FXUS61 KGYX 100236

Area Forecast Discussion
National Weather Service Gray ME
1036 PM EDT Thu Apr 9 2020

Moderate to heavy rain, snow, and some sleet are expected
through this evening as a coastal storm deepens and moves along
the coast. Winds will also be gusty this evening. The storm
will move quickly out of the area later tonight, leaving behind
cooler temperatures and snow squalls in the mountains for
Friday. Winds will be gusty once again on the backside of the
system. High pressure returns on Saturday with temperatures
running above normal this weekend. The next system arrives
Monday with heavy rainfall possible.


1030PM UPDATE...
Snow continues to wrap around the rapidly intensifying low over
the Gulf of Maine, however the back edge has made its way into
western Maine. Thus have dropped some of the winter weather
headlines. Additional snow showers are possible tomorrow, but
accumulations should be minor and primarily in the mountains.
Wind Advisory remains until midnight for southern New Hampshire
and a few gusts to 40 MPH have been observed.

Have updated the forecast with latest thinking on snow totals
and timing, although not a lot of change was made. Upped the
totals a bit near Augusta where the most prolonged period of
onshore moisture surge continues through the evening. We can see
the low wrapping up even on radar imagery and expect a
continued area of heavy snow falling within the wrap around area
mainly across western Maine this evening. With the heavy wet
nature of the snow and temperatures mostly above freezing, think
that a significant amount of compaction will occur which will
lower storm total snowfall amounts from what might otherwise be
reported. But it seems like a very heavy, thick 10 or 12 inches
is likely just inland of the Midcoast with higher totals further
north. Current headlines fit the latest forecast thinking well,
although we will likely be able to drop parts of the winter
headlines early. As for wind, there is still a chance of gusty
west winds this evening in southern New Hampshire, though it
seems this should be timed for later in the evening closer to
midnight when the best cold advection begins down there. Will
maintain the Wind Advisory, though confidence in criteria being
met has lowered.

We are upgrading the Midcoast to a Winter Storm Warning as
mesonet obs show temperatures right around 33 or 34 degrees with
snow falling in most of these zones. Immediate coastal locations
like Rockland airport are still 39 and rain, but even here this
is expected to change. Similar impacts expected here as
mentioned in prior update further southwest.

We have decided to expand the Winter Storm Warning a bit
further south into central Cumberland County and advisory for
interior York and coastal Cumberland. This is based on
observations showing very heavy wet snow falling and expanding
southward. Although the back of the precipitation is approaching
through New Hampshire at this time, we expect redevelopment as
the low strengthens in the Gulf of Maine this evening. The heavy
wet nature of the snow will make it even more slippery than
normal and could weigh down tree branches enough to cause power

A coastal storm continues to develop this afternoon over
eastern Massachusetts. Latest CAM models show the system hugging
the coast through this evening, pivoting and continuing to
deepen as it rotates across the coast. We are already seeing a
mix of p-types across the area, including rain, snow, sleet, and
graupel with the stronger convective elements. Temperatures
aloft are isothermal, so as melting and other processes continue
many places will switch back and forth between liquid and
frozen precipitation. As far as convection is concerned, most of
the instability remains to the south. However, rapidly
increasing lapse rates have created conditions favorable for
lightning over the area. This chance for thunderstorms will
remain in the forecast through this evening.

Expecting snowfall rates to be in the 2-3" range at the height
of the event later tonight as frontogenesis is maximized in the
dendritic growth zone, causing heavy, wet snow to pile up
quickly. There will be a tight snowfall amount gradient between
the advisory/warning level in place, so some areas may get very
little as they mix in with rain along the coast, while on the
northern side of a county higher amounts may be realized.

Snow will eventually become the dominant precip type tonight as
colder air is pulled south on the backside of the low. Where it
will be mostly rain, liquid precipitation rates will also be
high, at least an inch an hour. This may cause some poor
drainage flooding at times. A dry slow should arrive in the
early morning hours and erode precipitation across southern NH
and SW ME.

Strong winds throughout the column will mix down to the surface
in any heavy precipitation. In particular, along the Mid Coast
where the onshore component will be strongest, a wind advisory
remains in place for gusts to 50 mph. In addition, similar wind
speeds are likely for southern NH as the storm tucks in along
the MA/NH coastlines and downward momentum transfer brings
higher winds just off the surface to the ground.

Temperatures will not vary much overnight but should cool into
the upper 20s to lower 30s.


The system pulls away and lingers near Bangor, ME tomorrow
morning before pushing into the Canadian maritimes. Strong NNW
winds will continue to usher in colder air, and MOS guidance is
becoming more bullish with gusty winds over portions of the
area. May need a wind advisory tomorrow during this time, but
with the current winds advisories and a lull between the two
periods of higher winds, will deal with that once the system is
more or less past.

The upper low remains overhead tomorrow, and will see widespread
rain and snow showers. These will be much lighter than today
except for the higher terrain where RH and winds in the
950-850mb layer will support snow squalls with heavy snow and
low visibilities at times. This will primarily occur between
around noon through 6 pm and affect areas along the CT River
Valley, north of and including the White Mountain National
Forest, and northeast towards Jackman. Some of these stronger
squalls may make it into the foothills but will lose steam as
terrain support decreases.

Highs will reach the upper 30s to upper 40s in the area.


An active, troughy weather pattern continues through the
extended forecast period. Long-range model suites agree on the
upper air pattern during this time, namely with the development
of deep, anomalous troughing over the Plains by the start of the
next week. While this brings down a strong shot of cold air
into the Plains, it leaves us on the warm advective side of
things heading into the next work week. A preceding shortwave
will deliver a shot of moderate to heavy rain early in the week
with a dry trend to follow as troughing shifts east (although
not entirely dry).

On Saturday, breezy northwest flow continues as the trough
responsible for the messy weather today gradually lifts through
the Canadian Maritimes. Upslope snow showers continue near the
international border through the day, then high pressure nosing
in from the southwest gradually clears the area of showers and
most clouds. Expect a fairly nice Sunday with breezy southwest
winds, mostly sunny skies, and temperatures topping out in the
50s to near 60 over the lower elevations as high pressure passes
to the south.

Sunday night, aforementioned deep troughing develops and digs
southward through the Plains, phasing with the southern stream. A
southern stream shortwave kicks out ahead of the long wave and rides
NEward, leading to strong cyclogenesis over the mid-Mississippi
Valley into the Great Lakes Region. Low pressure eventually tracks
NEward into northern Quebec by the end of Monday, during which time
broad warm frontal forcing overtakes the northeast CONUS. As we`ve
seen in numerous storms this cold season...including today, as an
extreme example...re-development of low pressure is probable as the
front reaches the coast, although it seems to be weaker than in
other systems being as detached from parent forcing as it is.
Precipitation may begin in the southwestern zones as early as
Sunday night; model ensembles focus most precipitation during
the afternoon and evening on Monday. Little change in the QPF
forecast with a general 0.75-1.5" focusing on the coastal plain
extending north into the mountains, falling as rain.

Stratiform rain moves out to the northeast Monday night with a
drying trend to follow. The shortwave becomes ingested in the
broader trough which continues to spin overhead into the middle
of the week with enhancements as cold fronts drop down from it.
This keeps shower chances at least in the mountains with a
return to near- normal temperatures.


Short Term...Mostly VFR conditions this morning...though patches
of IFR CIGs are already developing in onshore flow N of the warm
front. Overall conditions will quickly drop to IFR or lower as
precip moves in from SW to NE around midday. Periods of +RA are
likely at most of the terminals...and across Srn NH especially
there may be some TSRA. Confidence is too low for
prevailing...but I did add PROB30 groups to PSM and MHT. Farther
N AUG will likely see a period of +SN when the heaviest precip
arrives late afternoon. RKD may see surface wind gusts approach
35kt this evening...but it should be a short window for
strongest winds. Dry slot quickly moves in this
evening...bringing an end to heavy precip...but lingering MVFR
CIGs stick around into Fri. Significant upslope SHSN are
expected...with local IFR conditions possible in the vicinity of

Long Term...VFR prevails through the weekend with breezy
northwest flow Saturday turning southwesterly Sunday as high
pressure crosses to the south. Widespread restrictions in RA are
expected Monday. Afterward, westerly flow and VFR prevails with
occasional restrictions in -shra especially over the mountains.


Short Term...Coastal storm will rapidly develop in the Gulf of
ME through this evening, and high end gale warnings remain in
effect thru Friday. Will have to watch the CAA behind the
deepening low early Friday...where gusts may approach storm
force well outside the bays.

Long Term...Seas back down below 5 ft by Saturday morning, but
offshore flow may gust near 25 kts over the waters Saturday
afternoon. High pressure crosses to the south Sunday. The next
area of low pressure crosses the region on Monday with
increasing onshore flow, possibly to Gale Force, and increasing
wave action.


A period of heavy rain and some embedded thunder is likely
along the Maine coast this evening...transitioning to snow over
for areas just inland in some cases. Given snow in the mountains
and foothills and a rain/snow mix just south...significant
river flooding is not expected. May have some short-fused issues
at the coast especially with water levels rising towards the 1
AM Friday high tide which may prevent efficient drainage. This
event may also prime some locations for water problems with
another opportunity for heavy rainfall Monday.


Astronomical tides are near peak for the month and already near
flood stage without wind and wave forcing. With a strong coastal
storm continuing through this evening and winds increasing,
expect areas of minor flooding and additional splashover and
beach erosion. Storm surge values should max out around 2
ft...but crucially the timing will miss high tide by several
hours. Coastal flood advisory remains in effect for the next tide


The last GYX upper air observation was March 25 at 12Z.
Unfortunately, a disruption in gas supply has temporarily halted
observations from GYX. At this time it is unknown when
observations will resume.

The Sugarloaf NWR transmitter has returned to service.


ME...Winter Storm Warning until 8 AM EDT Friday for MEZ012>014-
     Winter Storm Warning until 2 PM EDT Friday for MEZ007>009.
     Coastal Flood Advisory until 3 AM EDT Friday for MEZ023>028.
     Winter Weather Advisory until 8 AM EDT Friday for MEZ024.
NH...Wind Advisory until midnight EDT tonight for NHZ007-008-
     Winter Storm Warning until 2 PM EDT Friday for NHZ001-002.
     Coastal Flood Advisory until 3 AM EDT Friday for NHZ014.
MARINE...Gale Warning until 11 AM EDT Friday for ANZ150>154.




NWS GYX Office Area Forecast Discussion

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