Area Forecast Discussion

FXUS61 KGYX 201142
Area Forecast Discussion
National Weather Service Gray ME
642 AM EST Tue Feb 20 2018
A warm front will cross the region from south to north today. A
cold front will cross the region late Wednesday, and stall south
of the area Thursday. High pressure build in for Friday.  A 
series of waves moves across the area this weekend with light 
rain or snow possible, although the most significant will move
through Sunday.
6am update: A few areas of dense fog now being reported as the
sun rises. Have issued an SPS and updated to include Patchy 
dense fog for the next few hours. 
Overview: High pressure off to our east will continue to 
generate southwesterly flow pushing unseasonably warm air into 
the region through the next several days. 
Today:Band of light showers associated with a warm front will 
continue to life north through the area this morning. 
Temperatures have climbed to the freezing point across the 
entire region and so the remaining Winter Weather Advisory has 
been dropped with this forecast update. 
Temperatures will continue to warm throughout the day, reaching the 
60s across southern New Hampshire. In Maine it will not warm up 
quite as much. Along the coast this is due to the flow coming off 
the cold ocean water. Interior Maine will also remain in the 40s as 
the current cold air will be slow to make it out of the region. 
While shower activity will lift northwards some clouds will 
remain for much of the day, especially along the coast.
Overnight expect just a slight drop in temperatures as the overall 
warm advection continues. With dewpoints in the 40s moving over the 
snowpack fog will be widespread across the region, and dense fog is 
Wednesday will be the warmest day of the week as the bulk of the 
warm air moves into the region. This anomalous air mass is forecast 
to reach near record levels. Daily records for our climate sites 
appear below. Have gone with high temps at daily record levels for 
all three locations, but stopped short of the all time February high 
temp records which are just a few degrees higher. These temperatures 
will certainly be a refreshing break from winter, and most locations 
have not seen 60F since early November. 
While confidence is high for these record temperatures across New 
Hampshire and interior western Maine, the midcoast is not going to 
be as warm and is a much lower confidence forecast. Our ocean 
temperatures continue to run near 40 degrees which will limit the 
high temperatures coastward of Rt 1 from Portland east. Despite the 
trend through the day towards a more westerly wind a slight sea 
breeze is likely to take hold keeping the immediate coast in 
onshore flow. Another consideration is sunshine. Forecast 
soundings for RKD continue to show a Marine layer remaining 
through the day. Without a break in the fog these locations may 
struggle to reach the upper 40s let along 50.
A quick look at the 500 mb pattern across NOAM and vicinity
shows some flattening of the strong wrn Atlantic ridge late 
this week, moving the more active part of the jet over the CWA 
late this week into the weekend. Temps will moderate back closer
to normal, but should still trend on the warm side of normal. 
This active flow will also produce several waves, making for an 
unsettled period, with the chance of some rain or snow. This 
should mostly be light, but some areas could see several inches 
in wave that moves through on Sunday.
For Wed night, front will be exiting the CWA during the evening,
with temps dropping from their near record warm on Wednesday. A
few showers may be possible in the evening over the north, but
for the most part this front looks dry. Overnight lows will
still be mild for late Feb, generally in the low to mid 20s N,
to the low to mid 30s S.  
On Thu, the front briefly stalls to our south, as a weak wave 
moves along it, this will keep some clouds in the southern half
of the CWA /with an outside chance of some showers/, and also 
prevent the core of colder air from moving south into the CWA. 
So, with W_NW winds downsloping will allow for highs in the low 
40s in southern NH and the ME coast, with generally mid to upper
30s elsewhere. Sfc high builds over the nrn CWA Thu night into 
Fri, and the 500mb ridge nudges back to the N, so look for 
partly to mostly sunny skies with highs in the 30s to low 40s. 
The weekend will see two fast-moving wave move thru, the first
will be Fri night, and the second Sunday into Sunday evening.
The first wave look like it could bring some SHRA/SHSN to the 
region, although the best chance will be in the nrn zones, and 
any snow accums will be light. The second which will move in 
Sunday, looks a little bit more impressive, although still not 
strong, but could produce a period of snow to rain near the 
coast, and a few inches of snow in the north. Saturday will be 
mild with highs mostly in the 40s, although cooler near the intl
border, and Sunday will see highs closer to normal generally in
the 30s.
Short Term...Widely varying conditions out there tonight as
showers and moist air over snow create low ceilings and fog
across the region. LIFR will continue along the coast through
daybreak with scattered IFR and MVFR in the interior. Conditions
will improve slightly to MVFR today before once again seeing
dense fog and IFR to LIFR overnight tonight. Tuesday will be VFR
for all but the midcoast where onshore flow will keep low
ceilings around through the day. 
VFR conditions across the region will come to an
end late this evening as increasing clouds and showers move in
and a warm front enters the region. Increasing dewpoints over 
the snowpack will result in fog overnight dropping conditions to
IFR and locally LIFR across the region. Tuesday will have a
gradual improvement for all but the immediate coastline where 
IFR in low ceilings may remain throughout the day. Fog becomes
widespread once again Tuesday night.
Long Term...Mainly VFR Wed night into Friday. Some MVFR to IFR may
be possible Fri night in SHRA/SHSN.
Short Term...A south to southwest flow will continue over the
region through Wednesday. While winds have subsided, seas remain
near 5ft on the outer waters and SCAs continue for this region.
Long Term...A brief period of NW SCA level winds/seas possible 
Wed night, but otherwise winds and seas should stay below SCA
levels into Saturday.
Have issued a flood watch for the potential for ice jam flooding. 
While total QPF amounts with these showers remain small the warm 
temperatures will begin to melt off the snowpack, and snowpack 
density analysis through the southern portion of the area 
supports the runoff. While the melt won't be enough to cause 
flooding on its own, forecast hydrographs suggest the potential 
for enough rise to move ice. With several ice jams already in 
place the concern for ice jam flooding is increased and thus a 
flood watch has been issued for western New Hampshire where the 
combination of temperatures, QPF, and existing ice jams coexist.
Further south in NH little snowpack and river ice remains while
across Maine temperatures remain lower, especially through the 
headwaters and less runoff is expected so no flood watch is 
NH...Flood Watch through Wednesday evening for NHZ001>003-005-007.
MARINE...Small Craft Advisory until 5 PM EST this afternoon for ANZ150-
NEAR TERM...Curtis