Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
306 PM EST Thu Mar 09 2023

Valid 00Z Fri Mar 10 2023 - 00Z Sun Mar 12 2023

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

...Moderate to locally heavy snowfall accumulations will spread from the
Northern/Central Plains into the Great Lakes and Appalachians
Thursday-Friday...

...Shower and thunderstorm chances with locally heavy rainfall continue
for the Southern Plains and Lower Mississippi Valley Thursday;
precipitation chances increase for the East Coast Friday...

A persistent storm system lingering off the northwest Pacific coast will
better organize as upper-level energy approaches and moisture tapped deep
from the Pacific streams in, bringing yet another Atmospheric River event
to the West Coast in an already active winter season. Warming temperatures
will raise snow levels across much of the West, bringing the heavy rain
threat up into some portions of the higher terrain, including areas snow
on the surface. A Moderate Risk (level 3/4) of Excessive Rainfall is in
effect on Thursday over portions of central coastal California and the
interior central valleys. A High Risk (level 4/4) of Excessive Rainfall is
in effect on Friday over the same areas, particularly in favorable upslope
regions along the terrain of the coastal ranges and the Sierra, where
several inches of rain are expected. Because this system is overall warmer
than previous atmospheric rivers, rainfall at higher-elevations may
contribute to rapid snowmelt, which may further exacerbate the potential
for scattered to numerous flooding instances downstream. The threat for
flooding also extends to the east slope of the Sierra into the Great Basin
as well, given the warmer temperatures. Moderate to locally heavy rainfall
may also impact the Pacific Northwest, but without the flooding concerns
seen further south due to a lack of tropical moisture import.
Additionally, heavy snowfall will spread across higher mountain elevations
in the Cascades, Sierra, and interior ranges of the northern Great Basin
Thursday. This snow will then spread into portions of the northern/central
Rockies by Friday. Widespread snow totals of over a foot are likely, with
locally much higher totals of multiple feet possible, especially for
portions of the Sierra. Interior valley locations will likely see a mix of
rain and snow, keeping any snow accumulations low. Numerous and widespread
wind-related advisories are in effect for portions of northern and central
California and portions of the Great Basin due to wind gusts forecasted to
reach upwards of 40-50 mph at lower elevations and up to 70 mph at higher
elevations. Despite cool high temperatures on Thursday, Pacific air moving
in on Friday will cause temperatures to warm up going into the weekend,
with highs forecast to be in the 40s and 50s for the Pacific Northwest and
the Great Basin, and 50s and 60s for much of California. The Desert
Southwest and Southern Rockies will remain warmer than the rest of the
region, with most highs into the 60s and 70s, reaching into the low 80s
for some locations.

Further east, an upper level wave pushing across the Plains and into the
Midwest will aid the organization of an eastward moving frontal system and
continue to spread snow from the Northern/Central Plains into the Great
Lakes and into the central/northern Appalachians by Friday. The highest
chances for locally heavier snow of 6"+ will be over eastern Iowa into
southern Wisconsin on Thursday, and favorable lake-effect locations off
Lake Erie and into higher elevations of the central/northern Appalachians
in Pennsylvania into Friday. Snow rates may exceed an 1" per hour at
times, leading to difficult travel conditions. On Friday, the system over
the West will move into the Northern Plains, bringing renewed snow chances
to portions of Montana and the Dakotas through Saturday. Locally heavier
snowfall accumulations are possible near the Canadian border and into
northeastern North Dakota. High temperatures will generally be seasonable
across the Midwest, with 30s and 40s on Friday. High temperatures will
cool down from west to east over the weekend over the northern Plains,
with highs generally in the 20s and 30s on Saturday.

The chance for showers and thunderstorms will linger across much of the
southern tier of the country as a stagnant quasi-stationary surface
boundary remains in the region. Some locally heavy rainfall will be
possible across portions of eastern Texas and into the Lower Mississippi
Valley, though the flash flood risk is more marginal compared to previous
days. The incoming upper-level shortwave will help to finally push the
boundary southward as a cold front starting late Thursday night into this
weekend, pushing storm chances eastward through the lower Mississippi
Valley and into the Southeast on Friday and Saturday. Unseasonably warm
temperatures will come to an end across southern Texas and the Lower
Mississippi valley due to the cold frontal passage cooling temperatures
down to more seasonable temperatures Friday, with generally 60s for highs
outside of the immediate Gulf Coast and far South Texas. Precipitation
chances will also increase for the Mid-Atlantic and Carolinas due to the
approaching frontal system. Light to moderate rain showers can be expected
from Virginia south, while some snow may mix in to the north along the
I-95 urban corridor Friday night, though very little to no accumulations
are currently expected. Temperatures will generally cool going into the
weekend following the frontal passage. High temperatures on Friday will be
in the 30s and 40s for New England and 50s-60s in the Mid-Atlantic,
cooling down to the 40s and 50s for much of the East Coast on Saturday.

Putnam/Genz

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