Area forecast discussion 
National Weather Service Mount Holly New Jersey 
619 PM EDT Tuesday Oct 21 2014 

broad low pressure will drift off the coast tonight. The low is 
forecast to move slowly north and northeastward reaching the 
waters off Cape Cod on Thursday night and arriving in Nova Scotia 
on Friday night. High pressure is anticipated to build into our 
region from the southwest for Friday into Saturday. A cold front 
approaching from northwest is expected on Saturday night with 
another area of high pressure following for Sunday and for the 
early part of the new week. 


Near term /until 6 am Wednesday morning/... 
what was once a better defined mesoscale convective vortex out in western Pennsylvania 
looks to be losing it luster but it should not completely wash out 
as it moves closer to our County Warning Area. The current area of activity is 
expected to increase through the late evening hours and begin to 
wane as it loses better support from the middle-level trough to our 
west. The middle- level troughing to our west dives further southward 
to our immediate west late tonight as more and more energy is 
transferred to a coastal low pressure just offshore of Delaware-Maryland-Virginia. 

We catered the probability of precipitation with likelies across our northern fringe and 
chance elsewhere, early and then bring in likely across our 
southern zones later tonight with the movement of the closing middle- 
level low and overhead energy Transfer to the coast. 

The latest radar showed some organized showers/thunderstorms and rain in northern New Jersey and 
some less organized stuff along the western periphery of our area. 
Movement is slow. Have tried to adjust probability of precipitation to account for its 
location and trends, but this was difficult, nonetheless. Also, 
had to make some adjustments to cloud cover. While most of the western 
sections of the area is cloudy eastern sections were mainly clear 
at this time. 

Gridded temperatures were a bit too warm in the real near term and needed 
to drop them a few degrees as well. 


Short term /6 am Wednesday morning through 6 PM Wednesday/... 
generally speaking the poor mans 500mb ensemble shows good 
agreement among the 12z operational models. All show the troughing 
to our west closing off tonight as multiple impulses move through 
its base over the next couple of days. As it continues to close 
off a better defined surface low takes shape just offshore of the 
Delaware-Maryland-Virginia/southern New Jersey coastline. The strongest of the middle- 
level impulses tonight dives into the base of the trough as it and 
it begins to close off but deepens the coastal low pressure. Ample 
Atlantic moisture will be in place combined with good cyclonic jet 
dynamics and divergence-q field to see categorical probability of precipitation across a broad 
portion of our eastern half with moderate rainfall expected. 

Temperatures will only be allowed into the upper-50s to maybe the 
low-60s in the southern places. The pressure gradient tightens and 
with some mixing occurring in the afternoon hours gusts could top 
out around 25 with a northerly flow...raw indeed. 


Long term /Wednesday night through Tuesday/... 
a middle level low is forecast to be located off the Delaware-Maryland-Virginia coast 
on Wednesday evening. The feature will lift slowly north and 
northeastward passing over the waters off Cape Cod on Friday 

We continue to anticipate rain for Wednesday night. The rain 
should remain fairly light in much of eastern Pennsylvania and 
northeastern Delaware. However, moderate to occasionally heavy 
rain is possible in New Jersey and Delaware, closer to the middle 
level low. 

A fair amount of lingering wrap-around moisture will remain over 
our region on Thursday. We are anticipating a cloudy and damp day 
with a northwest wind and occasional light rain. We have gone with 
the low end of the temperature guidance. High temperatures should 
be mainly in the 50s in our forecast area. 

Gradual drying is expected from southwest to northeast during the 
course of Thursday night and Friday as the middle level low continues 
to move away from our region. Temperatures should begin to ease 
back toward normal levels for late October. 

A short wave rotating around the middle level low is forecast to 
pass overhead on Friday night. Another middle level short wave from 
the northwest is expected for Saturday night along with an 
associated surface cold front. The cold front should have limited 
moisture associated with it, so we are not anticipating any 
precipitation at that time. Temperatures are forecast to be near 
normal over the weekend. 

Ridging at the surface and aloft are anticipated for Monday and 
Tuesday with a mostly clear sky and slightly above normal 


Aviation /22z Tuesday through Sunday/... 
the following discussion is for kphl, kpne, kttn, kabe, krdg, 
kilg, kmiv, kacy and surrounding areas. 

Tonight...VFR to MVFR/IFR. Light westerly flow expected with 
showers overspreading from west to east before shutting off late 
this evening. Isolated thunder possible through late this evening 
but not confident on placement so left out of tafs...better chance 
further east. Start to see MVFR/IFR ceilings and visibilities as low pressure 
moves nearby. Rain early Wednesday morning could be heavy at times 
and may reduce visibilities into the IFR range. Winds veer towards the 
northeast and increase towards 10 knots. Medium confidence. 

Wednesday...mostly MVFR. Rain will prevail a majority of the day, 
especially from phl eastward. Northeast winds around 10 to 15 
knots with gusts up to 25 knots...slight backing towards the north 
late in the period. Medium confidence. 

Wednesday night and Thursday...conditions varying between VFR and 
MVFR in periods of rain. 

Thursday night...mainly VFR with a chance of showers. 

Friday through Sunday...mainly VFR. 


tonight...sub-sca conditions expected tonight. Light southwest- 
west flow with showers overspreading from the west and then 

Wednesday...we upgraded to gales across the Lower Bay and 
southern two zones starting Wednesday afternoon as low pressure 
just offshore wraps up. Small craft elsewhere through the 
Thursday. Northeast winds increase to 20 to 25 knots with gusts 
into the middle-30s likely southward and low-30s northward. Seas 
increase to around 5 to 6 feet late. 

Wednesday night and Thursday...a Gale Warning is in place for the 
waters off Delaware and for the lower part of Delaware Bay. A 
Small Craft Advisory is in effect for our remaining waters. We are 
expecting a gusty northwest wind. 

Thursday night through Friday night...northwesterly wind gusts of 
25 to 30 knots are possible. 

Saturday through marine headlines are anticipated. 


Phi watches/warnings/advisories... 
New Jersey...none. 
Marine...Small Craft Advisory from 10 am Wednesday to 6 PM EDT Thursday 
for anz450>453. 
Gale Warning from 2 PM Wednesday to 11 am EDT Thursday for 
Small Craft Advisory from noon Wednesday to 6 PM EDT Thursday 
for anz430. 


near term...Heavener/nierenberg 
short term...Heavener 
long term...iovino 

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