Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1236 PM EDT Mon May 24 2021
Valid 12Z Thu May 27 2021 - 12Z Mon May 31 2021
...Overview...
A pair of shortwave troughs will track east over the northern tier
of the CONUS through Monday while the next trough digs down the
West Coast, closing off southern California Sunday as the pattern
becomes less progressive with ridging up the central Plains.
Rainfall will be focused along a cold front from the central
Plains to the East Coast on Friday, sagging south to the Gulf
Coast with the front Saturday before focusing ahead of the western
trough/low over the central Plains Sunday/Monday.
...Guidance Evaluation and Preferences...
The latest deterministic models continue to depict reasonable
clustering for the Thu-Sat period as low pressure along the front
moves from the Plains to the Ohio Valley to a developing cold air
damming wedge over the Mid-Atlantic. By then, uncertainty
increases with a southern stream shortwave through Texas/lower MS
Valley as well as the unfolding western trough/low and potential
stalling troughing along the East Coast. Did a typical trend
toward a majority ensemble blend (GEFS/ECENS) with a small
weighting of the GFS/ECMWF/Canadian deterministic runs to offer
just a bit of detail where appropriate. Blended the 12Z/13Z
National Blend of Models with ECMWF/GFS/ECENS/GEFS for
temperatures/PoPs/QPF.
...Weather Highlights/Hazards...
Highest chances of rainfall during the period are Thursday
night/Friday ahead of an eastward moving low from the central
Plains to the Corn Belt eastward to the central Appalachians along
a wavy frontal boundary with a potential area of organized and
moderate to heavy rain shifting across the mid/lower Mississippi
Valley into the Ohio Valley. Areas in the Mid-Atlantic look to see
light/modest showers in the developing cold air damming. Then,
return flow up the Plains meets the next cold front with potential
repeating rain over the central Plains Sunday/Monday.
Temperatures will be cool, 10 to 15 degrees below normal, in the
northern Plains to Upper Midwest to northeast Friday/Saturday,
expanding south down the Mid-Atlantic Saturday with the cold air
damming. Meanwhile hot conditions, 10 to 15 degrees above normal
and near records, persist in the Southeast until the cold frontal
passage Saturday into Sunday. For the rest of the Memorial Day
weekend, expect near to slightly below normal temperatures east of
the Rockies, while the Pacific Northwest looks to see a warming
trend with temperatures 10 to 20 degrees above normal by Memorial
Day.
Jackson
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, winter weather outlook probabilities
and heat indices are at:
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/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml