Area forecast discussion
National Weather Service Gray ME
1053 am EDT Tuesday may 21 2013
Synopsis...
a front will remain stalled to our south through tonight before
returning north as a warm front on Wednesday. Thursday a cold front
will move through touching off thunderstorms. A high will build in
Friday afternoon and remain through the weekend.
&&
Near term /until 6 PM this evening/...
1045 am update...surface warm front is currently draped in a northwest-southeast
fashion from near Boston Massachusetts to southwestern New Hampshire to near Burlington Vermont.
Along and south of this front...temperatures have risen well into
the 70s. North of the front...temperatures are generally in the 50s. A
few convective showers and isolated thunderstorms have developed in
the vicinity of the front over the last hour. Well north of the warm
front across central and middle coast Maine...a general rain
continues to fall but should taper off a little bit going forward.
As the airmass heats up along and south of the warm front which
should waver around across southern and western New Hampshire through early
to middle afternoon...surface-based instability will continue to
increase. MLCAPE values may rise to 700-1000 j/kg in this area
from near Concord New Hampshire westward. With sufficient deep layer wind
shear in place in this area...one or two strong storms may
develop during the early afternoon hours. Will have to watch for
the potential for gusty winds and small hail there. Otherwise...to
the north of the front...a few elevated storms will be
possible...but mainly expecting cool weather along with some
showers.
By middle afternoon...a backdoor push of cooler air will move rapidly
from NE to SW...and push the warm front back southward by late in
the day.
635 am...minor adjustments for this estf update to reflect radar
trend as well as the mesonet.
Previous disc...
at 06z...west-east oriented surface front extended from near Lake
Ontario through southern New England. An impulse evident on GOES
water vapor over the eastern Great Lakes was racing east
accompanied by a broken area of convection as depicted on National Weather Service 88d
Doppler mosaic. This activity will race eastward and reach the
forecast area towards 12z. Impulse and associated convection will
exit the area during the afternoon with lingering clouds and
spotty showers and drizzle in onshore flow to the north of the
stalled boundary. Temperatures mainly in the 50s today with a few
low 60s possible well inland away from the coast.
&&
Short term /6 PM this evening through Wednesday night/...
the next batch of showers arrive tonight as another impulse and
associated surface low begin to gradually push the surface
boundary northward as a warm front. On Wednesday...the boundary
continues northward with southern and western sections enjoying
summertime warmth and humidity in the warm sector with highs
approaching 80f. For northern and eastern sections as well as near
the coast...more clouds or marine influence will limit high
temperatures mainly to the 60s. Steadier showers and isolated
thunder with the warm front will be replaced by scattered
afternoon showers and thunderstorms in the warm sector.
&&
Long term /Thursday through Monday/...
by 00z Thursday a more progressive upper flow pattern develops as
the closed upper low that had been over the central part of the
country for the first portion of the week is reabsorbed into the
hemispheric flow as a trough over the Great Lakes. This trough
will then translate eastwards through the day on Friday...
dragging a cold front through late Thursday as the surface low
tracks up the St. Lawrence River valley.
With the front arriving into western New Hampshire in the afternoon
thunderstorms are likely as middle-day heating combined with height
falls aloft help to destabilize the atmosphere. The biggest
impediment to convective initiation appears to be the potential
for wide spread cloud cover through the morning Thursday as
moisture moves in in the early morning and showers should be
ongoing throughout the day, however strong forcing along the
front and a good wind shift and surface convergence should result
in some thunder for the afternoon.
Friday the long wave trough pushes out to sea.... GFS suggest a
quick moving short wave could cause lingering showers into the
first portion of Friday...however have low confidence in such a
transient feature and have opted to go with clearing earlier in
the day. All guidance agrees on the low being replaced by a high
building in allowing clear skies and warm temperatures by Friday
evening for the start of the Holiday weekend. The high will remain
through Saturday and into Sunday when another boundary stalling to
our south bring the potential for shower through the southern
portions of the area for Monday.
&&
Aviation /15z Tuesday through Saturday/...
short term /through Wednesday/...MVFR with areas of IFR in fog and
drizzle through tonight. Becoming VFR Wednesday with scattered MVFR in
showers and local brief IFR in thunderstorms.
Long term...
Wednesday night will see IFR fog and showers in the mountains...
with MVFR and possible periods of IFR on the coastal plain.
Afternoon thunderstorms may impact... especially in New Hampshire.
Conditions will return to VFR for the weekend.
&&
Marine...
short term /through Wednesday/...quiet on the waters with only
issue visibility restrictions in fog and precipitation.
Long term...
seas will build under southwesterly flow Wednesday night and into
Thursday.. with Small Craft Advisory for high seas most likely by midday on
Thursday. After the winds shift northwesterly seas will diminish
with relatively calm and flat conditions for the weekend.
&&
Fire weather...
with damp weather expected for much of the week along with higher
relative humidity values and green up...fire weather danger should
remain low through the week.
&&
Gyx watches/warnings/advisories...
ME...none.
New Hampshire...none.
Marine...none.
&&
$$
Near term update...ekster
