Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 201048

Area Forecast Discussion
National Weather Service Gray ME
648 AM EDT Mon May 20 2024

Surface high pressure moves in today and will clear things out
this afternoon and then anchor itself just offshore allowing
for some seasonably warm temperatures. There`s a chance for some
thunderstorms in the mountains late Tuesday into Tuesday night,
with a better chance for showers and storms Wednesday afternoon
and evening as a cold front approaches. An upper level trough
will keep scattered showers over the region Friday. High
pressure builds in from north over the weekend.


645 AM...No real changes to the forecast, just adjusted sky/fog
to better reflect reality this morning. They still should all
burn off by midday.

Previously...Sfc high shifts offshore during today as 500 MB
ridging shifts into more zonal flow by later in the day. This
will allow sfc flow to become more SW as flow aloft shift to the
W. The stratus S and E of the mtns will begin to erode from
inland first this morning, and eventually do so at the coast,
but that may not be until midday or so. Also, the onshore flow
near the coast will likely never shift to SSW, as it does this
afternoon inland. Ultimately this will lead to a fairly wide
differential in temps between the coast and inland areas,
especially the CT valley where highs will reach into the upper
70s today, while inland areas S and E of the mtns should get to
the low to mid 70s, and the coast will likely remain in the 60s


Should stay mainly clear away from the coast through the night ,
and with light winds this will allow temps to fall into the low
to mid 50s across much of the area, although the coast will be
the coolest, as it will never get out of the marine lyr, and
lows will fall to around 50. Another round of low coastal
stratus is possible again late tonight, although should be
limited to closer and the coast, and some models only bring into
the mid-coast overnight.

On Tuesday, we line up pretty good with W flow aloft and SW flow
near the sfc, and this will advect some warm mid level air into
the CWA with 850 MB temps pushing 15C by the afternoon. This
should be enough to push temps to 80-85 across much of the area
away from the coast. Still we are likely to see see the flow
shift to the S along the coast which will limit highs to 65-70
along the mid coast and 70-75 along the N-S oriented coast S of
Casco Bay. There is a remnant MCS that will be across S Quebec
late in the day. 12Z model runs tend to keep this out of the CWA
until Tue evening, but may see some convection develop ahead of
it the far N late in the afternoon.


Overview... A building ridge along the Eastern Seaboard brings
very warm conditions for much of the week, peaking midweek.
Residual convection riding around the ridge brings a few chances
for showers and storms over several days, with the greatest
chance on Thursday as a cold front approaches from the north.
Relatively cooler air returns by late in the week and the


Wednesday looks to be the peak of the heat, with temps warming
into the low 90s across much of southern and western NH, and 80s
elsewhere. Even the southern coastlines warm into the 80s with
southwesterly flow, while the MidCoast warms into the 70s. As
mentioned, there`s a little less certainty across the north on
high temps where leftover morning convection could limit how
high temps rise. Scattered afternoon showers and storms are also
likely across northern areas Wednesday afternoon. There will be
another deteriorating MCS rounding the ridge again Wednesday
night, but similar to the previous night`s it`s unclear at this
point how robust this system will be by the time it reaches New

Thursday remains warm, but with a downward trend in temps
underway. A cold front moves through during the daytime, with
some showers and storms accompanying it, especially across the
higher terrain. Thursday likely ends up be the warmest day for
the MidCoast, with winds turning westerly in the afternoon and
warming temps into the upper 70s to near 80. 80s are expected
elsewhere, with one more day in the upper 80s across southern

Behind the cold front, temps still look fairly warm downwind of
the mountains on Friday. Temps warm into the 70s in most spots,
with highs near 80 across southern NH. The mountains likely see
more cloud cover and get deeper into the cooler airmass,
keeping highs in the 60s.

Right now the weekend looks cooler as high pressure noses in
from the north, but the warmth won`t be far off to the south.
The high is not overly strong, and has been trending a bit
weaker since yesterday. Should this trend continue, then the
weekend would likely end up warmer with highs in the 70s, rather
than the 60s. This forecast follows closer to that trend, but
acknowledges that we could end up with a boundary of airmasses
within the CWA. This is one more item to monitor over the coming


Short Term...We haven`t really seen the LIFR cigs yet at most
terminals and even IFR is more here and there at this hour.
Theres still a possibility of some LIFR around daybreak, but
overall IFR looks to be the rule. Inland terminals should
improve to VFR with a few hours of sunrise, while coastal
terminals and KAUG will not break until around midday. Otherwise
VFR expected into early this evening. Tonight looks better with
any possibility of coastal stratus and/or fog limited to coastal
terminals, and even this may only occur at KRKD, based on some
models. Whatever does form, will be quicker to dissipate Tue

Long Term...Mainly VFR conditions are expected at most
terminals Tuesday night through Thursday. Some coastal fog is
possible at times at RKD Wednesday and Thursday. Afternoon and
evening showers and thunderstorms bring brief restrictions
Tuesday through Thursday across northern terminals, with a
lesser chance of showers and storms elsewhere. VFR conditions
likely return by next weekend.


Short Term...Seas near 5 ft should gradually drop through today,
more in the 1-2 ft range by this evening. Winds are light
through tonight, but will pick up from the SW on Tuesday,
although should stay below SCA levels.

Long Term...High pressure builds along the Eastern Seaboard
this week, bringing increasing south to southwesterly flow.
Areas of dense marine fog are possible by midweek. Some SCA
conditions are possible by Thursday with increasing
southwesterly flow ahead of an approaching cold front. High
pressure then builds across the waters going into the weekend.





LONG TERM...Cempa/Clair