Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
1045 am EST Sat Feb 28 2015
high pressure located over the southern Great Lakes and the Ohio
River valley early this morning will build to the east. The high
is forecast to pass off the coast early on Sunday. A cold front is
expected to approach from the northwest on Sunday and it should
pass through our region on Sunday night followed by another area
of high pressure for Monday and Monday night. Low pressure is
anticipated to move across the Great Lakes on Tuesday and Tuesday
night, then down the Saint Lawrence River valley on Wednesday. The
low is forecast to pull a cold front slowly through our region on
Wednesday and Wednesday night with high pressure following in its
wake for the end of the week.
Near term /until 6 PM this evening/...
previous forecast in good shape. Minor adjustments to temperatures/dew
High pressure builds across the area today and centers itself
overhead by the end of the day. This will provide fair weather
through today, with only cirrus clouds expected. Temperatures will
be significantly below normal, around 20 degrees in most places.
Winds will be northwest-north around 5-10 miles per hour until the high fully
builds across the area, then become light and variable/calm.
Short term /6 PM this evening through 6 am Sunday/...
the high will be centered across the area this evening, before
beginning to build offshore overnight. This will continue calm,
cool, dry weather. Cloud cover is expected to increase overnight,
which may help level temperatures off some overnight and prevent
significant radiational cooling during the night. Lows remain
15-20 degrees below normal.
Long term /Sunday through Friday/...
middle clouds are expected to be overhead on Sunday morning with
additional moisture building into our region during the day in the
return flow as high pressure drifts farther off the coast. The
guidance continues to speed up the arrival time of the
precipitation. It appears as though we may see some light snow
beginning to build into our region on Sunday morning.
The precipitation event is forecast to be focused on Sunday
afternoon and Sunday evening with the precipitation coming to an
end from late Sunday night into early Monday morning following the
passage of the cold front.
The anticipated temperature profiles suggest a transition from
snow through sleet and freezing rain to rain on much of the
coastal plain as temperatures are expected to rise through the
event. A change from snow to sleet and freezing rain is
anticipated to the northwest of the fall line, with our far
northern counties likely to remain all snow and sleet.
Based on the latest projections, we could see 4 to 6 inches of
snow in the elevated terrain up north, tapering down to around an
inch or two along the Interstate 95 corridor. Ice accumulations of
one to two tenths of an inch may be focused across southeastern
Pennsylvania and central New Jersey where the freezing rain may
last the longest. Lesser amount are anticipated on either side of
A drying trend is forecast for Monday with temperatures rising
into the 30s up north and into the 40s in our southern counties.
A more substantial precipitation event is expected for the middle
week period. There is a chance for mixed precipitation on Tuesday
morning. Mild air is forecast to build into our region from the
south and southwest with the precipitation changing to rain on
Tuesday and Tuesday night.
Temperatures are forecast to rise into the 40s and 50s throughout
our region on Wednesday with more rain expected. The perception
may end as a bit of snow, especially up north as cold air returns
late on Wednesday night and on Thursday.
There remains some disagreement among the model guidance
regarding the expected rainfall amounts. However, there is the
potential for a period of moderate to heavy rain. There may be
some flooding as the rainfall combines with snow melt and as ice
begins to move on area waterways due to the mild temperatures.
Cold dry air is anticipated to return for the end of the week.
Aviation /16z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
VFR conditions will persist through the taf period. Only high
level clouds expected today into the first half of the night.
Clouds will thicken and lower toward daybreak but remain VFR.
Winds will be northwest-north around 5-10 knots today, before
becoming light and variable/calm this evening and overnight.
Sunday...conditions lowering to MVFR and IFR, especially in the
afternoon, due to the arrival of a wintry mix of precipitation.
Sunday night...IFR and MVFR conditions in mixed precipitation.
Low level wind shear is possible with the potential of a
southwesterly low level jet around 45 knots overhead.
Monday...conditions improving to VFR.
Monday night...mainly VFR.
Tuesday...conditions lowering to MVFR and IFR, especially in the
afternoon, as rain builds into our region. The rain may begin as a
Tuesday night and Wednesday...MVFR and IFR conditions in rain.
The rain may be moderate to heavy at times.
sub-Small Craft Advisory conditions will persist across the area
today into tonight as high pressure builds across the waters.
There will be some light freezing spray for the first half of the
day when there is a steady north-northwest wind, before winds
become light and variable late today into tonight.
Sunday and Sunday night...no marine headlines are anticipated.
Monday and Monday night...a Small Craft Advisory may become
necessary due to a gusty northwest wind.
Tuesday and Tuesday night...no marine headlines are anticipated.
Wednesday...a Small Craft Advisory may be necessary due to a
gusty southwest wind.
two precipitation events are expected during the extended period,
one on Sunday afternoon into early Monday morning and a second
one on Tuesday afternoon into Wednesday night.
The initial event looks to be one with snow or mixed wintry
precipitation. The second event on Tuesday night into Wednesday
night looks to be on the liquid side with temperatures well above
freezing after an initial wintry start. Although this second event
is about 4 days out, we wanted to highlight that some of the
solutions we're seeing are producing locally heavy rainfall.
The combination of a brief warm up on Wednesday, locally heavy
rain, melting snow, a frozen ground, above normal ice in creeks,
streams, and rivers could lead to increased runoff and flooding.
Increased flow 0n area creeks, streams, and rivers could also
start to move ice, and in a worst case scenario, create
restrictions or jams.
Again, this second event bringing warmth and rain is about 4 days
out. Things can change. Continue to monitor forecasts. Keep in
mind that snowmelt and warmth, by themselves, typically don't
cause flooding. How much rain we get will be the determining
min temperature records for Sat/28th.
Por / site / Feb 28
1872 / kphl / 9 1934
1874 / kacy / 2 1934
1894 / kilg / -5 1934
1922 / kabe / -10 1934
1869 / krdg / 3 1934
1865 / kttn / 1 1934
1948 / kged / 8 1950
1901 / kmpo / -15 1907
Kacy rer for 3/1 is 5 in 1980 and kttn 8 in 1972.
Note: * indicate and other years.
Note: por = period of record, the year official climate observation
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.
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) 25.4(1895)
1874 / kacy / 21.6(1979) 23.6(1934) 23.8(1978) 24.9(2015) 25.5(1875)
1894 / kilg / 20.2(1934) 22.1(1979) 22.7(1978) 24.7(2015) 24.9(1936)
1922 / kabe / 16.6(1934) 19.0(2015) 20.4(1979) 21.6(1936) 22.0(1963)
Per the above table, Abe is easily on track for the second coldest
February, both Acy and ilg 4th coldest, and phl the sixth coldest
projected at 25.5f (not shown in The Table above).
The following is a table of the ***projected*** mean February 2015
temperatures (f) and departures from normal. January 2015 mean
temperatures are also included for comparison purposes.
Por / site / Feb mean(f) / Feb normal(f) / Feb dep (f) / Jan mean(f)
1872 / kphl / 25.5 / 35.7 / -10.2 / 30.9
1874 / kacy / 24.9 / 35.3 / -10.4 / 30.2
1894 / kilg / 24.7 / 35.1 / -10.4 / 30.3
1922 / kabe / 19.0 / 30.7 / -11.7 / 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
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 on average about
2 to 3 degrees warmer than January. The Converse is shaping up to
be the case for February 2015, as mean temperatures will be 2 to 3
degrees below those observed in January.
The following is for any meteorological winter month, not just
January or February.
Also of interest, this would also be the second or third coldest
monthly mean temperature on record at Allentown since records
began in 1922, with February 1934 being the coldest! Our other
sites rank as follows:
Philadelphia projects around 12th coldest monthly mean since
records began in 1873.
Atlantic City around 7th coldest monthly mean since records began
Wilmington has missing data in its database (1897-1916), and so
we don't focus as much attention on that record.