Area forecast discussion 
National Weather Service Mount Holly New Jersey 
934 PM EDT Thursday Oct 30 2014 


Synopsis... 
high pressure over our region will shift to northern New England 
by morning. Low pressure over Ohio Friday afternoon will join 
forces with low pressure east of the Carolinas to form a strong 
storm southeast of Cape Cod late Saturday. That storm moves to the 
Maritimes Sunday. Strong high pressure settles into the Carolinas 
early next week then slips eastward into the central Atlantic next 
Wednesday. 


&& 


Near term /until 6 am Friday morning/... 
weak high pressure will continue to influence our region 
overnight. 


The daytime stratocumulus continued to dissipate this evening. We 
are anticipating few to scattered clouds during the night with a 
light wind, mainly 5 miles per hour or less favoring the north. 


Temperatures are anticipated to fall into the range from the 
middle 30s to the lower 40s toward daybreak. The low level air in 
our region is drier than it was last night, so no fog is 
expected. 


&& 


Short term /6 am Friday morning through 6 PM Friday/... 
two areas of low pressure will begin to impact our weather late 
in this period. The first one will be over the Great Lakes and 
Ohio Valley Friday with the second developing off the Carolina 
coastline. Clouds from the low pressure system to our west should 
begin to move in late in the day. Winds will shift to the 
northeast in response to the low pressure off the Carolina coast. 
This will likely allow additional clouds to advect in from the 
ocean during the afternoon. Some patchy drizzle can not be ruled 
out along the coast. Modeled 925 mb temperatures indicate the 
potential for highs in the upper 50's on Friday for phl. However 
with clouds moving in it will be hard to reach these and kept 
highs in the middle 50's with some upper 40's northwest. 


&& 


Long term /Friday night through Thursday/... 
500 mb: a high amplitude trough in the eastern United States this 
weekend moves to the Maritimes early next week while a warming 
ridge follows early next week. Another trough evolves in the 
eastern United States later next week. 


Temperatures: by the time the long term forecast period begins 
we've closed out the month of October that averaged more than 2 
degrees above normal. November starts out near normal Saturday... 
5 degrees colder than normal Sunday with wind... still nearly 5 
degrees below normal Monday but with less wind and then near 
normal Tuesday. Temperatures should average several degrees above 
next Wednesday and Thursday....maybe as much as 10 degrees above 
normal either day. 


Hazards: gale Saturday possibly lingering into Sunday. Possible 
minor tidal inundation flooding near the time of high tide 
Saturday afternoon and night but this is not likely. A small 
chance of spotty Wind Advisory conditions Sunday. 


Forecast basis: unless otherwise noted the long term period of 
this forecast is generally based on a 50 50 blend of the 12z/30 
NAM/GFS MOS for the period Friday night-Saturday night and then 
that value blended 50 percent with the 00z/30 European model (ecmwf) 2m temperatures. 12z/30 
GFS MOS comprises Sunday and Sunday night...then thereafter 
(monday onward) the 1523z/30 wpc gridded guidance which at times 
is blended 50 50 with the 12z/30 mexmos. All this was eventually 
checked against the 12z/30 European model (ecmwf) through Tuesday only, when we 
modified the NCEP-wpc guidance higher by several degrees both 
Monday and Tuesday! 


The remainder..Wednesday and beyond..of the 12z/30 operational 
European model (ecmwf) did not arrive in a timely fashion and was not used for this 
forecast. 


Precipitation probability guidance is checked against the 09z/30 
sref 3hrly probability of precipitation for .01 through 00z Monday and thereafter the 
12z/30 gefs 6hr probability of precipitation for 0.05. 


The dailies below... 


Friday night...periods of rain developing westward through 
New Jersey...possibly during the evening trick or treat time. Confidence 
on forecast details is average. 


Saturday...cooler than normal and brisk with northerly gusts 
20-30 miles per hour. Rain probable at times southeast PA through southern-central 
New Jersey and probably south onto the Delaware-Maryland-Virginia. 15z sref is drier than 
i'd like to see for Saturday. So the combination of the late 
arriving European model (ecmwf) and spread in solutions lowers my confidence on 
saturdays forecast to only average. 


Sunday...windy and maybe 5 degrees colder than normal with 
northwest winds gusts 30-40 miles per hour. Isolated Wind Advisory criteria 
possible. The GFS is more robust than the 12z European model (ecmwf) and so my 
confidence on maximum wind gust is below average. Diurnal SC with 
plentiful morning sunshine hiding behind increasing midday SC. 
There is a small chance of but as yet unmentioned...for an 
afternoon sprinkle with a secondary trough aloft passage. If the 
sprinkles materialize...it would be a snow shower in the Poconos. 


Sunday night...the frost freeze portion for our forecast area 
ends November 1 so despite the forecast of frost or freezing 
temperatures under mostly clear skies and light winds...a headline 
will not be issued. There is a chance of middle level cloud cover 
arriving around dawn. 


Monday...diminished wind and milder. Middle level cloud cover. West 
wind gust 15 miles per hour. The wpc guidance was raised by 4 degrees due to 
the much milder 12z/30 European model (ecmwf) 2m temperatures. 


Tuesday...low confidence on how much cloud cover. This should be 
a nice day. Above normal temperatures. 


Wednesday...probably still nice. Maybe a shower develops late. 
Above normal temperatures. 


Thursday...maybe a period of showers otherwise...the next trough 
and a cool front may be moving into the eastern USA. Above normal 
temperatures. 


&& 


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


VFR conditions are expected through the taf period. 


Few to scattered clouds are anticipated during the night and into 
Friday morning. An increase in stratocumulus is expected during 
the afternoon. Ceilings are forecast to be around 4000 to 5000 
feet at that time. 


A light wind at 5 knots or less should favor the north overnight. 
A north to northeast wind around 4 to 8 knots is expected for 
Friday. 


Outlook... 
Friday night...VFR ceilings may lower to MVFR ceilings late. -Shra should 
be developing over New Jersey possibly resulting in MVFR visibility as well. 


Saturday...MVFR ceilings with possible IFR conds in showers across southeast 
PA...the Delaware-Maryland-Virginia...S and central New Jersey. Northerly winds gust 20-30 
knots. 


Saturday night...conditions will slowly improve from west to east 
through the night. Gusty north-northwest winds should continue especially at 
kacy. 


Sunday...mostly VFR conditions. Northwest wind gusts 23-33kt diminishing 
at night. Ceilings near 3500 feet in the early afternoon may yield an 
isolated sprinkle (except flurry poconos?). 


Monday...VFR with broken ceilings at or above 10000 feet. West-northwest wind gusting 15 knots. 


Tuesday...VFR. 


&& 


Marine... 
seas and winds should remain below Small Craft Advisory criteria through Friday 
afternoon. However some wind gusts close to 20 knots are possible 
by Friday evening off the Delaware coast. 


Outlook... 
headlines have been issued. Timing of the onset of gale force 
gusts is still uncertain and if this gale is delayed until Saturday 
evening...I wanted an Small Craft Advisory to precede. 


The 12z/30 GFS ww3 modeled seas were increased by 2-3 feet Saturday 
through midday Sunday. 


Friday night through Sunday...winds will build into Small Craft Advisory criteria, 
and then gales, with peak gusts near 40kt possible during the day 
on Saturday. Gale conditions could continue through much of the 
day Sunday. 


Sunday night into Monday...winds should subside below Small Craft Advisory 
criteria through this period though Small Craft Advisory seas may linger into early 
monday? 


Tuesday...no headline anticipated. 


&& 


Tides/coastal flooding... 
an onshore component of the breezy to windy conditions on 
Saturday will lead to elevated water levels this weekend. Minor 
tidal flooding may occur with the high tide cycles Saturday and 
Saturday night. At this time we think it unlikely but we still are 
monitoring. 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...none. 
Delaware...none. 
Maryland...none. 
Marine...gale watch from Saturday morning through late Saturday night 
for anz431-450>455. 
Small Craft Advisory from midnight Friday night to 6 am EDT 
Saturday for anz450>455. 


&& 


$$ 


Synopsis...drag 
near term...iovino 
short term...Gaines 
long term...drag 
aviation...drag/iovino 
marine...drag/Gaines 
tides/coastal flooding...drag 












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