Area forecast discussion
National Weather Service Mount Holly New Jersey
941 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 /until 8 am Wednesday morning/...
930 pm: cut back further on showers northwest portion of the forecast area tonight. Fog
is in the Countryside forecast but not necessarily the urban centers
(fogger tool I think is better than the conservative crossover).
However sref probs even lower visibility to less than 1 Michigan in the city
by 09z.
So MO clear skies give way to low overcast late. There is a small
chance that convection in northwest PA and S New York state at 01z will develop east-southeastward
and graze the Poconos 05z-08 but for now... model signals are dry
for this evening and without cumulus...its difficult to have a shower.
Warm and humid with temperatures much above normal for this time of
year...and more typical of a middle Summer night.
&&
Short term /8 am Wednesday morning through 6 PM Wednesday/...
Wednesday will have weather similar to today. Plenty of clouds/fog in
the morning and a chance for showers/thunderstorms during the afternoon...mainly
east PA. Its possible there will be isolated showers in the Delaware valley
during midday but for the most part convection should be middle or
late afternoon...if any within our County Warning Area.
Storm Prediction Center has placed the slight risk for thunderstorms to the west of our area...so
we will watch for the update early Wednesday morning. Highs will be
very warm again Wednesday with temperatures in the middle to upper 80s in most areas
(except along the shore...where readings in the upper 70s to low
80s may occur). There is still a small chance the temperature nudges 90f
vicinity of krdg or kabe or near ksmq in the afternoon where the hottest
temperatures should occur...again presuming no convection in the 14z-20z
time frame.
Cloud cover will probably very slow to thin over southeast New Jersey and S Delaware on
Wednesday...possibly not clearing off until middle afternoon.
SW wind g to 15 miles per hour Wednesday afternoon.
&&
Long term /Wednesday night through Tuesday/...
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 /02z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Tonight...VFR cirrus this evening. Light south-southwest wind. Conditions
likely to become IFR or LIFR in St/fog after 07z.
Wednesday...after a probable IFR condition start at 12z...a slow return to
VFR by middle or late morning with scattered-broken clouds at or above 3500 feet in the
afternoon and a shower or thunderstorm possible during the afternoon...mainly
vicinity krdg or kabe. SW wind gust to 15 knots in the afternoon.
The IFR ceilings may be very slow to lift vicinity kmiv and kacy not lifting
to MVFR ceilings until midday Wednesday and clearing around middle afternoon.
There is a small chance for a shower in the Delaware valley vicinity kpne/kphl
around 15-16z Wednesday per long range RUC-rap but an unlikely occurrence.
Feeling is the models have a slight wet bias and are overdoing convective
potential in this SW flow summerlike scenario in our County Warning Area.
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...
guidance running a solid 1 foot or more too high recently due to
warm air advection over cooler water.
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 will probably 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.
&&
Climate...
knowing the first 20 days of may temperatures have averaged almost
spot-on normal for almost every climate site in our area...we
projected the remainder of the month for kphl. We used the kphl
maximum/mins for the next 7 days, and then the ftprha phl 2m maximum/min
temperatures beyond through the 31st.
The projected monthly average temperatures is in the normal range...slightly above
but within 1/2 degree of normal.
We discuss temperatures tonight since we're coming into the Memorial Day
weekend which will be cool and less favorable for ocean swimming but
guidance is showing increasing chances for a warmer than normal
pattern developing here between roughly the 30th of may well into
the first week of June.
Sst's are already generally several degrees above normal. If we
advance into a hot spell by the end of next week...we do not want
a repeat of last year when hot weather...warmer than normal waters and
seemingly benign ocean swells encouraged swimmers to take unnecessary
risks at early season "unguarded" beaches with rip current related
drownings. The dangers of rip currents are worthy of a few minutes
of dinner table discussion...especially since there is access to
the beaches for millions of swimmers over interior sections of our
area who may be less experienced with the dangers of ocean swimming.
The chances of drowning at a life guarded beach is 1 in 18 million.
Rip current awareness week is June 2 through 8.
&&
Phi watches/warnings/advisories...
PA...none.
New Jersey...none.
Delaware...none.
Maryland...none.
Marine...none.
&&
$$
Synopsis...nierenberg
near term...drag 940
short term...drag/O'Hara 940
long term...nierenberg
aviation...drag/nierenberg 940
marine...drag/nierenberg/O'Hara 940
climate...940
