Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
352 AM EDT Wed Sep 01 2021

Valid 12Z Wed Sep 01 2021 - 12Z Fri Sep 03 2021

...Tropical Depression IDA is forecast to slowly weaken while moving
northeastward with a High Risk of excessive rainfall from the northern
Mid-Atlantic/Northeast through Thursday morning...

...There is an Enhanced Risk of severe thunderstorms over parts of the
Mid-Atlantic through Thursday morning...

...The Sight Risk of excessive rainfall over the Southwest into the
Central/Southern Rockies as former T. C. NORAâ€S moisture moves over the
region through Thursday morning...

...There is a Slight Risk of severe thunderstorms over parts of the
Northern/Central Plains through Thursday morning...

Tropical Depression IDA is forecast to slowly weaken and become a
Post-Tropical Cyclone by Thursday morning while moving northeastward. 
What was IDA will move off the Northeast Coast also on Thursday morning. 
However, IDA will continue to produce heavy rain along the path into
Thursday.  Therefore, the WPC has issued a High Risk of excessive rainfall
from the northern Mid-Atlantic/Northeast through Thursday morning. The
associated heavy rain will create widespread areas of flash flooding.
Furthermore, severe, widespread flash flooding is expected with IDA. Areas
that normally do not experience flash flooding will flood. Lives and
property are in great danger through Thursday morning from the northern
Mid-Atlantic/Northeast.

Furthermore, the SPC has issued an Enhanced Risk of severe thunderstorms
over parts of the Mid-Atlantic through Thursday morning.  The hazards
associated with these thunderstorms are frequent lightning, severe
thunderstorm wind gusts, hail, and a few tornadoes.  What was IDA will
move from the Mid-Atlantic into New England by Thursday morning then move
into the Canadian Maritime Provinces by Friday.  IDA will continue to
produce heavy rain until it leaves the U. S.

Meanwhile, a front extending from the Northern High Plains westward to the
Great Basin will move eastward into the Northern Plains overnight
Wednesday, producing showers and thunderstorms. As a result, the SPC has
issued a Slight Risk of severe thunderstorms over parts of the
Northern/Central Plains through Thursday morning.  The hazards associated
with these thunderstorms are frequent lightning, severe thunderstorm wind
gusts, hail, and a few tornadoes.  The severe thunderstorms threat will
decrease slightly on Friday into Saturday. 

Elsewhere, moisture associated with what was once Tropical Cyclone NORA
will move over the Southwest into parts of the Great Basin and
Central/Southern Rockies on Wednesday into Thursday, producing
thunderstorms. Therefore, the WPC has issued a Slight Risk of excessive
rainfall with these thunderstorms. The associated heavy rain will create
mainly localized areas of flash flooding, with urban areas, roads, and
small streams the most vulnerable through Thursday morning.  Additionally,
there is a fire weather threat over Northern/Central California as Red
Flag Warnings have been issued in these areas. Air Quality Alerts have
also been published over much of the Pacific Northwest and California and
parts of Wyoming and Colorado due to wildfire smoke.  There are also Heat
Advisories out for parts of the Southern Plains and the Lower Mississippi
Valley.

Ziegenfelder