Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/12/20
See below for an aviation forecast discussion for the 00Z TAFs.
&&
.SHORT TERM...(This Evening through Wednesday Night)
Issued at 339 PM CST Tue Feb 11 2020
Powerful Arctic boundary is on its way early Wednesday with very
strong winds along and behind it. The ops models along with hi-res
models show that there should be some light snowfall from upper
level lift with the upper level low pressure trough axis moving
through early Wednesday. The Arctic front will then follow quickly
with a big pressure surge (up to 10mb+) along with rapidly falling
temperatures. We should see snow squall type/blizzard conditions
along the front as the hi-res models have depicted this with the
enhanced radar reflectivity output. Snowfall amounts should be
around an inch or less. With the existing snow cover combined with
the new snowfall and strong north winds gusting to 40 to 50 mph,
issued a blizzard warning for the eastern cwa for Wednesday. With
less snow to blow around with the strong winds, went with a Winter
Weather Advisory from Brown county and west to the Missouri River
for Wednesday. The snow will end quickly by noon with the winds
continuing through the afternoon. Otherwise, wind chills will fall
quickly through the day and evening to 25 below to 45 below zero.
Clearing skies Wednesday night with enough winds, temperatures will
fall to the teens to around 20 below zero. Therefore, dangerous wind
chills will continue into Thursday. Issued a Wind Chill
Advisory/Warning for much of the region Wednesday afternoon into
Thursday morning.
.LONG TERM...(Thursday through Tuesday)
Issued at 339 PM CST Tue Feb 11 2020
Arctic high pressure will be in place over the region on Thursday,
with high temperatures likely remaining below zero from the James
valley and points eastward. Winds will be light on Thursday with the
surface high in place, but will still be dealing with possible wind
chill headlines through the day Thursday and more so Thursday night
into Friday as the return flow sets up again and southerly winds
increase. Quick warm up Friday and through the weekend as 925/850 mb
temps rebound. 20s, 30s, and even 40s across the southwest counties
are in the forecast for this time period.
As for precipitation, the start of the period looks quiet, with just
a weak shortwave crossing the region Friday night into Saturday
morning. This wave may bring some light snow to parts of the CWA,
but moisture looks to be lacking. Models show potential for perhaps
a stronger storm system early next week. But obviously, way too
early to concern ourselves with specifics - will just continue to
monitor model trends over the next few days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 644 PM CST Tue Feb 11 2020
VFR conditions are expected through 06Z. Beyond that, in the late
night hours and on into Wednesday morning, an arctic front is
expected to push through the region bringing light snow and very
strong north winds and blowing snow. Sub-VFR vis/cigs are
expected at all terminals through, at least, the first half of
Wednesday. KABR/KMBG/KATY may experience a short window of IFR
conditions with KATY reaching short lived blizzard conditions and
KMBG/KABR reaching near blizzard conditions for a brief time
Wednesday morning. Falling snow should be over by 18Z Wednesday,
and by 00Z Thursday, VFR cigs/visbies should be returning as wind
speeds back down and blowing snow diminishes.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 4 AM to noon CST Wednesday for
SDZ004>006-009-010.
Wind Chill Advisory from noon Wednesday to noon CST Thursday for
SDZ004>006-009-010-016>018-034-036-037.
Wind Chill Warning from noon Wednesday to noon CST Thursday for
SDZ007-008-011-019>023.
Blizzard Warning from 4 AM to 6 PM CST Wednesday for SDZ007-008-
011.
Winter Weather Advisory from 6 AM to 6 PM CST Wednesday for
SDZ016-017-034-036-037-051.
Blizzard Warning from 9 AM to 6 PM CST Wednesday for SDZ018>023.
MN...Wind Chill Warning from noon Wednesday to noon CST Thursday for
MNZ039-046.
Blizzard Warning from 4 AM to 6 PM CST Wednesday for MNZ039-046.
&&
$$
UPDATE...Dorn
SHORT TERM...Mohr
LONG TERM...TMT
AVIATION...Dorn
Area Forecast Discussion
National Weather Service Bismarck ND
952 PM CST Tue Feb 11 2020
.UPDATE...
Issued at 941 PM CST Tue Feb 11 2020
Light snow has spread across a good portion of western and central
North Dakota. Surface low pressure was located over far northwest
North Dakota, with the Arctic cold front just pushing into the
northern tier counties.
No significant changes with the overall pattern and still looks
like a general 1-3 inches of snow across the forecast area.
However, the latest mesoscale models and new NAM have trended a
little farther west with the area of heavier snow, tracking from
western into south central ND, and have also trended a little
lighter with snow amounts over the Turtle Mountains area. Overall
though, nothing to warrant any changes to the current hazards.
Updated text products will be sent shortly.
UPDATE Issued at 537 PM CST Tue Feb 11 2020
The main adjustment to the forecast late this afternoon was to
delay the start time of the advisory over the north central until
9 PM this evening. Previous start time was 00 UTC and the Arctic
front remains a ways away from the border. Latest RAP shows the
front moving into the area around 03-04 UTC.
Otherwise for the update we made some minor adjustments to the
timing of the arrival of precipitation, slowing it down a little.
We also bumped up sky cover.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 313 PM CST Tue Feb 11 2020
The main concern for the short term period is the powerful Arctic
cold front sweeping through the region tonight into Wednesday.
Hazards include light snow accumulations, blowing snow with near
whiteout conditions in open areas, and eventually, very cold wind
chills.
Currently, a surface arctic cold front extended west-east across
central Alberta to central Manitoba. Southwest surface winds to its
south allowed a mild February day across the northern tier states,
with temperatures this afternoon in the 20s and 30s. At upper
levels, a large Hudson Bay Low was well established with
northwesterly flow across western Canada and the northwestern and
north central US. A significant shortwave in the upper flow was over
southern Alberta, with its coincident surface low along the western
side of the arctic front.
The upper level shortwave and its attendant clipper-type low will
dive southeast into Montana/the Dakotas tonight. This arctic cold
front associated with the clipper system will plunge south, arriving
in northern North Dakota during the evening hours and continuing
south into the central Plains states on Wednesday.
Light snow will accompany the front, and will begin early this
evening in the far north and far west. Latest model guidance
continued to result in 1-3 inches of snow for much of the area.
Simulated reflectivity, negative EPV, and strong frontogenesis
suggest the potential for enhanced snow rates, but think it would be
a transient threat and not significantly add to the big picture
accumulation forecast. The dendritic growth zone is deep, but only
lasting a few hours within the arctic frontal zone.
The greatest concern with the Arctic frontal passage is strong winds
resulting in impactful blowing and drifting snow. Not much has
changed in the model data over the past 24 hours. Very strong
pressure rises (over 10 mb/3 hr) and cold air advection accompany
the front, but still struggling to find boundary layer winds
exceeding 40 kts. The timing of the frontal passage on the 12z
models is similar to that of the 00z runs from last night. This will
mean that the arctic front moves through the state during the
nighttime hours before any diurnal effects on mixing can be
realized.
We are expecting peak wind gusts around 45 mph, which will likely
not be strong enough to break the crust of the existing snowpack.
However, the forecast snow amounts create a greater potential for
blowing snow significantly reducing visibility, and for at least a
few hours in duration. For this reason, we will continue the Winter
Weather Advisory for blowing snow, generally along and east of
Highway 83. The winter weather advisory lines up with where the
strongest winds are expected. Near blizzard conditions are possible
in rural areas across the James River Valley. Given the current
forecast, confidence is not high enough in blizzard criteria being
reached over a geographically significant area to warrant a warning
or even a short-fused watch. For areas of western North Dakota, we
issued a Special Weather Statement earlier today for the rest of
western/central North Dakota. This Special Weather Statement will be
re-issued for tonight and Wednesday...addressing the sub-advisory
snow/blowing and drifting snow, etc. Travel impacts are possible
even though advisory criteria may not be met.
Temperatures are expected to fall through the day Wednesday, with
daily maximums occurring very early Wednesday morning ahead of the
frontal passage. Winds will slowly diminish Wednesday afternoon.
Advisory criteria wind chills appear likely north and east of the
Missouri River Wednesday morning through Thursday morning. As the
winter weather advisories end on Wednesday, they may need to be
replaced/extended because of wind chills.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 313 PM CST Tue Feb 11 2020
Arctic high pressure will reside over the Northern Plains Wednesday
night into Thursday. Widespread low temperatures in the 10 to 20
below zero range are expected. Wind chills will remain a concern
north and east of the Missouri River Wednesday through Thursday
morning. Daytime highs for Thursday will be mainly in the single
digits above zero with a chance at getting into the teens in far
western North Dakota.
Mild Pacific air under an upper level ridge will quickly push into
the region Thursday night into Friday, bringing temperatures back to
near to perhaps even above average, with highs above freezing across
the western third of the state on Friday. A shortwave trough will
move across the area late Friday into Saturday. Timing differences
and small precip amounts in the models resulted in no chances or
very slight chances of light precip Friday/Saturday.
The synoptic pattern continues to look progressive into early next
week, with near to above normal temperatures remaining favored. The
deterministic GFS/ECMWF and several GEFS members now show a chance
of very light snow accumulations around the late Sunday/Monday
timeframe.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 941 PM CST Tue Feb 11 2020
VFR conditions to begin the 00Z TAF period. An arctic cold front
and a clipper system will combine to produce a period snow
(generally 1-3 inches) along with strong winds, producing areas of
blowing and drifting snow. Snow will move into the west this
evening. The Arctic cold front will drop north to south late this
evening and overnight. Expect a period of MVFR to occasionally IFR
ceilings and visibilities in snow and blowing and drifting snow
at all TAF sites. The worst conditions will be late tonight
through mid morning on Wednesday. Expect VFR conditions to return
to southern areas by early afternoon Wednesday with North to
northwest winds diminishing through the afternoon.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon CST Wednesday for NDZ004-005-
012-013-022-023.
Winter Weather Advisory until 6 PM CST Wednesday for NDZ025-
035>037-046>048-050-051.
&&
$$
UPDATE...TWH
SHORT TERM...JV
LONG TERM...JV
AVIATION...TWH
Area Forecast Discussion
National Weather Service Caribou ME
1047 PM EST Tue Feb 11 2020
.SYNOPSIS...
Low pressure will exit well south of Nova Scotia this evening,
followed by high pressure building over the area through
Wednesday. Another Low pressure approaches from the southwest
Wednesday night, then tracks over the Gulf of Maine Thursday.
An arctic front pushes through later on Thursday followed by
Canadian high pressure building in through Saturday. The high
will then slowly move east of the area Saturday night and
Sunday.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
1035 PM Update...Still some reports of patchy freezing drizzle,
but there things are improving. RAP and CAR 00Z sounding
supported potential for some freezing fog overnight. Radar
showed enhanced returns pulling across eastern Washington County
attm as low pres passes s of Nova Scotia. Temps have cooled
down AOB 32F as far s as Bangor w/light rain changing to snow.
Temps were still in the mid 30s along the coast w/light rain.
Temps will continue to cool down and light rain along the coast
could change to a brief period of snow before ending. A weak
cold front or trof across western Maine this evening is expected
to slide across the region overnight into Wednesday.
Flurries/isolated snow showers are expected along the northern
and western border. No accumulation is expected. Adjustments
were made to the temps.
Previous Discussion...
Sfc high pres well SW of the FA will ridge into the Rgn on Wed,
providing partly to msly sunny skies and mild temps. However, a
stronger sfc pres grad and winds alf in the 925 to 850 mb layer
will result in much breezier conditions by midday contg into
the aftn hrs. By late in the aftn, clds will begin to increase
ovr the far N in advc of a strong arctic cold front movg E of
QB.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Main concern is a system for late Wednesday night into Thursday
with advisory level snow possible mainly southern half of the
area. This system is relatively weak with a shortwave upper
trough moving in from the Great Lakes and a weak surface low
forming in the northern Gulf of Maine. With this system not
having a whole lot of amplitude, it won`t be able to tap into
much warm air ahead from the south, and precip type looks like
mostly snow except perhaps rain mixing in along the coast. One
interesting aspect of this system is an Arctic front moving
through from north to south on the tail end of the system. This
could provide some local enhancement of the snow before it
tapers off, plus allow for plummeting temperatures Thursday
afternoon and night after the snow tapers off. Winds don`t look
terribly strong behind the Arctic front, but it could possibly
be enough for a bit of blowing snow. Something to keep an eye
on. Do not expect any freezing rain or sleet with this system.
Models are in pretty good agreement. Much colder for Friday and
breezy with highs around 0 in the north and 10 to 15 Downeast.
May need a wind chill advisory Northern Maine late Thursday
night into early Friday.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Friday night has the potential to be bitterly cold as Arctic
high pressure moves in late in the night. Undercut most
temperature guidance and went for lows below zero virtually
everywhere, and as cold as about -30 in some of the usual
coldest spots in the North Woods. Still cold on Saturday but not
quite as bad since the high moves east with some moderation of
the airmass in the afternoon. Weak system for Sunday and milder
with a chance of snow showers, perhaps followed by another shot
of Arctic air Sunday night into Monday, though models disagree
on how far south the Arctic front makes it. For example, 12z
ECMWF has it stalling over the area. Next potential system is
Tuesday/Tuesday night. Models actually are in pretty good
agreement on there being a system around this time...above
average agreement for being so far out. Went with likely PoPs.
This system has the potential to be fairly strong and appears
likely to tap into deep moisture from the south. Way too early
to determine precip type, but this is the type of system where
all precip types could be on the table.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: Tonight...IFR to low MVFR clgs with ocnl MVFR vsbys
in any lgt sn or sn shwrs Nrn TAF sites this eve, then MVFR clgs
ovrngt. IFR to low IFR clgs Downeast with MVFR/IFR vsbys in lgt
rn and sn, becmg MVFR clgs late tngt. Lgt winds all sites.
Wed...VFR all sites. Mdt NW winds.
SHORT TERM: Wednesday night...VFR early, perhaps becoming MVFR
late with snow developing. Fairly light winds.
Thursday...MVFR and IFR with widespread snow, possibly mixed with
rain from KBGR south. Fairly light winds until late Thursday
when an Arctic front moves through and brings a decent N breeze.
Thursday night and Friday...Mostly VFR except possible MVFR
ceilings north. North breeze.
Friday night and Saturday...VFR with light winds.
Saturday night and Sunday...Mostly VFR Downeast, with MVFR
possible north. SW breeze.
&&
.MARINE...
NEAR TERM: No chgs to the SCA issued for very erly morn til erly
aftn Wed. Until then winds and seas below SCA thresholds. Winds
and seas should again subside below SCA thresholds mid to late
aftn Wed. Kept close to blended model wv guidance.
SHORT TERM: Conditions improving below small craft by Thursday
morning. Conditions back to small craft Thursday night and
Friday with an offshore wind and seas over 5 feet. Good chance
of moderate freezing spray in this period as well. Back below
small craft Saturday, then another shot at small craft seas and
winds Sunday.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Small Craft Advisory from 3 AM to 1 PM EST Wednesday for
Anz050>052.
&&
$$
Near Term...Hewitt
Area Forecast Discussion
National Weather Service Nashville TN
828 PM CST Tue Feb 11 2020
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Some light showers are moving through the area with MRMS QPE
showing less than one tenth of an inch in the last 3 hours along
the southern tier of counties. Elsewhere, any rainfall has been
just a hundredth or two. HRRR shows more light showers overnight
with no significant rain amounts. With the blanket of cloud cover,
temperatures will not move much the rest of the night. The
current forecast is on track. Only made minor adjustments to
hourly temperatures and PoPs.
&&
.AVIATION...
00Z TAF DISCUSSION.
A couple of spots are still MVFR but it looks like KBNA/KMQY/KCKV
should improve to VFR for several hours overnight as the warm
front takes its time moving northward. Conditions should start to
deteriorate again by 10-11Z with IFR and more showers settling in
by mid-morning Wednesday. TS will be possible near the end of this
TAF cycle, but for better timing, will wait until 06Z issuance to
prevail.
Winds will remain light tonight and most of tomorrow, but swing
from the north to the east by tomorrow afternoon.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from Wednesday evening through Thursday
morning for Cumberland-Fentress-Grundy-Overton-Pickett-Putnam-
Van Buren-Warren-White.
Flash Flood Watch from Wednesday afternoon through late
Wednesday night for Bedford-Cannon-Cheatham-Clay-Coffee-Davidson-
De Kalb-Giles-Hickman-Jackson-Lawrence-Lewis-Macon-Marshall-
Maury-Perry-Robertson-Rutherford-Smith-Sumner-Trousdale-Wayne-
Williamson-Wilson.
Flash Flood Watch from Wednesday afternoon through late
Wednesday night for Dickson-Houston-Humphreys-Montgomery-Stewart.
&&
$$
DISCUSSION......Reagan
AVIATION........Unger
Area Forecast Discussion
National Weather Service Pocatello ID
105 PM MST Tue Feb 11 2020
.SHORT TERM...Tonight through Thursday. Northwest flow will
continue around the ridge currently centered near the coast.
There is a chance of light snow that will remain through this
period across portions of the central mountains,
Centennials/Island Park, and south through the eastern and
southeast highlands. Snow amounts will be light, although we could
see on occasion like Monday where a band or burst of snow could
create slick roads. We will also be watching for expanding stratus
and possible fog the next 2 mornings as inversion strengthen. A
couple of other areas we COULD see light snow will be 1) tomorrow
morning across the South Hills/Albion Mountains as the next storm
drops down the Divide, and 2) under any stratus deck. This would
be courtesy of the "seeder feeder" process. Under the inversion,
expect much colder temperatures. Lows will likely be in teens to
single digits below zero at night, and 10s-20s during the day.
Where we can get some mixing, especially across the Lower Snake
Plain, Magic Valley and lower elevations south of I-84 &
86...highs will jump above freezing and some cases above 40
degrees! Keyes
.LONG TERM...Thursday Night through next Tuesday. The next storm
moves in Thursday night and Friday. The normal runs of the GFS and
ECMWF are slowing this down by a good 6-12 hours, while the Blend
of Models is still on the faster side. This storm won`t dump a lot
of precipitation, maybe 1-3" in favored upslope areas like the
Sawtooths and eastern highlands. Other places will see little snow
and/or a mix of rain and snow depending on the time of day. Winds
kick up so there could easily be some blowing and drifting up in
the high country. This trend of normal model runs slower vs the
Blend continues with the next storm over the weekend. Whenever the
storm does arrive, this one should a lot more moisture and warm up
to work with. Rain, snow and some decent wind will occur, with a
mix likely from Pocatello to Burley and points south...and snow
likely everywhere else. With this storm have more moisture and
"wet" snow, blowing and drifting conditions might be a little less
of an issue...but certainly not a "zero issue" either. Another
storm will quickly follow on its heels and be here on Tuesday.
Keyes
&&
.AVIATION...A weak shortwave disturbance diving SE across MT tonight will deal a
very minor, glancing blow to our region, with increased clouds and
some snow showers possible in some of our highlands/mntns
(especially as you head toward the MT/WY borders). The coarser NAM12
continues to bring this activity through KDIJ and builds showers as
far SE as KIDA, but none of the higher resolution models are as
aggressive at spilling snow into the Snake Plain, so we have removed
VCSH from KIDA this afternoon and probably can drop it from the TAF
for this evening too unless things change. SN will remain possible
at KDIJ tonight and Wed AM, with snowfall rates being the main
driver for vis reductions, currently forecast to MVFR but IFR is
also possible and can occur easily as soon as steady snow takes
hold. Otherwise, greatest forecast uncertainty revolves around
potential for some low stratus/additional fog tonight, especially at
KIDA. A better signature for low- to mid-level cloud decks on NAM
time-heights may keep fog at bay by reducing near-surface
radiational cooling, and we don`t see strong indications of fog in
the MAV/MET guidance or HRRR products, so for now we maintained VFR
cigs/vsbys in the TAF. However, surprise fog occurred last night
despite virtually no support from model guidance, so we will need to
monitor this potential hour-by-hour this evening...there may not be
much lead time if it occurs. Also nudged diurnal winds down by
several knots this afternoon at nearly all sites to better match
observation trends and 12z MOS guidance. - KSmith
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$