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FXUS61 KCTP 201953

Area Forecast Discussion
National Weather Service State College PA
353 PM EDT Tue Mar 20 2018

An early spring, long duration winter storm will bring heavy
snow to parts of south-central Pennsylvania through Wednesday. 
Dry weather with cooler than average temperatures is expected
Thursday and Friday.


Snow continues to slowly move north toward the I-80 corridor
this afternoon, with plenty of dry air (single digit dewpoints)
still in place over north-central PA. Some sleet is mixing in
across the far southeast zones. Snow intensity should decrease 
into this evening and overnight hours in south central PA, but 
nightfall will offer a better environment for accum on roads 
even at lighter rates and marginal temperatures. We continued to
refine the storm total snowfall, incorporating recent reports of
3-6"+ reports along the southern tier counties/higher elevations.
Still expect a very sharp gradient near I-80 with hires models 
showing little (<1") to no accumulation north of I-80. 


The 12z HREF shows the period of lighter snow overnight very
well before ramping snow intensity up again Wednesday morning
into the afternoon, with accum rates ~1 in/hr shifting from 
south central to southeast PA into the afternoon. Minor 
adjustments (slight increase) were made to snowfall on Day 2. 
Snow will taper off Wednesday evening in the lower Susquehanna 
Valley before ending Wednesday night. By the time the early 
spring/late March storm is over, some locations along and south
of Rt22/I-81 will see around 1 foot of snow. 


By Thursday...the storm will continue to slowly lift away from 
our area. An upper level low will drop southeast late Thursday 
into Friday. This will likely bring more clouds back into the 
area...with a chance of some snow showers, and keep temperatures
on the cooler side.

A complex pattern for the upcoming weekend into early next 
week will prevail. Central PA will likely be between a 
developing storm off the coast...and on the edge of warm 
advection from the central plains. Thus much of the time it 
should be dry, but remain cool in low level northeasterly flow.
By Sunday night into Monday, another upper wave slides through
with ridging and cool surface high building in behind.


VFR conditions persist over northern half of CWA as dry air
continues to fend off precip approaching from the south. Areas
north of I-80 should remain VFR through the TAF period.

Snow/areas of mixed precipitation impacting southern half of CWA
this afternoon with widespread restrictions. Precip intensity
should lighten for several hours this evening before picking up
again late tonight into Wednesday with another period of
moderate to heavy snow likely, especially across SE portions.
Restrictions will continue, with widespread IFR esp along and
south of the PA Turnpike, until conditions begin to improve from
the north late Wed into Wed eve. 

LLWS becomes likely over the south late tonight into Wed as
850mb jet increases to 30-40 kts as it rotates from the east to
the northeast. 


Tonight and Wed...Snow and restrictions continue southern half. 
Some improvement later on Wed.

Thu...No sig wx expected.

Fri...Cig restrictions poss NW. 

Sat-Sun...No sig wx expected.


The Spring (Vernal) Equinox will be at 12:15 PM today, March 
20. Sunrise in State College, PA will be 7:14 AM and sunset at 
7:23 PM, for a total day length of just over 12 hours.

While it will be spring on the calender today...a look outside
will be more like winter. We may have to wait until late in the
month to see a touch of spring-like temperatures.


Winter Weather Advisory until 8 PM EDT Wednesday for 
Winter Storm Warning until 8 PM EDT Wednesday for PAZ024>028-



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