Weather

226 
fxus61 kphi 110812 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
412 am EDT Sat Oct 11 2008 


Synopsis... 
high pressure will dominate the weather through Tuesday. A weak 
backdoor cold front will cross the region Monday. A cold front 
will cross the region late Wednesday into Thursday. Another cold 
front may impact the region late in the week. 


&& 


Near term /through tonight/... 
areas of patchy fog have developed at some of our observing sites 
this morning but should dissipate as the sun begins to rise. The 
fog layer is pretty shallow in most areas and should not amount to 
much. Areas closer to the shore, where the sea breeze moved 
through yesterday, have had a bit more fog this morning. 


High pressure will continue to dominate our weather. The 
persistent low pressure system off the the south of the region has 
brought some cirrus across the southern areas overnight. The skies 
should begin to clear out as we approach day break with clear to 
mostly clear skies throughout the forecast area. 


Temperatures will once again reach into the 70s across the region 
with a north to northeast wind prevailing throughout the day. 
Overall, a beautiful day is on tap for the weekend! 


&& 


Short term /Sunday through Monday/... 
high pressure at the surface will remain over our region while the 
ridge aloft continues to build. 850mb temperatures for this period are up 
around +15c which should translate into warming temperatures for Sunday and 
Monday for our area. We have kept the highs below 80 for both 
Sunday and Monday but as the airmass modifies it may get pretty 
close to 80, especially on Monday, in some areas. 


Sunday night will cool back down as we once again have clear skies 
and relatively calm winds overnight. Some fog may form again but 
may be restricted to areas near rivers and valleys. 


&& 


Long term /Monday night through Friday/... 
high pressure starts to shift off to our south Monday as a weak 
backdoor front pushes down from the north. The models have backed 
off on this feature over the past several runs as ridging aloft 
looks to be quite strong. It looks like the backdoor front will 
bring about a shift in the winds with little else amounting from it. 


A cold front will approach the region Tuesday ushering in clouds 
across the region. If the backdoor front remains a factor then we 
could see some showers along it as it pushes back north as a warm 
front. For now we keep the forecast dry through Tuesday. The cold 
front will cross the County Warning Area late Wednesday into Thursday, bringing 
showers across the area. The 00z GFS has slowed the frontal 
passage down and seems to be in line with the 00z European model (ecmwf) solution. 
With confidence starting to build in this period we have decided 
to follow the 00z GFS and integrate it into the current forecast. 
The latest model runs also show that the front will be on the dry 
side. 


High pressure is expected to build in from the west Thursday and 
hang around through Friday. Another low pressure system may impact 
the region as we head into the weeks end. 


The Wednesday through Saturday time frame in the extended has 
considerable uncertainty tacked along with it. Because of timing 
issues amongst the different models, we have decided to go with 
chance probability of precipitation for the later part of the period. 


For temperatures, with the MOS guidance flip flopping from run to 
run we did not want to lean to heavily on one particular run. 
Therefore, we went with a blend of the new 00z MOS guidance and 
continuity. This way we ensure that some new data is reflected in 
the forecast without any major changes having been made. 


&& 


Aviation /08z Saturday through Wednesday/... 
high pressure will continue to build into the area today and be the 
main weather feature for the next several days. A persistent 
upper-level system however near the southeastern United States 
continues to toss some cirrus our way. This is being pulled 
northward by a segment of a 250 mb jet. This feature is forecast to 
gradually slide eastward today. The air mass is rather dry, however 
dew points have made a significant recovery from yesterday afternoon 
and this is leading to saturation right near the ground /more of a 
rather shallow fog layer in spots/. This may result in some IFR fog 
at kmiv and even IFR/LIFR fog at kacy at times early this morning. 
It is unclear if river fog is able to form and impact krdg, 
therefore it has not been included but will monitor. Elsewhere, fog 
is not anticipated. The surface winds today will be rather light to 
start, however with high pressure to our northwest, we will have a 
northeasterly wind increase after sunrise as vertical mixing 
develops and deepens. The winds are not that strong for a distance 
above the surface, therefore we are not expecting winds to exceed 
10 knots. Given the prevailing rather light northeast flow today, 
there should be a sea breeze influence at kacy and kmiv this 
afternoon allowing winds to shift to the east and southeast for a 
time before going light and variable. We also may see a Bay/river 
influence settle into kilg and kphl respectfully this afternoon. 


Any wind will quickly diminish early this evening with the loss of 
daytime heating with perhaps a touch of cirrus tonight. 


Outlook... 
high pressure overall is forecast to remain the dominate feature 
into Tuesday. However, a backdoor front is forecast to move across 
our area on Monday. This front looks rather weak with a wind shift. 
One possible fly in the ointment is with a possible moistening 
low-level airmass with an onshore flow Monday night and Tuesday. This 
could introduce some low clouds, however this scenario is rather 
uncertain at this time. Patchy fog could be possible during some 
early mornings. A potentially bit more active front then approaches 
on Wednesday but may not move through until Wednesday night into 
Thursday. 




&& 


Marine... 
high pressure will continue to build into the area today and be the 
dominate feature into early next week. The position of this high 
will produce a northeasterly flow today through Sunday. A weak front 
will then settle across the area from the north and northeast later 
Monday. This front looks rather weak with mainly just a wind shift 
expected as it moves through. The pressure gradient does not look to 
be that strong and the onshore flow behind the backdoor front also 
does not look that strong. Forecast soundings only indicate about 15 
knots reaching the surface during this time frame. 


The next cold front looks to arrive sometime Wednesday into 
Thursday. There are differences in the timing with this front with 
some model guidance being much slower than others. For now, we will 
bring the front into the waters Wednesday night. The flow will 
increase some from the south and southwest ahead of this front. All 
indications are that winds and seas will remain below Small Craft 
Advisory criteria through the forecast period. 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...none. 
Delaware...none. 
Maryland...none. 
Marine...none. 


&& 


$$ 
Synopsis...meola 
near term...meola 
short term...meola 
long term...meola 
aviation...gorse 
marine...gorse 

National Weather Service Glossary of Abbreviations

Non-Expanded Version (with abbreviations)