Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
353 am EDT Sat Apr 25 2015
weak high pressure covers our area early today. Low pressure over
the lower Ohio Valley will pass off the North Carolina coast Sunday.
That low becomes part of large low pressure circulation over the
northwest Atlantic early next week. A low pressure system over the
northern Gulf of Mexico Tuesday night emerges off the southeastern
Seaboard late Wednesday and Thursday and heads northeast.
Near term /until 6 PM this evening/...
330 am package: not much change in the frost/freeze hazard as
radiational cooling varies based on the surface wind stirring but
overall...the advisory/warning is reasonable and verifying.
Today...variable high cloud cover. The thicker skycover from far
southeast PA and snj southward. Sprinkles may develop toward 6 PM over
Talbot/Caroline and southern Sussex counties on the SW edge of our
forecast area. Forecast temperatures today were a 1/3rd blend of the
00z/25 GFS/NAM MOS and 00z/25 European model (ecmwf) 2m temperatures. The European model (ecmwf) is quite
cool under the clouds over the Delaware-Maryland-Virginia and have modified the
NCEP MOS downward there. Warmest temperatures in our forecast area today
should be in northern New Jersey where there should be more sunshine.
A nice day with much less wind than the previous Wednesday-Thu-Friday
Daytimes temperatures will be warming a bit except the Delaware-Maryland-Virginia where it
will be chilly today and maximum temperatures almost 15 degrees below
normal while maximum temperatures around Allentown and Mount
Pocono northeastward through nnj should only be 8 to 10 degrees below
A weak wind shift boundary will be forming just to our north late
in the day with westerly winds gusting to 15 miles per hour during the
afternoon in PA and nnj but sea breezes should develop coastal New Jersey
and coastal Delaware. Winds on the Delaware-Maryland-Virginia will be light where less
mixing is expected due to heavier skycover.
Short term /6 PM this evening through 6 am Sunday/...
tonight...thick high cloud along and south of I-78, with the northern
portion of the forecast rain shield a blend of HPC qpf, 50 50
00z/25 NAM/GFS MOS and multi model .10 in 6 hours. That means mainly
the southernmost 40 miles of our cwa, Talbot County, Queen Annes
and Caroline counties in Maryland and Sussex County de, possibly Kent
County Delaware and possibly the southern tip of New Jersey. This cloud cover today
and cloud cover/rain tonight is associated with the low redeveloping
near the NC coast. A wind shift from light west to north-northeast
progresses from north to south through our County Warning Area during the night.
Patchy frost is in the forecast north of I-78 tonight. No new frost advisory
at this time due to the uncertainty of the northern edge of thick cloud
cover. It already froze up there this morning so early susceptible
blooms were probably damaged.
Long term /Sunday through Friday/...
a low pressure system will be moving offshore Sunday morning and
its associated clouds and light rains will be affecting the southern
parts of our area. Some light rain will pull away by evening with
perhaps up to a tenth of an inch possible. Elsewhere...partly to
mostly sunny north and central areas with temperatures near
Cooler air arrives for Monday and Tuesday as the large upper low
offshore rotates a few short waves and surface troughs across the
area. Scattered showers are expected Monday with chance probability of precipitation. Drier air
arrives Tuesday...but still a slight chance for a shower far north.
Temperatures will run several degrees below normal Mon/Tue...with
Tuesday likely the milder day.
The European model (ecmwf)/GFS models both show another surface/upper low strengthening
across the southeast states and moving northeast...just east of
our area. It appears to be another glancing shot of clouds and
rains S/east for Thursday and into early Friday. Any changes with the track
could bring some heavier rains to the area. We have just used the
wpf probability of precipitation for now...mostly chance (thu) and slight chance (thu night).
Temperatures will return to near normal for the middle/late part
of next week.
Aviation /08z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Through 12z...VFR clear with scattered-broken clouds at or above 15000 feet arriving
southeast PA and S New Jersey southward after 09z. Light north northwest wind.
Today during the day...sct-bkn at or above 15000 feet may briefly thin late
in the day. Light west - northwest wind becoming west midday with
gusts to 15 knots possible during the afternoon in New Jersey/PA but seabreezes
develop along coastal sections middle and late afternoon.
Tonight...ceilings at or above 10000 ft, especially after 03z/26. A sprinkle
possible kphl/kilg/kmiv kacy but not in the forecast at this time. It may be
too dry in the layer under 8000 feet. Light west wind shifting north-NE
during the night. Please see tafs for timing details as a wind
shift boundary sags southward.
Sunday...mainly VFR conditions, as any sub-VFR in rain to start
across southern areas will improve back to VFR.
Monday...mainly VFR conditions; although, some isolated showers are
possible. Gusty north to northwest winds, with gusts to 20 knots.
Tuesday and Wednesday...mainly VFR expected; although, conditions
may deteriorate late Wednesday night depending on the timing and
track of a possible coastal low pressure.
discontinuing Small Craft Advisory at 330 am. Sub Small Craft Advisory conditions through tonight
with northwest to northeast winds this morning becoming westerly
midday then sea breezes during late afternoon. Light winds tonight
becoming north-NE late.
Sunday/Sunday night...sub-sca conditions. Rain south.
Monday/Monday night...mostly aub-aca but some wind gusts around 25
kts possible. Scattered showers.
Tuesday through Wednesday...mostly sub Small Craft Advisory.
dry conditions are expected once again today, with minimum relative humidity
values once again ranging from 20 to 30 percent. However, winds
will be considerably lighter, with gusts generally near or below
15 miles per hour through the day. No action at this time.
PA...freeze warning until 8 am EDT this morning for paz060>062-
Frost advisory until 8 am EDT this morning for paz070-071.
New Jersey...freeze warning until 8 am EDT this morning for njz001-007>010-
Frost advisory until 8 am EDT this morning for njz014-023>026.
Delaware...frost advisory until 8 am EDT this morning for dez001>004.
Maryland...freeze warning until 8 am EDT this morning for mdz008.
Frost advisory until 8 am EDT this morning for mdz012-015-019-