Area forecast discussion 
National Weather Service Mount Holly New Jersey 
936 PM EDT Tue Sep 27 2016 


Synopsis... 
a frontal boundary will stall offshore through Wednesday. Low 
pressure systems over the Great Lakes and southeast United States are 
expected to drift toward the region for the later half of the 
week, before finally lifting into New England for the weekend. 


&& 


Near term /until 6 am Wednesday morning/... 
an upper air analysis showed a strong closed low centered in the 
upper Great Lakes region. There are numerous short waves rotating 
around this closed low, however they are west of our area. 
Meanwhile, a frontal zone is stalling to our south and east. 


For tonight, our region remains generally between the above systems. 
There has been decent drying across much of the area today in the 
wake of the aforementioned front. The main push of the drying has 
slowed though toward the coast as dew points are higher compared to 
farther inland. In addition some clouds lingering closer to the 
coast, although satellite trends are showing more breaks occurring. 
We will maintain some clouds for these areas, although at least some 
clearing should occur for a time overnight. The bulk of the showers 
have moved farther offshore, and the rest of the night may not 
feature much of any showers from near the coast and across the 
marine area. As a result, we generally went with a dry forecast. 


A mainly clear sky for many areas combined with light winds will 
allow temperatures to radiate decently, especially across the 
northern and western areas where dew points have been much lower. It 
is these locations where patchy fog may develop toward morning, and 
therefore we included a mention for low-lying areas (river valley's) 
for now. Not anticipating dense fog, but there may be a few spots 
where the fog reduces the visibility to less than a mile. 


&& 


Short term /6 am Wednesday morning through 6 PM Wednesday/... 
the closed upper low will become entrenched over the southern Great 
Lakes on Wednesday. As it does, surface low pressure will develop 
along that stalled frontal boundary over the Tennessee/Ohio valleys during 
the day Wednesday, and will begin to slide along the boundary to the 
north and east. 


Both the GFS and the NAM are in decent agreement in holding off 
precip for the area until late in the day. Most of the day Wednesday 
should be mainly dry for most areas, but with a developing onshore 
flow, and increasing low level moisture, can expect lower clouds to 
develop starting in the late morning. Cannot rule out some patchy 
drizzle during the day, but areas most impacted by any showers will 
be southern areas, and then the showers slowly work their way up to 
the north late in the day. As of now, pops were kept on the low 
side, however did raise them to likely late in the afternoon across 
the far south. 


&& 


Long term /Wednesday night through Tuesday/... 
an unsettled period is in store for the first part of the extendd 
pd. 


High pres will remain over ern Canada and new eng, with a large 
upr low spinning around to our SW. One area of low pres, moves by 
to the W Wed night into Erly Thu. This feature has the potential 
to bring the heaviest, steadiest rain to the area durg this pd. 
However, guid continues to suggest that the highest qpf will be to 
our W. 


As is often the case with upr lows, there will be an abundance of 
clouds and periods of rain, but determining when and where it will 
rain is difficult and the mdls are disagreeing. 


Durg the day Thu, there cud be a break, especially over nrn areas. 
Mdls diverge considerably Thu night into Erly Fri with the GFS 
remaining drier and the European model (ecmwf) and NAM wetter. 


Later Fri into Fri night could see another lull. 


Over the weekend, the upr low begins to fill and lift out and 
precip chcs will gradually decrease. However, there will at least 
be some chc on Sat, especially N and psbly into sun before all 
rain chcs come to an end Erly next week. 


Temps look to be around nrml. Quantitative precipitation forecast values could reach 2 to psbly 3 
inches on the lwr Delmarva and less elsewhere. 


&& 


Aviation /02z Wednesday through Sunday/... 
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg, 
kmiv, kacy and surrounding areas. 


Overnight...VFR overall, although a ceiling will linger for 
awhile longer at or near miv and Acy. Local fog toward morning may 
result in MVFR/IFR visibility for a time, however confidence is 
not all that high for most areas therefore just included light fog 
at miv for now. Light south-southwest winds, becoming light and 
variable to calm at most terminals. 


Wednesday...VFR ceilings developing in the morning, then lowering to 
MVFR from southeast to northwest during the course of the day. An 
onshore flow is expected to increase, therefore lowering ceilings 
may occur fairly quickly. A few showers are possible especially in 
the afternoon, with even some drizzle possibly developing for some 
areas. East-northeast winds 3-6 knots to start, then increasing to 
10-15 knots in the afternoon. 


Outlook... 
Wed night thru Thu...MVFR/IFR conds likely with shra, some psbly 
hvy. MDT confidence. East-northeast wind around 20 to 25 kts on Thu for kacy 
and psbly kmiv. 


Thu night thru Fri...some improvement is psbl, but MVFR is likely 
with lower conds in any rain showers. East-northeast wind 20 to 25 kts for kacy. Low 
to MDT confidence. 


Sat thru sun...mainly VFR, but some lower conds psbl in sct 
shwrs. MDT confidence. 


&& 


Marine... 
light winds this evening, becoming NE 5-15 knots after midnight. Seas 
will remain mostly 2-4 feet. 


On Wednesday, winds and seas will begin to ramp up as low pressure 
approaches from the south and west. Small Craft Advisory conditions 
with winds gusting to 25 knots and seas building to 5 feet will develop 
over northern ocean waters Wednesday afternoon, so a Small Craft Advisory has been 
issued for those waters for Wednesday afternoon. 


Outlook... 
a gale watch for the northern coastal waters and Small Craft Advisory elsewhere 
has been issued for Wed night thru Thu for increasing east-northeast wind and 
seas. Confidence was not high enough to extend gale watch further 
S. A prolonged sca will likely be needed into at least Saturday. 
Seas will build into Fri and could reach 9 to 10 feet before 
decreasing. 


Rip currents... 
there is a moderate risk for the formation of dangerous rip 
currents Wednesday. This is due to the combination of an 
increasing onshore wind and building seas. 


&& 


Tides/coastal flooding... 
spotty minor tidal flooding on the oceanfront is possibile with 
the Thursday and Friday high tidal cycles. 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...none. 
Delaware...none. 
Maryland...none. 
Marine...Small Craft Advisory from 6 PM Wednesday to 8 PM EDT Thursday 
for anz430-431-452>455. 
Gale watch from Wednesday evening through Thursday evening for 
anz450-451. 
Small Craft Advisory from 1 PM to 6 PM EDT Wednesday for 
anz450-451. 


&& 


$$ 
Synopsis...nierenberg 
near term...gorse 
short term...mps 
long term...nierenberg 
aviation...gorse/nierenberg 
marine...nierenberg/mps 
tides/coastal flooding... 



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