Scientific Forecaster Discussion
fxus61 kctp 190506
Area forecast discussion
National Weather Service State College PA
1206 am EST sun Nov 19 2017
a storm near Erie this evening will race through the eastern
Great Lakes tonight and up into eastern Canada Sunday. A strong
cold front trailing south from this low will plow east across
the commonwealth overnight. Colder air with strong, gusty west
to northwest winds, and some lake effect snow will then affect
the area Sunday. Conditions will gradually improve into Monday.
High pressure will bring moderating temperatures and dry
conditions Tuesday through at least Friday.
Near term /until 6 am this morning/...
as of 10pm, the sub 990mb low is just about on top of Erie
heading north-northeast down the St. Lawrence River valley. Radar still
shows waves of moderate to heavy rain racing northeast across
the area, but the rain is looking more disorganized as we see the
nose of the low level warm air move into the region and the
overall warm advection begin to weaken.
The warm air has broken into Somerset County where the
temperatures have risen into the mid 50s, but the cool air
damming wedge remains well entrenched over most of the remainder
of the area. Temperatures over the Ridge-Valley region will
generally continue to rise overnight as the warm air creeps
north and tries to erode the dense cool air in place. The usual
scenario under these setups is for the actual warm front to
creep into southern areas as the cold front moves toward the
region, but rather than pass through most of the County Warning Area cleanly,
it will tend to mix out briefly just ahead of the cold front,
leading to a brief spike in temperatures just before colder air
comes pouring in on a strengthening northwest wind. That will tend to
happen from midnight into the wee hours of Sunday. By the time
we wake up Sunday morning, it will be turning colder and the
wind will be strong and gusty out of the northwest under potent cold
The rap and hrrr agree, the front will enter our western
counties around midnight, and should be clearing the eastern
part of the County Warning Area by around sunrise.
Expect a sharp drop in temps after the frontal passage, and a
quick increase in wind as an area of 7-9 mb/3hr sfc pressure
rises moves NE from the Ohio River valley to The Finger lakes
and Pocono region of nepa between midnight and mid morning
The Wind Advisory affects the entire County Warning Area with the exception of
the northwest where a Winter Weather Advisory for lake effect snows
includes the mention of the strong gusty winds.
Will continue to advertise a large area of 1-1.5 inch rainfall
amounts across the region of central PA and northern PA from
along the 22/322 corridors and points north, where models show a
stripe of enhanced quantitative precipitation forecast from the steepest ascent of the moist
and increasing unstable air over the persistent/nearly
stationary low level boundary.
Short term /6 am this morning through 6 PM Monday/...
a very windy and cold day is on tap for Sunday with frequent
gusts of 40 to 50 mph during the mid to late morning hours as
the area of strong 3-6 hourly pressure rises moves NE across the
Sref mean 850 mb temps of about -7c across the northwest and -4 to -5c
across the southeast support Max temps in the l-M 30s in vicinity of kbfd and
kjst and mid to upper 40s in vicinity of kmdt and klns with upper 30s to
low 40s throughout the central mtn zones.
Scattered to numerous snow showers will bring a coating to 2
inches of wind whipped snow accum across The Laurels and
northcentral mtns, while the northwest snowbelt receives 3-5 inches of
les. Southeast of the Allegheny Front, frequent flurries and a few
narrow, sinuous bands of snow showers/squalls could whiten the
ground quickly in some locations.
Some peeks of sunshine will mix in across the lower susq valley
at times, with some brief, mixed rain/snow showers.
Long term /Monday night through Saturday/...
the extended part of the forecast will see the season's first
real lake effect snow event winding down early in the period,
followed by several days of cool but tranquil weather.
Model soundings show the inversion heights falling quickly
Sunday evening through Monday morning, which will begin the
process of shutting off the lake effect machine. Look for
accumulating snow to continue overnight over the normal snowbelt
areas of the northwest and even down into The Laurels-with lesser
amounts. The snows will continue shrinking back closer to the
immediate vicinity of the lakes by Monday morning and by Monday
afternoon there should be little more than a few leftover
flurries as the high builds off to our south and we see the
thermal advection switch from cold to warm.
High pressure will keep conditions dry into Tuesday before a
weakening front sliding by to our north brings the small chance
of a snow shower to northern areas Tuesday night and Wednesday.
Another area of high pressure will build east and keep US mainly
dry at least through the end of the week, before a new frontal
system takes aim at the area.
Aviation /05z Sunday through Thursday/...
cold front now pushing through western Pennsylvania with a thin
line of moderate rain showers. This feature will cross the state
over the next few hours with increasing winds behind it.
Conditions will vary between MVFR and IFR until the frontal
Expect northwest wind gusts in the 30 kt range overnight into
Lake effect snow showers will affect kbfd with MVFR to IFR
conditions. Elsewhere, a broken layer along with turbulence over
Mon...am shsn/reduced vsbys possible northwest mountains.
Tue-Wed...no sig wx expected.
Wind Advisory from 4 am early this morning to noon EST today
Wind Advisory until noon EST today for paz010-011-017.
Wind Advisory until noon EST today for paz024-025-033-034.
Winter Weather Advisory from 4 am early this morning to 1 PM
EST Monday for paz004-005.