047
FXUS02 KWNH 290652
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
251 AM EDT Wed May 29 2024

Valid 12Z Sat Jun 1 2024 - 12Z Wed Jun 5 2024

...General Overview...

The upper trough over the Northeast U.S. late in the week is
expected to move offshore by the weekend, with a Canadian surface
high providing a quality airmass with pleasantly cool conditions
across the East Coast followed by a warming trend by early next
week. Meanwhile, a rather unsettled weather pattern is expected to
be in place across the Central U.S. with multiple shortwave
disturbances aloft fueling multiple rounds of showers and
thunderstorms going into the weekend. Widespread showers will also
make a return to the Pacific Northwest early next week as a cold
front moves inland. Most of the Southwest and the Northeast should
remain mostly dry, and the upper ridge likely builds back northward
across southern Texas and thus maintaining hot and humid
conditions.

...Guidance/Predictability Assessment...

The 00Z model guidance suite features good overall synoptic scale
agreement on most aspects of the forecast for Saturday, mainly
among the GFS, ECMWF, and UKMET, along with the ensemble means.
However, at the time of fronts/pressures preparation and the QPF,
the 12Z CMC was an outlier solution near the East Coast with
keeping the offshore upper low much closer to the coast, and then
it become much stronger with an upper ridge developing across the
Northeast later in the forecast period compared to the model
consensus. It also did not have much support from the machine
learning guidance either, so it was not part of the forecast blend
for the entire forecast period. The new 00Z CMC has trended more in
line with the consensus and does not linger the upper low near the
coast like the 12Z run did. The GFS was a little slower with the
storm system crossing the Northern Plains early- mid next week, but
still enough ensemble and ML support to warrant keeping it.

The WPC fronts/pressures forecast was initially derived from a
ECMWF/GFS/UKMET blend, but transitioned to about 40-50% ensemble
means by next Tuesday/Wednesday amid increasing model uncertainty.
Some previous WPC continuity was also maintained for the Saturday
to Tuesday time period.

...Weather/Hazards Highlights...

Numerous showers and thunderstorms are likely to remain ongoing
across portions of the Southern Plains and eastward to the central
Gulf Coast region going into the weekend, with multiple weak
disturbances aloft interacting with a warm and humid air mass. A
broad Marginal Risk area is planned for the Day 4 Excessive
Rainfall Outlook period Saturday from central Texas to southern
Nebraska, and a second area across portions of the Deep South and
into the southern Ohio Valley.

Going into the Day 5 period Sunday, a more organized storm system
approaches the Dakotas and Upper Midwest, and convection should be
widespread enough to merit a Marginal Risk here, with the potential
for a Slight Risk in future updates as the event gets closer in
time. Some strong to severe thunderstorms are also likely with
favorable parameters in place. The potential exists for scattered
QPF maxima of 1-3 inches during this time period for some of these
areas that get repeated rounds of convection. There is also an
increasing likelihood of a late season heavy rain event across
northwestern Oregon and into western Washington on Sunday,
potentially an atmospheric river event, and a Marginal Risk area is
also planned for this region.

The fall-like temperatures across much of the Eastern U.S. are
expected to moderate and return to early June levels in time for
the weekend as the upper trough exits the region. Readings will
also get warmer across much of the Intermountain West, with highs
generally on the order of 5-10 degrees above average through the
weekend, and then spreading eastward across the western High Plains
for early next week. The exception would be for the Pacific
Northwest where widespread clouds and steady rainfall will keep
readings cooler. This also includes a warm-up for the Great Lakes
and into the Northeast. It will remain very hot and humid for much
of southern Texas with the upper ridge building back to the north
through early next week.

Hamrick


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





















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