Area Forecast Discussion
Issued by NWS Portland, ME-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KGYX 201624
Area Forecast Discussion
National Weather Service Gray ME
1224 PM EDT Thu Apr 20 2017
-- Changed Discussion --A cold front will remain just off the coast today. Clouds will
increase tonight ahead of a low pressure system moving out of
the great lakes. Rain will move in overnight and Friday then
continue through Friday night. The mountains will see a change
over to snow overnight Friday before ending as a cold front
sweeps through Saturday morning. Weak high pressure builds in
for Sunday before another period of unsettled weather to start
-- End Changed Discussion --
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
-- Changed Discussion --1222 PM...Minor ESTF update to reflect current mesonet as well
as satellite trends.
920 AM...At 13z a west-east frontal boundary was stalled to our
south with a 1019 millibar low situated along it over southeastern
New York State. A surface trough extended northward through
eastern New England. A 1032 millibar high was situated over the
southern tip of Hudson Bay. For today...the weak wave will
ripple along the boundary and turn the flow onshore along the
coast by mid day. The 1032 millibar high will briefly nose into
the region from the north and there may be some short lived
breaks in the overcast over northern and interior sections of
the forecast area. Otherwise...lingering low level moisture and
a predominantly onshore flow will make for a mostly cloudy day.
Temperatures will struggle to reach the 50s today with 40s
along the international border.
650 am...Just a few minor changes to POPs/T/Td based on current
trends, but otherwise forecast unchanged for today, with a lot
of clouds, but mainly dry weather.
Previously...Weak cold front moving SE of the CWA early this
AM, which will slow and become stationary across southern New
England today. Will see weak flow develop this morning, which
may mix some drier air down and produce a few breaks sun inland
areas from mid-morning thru early afternoon, but for the most
part there will be more clouds than sun. Coastal areas will
likely get stuck in the clouds, as the N flow is too weak to
overcome any onshore density current that gets going once things
start warming up. Temps will be warmer given at least a morning
of no onshore flow, so highs will range from around 50 in the
mountains and on the mid-coast to near 60 in interior srn NH.
Might see some spotty DZ late this afternoon in the upslope
areas of the foothills as SE flow begins to increase ahead of
the next approaching system.
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.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Compact 500 mb closed wave crosses the Great LAkes tonight, and
gets a shot of energy, showing some negative tilt there before
it lifts NE across srn Quebec FRi and Fri night as it fills.
This will allow for one sfc low to track with the wave aloft to
our N, and another to develop along the stalled front to our
south. HEaviest precip will generally and north, but will see
rain moving in from the SW tomorrow night and continue into
Friday. The more significant QPF, and this is only on the the
order of a half inch will be late tonight into Friday morning
when remnant convection and best dynamics passes just to our
NW. Lighter rain will persist through the day Friday as we
remain between the weakening system to the north and the
developing system to ours south. For the most part this will
fall as rain, although higher elevations could see some snow,
this will mostly above 4K ft in this timeframe, although the
elevation for snowfall will lower Fri night.
It will be cool through the period as the developing low to our
south cuts any hope of warmer air moving in and we remain in
E-NE flow. Overnight lows tonight will be in the mid-upper 30s
in the mtns, and in the 40-45 range on the coastal plain and in
srn NH. Highs Friday will be lucky to see temps rise by about 5
degrees, maybe reaching 40-45 in the mountains, and 45-50 in
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
A short wave aloft currently over Montana will move east
through the end of the week bringing low pressure into northern
New England for the start of the weekend. Rain will be
widespread on Friday and continue overnight before coming to an
end on Saturday morning. While initially on Friday everywhere
will start as rain expect to see a transition to snow at the
higher elevations overnight as the cold air aloft moves in. This
will result in up to an inch of accumulation, mostly above
2500ft. Neither sleet nor freezing rain is a concern here as
there is minimal warm air aloft and surfaces are too warm to
freeze on contact. Rather expect wet snow or snow mixing with
rain in the overnight hours.
Weak high pressure begins to build in on Saturday night and
crests over the region on Sunday. This high will simply trap any
remaining moisture at the surface giving cloudy skies and some
possible fog along the coast. There is a low chance for the area
to break out of the clouds, in which case a sea breeze could
develop but overall feel the cold damp option is more likely
and have stuck with overcast skies.
On Monday the forecast area is further squeezed between two
systems as a cold front passes to the north and a low moves
south of the area. Again look for widespread clouds with showers
possible in southern New Hampshire.
On Tuesday the cold front in the north tries to combine with the
low off shore to bring more widespread precipitation across
especially the eastern portion of the forecast area. This is a
possibility but a rather low confidence forecast at this point
and have just stuck with a mild mannered blend of options for
the rest of the forecast package at this point.
.AVIATION /16Z THURSDAY THROUGH MONDAY/...
Short Term...For the most part IFR or lower will prevalent
through Friday. Will see some improvement to MVFR today,
especially away from the coast, and may see some VFR late
morning into the afternoon at interior NH terminals, but all
locations can expect to return to IFR or lower tonight in
rain/fog and low cigs. These conditions will persist into
Friday, and coastal terminals could see E-NE winds gusting to
20-25 kt at times on Friday.
Long Term... Widespread IFR in rain will continue Friday night
into Saturday morning. Conditions will then improve to MVFR
region wide for Sunday, with a chance for IFR creeping crud
during the overnight in coastal locations.
Short Term...SCA seas persisting, but subsiding through early
morning, as are winds. So the 10Z expiration time of the SCA
looks reasonable. Will get a break today , but developing low
pressure to our south will begin to produce strengthening E-NE
flow tonight with SCA conds returning late tonight and on
Long Term... Small crafts will again be needed Friday overnight
into Saturday morning.
Moist onshore flow will persist into Saturday, with below
normal temps precluding any fire weather threat thru the