...2000Z Update...

A Marginal Risk area was added to central Kansas. This area is
arising as a concern especially in the hi-res models that go out
that far. Storms are likely to be ongoing Sunday morning,
propagating east from Saturday's southern High Plains convection.
This will be on the cusp of the instability gradient, a typically
favored location for storms with high rain rates. It is possible
the risk area will shift around in placement in future model cycles
if models vary.

No significant changes in forecast reasoning for the other
Marginal Risk areas. The Four Corners Marginal was expanded north a
bit to be consistent with recent model guidance.

Tate

...Previous Discussion...

...Eastern U.S...
Showers and thunderstorms capable of producing heavy to possibly
excessive rainfall will persist along and ahead of a progressive
front associated with a northern stream trough. Current guidance
continues to focus the heaviest rainfall amounts and rates over
portions of the Mid-Atlantic seaboard at the time of maximum
instability extending into portions of the coastal Carolinas.
Overall the upper dynamics should keep cells moving but with
precipitable water values approaching 2 inches along/near the
front...flooding is possible in areas of poor drainage and urban
areas.

...Southwest U.S...
Moisture begins to get drawn northward from Mexico on the western
side of a sprawling mid-level high over the Southern Plains.
Isolated to widely scattered late afternoon and evening convection
has the potential to produce locally heavy rainfall as the sub-
cloud layer moistens up in response to precipitable water values
over 1.5 inches crossing the border into southern Arizona by early
evening.

...Plains of western North Dakota and eastern Montana...
A mid- level trough will be moving out of the Northwestern US and
emerging from the northern Rockies by afternoon helping to focus
late day convection. Any convection that forms during the day
should encounter deeper moisture over North Dakota by the
evening...leading to a threat of excessive rainfall. Model guidance
does show increasing moisture transport into the region by a
strengthening low level jet during the evening with at least some
concern for convection to persist into the night given the model
shear profile.

Bann

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
305 PM EDT Fri Jun 28 2024


It generally remains the case that widespread showers and storms
are expected to be ongoing across the Upper Midwest on Monday ahead
of a frontal boundary and an upper level impulse moving through
the region. Although the overall forecast rainfall totals are
currently expected to be in the 1-2 inch range, this would be
falling on highly saturated grounds in many cases, which would be
an aggravating factor when it comes to flooding potential.
Therefore, the Slight Risk remains valid for the new Day 4 ERO
across much of Minnesota and portions of adjacent states. Marginal
and slight risk ERO areas are planned for Day 5 as the signal for
a main
axis of heavy convection shifts to/from Kansas/Iowa through
Wisconsin/Illinois into the Great Lakes, possible spreading across
the Ohio Valley toward the Mid-Atlantic over the holiday period.
Elsewhere, moisture pooling ahead of the cold front approaching the
Southeast U.S. coast may lead to some repeated rounds of storms
with high rainfall rates on Monday, where a Day 4 Marginal Risk
area is planned.

Monsoonal flow into the Southwest states will continue the daily
threat for showers and storms through much of the period. Marginal
risks remain in place across parts of Arizona, New Mexico, and
southern Colorado for both the Day 4 and 5 EROs, with the
potential for upgrades to a Slight Risk in subsequent updates
depending on short range rainfall. This pattern is likely to
persist into next Wednesday as well given the lingering and
deepened moisture channel on the upper ridge western periphery.

It will continue to remain hot and humid across the Southern U.S.
for much of next week, with the hottest conditions centered across
Texas and Oklahoma where triple digit high temperatures are likely.
Some of this heat likely reaches the Mid-Atlantic region by the
end of the week with highs in the middle to upper 90s. It will also
be getting hotter for the inland lower elevations of California and
into the Arizona Deserts with widespread 100-110 degree readings
likely, and locally higher for the normally warmer locations.

Hamrick/Schichtel

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
305 PM EDT Fri Jun 28 2024


It generally remains the case that widespread showers and storms
are expected to be ongoing across the Upper Midwest on Monday ahead
of a frontal boundary and an upper level impulse moving through
the region. Although the overall forecast rainfall totals are
currently expected to be in the 1-2 inch range, this would be
falling on highly saturated grounds in many cases, which would be
an aggravating factor when it comes to flooding potential.
Therefore, the Slight Risk remains valid for the new Day 4 ERO
across much of Minnesota and portions of adjacent states. Marginal
and slight risk ERO areas are planned for Day 5 as the signal for
a main
axis of heavy convection shifts to/from Kansas/Iowa through
Wisconsin/Illinois into the Great Lakes, possible spreading across
the Ohio Valley toward the Mid-Atlantic over the holiday period.
Elsewhere, moisture pooling ahead of the cold front approaching the
Southeast U.S. coast may lead to some repeated rounds of storms
with high rainfall rates on Monday, where a Day 4 Marginal Risk
area is planned.

Monsoonal flow into the Southwest states will continue the daily
threat for showers and storms through much of the period. Marginal
risks remain in place across parts of Arizona, New Mexico, and
southern Colorado for both the Day 4 and 5 EROs, with the
potential for upgrades to a Slight Risk in subsequent updates
depending on short range rainfall. This pattern is likely to
persist into next Wednesday as well given the lingering and
deepened moisture channel on the upper ridge western periphery.

It will continue to remain hot and humid across the Southern U.S.
for much of next week, with the hottest conditions centered across
Texas and Oklahoma where triple digit high temperatures are likely.
Some of this heat likely reaches the Mid-Atlantic region by the
end of the week with highs in the middle to upper 90s. It will also
be getting hotter for the inland lower elevations of California and
into the Arizona Deserts with widespread 100-110 degree readings
likely, and locally higher for the normally warmer locations.

Hamrick/Schichtel

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
1031 AM EDT Mon May 13 2024

Valid 00Z Tue May 14 2024 - 00Z Fri May 17 2024

...WPC Winter Weather Desk no longer routinely staffed this
summer...

Pending any significant winter weather, the WPC Winter Weather Desk
will not be staffed this summer. The desk will resume continuous
staffing starting in late September 2024.

Most of the winter products from WPC will continue to be produced,
including the Winter Storm Severity Index (WSSI), Probabilistic
Winter Storm Severity Index (WSSI-P), and the Probabilistic Winter
Precipitation Forecasts (PWPF).

WPC

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
305 PM EDT Fri Jun 28 2024

Valid 12Z Mon Jul 01 2024 - 12Z Fri Jul 05 2024


...Hazardous heat from the South and vicinity next week to
portions of the East/Southeast and California into the Fourth...


...Overview...

An active summer weather pattern will continue to feature a
pattern of energetic and progressive northern stream shortwaves
through the northern states as a strong ridge shifts slowly over
the South, eventually building back into the East and West Coasts.
A threat for heavy rains will be across the Upper Midwest Monday-
Tuesday, with focus slowly working over the Mid-Mississippi/Ohio
Valleys and vicinity through the holiday.It should also remain a
wet pattern across the Southwest with a continuous and highly
anomalous moisture feed around the western periphery of the ridge.
Hazardous heat threats will focus across much of the southern
Plains to Southeast/East over the period, building into parts of
the Southwest and interior California by mid to later next week.

...Guidance/Predictability Assessment...

Guidance forecast spread continues a trend of being lower than
normal through medium range time scales in a pattern with above
average predictability overall. The WPC product suite was mainly
derived for the Monday-Wednesday timeframe from a blend of the 06
UTC GFS and 00 UTC ECMWF/UKMET/Canadian along with the generally
compatible 13 UTC National Blend of Models (NBM) and WPC
continuity. Applied most blend weighting to the ECMWF/UKMET that
depict a stronger and more resilient southern upper ridge that may
prove slow to dissipate. Opted to switch the favored blend to best
clustered guidance from the ECMWF and GEFS/ECMWF ensemble means
along with the NBM for later next week amid slowly growing, but
manageable variances.

...Weather/Hazards Highlights...

It generally remains the case that widespread showers and storms
are expected to be ongoing across the Upper Midwest on Monday ahead
of a frontal boundary and an upper level impulse moving through
the region. Although the overall forecast rainfall totals are
currently expected to be in the 1-2 inch range, this would be
falling on highly saturated grounds in many cases, which would be
an aggravating factor when it comes to flooding potential.
Therefore, the Slight Risk remains valid for the new Day 4 ERO
across much of Minnesota and portions of adjacent states. Marginal
and slight risk ERO areas are planned for Day 5 as the signal for
a main
axis of heavy convection shifts to/from Kansas/Iowa through
Wisconsin/Illinois into the Great Lakes, possible spreading across
the Ohio Valley toward the Mid-Atlantic over the holiday period.
Elsewhere, moisture pooling ahead of the cold front approaching the
Southeast U.S. coast may lead to some repeated rounds of storms
with high rainfall rates on Monday, where a Day 4 Marginal Risk
area is planned.

Monsoonal flow into the Southwest states will continue the daily
threat for showers and storms through much of the period. Marginal
risks remain in place across parts of Arizona, New Mexico, and
southern Colorado for both the Day 4 and 5 EROs, with the
potential for upgrades to a Slight Risk in subsequent updates
depending on short range rainfall. This pattern is likely to
persist into next Wednesday as well given the lingering and
deepened moisture channel on the upper ridge western periphery.

It will continue to remain hot and humid across the Southern U.S.
for much of next week, with the hottest conditions centered across
Texas and Oklahoma where triple digit high temperatures are likely.
Some of this heat likely reaches the Mid-Atlantic region by the
end of the week with highs in the middle to upper 90s. It will also
be getting hotter for the inland lower elevations of California and
into the Arizona Deserts with widespread 100-110 degree readings
likely, and locally higher for the normally warmer locations.

Hamrick/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