447
FXUS02 KWBC 251803
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
203 PM EDT Sat May 25 2024

Valid 12Z Tue May 28 2024 - 12Z Sat Jun 01 2024

***Hot and humid conditions continue for southern Texas and the
 Florida Peninsula***

...General Overview...

An amplifying upper trough over the Great Lakes region early in
the week will result in a pattern change across much of the
northeastern quadrant of the U.S. through midweek. A relatively
strong cold front will bring a quality airmass from the Northern
Plains to the East Coast after recent warm and humid conditions.
Another cold front is also forecast to cross the Pacific Northwest
and then the Intermountain West through mid-late week, while an
upper ridge tries to build northward across the Plains. The
heatwave across the Gulf Coast region is expected to abate some by
midweek, although it will still be quite warm and humid for the
remainder of the week across southern Texas.

...Guidance/Predictability Assessment...

The 00z guidance was in reasonable agreement about the overall
synoptic pattern evolution across the lower 48 during the medium
range period. We went with a general model blend, consisting of the
00z EC/CMC/UKMET and 06z GFS for our days 3 and 4 blends with
higher weighting toward the 06z GFS and 00z EC. The 00z European
Ensemble mean is introduced to the blend on day 5 to moderate the
aggressive mid-level troughing over the Northwest found in the
operational GFS and Canadian. We move away from the deterministic
GFS on day 6 since the 06z solution had a negatively tilted mid-
level trough propagating through the northern tier while the Euro,
ensemble means and AI models suggested a more positively tiled
trough. The days 6 and 7 blends consist of the 00z EC/ECE/CMCE and
06z GEFS.


...Weather/Hazards Highlights...

Moisture convergence along a frontal boundary and east of a dryline
across Texas and Oklahoma will likely generate scattered to
numerous showers and thunderstorms, with the potential for episodes
of locally heavy rainfall early to mid week as some MCS activity
develops. The threat of heavy rainfall will be highest in Texas
Tuesday into Wednesday as an upper level shortwave moves over the
southern Plains, so there is now a planned Day 4 (Tuesday) Slight
Risk in the ERO across portions of north-central Texas where the
potential exists for storms with rainfall rates approaching 2
inches per hour. Some strong to severe storms are also likely. The
coverage of showers and storms will likely expand north across the
central and northern Plains later in the week as an organized
frontal system moves into the central U.S. from the Rockies.
Locally heavy rainfall will be possible across portions of the
Rockies going into late Friday and early Saturday as the cold front
intercepts an increasingly humid airmass.

In terms of temperatures, the Gulf Cast region will continue to
remain hot and humid on Tuesday before some limited relief arrives
by midweek as a cold front drops southward. However, the heat and
humidity will likely continue across Deep South Texas and South
Florida with highs running up to 10 degree above average, and heat
indices in the 100-110 degree range, especially for southern Texas.
Some triple digit heat is also likely for the lower elevations of
the Desert Southwest, but very low humidity here will help keep
heat indices in check.

A quality airmass will deliver a refreshingly cooler airmass from
the Upper Midwest to the Mid-Atlantic and points northward as a
pair of cold fronts pass through. courtesy of a building upper
level trough centered over the Great Lakes and Northeast. Cooler
weather is also forecast to reach the northwestern quadrant of the
nation as the next upper trough moves inland across the
Intermountain West, with highs running 5-15 degrees below normal by
the end of the week.

Kebede/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







$$