Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1041 PM EDT Sat Mar 15 2014
an area of low pressure will track south of Pennsylvania Sunday
night and Monday. Temperatures will be below normals through middle-
week when another low pressure system will likely track west of
Near term /until 8 am Sunday morning/...
continually less cloud cover and no real/thick high clouds off to
our immediate west. Much of the night should be clear outside the
northern mts. Mins look great.
8 PM update...
clouds now confined north of 1-80 but higher clouds moving in from the
west. Winds showing hints of slacking off...but have kept the
gustiness through at least the first half of the overnight.
visual loop shows broken-overcast stratocu clouds over about the northwestern 2/3
of my forecast area...with scattered-broken clouds over the southeastern 1/3 or so.
Radar continues to show light returns over the north where at
bfd...they occasionally see snow bring the viz down to 2-4 miles.
High res hrr...operational NAM and GFS all dry the light activity
up over the next few hours...leaving little more than flurries
possible into the evening.
Expect gusts to continue as stronger winds aloft mix down. BUFKIT
soundings support gusts to 30kts over much of the area through late
afternoon. The gusty winds will add a noticeable chill to the
air...despite temperatures fairly close to average for middle March. Ens
mean 800 mb temperatures imply maximum temperatures from the m30s northwest mountains...to the l50s
across the lower susq Valley.
High pressure will bulge in from the Great Lakes
overnight...bringing a lowering inversion and a colder northerly
flow. Overnight lows will average some 5 to15 degree below normal.
Short term /8 am Sunday morning through 6 PM Sunday/...
high pressure with origins over the northwest territories will work southeast
across the Great Lakes later tonight and Sunday. Latest
guidance...with the lone exception of the 12z GFS keeps central PA
dry during the daylight hours of Sunday. The GFS just tickles the
far southern tier with what would be some light snow during the
last part of the afternoon.
Other than some increase in middle/high clouds...thinking is that the
chances for precipitation will remain low over the vast majority of the
Fading sunshine...combined with northerly flow/cold advection
should result in a very chilly Sunday. Gefs 925mb temperatures close to
2sd blw average should translate to maximum temperatures of only around 20f over
the northwest mountains...to perhaps the u30s in the valleys along the Maryland
Long term /Sunday night through Saturday/...
1030 PM update...
newest NAM supports just a few hundreths making it north of the
Mason-Dixon line Sunday night/early Monday. Wave keeps on truckin.
However...most models do bring a tenth or more up to the
Turnpike/rte 22. So will make no changes - especially no issuance of any
advisory at this point.
8 PM update...
light-moderate snowfall for the southern tier looking more solid...but
forecaster confidence in an advisory snowfall not at 80pct quite
yet...so no advisory just yet. Will likely leave this go for the middle
shift. Plenty of more data will be available to them.
operational model and last few versions of sref and GFS ensemble
guidance has greatly converged on a solution for a much more
suppressed/non-phased southern stream wave to cross the lower miss
valley and southeastern U.S. Sunday into Monday. This storm path will leave
at least the northern half of Penn high and dry...with generally light
accums of snow limited to far southern Penn.
12z GFS is a slight northern outlier /compared to the 12z NAM and
12z ec/...creating the potential for several inches of snow over the
southern 2 layers of PA counties. Made only minor southward
modifications to snow probs and accums based on the last few runs of
oper and ens guidance.
The approx 1024 mb surface high suppressing this storm system will move
from the upper glakes to northern New York by Monday. As this high slides
over the New England states Tuesday into Wednesday...southeasterly low level
flow developing ahead of an approaching warm front will bring
increasing layer clouds and a chance for a light icy mix or a bit of
snow early Wednesday.
Isolated-scattered showers will be possible along and ahead of a
weak cold front Wednesday afternoon and night...while rain showers
mix with scattered snow showers across the Laurel Highlands and northwest
mountains Wednesday night into Thursday.
The middle to late week period will feature a transition to mainly
zonal flow aloft...which will transport air of northern Pacific origin
quickly east...giving US temperatures near to slightly above normal for
A more potent northern stream shortwave will bring another round of
mainly rain showers /or even a several hour period of steady rain/
Saturday followed by a shot of colder air for Sunday into the
Aviation /03z Sunday through Thursday/...
mainly VFR conditions will dominate...bfd ceilings have
liefted...though lingering right around MVFR...and remains
possible trhough 06z. Gusty west-northwest winds have generally subsided with
bfd the only exception...with gusts up to 20kts possible. The
gradient will continue to slacken and shift to the north. Expect
winds to continue to subside as the evening continues.
High pressure building through the gr lakes will bring VFR
conditions for Sunday. Some increase in middle/high clouds is likely
over southern areas in response to a developing storm moving out
Sun night-Mon...an area of low pressure will track south of PA.
This could bring reduced conditions over the southern terminals.
Tuesday...mainly VFR. Lower conditions possible Laurel Highlands.
Tuesday night-Wed...periods of MVFR to IFR along with scattered rain/snow
showers as a frontal system moves through the region.
Thursday...MVFR possible in the mountains. VFR over central and eastern
near term...dangelo/la corte
short term...la corte