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Area forecast discussion 
National Weather Service Gray ME 
233 PM EDT sun Sep 7 2008 


Synopsis...the remnants of Hanna will continue to head into the 
Maritimes tonight. An upper level disturbance will cross the 
mountains overnight...and another upper level disturbance will 
cross the region Monday. A strong cold front will cross the 
region late Tuesday...bringing showers and thunderstorms to the 
region. High pressure will build in from the west behind the 
front...cresting across the region Thursday. 


&& 


Near term /through tonight/... 
after the not so subtle conditions brought on by the remnants of 
Hanna...weak features may more a more nebulous forecast tonight. 


The moisture trapped under the inversion in the low level cold air 
advection has been slow to leave across the mountains and central 
zones. This should occur as the inversion weakens...and model 
soundings indicate this will occur prior to 0000 UTC Monday just 
about everywhere. The gradient eases enough to allow winds to drop 
off quickly after sunset (at the latest). 


Have been watching the weak short wave and associated surface 
trough across eastern Ontario and western New York state this 
afternoon. Overall...the convective potential with these feature 
has been waning...but the wind shift line remains well defined (on 
satellite and the radar composite). Would expect this feature to 
weak slowly as it moves east as its middle level support weakens and 
shears to the northeast. 


The clouds from this system should remain more or less intact and 
impact northern zones tonight. Also included a slight chance of 
showers for the mountains if the activity on radar now happens to 
survive this far east. Elsewhere...expect dry conditions with 
partly cloudy skies north (except for the mountains) and mainly 
clear further south. 


The clouds could affect the amount of patchy fog that develop 
tonight across northern zones. Elsewhere...with abundant low level 
moisture and slackening winds...will include patchy fog in most 
locations. A blend of MOS numbers should be OK for lows...except 
in the mountains...where lows were several degrees warmer than the 
blend...with clouds in place and more arriving. 


&& 


Short term /Monday/... 
the first short waves moving through Quebec early...but there is 
another on its heels. The next short wave was over Minnesota early 
this afternoon. There were light rain showers with this feature in 
the upper Midwest this afternoon...and would expect this to move 
across the mountains in the afternoon. With dry sub cloud conditions 
over the mountains Monday with some mixing...not sure how much 
will reach the ground. Will include a slight chance of showers for 
the mountains with the showers as it weakens in the flow as it 
moves east. 


Elsewhere...partly to mostly sunny skies should cover. The 
gradient closer to the coast may relax enough for a sea breeze to 
develop. Highs were based mainly on a MOS blend. 


&& 


Long term /Monday night through Sunday/... 
with the exception of the NAM...GFS/Gem/UKMET/European are in good 
agreement with the strong cold front...bringing it across Tuesday 
afternoon. The NAM develops the low aloft much stronger...slowing 
its progression...however feel this solution is an outlier and 
stick closer to the GFS for this time period. With a late 
afternoon frontal passage...there is a severe weather threat for 
the region...slightly higher in southern sections where moist air 
is more likely to work in. Wind fields aloft are very strong...around 
50 kts at 850 mb ahead of the front. Instability appears to be the 
limiting factor. Weaker storms would not be able to transport 
these winds to the surface...however stronger cells could evolve 
into lines or line segments...which would produce damaging winds. 
For now will mention in severe weather potential statement...noting we are in a slight risk in 
Storm Prediction Center/S graphic. Carry likely probability of precipitation Tuesday in most areas...then 
taper to chance Tuesday evening. Also...noted GFS hinting at our 
first upslope event of the season...with clouds...and perhaps rain 
showers in the mountains late Tuesday night. 


Beyond this...models in excellent agreement...with strong high 
pressure building in from the west Wednesday...then cresting 
across the region Thursday. Given the cold air behind the 
front...and the high settling in...see the potential for the first 
frost of the season...mainly in the mountain valleys. 
Otherwise...expect fair weather...as we get a preview of fall 
through the end of the week. 


Beyond...European is faster with the next shortwave by about 12 
hours compared to the GFS. Prefer a blend...with chance probability of precipitation at 
the consensus...then high pressure builds behind the 
shortwave...perhaps bringing fair weather for next weekend. 


&& 


Aviation /18z Sunday through Friday/... 
in the near term...all terminals have improved to VFR as the 
moisture trapped under the inversion in low level cold air 
advection has been slow to mix out. Winds will cease gusting 
before 2200 UTC as low level cold air advection ends and the 
gradient eases. Would expect VFR conditions to continue through 
at least 0600 UTC Monday. 


After this...it is not clear just how widespread the patchy fog 
will be tonight. Clouds with the short Ave and cold front over 
western New York state and eastern Ontario should remain mostly to 
the north of the terminal sites...and LIFR conditions are expected 
at kleb between 0800 UTC and 1300 UTC Monday. VFR conditions are 
expected Monday. 


Thunderstorms will likely impact aviation Tuesday afternoon into 
evening...with predominantly VFR conditions behind the front for 
Wednesday and Thursday. 


&& 


Marine... 
in the short term...winds are still marginal for small craft in 
the wake of the remnants of Hanna...but seas remain up. It will 
take most of the night for the seas to drop back below 5 feet over 
the ocean... but could do this a bit sooner over the bays. 


The westerly gradient Monday may ease enough for sea breezes to 
form in the afternoon...but winds and seas should remain below 
small craft levels. 


In the long term...a Small Craft Advisory will likely be needed 
Tuesday...ahead of the cold front. Expect marginal but below Small Craft Advisory 
conditions behind the front...with winds/seas dropping through 
Thursday as high pressure builds towards the waters. 


&& 


Hydrology... 
river levels continue to fall this afternoon as the runoff process 
seems to have peaked. The Presumpscot River at Westbrook has crested 
and is falling the river should drop below flood stage this evening. 


&& 


Gyx watches/warnings/advisories... 
ME...none. 
New Hampshire...none. 
Marine...Small Craft Advisory until midnight EDT tonight for anz150>154. 


&& 


$$ 


Long term...apffel 

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