Scientific Forecaster Discussion
fxus61 kphi 192036
Area forecast discussion
National Weather Service Mount Holly New Jersey
336 PM EST Tue Nov 19 2019
low pressure will continue moving away from the coast toward the
Canadian Maritimes through tonight as high pressure builds across
the mid-Atlantic. Thursday through Friday, low pressure will pass
from the Great Lakes region to southern Quebec and push a cold front
through our region on Friday. Low pressure will develop across the
Carolinas and pass just to the south of the forecast area and
offshore Saturday into Sunday. High pressure then returns through
early next week.
Near term /until 6 am Wednesday morning/...
a surface analysis this afternoon showed low pressure in the
Canadian Maritimes with another low well east of the Delmarva coast.
A weak high was near the Gulf Coast while a frontal zone was draped
from the Midwest to the Tennessee Valley.
An upper-level trough will pivot northeastward across the mid-
Atlantic and northeast tonight as a strong short wave in its base
tracks east of the Carolina coast. This trough may tend to start
closing off late tonight across our region. Despite this, the
moisture looks shallow and there is not a lot of lift especially
organized. The soundings in the Poconos are hinting at some drizzle
potential, however the low-level profile is looking not quite
saturated enough. In addition, some sprinkles cannot be ruled out
mainly across Delmarva given upstream radar returns however this may
dissipate northward or not really reach the ground. As a result, we
continued with a dry forecast through tonight. A lot of cloud cover
is expected to move across our area during the course of the night
with much of this the high to mid level variety. The winds will be
on the light side to even locally calm, although some increase
should take place closer to daybreak as 850 mb cold air advection
teams up with some tightening of a pressure gradient. Due to the
expectation of quite a bit of cloudiness through the overnight, fog
is not anticipated and radiational cooling should not be completely
efficient. Low temperatures are mostly a MOS/continuity blend.
Short term /6 am Wednesday morning through 6 PM Wednesday/...
the axis of an upper-level trough is forecast to shift to our
northeast and east during Wednesday morning. As this occurs, surface
high pressure will build closer however there will be a tightened
pressure gradient between it and low pressure nearing the Canadian
Maritimes. The forecast soundings show quite a bit of moisture in
the lower levels therefore cloud cover should prevail, although with
deeper mixing occurring in the afternoon at least some thinning of
the cloud cover should take place especially across the southern
areas. There is strong warm air advection forecast to surge up the
Ohio Valley, setting up a strong thermal gradient to our south and
west and this may also add to the cloud cover especially as some
soundings show a strengthening inversion developing through the day.
The increased mixing beneath any inversion during the late morning
and afternoon hours will allow for a breeze to increase from a
northwesterly direction, and peak wind gusts look to be around 25
mph. These winds should diminish fairly quickly late in the
afternoon as the depth of the mixing lowers. Temperatures will
depend on the extent of the cloud cover through the day, however
many places should top out right near 50 degrees.
Long term /Wednesday night through Tuesday/...
the extended forecast is largely handled by two events. High
pressure through most of the rest of the work week and a
developing upper level trough with a surface low tracking over
Quebec bringing a slow moving cold front through the region.
High pressure will continue under an upper level ridge leading
to quiet weather and partly cloudy skies through Friday
morning. Temps will be warming daily getting closer to near
normal. By Friday morning an upper level trough will be digging
into Quebec towards the Maritimes leading to warm southerly flow
across the region. As we sit in the warm sector of an elongated
low pressure system temps should warm into the mid to upper 50s
to low 60s across the region. If those temps do materialize it
will be only the fourth day of the month where we see a day
Above normal temps quickly return back below normal heading
into the weekend as rain falls across the area Friday into early
Friday evening and temps quickly cool behind the cold front. The
area sees a brief break in action Friday night into Saturday
morning before a weak shortwave trough digs through the Southern
Plains and pushes a surface low through the Carolinas into the
mid-Atlantic Saturday evenings. At this point thermal profiles
indicate that we'd be cold enough to see some light snow out of
that low pressure system however surface temps should be warm
enough that not much would accumulate.
Coming out of the weekend Monday looks fairy quiet as high
pressure begins to build across the eastern Continental U.S..
Aviation /20z Tuesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Rest of this afternoon...VFR. Westerly winds 3-6 knots, becoming
mostly light and variable toward evening. High confidence,
Tonight...VFR ceilings. Winds mainly light and variable or locally
northwest around 5 knots. Moderate confidence.
Wednesday...VFR ceilings. Northwest winds increasing to 10-15 knots
with gusts to around 20 knots. Moderate confidence.
Wednesday night through Thursday...VFR with clearing skies
expected Wednesday night. Northwesterly winds 5-10 kts with
gusts of 15-20 kts possible early. Moderate confidence.
Friday...VFR with MVFR ceilings developing later in the day with
periods of IFR possible. Rain showers overspreading the region
throughout the day ahead of a cold front. Southerly winds
becoming west late around 10 kts with gusts up to 20 kts.
Saturday...VFR initially with MVFR developing late in the day
through the overnight. Periods of IFR possible. Rain
overspreading the region late in the day and through the
overnight hours. Winds 5 kts or less favoring a northwesterly
direction. Low confidence.
the conditions are anticipated to be below Small Craft Advisory
criteria through tonight and even to start Wednesday. A tightening
pressure gradient though along with cold air advection will result
in better mixing during the day. This should result in northwesterly
wind gusts to around 25 knots especially starting Wednesday
afternoon. As a result, a Small Craft Advisory has been issued for
all areas starting at 16z/11am.
Wednesday night through Thursday... Small Craft Advisory in
effect until 7 am (12 am) Thursday morning for the ocean
(delaware bay) waters with winds gusting 25-30 kts overnight and
seas up to 5 feet. Winds and seas will decrease quite a bit by
Friday...Small Craft Advisory conditions likely developing throughout the day as
a cold front approaches the mid-Atlantic and southerly winds
increase with gusts around 25 kts and seas 3-5 feet.
Saturday...some lingering Small Craft Advisory criteria possible in the morning
hours, otherwise sub-Small Craft Advisory conditions are expected to prevail for
much of the day.
Marine...Small Craft Advisory from 11 am Wednesday to 7 am EST Thursday
Small Craft Advisory from 11 am Wednesday to midnight EST
Wednesday night for anz430-431.