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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 222335

Area Forecast Discussion
National Weather Service State College PA
735 PM EDT Fri Mar 22 2019

Windy and colder conditions with rain showers, snow showers, and
locally heavier squalls will follow behind a strong coastal
storm that brought heavy rain to the lower Susquehanna Valley. 
Improving weather is expected over the weekend with moderating 
temperatures. The next weather system is expected into early
next week, with some rain and snow showers. A return to dry
weather is expected on Tuesday, with a moderating trend in 
temperatures later in the week. Wet conditions could return to
the area by next weekend.


Rain and high elevation snow will end across the far eastern
part of the CWA early this morning. Small streams in the 
Juniata and Lower Main Stem Susquehanna River Basins have
responded to the rainfall with several points cresting above
caution stage. 

Focus shifts to changing weather expected over the next 24
hours. A strong shortwave will combine with strong March sun and
cold air aloft to produce gusty winds and convective rain/snow 
showers. Locally heavier squalls (possibly containing small hail
or graupel) are possible and could be accompanied by rumbles of
thunder. Issued wind advisory for part of south central PA 
where fcst soundings and hires guidance indicates potential for 
max winds gusts around 50 mph. The most likely timing for max
gusts would be later this afternoon into early tonight as 
subsidence region moves over the area in the wake of the 
vigorous shortwave. Frequent snow showers will likely bring a 
light snow accumulation and areas of slippery travel to the 
higher elevations of the western Alleghenies through tonight.


Snow showers should end early Saturday morning followed by 
gradually subsiding winds into Saturday night. High pressure 
will provide dry wx over the weekend with temperatures trending
warmer on Sunday.


Model guidance is in decent agreement with the next system 
returning light precipitation to the area late Sunday night into
Monday. I made a few adjustments to the temperatures. Looking at
some snow mixing with the rain at times late Sunday night into
Monday, especially across the north.

Dry weather is fcst from Monday night through late week. Temperatures
should trend colder behind the system Monday, given the source 
of the airmass. Minus 30 degree air at 850 mb over eastern 
Canada Sunday night is cold for late March.

Temperatures will rebound above average later in the week. I made
a few adjustments, but no big changes.

New EC (12Z) similar to the 00Z run of the EC and other models, 
as we head into late Friday into next weekend, that a system 
will lift northeast across the Great Lakes. This low will bring
mild air into the area, but also a tendency of the cold front 
to slow down with a ridge of high pressure over the southeast. 
This will result in some showers by Saturday. 

Overall, an active weather pattern for the lower 48.


A windy northwest flow continues across the entire region this
evening, with gusts frequently reaching 30 knots. Snow shower
activity beginning to wane across the region, especially noted
across the downslope regions of central and eastern portions of
the area.

KJST and KBFD, our typical airfields susceptible to a cold
unstable upslope flow continue to drift in and out of MVFR to
occasional IFR conditions. Even here, with loss of instability
overnight, expect snow showers to continue to decrease in
intensity overnight. Winds will remain brisk from the northwest
at 15 to 15 knots, with some gusts around 30.

VFR conditions across the region, but with the strong northwest
flow continuing. Indications are that the flow will begin to
relax late in the TAF period. Have included a 22z group
indicating the trend downward of the winds.


Sat...VFR, but brisk.

Sun...No sig wx expected.

Mon...Rain/snow/low cigs possible, mainly N and W Mtns. 

Tue and Wed...No sig wx expected.


Strong northwesterly winds in the wake of cold front will
persist through Saturday. Relative humidities are forecast to 
drop to 30% or less Saturday and Sunday afternoon. However, 
in collaboration with fire weather partners, recent significant
rainfall and snow/rain showers today will keep fine fuel 
moisture above 10% through the weekend. Thus no flags are 
expected at this time.


We are monitoring a few Lower Main Stem tribs with Harper 
Tavern/Swatara Creek just at minor FS. Expect falling stages by
later today.


Wind Advisory until 5 AM EDT Saturday for PAZ024>028-033>036-


SYNOPSIS...La Corte/Gartner
NEAR TERM...La Corte/Gartner
SHORT TERM...Gartner/Steinbugl
LONG TERM...Martin