Area Forecast Discussion
Issued by NWS Portland, ME
FXUS61 KGYX 270132
Area Forecast Discussion
National Weather Service Gray ME
932 PM EDT THU MAY 26 2016
High pressure to our east will allow a southerly wind to bring
warm and humid conditions into New England. Some afternoon
thunderstorms will be possible on Friday afternoon as the heat and
humidity generate instability in the atmosphere. The hottest day
will be Saturday when much of the area will warm into the 80s and
90s. A cold front will drop southward across the region late
Saturday into Saturday night. An onshore easterly flow will keep
temperatures cooler on Sunday especially east of the mountains.
Warm air builds in again from the southwest on Monday and Tuesday
before another cold front crosses the area from the northwest
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
930 pm update: Quiet conditions over the area at this time. The
few convective cells over southern NH earlier this evening have
dissipated. Mid/high clouds continue to stream across the area.
Input latest obs data and made minor adjustments to temps and
cloud cover accordingly...no other changes.
625 pm update: A few convective cells have developed over
southern NH so added pops in the area of the cells. Minor tweaks
to temps based on latest mesonet data. No other changes at this
Mainly clear skies will be replaced by clouds that will continue
to spill east ahead of an approaching warm front. This front will
become hung up across far Western Interior Maine and
southern/central New Hampshire. Scattered showers and
thunderstorms will gradually move eastward through New Hampshire
tonight. Expect these storms to move east into more stable
conditions across Maine, where elevated convection is a
possibility over night.
Dew points will remain in the lower to mid 50s overnight, with
readings climbing to near 60 over southern New Hampshire. This
will be close to the forecast overnight mins.
Patchy fog may occur in the CT River Valley.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
With warm air advection and the front in the vicinity on Friday,
expect showers and thunderstorms to develop once again, mainly in
the afternoon hours. Sufficient CAPE with ~1000 J/KG forecast,
mainly over New Hampshire. There will be a significant west to
east gradient in max temperatures and therefore instability. At
this time, have limited enhanced wording for the possibility of
damaging winds and hail to New Hampshire. Have included this
possibility in the HWO as well. Greatest threat would be for high
Dew point values will climb into the lower to mid 60s over
southern New Hampshire during the day. With air temperatures
forecast in the mid 80s, expect heat indices to further be on the
There is a possibility of patchy drizzle and fog along the coast
due to onshore winds developing once again. This may linger into
Friday night as convection gradually weakens with the loss of
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Weak low pressure moving through the Gulf of Saint Lawrence will
cause winds to shift to the northwest on Saturday. This will help
to keep the influence from the seabreeze minimized to the
immediate coastal areas in the afternoon. Meanwhile the heat
continues to build with high temperatures reaching the mid 80s to
low 90s. With dewpoints remaining in the 60s, it will also be
humid. Heat index values will likely approach 95 degrees in urban
New Hampshire. Cannot rule out an afternoon thunderstorm either
though this should be fairly isolated.
Saturday night another front drops southward across the area...
helping to push out the warm/humid air mass. By Sunday morning
high pressure will be centered over eastern Maine with an easterly
wind flow across much of the area. This onshore flow will keep
temperatures cooler on Sunday, especially east of the mountains.
Went just a few degrees below the blend of guidance values to
account for the wind off the cold waters.
Meanwhile, the heat and humidity continue to build further to the
west over New York state. By Monday this heat and humidity will
shift eastward as high pressure moves east and a shortwave trough
drives a cold front toward the area from the northwest. This will
bring a chance for some thunderstorms on Monday. If all the
ingredients come together just right then there could be a chance
of severe thunderstorms. Right now the biggest question is whether
the instability will be able to spread into our area or whether
the southerly low level flow will keep enough of a marine
influence in place to limit instability especially across Maine.
A cold front crosses the area Monday night into Tuesday. The air
mass behind the front is not that much cooler than the one ahead
of it so temperatures remain in the 70s to low 80s for highs. A
better shot of cooler air arrives Wednesday into Thursday.
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Short Term...Areas of MVFR developing tonight in showers and
thunderstorms with local IFR near the coast in drizzle and fog.
Showers and thunderstorms will be possible again on Friday.
Long Term...Generally expect VFR conditions Saturday. Cannot rule
out an isolated thunderstorm Saturday afternoon. An onshore flow
develops by Sunday morning and it is possible that low clouds
could move in off the water bringing IFR conditions east of the
mountains. Showers and storms are possible again on Monday in
advance of the next cold front coming in from the northwest.
Short Term...Quiet on the waters with winds and seas remaining
below Small Craft thresholds.
Long Term...A cold front drops south into the Gulf of Maine and
pushes westward Saturday night. Winds become easterly which could
increase the wave heights in the western Gulf of Maine, but still
expect winds and waves below advisory levels. High pressure shifts
east with a southwest flow returning by Monday with gusts possibly
approaching advisory levels as the front approaches Monday night
Moderate to high humidity levels return for tonight through the
start of the holiday weekend. We are forecasting all areas to
receive rainfall for the end of the week into the upcoming
weekend...although amounts should be relatively light.