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FXUS02 KWBC 190659

PMDEPD



Extended Forecast Discussion

NWS Weather Prediction Center College Park MD

259 AM EDT Fri Apr 19 2024



Valid 12Z Mon Apr 22 2024 - 12Z Fri Apr 26 2024





...General Overview...



The forecast period begins on Monday with an upper trough crossing

the Southeast U.S., and a second trough amplifying over the Great

Lakes and the Northeast U.S. going into Tuesday-Wednesday. This 

will bring a strong cold front across the Eastern U.S. with colder 

high pressure settling in behind it. A second trough likely 

develops over the Western U.S. by the middle to end of the work 

week, with a corresponding surface low expected to develop over the

western High Plains by Friday. This would probably be the next 

best chance for potentially impactful weather in terms of rain, 

thunderstorms, and wind across the Central U.S.





...Guidance/Predictability Assessment...



The 00Z model guidance suite indicated better than average agreement

across the continental U.S. through the middle of next week on the

synoptic scale features. In terms of specific features, the 

guidance is showing a stronger solution across the Northeast U.S. 

for midweek as a potent disturbance drops south from the Hudson Bay

region and invigorates the shortwave approaching from the Great 

Lakes region. The GFS is most amplified with this trough and has 

the core of the upper low over northern New England. For the 

Western U.S., the development of the broad upper trough by the end 

of next week will be contingent on the level of phasing of two 

separate shortwave troughs, with one originating west of 

California, and the other dropping south from the Gulf of Alaska. 

The GFS is quicker to bring the trough onshore across the 

southwestern U.S, whereas the CMC is slowest with this, and the 

GEFS mean serves as a reasonable middle ground solution. The WPC 

fronts/pressures forecast was primarily derived from a 

CMC/ECMWF/GFS consensus through Wednesday, and then increasing 

contributions from the GEFS mean going into Thursday and Friday 

while still using some previous WPC continuity.



...Weather/Hazards Highlights... 



The shortwave crossing the Upper Midwest to the Great Lakes and 

then the Northeast will be accompanied by some generally light to 

moderate rain Monday into Tuesday, mainly ahead of and along the cold

front. Given the overall progressive nature of this storm system, 

and the lack of appreciable instability and QPF, no flash flood 

threat areas are currently warranted for the excessive rainfall 

outlooks on both days 4 and 5. The next round of light rain and 

mountain snow should arrive in the northwestern states by next 

Wednesday ahead of the amplifying trough, and becoming heavier 

going into Thursday across the Northern Rockies. More widespread 

showers and storms are then expected to develop across the Plains 

by the end of the week as moisture and instability increase in the 

warm sector of a surface low pressure system, and the potential 

exists for some strong storms ahead of the dryline in the Southern 

Plains.



In terms of temperatures, there will likely be a modest warm up 

expected from the Southern Plains to the Mid-Atlantic region on 

Tuesday, but the next shortwave into the northern tier should keep 

temperatures chilly for this time of year from the Rockies to the 

Great Lakes and eventually into the Northeast for midweek. Initial

ridging out west should support above normal temperatures, but 

temperatures are likely to fall to below normal levels along much 

of the West Coast and inland by next Thursday. Warmer temperatures 

and increasing humidity are forecast for the south-central U.S. by 

next Friday as the upper ridge axis builds back, and southerly flow

from the western Gulf advects moisture northward ahead of a 

developing surface low.



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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