Area forecast discussion 
National Weather Service Mount Holly New Jersey 
554 am EDT Friday Oct 9 2015 

an area of low pressure will track to our north during today, 
however an associated strong cold front will move through our area 
this evening. High pressure will then build into our region Sunday 
and Monday. The next cold front arrives during Tuesday, briefly 
followed by high pressure Wednesday. It appears that another cold 
front then arrives late Wednesday into Thursday. 


Near term /until 6 PM this evening/... 
550 am update: added showers early today to the Maryland East Shore per 
radar nearing kbwi, withdrew fog S of Trenton and enhanced fog 
wording north of i80. Those products posted around 520 am. 

Today...fog is thinning where a deck of clouds near 5000 feet has 
invaded, with the radiational feedback warming the boundary layer 
and dissipating the fog. Remaining fog now NE of kttn and slowly 
edging north. 

After any isolated or scattered early morning showers end around 15z, 
mixed clouds and sun develop after early areas of IFR MVFR ceilings 
lift and thin by 15z. 

For svr: please monitor swody1 and mcd's as well as our office products. 
In agreement with the 0518z swody1. MLCAPE of 300-700j, not too 
shabby for October, combined with the approaching cold front should 
set off around 80 percent coverage of measurable showers and isolated 
strong thunderstorms this afternoon as depicted the hrrr/rap 12z/8 and 
00z/9 Storm Prediction Center WRF and now also expected to be modeled by the 00z/9 
Storm Prediction Center WRF and the 00z/9 NSSL WRF. Timing might be 90 minute fast 
but essentially this traverses the County Warning Area in 6 hours or a bit 
less...driven by a strong westerly 750 mb flow of 35-40 knots. 

Bulk shear around 30 knots but 35-40 knots winds at 750mb suggest 
potency. The band of showers and thunderstorms reaches the coasts by 00z. 

Precipitable water increasing from 1" now to 1.6" this afternoon...some of the 
rain will be briefly heavy. Streaks of east-west oriented heavy rains, 
may be found, especially north 2/3rds of New Jersey. 

Our forecast has chance of thunderstorm with heavy rain and strong gusty winds. 

Maximum temperatures today 78 to 83f near I-95 southeastward with SW wind gusts around 
25 miles per hour this afternoon. Temperatures at least 10 degrees above normal. 
Slightly cooler along the Waters Edge, especially Cape May County 
and of course not quite as warm in the Poconos and Sussex County 
New Jersey. 

Was surprised to see the 00z/9 European model (ecmwf) 2m temperature for 18z today lower 
to 73f from previous runs of 75-78. Thinking the 00z/9 NCEP model 
blend will be more accurate...around 80f for phl. 

So the forecast was basically a lean to warmer and wetter available 00z/9 
temperatures/dewpoints via MOS and mass fields of the NAM/GFS/ECMWF and 
then used a blended 50 50 wind from NCEP MOS. Afternoon gusts were 
increased above local tools. 

Confidence: overall above average. 


Short term /6 PM this evening through 6 am Saturday/... 
tonight...again no change from the previously written Thursday 
afd scenario. Any lingering showers and scattered thunderstorms near the cf at 8 
PM this Friday evening (mainly southeast New Jersey and the southern portion of the 
delmarva) should quickly move out to sea along the cold front. 
There might be some lagging sprinkles behind the cold front in southeast 
PA and S New Jersey this evening but essentially it dries out tonight. 

High cloud cover may remain most of the night but there will be a 
noticeable cooling and drying in the boundary layer overnight with 
northwest surface winds gusty to 20 miles per hour and becoming northerly 
toward morning. 

Confidence: above average. 


Long term /Saturday through Thursday/... 
the synoptic setup is comprised of a trough in place across the east 
Saturday, however a stronger short wave in the base of this trough 
allows for more amplification to our south. This should result in a 
closed low forming to our south during the course of the weekend and 
early next week. The next trough slides across the northern tier of 
states Monday and arrives into the northeast Tuesday, before 
relaxing some Wednesday into Thursday. We used a model blend with 
continuity for Saturday into Monday, then blended the 00z wpc 
guidance with continuity thereafter. Some adjustments were then made 
following additional collaboration with our neighboring offices. 

For Saturday...a stronger short wave at the base of the trough looks 
to result in the flow becoming cut off and therefore a closed low 
develops to our south. This should maintain at least some clouds for 
a time in the morning mainly across the southern portions of our 
County Warning Area. High pressure at the surface is forecast to be building in 
through the day with a northerly wind expected. This will help 
advect drier air southward across our area, therefore more sunshine 
should occur from north to south. It appears that enough drying 
should prevent much stratocumulus developing within the cold air advection. It will 
be much cooler, however less wind should occur in the afternoon as 
the surface high builds in. Given enough clearing and lighter winds 
at night, temperatures may near the middle/upper 30s across portions of 
the northern zones toward daybreak Sunday with possibly some frost. 

For Sunday and Monday...a chilly start to Sunday. The upper-level 
trough generally starts to weaken Sunday as ridging builds up the 
Ohio Valley, however a closed low looks to linger to our south. We 
are left with lingering high pressure at the surface Sunday before 
it weakens into Monday. The aforementioned closed low and associated 
surface low should remain south and east as it slowly moves out to 
sea Monday. This occurs as the next upper-level trough begins to 
amplify across the Great Lakes region. We are anticipating a warming 
trend during this time frame as the flow starts to turn 
southwesterly ahead of the next cold front. We maintained a dry 
forecast based on surface high pressure working in for a time. 

For Tuesday through Thursday...the model guidance overall shows a 
decent upper-level trough swinging across the Great Lakes and into 
the northeast for a time. This pushes a cold front into the area 
Tuesday. It still appears though that the main surface low tracks 
well to our north although perhaps a weak surface low develops near 
coastal New England. This leaves our area removed from the better 
large scale lift. In addition, the deeper moisture looks to reside 
offshore and therefore is more limited here for the frontal boundary 
to work with. As a result, some low probability of precipitation were left for Tuesday. A 
brief return of high pressure for Wednesday, however another system 
quickly tracking just north of the Great Lakes may send another cold 
front into our area Wednesday night into Thursday. The timing of the 
individual features is less certain this far out especially as the 
short waves may be on the weaker side. A surface cold front, perhaps 
weakening, may therefore still be lurking in our area during 


Aviation /10z Friday through Tuesday/... 
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg, 
kmiv, kacy and surrounding areas. 

Through 12z...IFR St/fog now mostly kttn north and receding northward. 
Elsewhere MVFR fog or VFR ceilings at or above 4000 feet. Light wind. 

After 12z today...any remaining MVFR/IFR cigs, primarily NE PA 
and northwest New Jersey will lift by 16z while elsewhere widespread ceilings at or above 
4000 feet. Gusty SW wind to 25 knots in the afternoon prior to the cold front passage. 
A 1 hour band of brief IFR showers and scattered thunderstorms will be 
developing eastward this afternoon with potential for westerly gusts to 
40 knots near any thunderstorms. Please see tafs for details. Confidence: above 

Tonight...any lingering showers should quickly exit offshore between 
00z-02z/10 with VFR ceilings clearing to reveal only cirrus after 06z/10. 
Winds becoming predominantly northwest with gusts around 20 kt, then turning 
northerly toward 10z Saturday. Confidence: above average. 

Saturday...VFR. North-northeast winds mainly 10-15 knots, then 
diminishing in the late morning and afternoon /becoming mostly light 
and variable at night/. 

Sunday and Monday...mainly VFR. 

Tuesday...mainly VFR, however a cold front moving through may 
produce some showers. 


Small Craft Advisory headlines. Small Craft Advisory SW wind begins around midday nearshore ports 
where navigation may be hindered. Further out over the water, the 
southwest wind may be a little less due to less Transfer. Easterly 
swell this morning will be overrun by a developing southerly short 
period chop this afternoon, 

Today...winds are expected to increase to 25 knots, and and seas 
on the ocean are expected to increase to 5 feet during the day 
ahead of the frontal boundary. 

Tonight...wind shift to northwest with gusts 25 kt, especially New Jersey waters 
after midnight. Atlantic seas 4-5 feet. 

Saturday...high pressure building in from the west and weak low 
pressure to our south will result in a northerly wind. The presence 
of cold air advection initially and a tightened pressure gradient will result in 
gusty winds, however as the high builds closer the winds are 
expected to decrease from north to south in the afternoon. As a 
result, we will extend the Small Craft Advisory through midday for 
the Atlantic coastal waters and lower Delaware Bay. The winds and 
seas are expected to lower at night. 

Sunday through Tuesday...the winds and seas are anticipated to be 
below Small Craft Advisory criteria at this time. A cold front 
however arrives during Tuesday. 


Phi watches/warnings/advisories... 
New Jersey...none. 
Marine...Small Craft Advisory from 11 am this morning to noon EDT 
Saturday for anz431-450>455. 
Small Craft Advisory from 11 am this morning to 6 PM EDT this 
evening for anz430. 


near term...drag 554a 
short term...drag 554a 
long term...gorse 
aviation...drag/gorse 554a 
marine...drag/gorse 554a 

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