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FXUS02 KWBC 080651

PMDEPD



Extended Forecast Discussion

NWS Weather Prediction Center College Park MD

251 AM EDT Wed May 8 2024



Valid 12Z Sat May 11 2024 - 12Z Wed May 15 2024



...Emerging Texas/Gulf Coast/Southeast Heavy Rainfall Threat...





...Pattern Overview and Guidance/Predictability Assessment...



Overall, guidance reasonably agrees for mean troughing to linger 

over the eastern U.S. while a modest Rex block/split flow pattern 

will take its time to de-amplify over the western U.S. through much

of a mainly benign medium-range weather pattern there.



A number of shortwave troughs are forecast to rotate around the 

mean upper trough in the East, and they present some issues as to 

when and where the shortwaves may interact and/or amplify. This has

implications to coastal cyclogenesis specifics for this weekend.

WPC progs have consistently shown moderate low developments given

uncertainties, but there have been some stronger all-things come

together solutions. Most recently, the 12 UTC UKMET offered the 

most robust low far southward offshore the Southeast to then 

up/off the coast, but the 00 UTC UKMET has started to back-off.



As for the Rex block in the West, models generally show a gradual 

pattern flattening with time, with emerging differences on whether 

a southern stream low-amplitude trough ejects to the southern 

Plains or remains slow-moving over the Southwest into early-mid 

next week. Despite timing differences and varied lead impulses to

consider, there is a growing downstream response signal for

rainfall fueling moisture/instability to increasingly return/spread

over TX and the Gulf Coast region/Southeast Sunday-next Wednesday.



Given uncertainties, the WPC medium range product suite was primarily

derived from a composite blend of compatible guidance from the

latest GEFS/ECMWF/Canadian ensemble means and the National Blend 

of Models to offer a solid pattern base and reasonable continuity.



...Weather/Hazards Highlights...



Moderate rainfall will linger this weekend over the Northeast with

wrapback moisture and upper trough support as downstream energy 

transference leads to coastal low genesis, but details remain 

uncharacteristically uncertain even as we enter short range time 

frames. Upstream northern stream systems will then periodically 

offer bouts of mainly lighter rains from the north-central U.S. to

the Great Lakes/Northeast this weekend to next midweek, albeit 

also with uncertainty in focus/timing, but with limited impact.



Meanwhile to the south, a cooling/slowing trailing front along 

with a reinforcing front and upper shortwaves are expected to 

periodically focus precipitation from the southern Rockies/Plains 

out through the Gulf of Mexico and Gulf Coast/Florida this weekend

through early-mid next week. A growing but still not solidified 

guidance signal offers support for moisture to increase along the 

Gulf Coast and vicinity ahead of the returning warm front. Heavy 

rain may work inland over time as the front edges northward. The 

WPC Day 5/Sunday into Monday Excessive Rainfall Outlook introduced

a Marginal Risk area from SE Texas to southern Louisiana/Mississippi.

Drenched soils from recent heavy rains also prompted an embedded 

Slight Risk area around Houston/SE Texas and SW Louisiana. Heavy 

rain and a threat of runoff issues may also spread through the 

central Gulf Coast to the Southeast early-mid next week to monitor.



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































































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