Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Fri Nov 12 2021

Valid 12Z Fri Nov 12 2021 - 12Z Sun Nov 14 2021

...Snow and high winds over the northern Plains/upper Midwest gradually
subside today as locally heavy rain and strong thunderstorms move across
the Northeast and Mid-Atlantic...

...Flash flooding potential to continue over the Pacific Northwest into
early Saturday as onslaught of heavy rainfall continues...

...An Alberta clipper will deliver another around of snow/rain and gusty
winds across the northern Plains Saturday into early Sunday...

A large and energetic low pressure system that has brought snow and high
winds across the northern Plains and upper Midwest will steadily weaken
today as it moves across the Great Lakes and retreats into Canada tonight.
 Nevertheless, very strong and gusty winds on the back side of this system
will initially bring blowing snow and reduced visibility over portions of
the northern Plains early this morning before conditions steadily improve
later today.  In the mean time, a strong cold front associated with this
energetic system will sweep through the eastern U.S. today with locally
heavy rain and embedded strong thunderstorms.  These storms may lead to
local flooding issues later today across New England.

Shifting focus out west, persistent onshore flow from a modest atmospheric
river will continue to bring moderate to heavy rainfall into portions of
the Pacific Northwest.  Another 2-4 inches of rain have been forecast for
the region over the next 24 hours and rainfall rates over some areas may
be as high as 0.5-0.75 inches per hour.  Given the already saturated soils
from the previous days' rain and the concern for the development of rapid
run-off and urban flooding, the Weather Prediction Center has issued a
Slight Risk of Excessive Rainfall for portions of the Pacific Northwest
through Friday morning.  The threat of heavy rain is forecast to diminish
later tonight as the main energy penetrates further inland to support a
anew low pressure center over Albert Canada.

In the Central/Southern Plains, dry and breezy conditions coinciding with
low values of relative humidity has prompted the issuance of an Elevated
Risk of fire weather by the Storm Prediction Center through Saturday
morning, as these conditions could allow any fires that ignite to spread
rapidly.

Temperature-wise, daily highs across much of the country are forecast to
sit near or moderately (within 10 degrees) above normal. However, for
those areas that find themselves to the west/southwest of the occluded low
pressure system the opposite holds true. Significant cold air advection
behind the system, aided by the cut off low aloft, will force temperatures
to drop well below normal behind a cold front set to develop across the
central US this evening. On Friday the Central Plains and Middle
Mississippi Valley will be hit the hardest as highs are expected to fall
into the 30s and 40s, around 10 to 15 degrees below normal. As the Plains
warm up on Saturday with the advancement of a warm front through the
region, cooler temperatures are expected to settle into the Tennessee and
Ohio Valleys with the eastward progression of the cold front. With
temperatures sitting 10 to 20 degrees below normal, daily highs in these
areas will be unable to escape the 40s and 50s.

Kong/Zavadoff


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