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Area Forecast Discussion (AFD)

Issued by Caribou, ME (CAR)

                            
000
FXUS61 KCAR 181951
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
351 PM EDT Mon Mar 18 2019

.SYNOPSIS...
High pressure will build toward the area tonight then crest over the 
region Tuesday into Tuesday night. High pressure will move south of 
the area Wednesday. A trough of low pressure will approach Wednesday 
night then move over the area on Thursday. 
&&

.NEAR TERM /THROUGH TUESDAY/...
Some spotty flurries or snow showers may be around early tonight as 
the trailing end of some moisture from the Maritimes trough slides 
through. Otherwise, the sky will trend more clear overnight as 
high pressure builds in from the west. The high will build over 
the area Tuesday bringing a dry day. However, soundings are 
again showing an unstable layer up to 5-6K ft. This will likely 
produce cumulus over the area again on Tuesday, especially 
across the north, so a partly cloudy sky north to mostly sunny
Downeast is expected. Winds will generally be light with the 
high building in.
&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
For Tuesday night, expect light winds and clear skies. This
means a shallow radiation inversion will yield subzero readings
in Aroostook County and single digits elsewhere. The inversion
will break quickly Wednesday morning. Warm air advection and
southwest winds will allow highs to reach the upper 30s to
around 40F Wednesday afternoon. The warm advection continues
Wednesday night and there will be some high clouds. Anticipate 
lows will only drop to the upper 20s north and lower 30s south.
Things become very interesting on Thursday. Previous forecasts
increased pops fairly quickly with a weak frontal system.
However, signs are increasing that this system will tend to
stall while a more significant system developing towards the
mid-Atlantic coast...or even towards Cape Hatteras...will spread
moisture northward later in the day. With temperatures rising
into the 40s on Thursday, most precip will start as rain.
However, all warm air will be in the boundary layer. Thus,
precip may mix with snow or change to wet snow as evaporative
cooling occurs.  
&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The period Thursday night into Saturday represents one of the
more interesting and dynamic situations from a long, snowy
winter in northern Maine. Guidance is having a difficult time
handling the exact details of a powerful upper ridge building 
in the western US while a major upper trough digs in the eastern
US. The key details involve how far this upper trough digs into
the southeastern US, the longitude of the trough axis and how 
it phases with a rich supply of southern stream moisture off the
Carolinas on Thursday. While a lot of earlier guidance didn't 
suggest all of these elements could successfully phase...except 
GFS FV3...both ECMWF and GFS now show a bomb developing along 
the east coast. The difference is that the ingredients come 
together later with the GFS, the storm is more of a miss to the 
east for Maine, and it's not as deep as the ECMWF. Have leaned 
somewhat towards the 18/00Z run of the ECMWF and GEFS mean for 
this forecast, but did not integrate the explosive/eye-popping 
18/12Z ECMWF run at this time. This run shows the potential for 
a major Nor'easter with surface pressures diving to 973mb over 
Downeast Maine. Since there's not a lot of cold air in place, 
the risk is for heavy wet snow. Heavy wet snow followed by high 
winds later Friday into Sunday heightens concerns about power 
outage potential. This potential storm also coincides with high 
astronomical tides. The next 24 hours should provide better 
clarity to this potential high-impact situation as models get a
better handle on key details.

Regardless the storm's exact track, winds will be the primary
issue through the weekend. The expectation of heavy, wet snow
will mitigate drifting and blowing snow.
&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
NEAR TERM: VFR conditions are expected across the area tonight
through Tuesday. 

SHORT TERM: Expect VFR conditions Tuesday night into Thursday
morning. Conditions will deteriorate to IFR Thursday afternoon
due to both cigs and snow. The trend for Thursday night into
Friday will be towards LIFR due to snow and cigs. There is a
possibility of significant snow affecting rwy conditions Friday.
Conditions improve towards IFR Friday night. By Saturday, 
expect VFR for BGR and BHB, but MVFR tempo IFR in snow showers 
north of GNR and HUL. 
&&

.MARINE...
NEAR TERM: Winds and seas should be below SCA tonight and Tuesday as high 
pressure builds over. 

SHORT TERM: The major issue will be the potential development a
major East Coast storm late in the week. The current forecast
calls for SCA conditions Friday afternoon into Monday, but the
odds of a strong gale are trending upward for Friday into
Saturday. This storm may also coincide with the highest
astronomical tides of the month on Friday.
&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$

Near Term...Bloomer
Short Term...MCW
Long Term...MCW
Aviation...Bloomer/MCW
Marine...Bloomer/MCW