Area Forecast Discussion
Issued by NWS Caribou, ME

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FXUS61 KCAR 110113
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
913 PM EDT Thu Aug 10 2017

.SYNOPSIS...
A warm front will lift north across the region on Friday. Then a
cold front cross the state on Sunday.

&&

.NEAR TERM /THROUGH FRIDAY/...
9:13 PM Update...The cold front that was across far northern
Maine late last evening has stalled out across the Downeast
Region this evening. The showers and isolated thunderstorms that
moved from the central highlands and across parts of interior
Downeast Maine this afternoon have for the most part died down.
There is still one heavy shower around Waterville, but it likely
will dissipate before it would move into southern Penobscot or
Hancock Counties. Made some tweaks to the forecast based on the
latest observations, radar loops, and satellite data.

Previous discussion...
The frontal boundary remains draped across interior
Downeast/Central Highlands this afternoon, and as expected we`re
seeing scattered convection along it. These showers and
isolated thunderstorms will dissipate as we go into the evening
hours and daytime heating is lost. Patchy fog will develop
Downeast overnight; otherwise expect partly cloudy skies to
prevail. Lows will be in the mid and upper 50s in most spots,
with a few locations staying in the lower 60s.

For Friday...the frontal boundary will finally lift back north as a
warm front. Showers and thunderstorms will develop during the
afternoon hours, mainly along and north of a Dover-Foxcroft to
Danforth line. There`s some uncertainty as to the extent and
strength of the convection. The NAM`s pretty robust with CAPE,
running 1000-1500 J/kg, while the GFS is more tempered, keeping most
locations under 600 J/kg. The NAM is likely overdone as it does have
a high-moisture bias. There will be a bit of shear, around 25 kt in
the 0-6km layer. Freezing levels are progged to be around 10 kft, so
any stronger storms could produce some small hail. Note that SPC`s
Day 2 Outlook just has us in General Thunder for Friday. Given the
uncertainty as to how much instability we`ll have, have opted to
leave any enhanced wording out of the forecast for now. Daytime
highs will be in the upper 70s to around 80, a bit cooler along the
coast.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As a weakening trough/warm front lifts north of the CWA Fri
night, a few lingering showers and perhaps a rumble of thunder
will be possible early from the Central Highlands to the
northern and western borders of the CWA. However, the bulk of
this activity should be over by midnight. As an upper trough and
associated surface low approaches from the west, some models are
pointing toward a risk for PM showers and a stray t-storm along
the western border, so this was reflected with some Chance POPs
and a slight chance of thunder for zones 1, 3, and 4 in the
afternoon and evening. Knocked out any thunder risk after 00z
Sun, and dropped off general shower activity between midnight
and sunrise as the forcing of the low/front remains to the west
overnight. Also overnight into Sun AM, a disturbance passing
south of the CWA may bring some showers to Downeast and the
Penobscot Bay, but given discrepancies and lack of consistency
on the details, have kept POPs to 40 or less for now.

As for the passage of the front on Sunday, there remains some
disagreement on timing between the models, with the GFS still
teh fastest and the CMC still the slowest. However, overall
timing has shifted towards more agreement with the faster GFS
timing, so winds and POPs for Sunday were skewed toward this
sort of a solution. Introduce slight chance of thunder late Sun
AM, with an increased risk for storms in the afternoon and
evening. Overall, high temps were dropped a few degrees both
days given the most recent guidance, but highs for central and
Downeast areas will be warmer on Sunday owing to SW`ly winds,
compared to onshore winds for Saturday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
There is good agreement on some weak upper ridging bringing
clearing to the CWA later Sun night through Mon night. However,
an upper trough forecast to pass to the north on Tue may bring
some showers and a slight chance of storms to the CWA, mainly
across central and northern areas. Models then diverge from
Wednesday onward, with the GFS keeping the CWA dry through
Friday, but the CMC and ECMWF dropping a cut-off low out of
Hudson bay and across the area later Wed or Wed night. There`s a
further breakdown in any consensus on Thurs, as the ECMWF is
much quicker to eject this low and brings dry conditions for
Thurs, while the CMC is slower and keeps some clouds and showers
around through Thurs. As a result, POPs were kept to 40 or less
for Wed and Wed night, and to 30 or less for Thu afternoon and
evening. Highs were kept around seasonal norms through the
long-term. These highs were lower than the GFS and GFS MOS
guidance for Wed and Thu to account for the risk of an upper-low
bringing some precip and clouds to the CWA.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: Mainly VFR expected at the northern terminals
through 15z Friday. The southern sites may drop to IFR or
perhaps LIFR at times after midnight in patchy fog, but
confidence on the fog is on the low side. Scattered showers and
thunderstorms will develop after 15z Friday and continue
through 00z Sat, especially at the northern sites. MVFR or IFR
is possible in any thunderstorms.

SHORT TERM: Convective showers may impact KHUL through KFVE 00z
to 09z Sat, with MVFR or IFR conditions possible in such
activity. Otherwise, onshore flow and a disturbance passing to
the south of the state may bring IFR CIGs to KBGR and KBHB
for Sat and Sat night, but this is not very certain at this
point. Some MVFR and even IFR conditions are more certain during
the day Sunday with shower and thunderstorm activity mainly for
KBGR northward, though lower conditions for KBHB can`t be ruled
out on Sun. Expect VFR conditions for all sites Sun night
through Mon, except where patchy fog may cause lower conditions
Sun night. Another disturbance may bring lower CIGs with shower
activity, but widespread MVFR or IFR conditions are not expected
at this time.

&&

.MARINE...
NEAR TERM: No headlines will be needed through Friday. The waters will
mainly be under the influence of high pressure with a frontal
boundary remaining to the north. As such, winds and waves will
remain below Small Craft levels through the period.

SHORT TERM: Winds and seas should remain well below SCA criteria
through the period, and no significant threats to safe
navigation are expected over the weekend.

&&

.EQUIPMENT...
The Hodgdon, Maine WSR-88D is back in service after technicians
installed an important technological upgrade this week.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.

&&

$$

Near Term...CB/Hastings
Short Term...Kredensor
Long Term...Kredensor
Aviation...CB/Hastings/Kredensor
Marine...CB/Hastings/Kredensor
Equipment...CB



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