Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
939 am EST Friday Feb 27 2015
weak impulse moves through the area today followed by an extensive
high pressure system for a majority of the weekend. As the high
slips off the coast on Sunday a weak warm front lifts through the
region as low pressure passes to our west and its associated cold
front pushes through on Monday. Another low pressure ejects out of
the Central Plains and crosses our region on Tuesday into Wednesday.
The lows associated cold front pushes through later on Wednesday
with another expansive high pressure system filling in behind it.
Near term /until 6 PM this evening/...
Snow showers have for the most tapered off across the region. A
mix of clouds and sun is expected throughout the remander of the
day. Temperatures were raised a few degrees with the 9:30 am
update and are still over met/mav. A upper level short wave trough
does approach our region by middle day, similar limitations will be
in place for any precip, best chance in the Poconos for some
Short term /6 PM this evening through 6 am Saturday/...
at least one model is depicting low level clouds developing by this
evening. However, this seems unlikely with the synoptic pattern of a
surface high sliding east toward the region as flow aloft
transitions to more zonal flow. Therefore, expect clearing skies
this evening into the overnight hours. This, combined with
subsidence in the low levels and light winds will lead to prime
radiational cooling conditions, especially for locations that still
have a snow pack. Thus, went slightly below guidance for lows.
Long term /Saturday through Thursday/...
medium range guidance is in pretty decent agreement with the large
scale features through the extended period. The middle-levels take on
more of a zonal-ish flow over the weekend with the next embedded
wave expected by Monday followed by deepening ridging through middle-
week as the longwave trough reloads to our west and advances through
late in the period.
Saturday...high pressure will be overhead allowing for lots of
subsidence and mostly clear skies. Temperatures will be rather cold
still, nearly 20 degrees under climatology for the last day of
Sunday - Monday...zonal-ish flow turns a bit sharper as the broad
trough reloads well to our west. Another passing shortwave aloft
approaches and pushes a cold front through the region very late
Sunday into Monday morning. Out ahead of the front temperatures are
able to modify a bit thanks to the departing high pressure now off
the coast and a light return flow setting up. We confined the higher
probability of precipitation until late Sunday night just ahead and with the frontal
passage. Decent amount of Theta-E advection occurring ahead of the
cold front with enough lift for a light snow to start before a
wintry mix of rain/snow/sleet/freezing rain occurs, mostly across
the southern half of the cwa, by Monday morning. There could be some
wak cold air damming occurring, even as winds turn more easterly,
but given the Arctic high will be offshore and not expecting a huge
response in the low-level winds the ground could still be cold
enough for some light freezing rain...moreso then we are currently
carrying in the forecast.
The best chances for an all snow event remains aross our northern
most zones where the warm nose gets close but does not have enough
push to move through, prior to the cold front ushering in another
shot of colder air. We are currently carrying a few inches of snow
across the Poconos at this time.
Tuesday - Thursday...with the cold front to our east and a brief
shot of high pressure behind it, the next system, forming deep in
the south, begins to enter the region from the southwest later on
Tuesday. A light onshore flow will help to enhance the low-level
moisture flux when combined with a strong low-level southerly surge
of warm/moist air. This event could have a copious amount of
moisture with it, given its origin and the modifying airmass we'll
have in place. Too early for ptype specifics but it does appear to
be another mixed event. This systems cold front drags through rather
slowly, as the troughing to our west sharpens and slows it down a
bit. This could allow for a longer duration event so we carry chance
probability of precipitation through the first half of Thursday before drying out.
Aviation /15z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe,
krdg, kilg, kmiv, kacy and surrounding areas.
Generally VFR conditions through the taf period. Brief IFR and
MVFR conditions with shsn are possible at kphl, kilg, and kpne
through 14z. Another caveat is that the GFS is indicating MVFR
ceilings developing this evening for primarily the Delaware
valley. This seems unlikely as it has been overestimating the
moisture in the low levels the last few days, so have chosen to
discount this for now. Otherwise, should see skies slowly clearing
through the day and light northwesterly winds.
Saturday - Sunday morning...VFR. Northerly winds prevail as high
pressure noses in from the west.
Sunday night - Monday...MVFR/IFR expected with snow to
rain/freezing rain possible by early Monday morning.
with the morning update we did raise wave heights based on buoy
observation to between five and six feet. This leads to a higher
confidence Small Craft Advisory seas will persist through the late afternoon. Winds
have already subsided and should remain below Small Craft Advisory criteria today
and tonight, although a few gusts near 20 knots are possible over the
ocean waters this evening. Wave heights should start to decrease
Saturday - Sunday...sub-sca expected, though persistent
northeast winds may allow for building seas across our southern
Sunday night - Monday...possible Small Craft Advisory conditions late on Sunday
ahead of an approaching cold front with increasing southerly
winds and building seas expected. Better chance behind cold front
passage on Monday with gusty west winds.
records for Friday and Saturday. Note records for Friday unlikely
but posted just in case one or 2 are approached at 1159 PM Friday
There is a greater chance of records Saturday.
Por / site / Feb 27 Feb 28
1872 / kphl / 6 1900 9 1934
1874 / kacy / 7 1934* 2 1934
1894 / kilg / 5 1934 -5 1934
1922 / kabe / -2 1963 -10 1934
1869 / krdg / 4 1934* 3 1934
1865 / kttn / 6 1934 1 1934
1948 / kged / 10 1963 8 1950
1901 / kmpo / -9 1993 -15 1907
Kacy rer for 3/1 is 5 in 1980.
Note: * indicate and other years.
Note: por = period of record,the year official climate observation began.
The following is a table of the ***projected*** top 5 coldest
february's on record, based on the current forecast, and thus
subject to change. Each ranking denotes the mean February
temperature /f/ and year of occurrence.
We rereviewed these projections listed below using this Thursday
mornings (26th) mins and the phi forecast as seen on ndfd and sft's. We
see phl/Abe/ilg all very close to yesterdays projections. Kacy
changed to a warmer projection however that could yet revert back to
a colder monthly average due to the potential for radiational
cooling on one or 2 of the mornings.
Por / site / 1st rank / 2nd rank / 3rd rank / 4th rank / 5th rank
1872 / kphl / 22.2(1934) 23.0(1979) 24.3(1885) 24.6(1978) 25.5(2015)
1874 / kacy / 21.6(1979) 23.8(1978/1934) 24.5(2015) 25.5(1875) 25.7
1894 / kilg / 20.2(1934) 22.1(1979) 22.7(1978) 24.5(2015) 24.9(1936)
1922 / kabe / 16.6(1934) 18.9(2015) 20.4(1979) 21.6(1936) 22.0(1963)
Per the above table, Abe is easily on track for the second coldest
February, Atlantic City 3rd coldest followed by the fourth coldest
at ilg, and the fifth coldest at phl.
The following is a table of the ***projected*** mean February 2015
temperatures /f/ and departures from normal. This is also based on
the current forecast, and thus subject to change. January 2015 mean
temperatures are also included for comparison purposes.
Por / site / Feb mean(f) / Feb normal(f) / departure / Jan mean(f)
1872 / kphl / 25.5 / 35.7 / -10.2 / 30.9
1874 / kacy / 24.5 / 35.3 / -10.8 / 30.2
1894 / kilg / 24.5 / 35.1 / -10.6 / 30.3
1922 / kabe / 18.9 / 30.7 / -11.8 / 25.9
In general, mean temperatures at our four major climate sites are on
track to be around 10 to 12 degrees below normal for February 2015.
It's also interesting to note that the projected February 2015 mean
temperatures will be well below the January 2015 mean temperatures.
To put this in perspective, normal mean February temperatures at our
four major climate sites are about 2 to 3 degrees warmer than January.
The opposite is shaping up for February 2015.
Also...of interest...this would also be the second coldest monthly
mean temperature on record at Allentown since records began in
1922; February 1934 being the coldest!
Phl projects around 12th coldest monthly mean since records began in
Atlantic City 7th coldest monthly mean since records began there
Wilmington has missing data in its database (1897-1916) and so we
don't focus as much attention on that record.
Marine...Small Craft Advisory for hazardous seas until 4 PM EST this
afternoon for anz450>455.