Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 252255

Area Forecast Discussion
National Weather Service Caribou ME
655 PM EDT Tue Jul 25 2017

High pressure will build across the region through Wednesday.
A cold front will cross the region later Thursday through
Thursday night.


630 PM Update: The most sig chg this update was to speed up the
clrg across the Rgn by erly eve with latest sat imagery already
showing mclr to clr skies. Otherwise, fcst hrly temps/dwpts were
updated into the ovrngt based on obsvd hi temps and trends seen
from latest late aftn/erly eve obsvd temps. Based on these
trends, we lowered fcst ovrngt low temps across NW vly lctns a
few deg F based on lower obsvd dwpts then previously fcstd
already in place.

Orgnl Disc: High pressure will build across the region tonight
through Wednesday. Cloud cover will decrease this evening
leaving clear skies overnight. Could also have patchy fog late
tonight across Downeast areas. Mostly sunny skies and warmer
temperatures will occur Wednesday. Low temperatures tonight will
range from the mid to upper 40s north, to around 50 to the
lower 50s Downeast. High temperatures Wednesday will range from
the upper 70s to lower 80s across much of the forecast area,
with mid to upper 70s along the Downeast coast where onshore
winds will develop.


Unsettled for Thursday and cooler for Friday.

A weak occluded front is forecast to lift across the region
early Thursday. Model guidance still shows some discrepancy in
regards to timing of the initial round of showers. The 12z NAM
was by far the slowest w/the timing and less rainfall while the
GFS and Canadian Global support an earlier arrival of the
showers w/more rainfall. There is some mid level forcing w/this
front along w/some moisture through 700mbs. This would be
enough to set off some activity. The 12z run of the ECMWF aligns
closer to the GFS and Canadian w/the timing and rainfall.
Given all this, decided on a faster timing and brought 40-50%
pops to the north and central areas by between 6-8 am. These
showers look like they will move through quickly w/a break in
the action. Another round of activity which will be showers and
possible tstms by the afternoon into evening as a pre-frontal
trof ahead of the cold front moves into the region. Some
instability is does appear to be there and if some heating can
be realized, then the atmosphere would destabilize. The GFS is
more bullish and the NAM w/its instability and steeper lapse
rates. The GFS showed CAPE of 800-1200 joules w/0-6km around 25
kts or so. The NAM is weaker but does show some shear and
meager lapse rates around 6.0 c/km. Moisture does appear to be
available w/PWATS 1+ inches. Temps were raised a category from
the previous forecast w/the expected brief heating. This would
mean 70s to around 80 for central areas. I say brief, because
concern is that cloud cover hanging on would keep substantial
heating to a minimum and thus cutting back tstm potential.
Attm, decided to include the mention for tstms but the
confidence is not high enough to include any enhanced wording
attm. The later shifts can look into this further as we move
closer in.

The associated cold front is expected to slide across the region
later Thursday night w/showers and any leftover storms ending by
late evening. Cooler air is set to follow in behind the front
for Friday w/some sunshine and clouds. Daytime temps for Friday
will most likely be below normal for late July.


High pres at the surface set to settle across the region into
the weekend. Aloft will remain an upper trof across northern New
England. The trof axis will be a focus for the chance for some
showers across the northern and western areas especially on
Sunday. This along with some clouds would limit heating and
hence cut down on daytime temps. Decided to stay temps just
below norms for Saturday and near normal readings for Sunday.

The next shot for any shower activity looks to be on Monday as a
cold front is shown by the long range guidance to slide across
the region in the afternoon. Given the setup, it looks like the
potential for convection is there.


NEAR TERM: Variable conditions are possible with any patchy fog
Downeast late tonight. Otherwise, VFR conditions are expected
across the region tonight through Wednesday.

SHORT TERM: MVFR conditions w/some IFR on Thursday. The IFR will
be mainly across KBGR and KBHB due to s flow in off the Gulf of
Maine. Showers will be the main wx element w/the threat for some
tstms for the northern terminals. Improving conditions for
northern areas later Thursday night into Friday to VFR while
from KBGR to KBHB will see hang onto IFR/MVFR. Conditions are
expected to improve for all terminals by later Friday into


NEAR TERM: Winds/seas will remain below small craft advisory
levels tonight through Wednesday.

SHORT TERM: No headlines are anticipated for this cycle. Stayed
w/winds 10-15 kts into Friday w/a few gusts closing in around 20
kts for the outer waters. The cold front should clear the region
later Friday into Saturday w/high pres settling in from the wnw.
Thus, winds will drop back off to around 10 kt in Sunday. Seas
will creep up to around 4 ft along the outer zones into Friday.
Seas will drop back as the front cross the waters and winds turn
more offshore.





Near Term...VJN
Short Term...Hewitt
Long Term...Hewitt
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