Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
345 PM EDT Wednesday Mar 12 2014
low pressure will continue to deepen as it lifts rapidly from
southern Pennsylvania northeastward along the New England coast
through tonight. Temperatures will plummet tonight into early
Thursday behind strong and gusty north-northwest winds. The cold
blast will be short-lived with a nice rebound in temperatures on
Friday. A series of Canadian frontal passages over the weekend
will send temperatures seasonably colder into early next week.
Near term /until 6 am Thursday morning/...
the cold air finally got into the northern tier counties as did
the snow. Last look Bradford was 29f and snowing. Snow and cold
air will continue to slowly change rain to snow across the
northern tier this afternoon.
Farther south...a modest band of intense showers has developed in
the warm air on the west side of the mountains. It is a few tens
of miles ahead of the real cold air and it can produce brief
stronger rain showers and can bring down gusty winds...winds are
over 60kts above about 5-6kft. Metars show these convective
elements can bring down 35 to 40 miles per hour winds. Just past kjst about
The low at 18z was over southwestern PA chugging eastward. Central
and southern areas will see this frontal boundary and linear
enhanced convection sweep across the state over the next 2-3 hours.
Expect snow in northern tier to begin accumulate. There are two
shots at snow in northwest PA...with the band just northwest of the low and the
larger deformation band over NE Ohio and Lake Erie. Had to bring
snow totals down considerably since last update.
The front should sweep across all of the region this evening and
cold air will change all remain precipitation to snow/snow showers.
Areas where it rains and rapid temperature falls could produce icy
roads/flash freezing conditions.
In northwest where it snows there could be some blowing snow.
It will get wind behind the cold front and winds will become quite tonight.
Very cold overnight toward morning temperatures should fall to
around 0 in northwest and upper teens in southeast.
Short term /6 am Thursday morning through 6 PM Thursday/...
cold windy start....bundle up on way out in the morning.
Winds should diminish late morning into the middle afternoon hours.
Very windy very cold.
No significant precipitation.
Just a cold wintry day with a shot at some near record low high
temperatures if temperatures do not begin to rise before sunrise
Long term /Thursday night through Wednesday/...
the good news is that the cold blast will be short-lived...with a
rapid moderation occurring on Friday. Temperatures should even level off
or go non-diurnal late Thursday night into the predawn hours Friday morning
especially across the western mountains some of the sheltered valleys in the
eastern part of the County Warning Area may still decouple toward daybreak.
Breezy SW return flow in advance of northern clipper surface low tracking
across the upper Great Lakes/southern Ontario and downsloping effects
should help to boost temperatures into the low/middle 40s north and low/middle
50s south. The models turn the low to the northeast up the St.
Lawrence Valley on day 5/Sat...dragging a trailing/weak cold front
across the northeast and middle-atl states. 12z model guidance indicates
some light shower activity along the cold front...with the highest
probability of precipitation based on consensus blend across northwestern sections between 00-06z Sat
GFS and ec ensembles show a cold upper-level trough remaining a
fixture over eastern Canada and the northestern Continental U.S....with ridging along
the West Coast possibly breaking down into early next week. At
the surface...a modestly strong/1040mb high pushing southeastward from the
upper Midwest/western Great Lakes should direct colder air into the
region behind a reinforcing Canadian frontal passage on Sunday...with temperatures
trending lower on day 5/6.
The key feature of interest will be a surface wave migrating northeastward from
the Texas/la Gulf Coast across the southeast to the Outer Banks by 12z
Monday. The 12z GFS trended in the direction of the 00/12z European model (ecmwf)
which has indicated a deeper and 'more defined' low for the past
four cycles. The 12z UKMET is very close to the European model (ecmwf) and just a
tad weaker. The GFS and especially the gefs are more suppressed vs
their non-NCEP counterparts. Regardless of the solution choice...the
main forecast challenge will initially be the track followed by potnl
rain/snow transition line on northwest periphery of the associated precipitation
shield. Final probability of precipitation were nudged in the direction of the European model (ecmwf)
bringing chance mentions of rain/snow to much of south-central PA
Sun night into Monday.
Aviation /19z Wednesday through Monday/...
rain showers will continue to spread eastward across southern PA this
afternoon...with MVFR and IFR conds prevailing. A line of heavier
showers and even some thunder right along the cold front and is
approaching kjst at 18z. This line will March eastward across the
remainder of southern PA late this afternoon...affecting kunv...kaoo...kmdt
Some low-level wind shear is expected above a shallow layer of
cool air that is trapped across central and eastern PA this afternoon.
Rain is changing over to snow across northwest PA /kbfd/ this afternoon...and
the rain/snow line will continue to progress southeastward as
colder air filters into the region. Very gusty northwest winds
will develop as the cold air is dragged into the region behind
this system late this afternoon and this evening.
For tonight....IFR and MVFR conds should slowly give way to VFR
across the central mountains and lower susq valley. Reduced ceilings may
linger across the western Highlands /kbfd and kjst/. Gusty winds will
continue tonight into Thursday.
Quieter weather should return for Friday.
Thursday...gusty north/northwest winds...gradually diminishing in the afternoon.
Friday...no sig weather expected.
Sat...weak cold front could produce scattered -shra/-shsn.
Sun-Mon...low pressure will pass to our south and could brush southern PA
with some precipitation.
with warmer temperatures rainfall today...we expect minor to
moderate rises on rivers and streams. The most significant rises
are expected on the main Stem susq. There is still enough ice in
spots to lead to ice jams...though significant decay has occurred
at many locations due to the recently warm weather. Ice jams are
possible but not predictable. Monitor water levels closely for
the rest of the week. Some minor flooding/ponding of water is
possible in areas where snow and ice block drains and slow run
Wind Chill Advisory from midnight tonight to noon EDT Thursday
Winter Weather Advisory until 8 am EDT Thursday for paz006-010-
Wind Advisory until noon EDT Thursday for paz025>028-034>036-
Winter Storm Warning until 8 am EDT Thursday for paz004-005.