658 
fxus61 kcar 041705 
afdcar 


Area forecast discussion 
National Weather Service Caribou ME 
1205 PM EST Thursday Dec 4 2008 


Synopsis... 
a strong cold front will approach from the west today and then 
move across the region late this afternoon into this evening. 
Much colder air will pour into the area tonight behind the cold 
front. An upper level disturbance is expected to cross the region 
Friday reinforcing the cold air across the area. High pressure 
will then remain across the region through Saturday. Low pressure 
may bring some snow to the area later Sunday and Sunday night. 
&& 


Near term /through tonight/... 
have adjusted probability of precipitation across the north and went with mainly snow 
for precipitation type across the northern zones this afternoon based 
on several ground truth reports. 


Also..issued a Wind Advisory until 21z for zones 29/30 since 
rainwise observation are showing US getting close to criteria at this time. 


The front is expected to be at the coast by the evening. Much 
colder air seeping in as 850mb front moves across the region. Kept 
chance probability of precipitation in across the north and west this evening to account for 
this feature. Clouds will begin to break up by daybreak Friday as 
drier air works in. Gmos temperatures for tonight looked decent and were 
accepted. Some adjustments were made downward for the low lying 
areas. 
&& 


Short term /Friday through Friday night/... 
Friday and Sat appear to be msly dry and seasonably cold with typical 
SC cloud cover and flurries msly for northern/western portions of the forecast area. 
&& 


Long term /Saturday through Wednesday/... 
aftwrds...models continue to indicate a strong digging shortwave complex 
advancing southeast from central can into the lower Great Lakes and Ohio Valley. 
The 00z European model (ecmwf) continues to be the most agressive with this 
system...forming a secondary surface low somewhere off the middle Atlantic 
coast Sat night and tracking it NE toward western Nova Scotia on sun and 
into the Gulf of Saint Lawrence Sun night. This scenario would result 
clouds to increase over the forecast area Sat night and allow this system to form 
an organize precipitation shield to result in potentially significant 
amounts of snfl due to Atlantic moisture inflow...especially inland 
from the immediate coast over eastern portions of the forecast area. Coastal areas 
may experience enough low level warming from the Atlantic for snow to mix or 
even change over to rn sun after/Erly evening. In any event...the trend 
advertised by the ecmw is backed up enough by the 00z GFS and GFS 
ens members to increase probability of precipitation to the likely category sun into sun 
evening for the forecast area. 


Snow should taper to snow showers across the forecast area by Monday morning...continuing through 
the after before ending Monday night as a narrow ridge of hi pressure approaches 
and crosses the forecast area. 


Both the GFS and European model (ecmwf) increase clouds quickly over the forecast area on Tuesday as 
middle/upper warm advcn begins in earnest. Snfl should again 
overspread the af by Tuesday after and continue Tuesday night. The 00z GFS opnl 
model run indicates that enough middle/low level warm air should arrive to 
transition snfl to rn or mixed rn/snow over especially eastern portions of the forecast area 
late Tuesday night into Wednesday before colder air moves back into the forecast area 
behind a first WV of low pressure prognosticated to depart the forecast area by Wednesday night. 
There the models diverge...with opnl runs and some of the GFS ens 
members indicating a potentially stronger secondary to impact the 
forecast area on Thursday. For now gvn model low pressure temporal/spatial uncertainties 
with this system...we have opted to keep probability of precipitation in the chance category 
for now with this event. 
&& 


Aviation /18z Thursday through Tuesday/... 
near term: VFR this morning dropping back to MVFR this afternoon 
into the evening for the northern taf sites. Kbgr and kbhb should 
see VFR through tonight. 


Short term: hi MVFR clgs to VFR conditions will prevail across the 
forecast area Friday into Sat night...with the best chance of MVFR clgs across northern taf 
sites. All sites will lower to MVFR/IFR in clgs and snfl sun into 
Sun night. Downeast sites should recover to VFR on Monday while northern taf 
sites remain MVFR in occasional snow showers. 
&& 


Marine... 
near term: have issued a glw until 21z for the outer waters as 
winds ahve increased in the SW flow ahead of the cold front. 
Small Craft Advisory remains in effect for intracoastal waters. 


Short term: strong Small Craft Advisory to possibly gales can be expeceted on the back 
side of the departing late weekend low into Monday across our waters. 
We used the wna ww3 data fo WV heights and a blend of GFS...NAM and 
GFS MOS for winds. 
&& 


Car watches/warnings/advisories... 
ME...Wind Advisory until 4 PM EST this afternoon for mez029-030. 
Marine...Small Craft Advisory until 4 PM EST this afternoon for anz052. 
Gale Warning until 4 PM EST this afternoon for anz050-051. 


&& 


$$ 


Near term...duda