082 
fxus61 kcar 200940 
afdcar 


Area forecast discussion 
National Weather Service Caribou ME 
440 am EST Thursday Nov 20 2008 


Synopsis... 
low pressure over the Maritimes will continue to move northward 
today and tonight. Mostly cloudy conditions can be expected in the 
north today. In southern areas skies will become cloudy later 
today and continue into Friday. Low pressure intensifying in the 
Maritimes on Saturday combined with upper level low pressure from 
Ontario province will bring snow showers to the region by Saturday 
afternoon...continuing into Saturday evening before tapering to 
flurries by Sunday morning. After fair and colder conditions 
Sunday afetrnoon and Sunday night...clouds will increase Monday 
ahead of a potentially significant storm system on Tuesday. 


&& 


Near term /through tonight/... 
intense low pressure over the Maritimes will continue to move to 
the north today and tonight. A weak upper level trough will persist 
over the northern portion of the state today then weaken tonight. 
Radar indicates some weak banding extending from New Brunswick 
into the northeastern portion of the forecast area. Have increased 
probability of precipitation slightly in this vicinity for early portion of the forecast 
this morning. For probability of precipitation will use a blend of the NAM...GFS and sref. 
Will used NAM/GFS blend for sky. Expect mostly cloudy skies north 
today. In southern areas should start with sun then increasing 
clouds later in morning into the afternoon. For wind...temperature 
and dew point have used gmos. 
&& 


Short term /Friday through Sunday night/... 
a break between systems will end by Sat as a shortwave complex digs east-southeast 
into central new eng. This feature will help intensify an ocean 
storm well east of Cape Cod as it moves north-northeast toward the can martimes. 
Although we not be directly influenced by this storm...there is 
potential for a weak deformation zone to set up over central and northern 
portions of the forecast area Sat after into Sat evening as an upper low closes off 
across southern portions of the forecast area. This would enhance snow showers over this 
portion of the forecast area...quite possibly resulting in at least 1 to 2 inch 
snow accumulations. There could even be more snfl if deeper Atlantic 
moisture gets advected into an extended trowl zone...but its still 
a little early to tell this with confidence at this time. Most snow showers 
will taper to flurries across the forecast area late Sat night with partial 
clearing expeceted especially over downeast and central areas on sun. 


What brief window of mclr skies will likely occur Sun night across 
the region as a weak surface ridge crosses the region. Sun and Sun night 
may be the coldest periods across the region. 
&& 


Long term /Monday through Wednesday/... 
GFS ens indicate hi uncertainty with S/waves interacting with the 
long wave pattern over the NE Pacific just west of British Columbia can and with the 
mean upper ridge over the north central Atlantic. This has resulted in a 
large spread of possible outcomes with the potential signfcnt 
storm system to impact our forecast area by midweek. For now...the preferred 
solution is the GFS ens mean which does not dig the upper trough as 
far S and west as the 00z European model (ecmwf) at this time. This would favor a primary surface 
low filling from eastern ont prov can Monday/Monday night with a secondary low 
reforming near the ME coast on Tuesday...with the secondary low then 
slowly tracking NE across southeast ME to just east of the ME/New Brunswick border Tuesday 
night and Wednesday morning. This track would result in snow or snow mixed with 
rain Monday night chgng to all rn as far north as perhaps east Central Aroostook 
County by Tuesday after...with areas further S experiencing the change over 
sooner. Although there is potential for sgnfcnt to heavy snfl for 
western an far northern portions of the forecast area...this storm track is subject to 
change over the next 2 to 3 days given the uncertainties of the long 
wave pattern surrounding this system. 


For now we have increased probability of precipitation to hi likely Cat Monday night and Tuesday 
and then gradually lower them to hi chance category by Wednesday to reflect 
the uncertainties this far out in the forecast. Precipitation types were 
generated off carefully crafted hrly temperature grids where the low Monday 
night was posted in the Erly to middle evening...allowing recovery of temperatures 
overnight Monday with increasing low level warm advcn. Also gmos temperatures Monday 
night and Tuesday night were raised significantly to reflect strong low level 
warm advcn conditions and associated cloud cover and precipitation. 


At this time...it appears most precipitation should end as snow showers across the forecast area 
on Wednesday as colder low level air returns...but this might not be the case 
if there is some merit to the European model (ecmwf) solution. 
&& 


Aviation /08z Thursday through Monday/... 
near term: expect hi MVFR to low VFR conditions in north into 
Friday night due to SC ceiling. VFR conditions expected for kbgr 
and kbhb during this time. Snow showers moving across especially northern taf 
sites by Sat after will bring low MVFR clgs accompanied by IFR to 
MVFR visibilities which will continue into Sat night. Downeast sites will 
experience hi MVFR to low VFR clgs and visibilities during this time. 
Conditions should improve to VFR most sites by sun...xcpt perhaps 
kcar and kpqi which may hold on to MVFR clgs much of the day. VFR 
conditions anticpated Monday with hi/middle clouds...with perhaps MVFR 
conditions in rn/snow late at kbgr and kbhb. 
&& 


Marine... 
have initialized the wind grids with a 50/50 blend of the nam12 
and gfs40. With cold air temperatures over upper 40 degree sea 
surface temperature have raise model blend wind speed around 3 
knots. For waves: have used the blend of Swan model. Wave models 
running a little low so will increase wave heights 1 foot through 
period to compensate for low model wind speed. Will extent Small Craft Advisory 
until 1500z. With off-shore wind and latest spectral showing no 
significant incoming long period wave...expect waves to subside as 
winds diminish. 


Went with msly ww3 for waves and a blend of GFS/NAM/sref in short 
range...lending more toward GFS MOS in the long range for winds. 
We actually reduced winds to just below gale levels late Monday night 
into Wednesday morning given uncertainties of track and intensity of low 
pressure expeceted in the vicinity of the waters at this time. 
&& 


Car watches/warnings/advisories... 
ME...none. 
Marine...Small Craft Advisory until 10 am EST this morning for 
anz050>052. 


&& 


$$ 


Near term...mignone 
short term...vjn 
long term...vjn 
aviation...mignone 
marine...mignone/vjn 

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