Severe Thunderstorm Warning 36, NWS Caribou, ME

Area Forecast Discussion
National Weather Service Caribou ME
147 PM EDT Wed Aug 29 2018

.SYNOPSIS...
Low pressure from Quebec will approach this afternoon and cross the
region tonight. A trailing cold front will cross the region late
tonight and Thursday morning. Cooler and drier air will then move
into the area later Thursday and Friday as Canadian high pressure
builds southward.

&&

.NEAR TERM /THROUGH TONIGHT/...
145 PM Update... No change in the thinking of Severe WX threat.
Decided to stay w/the previous thinking of damaging winds as the
primary threat. Watching the cell in Quebec as it is showing
rotation w/a hook. That appears to riding the gradient of the ridge.
The latest RAP soundings support possilbe rotation w/the storms as
LCLs drop along w/strong directional/speed shear. Meso analysis
showed strong theta E ridge across the north-central and downeast
areas. The 12z NAM and 16z RAP matching close to the initial setup.
Nice dewpoint ridge nosing nne w/dewpoints expected to climb all the
way into northern areas as the stalled boundary lifts n. Expecting
the radar to light up over the next few hrs.

Previous Discussion...
The main concern in the near term continues to be the
convective potential later this afternoon and into this evening.

A wave of low pressure across the Great Lakes region will then track
northeast across southern Quebec, drawing the front back to the
northeast as a warm front by late this afternoon. As it does so,
showers and thunderstorms are expected to develop this afternoon
across northern and western portions of the region. It appears as if
the greatest threat for any stronger storms will be across western
Maine and into the central Maine Highlands, where surface based CAPE
is expected to increase to around 1000J/KG. 0-6km shear also
increases to around 50 kt across this region resulting in the threat
for gusty winds in any stronger storms. Freezing levels start out
high, but some mid level cooling toward evening posses the threat of
small hail in any stronger storms. Decided to mention locally heavy
downpours in any storms as well, with precipitable water values
increasing to over and inch and a half. A cold front is then
expected to move southeast across northern Maine after midnight and
then into central and downeast areas toward daybreak Thursday.
Scattered showers and thunderstorms are expected to continue into
tonight with the passage of the front, although the threat for any
stronger storms should begin to diminish with the loss of daytime
heating early this evening.

Highs across the north are expected to range from the mid 70s
to around 80 degrees. Across central and downeast areas, highs
are expected to generally be in the mid 80s. Heat indices across
central and downeast areas are expected to top out at around 90
degrees which is below heat advisory criteria.

Lows tonight are expected to range from the upper 50s to lower
60s across the north and mid to upper 60s downeast.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
A cold front will cont crossing thru Cntrl and Downeast ptns of
the Rgn Thu morn and erly aftn with sct shwrs and isold tstms
then take shwrs SE of the FA later Thu aftn and eve. Behind the
cold front, sig cooler (at least back to near seasonal norms)
and much drier air from Cntrl Can will move into Rgn for Thu
ngt into Sat.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
Clds will increase ahead of the next weak cold front Sat ngt
with a chc of shwrs and Tstms mainly Sun aftn and eve. Models
are then uncertain with the tmg of any follow-up s/wvs for erly
next week. In any event, none of the models indicate sig
widespread rnfl Mon and Tue, so for now kept PoPs in the slgt
to low chc category until models getting better tmg consensus in
the long range. Temps look to gradually warm Sun into Tue, but
not as warm or humid as it has been the last couple of days.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: 620 AM....
VFR flight conditions are expected at all the terminals this
morning and into this afternoon. Scattered showers and
thunderstorms are expected to develop across portions of
northern and central Maine late this afternoon and continue into
this evening. Will include VCTS at the forecasts terminals
later this afternoon, except for KBHB. However, non TAF sites
such as GNR and MLT may stand the best chances for thunder this
afternoon and into this evening, with local IFR or lower in any
stronger storms, along with turbulent flight conditions.

SHORT TO LONG TERM: Mainly VFR all TAF sites, xcpt briefly MVFR
with any tstm or heavier shwr Thu and Sun aftn/eve.

&&

.MARINE...
NEAR TERM: Winds/seas are expected to remain below SCA levels
through tonight.

SHORT TO LONG TERM: No marine hdlns anticipated. Kept close to
WW3 wv guidance grids with with sig wv pds in the short wind
fetch 4 to 7 sec and long distance swell 8 to 11 sec ranges.

&&

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

&&

Near Term...Hewitt

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Special Weather Statement
National Weather Service Caribou ME
1003 AM EDT Wed Aug 29 2018

MEZ001>006-010-011-015-031-032-292115-
Northwest Aroostook-Northeast Aroostook-Northern Somerset-
Northern Piscataquis-Northern Penobscot-Southeast Aroostook-
Central Piscataquis-Central Penobscot-Southern Penobscot-
Southern Piscataquis-Northern Washington-
Including the cities of Allagash, Clayton Lake, Madawaska,
Fort Kent, Frenchville, Presque Isle, Caribou, Van Buren,
Mars Hill, Baker Lake, Billy-Jack Depot, Baxter St Park,
Chamberlain Lake, Churchill Dam, Mount Katahdin, Millinocket,
East Millinocket, Patten, Medway, Houlton, Hodgdon, Sherman,
Smyrna Mills, Greenville, Monson, Blanchard, Lincoln, Howland,
Springfield, Bangor, Brewer, Orono, Old Town, Dover-Foxcroft,
Milo, Guilford, Danforth, Vanceboro, and Topsfield
1003 AM EDT Wed Aug 29 2018

...Strong to Severe thunderstorms are expected this afternoon into
early evening...

Strong thunderstorms are expected to develop across the region
this afternoon and continue into early evening. Thunderstorms have
the potential to become Severe with the highest threat across the
Piscataquis, Penobscot and Mount Katahdin region. Severe thunderstorms
may contain strong wind gusts in excess of 58 mph with very heavy
rainfall. Hail up to one inch in diameter and rotation is
possible in the more intense storms.

Continue to monitor the National Weather Service or your local
media outlet for updates on this developing weather situation.

Hewitt