Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
247 AM EST Tue Jan 9 2024

Valid 12Z Tue Jan 9 2024 - 12Z Thu Jan 11 2024

...Major storm system will hammer the Eastern U.S. with widespread heavy
rain, strong winds, and severe thunderstorms on Tuesday into early
Wednesday...

...Unsettled weather conditions continue for the Western U.S. with much
colder temperatures arriving for the Northern Plains...

A very potent mid-upper level trough over the Central U.S. is becoming
negatively tilted and this is allowing for rapid surface cyclogenesis over
the Midwest and Ohio Valley on Tuesday.  The result will likely be a
sub-980 mb surface low over Michigan by late Tuesday evening/night, and
this low will continue lifting toward the northeast across southern
Ontario and into Quebec by Wednesday afternoon.  A strong cold front
trailing south from the parent low will exit the East Coast overnight
Tuesday across the Mid-Atlantic and into early Wednesday morning for the
Northeast U.S.

Widespread hazardous weather impacts are expected for the eastern third of
the U.S. in association with this low pressure system, and numerous
warnings and advisories are now in effect from the local NWS forecast
offices.  One of the big things making weather headlines will be the
widespread expanse of heavy rain capable of producing flooding from the
Florida Panhandle all the way north to southern Maine.  There is a
Moderate Risk of excessive rainfall now highlighted by the Weather
Prediction Center for the Tuesday-Tuesday night time period from northern
Virginia to southern New England, where the combination of 1 to 3 inch
rainfall totals over highly saturated, and in some cases snow covered
ground, along with swollen creeks and streams, will elevate the potential
for flooding across this region.  Another major issue that is quite
concerning is the powerful 850 mb low level jet that will be in place just
ahead of the cold front as it approaches the East Coast, with southerly
winds 75 to 100 mph just a few thousand feet above the surface.  At the
surface, this will likely result in widespread 30-50 mph winds, especially
near the coast and for elevated areas where gusts will likely exceed 50
mph.  Inland areas that have more of a surface temperature inversion will
get less of this wind energy from aloft mixing down, but still breezy
nonetheless.  Therefore, high wind warnings are in effect for many areas
near the coast and storm warnings for the open waters, and power outages
are a real possibility.  This will also cause instances of coastal
flooding where strong onshore flow piles up water into rivers and bays. 
Severe thunderstorms are also expected from northern Florida to the
coastal plain of the Carolinas, where a favorable combination of
kinematics and instability will fuel intense storms capable of producing
damaging winds and tornadoes.

Conditions should slowly improve going into Wednesday in the wake of this
intense storm system across the Eastern U.S., although it will still be
rather breezy with west to northwesterly flow, and snow showers for the
western Great Lakes and the eastern Ohio Valley.  A weaker low pressure
system approaches the Upper Midwest and Great Lakes region on Wednesday
into Thursday morning, but it will not have much moisture to work with, so
mainly light snow is expected with that event.

For the Western U.S., the weather pattern will also be active with a
strong Pacific front moving inland with very heavy snow for the Cascades
and then across the Northern Rockies with snow levels dropping over time. 
By Wednesday night, a second disturbance moves inland across the Desert
Southwest and this brings valley rain and mountain snow across Arizona and
New Mexico.  Meanwhile, an arctic front drops southward from Canada on
Wednesday and this will herald the arrival of the coldest temperatures so
far this season for the Northern Plains, with subzero lows becoming a
reality for Montana and North Dakota, and this cold airmass will continue
settling southward through the end of the week.  The combination of this
front and the storm system from the southwestern U.S. will eventually
result in a much larger low pressure system developing over the Southern
Plains by the end of the week.

Hamrick



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