Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
245 PM EST Wed Mar 08 2023

Valid 00Z Thu Mar 09 2023 - 00Z Sat Mar 11 2023

...Multiple day heavy rain and flash flood threat continues across the
Central Plains and Lower Mississippi Valley...

...Threat of heavy rain, flooding, and heavy high-elevation snow will
increase for the West as an Atmospheric River impacts the region
Thursday...

...Moderate to locally heavy snowfall accumulations will spread across the
Northern/Central Plains late Wednesday into the Upper Midwest Thursday...

A multi-day heavy rain and flash flood threat is expected to continue over
portions of the Southern Plains and Lower Mississippi Valley Wednesday and
Thursday after an initial round of heavy rain late Tuesday night. A
quasi-stationary surface boundary sits beneath southwesterly flow aloft
with ample moisture flowing in from both the Gulf of Mexico and an
additional stream sourced from the Pacific. Following the initial round of
storms moving through Oklahoma and Arkansas expected to weaken through
Wednesday morning, a shortwave passing over the region will help to
trigger another round of thunderstorms late Wednesday before a cold front
helps to initiate a final round late Thursday. Slight Risks (level 2/4) of
Excessive Rainfall have been issued for both Wednesday and Thursday from
southern Oklahoma/northern Texas into southern Arkansas for the chance of
locally heavy rainfall rates/totals and some scattered instances of flash
flooding.  There will be quite a stark contrast in temperatures north and
south of this stationary boundary, with highs generally in the upper 70s
and 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
Plains and Middle-Mississippi Valley. Temperatures in the Southern High
Plains appear more likely to recover a bit Wednesday into Thursday as the
boundary lifts northward, with highs in the 50s warming into the 70s.

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 storm system lingering 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 before an even more impactful Atmospheric River
approaches Thursday. 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. Forecast precipitation markedly
increases on Thursday with the arrival of the Atmospheric River, raising
snow levels and bringing the threat for heavy rainfall and flooding to
portions of central coastal California and the central interior valleys.
There is a Moderate Risk (level 3/4) of Excessive Rainfall as the threat
of several inches of heavy rain into high-terrain favorable regions given
increased snow levels as well as the additional impacts of snow melt will
increase the risk of flooding. At higher elevations in the mountains, 12"+
of snow will be possible for portions of the Cascades and Sierra, with
additional heavy snowfall also forecast for the Blue Mountains of Oregon
and Snake River Ranges in Idaho. Temperatures on Wednesday and Thursday
will be unseasonably cool over most of the West. High temperatures will be
in the 20s and 30s for the Northern/Central Rockies, 30s and 40s for the
Great Basin, 40s for the Pacific Northwest, and 50s for much of
California. 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.

Light snow showers over the Northern Plains/Upper Midwest and a wintry
mix/rain for the Central Plains will linger through the day Wednesday
before a more potent shortwave approaches from the west, helping to better
organize the frontal system currently over the Plains and increase
precipitation chances overall. The chances for locally heavier snow of 6"+
are highest for the western Dakotas late Wednesday night and into the day
Thursday, and for portions of the Upper Midwest on Thursday. Some gusty
winds may lead to a few areas of blowing snow and difficult travel
conditions. Further east, some light snow showers will be possible for the
Interior Northeast, but otherwise conditions will be mostly dry for the
East Coast through Thursday. Highs will generally be seasonable with
temperatures in the 30s and 40s for New England/the northern Mid-Atlantic,
50s and 60s for the southern Mid-Atlantic and the Carolinas, and 60s and
70s for the Southeast and Florida. Morning lows will be a bit chilly, at
or below freezing, from the Carolinas northward, and some blustery winds
may make for some cold wind chills Thursday morning. The system over the
Midwest will begin to push towards the Appalachians/East Coast late
Thursday night/early Friday morning, increasing precipitation chances
towards the end of the current forecast period.

Putnam

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