Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Caribou ME
1210 PM EST Friday Feb 12 2016
high pressure will briefly cross the region today. Low pressure
will track south of the area Saturday and Saturday night while a
surface trough extends inland across our area. Another Arctic
high pressure from central Canada will approach on Sunday and
cross the region on Monday.
Near term /through tonight/...
1210 PM update...we have issued wind chill headlines for late
Saturday night into Sunday morning for wind chills of -20 to -40.
Coldest readings will be in the North Woods. Other headlines
remain the same for now...
Quiet weather continues this afternoon. Have made some adjustments
to sky, winds, and temperatures to match current conditions. No
significanat changes needed.
Previous discussion...current wind chill hdlns over the northwest and
extreme NE are marginal at best...with actual wind chill advection criteria
only be met over msly higher terrain lctns. Otherwise...still a faint snow
shower streamer extending over Mars Hill from kpqi...but the latest
radar trend is toward dissipation...so we do not have any mention
of snow showers in the forecast for today at this time. Hi temperatures will be sig colder
today...ranging from the middle single digits over the extreme north to middle
teens along the downeast coast.
Clouds will increase tonight across the region ahead of an Alberta
clipper shortwave approaching from central can. Scattered snow showers and steady light
snfl will move into the forecast area from the west-southwest late tonight...with the best
potential of sig accumulating snfl beginning along the downeast
coast of Hancock County by daybreak as an inverted norlun surface
trough orientated toward this portion of the forecast area from the Gulf of ME
sharpens. Overnight lows will be coldest over NE valleys...where skies
will remain overcast free longest into the night. Elsewhere...overnight lows
will occur prior to the late night hours...with temperatures recovering late
under thicker cloud cover and an east-southeast surface wind.
Short term /Saturday through Sunday night/...
a classic norlun type 2 will set up late Friday night as the
clipper low transfers energy to a low well south of Cape Cod and
leaves an inverted trough along the coast. This could be the
biggest norlun event in many years along the down East Coast.
There will be a fairly deep unstable layer to over h600 moving
east along the coast late Friday night through Saturday and it
could produce some impressive snowfall rates approaching 2 or more
inches an hour. As is always the case with norlun troughs...the
big question will be where it sets up. Most guidance has continued
to favor coastal Hancock County for the inverted trough location
through most of Saturday. The trough then moves into Washington
County later in the day as it weakens. On the other hand...the NAM
continues maintain the trough location just west of Penobscot Bay
in the more climatologically favored area. These troughs are often
an all-or-nothing proposition with a very high bust potential due
to the fact that they are very narrow with sharp gradients and do
not necessarily extend inland as far as guidance. For now...have
taken a composite approach with amounts reaching 15 inches in
coastal Hancock County with a sharp cutoff east of Machias due to
high snow ratios along the narrow surface convergence line. The
concern remains that it will end up on the other side of Penobscot
Bay as the nam12 has been showing with minimal snow along the down
East Coast. Blowing snow will likely be an issue as the trough
finally moves east and winds increase.
Elsewhere...some snow can be expected inland along the narrow inverted
trough axis extending northwest towards Bangor and southern Piscataquis
County where snowfall amounts will taper to 3-4 inches. Have
concerns that forecast snow totals in Bangor are too high based on
the nature of norlun troughs and the propensity of guidance to
extend quantitative precipitation forecast too far inland. It will dry elsewhere with highs near
10f towards the Saint John valley and low-middle 20s on the coast.
Winds pick up late day and continue through the night as the
coldest air of the season advects into the forecast area. A Wind
Chill Advisory is likely as wind chills drop to -20 to -30f by
Highs on Sunday will be quite a bit colder than Saturday with
highs around zero north and low single digits everywhere else. The
wind continues Sunday with Wind Chill Advisory headlines highly
likely through the morning. High pressure builds later Sunday
night. Have continued to take a conservative approach to
temperatures with this forecast due to the narrow ridge and the
expectation that winds continue through the night...but if the
ridge crests Sunday night...temperatures could go much lower. The
entire area will be below zero Sunday night with near -15f in the
Allagash and zero to minus 10 through the rest of the area.
Long term /Monday through Thursday/...
expect sunny and cold conditions on Monday as high pressure crests
the region. Highs will rebound to the teens. Temperatures will
drop off initially Tuesday night...but clouds will increase
quickly with overrruning snow breaking out during the night.
Several inches of snow will be possible before the warm front
moves north of the state Tuesday evening. Very strong warm air
advection will occur from Monday night through Wednesday
morning...bringing temperatures towards 50f along the coast
Tuesday night and 40s for the entire area. The track of the low
now seems to be solidly west of the state. This means that the
primary threats will be heavy rain...high winds and flooding. The
western track mitigates the heavy rain risk to some degree as the
best forcing moves west of the state. Total quantitative precipitation forecast including the
initial snowfall now stands around one to two inches.
Nonetheless...the rainfall and warm advection raises flood
concerns due to snowmelt and ice movement. The current forecast
track brings the high wind threat to the forefront. A low level jet is
prognosticated to reach a strength of 80 to 90 kts with strong potential
for mixing some of those winds to the surface near the coast.
Downed trees and power outages will possible. The threat of
coastal flooding in the usual spots must also be considered. The
warmth will be fairly short-lived...24 to 36 hours...as cold air
returns Wednesday with sharply colder air moving in Wednesday
afternoon. Very windy conditions are likely Wednesday across the
entire area with some gusts to 50 miles per hour conceivable.
Aviation /17z Friday through Tuesday/...
near term: msly VFR expeceted today...with brief MVFR clg intervals
possible across northern taf sites. Conditions lower to IFR late tonight
over downeast sites with the arrival of snow with the norlun trough
while clgs and attms...visibilities with snow showers lower to MVFR over northern
Short term: VFR through the period except LIFR at bgr and bhb
Saturday due to snow. IFR to LIFR is also expected to overspread
the area Monday night into Tuesday due to snow and low ceilings.
near term: the freezing spray and small craft advisories are no
longer in effect. Winds and seas are slowly subsiding, and don't
expect much more than just perhaps some light freezing spray
through the remainder of today. No other changes needed.
Previous discussion...will continue the Small Craft Advisory and fzg spy
advection for our mzs into Erly afternoon...at which point both will be
lowered only to be re- issued as new hdlns for both wind and fzg
spy again later Sat. Kept close to ww3 WV guidance for forecast WV heights
today and tonight.
Short term: a gale is forecast Saturday night into Sunday evening
with fzg spy hdlns. A storm is possible by Tuesday night.
ME...Wind Chill Advisory from 2 am to 10 am EST Sunday for mez002-
Wind chill warning from 2 am to 10 am EST Sunday for mez001-
Winter Storm Watch from late tonight through late Saturday
night for mez015-016-029.