Scientific Forecaster Discussion
fxus61 kphi 172106
Area forecast discussion
National Weather Service Mount Holly New Jersey
406 PM EST Wed Jan 17 2018
low pressure with its attendant frontal system will move off
the East Coast tonight. High pressure will build across the Gulf
Coast through the end of the week, then offshore over the
weekend, bringing fair weather to the mid- Atlantic region. Low
pressure is forecast to develop over the central U.S. On Monday.
This low will move northeast through the Great Lakes Monday
night into Tuesday, pulling a cold front across the mid-
Atlantic area on Tuesday.
Near term /until 6 am Thursday morning/...
expecting a return to tranquil weather overnight. The mid and
upper level low progressing east should move off the Carolinas
coast late tonight. The track of this low should be far enough
south that we won't see any additional precipitation, except for
some very light snow through early evening across southern
Otherwise, expect clearing skies. With the light northwesterly flow,
should see temperatures continue to fall, with lows in the single
digits and teens across the area. The strongest winds and lowest
temperatures should not be coincident with each other which will
limit the low wind chill threat. Still, wind chill values below zero
are possible across the southern Poconos (cold, but still above
advisory level, and a far cry better than a few weeks ago).
Short term /6 am Thursday morning through 6 PM Thursday/...
on the heels of the low, a mid level short wave ridge is
expected to propagate over the region through the day tomorrow
resulting in mostly sunny conditions. At the surface, the
pressure gradient is expected to increase for a period tomorrow
as the surface high builds in. As a result, could see some gusty
conditions, but on land, not expecting gusts above 25 mph.
Temperature wise, we will still have cold air advection with the
northwesterly flow. As a result, expect highs to be from the mid 20s
to near 40 across the region, or about 5 degrees below normal.
Long term /Thursday night through Wednesday/...
the extended forecast will feature somewhat above normal
temperatures (for a change) and generally fair weather at least
through this weekend. A fairly strong frontal passage with
associated low pressure and precipitation is expected sometime
on Tuesday of next week.
By Thursday night the low pressure aloft now over the southern
Appalachians will be well offshore. A fast-moving shortwv trof
will swing across New England but should have little effect on
sensible weather over the mid-Atlantic region. Thereafter
through the weekend zonal flow aloft will prevail across the
north-central and northeast US. Meanwhile a large area of high
pressure centered along the Glfmex coast will gradually shift
east and off the southeast US coast by Sunday. Westerly flow
around the northern periphery of this high will help maintain
fair weather with a trend toward moderating temps, especially
A fairly deep trof aloft is forecast to move into the western US
over the weekend and into the central grtplns by Monday. In
response surface low pressure should develop over the plains and
move eastward into the grtlks by Tuesday. The associated cold
front should move through New Jersey and vicinity roughly in the Tuesday
morning time frame, although the lastest European model (ecmwf) looks a bit
slower. Increasing SW low-level flow ahead of the low/front will
result in increasing moisture starting Sunday night. At that
time the forecast includes slight chance pops well north of phl,
with the possibility of some freezing rain or drizzle, depending
on the degree of overnight surface cooling.
Forecst pops increase from chance on Monday to likely Monday
night with the approaching cold front. Depending on how quickly
cold air moves in, there could be some changeover to snow in the
Poconos late Monday night. Due to timing uncertainty, the
forecast maintains some chance for precip through Tuesday,
mainly in the morning. Forecast Max temps for Tue are still
above freezing (and above normal) but cold advection aloft could
produce snow showers well north/west of phl.
The air mass behind the front is not terribly cold and forecast
Max temps for Wednesday look to be still slightly above normal.
Aviation /20z Wednesday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Tonight...VFR conditions are expected with clouds diminishing.
Northwesterly winds near or below 10kt are expected to continue
overnight. High confidence.
Tomorrow...VFR conditions with few, if any clouds. Northwesterly
winds 10 to 15 kt with gusts up to 20 kt. High confidence.
Friday through Sunday...VFR conditions expected. West to
southwest winds, generally less than 10 kt. High confidence.
Monday...mainly VFR conditions but occasional MVFR possible in
expect the highest winds, and most widespread Small Craft Advisory
conditions to occur late tonight through mid morning Thursday. Gusts
near or above 25 kt are likely to continue through the rest of the
day. Therefore, have continued the Small Craft Advisory as is for now.
Thursday night...conditions expected to drop below advisory
Friday-Sunday...conditions expected to remain below advisory levels,
but winds may periodically gust around 20 knots.
Monday...increasing south winds with gusts possibly approaching
Small Craft Advisory levels late in the day.
the National oceanic and atmospheric administration all-hazards weather radio transmitter in Sudlersville
has returned to service with the correction of earlier phone
Marine...Small Craft Advisory until 6 PM EST Thursday for anz450>455.
Small Craft Advisory until 10 am EST Thursday for anz430-431.