National Weather Service Raw Text Product

Bulk Download

Start UTC Date @0z:
End UTC Date @0z:

FXUS61 KGYX 201937

Area Forecast Discussion
National Weather Service Gray ME
337 PM EDT Sat Oct 20 2018

A trough of low pressure will linger over the region tonight. A
strong northwesterly flow will set up over the region on Sunday
as high pressure builds in from the west. High pressure will 
crest over the region early Monday before shifting offshore. 
Low pressure will approach from the west Monday night and will 
cross the region Tuesday and possibly redevelop along coastal
areas Tue night. Low pressure will shift into the maritimes 
Wednesday. High pressure will gradually build in from the west 
Thursday through Friday.


The cold air arrives on two boundaries that move through, the
first of which passes thru the CWA this afternoon, and shifted 
winds more westerly, and have lowered Tds a bit. A second surge 
of cooler air will move through coincident with the 500 MB 
trough axis which moves through Sunday morning. A wave will move
along the sfc front to our south and will push some clouds back
to the N toward daybreak and into early Sunday morning. A few 
light SHRA or spkls may be possible across the srn tier of NH 
zones, with best timing for this 08-12Z. There's some cold air 
advection, but sfc flow weakens ahead of the next wave this 
evening, so winds diminish tonight. Lows will fall into the low 
30s N to around 40 in the south. 


By mid morning Sunday, should see skies start to clear and winds
begin to pick up in the NW downslope winds outside of the mtns.
Winds will likely gusts to 25-30 mph at times on Sunday, 
especially in the afternoon. CAA will battle with the downslope
on the coastal plain and highs there will be in the mid to 
upper 40s, while the mtns, with more clouds, will see highs in 
the lower 40s. 

Winds diminish somewhat around sunset, and skies clear out 
everywhere. But, NW flow will persist enough to prevent much rad
cooling. Still, cold enough aloft, to push lows into the 20s in
most spots.  


Keeping a very close eye on the high amplitude progressive 
upper ridge that becomes progressive to 110W with rapidly rising
heights. This will be the key in driving southeastward several 
powerful s/waves that will move thru Saskatchewan and Manitoba 
early in the week and then thru the Great Lakes by Tue. U.S. 
models have always had a history of poor performance with these 
short waves moving thru those data sparse areas of Canada where 
EURO has performed well. Ole rule of thumb also dictates 
potential significant closed upper low development along 
northeast corridor 72-96 hrs after movement into the 110W area 
with rapid height rises. With that said, EURO preferred model 
and shows an outcome scenario that one would expect as it 
continues to hint at the scenario of coastal development late 
Tue into Wed. It would be a fools errand to try and predict 
outcome at this point, but will begin nudging and hedging 
forecast to EURO solution by increasing POPs and avoid flip
flopping of forecast for Tue into Wed time frame. Will lower 
guidance temps during the event as decent UVV and dynamic 
cooling would cause decent dynamic cooling and overcome warmer
boundary layer temps.

Will increase POPs for Tue for initial light overrunning mixed 
ptype as a baroclinic zone begins to set up to our south. The 
pcpn may increase and turn to snow over much of the area Tue 
night depending on strength of digging s/wv and redevelopment 
along or just off the ME/NH coast. Confidence not high yet for 
anything more than a broadbrush approach Tue night into Wed.

Behind the system, mid to late in the week models agree on 
large upper low that gets carved out into the maritimes allowing
a strong and very cold northwest flow to develop. Expect 
orographic snow showers in the mountains with some light 
accumulations. Downsloping areas should remain dry. Expect temps
to be too high for late in the week due to the climo weighting
function (time of Year) vs the very cold h85 temps due to upper
closed cyclonic flow over the northeast, for now just tweaked
them to stay within collaboration ranges.


Short Term...Mainly VFR though Sunday night. Will see gusty NW
winds during the day Sunday reaching to 25 kts or so, but
diminishing around sunset.

Long Term...VFR Mon, but deteriorating conditions to MVFR/IFR 
Tue and possibly into Wed depending on potential development and
track of coastal low. Cyclonic flow aloft will keep MVFR 
conditions in snow showers in the mtns but downsloping areas on 
the northwest flow will keep those areas VFR.


Short Term...SCA will hold for now as we still see some
borderline wind gusts and seas are still 4-7 feet. Will see a
break overnight, but winds pick up again Sunday morning and a 
period of gales are expected in the open waters Sunday afternoon
and evening. 

Long Term...Timing and location of development of potential 
coastal low in the Gulf of Maine late Tuesday into Wed will
determine strength and timing of backing northwest winds in its
wake. A lot of uncertainty remains for Tue night into Wed but
Gales may be needed by Wed.  


Gusty NW winds and dry air will produce near red flag conditions
in the mtns on Sunday. Although windy near the coast as well, RH
values will be more moderate, generally 40-50 percent. 


MARINE...Small Craft Advisory until 7 PM EDT this evening for 


LONG TERM...Marine