Weather

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Area forecast discussion 
National Weather Service Gray ME 
253 am EDT Friday Aug 29 2008 


Synopsis... 
high pressure riding south from the Maritimes will move slowly 
east today and tonight. Meanwhile...low pressure south of Nova 
Scotia will move slowly northeast. A cold front will cross the 
region on Saturday. Then high pressure will ridge in from the 
Great Lakes Sunday through Wednesday...bringing fair weather and 
above normal temperatures. 


&& 


Near term /through today/... 
the forecast problem for today is clouds. 


Currently...the forecast area remains under the influence of 
surface high pressure and a closed middle level system. The closed 
middle level system (with a respectable surface low) is pushing clouds 
and showers across Nova Scotia and easternmost Maine. Meanwhile... 
middle and high level clouds associated with the middle level system 
that used to be Fay are trying to impinge upon the middle level ridge in 
place. 


Both of these system will try to throw clouds back across the 
forecast area today. While the clouds to the west should remain 
there for the most part...the clouds from the east will be the 
forecast problem. Should see less of an influence this afternoon 
from the eastern system...so will try to Divide the day with less 
clouds in the afternoon. 


The Canadian radar mosaic shows rain showers moving steadily west 
across Nova Scotia...and there have been some rain showers reported 
in central Nova Scotia and New Brunswick. For this reason...will 
carry a mention of showers for the eastern zones this morning. 


There could be a few light rain showers across the mountains this 
afternoon as well...as warm air advection focusing on a weak warm 
front. Elsewhere...expecting dry conditions. With the clouds this 
morning and the onshore flow...used a blend of MOS numbers for 
highs. 


&& 


Short term /tonight/... 
the influence of the eastern system should be less tonight...and 
all areas may see partly cloudy skies early. However...warm air 
advection ahead of the next short wave in the northern stream 
should get into the area late this evening and tonight. In 
addition...as the surface flow turns to the south and southwest... 
it may pick up developing stratus in the Gulf of Maine and bring 
it into the middle coast and central Maine. 


The warm air advection is broader with the set of model runs for 
tonight. This should result in rain showers being relegated to the 
mountains...where the orographic lift may help focus the warm air 
advection. The GFS MOS numbers look too cool for tonight in the 
warm air advection...and a blend of MOS numbers were used for 
lows. 


&& 


Long term /Saturday through Thursday/... 
a cold front will cross the region Saturday...but outside of this 
feature...expect a prolonged dry period. Saturdays cold front is 
associated with a strong 500 mb trough...which eventually closes off 
as it moves to our northeast. Front is much better defined 
aloft...with little temperature contrast between the warm and cold 
side. Both NAM/GFS bring the front through Saturday...however with 
limited moisture prefer to keep probability of precipitation in the chance range...highest 
in the mountains. Marginal thin convective available potential energy suggest scattered 
thunderstorms are likely...with severe weather threat minimal unless 
model dew point forecasts are too dry. NAM/GFS MOS blend works OK 
for highs. 


Largely expect showers to be done by Saturday night...though 
respect the MOS enough linger probability of precipitation east Saturday evening...this 
mainly right at the 00z cut-off. Have fairly high confidence that 
by midnight we/ll be on our way to clearing. 


On Sunday...a very favorable pattern for nice weather sets 
up...with a ridge to our west and a cutoff to our east at 500 mb. 
Thus have a high confidence in dry and fair weather for an 
extended period...lasting well into next week. Given GFS/European 
agreement on this persistent pattern...feel comfortable hedging 
drier and warmer than climatology weighted MOS. 


&& 


Aviation /07z Friday through Tuesday/... 
in the near term...the stratus moving west from the ocean storm 
has to this point remained above 3000 feet. However...ceilings 
between 2000 and 300 feet were reported over Nova Scotia...and 
this is about the height from the 0000 UTC cyqi soundings. This 
could lead to MVFR ceilings this morning for kaug and kpwm. 


Kleb is showing signs of going to LIFR...and this is expected 
through 1300 UTC. After this...would expect VFR conditions just 
about everywhere today. As the flow becomes south and southwest 
tonight...MVFR/IFR conditions are possible after 0500 UTC Saturday 
at kpwm and kaug. Elsewhere...mainly VFR conditions are expected 
overnight into early Saturday morning. 


Looking ahead...scattered thunderstorms Saturday afternoon. Expect 
predominantly VFR conditions Sunday through Tuesday as a strong 
ridge builds in. 


&& 


Marine... 
in the near term...winds are near 15 knots on the ocean 
waters...being on the western fringe of the gradient of the 
offshore low. As the surface low slowly move away today...the 
gradient will relax. In fact...winds should come around to sea 
breeze directions late this afternoon as high pressure again 
becomes the dominant feature over the waters. 


For the short term...as the surface highs moves east...and the 
gradient starts to tighten in advance of the cold front...the 
southwest flow will increase over the waters tonight. The depth 
of the mixed layer over the waters (based on model soundings) 
does not appear deep enough to allow gusts to exceed 20 knots. 
Through the short term...winds and seas are expected to remain 
below small craft limits. 


For Saturday...expect winds to pick up ahead of the front...with 
gusts pushing Small Craft Advisory levels as afternoon sea-breeze enhances a SW 
flow. Went a tad above MOS for this reason. Otherwise...front 
sweeps through Saturday night...with a decent but sub Small Craft Advisory northwest flow 
for Sunday. Winds gradually lax as high pressure builds from the 
west through Tuesday. 


&& 


Gyx watches/warnings/advisories... 
ME...none. 
New Hampshire...none. 
Marine...none. 


&& 


$$ 


Synopsis...apffel 
long term...apffel 
marine...apffel