Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Wed Jul 28 2021

Valid 12Z Wed Jul 28 2021 - 12Z Fri Jul 30 2021

...There is a Moderate Risk of severe thunderstorms over parts of the
Upper Mississippi Valley, Upper Great Lakes, and parts of the Ohio Valley
through Thursday morning...

...There is a Slight Risk of excessive rainfall over parts of the Upper
Mississippi Valley/Upper Great Lakes through Thursday morning...

...There is a Slight Risk of excessive rainfall over parts of the
Southwest Thursday into Friday morning...

...Heat Advisory over parts of the Mississippi Valley and the Plains;
Excessive Heat Warning over parts of the Northwest...

A front extending from the northern Mid-Atlantic across the Ohio Valley
into the Upper Midwest will have a wave of low pressure traveling along
the boundary through Thursday. As a result, showers and thunderstorms will
develop along and near the boundary through Thursday evening. Some of
these thunderstorms will become severe with more robust dynamics. 
Therefore, the SPC has issued a Moderate Risk of severe thunderstorms over
parts of Upper Great Lakes through Thursday morning.  The hazards
associated with these thunderstorms are frequent lightning, severe
thunderstorm wind gusts, hail, and a few tornadoes. There is a 10% or
greater probability of wind gust of 65 knots or greater and a 10% or
greater probability of two-inch or great hail over parts of the Upper
Mississippi Valley/Upper Great Lakes through Thursday morning. 
Furthermore, there is a 10% or greater probability of EF2-EF5 over parts
of the Upper Mississippi Valley/Upper Great Lakes through Thursday morning.

Additionally, the thunderstorms will produce heavy rain.  Therefore, the
WPC has issued a Slight Risk of excessive rainfall with these
thunderstorms over parts of the Upper Mississippi Valley, Upper Great
Lakes, and parts of the Ohio Valley through Thursday morning.  The
associated heavy rain will create mainly localized areas of flash
flooding, with urban areas, roads, and small streams the most vulnerable.

Showers and thunderstorms will continue along and near the boundary
through Friday. The severe thunderstorm threat shifts to the Ohio Valley,
Mid-Atlantic, Central Appalachians, and Northeast Thursday into Friday
morning.  The excessive rainfall threat decreases slightly on Thursday
into Friday morning.

Meanwhile, showers and thunderstorms will continue over the Southwest,
Central/Southern Rockies, and Great Basin today, though the excessive
rainfall threat will be lower. However, the monsoonal moisture streams
back into the Southwest as strong upper-level energy passes over the
region Thursday into Friday. Therefore, the WPC has issued a Slight Risk
of excessive rainfall over the Southwest on Thursday into Friday morning.
The associated heavy rain will create mainly localized areas of flash
flooding, with urban areas, roads, and small streams the most vulnerable.

Over the Northwest, there is an Excessive Heat Warning over parts of the
area, where temperatures will be above average. Furthermore, Heat
Advisories are currently in effect for portions of the Mississippi Valley
and the Plains where the temperatures will be 10 to 20 degrees above
average.  Moreover, several regions have Air Quality Alerts due to
wildfires over the Northwest into the Northern Rockies.

Ziegenfelder



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