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2024 Valentines Day Who the Hell Knows - Comeback Thread


DDweatherman
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NWS more concerned with flooding around the metro areas... 30-50% chance of an inch up by the PA line!

Text Products for AFD Issued by LWX (weather.gov)

Synoptically, we continue to monitor a strong 500 mb upper level low
pressure system that will eject out of the southern Plains early
Monday and into the Ohio/Tennessee River Valleys Monday afternoon
into Monday evening. Meanwhile, at the surface will watch the
progression of a cold front dropping south from Canada and New
England into the Mid-Atlantic Monday afternoon into Monday night.The
progression of this front south combined with the placement of high
pressure over central and eastern Canada will dictate how much cold
air makes it into the region especially as the upper level low
slides up the Mid-Atlantic coast late Monday night into Tuesday
afternoon.

Current deterministic and ensemble guidance continues to show subtle
differences in regards to the timing and intensity of the upper
level low as well as the progression of the front. The 12z NAM
remains the coldest solution while the GFS, GEM, GEFS, ICON, and
ECMWF have trended warmer over a large chunk of the forecast region.
This is particularly true in regards to the H85 0 degree isotherm
ballparked up around the PA Turnpike and I-80 region amongst most of
the guidance. Even with that said, several model solutions still
have the 0 degree C isotherm line in the vicinity of the PA/MD
border during the early Tuesday morning into Tuesday afternoon
timeframe as the upper level low/trough axis strengthens and swings
overhead. This will allow for a period of dynamical cooling for
precipitation to change from rain to snow.

Once again this will be determined by the surface low pressure
system track and transfer of upper level energy from the central
Appalachians toward the Mid-Atlantic coast. Plenty of uncertainty
remains here and still has yet to be ironed out amongst the models.

As of now, the highest confidence for impactful winter weather
remains in climo areas along and west of the Allegheny Front Monday
night into Tuesday. Areas further east of the mountains (especially
the Catoctin Mountains and areas along the immediate PA/MD border)
may see a brief period of rain changing to snow due to dynamical
cooling from the trough axis swinging overhead Tuesday morning into
Tuesday afternoon. Ensemble/NBM probabilities continue to show
probabilities of 2 to 4 inches of snow hovering between 30-50
percent for areas along and west of the Allegheny Front with 30-50
percent probabilities of 1 inch of snow along the PA/MD border
including the Catoctin Mountains. Higher snow amounts greater than 4
inches can be found across central PA and northern NJ where
deterministic/ensemble guidance continues to illustrate the best
frontogenetic forcing setting up. Any changes in the track of the
system (further south), strength, and timing of the H85 cold front
could play big dividends in where the best forcing/highest impact
from wintry weather sets up. For now, the current forecast favors
snow over the mountains of the Allegheny Front/Catoctins and
rain elsewhere across the region. More on snow totals at
weather.gov/lwx/winter.

Outside of the wintry threat the bigger concern may be flooding
given saturated soils, elevated streamflows, and heavy rainfall
within a short period of time (6-9 hour window). Rainfall amounts
will remain between a 0.5 to 1.50 inches with this system with
locally heavier amounts along and east of I-95.

High temperatures for most Monday will push into the mid to upper
40s with increasing easterly flow. Lows Monday night will fall into
the 20s over the mountains with low to mid 30s across the
rest of region.

Low pressure quickly intensifies and pulls away from the region
Tuesday afternoon and evening. This will lead to falling
temperatures as gusty northwest flow ushers in cold Canadian air.
Highs will will push into the upper 30s and low to mid 40s outside
of the mountains. Conditions will dry out east of the mountains with
low level moisture allowing upslope snow showers to continue along
and west of the Allegheny Front. These snow showers will diminish
Tuesday night into Wednesday as brief Canadian high pressure settles
in. Another shortwave and clipper-type low pressure system will
quickly follow within northwest flow Thursday into Friday. This
system will produce another shot of accumulating snow over the
mountains with the potential for a rain and snow mix further east.
It will also deliver another shot of cold Canadian air to the
region. Temperatures will remain 5 to 10 degrees below average by
the middle and latter half of next week.

 

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9 minutes ago, Stormchaserchuck1 said:

Nobody's into it, but we get some wrap around flurries Tuesday on the 0z NAM. Low pressure is really strong, 980s mb right when it exits the coast off of Ocean City. 

Not that it means much but it’s a little more than flurries for the northern areas. Maybe 1-2” in the favored spots.

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