162
FXUS02 KWBC 271832
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
232 PM EDT Mon May 27 2024

Valid 12Z Thu May 30 2024 - 12Z Mon Jun 03 2024


...General Overview...

The upper level pattern across the continental U.S. will be
featured with a trough over the Northern Rockies, a ridge over the
Upper Midwest, and a trough over the Northeast U.S. for the
beginning of the forecast period Thursday. Both of these troughs
move rather slowly eastward through Saturday, while the southern
tier states have more zonal flow aloft. The trough crossing the
Rockies will be accompanied with a surge of moisture from the Gulf
of Mexico ahead of an approaching frontal boundary, and this will
fuel multiple rounds of heavy rain and thunderstorms from northern
Texas to the central Plains for the second half of the work week.
The trough then reaches the Upper Midwest by next weekend and then
lifts northward into Canada, while the upper ridge rebuilds across
Texas late in the forecast period.


...Guidance/Predictability Assessment...

Latest model guidance remains in good overall synoptic agreement
for much of the period, but with some lingering uncertainties in
timing of individual systems. There was good enough agreement the
first half of the period for an equal blend of the latest
deterministic solutions. After this, models agree an upper low
south of the Gulf of Alaska will send a shortwave or two into the
Pacific Northwest this weekend/early next week but disagree on the
timing and amplitude of this evolution, leading to models becoming
out of phase with each other. Transitioned towards more of the
ensemble means the second half of the period given the
uncertainties. Overall though, this maintained good agreement with
the previous WPC forecast.


...Weather/Hazards Highlights...

Numerous showers and thunderstorms are likely across much of the
central and southern Plains going into the second half of the work
week as a warm front lifts up from the western Gulf and advects
copious moisture northward. This will also be in tandem with
increasing lift afforded by an incoming upper trough from the
Rockies. A broad Marginal Risk area continues for the Day 4
Excessive Rainfall Outlook period Thursday from central Texas to
the eastern Dakotas. There is an embedded Slight Risk, which was
expanded northward from the initial overnight issuance, from north-
central Texas into southeast Nebraska, where MCS activity is most
likely to develop. Additional heavy rain is expected on Friday
across many of these same areas and eastward, and so maintained a
broad Day 5 Marginal Risk area from northern/eastern Texas and the
lower Mississippi Valley to the Upper Midwest. There will likely be
the need for a Slight Risk area during this time in future
updates, but the differences in QPF maxima among the guidance
preclude having any Slights at this time. Some strong to severe
thunderstorms are also likely. The potential exists for 3-5 inches
of rainfall through late Friday for some of these areas that get
repeated rounds of convection.

General troughiness across the northern states should continue to
allow scattered summertime convection across the central Plains-
Mississippi Valley region through the weekend and into early next
week as well. Another trough just off the West Coast should also
bring in a round of rainfall to parts of the Pacific Northwest late
weekend.

Hazardous heat is expected to continue across South Texas through
much of the period with daytime highs in the low-mid 100s (and even
higher heat indices) indicating a major to localized extreme heat
risk. Hot and humid conditions are also expected to continue
across much of the Gulf Coast region, including the Florida
Peninsula, going into the end of the week, but a few degrees cooler
compared to what is happening now. The opposite will hold true
from the Great Lakes to the Mid-Atlantic and Northeast as a
relatively strong cold front heralds the arrival of a high quality
airmass with pleasantly cool conditions and lower humidity to close
out the week. There will likely be some showers across the
northeastern quadrant of the nation in conjunction with the
trough/upper low that passes through the region. Cooler weather is
also expected from the Pacific Northwest to the Northern Rockies
courtesy of the upper trough moving overhead, and then a return to
warmer conditions for much of the Western U.S. by next Sunday.

Santorelli/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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