Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
350 PM EDT Thu Jul 20 2017
Valid 00Z Fri Jul 21 2017 - 00Z Sun Jul 23 2017
...A slight risk of severe storms for the Lower Great Lakes/Ohio Valley
and the Northern High Plains through Sunday morning...
...Heavy rain likely over parts of the Upper/Middle Mississippi Valley
into the Western Ohio Valley on Friday...
...Temperatures will average 10 degrees above average over parts of the
Central Plains/Middle Mississippi Valley...
...Isolated heavy rain and flash flooding possible across the Southwest
through the weekend...
Conditions are setting up for an extended wet period for portions of the
Upper Mississippi Valley and Great Lakes. A quasi-stationary frontal
boundary will be present over the next few days spanning from the northern
Mid-Atlantic/Northeast to the Northern/Central Plains. Multiple rounds of
showers and thunderstorms will develop and move slowly along this
boundary. The highest concentration of rainfall is forecast along a line
from southeast Minnesota to northwest Indiana. This area has already had
recent precipitation, and with an additional 1 to 3 inches anticipated,
the risk for rapid runoff and flash flooding will increase. A moderate
risk for excessive rainfall has been issued by WPC. Additionally, SPC has
highlighted an area having a slight for severe thunderstorms to develop
from the eastern Dakotas to western Ohio on Friday... and expanding
northward into the Upper Great Lakes and eastward to the northern
Mid-Atlantic by Saturday. Please refer the convective outlooks from SPC
for more information on the severe risk.
Monsoonal moisture, daytime heating and upper-level energy will continue
to trigger showers and thunderstorms over parts of the Southwest/Great
Basin eastward to the Central/Southern Rockies through the weekend. Higher
rainfall rates will remain possible for much of the Southwest and
Southern/Central Rockies, which will increase the risk for flash flooding.
Slight risks for excessive rainfall will persist over much of this region
through Saturday night.
Moisture rich air over the Southern Mid-Atlantic/Southeast Coast and
across the Gulf Coast states will interact with daytime heating and
upper-level impulses to produce showers and thunderstorms. Coverage will
increase during the late afternoon and evening hours. Elsewhere, onshore
flow off the Pacific will aid in producing rain over parts of the Pacific
Northwest through late Friday.
Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php