Area Forecast Discussion
Issued by NWS Mt. Holly, NJ-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KPHI 130555
Area Forecast Discussion
National Weather Service Mount Holly NJ
1255 AM EST Fri Jan 13 2017
A cold frontal boundary will move into region tonight and settle
south of the region for the weekend. High pressure will also
build into the Great Lakes this weekend and move eastward through New
England on Monday. Another low pressure system will track from the
Southern Plains into the Great lakes for the early and middle part
of next week.
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
-- Changed Discussion --The cold front is right on our western doorstep and will continue
to push through our area, reaching the I-95 corridor overnight
and coastal locations just before sunrise.
The showers have started to fall apart as they push towards the
coast but a few scattered showers will continue to over the next
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.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/...
Minor adjustments were made to the temperatures for Friday based
on the latest guidance. High temperatures for the calendar day are
likely to occur prior to the fropa (around or just after
midnight). For the daytime tomorrow, CAA will mostly offset
daytime heating, so temperatures will generally remain steady
during peak heating. Daytime highs range from the mid 30s in the
southern Poconos to the mid 50s in southern Delaware.
As the cold front progresses south of the area tomorrow, breezy
northwest winds will develop across the area. Temperatures will
struggle to climb from early morning readings, and daytime high
temperatures will likely be well below readings seen at midnight.
Skies will rapidly clear after cold frontal passage, but this will
be short-lived as the next vort max in the Ohio Valley begins to
approach the region, with associated upper-level lift increasing.
High clouds are expected to move into the region by late in the
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Friday night through Monday:
High pressure will be located over he Great Lakes with waves of
low pressure moving west to east along a frontal boundary in the
Mid- South. Moisture will ride north of the boundary as well
leading to the development of overruning light precipitation with
each wave of low pressure.
The first area of low pressure will track to our south in the
Saturday timeframe. Right now it appears the best lift for light
precipitation development will be across northern Maryland into the
Delmarva. This light precipitation is likely to break out from
southwest to northeast on Saturday. However, a fairly substantial
dry layer around 3,500 feet up in atmosphere will likely mean virga
will occur for a while across the region for a good portion of the
day. A sharp gradient of where precipitation occurs over northern
part of the forecast area will likely be present as well.
High pressure will start to shunt the overruning moisture along the
boundary further south allowing for clearing conditions over most of
the region with continuing periods of light precipitation in Delmarva
through Sunday night. The frontal boundary will then surge
northward as a warm front Sunday night and Monday with a chance
for some additional light mixed precipitation.
Precipitation type as has been all winter gets a little more
complicated. Typical model bias at this range is for the data to be
cold in the mid-levels and to warm at the surface. Overall, these
biases lead to higher prospects of ice as we get closer to an event.
The NAM and GFS are more prominent with a warm layer surging
toward Philly and ACY in the 850-925 mb range with the ECMWF only
taking the warm layer into the Delmarva. This warm layer would
allow for sleet and freezing rain to mix in with the light snow.
Temperatures as well could rise a few degrees above freezing in
Delmarva allowing for a change to rain.
Right now total precipitation looks to be around a tenth of inch
through Saturday night from a Reading to Toms River line and points
south. A few hundredths of an inch of additional precipitation currently
looks to fall for the remainder of the weekend into Monday.
Around an inch of snow could fall on a Reading to Toms River with
lower amounts further south due to mixing. Minor ice accumulations
could occur throughout the weekend as well.
Temperatures should be in the 20`s and low 30`s through Saturday,
at or a little cooler than MET/MAV/ECMWF and then fairly close to
the model data for the remainder of the weekend. Will have to
watch to see how long it takes to scour out the low level cold in
the Southern Poconos and Northwest New Jersey on Monday.
Monday night through Thursday:
A low pressure system will track into the Great Lakes with a
surge of warm air advection. A CAD situation is showing up on the
models on Tuesday which will likely delay the warm-up till
A chance of rain showers is present as the warm front
on tuesday, with additional chances of rain Wednesday and Thursday
with a front nearby and warm moist air being advected northward.
Temperatures have the potential to be 20 degrees above normal
Wednesday and Thursday with a frontal boundary to our northwest.
Long term ensemble guidance is likely underdoing the warm-up at
this point given biases to stick closer to climatology that far
Longer term: Temperatures should continue well above normal in
the 8-14 day as a trough moves into the west coast and Alaska (+
EPO, - PNA) that will result in height rises along the east coast
bringing warm air northward.
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Gusty SW winds have started to diminish this evening as the cold
front approached from the west. Fropa is expected to occur from
NW to SE between 06Z- 09Z and is marked by a wind shift out of the
Some light showers continue to move through the area in advance of
the fropa. The showers have been decreasing in coverage over the
past couple of hours but a very brief shower remains possible
through 08Z. Some MVFR ceilings may develop just in advance of and
along the fropa but should quickly clear out of the terminals as
the wind direction shifts to the northwest. Best chances for MVFR
conditions are at KABE and KRDG where steadier rain was reported
earlier this evening.
Today should be VFR with breezy northwest winds 10-20 kts with
gusts up to 25 kts. Winds will gradually diminish by late in the
afternoon, then we should lose the gusts toward sunset. Ceilings
are expected to lower towards the end of the TAF period as the
next system arrives.
Saturday through Saturday night: Visibilities and ceilings
lowering to MVFR/IFR Saturday into Saturday night due to light
snow developing. Possibly a wintry mix for KILG, KACY and KMIV.
Winds 10 knots or less.
Sunday and Sunday night: Lingering light mixed precipitation for
KILG, KMIV and KACY with MVFR/IFR, improvement elsewhere. Winds
under 10 knots.
Monday through Tuesday night: MVFR/IFR throughout most of this
period. A light wintry mix Monday morning changing to light rain.
Winds under 10 knots.
-- End Changed Discussion --
Will likely let SCA expire at 10 PM for the DE Bay. SW winds had
increased this evening with the arrival of the SW low-level jet.
Winds at SJSN4 were around 25 kt at 9 PM. The low-level jet will
progress downstream of the area over the next hour or two and
wind speeds should accordingly decrease to below SCA criteria.
The SCA headline for the coastal waters was left as is but the
wording was updated to reflect the higher wave heights that are
have been observed early this evening (generally 5-7 ft; buoy
440025 reported 8.5 ft late this afternoon). Wind grids were also
tweaked a bit to cap peak gusts in the 24-27 kt range (previously
was 28-32 kt) this evening. As discussed previously, SW winds will
weaken overnight and may drop below 25 kt for a period late tonight.
A wind shift from the NW is expected behind a cold front early in
the morning. NW winds will become gusty again during the day on
Friday. The strongest wind gusts of 25-30 kt are most likely to
occur mid to late morning. The SCA is in effect until 6 PM Friday
for the coastal waters but it may be able to be cancelled earlier
as the winds gradually weaken during the afternoon. Seas are
forecast to drop below 5 ft by the afternoon as well.
Sub-SCA conditions expected. Highest winds will be Saturday,
around 15 knots on the ocean. Seas will fairly low of only a foot
or two throughout the period.
Model guidance continues to show low tides tonight approaching blow
out tide thresholds. With the full moon today, astronomical low
tides will be between -0.75 and -1.5 ft MLLW. Additionally, the
southwest winds expected before low tide tonight are not optimal
for blow out tides. Therefore, we still expect the total water
level to stay above blow out tide thresholds.
Record high temperatures occurred today at Atlantic City,
Wilmington and Reading (tied). Record Event Reports (RER) have
been issued with some more details. Allentown and Georgetown
missed their record highs by one degree.
Another round of very warm temperatures is likely to occur next
Wednesday and Thursday but potential cloud cover and CAD may limit
the degree of the anomalous warmth. Will post records if the full
potential of the warm up looks to transpire.
-- Changed Discussion --PA...None.
MARINE...Small Craft Advisory until 6 PM EST this evening for
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