Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
1232 am EDT Wednesday Jul 23 2014
high pressure will continue to move eastward tonight allowing for a
better return flow tomorrow ahead of a potent cold front. The front
should move through later on Wednesday into Thursday morning. High
pressure will fill in behind the departing front through the first
half of the weekend before a complex system approaches Sunday
spilling into the new work week.
Near term /through today/...
the 1230 am further estf update has considerably reduced the fog
in the forecast and delayed it. Too much tt/dew point spread at 04z.
Fair early this morning...patchy fog toward 10z...mainly northwest New Jersey.
Used the ups crossover tool which is more conservative than the
Today...little change in philosophy. Model guidance states widespread
lower 90s (near 18c 850 mb and 925mb hottest temperatures are just west
and northwest of our forecast area). Poconos and immediate Atlantic shore
a bit cooler.
Heat index upper 90s. No heat advisory in this continuing Summer bereft
Have withdrawn morning thunder in east PA and northwest New Jersey.
Thunderstorms probably restricted to northwest New Jersey and NE PA after 21z...possibly
a second cluster crossing ches bay? Tt 48+ swi -2 ki increasing to
38c vicinity pocs and east Virginia. Appears to be a see text case...unlikely
severe through 00z due to lack of bulk shear...500mb winds under 30
knots and MLCAPE closer to 1600j.
Note that there should be cumulus fields forming this morning over nnj
in a leading edge area of ki 33c but with little or no primary
forcing am not expecting to yield any late morning thunderstorms in nnj as
this lead area of instability shoves east-northeast to Li by 18z.
Probably a 50 50 blend of the 00z/23 NAM/GFS guidance in the 330
Short term /tonight/...
slow southeastward progress of the cold front into the unstable airmass
should yield bands of thunderstorms into the early night but not necessarily
widespread. One or 2 thunderstorms could be severe but bulk shear is marginal
at worst for severe and only the tt and some cape allow for modest
isolated severe potential.
Precipitable water 1.8 inches offers a chance of narrow paths of 2 inch rains
beneath the biggest storms.
50 50 blend of the 00z/23 GFS/NAM guidance in the 330 am issuance.
Long term /Thursday through Tuesday/...
the base of the trough begins to flatten out by Friday, though not
entirely becoming zonal. This yields slightly below normal
temperatures and decreased chances for convection given a drier
airmass in place. Still a bit uncertain about the Saturday evening
timeframe as some of the operational guidance swings a piece energy
through the base of the trough which could touch off a couple
stray/isolated showers...better east than west with better moisture
pooling and seabreeze interaction.
Ridging builds into the west sending stronger shortwaves of energy
into the trough overhead allowing for another bout of deeper
troughing. Expect unsettled weather through the remainder of the
longterm as a series of embedded waves pushes through aloft touching
off showers and thunderstorms.
Aviation /06z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Early this morning before 12z...primarily VFR with scattered clouds at or above
4000 feet. Patchy 2 to 5 Michigan fog in the Countryside taf locations
but confidence is less than it was at this time ydy. Temperature-dewpoint
spreads at midnight are just too large. Light S-SW wind.
Today after 12z...VFR scattered at or above 5000 feet. Briefly broken ceilings near 5000
feet vicinity kabe and krdg this afternoon and slight chance of a thunderstorm there
after 22z. SW wind g 17 knots this afternoon most taf locations.
Tonight...VFR ceilings with a better chance of brief IFR conds in
thunderstorms. Light SW wind shift north toward morning when patchy IFR St/fog
might form in the frontal zone or where it rains this evening.
Thursday...MVFR and IFR conditions at times in showers and thunderstorms.
Patchy fog Thursday morning.
Thursday night through Saturday...mainly VFR.
Sunday...sub-VFR possible in scattered showers and thunderstorms.
no headlines through Wednesday night.
Mainly S-SW wind g under 20 knots shift to north toward dawn Thursday.
Wave heights on our ocean waters should be 2 to 4 feet. Waves on
Delaware Bay are expected to be 2 feet or less.
Scattered thunderstorms tonight.
Thursday through Sunday...high pressure overhead will keep seas and
winds below Small Craft Advisory criteria.
near term...drag 1231a
short term...drag 1231a