Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
627 am EST Monday Jan 26 2015
low pressure in North Carolina will track to the Virginia convective available potential energy
by noon then intensify rapidly in its northeast turn...nearing
Cape Cod at noon Tuesday and then weakening off to Nova Scotia on
Wednesday. High pressure from the west is forecast to arrive
Wednesday night. A weak low is expected to follow and pass over
our region Thursday night and early Friday. Another area of high
pressure is then anticipated for the start of next weekend.
Near term /until 6 PM this evening/...
light snow across the area overnight with a few 1 to 2 inch
reports across montgo County. Radar appears to show a break across
those areas now...but more energy beginning to organize to the S
over MD/VA. This should move north today with deteriorating
conditions expected later this morning.
The developing coastal storm will begin to throw some snow into
southeastern areas toward 00z. Again a few inches are possible over del
and coastal New Jersey. Any precipitation over the southern Delaware-Maryland-Virginia or extreme southeast New Jersey
may fall/mix with rain this afternoon. Most of the flags
associated with the two systems go into effect around noon. The
watches were changed to warnings (north of berks) and advisories
(berks and south). The starting times were lined up with the other
flags for simplicity.
Short term /6 PM this evening through 6 am Tuesday/...
the coastal system will deepen rapidly overnight as is moves from
off the NC/Virginia coast to the 40/70 benchmark. Steady/heavy snows will
affect mostly the eastern 2/3rd of the area with lighter snows and
blowing snow over the western/southwestern edges of the area. Our snow totals
are not much different than the ones issued Sun afternoon...perhaps
a few inches lower if anything. Warning criteria snow may or may
not occur across the farthest western warning areas(carbon and
lehigh)...but blowing snow across the higher elevations will make
things look warning-like. Plenty of travel impacts across the
region. Highest totals through 12z northern half of New Jersey and into extreme eastern
Long term /Tuesday through Sunday/...
***blizzard coastal New Jersey will be ending Tuesday afternoon***
500 mb: deep occluded cyclonic circ near the southern New England
coast Tuesday departs with ridging Wednesday. The next trough
forms southeastward to the East Coast Thu-Fri. Thereafter the Hudson Bay
vortex slides southeastward into Quebec by Monday.
Temperatures: calendar day averages will be below normal Tuesday
through Sunday with several days around 10 degrees below normal.
Forecast basis: unless otherwise noted within the dailies. This
forecast is a 50 50 blend of the 00z/26 mav/met for Tuesday-Wednesday.
The 00z/26 mex MOS was applied Wednesday night and Thursday. The
05z/26 wpc d4-8 elements of dewpoints/wind/sky/pop/Max-min temperatures
were not used for the longer range...but we did adjust probability of precipitation higher
Thursday afternoon into Friday morning for the next clipper.
Tuesday...bent back middle level front at 700-600 mb with fgen excessive
snowfall rates coastal central and northern New Jersey will be winding
down rapidly Tuesday afternoon with surface winds backing to northwest. Ideal
snow growth region near 650mb nnj northeastward with 1-3"/hour expected even
for the first few hours after sunrise Tuesday. But...how far west
of I 95 is it snowing Tuesday is still somewhat uncertain. Usually
with banding there are areas of strong subsidence and drying in
what you would otherwise consider a snowy environment. Those areas
of drying can surprise. This mesoscale meteorology we're not too good
at realistically and reliably detailing more than a few hours in
advance. Lets think of lighter snow occurring across the rest of
eastern PA and the Delaware-Maryland-Virginia Tuesday morning then drying out. Northwest wind
gusts 25-35 miles per hour. Considerable blowing and drifting of the snow
occurs, especially across New Jersey. Estimating drifts to 4 feet are
possible in exposed regions of coastal NE NJ, where snowfall
exceeds 18 inches.
Tuesday night...clearing...with gusty northwest winds 20 miles per hour. Drifting
snow continues, especially coastal nnj
Wednesday...MO/sunny with gusty northwest winds 20-30 miles per hour. Drifting snow
Thursday into Friday...a clipper system from the northwest and west
may bring a shot of light snow from late Thursday into Friday. For
now we are forecasting an event ... amounts under 2 inches
in this cf situation and for now mainly north of I 78.
Later Friday into Saturday...another shot of cold dry air is anticipated.
Next Sunday and Monday...it might get interesting again? It does
not look necessarily straightforward with the southeast evolution of the
polar vortex and what might develop to our south ahead of the
possible arrival of bitterly cold air here early next week.
Aviation /12z Monday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
**High impact event, especially tonight and Tuesday morning**
Mostly MVFR conditions early today will be somewhat changeable later
as the weak clipper system crosses the area. Conditions may go VFR
for awhile later this morning and into the early afternoon...but
confid in placement and timing for this is low and will not be
included in the tafs. The Nor'easter will affect the terminals
beginning late this afternoon and into Tuesday. Widespread LIFR with
snow and blowing snow common. Strong NE winds tonight and into Tuesday.
Tuesday...significant morning snowfall and IFR conditions probably
confined mainly to New Jersey from vicinity kphl-kacy line northward and that
snow will be ending in the afternoon. Becomes VFR everywhere during
the afternoon but with blowing and drifting snow. Northwest wind gusts
Tuesday night...VFR scattered or broken at or above 4000 feet. Northwest wind gusts 20 knots.
Wednesday...VFR scattered at or above 4000 feet. Northwest wind gusts 20-30 knots.
Thursday into Friday morning...VFR to start Thursday then a chance
of snow showers late Thursday or early Friday when conditions may lower
into the MVFR or IFR range for a time. SW wind Thursday afternoon shift northwest
significant Nor'easter to affect the waters later today and tonight.
Marine flags will remain as they are with the morning package. Storm
warnings for most of the coastal waters and gales for del Bay and
the southern two coastal zones. Beginning and end times continue to
Tuesday...a marine Storm Warning is in effect for our ocean waters
off New Jersey to start the day. A Gale Warning is in effect for the
waters off Delaware and for Delaware Bay. Winds diminishing in the afternoon.
Tuesday night...leftover northwest gales during the evening with slowly
diminishing wind overnight. Freezing spray.
Wednesday...Small Craft Advisory conditions are expected with
Wednesday night through Thursday...no marine headlines are
Friday...an Small Craft Advisory should eventually be needed by late Friday as a
northwest flow of cold air advection develops behind the northeastward
departing clipper low.
coastal flooding...coastal flood watches will be converted to
warnings with the 330 am forecast package. Widespread minor with a
few areas of low-end moderate tidal flooding expected. The tide
cycles tonight and Tuesday morning are the most likely one to have
flooding concerns...the greater threat being tonights midnight
high tide cycle.
PA...Winter Storm Warning from noon today to 6 PM EST Tuesday for
Winter Weather Advisory from noon today to 3 PM EST Tuesday
Winter Storm Warning from noon today to 3 PM EST Tuesday for
New Jersey...Winter Storm Warning from noon today to 6 PM EST Tuesday for
Coastal Flood Warning from 11 PM this evening to 7 am EST
Tuesday for njz012>014-020>027.
Blizzard Warning from noon today to 6 PM EST Tuesday for
Delaware...coastal Flood Warning from 11 PM this evening to 7 am EST
Tuesday for dez002>004.
Winter Weather Advisory from noon today to 3 PM EST Tuesday
Maryland...Winter Weather Advisory from noon today to 3 PM EST Tuesday
Marine...Storm Warning from noon today to 6 PM EST Tuesday for
Gale Warning from noon today to 6 PM EST Tuesday for anz430-