Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
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FXUS61 KGYX 241803
Area Forecast Discussion
National Weather Service Gray ME
203 PM EDT Fri Mar 24 2017
A warm front will cross the region today, and then shift
southward as a cold front Saturday. High pressure will build in
Saturday night and Sunday. A series of lows will track across
the region Sunday night through Wednesday and make for an
unsettled period with some bouts of rain or wintry
precipitation. High pressure builds in for the end of the week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --2 PM update... Quick update to issue winter weather advisories
for central and northern New Hampshire. Models doing poor job on
intensity of over-running and consequently QPF with this over-
running precip. Many locations reporting vsby below 1 mile and
moderate to occasionally heavy snow across areas of the
advisory. With plenty of activity upstream to come...now looking
for accumulations of 3 to 6 inches these areas. No other
changes planned attm.
Very dry airmass in place over the region late this morning
resulting in hit and miss areas of light to moderate snow and
gusty winds. Still expecting some minor accumulations through
early afternoon as the airmass saturates and cools in interior
sections of Maine and New Hampshire. Temperatures will
gradually increase through the afternoon and boundary layer will
warm enough in southern zones for precip to mix with rain and
eventually go over to plain rain showers. Have update pop/wx
grids to relect current radar trends. Aside from a few temp/td
tweaks no other changes planned attm.
7AM UPDATE...Will update the forecast based on early morning
temperatures. Regional radar imagery shows widespread echoes
which have been moving through Vermont and even into New
Hampshire and Maine at times. Have yet to see reports of any of
this reaching the ground as there remains a very dry layer of
air below this. It will moisten up later this morning, though.
Surface high pressure over the area early this morning will
shift east today, bringing a southerly flow to the region which
will help to push out the cold air. Westerly warm advection flow
will be ongoing aloft today, bringing increasing clouds and
eventually precipitation. Precipitation will become more focused
along and ahead of a warm front which will move southwest to
east across the area today. Atmospheric profiles indicate that
conditions will be cold enough for snow formation ahead of the
warm front, with surface temperatures playing the critical role
in whether snow or rain reaches the surface. It is likely that
temperatures initially warm this morning, but as precipitation
arrives and falls into the low level dry air, evaporational
cooling will bring surface temperatures down closer to freezing.
As a result, expect most of the area to see some snow today,
with a possible transition to rain this afternoon and evening as
the precipitation comes to an end. There is not a ton of
moisture available with this system as it is arriving from the
west (off the continent) and does not have a lot of organized
lift with it. But total liquid precipitation amounts of 0.1 to
0.25 inches is likely, which could translate to 1 to 3 inches of
snow. The ability of snow to accumulate will be impacted by
surface temperatures which are expected to be near or possibly
above freezing for a good part of the area. Thus if snow does
accumulate it may melt quickly afterward.
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.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Any lingering precipitation should depart to the east early this
evening as the warm front pushes through. There may be some
lingering upslope precipitation in the mountains on the low
level westerly flow. Temperatures across most of the area stay
in the 30s tonight, in some cases above freezing. But by morning
a cold front will be dropping down from the north which will
bring colder temperatures and drop northern areas into the 20s.
As the front arrives in southern New England during the day
Saturday, a weak wave will be moving east along the front. This
will spread some precipitation into southern parts of New
Hampshire. Precipitation type will again be dependent on
surface temperatures, and at this time looks likely to be mostly
rain. But there could be some areas of light snow especially on
the northern edge. Warmest temperatures on Saturday may well be
toward the midcoast of Maine where there could be some sun to
bring the temperature into the mid 40s.
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Overall, 500mb pattern in the extended will lean toward weakly
amplified zonal flow, with multiple waves, but nothing becoming
very amplified. Should see enough of a trough get carved out of
the flow by mid-week as it moves to our east, then we will some
ridging at the end of the week.
Models tend to be in agreement that cold front will shift far
enough south Saturday to allow some ridging to build in through
Sunday. So, have backed off pops a little more in this
timeframe. But this airmass will be cool with lows Sunday
morning back into the teens to mid 20s, and highs on Sunday
mostly in the 35 to 40 range, so a few degrees below normal.
Sunday night will see WAA return as weakening trough shifts NE
thru the Great Lakes as it runs into ridging aloft. The trend
is for less QPF Sunday night, given the strong ridging, but if
anything falls, many spots will be cold enough for either light
snow or freezing rain. This system is slow moving, and light
precip will likely linger into Monday, although with a gradual
warming trend, so precip should go over to rain in all but far
northern zones, with highs mid 30s to low 40s. Secondary wave
moves through Tuesday, and will likely see another round of
light precip, which could once again show some wintry
characteristics Tuesday night before cold front swings through
early Wednesday. Digging trough to our N and E should keep us in
drier NW flow for the latter part of the week, with temps
closer to normal.
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Short Term...VFR conditions this morning become IFR to possibly
LIFR in light snow late this morning into the afternoon. Snow
may transition to rain through the afternoon especially in
southern parts of the area. Could see VFR conditions return to
parts of the area overnight tonight.
Long Term...Should see mainly VFR Saturday into at least Sunday
morning. Then expect deteriorating conditions late Sunday into
Sunday night in mixed precip. Expect IFR late Sunday night into
Monday, with maybe some improvement to MVFR at times Monday
night and Tuesday, but expecting an extended period flight
restrictions for Mon- Tue.
Short Term...A southwesterly flow will develop this afternoon
behind a warm front. Winds could gust to 30KT at times, and a
Small Craft Advisory has been issued. Winds just above the
surface will be fairly strong, but the low levels of the
atmosphere should remain at least somewhat stable on the warm
advection flow, so we should remain below gale force winds
Long Term...SCAs possible due to wind on Monday, and then
potentially for seas Mon night into Tue.
-- Changed Discussion --ME...None.
NH...Winter Weather Advisory until 9 PM EDT this evening for
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ150>154.
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