Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
421 am EDT Thursday may 7 2015
high pressure anchored off the northeast coast through early next
week. A low pressure is forecast to lift through the Great Lakes
region early next week and toward the northeast by Wednesday,
pulling a cold front to the East Coast around Tuesday.
Near term /until 6 PM this evening/...
a rather quiet pattern is on tap at least for the near term. Today,
the middle and upper level ridge begins to build east. The associated
subsidence would suggest a warming trend for today, with highs at
least a few degrees higher than yesterday. However, this will be
somewhat tempered by the onshore flow which is expected for at least
the first half of the day. In the end, think the clearing skies and
subsidence will have more of an impact, so have stayed close to the
mav and met guidance.
Short term /6 PM this evening through 6 am Friday/...
Ridge axis moves directly overhead of the region. At the surface, a
ridge will result in winds slowly veering to southwesterly.
Depending on how quickly this wind shift occurs, fog is possible
over areas that hang on to the onshore flow the longest, especially
given the continued subsidence in the middle and upper levels. However,
most models show the boundary layer sub-saturated overnight, so have
held off on mentioning fog in the grids for now.
Long term /Friday through Wednesday/...
not much change to the longterm grids tonight as the pattern does
not appear to waver too much from what has been seen the past 2-3
nights. The most notable change comes towards the end of the period
as the blocking gets washed out and replaced with
troughing...temperatures drop back towards the seasonal levels.
Friday...dry day expected with ridging aloft keeping a decent lid on
the region. Temperatures will climb back towards 80f in most places
with building middle-level heights, even with a light south-southeast
Saturday - Sunday...we continue with the slight/chance probability of precipitation each
afternoon, mostly southwest-west of the metropolitan area where moisture
pooling and warmer temperatures are expected. Outside of the
diurnally driven convective showers fog/drizzle/stratus will occur
each morning across most of the region...fog may be dense at times
especially in areas with added low-level moisture from the passing
showers. Highs will climb a bit higher each afternoon into the low-
Monday - Wednesday morning...as a cool front approaches...there will
be greater moisture, lift, and instability available and therefore
higher probability of precipitation than previous days. Given a slow frontal passage with
ample Gulf/subtropical moisture and the remnants of whatever forms
(tropical or not) along the southeast coast...heavy rainfall is
possible during this time frame.
Wednesday - Thursday...generally a dry forecast is expected with
troughing having replaced the ridging/flat flow we've had in place
for several days. A drier and much cooler airmass, more seasonal,
will engulf the region.
Aviation /08z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe,
krdg, kilg, kmiv, kacy and surrounding areas.
VFR conditions are expected through the taf period. There is a very
small chance of mist/fog developing after 06z tonight. But how long
we keep cloud cover and dew point temperatures will have a big
impact on the chances for fog to develop, so have left out of the
tafs for now. Wind direction will be changing through the day, from
northeasterly currently to easterly by around 18z. By 21z, many taf
sites will be southwesterly, except kilg, kmiv, and kacy which may
stay southeasterly thanks to the influences of the Bay and sea
breezes. Still, wind speed should be light, generally near or below
Friday...VFR. Light south-southeast winds expected.
Saturday - Monday...mostly VFR. Some early morning MVFR/IFR
fog/stratus possible at most of the terminals...better chances
closer towards the coast. Southeast flow giving way to southwest
winds on Sunday. Possible afternoon showers/thunder each
afternoon...better chances across the western terminals.
winds and seas should remain below Small Craft Advisory criteria
today and tonight. Winds may shift from northeasterly to southerly
by tonight, but speeds should generally be less than 10kt.
Friday - Monday...generally a sub-Small Craft Advisory forecast with seas increasing
a bit under a persistent southeasterly flow through Saturday. The
flow then becomes more southwesterly on Sunday.