Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Tue Aug 31 2021

Valid 00Z Wed Sep 01 2021 - 00Z Fri Sep 03 2021

...Widespread heavy rain, with areas of considerable to significant and
potentially life-threatening flash flooding, is expected from the
Tennessee Valley through the Upper Ohio Valley, Central Appalachians,
Mid-Atlantic, and southern New England in association with T.D. Ida...

...Tropical moisture from the remnants of Nora will bring heavy rain and
widespread concerns for flash flooding, some of it possibly significant,
to the Southwest U.S. over the next couple of days...

...Windy conditions and dry weather will continue to pose a fire weather
threat to areas of northern California and the northern Great Basin going
through Wednesday...

Tropical Depression Ida is forecast to advance northeast this evening and
overnight across the Tennessee Valley, and then cross the central
Appalachians and Mid-Atlantic states on Wednesday. By Wednesday night the
system will merge with a frontal zone and become a
post-tropical/extratropical cyclone and move just south of Long Island and
then away from New England on Thursday. Very heavy rainfall is expected
along and just north of the path of Ida going through the period, and the
expectation is for as much 3 to 8 inches of rain with isolated heavier
amounts. This rainfall may lead to areas of considerable to significant
and life-threatening flash flooding. In fact, the Weather Prediction
Center has highlighted areas of northern West Virginia, western Maryland,
southern Pennsylvania, and New Jersey in a High Risk of excessive
rainfall. Widespread moderate to isolated major river flooding impacts are
forecast across these same areas.

In addition to the flooding and flash flooding risks, Ida is expected to
bring a threat of severe weather to the Mid-Atlantic states on Wednesday,
and the Storm Prediction Center has highlighted this area in an Enhanced
Risk with damaging winds and tornadoes the dominant concerns. This will
mainly be focused along and the south of Ida's track.

Meanwhile, an upper-level trough advancing east out across the northern
Plains coupled with a frontal zone will set the stage for broken areas of
showers and thunderstorms, some locally severe, out across the northern
and central Plains, and the Midwest, going through Wednesday and Thursday.
The Storm Prediction Center does indicate a Slight Risk for severe weather
over the northern Plains on Wednesday with damaging winds and large hail
the main concerns.

Elsewhere, tropical moisture associated with the remnants of Nora will
move over the Southwest and adjacent areas of the Great Basin and Central
Rockies through Wednesday and Thursday. Widespread shower and thunderstorm
activity is expected. This will drive a widespread threat of flash
flooding, some of which may be significant. As a result, the Weather
Prediction Center has highlighted a Slight to Moderate Risk of excessive
rainfall, with an emphasis on southern Arizona. Any burn scars, dry
washes, and slot-canyons will be most sensitive to enhanced runoff
concerns.

There is also a fire weather threat to parts of the West, with an emphasis
on northern California and Nevada going through Wednesday. Red Flag
Warnings and air quality alerts have been issued accordingly, and
especially with areas of widespread smoke.

Orrison