Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
335 PM EDT Tue Jul 27 2021

Valid 00Z Wed Jul 28 2021 - 00Z Fri Jul 30 2021

...Excessive Heat Warning over parts of the Northern High Plains; Heat
Advisory over parts of the Lower Mississippi Valley/Southern Plains,
Northern/Central Plains, and the Northern High Plains...

...There is a Slight Risk of excessive rainfall over parts of the Upper
Midwest/Upper Great Lakes Wednesday through early Thursday and for the
Southeast through Wednesday morning...

...There is a Slight Risk of severe thunderstorms over parts of the Upper
Midwest and the Lower Great Lakes through Wednesday morning...

Hot conditions will persist across portions of the Northern High Plains,
Central and Southeast U.S. - this vast area has Heat Advisories in place
from central Montana to central Georgia with pockets of Excessive Heat
Warnings over northeast Oklahoma, eastern Montana and north-central
Wyoming, as well as, Excessive Heat Watches over parts of Minnesota and
Iowa. 
Daily temperatures will rise into the upper 90s to low 100s. Several
regions have Air Quality Alerts due to Canadian wildfires and the
wildfires over the Northwest into the Northern Rockies. The hot and dry
airmass over the West has weakened the impact of the Southwest Monsoon but
there will be an uptick expected in the risk for excessive rainfall by
Friday. Showers and thunderstorms will continue over the Southwest,
Central/Southern Rockies, and Great Basin through Thursday, becoming more
diurnal. Marginal Risk areas are in effect through Thursday and a Slight
Risk is in effect for parts of Arizona on Friday.

A front extending from the Northeast, across the Great Lakes and into the
Northern High Plains will have multiple waves of low pressure traverse
through this boundary as it sags southward. This boundary will provide
focus for showers and thunderstorms to develop near it and some may become
severe. SPC has issued a Slight Risk of severe thunderstorms over parts of
the Upper Midwest and the Lower Great Lakes through Wednesday morning;
frequent lightning, strong wind gusts, hail, and minimal risk of tornadoes
are possible. This threat will translate to the Upper Great Lakes/Upper
Mississippi Valley on Thursday. Heavy rainfall and flash flooding will
also accompany these severe storms. WPC has a Slight Risk for excessive
rainfall in effect.

Another front extending from the Mid-Atlantic region across the
Ohio/Tennessee Valleys into the Northern Plains will begin to weaken.
Tropical moisture will pool over the Southeast, Lower Mississippi Valley
and the Southern Plains and will aid in the development of showers and
thunderstorms as pulses of energy pass through in the mid/upper
atmosphere. Periods of heavy rain are expected and may lead to an increase
risk for flash flooding.

Campbell

Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php