Area Forecast Discussion
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FXUS61 KGYX 221311
Area Forecast Discussion
National Weather Service Gray ME
911 AM EDT FRI JUL 22 2016
Warm and humid air streams in today as a cold front approaches
from the northwest. This will set off scattered thunderstorm this
afternoon and evening. The cold front stalls over the region on
Saturday before moving south Saturday night. High pressure will
build in from the west Sunday. High pressure will shift offshore
Sunday night. A cold front will approach from the west on Monday
and will push east through the region Monday night. High pressure
will build in from the west Tuesday. A weak cold front will slowly
settle south through the region Wednesday through Thursday.
.NEAR TERM /ThROUGH THIS EVENING/...
Although there is still the possibility for severe convection
today... it is looking more and more likely that it will be an
evening event for most of the forecast area. Water vapor imagery
is clearly showing significant mid level drying upstream of the
forecast area moving into northern New England. The feature that
is likely to kick off our convection today is still just to the
north of Lake Superior. As always though... there are a few things
that could change that. As it stand right now... both the HRRR and
the latest NAM are indicating that convection in our CWA will hold
off until after 6pm tonight. However... once it does start there
appears to be plenty of energy to work with as the short range
models are consistent in showing more than 2000j/kg of Cape. The
short range models are also showing enough instability to get
things started a bit earlier right along the New Hampshire and
Massachussetts border. If that were to materialize then we could
see some convection fire in our area along an outflow boundary. As
it stands though...we are expecting the convection to largely be
confined to 6pm or later across most of the forecast area. The
mountains may be the exception and could go a few hours earlier as
they will be the first to be impacted by the disturbance coming
from the Great Lakes. Midnight shift had already started this
trend in the forecast package so there are not a ton of changes to
the current package.
As the cloud cover begins to greak up today we will also see
significant temperature rises. This will be coupled with an
increase in low level moisture to create very warm heat indices
across most of the area. Expect to see heat indices in the lower
to mid 90s across the coastal plain and southern New Hampshire.
Lastly... with the warm and sunny conditions there could be an
increase in activity at coastal beaches today. Long period onshore
swell will likely generate a moderate risk for rip currents.
Initially looking at two 500 mb waves moving through, one early
today, and the other, a little stronger, tonight. This had sort
of split the energy for potential severe wx today, and will give
us a period with limited trigger for storms through a good part of
the day. First round of t-storms has developed over upstate NY and
southern Quebec. The southern end of the line is expected to
diminish as move into VT, but the northern part may cross the nrn
tier of zones between 09Z and 13Z. Not expecting these to be
severe. Behind this line of storms will see a little subsidence
and some drying, and this will likely limit storm development
through at least 18-19Z. The early storms may leave a boundary
across the north, which could produce a few storms before then,
but best chc for storms will be later in the afternoon into the
Otherwise it will be warm with increasing humidity this afternoon,
as temps rise into the mid 80s to around 90 in many spots and into
low 90s southern NH. Urban parts of southern NH will see heat
index values rising into the mid 90s this afternoon, as TDs climb
into the upper 60s. SW flow will keep the mid coast a little
cooler, and more clouds clouds over the ME mountains will keep
temps there a little lower as well.
As for the storms, best mode for severe will be bowing segments
with damaging winds, but cannot rule out a enough of a rotating
updraft to produce some large hail. Could see a more organized
line develop late, but confidence is low, and looks to be more of
a scattered severe event.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Beyond the threat of severe continuing into this evening, should
see sfc front slow and stall late tonight, as the wave aloft
passes it by. This will allow for a decrease in coverage of
convection late this evening and overnight, but given the presence
of the sfc boundary and plenty of low level moisture, the chance
for a few showers or storms will be there thru the overnight,
especially from central NH thru the ME mid-coast and pointsnorth.
Overnight lows will be balmy, mostly in the low to mid 60s in the
north and upper 60s to near 70 in the south.
On Saturday, a third 500 mb wave will move across New England and
this will push the front southward in the afternoon. Another round
of showers and storms is expected, and once again we will see the
threat for severe storms as height falls and mid-level lapse rates
combine with decent sfc instability to produce some rotatingupdrafts.
The best chance for the strong storms would be south of the front
and this may preclude much of a severe threat in the northeastern
zones. Winds shift more westerly which will allow for slight lower
TDs and slightly less warm highs on Saturday.
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
High pressure will build in from the west Saturday night bringing
clearing skies overnight. Lows will bottom out in the upper 50s to
lower 60s north and mid to upper 60s south.
High pressure will crest over the region on Sunday producing mostly
sunny skies and highs from the mid 70s to lower 80s north and mid
to upper 80s south.
High pressure will shift offshore Sunday night and Monday as a cold
front approaches from the west. Timing of this boundary not looking
favorable for convection on Monday as best instability remains west
of the forecast area. Best chance for any thunderstorm activity
would come late in the day in far northwest zones. Should see a very
warm and humid day with highs ranging from the mid 80s to lower 90s.
Cold front will cross the region Tuesday night with scattered showers
and thunderstorms. Lows will range through the 60s to near 70.
High pressure will build in from the west behind the front on Tuesday
bringing somewhat cooler and less humid air back into the region on
brisk west winds. Highs on Tuesday will range from the mid 70s to
High pressure will hold over the region Tuesday night and Wednesday
as a weak cold front slowly settles into southern Quebec. May see
a late day shower or thunderstorm in far northern zones but not
looking for any widespread activity. Highs on Wednesday will top
out in the mid 70s to lower 80s north and mid to upper 80s south.
Cold front will slowly sag south through the region Wednesday night
and Thursday which may set off some afternoon convection but not
looking for anything too widespread as forcing with this boundary
.AVIATION /13Z FRIDAY THROUGH TUESDAY/...
Short Term...Mainly VFR through today, except for some sct TSRA
mid-late afternoon. Could see a period of IFR coastal stratus and
fog late tonight, and perhaps some valley fog as well.
Long Term...VFR Saturday night through Tuesday.
Short Term...Persistent SW flow allows for swell to build today
and tonight in the open waters reaching 5-6 feet or so through
Long Term...No problems noted.
MARINE...Small Craft Advisory for hazardous seas until 8 AM EDT
Saturday for ANZ150-152-154.