Area Forecast Discussion
Issued by NWS Portland, ME-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KGYX 300850
Area Forecast Discussion
National Weather Service Gray ME
450 AM EDT MON MAY 30 2016
A front stalled to our south will return north as a warm front
today. This front will be preceded by showers and a few
thunderstorms through Monday morning. A warm humid air mass will
follow the warm front on Monday afternoon with another round of
showers and thunderstorms expected. Tropical moisture from the
remnants of Bonnie will be entrained in the frontal system and
could produce heavy rainfall and localized drainage flooding on
Memorial day. Two cold fronts will cross the area Monday and
Tuesday night with high pressure to follow Wednesday and
Thursday. An upper level trough could produce some rain towards
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
5am ... just a quick adjustment to the PoP as radar shows rain
moving into New Hampshire a bit faster.
At 3am... an area of rain was crossing Vermont and
Southern New England into southwest New Hampshire. This rain will
continue to move northeastwards crossing the southern portion of
the forecast area early this morning. The rain is being driven by
two factors. To the south, the remnantsof Tropical Depression
Bonnie is streaming moist tropical air northward on the west side
of a Bermuda high. Satellite shows PWAT values as high as 2in in
this air mass with values around 1.5 inches across much of New
England. To the west a short wave trough is moving out of the
Great Lakes into western New York. These two systems are creating
a squeeze pushing the moisture northwards up the coast. While PWAT
is high... the area of rain is now mainly stratiform forced by the
synoptic squish and thus the concern of heavy rainfall has abated
as the rain continues to move. THe early morning timing will also
keep any convective threat to a minimum.
Today will be a bit of a paradox as rain creates sun which in turn
creates rain again. Ahead of the early morning rain the marine
layer is well entrenched along the coast with widespread drizzle
and fog. The morning rain will serve to move the marine layer out
allowing sun to break out from west to east across the region this
afternoon. The sun will subsequently destabilize the
region...allowing a line of thunderstorms to form along the front
which will cross the area late today. The thunderstorms will form
around mid afternoon as temperatures rise to near 80 in interior
New Hampshire and the CT river valley. CAPE values of up to 1000
J/kg combined with an 80kt jet streak overhead will generate
sufficient shear for a few severe thunderstorms to develop with
damaging winds and small hail being the main threats.
.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
Overnight skies will clear and showers and thunderstorms will die
off as the front moves out of the area. Residual moisture will
allow patchy fog to form...especially in favored valley locations.
Tuesday will be mostly sunny with just a slight chance of upslope
showers in the afternoon in the mountains along the Canadian
border. Light northwesterly flow in the wake of the front will be
enough to keep the sea breeze at bay allowing temperatures to
climb into the 80s for all but the immediate coastline.
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Dry weather will continue into the midweek as high pressure
gradually builds in behind the departing front. Weak northerly
flow will veer to the east by Wednesday afternoon bringing in a
sea breeze. Temperatures should reach the 70s however with inland
areas a few degrees warmer than the coast.
Onshore flow strengthens Thursday with perhaps some drizzle...
stratus... and fog allowing readings to only reach the 60s for
much of the area. The remnants of the very weak TD Bonnie will
move off the Carolinas Thursday night allowing a baroclinic zone
to shift towards the eastern seaboard. This will introduce some
heavier showers for Friday into the weekend with highs once again
in the 60s and 70s. During this time overnight lows will be in the
40s and 50s...or in a word...normal.
.AVIATION /09Z MONDAY THROUGH FRIDAY/...
Short Term...widespread LIFR conditions will continue for the next
several hours. Rain moving in from the Southwest will increase
visibilities at MHT CON and PSM by 14Z and at Portland by around
16Z. Conditions will improve to VFR across the area by 18Z. This
afternoon scattered thunderstorms and showers may impact HIE LEB
and AUG. Monday night expect valley fog for LEB and to a lesser
extent HIE CON. All areas will be VFR for Tuesday.
Long Term...VFR for Wednesday. Some MVFR along the coast Thursday
in drizzle...stratus...and fog. -SHRA Thursday evening into Friday
for all terminals bringing ceilings and visibilities down to MVFR
Short Term... Rain and fog for this morning. Fog may lift somewhat
mid afternoon before returning overnight. Winds and seas will
remain below small craft.
Long Term...Generally poor boating conditions from Thursday
through the weekend in fog and drizzle as well as showers. Winds
and seas will remain below small craft criteria.
Winds will remain light through the next few days with cooler
temperatures and precipitation in the forecast the next two days.
This will help keep fire danger in check.