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FXUS02 KWBC 050712

PMDEPD



Extended Forecast Discussion

NWS Weather Prediction Center College Park MD

312 AM EDT Sun May 5 2024



Valid 12Z Wed May 08 2024 - 12Z Sun May 12 2024





...Mid-South/Ohio Valley Excessive Rain/Severe Threat midweek

shifts to the Central Gulf Coast States/Appalachians Thursday...





...Guidance/Predictability Assessment...



Recent guidance cycles have shown good agreement for the overall 

synoptic pattern, albeit with local uncertainties. A blend of best

clustered guidance from the GFS/ECMWF models and to a lesser 

extent more run to run varied UKMET/Canadian runs Wednesday-Friday

tends to mitigate smaller scale issues consistent with uncertainty

and has good ensemble and NBM support and continuity.



By next weekend there remain significant differences between model

guidance and run to run continuity on how far south and east the 

lingering Plains energy works into the Great Lakes/Northeast. There

is also uncertainty out West with the evolution of energy around 

the Great Basin and a blocky upper ridge/high Rex type pattern to 

the north. Accordingly, the WPC blend has again trended to more 

compatable and run to run consistent GEFS/ECMWF/Canadian ensemble 

means. This maintains maximum WPC product continuity.



...Weather/Hazards Highlights... 



Amplified upper trough/low energies will shift slowly from the

northern Plains midweek to the East next weekend along with

a main/reforming parent surface lows then moderate coastal low. 



There will be higher elevation snows back over the north-central 

Rockies into mid-late week on the backside of the main trough/low 

as depicted in the WPC Winter Weather Outlook. Rainfall on the 

west side of the strong surface low could be heavy across eastern 

Montana given upper-level support. However, this region is not 

particularly sensitive to flooding concerns, and instability should

be limited wrapping around the low. A WPC Excessive Rainfall 

Outlook (ERO) Marginal Risk area remains in place Day 4/Wednesday 

for this area given the potential for protracted heavy rain.



Meanwhile, an associated lead and wavy/trailing frontal system 

will gradually work downstream across the central and eastern 

states to intercept and pool return flow instability and moisture. 

This will set the stage for a widespread and generally broad comma 

shaped area of rainfall to include a threat for excessive rainfall 

and strong to severe thunderstorms for areas near the Mid-South 

and Ohio Valley midweek and the Central Gulf Coast States to 

Appalachians into the Southeast Thursday into Friday.



A Marginal Risk and embedded Slight Risk ERO remains from the Mid-

Mississippi Valley through the Ohio Valley states Day 4/Wednesday 

as fronts push farther toward the east and northeast and interact 

with pooling moisture and instability. The Storm Prediction Center 

highlights a broad area of the Midwest to Mississippi Valley/parts 

of the Southern Plains for severe weather potential into midweek. 

A favorable pattern will continue for rain and thunderstorms across

the South with the trailing cold front and broadly onward across 

the East where dowsstream energy track may support moderate late 

next week coastal low development off the Northeast to monitor.



Expect much cooler than normal temperatures for parts of the West 

Wednesday/Thursday under upper troughing. Meanwhile, mean upper 

ridging will favor quite warm temperatures from the South through 

the Appalachians/Mid- Atlantic to threaten record seasonal values. 

90s are forecast across the southern tier, with potential for south

Texas excessive heat with temperatures over 100F and higher heat 

indices. Temperatures broadly cool later week into next weekend.



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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