995 
fxus61 kphi 220000 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
800 PM EDT sun Mar 21 2010 


Synopsis... 
high pressure responsible for our fine weather this weekend will 
move slowly off to the east tonight. A low pressure system will 
approach from the southwest overnight and Monday and bring a return 
of rain before passing off the middle Atlantic coast Tuesday. More high 
pressure will build into our region from the west for the middle and 
latter parts of the coming week. Another cold front will move in to 
start the upcoming weekend. 


&& 


Near term /until 6 am Monday morning/... 
at 00z cirrus was increasing around the area and seemed thickest 
south...especially southeast. The high clouds will thicken and 
lower to middle level cloudiness...and then low clouds...ahead of an 
approaching storm system as the overnight progresses. Some light 
rain may move into the area late tonight, well ahead of the main 
rain expected Monday. However, any rain overnight will be light. 
With clouds expected tonight, along with a light southerly flow, 
temperatures should not fall rapidly and be generally in the 
upper 40s to lower 50s. 


&& 


Short term /6 am Monday morning through Wednesday/... 
an area of low pressure will be lifting toward the area Monday and 
bring a frontal boundary through the area Monday night into 
Tuesday. Rain will overspread the area late in the day Monday and 
continue into Monday night. Rainfall amounts are expected to range 
from 0.50 inches to 1.00 inches in the southern half of the cwa, 
to 1.00 to 1.50 inches in the northern half of the County Warning Area. There 
could be some locally heavier amounts, especially if any 
convection does occur. There is not a tremendous amount of 
instability, nevertheless, the Storm Prediction Center does have our area outlined in 
general thunderstorms. One thing of note is the GFS was 
significantly lower than the rest of the model consensus in 
regards to the quantitative precipitation forecast. The European model (ecmwf)/NAM/Gem/sref were all closer and 
about 0.50 to 1.00 inches greater than the GFS, therefore we went 
with a blend of the consensus. The heaviest rain is expected to 
occur late Monday afternoon into Monday evening. With flooding 
still occurring from the previous rain and rivers still running 
high in northern New Jersey, we have decided to issue a Flood 
Watch for our 6 northern New Jersey counties. Please refer to the 
latest Flood Watch for more information. 


Rain is expected to begin to taper off Monday night and into Tuesday 
morning. However, there could still be some showers on Tuesday 
before the upper level low moves out of the area. Any rain on 
Tuesday is not expected to be heavy. Temperatures Tuesday will 
likely get into the upper 50s to around 60 behind the departing low 
pressure system. As we go into Tuesday night and Wednesday, winds 
could get quite breezy as the low pressure moves to our northeast 
and really begins to tighten up. Winds on Tuesday night/Wednesday 
could gust up to 3o to 35 miles per hour at times. Other than the wind, 
Wednesday will likely be a pretty nice day with temperatures 
generally in the upper 50s to lower 60s. 


&& 


Long term /Wednesday night through Sunday/... 
pleasant weather will be across our part of the country during the 
beginning of the extended period. High pressure will be ridging 
eastward from a center over the Ohio Valley Wednesday night and Thursday. 
Temperatures on Thursday will be cooler than than on Wednesday with 
readings mostly in the middle to upper 50s...but these temperatures are 
still a little above normal for late March. 


A sharpening 500 mb trough across central Canada during the middle of 
next week will cause low pressure to move across eastern Canada 
Thu-Fri. An attached cold front will cross the northeast and middle 
Atlantic region late Thursday night and Friday morning. A chance for showers 
was retained in the forecast for this feature. A small area of -SW was 
confined to the highest elevations of the southern Poconos and Sussex city 
New Jersey with marginally cold temperatures late Thursday night. 


A high pressure system from Canada will build over the region next 
weekend and dry weather is expected. The temperatures will dip a 
little below normal with highs in the 50 to 55 degree range and lows 
in the 30s most areas. 


&& 


Aviation /00z Monday through Friday/... 
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg, 
kmiv, kacy and surrounding areas. 


The latest tafs continue the trend from the previous ones showing 
that weather conditions will go down tonight as low pressure over 
the Tennessee Valley approaches our region. As low level moisture 
increases, ceilings will gradually lower. By daybreak with light rain or 
drizzle moving in, ceilings should be down to MVFR/IFR. The rain will 
become more widespread and heavier during the day. This will keep 
conditions quite low, generally in the IFR range, although could 
vary from LIFR to MVFR at times with the rain intensity. Could also 
be some embedded thunderstorms in the afternoon and evening hours, 
mainly in our southern sections. Winds should be relatively light 
with this system, since the storm center is forecast to move almost 
directly over US. 


Outlook... 
conditions will remain low through Monday night but should begin 
to improve Tuesday as slightly drier air moves in and the 
precipitation becomes showery. As the low pulls off to the northeast 
Tuesday night and Wednesday, northwest winds will become quite blustery. 
High pressure will bring fair weather and good flying conditions 
Wednesday through Thursday. 


&& 


Marine... 
relatively tranquil conditions continue today as high pressure 
moves off to the east. Low pressure over the Tennessee Valley will 
move across our area late Monday into Tuesday and then head off to 
the northeast later Tuesday into Wednesday. This system will provide 
our waters with another round of rain with the possibility of 
a few embedded thunderstorms. With the low approaching and the 
pressure gradient tightening, winds and waves will be increasing 
from south to north. The onset of the Small Craft Advisory will be 
pushed back to noon Monday on Delaware Bay and on our southern ocean 
waters. The advisory will be raised on our northern ocean waters at 
7 PM Monday. Advisories for all waters will continue until 8 PM 
Tuesday. They will likely need to be extended at least through 
Tuesday night and possibly well into Wednesday as northwest winds increase 
as the low pulls off to the northeast. Winds and seas will diminish 
later Wednesday through Thursday as high pressure moves back in. 


&& 


Hydrology... 
model quantitative precipitation forecast apparently dropped on the overnight shift for this 
upcoming rain event later Monday through Tuesday...but has increased 
on the 12z NAM and the latest European model (ecmwf). The heaviest rain appears to 
occur Monday night into early Tuesday...as low pressure over the 
lower Mississippi and Tennessee valleys this evening will move 
northeastward tonight and Monday and pass over our area Tuesday. 


Rain is forecast to be heavy at times later Monday afternoon and 
Monday night...and taper off during Tuesday as low pressure passes 
through the region. General rain amounts are forecast to be in the 
range of one to one and a half inches...with local amounts possibly 
around two inches. Since streams and rivers are elevated...and 
surface and especially subsurface moisture is high...additional 
small stream and even river flooding could occur Monday night and 
Tuesday. Where flooding was recent or even ongoing on the Passaic 
and Raritan rivers...renewed flooding may be experienced into the 
middle of this coming week...but that will depend on exactly how 
much rain falls. 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...Flood Watch from Monday afternoon through Tuesday afternoon 
for njz001-007>010-012. 
Delaware...none. 
Maryland...none. 
Marine...Small Craft Advisory from noon Monday to 8 PM EDT Tuesday for 
anz430-431-452>455. 
Small Craft Advisory from 7 PM Monday to 8 PM EDT Tuesday for 
anz450-451. 


&& 


$$ 


Synopsis... / Miller / Robertson 
near term...Robertson / 
short term...Robertson / 
long term...O'Hara 
aviation...rpw / O'Hara 
marine...rpw 
hydrology.../ 

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