Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 191637
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1137 AM EST Mon Feb 19 2018

.SYNOPSIS...
High pressure will move east of northern New England today. A
warm front will move north of the region Tuesday and usher in
very warm air for this time of year. A cold front will move
through Thursday ushering in cooler air for the end of the
week. Another two areas of low pressure will move northeast from
the Ohio River Valley next weekend. These systems will bring
more unsettled weather and possibly mixed precipitation to
portions of Maine and New Hampshire.

&&

.NEAR TERM /THROUGH TONIGHT/...
Update...
Temperatures climbed very rapidly this morning with good mixing
and partly to mostly sunny conditions. Temperatures are now
near 40 degrees in most areas. The exception was in the
mountains where an inversion has kept readings in the 30s.

Southerly winds will continue to increase this afternoon with an
increase in cloud cover, slowly down our quick ascent in
temperatures. Mesoscale models suggest the area of rainfall
associated with a weak short wave and warm air advection over
upstate New York will continue to race eastward today, bringing
precipitation to western portions of the region by around 21 or
22Z.

Prev Disc... Have updated the forecast based on current
conditions and latest set of mesoscale models. Depsite a cold
start, have adjusted temperatures into the 40s for most areas
for high temperatures. Warm air advection and initially, a very
dry airmass will allow for readings to climb quickly this
morning. Thereafter, clouds will stream in from upstate New York
during the afternoon hours.

Prev Disc... 6am update... minor adjustment to temperatures
which have bottomed out in the single digits in the mountain
valleys and will start to rise with the sun.

prev disc...
A warming pattern begins today as high pressure moves off to our
east allowing southerly return flow to set up. Early morning
temperatures have dropped into the single digits across the
north in sheltered valleys where clear skies have helped the
radiational cooling. The February sun will help temperatures
rise early and continue warming through the day as the south to
southwesterly flow takes hold. High temperatures will climb into
the 40s across the area.

&&

.SHORT TERM /TUESDAY/...
Within the southwesterly flow, a weak short wave current over
western New York will move through the ridge late this evening
pushing a warm front through the region overnight. This will spread
precipitation across the area, in the form of scattered
showers. With temperatures both aloft and at the surface well
above freezing most of the area will see this as light rain
showers. The one region for mixed precipitation will be from
Rangeley into Jackman and Central Somerset county. Here the low
temperatures will hover at or just below freezing, which may
result is some light icing, especially in the mountains above
2000ft. With no significant mixed precipitation expected in the
populated valleys will not issue an advisory for this marginal
event. Overnight also expect fog to become widespread as warm
air moves over the snowpack and begins to saturate. Pockets of
dense fog are possible.

Tuesday temperatures will continue to climb as 850mb
temperatures climb to near record levels (Feb max observed 850mb
temp at KGYX is 13C). With the southwesterly flow this sets up a
classic spring scenario, wherein New Hampshire and extreme
southwest Maine climb into the 60s, while from Portland east
through the midcoast onshore flow over 40 degree water keeps
temperatures down and fog and low clouds of a marine layer in
place. This is reflected well in forecast soundings which show
a large surface inversion for KRKD and KPWM and a well mixed
region further west through the CT river valley. With the warm
advection just setting up, expect highs to remain below record
despite reaching 60 across southern New Hampshire. (see records
in Long term section below)

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
In the long term unsettled weather and very warm to much cooler
with even some mixed precipitation over the weekend.

A warm front lifts north of the forecast area Tuesday. This
will lead to potential record breaking warmth on Wednesday.
Currently forecasting record high temperatures for both Portland
and Concord.

***Records for PWM & CON***
        TUE        WED
PWM     61/1994    59/1953
CON     66/1930    64/1872

Expect areas of fog into Wednesday morning with light rain.
skies should become partly cloudy Wednesday afternoon allowing
the temperatures to soar during the day. Some locations in
southern New Hampshire may reach 70 degrees.

A cold front wing swing through Thursday morning with some light
rain/showers and much cooler. high pressure builds in Thursday
afternoon.

Models differ a bit on the system for late Friday and Saturday.
ECMWF is faster than the GFS. Right now have chance POP for
Friday afternoon. Precipitation will likely be snow north and
snow to mix central and to mix and then rain southern locations.
Forecast gets more muddled Sunday as GFS is bullish on surface
low development near the benchmark. For now have snow and mixed
precipitation changing to rain coast then back to snow Sunday
night.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Short Term... VFR conditions across the region will come to an
end late this evening as increasing clouds and showers move in
and a warm front lifts through the region. Warm dewpoints over
the snowpack will result in fog overnight dropping conditions to
IFR across the region. Tuesday will see VFR return for all but
the immediate coastline along the midcoast where IFR in low
ceilings remain possible throughout the day.

Long Term...IFR/LIFR Tuesday night into Wednesday morning in
fog and rain. Conditions improve to VFR Wednesday afternoon.
MVFR expected Wednesday night as cold front moves through then
VFR Thursday. IFR returns Friday as surface low approaches from
the southwest.

&&

.MARINE...
Short Term... Increasing southwesterly flow around the departing
high pressure will push winds and seas to Small craft criteria
and an SCA has been issued for the outer waters, as well as
Penobscot bay where the SW flow is favorable for building seas.

Long Term...Small Craft Advisory likely for Wednesday as winds
increase from the southwest and increasing seas.

&&

.HYDROLOGY...
Will be monitoring the rivers over the next few days as the
warm weather and some rain may lead to enough runoff to cause
ice jam flooding. There are several locations with ice jams in
Maine and New Hampshire. Looks like a 72 hour period or longer
with temperatures remaining above freezing. It is possible that
the warmer weather will weaken the ice so that any rise in river
levels will just move the ice harmlessly downriver. QPF should
be fairly light with less than a quarter inch expected Monday
night through Wednesday in the south and up to an inch in the
far north near the Canadian border.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 5 AM EST Tuesday for ANZ150>152-154.

&&

$$
JC


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