Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 291054
AFDGYX

Area Forecast Discussion
National Weather Service Gray ME
654 AM EDT Thu Jun 29 2017

.SYNOPSIS...
A warm front will approach today and tonight bringing
increasing chances of rain during the afternoon hours and
especially overnight. Warm and moist weather Friday through the
weekend and low pressure nearby will allow for continued chances
for showers and thunderstorms. Drier weather will arrive early
next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
655 AM Update...Have updated the forecast mainly for minor
adjustments to PoP and temperatures for the next few hours.
Plenty of sun across central and eastern zones this morning, and
have adjusted sky cover down a bit for these locations for the
next few hours. Otherwise, looks like any rain/showers hold off
for at least a couple more hours across western zones. When it
does rain, it should be light. The threat for heavy downpours
does not look to arrive until tonight (except perhaps on an
isolated basis this afternoon across central and northern
zones).

Previously...

A warm front will gradually sharpen up to our southwest today.
An early morning short wave trough grazing our northern zones
may bring a brief period of showers with isolated thunder to
Somerset County prior to dawn. This short wave trough, as it
departs, will provide some upper level confluence will may allow
shower activity associated with developing warm front to delay
for most zones today. We do have increasing PoPs today, mainly
across western zones, but we think any precipitation will be
quite light during the daylight hours. In fact, there may be a
decent amount of sun this morning. Went with a blend of models
for high temperatures today which resulted in highs well in the
70s. If a narrow band of light stratiform rain does develop
today in association with the warm front, then temps will lower
in that area.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Warm front lifts northward tonight. This will allow moisture and
elevated instability to flood northward above our CWA overnight.
As a short wave trough approaches from the west and low level
jet strengthens, showers and thunderstorms should develop,
especially across northern zones. The area of showers and storms
may take the form of a loosely organized MCS with the threat for
heavy rainfall and frequent lightning. Again, the main threat
would be across northern zones, but all areas will be in play
for some lightning and heavy downpours overnight.

The area will be warm sectored on Friday with very warm and
humid weather expected. Forcing for ascent should be pretty weak
for much of the day (after morning convection exits) and this
should allow for mainly dry weather save for a few pop up
thunderstorms in the afternoon. However, with moist and unstable
airmass in place, a better defined short wave moving through the
flow could allow for a more widespread afternoon convective
event. As of right now, that potential threat looks to be to our
west.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
The extended forecast will start off with a fairly wet start as
a series of showers and thunderstorms form over the region
before drying out for the start of next week.

Friday night will begin with an upper level trough upstream of
us over the great lakes. At the surface a weak surface low
remains over the eastern Great Lakes with the warm front
extended east west across Maine. In addition to this boundary,
deep southerly flow around a strong Bermuda high will push moist
tropical air northward. The juxtaposition of a surface boundary
and deep tropical moisture doesn`t bode well for those seeking
dry conditions for the weekend. Saturday will see widespread
shower activity likely and with PWAT nearing seasonal and yearly
highs very intense rainfall is possible in any storms that
form. Upper level flow remains relatively weak through the end
of the day Saturday when an upper level jet streak finally
rounds the trough axis. This weak flow means storms will be slow
to move presenting a flood risk especially in the flashier
mountain areas. The location of any boundaries as well as
rainfall received in the prior 48 hours will be key in
determining any flash flood risk for Saturday and due to these
uncertainties will not be issuing any Flood watches at this
time. Temperatures will be quite warm on Saturday with again the
location of any existing warm frontal boundary playing a key
role. south of the boundary through southern NH and into
extreme SW Maine skies will clear enough to allow temperatures
to climb into the 90s and with the moist airmass this will
result in a heat index in the low 90s. Have hedged upwards a bit
on the temps in the south as models are often slow to capture
this warm air.

As we move into Sunday a jet streak rounds the bottom of the
upper trough pushing the surface system and accompanying cold
front to our east Sunday morning. While some shower and
potential thunderstorm activity is likely along the cold front
the trend has been for an earlier timing and drier air mass
which will decrease PoPs for the afternoon.

High pressure finally begins to build into the area on Monday.
The mountains will be the only areas to see any sort of shower
potential as they remain in upslope northwesterly flow in the
wake of the front the day before.

Tuesday the 4th of July will also be dominated by high pressure
and mostly sunny skies across the forecast area. Highs will be
near 80 south to the 70s north. With high pressure expect a
seabreeze to develop along the coast. Clear skies, warm
temperatures, and light winds sounds like the making for a
perfect holiday but throw in the mid-50 degree water
temperatures of the ocean and the hypothermia risk to paddle
craft remains high.

The high pressure will remain into the middle of next week with
mostly sunny skies and temps in the 70s through Thursday.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
Short Term /through Thursday Night/...Areas of MVFR late this
afternoon and tonight in shra/tsra with lcl IFR psbl. This
morning will be VFR outside of early morning valley fog. Mainly
VFR on friday outside of scattered showers and thunderstorms.

Long Term...
Saturday will see showers and thunderstorms particularly in the
north...here the clouds may drop to MVFR for the afternoon as
showers become more widespread. With the abundance of moisture
IFR fog is likely across the area both Friday night and Saturday
night before a drying trend moves in. By Sunday high pressure
comes in for the start of next week bringing VFR conditions and
a sea breeze to the coastal terminals.

&&

.MARINE...
Short Term /through Friday/...Marginal SCA conditions may
develop on the ocean waters tonight into Friday with southerly
flow strengthening. However, with the increasingly warm air
moving over the colder ocean it may be tough for winds to mix
down and generate seas as high as the wave models are showing.

Long Term...
Conditions remain marginal for a small craft with higher waves
through the day on Saturday on the outer waters before
decreasing as high pressure moves in on Sunday.

&&

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

&&

$$

NEAR TERM...Ekster
SHORT TERM...Ekster
LONG TERM...Curtis



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