Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
652 PM EST Monday Jan 26 2015
periods of light snow will decrease across central Pennsylvania
tonight as a strong coastal storm tracks towards New England
tonight. The coastal storm will rapidly intensify tonight and
Tuesday...as it tracks east of New England. High pressure will
build over the region for the middle of the week...followed by an
Alberta clipper Thursday.
Near term /until 6 am Tuesday morning/...
600 PM update...
extended the advisory for those middle susq counties through 11 PM...as
snow is still falling and is not tapering off as quickly as 4km
NAM/rap/hrrr had portrayed. Models continue to indicate that this is
the first area of the County Warning Area which will have the snow drop to
nothing. Snow has re-entered/developed over the southeast and current
numbers still look good over the whole region.
added Tioga Colorado to the advisory as snow should continue to fall there
for another few hours and they are already pushing 3-5 inches of
snow off their cars. However...the rap and hrrr both slide the big
band off to the west /not east/ slightly - so lesser chance for
Sullivan Colorado PA to get too much more. Just upped probability of precipitation slightly to
just below 101 percent in the central and west.
deformation between the inverted surface trough over western and
southwestern PA and rapidly developing coastal low off of
southeast Virginia is maintaining categorical probability of precipitation/snow across The
Laurels and central/west central/northwest/northern mountains
presently. My southeast counties have started to see some light
activity but it is still removed from the better deformation
associated with the inverted trough to the west and the intensifying
low to the east. Lowered the lower end of snow far ranges for the
east in west-southwest...generally 2 to 5 inches expected overall before
accumulate snowfall exits PA by daybreak Tuesday morning.
Overall however...widespread light snow will continue to fall over
central PA this evening into late tonight along the axis of deep
easterly flow between low to the south and high pressure over New
England...forced locally by the increasing aforementioned
deformation. Hi res NAM/hrrr/WRF arw all support an additional 1-3
inches today...with the highest amts across the central
mtns/alleghenies. Keeping headlines as is for now but some may
need to be extended overnight depending upon where the deformation
propogates. Hrrr indicates a southwest shift to the forcing after
03z...as the parent coastal circulation dominates and takes over
effectively disrupting and eliminating the deformation forcing
snowfall over central PA by 12z.
Short term /6 am Tuesday morning through 6 PM Tuesday/...
as mentioned above...deformation snow showers should dwindle early
Tuesday...while north-northwest flow in wake of departing coastal low draws
much drier air into central PA. 25 to 35kt NE wind gusts will be
felt as tight pressure gradient is realized in wake of storm just
offshore of southern New England coast. As previously
mentioned...there is the potential of some blowing/drifting...especially
eastern PA where bukfit soundings support gusts between 30-35kts. Ens
mean 925 temperatures support maximum temperatures Tuesday from near 20f over the north
mountains...to around 32f across the lower susq valley.
Long term /Tuesday night through Monday/...
deep storm will pull away from PA Tuesday night. With winds
from the north...took out snow showers for jst.
Skies should clear out by Wednesday morning.
Main change was Wednesday night...did lower temperatures...based on 12z
model runs...and that with mainly clear skies and light
winds...expect temperatures to drop...with fresh snow cover.
Next system will bring some snow showers to the area later Thursday
into Friday. This system not looking like it would result in
a coastal real near the coast.
Colder air for Friday night.
Weekend not looking too bad...colder air will try to build in
early next week.
Aviation /00z Tuesday through Saturday/...
for 00z package...extended poor conditions further out in
While conditions may not be bad all the time...as been the
case since I came in at 8 am this morning...deep storm
forming just off the middle Atlantic coast at this time will
continue to wrap moisture to the west. Radar shows rather
heavy snow now to the west and SW of MDT...extending
northward to between unv and ipt. SW winds at ipt suggest
inverted trough still in place. Snow will be an problem
until this feature falls apart on Tuesday.
Winds will pick up on Tuesday...as storm starts to pull
north adn east of the area.
Wednesday...VFR with no sig weather expected.
Thursday...VFR to start...with late day restrictions spreading in from
Thursday night-Fri...widespread IFR/MVFR in snow.
Winter Weather Advisory until 7 am EST Tuesday for paz004>006-
Winter Weather Advisory until 11 PM EST this evening for