Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
918 PM EST Wednesday Jan 28 2015
high pressure will move in from the west overnight and offshore
on Thursday. Low pressure will move across the Great Lakes
Thursday night and reform near Cape Cod on Friday. This will cause
an Arctic front to cross the region Friday afternoon. More high
pressure will move in from the Ohio Valley and over the region
this weekend. A complex storm system will affect the region early
Near term /until 6 am Thursday morning/...
high pressure was centered over southwestern Pennsylvania and
vicinity this evening. The high will drift to the east with its
axis reaching our region toward morning. The sky is expected to
remain clear for much of the night with perhaps some wisps of
cirrus arriving near daybreak.
The northwest wind will continue to diminish as it veers toward
the north. The wind will likely become light and variable at many
The light wind, clear sky and snow cover will cause temperatures
to fall quite a bit overnight. Minimum readings should be in the
single digits in the north and in the teens across the south.
Short term /6 am Thursday morning through 6 PM Thursday/...
the high pressure will shift to our south and east on Thursday as
a low pressure system tracks toward the middle Atlantic from the
Great Lakes region.
Clear skies will start to cloud up as the next system approaches.
Precipitation looks to hold off until later in the day but we
might start to see our first flakes fall during the
afternoon/early evening hours.
Temperatures will generally rise into the upper 20s to lower 30s
through much of the region, with middle to upper 30s across southern
Delaware and along the coast.
Long term /Thursday night through Wednesday/...
the middle-level pattern features the polar vortex over hudson's
Bay... a ridge in vicinity of the West Coast of noam and a southern stream
cut off low near Baja California California...that may finally ejected
northeastward by the middle of next week. These features will
guide shortwave energy through a mean trough over the east Continental U.S.. this
trough is expected to become negatively tilted...leading to the
redevelopment of a clipper system in vicinity of Cape Cod on Friday...and will
be followed by shortwave ridging for a brief time over the region on
Sunday. Meanwhile...a primary shortwave enters the northern inter-
mountain west on Saturday accompanied by several other pieces of
energy extending from hudson's Bay to the Gulf Coast. The degree
of phasing these features undergo as they traverse the east Continental U.S.
Trough...and redevelopment in vicinity of the East Coast...presents the
greatest uncertainty in this forecast. At the d+5 time
frame...it/S to early to lock onto any specifics...but the nao is
projected to go from negative to positive which is typically
favorable for East Coast cyclogenisis.
Aviation /02z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
VFR conditions are expected overnight and on Thursday. The sky
will remain clear overnight with an increase in cirrus on Thursday
morning and an increase in middle level clouds, with bases at or
above 10,000 feet, during the afternoon.
A light northwest to north wind should become light and variable
at most locations for late tonight and Thursday morning. A light
southeast wind around 4 to 8 knots is anticipated to develop for
Thursday night through Friday morning...MVFR/IFR in light snow.
Friday afternoon...conditions improving to VFR. MVFR/IFR possible
in snow squalls. Northwest winds gusting around 30 knots.
Friday night...VFR with gusty northwest winds expected to continue.
Sunday and Monday...light snow is expected to overspread the area
late Sunday or early Monday...low confidence on timing. MVFR/IFR
possible in the snow.
the Small Craft Advisory on the ocean is in effect through 1 am.
Winds are diminishing as the pressure gradient weakens across our
area. Seas are also decreasing. Expect both winds and seas to
fall below Small Craft Advisory criteria on our ocean waters later
tonight. Light freezing spray will remain possible through
Sub-advisory conditions are expected for Thursday with light
easterly winds and seas around 2 to 3 feet on the ocean.
Thursday night...winds and seas may approach Small Craft Advisory thresholds.
Friday/Friday night...gale force wind gusts increasingly likely.
Sat...gale conditions diminishing back to Small Craft Advisory conditions.
Sun...sub Small Craft Advisory conditions expected.
Monday...winds and seas may approach Small Craft Advisory thresholds.
Marine...Small Craft Advisory until 1 am EST Thursday for anz450>455.