Mid-October Storm, including possible tropical system interaction, Update One

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FXUS61 KCAR 200403
AFDCAR

Area Forecast Discussion
National Weather Service Caribou ME
1203 AM EDT Thu Oct 20 2016

.SYNOPSIS...
High pressure will build across the region overnight. The high
will move east on Thursday. Low pressure approaching from the west
will bring rain Thursday night into Saturday.

&&

.NEAR TERM /THROUGH THURSDAY/...
12:03 AM update...Clear across the region as of midnight with
clouds to the north and west of Maine. These clouds should remain
at bay overnight. Temperatures have dropped back into the 30s in
the colder northern valleys, and some patchy river valley fog is
possible very late tonight into early Thursday morning. Only minor
tweaks to the ongoing forecast based mainly on the midnight
observations.

Orgnl Disc: Added patchy fog late tonight. Lowered tonight`s lows
with a very shallow inversion likely. Guidance usually does poorly
with such shallow inversions in the fall. Some of the bias-
corrected consensus blends are getting the right idea, but are
probably still not quite there. No frost advisories will be
issued. The frost/freeze program has ended for this season in our
forecast area. In terms of shallow patchy fog, forecast Skew- Ts
show nothing, but the dew points, strong subsidence, residual
surface moisture and time of year suggest otherwise.

For Thursday, guidance seems in good agreement with highs in the
mid to upper 50s and increasing afternoon clouds. Will ratchet pops
up sharply at the end of the afternoon into the evening. A wave of
low pressure currently in Oklahoma will organize and deepen on its
way to the Ohio Valley late Thursday. Piscataquis County could
receive a few hundredths of an inch of rain by evening.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
A large trough of low pressure will be approaching from the west
Thursday night as a very moist frontal boundary extending from over
the Appalachians north to the St. Lawrence valley begins to
approach. Some rain will be pushing into western areas ahead of this
front. From there, the forecast becomes complicated as the moist
frontal boundary remains to our west, the trough becomes more
negatively tilted, and increasing moisture from a tropical wave off
the southeast coast begins to approach. Rain will likely spread
across the rest of the area Friday as surface low pressure develops
off the Mid Atlantic coast. The rain will expand in coverage and
continue into Friday night with some bands of heavy rain likely as
the Mid Atlantic low lifts north across our area and the trough
becomes increasingly negatively tilted pulling tropical moisture
north. Some of the rain will continue into Saturday, mainly across
the north. However, drier air wrapping into the trough and lifting
up from the south will likely end the rain from south to north on
Saturday.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Surface low pressure will lift north of the area Saturday night as
strong, gusty south southwesterly winds wrapping around the low
buffet the area. Showers will continue in western areas. This will
be followed by a blustery and cooler day on Sunday as clouds,
showers, and a strong west southwesterly wind continues south of
departing low pressure. Rain showers may mix with snow showers
across the north late Sunday night. Monday will be drier but
remaining very chilly. Moisture wrapping back into the area beneath
the trough will bring clouds and rain and snow showers Monday night
into Tuesday. Drier but chilly weather will follow Tuesday night
into Wednesday as cold high pressure builds in from the west.