499
FXUS02 KWNH 280659
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Tue May 28 2024

Valid 12Z Fri May 31 2024 - 12Z Tue Jun 04 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. 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 Friday, but
meaningful differences in the models appear as early as Saturday
with the arrival of the trough across the Pacific Northwest, and
the trough lifting out across the Upper Midwest. The GFS becomes
more progressive with the trough crossing the rockies and northern
Intermountain West, and by Sunday the CMC is stronger with a
shortwave trough over the Midwest and Ohio Valley region, and
becoming stronger with a downstream ridge over the Northeast by
Monday. Model spread becomes noteworthy by early next week across
the northern tier states with limited forecast confidence on
specifics, but better agreement with respect to the building upper
level ridge across Texas. The WPC fronts/pressures forecast was
initially derived from a deterministic model blend, but
transitioned to about 50% ensemble means by next Tuesday amid
increasing model uncertainty. Some previous WPC continuity was also
maintained through the Friday to Monday time period.

...Weather/Hazards Highlights...

Numerous showers and thunderstorms are likely to remain ongoing
across much of the central and southern Plains going into Friday
and the weekend with multiple weak disturbances aloft interacting
with a warm and humid air mass. A broad Marginal Risk area
continues for the Day 4 Excessive Rainfall Outlook period Friday
from central Texas to southern Wisconsin. There is an embedded
Slight Risk area planned for the ArkLaTex region, where MCS
activity is most likely to develop based on the latest
deterministic guidance. There may be some abatement in the coverage
of convection on Saturday across the Central U.S., but still enough
to merit a few Marginal Risk areas where the best combination of
upper level forcing and moisture convergence will likely exist.
Some strong to severe thunderstorms are also likely each day. The
potential exists for scattered QPF maxima of 2-4 inches for the
Friday to Saturday time period for some of these areas that get
repeated rounds of convection.

The fall-like temperatures across much of the Eastern U.S. are
expected to slowly 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 Western U.S., 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. 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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