Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
823 PM EDT sun Mar 16 2014
cold high pressure will build to our north through Tuesday. Meanwhile,
an area of low pressure is forecast to pass off the middle
Atlantic coast late tonight before moving quickly out to sea on
Monday. Another area of low pressure is expected to move across the
northern plains into southern Canada Wednesday into Thursday,
bringing first a warm front through the region and then its
associated cold front will cross the area Wednesday night. High
pressure is expected to follow for Thursday. Another cold front
from the west is forecast to arrive on Friday night or Saturday.
Near term /until 6 am Monday morning/...
the 18z models trended drier and slightly more suppressed. Overall
the idea of an extremely tight precipitation gradient on the northwest/north side make
sense. All of the models are going to be too high with their forecast
surface dew points at 00z in our County Warning Area. Some too cold with their 2m
temperatures also. The precipitation is not edging geographically north of model
quantitative precipitation forecast projections which again is testimony to the cold dry air with
the surface high. Thus confidence about probability of precipitation and snowfall amounts
along the northwest edge of our headlines remain low. We nudged snowfall
amounts down and tried to tighten the gradient.
Elsewhere latest sels mesoscale discussion and observations from WV is showing banded
snow underway. 18z WRF still forecasting impressive fgen forcing into
our cwa, but a bit south of previous projections. This update we
also tightened the axis of heaviest snow and dropped slightly
farther to the south. Precipitation reaching the ground has just about
extended through most of Virginia.
High pressure will remain across the Great Lakes tonight while low
pressure moves along a stationary front across the southeast states. A
second low will form along the front (off the east coat) tonight and
move off into the Atlantic late. Todays 12z model runs have (you
guessed it) come back to a wetter and further north solution,
similar to what they had a few days ago. As a result, we have
decided to add a tier of counties north/west to the (previous) advs
and warnings. Snow totals will be 1 to 2 inches higher with the
greatest totals still expected over the Delaware-Maryland-Virginia and southern New Jersey. The
storm will have a profound impact on the morning rush for the metropolitan
areas...so plan on plenty of extra travel time Monday morning. The
snow will start around sunset this evening over the Delaware-Maryland-Virginia and
arrive a few hours later across southern New Jersey and southeast PA. Little if any snow
will fall over the southern Poconos and northern New Jersey. Sub-advection amounts (1-2
inches) will fall across the Lehigh Valley and Berks County.
Winds will remain north or northeast tonight with winds gusting at
times to 20 miles per hour overnight. Low temperatures will drop into the teens
across the north and mostly low/middle 20s elsewhere.
Short term /6 am Monday morning through 6 PM Monday/...
the steady snows will end from west to east during the day. The ending
times of around noon for the expiration of the west-southwest flags still looks
good. The accumulating snows will be over across the northern half of the
County Warning Area while the 12z-18z totals over the Delaware-Maryland-Virginia and southern New Jersey will be
1-1.5 inches. (So most of the storm accums are before 12z mon).
Clouds will decrease over the area during the afternoon. Highs will
top out in the low/middle 30s across the area with some upper 20s far
Long term /Monday night through Sunday/...
high pressure will build down from Canada for Monday night into Tue,
bringing cool and dry weather. Another area of low pressure is expected to
develop off the southeastern Continental U.S. CST, but attm, all guidance (except the
nam) keeps it well off the coast.
By Tuesday night, an area of low pressure will move eastward from the upper MS
valley and bring a warm front through the region. This front could trigger
some light precipitation by Erly Wednesday. Depending on onset time, there
could be some snow or a mix from the I-95 Corridor North and W, before
a changeover to all rain after daybreak. This looks to be a
predominantly rain event on Wednesday as temperatures rise. The cold front associated
with this low will cross the area Wednesday night. Precipitation chances will
increase through the day ahead of frontal passage.
High pressure will then build over the southeastern states and keep things
dry for Friday before another weak low approaches from the west Friday night
into Sat. This low will bring another shot of precipitation and while it
looks to be predominantly rain, temperatures will be cold enough north and west
for snow or a mix Friday night into Erly Sat.
A large high is then expected to build down from Canada for sun.
Temperatures will start off below normal then rise to near or a bit above
seasonal values for most of the extendd period.
The Vernal equinox is Thursday at 1257 PM. Hopefully mother nature
can take the hint!
Aviation /00z Monday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Low pressure will move south of the area tonight and Monday while
strong high pressure remains to the north. Clouds will continue to
lower and advance across the region this evening and overnight.
The snows have arrived across the Delaware-Maryland-Virginia and will continue to spread
across the rest of the region tonight. Only light snows are
expected at kabe and krdg...while higher totals and IFR conditions
expected for the del valley and southern New Jersey taf sites. Winds will be
mostly north/NE at 10 to 15 kts with g20 at times.
Monday...IFR conditions early (mvfr north/w) will all improve back to
VFR from northwest/southeast during the day. However, kmiv and kacy may remain
MVFR through most of the day. Winds will remain mainly NE at 10
to 15 kts through the day with some gusts early, before dropping back
under 10 knots into the evening.
Monday night through Tuesday....VFR. High confidence.
Tuesday night through Wednesday night...mainly VFR with a chance of rain
showers lowering conditions to MVFR at times, as first a warm
front passes through Tuesday night then a cold front Wednesday night. MDT
Thu-Fri... mainly VFR. MDT to high confidence. Some lower ceilings possible
especially north and west late Friday. MDT confidence.
the placement and types of marine flags will remain unchanged...but
we will move up the timing for the beginning of the gales/Small Craft Advisory to
00z. Gales expected to begin this evening over the ocean and lower
del Bay. Small Craft Advisory conditions expected over the upper del Bay. Gales
should last at least until noon Monday...before a transition back to
Small Craft Advisory conditions. The NE fetch will create rough seas over the
southern/central coastal waters and southern del Bay...with the northern coastal
waters being somewhat sheltered.
Monday night-Fri...wind speeds are forecast to be mainly less than
25 knots except through Erly Tuesday. However, wave heights on our ocean
waters may remain around or in excess of 5 feet through the period.
the developing northeasterly flow will result in an increase in
tidal departures. The astronomical tides associated with the full
moon are rather low and tidal departures of greater than a foot
and a half would be needed for minor tidal flooding to occur.
Being that the low is not forecast to be particularly strong, the
latest extratropical surge guidance is not indicating that any
tidal flooding will take place.
begorah, more snowfall records to fall and/or climbing higher in
the snowfall record department:
Daily snowfall records for:
Allentown 12.0 in 1896 4.2 in 1967
Atlantic City 1.7 in 1978 1.6 in 1965
Philadelphia 4.1 in 1978 3.5 in 1892
Wilmington 2.9 in 1978 2.4 in 1965
In Philadelphia, we have had 13 separate calendar days in which
an inch or more of snow has fallen this season. We have a chance
to make it 15 calendar days which would give this season sole
possession of second place. 14 calendar days occurred in 1898-99
while the record is 17 calendar days in the 1917-18 season.
Speaking of second place, an additional 2.7 inches would give
Philadelphia (62.9 inches currently) the second snowiest season on
record, surpassing the 65.5 inches during the 1995-6 season. The
all-time record is 78.7 inches in 2009-10. It appears safe through
this event. If 6.6 inches or more of snow were to fall early next
week, it would be the first time ever there have been four double
digit months of snowfall in one season in Philadelphia.
Atlantic City (33.7 inches currently) needs one tenth of an inch
of additional snow to crack the top 10 snowiest seasons on record
and 8.7 additional inches to supplant 2002-3 as the 5th snowiest.
The most recent snowiest winter was 2010-11 (ranked 8th) at 38.0
inches. Numero Uno is the winter of 2009-10 at 58.1 inches.
Wilmington (52.9 inches currently) needs 3.1 additional inches to
supplant 1995-6 as the second snowiest season on record. The
record is 72.8 inches during the 2009-10 season.
Allentown seasonal snowfall ranks:
75.4 inches in 1993-4
71.4 inches in 1995-6
67.2 inches in 1966-7
66.9 inches in 2013-4
PA...Winter Weather Advisory until noon EDT Monday for paz070-071-
New Jersey...Winter Storm Warning until noon EDT Monday for njz016>018-
Winter Weather Advisory until noon EDT Monday for njz012>015-
Delaware...Winter Storm Warning until noon EDT Monday for dez001>004.
Maryland...Winter Storm Warning until noon EDT Monday for mdz008-012-015-
Marine...Gale Warning until noon EDT Monday for anz431-450>455.
Small Craft Advisory until noon EDT Monday for anz430.