Scientific Forecaster Discussion
fxus61 kctp 161029
Area forecast discussion
National Weather Service State College PA
529 am EST Mon Jan 16 2017
high pressure will drift east and off the mid Atlantic coast
today. A warm frontal system will drift slowly northeast across
the region Tuesday, followed by a cold front pushing east through
the state Tuesday night and early Wednesday. High pressure will
move northeast from the Tennessee Valley and bring mainly dry
conditions with temperatures several degrees above normal.
Near term /until 6 PM this evening/...
1032 mb surface high pressure over southeastern PA will provide
the region with fair and dry weather through much of today.
A rather thick cirrostratus/altostratus layer streaming across
much of southern PA will hold temps up (in the 20s) down there,
while much thinner cirrus across most of central and nepa has
allowed temps to fall into the mid and upper teens in many
Clouds will steadily thicken-up/lower during the day today as the
crest of a flat upper level ridge moves NE across the Ohio River
valley and the mean 925-850mb flow backs to the west-southwest. This will
push a sharp gradient of increasingly higher Theta-east NE across
all of the County Warning Area (except for the northern tier the state) by 00z
There is a slight chance for some light rain or drizzle across the
SW part of the forecast area late this afternoon.
The cold temps early this morning, and thickening cloud cover
throughout the day will hold temps lower by a few to several deg
f compared to earlier forecasts and model guidance. Highs will be
mainly in the mid to upper 30s for the bulk of the forecast area,
while some cooler readings will be found across the mtns of
central and northern PA, and some higher readings across our far
Short term /6 PM this evening through 6 PM Tuesday/...
the stubborn trough/upper low over the West Coast will weaken and
lift across the Southern Plains into the Great Lakes region as a
pattern change begins.
A good portion of the upcoming week is shaping up to be mild and
showery (especially tuesday) as the bulk of Med range guidance
shows a ridge slowly retreating off the East Coast as remnants of
that West Coast low get picked up by the northern stream and track
across PA during the midweek.
A warm front will be advancing northeast over the area early
tonight, spreading a shield of thick altostratus and nimbostratus
across central PA. The strongest warm air advection is still indicated across
western PA toward the end of the day/this evening, where
scattered showers are possible.
Further south, an increasingly moist southeast flow at low
levels, will likely create some drizzle over the higher terrain of
A combination of the NAM and nbm were used to paint hourly and low
temps tonight. This greatly assisted in depicting the area where
light ice accretion is likely later tonight through the mid
morning hours Tuesday and the areal extent and duration of a
recently issued Freezing Rain Advisory.
Shield of mainly light rain overspreading the region from the SW
tonight will initially fall into very dry low level air. This will
allow temps to wet bulb down to the u20s and lower 30s over much
of central and northern PA changing the rain to mainly light
freezing rain between midnight and shortly after sunrise Tuesday.
For midday Tue into Tue night, deep southerly flow ahead of that
trough will bring a plume of anomalous precipitable waters over the region which
supports the idea of showery (periods of steady rain on tuesday)
and mild weather. As has been the case frequently lately, the GFS
brings the trough through faster than the European model (ecmwf). Followed close to
the nat'l blend of models vary high, 90-100 pops for Tuesday
surround on either side by mainly likely pops.
Long term /Tuesday night through Sunday/...
winds turn westerly behind the system by Wednesday morning as
flow turns more zonal, but with no real cold air in sight, temps
will remain on the mild side and above freezing during the Day.
Ridge re-establishes itself over the eastern U.S. For late in the
week, as mild SW flow persists over the Midwest. Guidance
suggests energy will dive south along the West Coast eventually
helping to strengthen the building upper ridge over the east.
We'll be on the eastern side of this, so subtle shortwaves sliding
into the Midwest will bring varying amounts of cloudiness to the
west (less in the east) with low end chances for light showers.
Aviation /12z Monday through Friday/...
VFR flying today with clouds thickening and cigs lowering through
the afternoon. Restrictions should develop around 16/00z with MVFR
to IFR conditions good bet tonight into Tuesday. Rain will spread
across the airspace late tonight through Tuesday with risk for
freezing rain mainly over the northern 1/2 of the airspace btwn
00-15z Tue. Plan to add rain/freezing rain groups with the 16/12z tafs.
Wed...MVFR/IFR west; MVFR central to VFR southeast. Rain showers
west ending Wed ngt.
Thu-Fri...no sig wx.
Freezing Rain Advisory from midnight tonight to 10 am EST
Tuesday for paz004>006-010>012-017>019-037-041-042-045-046-