Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
317 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 will develop across the
Central Plains and Middle-Mississippi Valley...

...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 and Midwest through
mid-week...

A multi-day heavy rain and flash flood threat is expected to develop over
portions of the Southern Plains on Tuesday night and expand further
eastward into the Lower Mississippi and Tennessee Valleys Wednesday. A
quasi-stationary surface boundary sits beneath southwesterly flow aloft as
moisture increases from both the Gulf of Mexico as well as a stream
sourced from the Pacific. These sources will combine to trigger the
development of multiple rounds of nighttime thunderstorms beginning
Tuesday night over Oklahoma. A Slight Risk (level 2/4) of Excessive
Rainfall is in effect on Tuesday as anomalously high moisture content will
contribute to rain rates of 1"+ per hour. In addition, 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", with 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
concern for more numerous instances of flooding given the high antecedent
soil moisture and therefore the issuance of a Slight Risk (level 2/4) of
Excessive Rainfall on Wednesday. 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, further
expanding the flash flood threat eastward. There will be quite a stark
contrast in temperatures north and south of this stationary 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 across the West and Plains will be a bit
more unsettled and cooler than the East as this winter's dominant pattern
of upper-level troughing over the West with downstream ridging to the east
continues. 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 snowfall
totals of several feet. Some thunderstorms will be possible along the
coast, and some 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 on Tuesday and Wednesday
will be unseasonably cool over most of the West. High temperatures will be
in the 20s and 30s for the Northern/Central Rockies and Great Basin, 40s
for the Pacific Northwest, and 50s for much of California. Some locations
over California and the Great Basin may meet or exceed record low maximum
temperatures on Wednesday. Portions of the Southwest and Southern Rockies
will be the one warm spot for the West, with highs forecast to be above
average 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 is currently impacting
portions of the northern Plains, where several inches of snow has already
fallen. Another, more intense round of snow will begin Wednesday afternoon
and continue into Thursday for portions of the Northern and Central Plains
as a more significant shortwave moves out from the Intermountain West.
Rain showers and a wintry mix will be possible further south into the
Central Plains. This system will move into the Upper Midwest by Thursday
evening, with significant snowfall totals possible through Thursday
evening. 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 temperatures maximizing
30s and 40s over much of the region. 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. Some highs across the Southeast may be close
to breaking the daily record. A cold frontal passage will cool most
locations back to more seasonable conditions Wednesday except along the
immediate Gulf coast and into southern Florida, where temperatures in the
80s will persist.

Putnam/Genz

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