Area forecast discussion
National Weather Service Mount Holly New Jersey
255 PM EDT Tuesday may 21 2013
Synopsis...
high pressure will remain off the southeastern United States
coast through Thursday. An area of low pressure will move from the
Southern Plains to southeastern Canada through Thursday and bring
a cold front through the region late Thursday into Friday. High
pressure will then build in from the west for the Holiday weekend
this high will then gradually move offshore through Tuesday.
&&
Near term /through 6 am Wednesday morning/...
any lingering showers/thunderstorms across the northern areas will dissipate
this evening with the loss of heating. A few downpours may occur
with the activity early. Skies will be partly to mostly cloudy
early...then transition back to a low overcast along with areas of fog
again tonight. Conditions will probably remain above dense fog
advisory criteria...so we have not issued that at this time. It will remain
warm and humid again tonight with lows in the low/middle 60s north and
middle/upper 60s south. Winds light mostly from the SW.
&&
Short term /6 am Wednesday morning through 6 PM Wednesday evening/...
Wednesday will have weather similar to today. Plenty of clouds/fog in
the morning and the chance for showers/thunderstorms during the afternoon. This
activity will probably be found across most areas...unlike today where
it was restricted to the north. We will carry probability of precipitation in the chance range
for now. The Storm Prediction Center has placed the slight risk for thunderstorms to the west of
our area...so we will watch for updated overnight. Highs will be
very warm again Wednesday with temperatures in the middle 80s in most areas (except
along the shore...where readings in the upper 70s to low 80s may
occur).
&&
Long term /Wednesday night through Monday/...
the area of high pressure will remain off the Atlantic CST Wednesday night
and Thursday and southwesterly flow will continue which will keep warm weather over
the area. However, by Thu, an area of low pressure will move into
southeastern Canada. The cold front associated with this low will cross the region
Thursday night. This period looks to to be the wettest with showers, thunderstorms
and possibly some heavy rain. Its a bit too early to be certain about
any sever weather potential. It will be dependent on daytime heating
and other factors. However, it could be mitigated by the fact that
the front will be coming through after sunset. The 21/12z GFS is
the slowest model clearing things out on Friday and tries to develop a
wave along the front. None of the other models have this feature, so
am not inclined to go along for now. Fri, especially later Fri,
should see improving weather and by Sat a large area of high pressure
will push into the Midwest from Canada wand will slowly slide eastward
through the Holiday weekend.
The pgrad between the building high and the departing low over the
Canadian Maritimes will keep a decent northwesterly flow over the area on
Sat, with weakening flow as the high moves in on sun. So, at this
point, the weekend looks predominantly dry, albeit cool for late
may and with a brisk northwest wind, it will feel cooler on Sat.
Temperatures look to be warmest on Thu, with temperatures around 80 or into the
80s. Then behind the front most locations will be around 70 or
into the lower 70s for the remainder of the period. Sat looks to be
the coolest days, with many locations hovering in the middle/upper 60s.
&&
Aviation /18z Tuesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
It has been taking a long time for the patch of St across
miv-phl-ilg to finally dissipate...but it appears that it will by
middle afternoon. VFR conditions expected into the evening...before a
return back to low MVFR/or IFR conditions again tonight. A few scattered
showers or maybe a thunderstorm could affect kabe later this afternoon...but
the probability looks too low to include in the tafs at this time. Amds possible.
Winds should stay mostly SW into the evening and then go mostly
light S overnight. Wednesday...a slow return to VFR by middle-morning then
scattered showers/thunderstorms possible during the afternoon.
Outlook...
Wednesday night through Thursday night...mainly VFR. MVFR, possibly IFR,
conditions possible in any showers and thunderstorms or periods of
heavy rain. Wind will shift from SW to northwest behind cold front passage late Wednesday
night/early Thursday morning. High confidence on the overall details. Low
confidence on the fact that all sites will see MVFR/IFR and
timing.
Friday...mainly VFR with a chance of showers mainly in the morning.
High confidence.
Sat-sun...VFR conditions expected. A brisk northwest wind on Sat of 15-20
knots. High confidence.
&&
Marine...
winds have been mostly SW/S across the waters today with speeds
mostly 10 to 15 kts. Seas have been mostly around 3 feet on the ocean
and 1 to 2 feet over the del Bay. Conditions should remain sub-Small Craft Advisory
tonight and approach Small Craft Advisory later Wednesday. Winds will increase
Wednesday...but with the warmer air and cooler seas...the winds/wave
guidance may be too high. We opt to keep the seas at 3 to 4 feet for
Wednesday and hold the winds below Small Craft Advisory flag levels. A few g 20-25 are not
out of the question later Wednesday. Scat showers/thunderstorms expected Wednesday.
Outlook...
high pressure anchored off the southeastern United States coast will
bring a prolonged south to southwest flow for Wednesday night through
Thursday. As this flow strengthens with a cold front approaching from the west
on Thu, winds and seas will gradually increase. Therefore, seas
and wind could be at or above Small Craft Advisory criteria by the start of the outlook period. A
Small Craft Advisory may be needed for this period on the ocean front.
However, with very warm air over the relatively cool ocean and
wave watch overdoing heights of late, have decided not to Post
anything at this time. There will also be some showers/thunderstorms Wednesday night into
Thursday along and ahead of the cold front passage.
The cold front will cross the area waters late Thursday into Friday.
Both winds and seas will start to subside and should fall below
Small Craft Advisory criteria. Winds and seas should remain below criteria through
the Holiday weekend as high pressure builds across the region.
&&
Phi watches/warnings/advisories...
PA...none.
New Jersey...none.
Delaware...none.
Maryland...none.
Marine...none.
&&
$$
Synopsis...nierenberg
near term...O'Hara
short term...O'Hara
long term...nierenberg
aviation...nierenberg/O'Hara
marine...nierenberg/O'Hara
