Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/12/18

Area Forecast Discussion

National Weather Service Bismarck ND

 904 PM CST Tue Dec 11 2018

.UPDATE...
Issued at 903 PM CST Tue Dec 11 2018

Areas of fog continue to develop across portions of north central
North Dakota, and the southern James River Valley per NDDOT
webcam, GOESEast, and surface observation trends through 03 UTC.
The fog is most dense and with the greatest areal coverage across
the lower Souris Basin and into the Turtle Mountains. Will
continue to monitor trends should a Dense Fog Advisory become
necessary.

UPDATE Issued at 534 PM CST Tue Dec 11 2018

No significant change to the forecast for tonight with this
update. A rain and snow mix across the southern James River
Valley will continue to shift east over the next 1-2 hours.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 223 PM CST Tue Dec 11 2018

A trough of low pressure now moving through the James river
valley will keep some likely chances for rain and snow across the
southeast through early this evening. CAM models have been seeing
some fog developing following the trough passage across the far
eastern counties, and have added fog using the HRRR as the
primary model. Considered some patchy freezing drizzle as the dry
air moves in behind the system this evening, however their seems
to be sufficient ice aloft to prevent much of this.

Wednesday will see another clipper move in from Montana. This will
bring some gusty winds across the southwest. Looked at NAM and
GFS soundings, and bumped the winds up about 10 mph over
SuperBlend guidance, but still did not reach advisory category.
But some linkup potential for breezy to windy conditions Wednesday
afternoon and evening southwest. The clipper will also spread
some low chances for rain and snow, but pops have trended lower
with each successive run so not impressed with teh precipitation
potential. Wednesdays highs will reach into the lower 40s
southwest and 30s elsewhere.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 223 PM CST Tue Dec 11 2018

The extended looks dry and mild as a broad ridge moves east into
the northern plains Thursday and Friday. A weak but dry clipper
moves through Saturday, followed by a warmup again through the
end of next week. Current indications show the 6 to 10 day
temperature outlook would be exceptionally warm if the low levels
mix out by next weekend. Currently we have mid 40s for highs
southwest and 30s elsewhere, but even upper 40s would be possible
in a good mixing environment.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 903 PM CST Tue Dec 11 2018

Areas of freezing fog will continue to develop across central
North Dakota tonight with LIFR visibility possible. VFR conditions
are expected across western North Dakota tonight. Westerly winds
will increase across western North Dakota Wednesday afternoon,
spreading into the central during the evening behind a cold front.
Gusts of 30-35kts are forecast. Low level wind shear is possible
Wednesday afternoon across the west with strong winds off the
surface. Scattered rain and snow showers are also possible
tomorrow with the passage of the front.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...PA
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...PA



Area Forecast Discussion

National Weather Service Caribou ME

 913 PM EST Tue Dec 11 2018

.SYNOPSIS...
A cold front will cross the region later tonight as weak low
pressure tracks east across the Gulf of Maine. High pressure
will build across the region later Wednesday through Thursday
and remain over the area on Fri.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
9:13 pm update: A weak area of low pressure is moving up the
Midcoast of Maine with a Norlun trough expected as the weak meso
low pulls away overnight. Thus far, the returns on the KGYX and
KCBW radars have not been all that impressive with nothing more
than about 15 dbz returns. Light snow was reported at Rockland
and the visibility briefly dropped to 3/4 mile before quickly
improving to 9 miles. Some very light snow or flurries has
reached KBHB and also flurries have been observed in a few spots
in far northern Maine. It still seems reasonable that some
locations especially along the Hancock County coast and outer
islands will locally pick up a few inches of snow overnight. As
it is not looking all that impressive on radar will hold the
course with no advisories. That said, with a high fluff factor,
we can`t entirely rule that some spot picks up several inches of
snow, but based on the latest radar returns it is not looking
likely. The latest few runs of the HRRR have been consistent
that most the accumulation will be over by around 10Z Wed
morning. Made some tweaks based on the latest observations and
trends, but nothing all that drastic.

Previous discussion:
The tricky part of the fcst tngt will be the potential of a
compact Norlun event for msly Wrn coastal Downeast areas, spcly
late tngt into erly Wed morn. The consensus of 12z synoptic
scale and a bunch of recent hrly meso model output suggests that
a meso low ovr the Casco Bay will come under the influence of
initial s/wv energy from the great lks this eve, and then some
additional s/wv energy from Nrn QB late ngt. This interaction
will likely result in an area of ocean sn to xpnd ENE from the
Gulf of ME toward the mid Maine coast and Wrn coastal Downeast
areas lathe this eve into the late ngt hrs, with potential brief
mdt sn rates between 1 and 4 am for coastal Hancock county.
With this fcst update, we increased PoPs to categorical and sn
amts to just below wntr wx adv thresholds alg the immediate
Hancock coast and outer islands. Due to the tmg of the event
late at ngt, it will be difficult to real tm reports, so
monitoring radar ref trends will be important in the event we
need to go with wntr wx hdlns in this small area of our FA. In
any event, any organized snfl or coastal areas will quickly wind
down to sct sn shwrs aft 6 am Wed as the upper trof axis
crosses the area.

Elsewhere, skies will become ptly to msly cldy ovrngt as SC
ahead of the cold front and s/wv from Nrn QB apchs the FA. Isold
sn shwrs ovr the Rgn with perhaps sct sn shwrs ovr the mtns can
be xpctd late tngt into Wed morn with the passage of these
features with ovrngt lows not as cold as last ngt due to greater
xpctd cld cvr. Following the cold front, sn shwrs should end
and skies will gradually become msly clr to ptly cldy by Wed
aftn as brisk NNW winds cont. Hi temps Wed aftn will be similar
to tdy, but the wind chill factor will make it feel much less
comfortable.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Sfc high pressure cntrd to the west of CWA at the start of the short
term pd. Clr skies and lgt winds wl mean another night of well-blo
zero temps acrs the north with some favored locations ovr nrn
Aroostook possibly making another run at -20F by daybreak tho H9
temps wl be warming by 12z.

Temps wl be moderating thru the end of the week with maxes on Fri
likely to climb close to normal values. Upr lvl ridge building acrs
the northeast likely to be undercut by weak wv zipping thru srn New
England Thu night. On Fri H5 heights rise to +560dm with highs
u20/nr 30 acrs the north and climbing abv frzg in Downeast areas for
the first time in a week.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Both the 12z GFS and EC keep the nrn and srn streams separate ovr
the weekend. Cannot rule out chc pcpn Fri night into Sat with the
upr lvl trof crossing CWA with lkly pops rmng south of the coast as
main upr low rmns deep into the srn U.S. CMC indicates a little more
phasing as it brings H5 low slightly further north than rmng
guidance does on Fri.

Models vary aft 00z Sun with EC much stronger with sfc high as it
builds in fm the Great Lks keeping the secondary low ovr the coastal
Carolinas as opposed to the GFS off of the mid-Atlantic with just an
open wave trof on CMC as it is much more progressive with system and
wl mostly discount this soln. Temps wl slide to slightly blo normal
by the end of the long term.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: Nrn TAF sites will begin VFR this eve then transition
to MVFR SC cld cvr late tngt into Wed morn, then sct out to VFR
again by Wed aftn.

Downeast sites will be MVFR or low IFR tngt, with KBHB likely
becoming IFR in a short pd of steady lgt snfl late tngt. Both
sites should transition back to VFR durg the morn Wed and remain
so Wed aftn.

SHORT TERM: VFR conditions expected through the end of the week.
Restrictions look to lower beginning Fri night into Sat
depending on the track of the low pressure system.

&&

.MARINE...
NEAR TERM: Initially lgt winds and seas, then winds increase
late tngt into Wed morn to SCA behind a departing sfc low movg E
across the Gulf of ME and cold front. SCA winds will then cont
thru the remainder of the day as llvl cold advcn increases ahead
of Can sfc hi pres from Nrn QB. Went with a blend of NWPS/WW3
guidance for fcst wv hts.

SHORT TERM: SCA conditions will linger into the very early part
of the short term. After this time winds and seas will remain
below SCA levels through the end of the week.

&&

.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory from 5 AM Wednesday to midnight EST
     Wednesday night for ANZ050>052.

&&

$$

Near Term...CB/VJN
Short Term...Farrar
Long Term...Farrar
Aviation...CB/VJN/Farrar
Marine...CB/VJN/Farrar