Scientific Forecaster Discussion
fxus61 kcar 190212
Area forecast discussion
National Weather Service Caribou ME
912 PM EST Mon Nov 18 2019
low pressure will track east of Cape Cod towards Nova Scotia
tonight. An upper level trough crosses the area Tuesday into
Wednesday before high pressure builds in on Thursday. Another
low pressure system will pass to the north on Friday followed by
high pressure on Saturday.
Near term /through Tuesday/...
9 PM update...as of 9 PM the leading edge of freezing rain was
on a line from just south of Fort Fairfield down to the katahdin
region and pretty much on track. Had to adjust temps down about
a degree across the north. Otherwise no major changes were made
Low pressure system is working it's way north toward the srn tip of
Nova Scotia in line with best 3-hrly pressure falls. Sfc ridge
axis and dry air conts to hold tight acrs the north and wl
likely not erode until closer to midnight. Current temps are
hovering in the lwr 30s at most all locations except where they
hv risen into the u30s/nr 40 along the coast. 12z guidance has
trended colder with the biggest ptype challenge area ovr cntrl
areas of the County Warning Area tonight.
Steady rain rotated into interior downeast areas over the past few
hours and is working north into locations where sfc temps are
more questionable. Mesowest obs showing temps around 32-34
degrees in portions of the Central Highlands and in the
Penobscot valley. With warm lyr FM 900-850mb appchg +5c as of
the current time cannot rule out isolated pockets of frzg rain
along the I-95 corridor for a good part of the evening hours.
Aft midnight ptype wl flip-flop btwn frzg rain, sleet or just
plain rain, especially in srn Piscataquis County where deeper
vlys reside and may hold onto cold sfc temps longer. For the
time being wl allow winter wx advisory to expire for the srn
segment at 06z and allow later shifts to monitor for possible
Further to the north we will likely see the full gamut of ptypes
acrs most of the nrn areas. Cold air aloft looks to hv a firm
grip acrs the North Woods with precip being all snow. Areas in a
stripe from about Moosehead Lake to the Mars Hill area and
either side of that line will likely see mixed precip in the
form of frzg rain, sleet and snow. As precip intensity picks up
expect dynamic cooling will lead to snow at times and as it
lightens, may see sleet or freezing rain at varying times thru
Overnight temps wl rmn nearly steady in the l/M 30s acrs the
south with temps dropping into the 20s ovr the north as NW flow
draws in colder air. As upr trof mvs twd and thru the region
tomorrow, expect a quick burst of hvy snow acrs the north into
Short term /Tuesday night through Thursday/...
snow showers associated with the Mon/tues storm will dissipate
rapidly Tuesday evening and overnight across the north. Much of
the deeper moisture will be absent for Wednesday, but forcing W/
upper trough will provide the chance for some snow showers
across the west and downeast. Downslope may prevent much in the
way of these showers in the north.
High pressure approaches Thursday, moving overhead Thursday
evening and overnight. This keeps the remainder of the short
term dry, with temperatures around normal.
Long term /Thursday night through Monday/...
on the heels of the high pressure center will be return flow and
increased pressure gradient W/ low pressure tracking north of
the Great Lakes. At this time, thurs night is expected to remain
dry, but precip will near the northwest forecast area Friday morning.
Track and evolution of the low varies, which will have an impact
on eventual quantitative precipitation forecast and precipitation types. Det GFS has a track
just south of James Bay, while latest European model (ecmwf) and Canadian take it
closer to the St. Lawrence rvr (a move nw). The gefs mean,
which was closer to the St. Lawrence previously, has shifted northwest
toward a Mid-Point between James Bay. The effect of a shift northwest
would lift much of the stratiform precip north of the area, but
still bring a wave through the County Warning Area.
Item to watch is if a sec low develops either on the coast or
further inland. This would modify the temperature profile the
most, potentially accelerating advection of warmer air from the
south and pushing rain/snow line north. Have not examined
details further for precip type, as location of low will be
resolved over coming shifts.
Temperatures cool on Saturday and Sunday as northwest flow wraps
around the low. This flow is interrupted with slight ridging at
the surface to reduce some cloud cover Sat night. Guidance
differs greatest late into the weekend, with eps intensifying
low pressure in the Gulf of Maine. GFS and Canadian hold a
stronger ridge to the south. This keeps low track more flat and
out to the open Atlantic. With little confidence in these
solutions, went with low pops as moisture will be in the region
amid an approaching wave.
Aviation /02z Tuesday through Saturday/...
near term: VFR across northern terminals until late evening.
MVFR restrictions in -fzra will move into hul by 01z, and mixed
precipitation by 05z at pqi and car. Fve will likely see IFR
snow from 07z through end of taf valid time. Ptypes will turn
over to IFR -sn at car and pqi after 10z with mixed
precipitation at hul after 10z. IFR -sn at hul after 15z.
Downeast terminals will see dominant -ra with low MVFR/IFR
restrictions thru 18z Tue.
Tuesday night and Wed: MVFR with lingering snow showers at
northern taf sites. VFR downeast except for a few scattered snow
showers in the afternoon with MVFR possible. Light northwest winds.
Wednesday night and thurs: VFR with light winds.
Thurs night and Fri: clgs/vsbys lowering to MVFR/IFR with snow
mixing with or changing to rain Friday. Winds shift S, and
increasing with gusts to 20kts.
Friday night and Sat: MVFR amid northwest winds with lingering snow
showers in the north and east taf sites. These taper Saturday
with northwest winds gusting to around 20kts.
near term: gales will continue tonight over all waters through
midnight. Will likely need an Small Craft Advisory thru the day on Tue as seas
remain aoa 5ft.
Short term: seas will remain near Small Craft Advisory criteria Wednesday and
Thursday, with north winds approaching 25-30kts Wednesday night.
Winds slacken and turn SW Thursday night, increasing Friday to
around 25kts Friday.
Seas will build to 6-8 feet Friday evening and overnight into
Sat as winds increase with gale possible Friday night.
a coastal flood statement was issued surrounding tonights high
tide for overwash/erosion at vulnerable areas (seawall Rd on
mdi, Roque Bluffs, etc).
Persistent surface winds from the NE will build surge close to
1 foot (according to etss) tonight ahead of an approaching
system south of the Gulf of Maine. This combined with high tide
above 10 feet MLLW, building near-shore waves 7-9 feet, and long
period swell around 12 seconds, will create the chance for
Winds turn north around high tide, reducing overall
surge/potential overwash impacts beyond this tide cycle as storm
ME...Winter Weather Advisory until 3 PM EST Tuesday for mez001>006-
Winter Weather Advisory until 1 am EST Tuesday for mez011-015-
Marine...Gale Warning until midnight EST tonight for anz050>052.