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fxus61 kgyx 041712 
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Area forecast discussion 
National Weather Service Gray ME 
1212 PM EST Thursday Dec 4 2008 


Synopsis... 
a cold front will move across the region late today...setting off 
some scattered rain or snow showers. A ridge of high pressure will 
build over New England Friday and Saturday...providing generally 
fair...but cold...conditions. Weak low pressure will approach 
from the Midwest Saturday night and Sunday while developing low 
pressure passes offshore. The interaction between these two 
systems may produce a period of accumulating snow across the 
region on Sunday. High pressure returns on Monday...with another 
storm system possible late Tuesday or Wednesday. 


&& 


Near term /until 6 PM this evening/... 
update to input latest observed data and extrapolate to the forecast 
through this afternoon. Slight adjustment to maximum and hourly temperatures based 
on latest observed readings. Otherwise no significant changes at this 
time. 


Cold fnt moves through late in the day with isolated to scattered -shra ahead of 
it over southern areas...with more organized -shra with higher pop over 
more northern zones. Colder air follows the fnt so -shra may mix with 
or change to -shsn over the Montana zones later this afternoon. 


&& 


Short term /6 PM this evening through 6 am Friday/... 
front should be just offshore by 00z. Expect a brief period of 
upslope snow showers...due to a 25 knots 925 mb wind. 
However...downward motion should dry things out quickly after 
midnight...cutting off the upsloping. Accumulations of an inch or 
two is all that is expected in favorable upslope locations. 


Foothills south...skies should clear out quickly behind the front. 
Use NAM/GFS MOS blend for lows...tweaking up a bit in the 
mountains where clouds should limit radiational cooling. 


&& 


Long term /Friday through Wednesday/... 
generally favoring the 00z NAM through Sat...then the GFS 
ensemble...which is similar to the 12z Euro...through the rest of 
the period. Large scale 500mb trough to continue to spread across 
the eastern 2/3 of noam through the middle of next week...with larger 
waves allowing fluctuations of the large scale trough axis...and 
also producing weather changes across the County Warning Area. 


Cold surface high builds over the middle-Atlantic on Friday with ridging 
extending north into New England...which will allow for a cold...but 
fair day...which will continue into Sat. Will have to watch a weak 
wave moving through Friday night...which could set off a few 
shsn...mainly in the mts...where it could help enhance upslope. 
Sat will likely remain dry...but will start to see hi clouds moving 
in advance of next system...which could produce some accumulating 
snow...as large scale 500 mb trough lifts NE across the Great 
Lakes...and surface low develops beneath a more potent 500mb wave 
offshore...with a little light snow a good bet beneath middle-level 
deformation between these systems. This system moves out Sun 
night...with high pressure building for Monday. 


Models differ more significantly late in the period with 00z op 
GFS being an outlier with its idea of very strong closed low 
tracking to the west of County Warning Area...and pulling polar vortex equatorward 
into southern Quebec. Prefer the less amplified solutions of the 
gefs/Euro....which would still bring some precipitation during the middle- 
week...mainly rain...as we/ll remain on warm side of the system. 
Have kept temperatures closer to climatology during the end of the period given 
the uncertainty. 


&& 


Aviation /17z Thursday through Monday/... 
short term /today through tonight/...don't expect much impact from 
showers associated with a frontal passage this afternoon...though 
leb will see MVFR ceiling and possible MVFR visibility with -shra while a brief 
period of MVFR visibility or ceilings is possible at all other taf sites. 
Some higher gusts from SW winds through most of the afternoon then 
winds will ease up later today as the surface pressure gradient relaxes 
ahead of the fnt. 


Long term...could see an extended period of flight restrictions 
Sat night into sun during a period of light snow. 


&& 


Marine... 
short term /today through tonight/...will continue a glw until 3 PM 
today for our two eastern outer coastal waters zones based on latest 
buoy reports. Otherwise Small Craft Advisory up for waters through this evening. Have 
bumped up seas forecast a little more for the rest of today into tonight 
based on latest buoy reports showing seas as high as 10 feet over 
the outer waters. Strong SW flow ahead of approaching cold fnt 
mixing low level winds down to surface with gusts over 40 knots at mism1. 
Winds will let up late this afternoon as the pressure gradient 
relaxes...but Small Craft Advisory conditions will still persist. Finally fnt 
moves through this evening with wind shift and eventually winds and 
seas subside. 


Long term...will see a relatively quiet period on the waters Friday 
through Sunday...as winds seas likely to remain below Small Craft Advisory levels. Might 
need Small Craft Advisory come Sun night or Monday as winds increase behind off shore 
low pressure. 


&& 


Gyx watches/warnings/advisories... 
ME...none. 
New Hampshire...none. 
Marine...Small Craft Advisory until midnight EST tonight for anz151-153- 
154. 
Small Craft Advisory until midnight EST tonight for anz150-152. 
Gale Warning until 3 PM EST this afternoon for anz150-152. 


&& 


$$