Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 031639
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
1239 PM EDT Wed Jun 3 2020

.SYNOPSIS...
There will be some scattered showers today, especially in the
afternoon, as low pressure tracks across northern New England.
We will see the temperature warm up behind it for Thursday and
Friday with showers returning Friday. A cold front Saturday
morning may be accompanied by another round of showers and
thunderstorms, but it will usher in cooler and drier air through
early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1237 Am Update...Continue to monitor showers crossing eastern
New York, Vermont and into far western New Hampshire early this
afternoon using adjacent radars as the GYX radar remains down.
Scattered, mostly light precipitation expected across western
Maine and New Hampshire for the remainder of this afternoon and
this evening per latest mesocale models. However, the
atmosphere may become sufficiently unstable over southern areas
to product a few thunderstorms through this evening.

Minor adjustments made to near term temperatures, dew points and
winds as well.

615AM UPDATE...
Made some adjustments to early morning precipitation chances
based on the latest observations which show not much rain
remaining. However, a few isolated showers are still possible
before the bulk of the shower activity arrives around midday.

ORIGINAL DISCUSSION...
Expect another round of showers today as low pressure tracks
along a subtle warm front draped across our area. These should
begin in the early afternoon, and there may be enough
instability for a rumble of thunder or two in southern New
Hampshire. Don`t expect a whole lot of areal coverage for
showers or total rainfall from this. With mostly cloudy skies,
temperatures will be held into the 60s for most, but southern
New Hampshire south of the warm front will warm into the 70s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Any lingering showers exit very quickly this evening with a
warmer westerly flow developing. The warmth will be noticeable
on Thursday as temperatures reach the 70s and 80s across the
region., Coastal areas may be a bit cooler as winds become more
southwesterly.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
The long term portion of the forecast is characterized by zonal
flow and anomalously high heights through the end of the week
yielding to an amplified, trough dominant pattern heading into
next week. Lower down in the atmosphere, the warming trend
continues into Friday, then is moderated by the passage of a
cold front Saturday with a return to near-normal temperatures.
Temperatures begin to trend warmer again by the middle of next
week as the amplified pattern shifts ridging into the eastern
CONUS.

Starting Thursday night and Friday, heights aloft steadily fall
in otherwise zonal flow while below warm and moist advection
increases. Resultant baroclinicity and upglide will likely lead
to some scattered rain shower activity over the region, most
likely over higher terrain. High temperatures in the 80s in a
developing warm sector plus increasing dew points will likely
lead to some instability, so have included a slight chance of
thunder during the afternoon and evening hours. Friday night, a
trough begins to dig down from the Canadian Plains and into the
Great Lakes region with cyclogenesis near the southern ON/QC
border...locally expect a stronger surge of warm/moist advection
which may lead to some fog development over the waters should
higher dew points be realized.

The way things look right now, Saturday has the greatest chances
for impacts with the passing frontal system. Synoptic support
exists for widespread showers with at least some thunder; jet
dynamics and the digging trough provide broad scale lift from
above while steepening lapse rates will provide support in the
mid-levels. As for a low-level triggering mechanism... am
honing in on the passage of a cold front trailing a low pressure
center as it travels east to west along the international
border. The latest round of 00Z models shows the cold front
crossing the Whites by mid-day Saturday. With this in mind, have
gone a little warmer for high temperatures on Saturday and
maintained a broad brush of slight chance thunder for the area.
Given the current model solutions, could argue for higher
thunder chances with the position of the cold front allowing for
the development of diurnal instability... but am not ready to
hinge the forecast on the position of a mesoscale frontal
feature so have maintained slight chance for now. Will have to
monitor the Friday/Saturday time period for severe storm
chances; we will be in the right entrance region of a jet streak
over the maritimes with the classic New England dilemma of
better shear north/better instability south.

Expect a clean change of airmass after the cold front and trough
pass Saturday into Sunday. 850mb temperatures in the mid-teens
Friday night drop into the single digits by Sunday with
strengthening low pressure over the maritimes producing a
northwest breeze locally. Expect high temperatures to run around
10 degrees cooler on Sunday than Saturday, back closer to
normal for this time of year. High pressure builds in to our
west Sunday night through Tuesday and heights aloft begin to
rebound. The coolest nights of the forecast period are expected
Sunday night with a cool airmass overhead and again Monday night
as high pressure nears, possibly allowing for a radiational
cooling night. Will have to monitor these mornings for possible
frost headlines over the mountains.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Short Term...Mostly cloudy conditions today, with ceilings
mostly around 5000 FT. Could see some MVFR ceilings as low
pressure moves through, accompanied by some showers and possibly
a thunderstorm especially for southern New Hampshire. This
should end this evening with VFR returning for all areas.

Long Term...VFR prevails on Thursday and Friday with light rain
showers, perhaps afternoon storms, beginning to enter the
picture Friday. Fog may impact locations along the coast Friday
night into Saturday, then a cold front crosses Saturday with
more restrictions possible in showers and storms. VFR returns
behind the front.

&&

.MARINE...
Short Term...Weak low pressure tracks along a subtle warm front
and into the Gulf of Maine later today. Since the pressure
gradient remains weak, winds will be mainly light and variable,
becoming westerly and then southwesterly with time through
Thursday.

Long Term...Winds and seas remain below SCA thresholds through
Thursday and Friday with southerly to southwesterly flow. Areas
of fog may develop Friday night into Saturday, and seas may near
5 ft thresholds, ahead of a cold front. That front crosses
Saturday with showers and storms possible. Cooler northwest flow
returns after the front.

&&

.EQUIPMENT...
KGYX radar has experienced an unexpected problem and is
inoperable. While technicians continue to work on the problem,
it is possible that the radar could be back in service as early
as later this afternoon, but no later than Thursday.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$
JC/ES



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