Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
253 PM EST Tue Mar 07 2023

Valid 00Z Wed Mar 08 2023 - 00Z Fri Mar 10 2023

...Multiple day heavy rain and flash flood threat to begin Tuesday night
over Oklahoma, extending eastward into the Mississippi Valley Wednesday...

...Unsettled conditions across parts of the West will continue through
mid-week with coastal rain and locally heavy snow in California...

...A couple rounds of moderate to locally heavy snowfall accumulations
likely for portions of the Northern/Central Plains through mid-week...

A multi-day heavy rain and flash flood threat is expected to develop over
portions of the Southern Plains Tuesday night and expand further eastward
into the Lower Mississippi and Tennessee Valleys Wednesday. A
quasi-stationary surface boundary beneath southwesterly flow aloft as
moisture increases from both the Gulf of Mexico as well as a stream
sourced from the Pacific will combine to trigger the development of
multiple rounds of nightly thunderstorms beginning Tuesday night over
Oklahoma. There is a Slight Risk (level 2/4) of Excessive Rainfall as
anomalously high moisture leading to rain rates upwards of 1"+ per hour as
well as the tendency for storms to back-build over the same regions given
generally unidirectional southwesterly flow aloft will lead to the risk of
locally heavy rainfall totals of 2-4" and the potential for scattered
instances of flash flooding. Another round of storms is expected to
develop late Wednesday night in the same general vicinity over Oklahoma
and Arkansas, leading to a greater concern for more numerous instances of
flooding given the prior day's rainfall and therefore the issuance of a
Moderate Risk (level 3/4) of Excessive Rainfall. The expectation is that
more of these storms will progress further downstream into the Lower
Mississippi and Tennessee Valleys late Wednesday night/early Thursday
morning, expanding the flash flood threat. There will be quite a stark
contrast in temperatures north and south of this boundary, with highs
generally in the 80s to the south over Texas and the Lower Mississippi
Valley, with even some low to mid-90s possible along the Rio Grande. On
the other hand, highs will be in the 40s and 50s to the north over
portions of the Central/Southern High Plains, Central Plains, and
Middle-Mississippi Valley.

On a broader scale, conditions will be a bit more unsettled and cooler
over the West and the Plains compared to the East as upper-level troughing
remains in place to the west with downstream ridging to the east. A
persistent series of lows off the northwest Pacific coast and upper-level
energy rotating around the trough in place will help to encourage nearly
continuous lower elevation valley/coastal rain and higher elevation
mountain snow chances for the Pacific Northwest and northern California.
Heavy snow is forecast for the northern coastal ranges and Sierra in
California Tuesday where higher elevations may see totals well over a
foot. Some thunderstorms will be possible along the coast, and light snow
may mix in for valley locations especially Wednesday night along the I-5
urban corridor of the Northwest. Additional snow showers are possible for
the Northern/Central Rockies Wednesday as a lingering surface boundary
remains draped across the region and the upper-level energy passes
through. Temperatures Tuesday and Wednesday will be unseasonably cool over
most of the West. Highs will be in the 20s and 30s for the
Northern/Central Rockies and Great Basin, 40s for the Pacific Northwest,
and 50s for California. Some of these highs in portions of the northern
Great Basin into central/northern  California are at or at least close to
record high minimums for the date. Portions of the Southwest and Southern
Rockies will be the one warm spot for the West, with highs in the 60s and
70s.

A couple waves of energy rotating around the western trough will also lead
to rounds of moderate to locally heavy snow across portions of the
Northern and Central Plains. The first round will continue through the day
Tuesday across portions of the Dakotas, where 3-6", locally higher, will
be possible through the evening. Another round will begin later Wednesday
and continue into Thursday for portions of the Northern and Central Plains
as a more significant shortwave moves out from the West. Rain showers and
a wintry mix will be possible further south into the Central Plains.
Further east, some light snow showers will be possible for the Interior
Northeast, but otherwise conditions will be mostly dry for the Midwest and
East Coast. High temperatures will generally be seasonable for New England
and the northern Mid-Atlantic, with 30s and 40s forecast. Highs will be
closer to early Spring for the southern Mid-Atlantic and Carolinas Tuesday
with 60s and 70s forecast, and more late-Spring like closer to the Gulf
Coast and Florida with low to mid-80s forecast. A number of these highs in
the Southeast will be close to record-tying/breaking levels. A cold front
passing through will cool most locations back to more seasonable
conditions Wednesday except along the immediate Gulf coast and into
southern Florida where 80s will persist.

Putnam

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