Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/20/22
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1002 PM EST Wed Jan 19 2022
.SYNOPSIS...
A strong cold front tonight will usher much colder air
into the region, and this bitterly cold air will stick around and
last into the weekend. A weak frontal wave may bring some light snow
to locations south and east of the Capital Region Thursday morning.
Snowfall amounts look light, but even the light amounts could result
in a slippery morning commute tomorrow. Afterwards, dry weather
dominates through the weekend into at least the beginning of next
week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Update as of 959 pm EST...A clipper low is moving across
southeast Quebec at this time. A band of snow showers is moving
across northern NY into the western Adirondacks and fell apart.
A short-wave move across w-cntrl PA is helping to increase the
low to mid-level FGEN for some light pcpn echoes to form south
of the region. The 00Z KALY sounding has a strong inversion at
800 hPA with dry air below it. Temps vary quite a bit as light
to calm winds and some holes in the cloud cover has allowed
temps in the Lake George Region/Glens Falls area to fall into
the 20s. The temps should rise or steady with the approaching
front.
The latest 01Z HRRR and shows light snow expanding
north/northeast into the s-cntrl Taconics/Mid Hudson Valley,
Berkshires and Litchfield Hills between 09Z-12Z. Lows will be
falling into the teens and 20s from the Capital Region north and
west with mid 20s to around 30F south and east. We kept a
slight chance of snow showers further north and west into the
Capital Region. Some lake effect snow showers and flurries will
also increase across the northwest portion of the forecast area.
Some accumulations will be a dusting to a tenth or two over the
north and west of the Capital District with a few tenths of an
inch to an inch or so over the Mid Hudson Valley, southern
Taconics and NW CT. Some slick spots are possible in these areas
for the morning commute. Some more details are below.
Previous near term...
Turning our attention to our southeastern zones...Late
tonight/early tomorrow morning, the cold front will be located
to our southeast near the coastline. AS an upper trough moves in
from the west, a southern stream shortwave embedded in
southwesterly flow aloft will track northeastward, bringing a
"surge" of increased moisture towards the region as a weak wave
of low pressure develops along the front. Additionally, we will
will be in a the right entrance region of a 300 mb jet streak,
and there may even be some jet coupling Thursday morning as
another upper- level jet streak moves off the Mid-Atlantic coast
to our south (putting our area in the vicinity of the left exit
region). Finally, there will be a band of enhanced
frontogenesis along the front itself. Combination of increased
moisture with mid and upper-level support will lead to a an area
of snow or snow showers developing along the front. This will
primarily impact our southeastern areas (Dutchess and Litchfield
Counties), with the highest amounts expected near the I-84
corridor. Best chance for snow appears to be between 4-10 AM
EST, and may initially start as a rain/snow mix (no ice
expected, though) before transitioning to all snow as colder air
works in. Total snowfall accumulations look to only be an inch
or two, but given that this snowfall will coincide with the
morning rush hour, the morning commute could be slippery
tomorrow across our southeastern zones. Even though slippery
travel conditions are expected, forecast snowfall amounts look
to fall solidly below advisory criteria. Main challenge at this
time is how far north and west the snowfall makes it. Some
sources of guidance suggest snowfall could make it into Columbia
County and the Berkshires, while other sources of guidance
confine snow to Litchfield and Dutchess Counties. Opted to go
with the further south solution, but will continue to monitor
trends as the event draws near.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Thursday morning, cold front continues moving to the south and
east. With the front departing, snow looks to taper to snow
showers by mid morning and should end by late morning. With the
cold front to our southeast, our region will experience strong
cold advection through the day as the troughing and core of the
cold air aloft move towards our region. Despite some partial
clearing, highs will only be in the 10s and 20s (except in the
Adirondacks where single digits are expected). Highs will occur
early in the day, with temperatures continuing to fall through
the day as the core of the cold air works towards our region.
With a tight pressure gradient between the departing low and a
1045 mb high over the midwest, it will also be breezy through
the day.
Thursday night will be another bitterly cold night, with lows
dropping below 0 outside of the Mid Hudson Valley and Litchfield
County, with temperatures in the -10s in the Adirondacks. To
make matters worse, it will remain breezy (especially before
midnight) as the surface high remains to our west. At this
time, wind chill values are expected to drop into the -20s
across portions of the Adirondacks, southern Greens, and eastern
Catskills, and even northern portions of the Berkshires where
wind chill advisories will likely be needed.
Friday and Friday night, the surface high finally makes its way
into our region. This will allow the pressure gradient and
therefore winds to relax. Despite partly to mostly clear skies,
it will remain cold as daytime mixing looks limited and we will
continue to see cold air advection into the region. Highs will
be mainly in the 10s, with single digits in the high terrain.
Friday night, we will be under the surface high. Combination of
clear skies, light to calm winds, and some snowcover should
lead to very favorable radiational cooling conditions. Went
below NBM guidance with Friday night lows, but still may not be
cold enough. Low temperatures will be similar to or even a
couple degrees below Thursday night lows, but wind chills will
not be as harsh with much lighter winds. Will also note that
guidance over the past few days suggested there may be a coastal
storm Friday night. However, with positively tilted trough
aloft and and southern stream disturbance lagging behind the
norther stream trough, any storm that does develop looks to
remain well east of us with no impact on our region except for a
few high clouds late Friday night.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Below normal temperatures will continue through the long term, as
upper level troughing dominates northeastern CONUS. Precipitation
looks to remain limited primarily to Lake Effect and some northern
stream systems, although there is a possibility for some added
southern stream moisture/energy influence for Tuesday-Wednesday.
For Saturday-Saturday night, current model consensus continues to
favor any coastal system tracking too far south/east to have much
influence on our region other than some high clouds. It will be
quite cold, with highs mainly in the teens to lower 20s. Very cold
temperatures possible for Saturday night as high pressure remains
nearby. Areas with a deep snowpack may have temps drop off
precipitously after sunset, with some mins of zero to 10 below
possible across the the southern Adirondacks, and zero to 10 above
elsewhere.
A northern stream clipper looks to approach Sunday-Sunday night,
with along with another arctic cold front. This should bring some
snow showers to the region, with best chances along and north of I-
90, initially with some isentropic lift and QG forcing, and then
with some Lake Enhancement Sunday night. Highs mainly in the 20s,
with lows Sunday night ranging from zero to 10 below across the SW
Adirondacks, and generally single digits and teens elsewhere.
Some lingering Lake Effect snow showers possible Monday, especially
western Mohawk Valley and SW Adirondacks, although may shift into
the eastern Catskills/Schoharie County as well. Otherwise remaining
cold, with highs in the teens and 20s. Lake Effect snow showers
should taper off Monday evening, although some light snow or snow
showers may develop across far western areas ahead of next incoming
system prior to daybreak Tuesday. Lows zero to 10 below across the
southern Adirondacks, and zero to 10 above elsewhere.
For Tuesday-Wednesday, a clipper type system looks to approach from
the west. However, additional southern stream moisture/energy may
also eject from the southwest/southern U.S., with some phasing of
upper level features possible. At the very least, even without much
phasing, some snow showers or a period of light snow will be
possible with the northern stream feature, especially during
Tuesday. Should added southern stream moisture/energy occur, a more
amplified system could result in slower movement, and greater
precipitation amounts for the region. So, chance PoPs are included
for Tuesday into Tuesday night, then gradually decreasing from NW to
SE Wednesday. It will turn even colder in the wake of this system,
with highs Tuesday mainly in the teens and 20s, and lows Tuesday
night in the single digits above zero for southern areas, and below
zero to the north. Wednesday highs mainly in the teens and 20s,
although may be even colder. Wednesday night could be frigid, with
widespread lows below zero possible.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Through 00z Friday....VFR conditions are expected to prevail
through the 00z TAF period for KGFL/KALB. Later tonight between
02z-08z, a cold front will pass over the local area. Moisture
riding up along the front could trigger a few light snow
showers/flurries over KALB/KGFL. Confidence is greater to the
south across KPSF/KPOU. That`s where we anticipate, MVFR-IFR
conditions developing. As far as timing, for the MVFR-IFR
conditions at KPSF/KPOU, we`re expecting between 06z- 09z as the
front pushes through and precipitation develops. Light snow is
possible for KPSF, but the greatest confidence is over KPOU. For
KPOU, lower ceilings coupled with light snow will contribute to
the MVFR-IFR conditions.
Light snow is expected to come to an end mid to late morning on
Thursday with categories improving back to VFR levels across
KPOU/KPSF.
Winds will continue out of the southwest this evening/tonight 5-10
kts before shifting out of the west-northwest later tonight behind
the cold front. Winds could gust as high as 20 kts over KPSF upon
the wind shift.
Outlook...
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Low Operational Impact. Slight Chance of SHSN.
Sunday Night: Low Operational Impact. Slight Chance of SHSN.
Monday: No Operational Impact. NO SIG WX.
&&
.HYDROLOGY...
A weak disturbance may bring light snowfall amounts (1-2") to
portions of Litchfield and Dutchess Counties Thursday morning.
Otherwise, mainly dry weather is expected through at least the
beginning of next week. Despite a mild day today with many
areas rising above freezing, we do not anticipate much snow melt
with temperatures turning cold again tomorrow through the end
of the week. This will support thickening and strengthening
river and lake ice.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...Main/Wasula
NEAR TERM...Main/Wasula
SHORT TERM...Main
LONG TERM...KL
AVIATION...Evbuoma
HYDROLOGY...Main/Speciale
Area Forecast Discussion
National Weather Service Bismarck ND
927 PM CST Wed Jan 19 2022
.UPDATE...
Issued at 925 PM CST Wed Jan 19 2022
There is an emerging signal in both global and high-resolution
deterministic guidance that there could be a loss of ice crystal
production aloft with the precipitation chances late Thursday
night through Friday morning, resulting in freezing drizzle being
a feasible type. There are timing differences on synoptic features
among guidance, but most model sounding locations show at least a
brief period of freezing drizzle potential across multiple model
cores. While confidence on the lack of ice aloft is growing, there
is lower confidence in the amount of forcing that will be
tangent, as the dry layer aloft seems to trail slightly behind the
strongest forcing. Nevertheless, there is enough support in the
925 mb frontogenesis field coupled with weak ascent along the 285
K surface to introduce freezing drizzle chances to the forecast
with this update. The shorter duration and lighter QPF should
limit impacts if this threat materializes.
In the nearer-term, forecast low temperatures were trended toward
the cooler side of NBM guidance based on current trends. But
there will likely be a large degree of variability in overnight
temperatures, as is often the case in strong radiational cooling
regimes.
The HRRR and RAP continue to suggest near-surface saturation
sufficient enough for fog formation. At temperatures this cold,
the fog would be made up of tiny ice crystals, which may not be as
impactful as fog made up of water droplets. Would like to see
evidence of this occurring before adding to the forecast, as this
is not a commonly observed phenomenon. Surface dewpoint
depressions are still in the 5 to 10 degree Fahrenheit range, but
saturation with respect to ice does not require values as low.
UPDATE Issued at 558 PM CST Wed Jan 19 2022
No major changes are needed for this update. The center of surface
high pressure sits near the intersection of the ND/MT and Canadian
borders as of this writing. The main forecast problem of the
night is how cold temperatures will plummet. The surface high
will glide southeastward through the night, exiting the state by
early Thursday morning. Overnight lows may occur earlier in the
night, concurrent with the calm winds at the center of the high
and a prevailing clear sky across the region.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 245 PM CST Wed Jan 19 2022
Wind Chill headlines remain through Thursday morning in areas
outside of the southwest.
A longwave trough continues to impact the Northern Plains with
very cold temperatures in the short term period. With the embedded
vort max passing through the region this afternoon, surface high
pressure will build in behind, becoming centered over the eastern
Dakotas by early Thursday morning. Morning temperatures colder
than -20 F will become common across central and eastern North
Dakota while not as cold in the southwest where winds turn
southerly.
Wind Chill headlines are in effect for areas outside of the
southwest through Thursday morning as wind chills down to -30 F to -45F
are expected. Though winds will be lighter than the previous
night, the colder air mass associated with the passing surface
high will compensate. Some radiation fog will be possible early
Thursday morning as light winds and clear skies will be associated
with the surface high. High- resolution models are inconsistent
about this possibility however, and with the very dry air mass and
uncertain snowpack moisture contribution the location and
probability is questionable. Will leave fog out of the forecast
for now and let future shifts reevaluate.
Thursday, the surface pressure gradient tightens between the
exiting high and developing low to the northwest. Breezy southerly
winds are expected as well as warmer temperatures west and
central. Highs in the upper 20s west, 5 to 15 central, and around
zero in the James River Valley are forecast.
.LONG TERM...(Thursday night through Wednesday)
Issued at 245 PM CST Wed Jan 19 2022
The long term forecast period will be highlighted by a transition
to northwest flow aloft, with periodic chances for snow as well as
warmer temperatures to the west and generally colder to the east.
As a temperature gradient hangs around the region through the
period, varying amplitude shortwaves will bring temperatures above
and below normal day to day. The first relatively deeper shortwave
will impact the area Thursday night and Friday, bringing a shot
of light snow and then warmer temperatures ahead of a cold front
on Friday. For the northwest the warmest temperatures may be
earlier in the morning before the cold front arrives. Fairly major
differences among guidance exists in how the cold air exits to
the east on Saturday, with NBM probabilities showing large spreads
in potential highs over the central and east. The spread is much
smaller in the southwest where highs in the low 30s are forecast.
Sunday should deliver warmer than normal temperatures for the west
and central ahead of the next cold front. Light snow is possible
on Saturday, but accumulating snow looks more likely Sunday night
and Monday over the north and east as a greater amplitude wave
arrives. NBM/ECMWF/GEFS ensembles show snow accumulation
probabilities topping out below warning criteria, which seems
reasonable based on the pattern.
The beginning of next week features more of the same temperature
uncertainty as 500mb model height clusters show greatest
differences in east-west placement of upstream ridging and
downstream troughing. The greatest impacts of this associated
baroclinic uncertainty are in the central and eastern portions of
the state where the difference between the NBM`s 25th and 75th
high temperature percentiles span 20 to 30 degrees. In the
southwest the spread again is much lower, and thus warmer than
normal temperatures have a greater predictability in this area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 925 PM CST Wed Jan 19 2022
VFR conditions are likely through the forecast. There is a low
chance of fog/ice crystals developing across central and
northwest North Dakota overnight. Winds will diminish this
evening, becoming southerly around 10-15 kts Thursday afternoon.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory until noon CST /11 AM MST/ Thursday for
NDZ017>020-034-042-045.
Wind Chill Warning until noon CST Thursday for NDZ001>005-
009>013-021>023-025-035>037-046>048-050-051.
&&
$$
UPDATE...Hollan
SHORT TERM...AE
LONG TERM...AE
AVIATION...Hollan
Area Forecast Discussion
National Weather Service Denver/Boulder CO
813 PM MST Wed Jan 19 2022
.UPDATE...
Issued at 756 PM MST Wed Jan 19 2022
Overall, only minor adjustments planned for the grids this
evening. Some lingering snow showers/flurries expected to
diminish by late evening, with partial clearing from north to
south after midnight. Timing of this is all reflected in the
current RAP analysis. The Winter Weather Advisory has been allow
to expire this evening, however continue to exercise caution
tonight as roads will be icy and slick, especially over bridge and
overpasses, side roads and sidewalks.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 314 PM MST Wed Jan 19 2022
Freezing drizzle has largely transitioned to flurries and light
snow across the region, as upper sections of the moist layer cool
below -10 C. A few light snow accumulations around an inch have
been noted across portions of Larimer and Weld Counties along the
I-25 corridor. The freezing drizzle has had no issues accumulating
on surfaces, particularly untreated roads and sidewalks, so
conditions are quite slick. Cloud cover should remain abundant
into this evening, with ground temperatures below freezing, so
plan on conditions remaining treacherous in spots even during the
evening commute, despite the transition away from freezing
drizzle.
Snow accumulations this afternoon should be extremely light,
remaining under a half inch for almost all areas. A few spots
along the foothills and Palmer Divide could see a touch more, but
under an inch most likely. Any lingering showers should exit our
CWA shortly before midnight. Debated dropping a portion of the
current winter headlines, but given the observed icy conditions
which are expected to persist into the evening rush hour despite
much additional precipitation, will keep them up for now.
Moist surface conditions and weak winds may lead to some patchy
fog tonight into Thursday morning, mainly for low-lying areas of
the plains, with chances dropping closer to the urban corridor. It
will be a chilly night with gradual clearing and lows largely in
the teens for the flatlands, and locally single digits for the
lower river valleys and the high mountain valleys.
Slightly milder Thursday with highs in the 30`s and low 40`s east
of the mountains. Ample clearing is likely by the afternoon,
particularly in the plains, with a few increasing clouds late in
the day in the mountains ahead of our next system.
.LONG TERM...(Thursday night through Wednesday)
Issued at 314 PM MST Wed Jan 19 2022
Warm advection cloudiness will spread back over the mountains
Thursday night, early enough to help keep temperatures up, and
then off of the Front Range by morning. This will be followed by
the shearing trough dropping south Friday, dropping a cold front
through in the morning. It still looks like the best lift will be
over the mountains and further west, but there will likely be
enough for a little snow as the moisture band moves over during
the day. The main feature will be the upslope enhancement west and
south of Denver in the late afternoon and evening. This could wind
up being like the event last week where there wasn`t much
elsewhere, but there was a pocket of significant snowfall from the
lingering showers in the upslope area southwest of Denver. This
could also be poorly timed, around rush hour on a Friday
afternoon.
We`ll have clearing by Saturday morning as we get drier northwest
flow starting. There will be warming aloft with increasing winds,
but on Saturday this will likely only surface over the mountain
ridges and foothills. By Sunday the warmer air and breezes will be
spreading east to at least the I-25 corridor and perhaps all
across the plains.
There`s still a lot of variety in model solutions for early next
week. There will be a couple of shortwaves in northwest flow, and
with the stronger flow there`s less chance of the energy shearing
out towards the southwest like systems have tended to do this
week. But there are big differences in timing and which wave will
be stronger. There are lots of solutions showing snow on Tuesday,
but for different reasons. The 12z GFS was gung ho with a long
period of overrunning precipitation as a strong cold front comes
early (Monday), but a shearing trough hold west of us through
Tuesday. It would be hard to get that just right so that would
happen, but there are similar setups in some model runs. Others
have a couple of waves that move through more quickly in the
northwest flow, still enough for a more transient threat of snow
along with colder temperatures. We`ll stick with our model blend
for now, though I was tempted to increase PoPs. Knowing just when
is the hard part. For now, we`ll have colder temperatures with the
PoPs mainly on Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 756 PM MST Wed Jan 19 2022
IFR ceilings 005-010ft AGL will continue this evening, but with
vsbys improving 3-6+sm most areas. Areas of light snow/flurries
will linger at the terminals through 05z, but no additional
accumulation expected. Improving trend overnight but could still
experience patchy fog, so will continue with vcfg after 10z.
East/southeast winds this evening will transition to a light
southerly drainage overnight.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Cooper
SHORT TERM...Rodriguez
LONG TERM...Gimmestad
AVIATION...Rodriquez/Cooper
Area Forecast Discussion
National Weather Service Marquette MI
640 PM EST Wed Jan 19 2022
.SHORT TERM...(This Evening and Tonight)
Issued at 249 PM EST WED JAN 19 2022
RAP analysis and GOES imagery shows a shortwave and associated 1000
mb sfc low over western Quebec quickly pulling away to the east.
Tight pres gradient behind the sfc low and ahead of the Arctic high
of 1044 mb building into the Northern/Western Plains still
generating strong NW wind gusts of 30-40 mph over the east half of
the cwa and generally 20-30 mph gusts over the west half into this
afternoon. Temps falling into the single digits abv zero this
afternoon combined with the strong nw winds have also lowered
wind chills into the zero to -15F range, coldest west half.
The LES and strong winds are still contributing to considerable
blowing snow over the east half as noted on area webcams so decided
to extend the winter weather advisory through this evening for the
eastern counties of the U.P. Winds and light LES also contributing
to some blowing snow over the west so extended advisories there
until 21Z, although weakening winds have already allowed for some
improvement in vsbys this afternoon as BLSN has diminished somewhat.
Tonight, winds will start to relax this evening, but blustery
conditions are still expected. LES will continue in the NW wind snow
belts, but accums will remain modest. With cold, arctic air
overhead, DGZ will remain near the sfc across the west, which will
keep growth and accum potential low. Across the east, a longer fetch
will allow for better modification, so a little better accumulation
potential will remain there. Additional snow amounts will remain 1
to 3 inches across the west and 2 to 4 inches across the east into
tonight. Temperatures will be cold tonight, falling into the single
digits blo zero for most locations. Lake effect clouds and air
modification will keep temps in the single digits abv zero across
the east. A few locations along Wisconsin stateline could see some
clearing, which will allow temps to fall closer to -10 blo zero.
Wind chills will generally be in the teens blo zero tonight, though
a few locations in Gogebic County could fall closer to -20 to -25
late tonight with expected clearing. Not issuing a Wind Chill
Advisory at this time, but it will be something to monitor for the
evening and overnight shifts.
.LONG TERM...(Thursday through Wednesday)
Issued at 218 PM EST WED JAN 19 2022
Upper level troughing over the upper Great Lakes 12z Thu will be
replaced by shortwave ridging on Fri with a shortwave trough in the
northern plains 00z Sat which moves into the upper Great Lakes Fri
night into Sat. Strong 850-500 mb q-vector convergence and deeper
moisture move in Fri night and both move out Sat afternoon.
In the extended, the GFS and ECMWF show a deep 500 mb trough across
the ern U.S. 12z Sun. Numerous shortwaves are embedded in this
trough with little change in the upper pattern for this forecast
period. This will continue the below normal temperatures for this
period along with prolonged lake effect snow showers.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 640 PM EST WED JAN 19 2022
Under a cold airmass and nw flow, lake effect snow showers will
continue to stream off of Lake Superior. At IWD, expect -shsn and
conditions varying btwn MVFR and IFR, but likely becoming prevailing
IFR during the night. As low-level winds begin to back Thu, -shsn
will shift n of IWD with improvement to VFR early in the aftn. At
CMX, -shsn will continue thru the fcst period with IFR likely to
prevail, though frequent LIFR will probably occur for much of
tonight. At SAW, there may be some flurries at times thru tonight,
but no vis restriction expected. Otherwise, cigs will fluctuate
around 3000ft, so expect varying conditions btwn high MVFR and VFR.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 218 PM EST WED JAN 19 2022
Gale event will continue to wind down this afternoon and will end
this evening. Next period of strong winds will be southwest winds to
30 knots Thu night into Fri night and there could be some gale force
gusts to 35 knots with that. With the wind, freezing spray will
continue to be a problem for this forecast period.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory until midnight EST tonight for MIZ006-
007-085.
Lake Superior...
Heavy Freezing Spray Warning until 1 PM EST Thursday for
LSZ243>251-264>267.
Heavy Freezing Spray Warning until 7 AM EST /6 AM CST/ Thursday
for LSZ162-240>242-263.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...07
AVIATION...Rolfson
MARINE...07
Area Forecast Discussion
National Weather Service Pocatello ID
903 PM MST Wed Jan 19 2022
.UPDATE...We did an update to account for the potential of light
snow/flurries under the stratus deck tonight and tomorrow morning.
We also did expand the freezing fog potential as well into some
more sheltered valleys outside of the Snake Plain. We will let the
overnight shift do any updates in terms of snowfall tomorrow and
tomorrow night. Keyes
&&
.PREV DISCUSSION... /issued 200 PM MST Wed Jan 19 2022/
SHORT TERM...Tonight through Friday night. Weak shortwave
dropping along the Divide this afternoon is still proving to be
not enough to break up the broad area of stratus embedded in lower
elevations of East Idaho. There may be just enough moisture
present in the mid-cloud deck working into the southern highlands
to produce a trace of snowfall in some areas, but confidence is
low for anything other than a flurry or two. Expect one more night
of inversions before next system works through the region tomorrow
into early Friday. Light snow is expected to begin in the central
mountains and along the Divide during the morning hours. Frontal
boundary rapidly drops southeast through East Idaho during the
afternoon and evening, and the main focus for snowfall occurs
along/just ahead of the front. Today is no exception. High-res
guidance solutions remain absolutely consistent with timing the
strongest band of snowfall: afternoon in the central mountains,
evening in the Snake Plain, and evening/overnight for the
eastern/southeast highlands. The guidance trend has been to
creep the expected QPF amounts upwards very slightly with each
run, pushing generally an additional quarter to half-inch of
snowfall each time depending on location. This puts the latest
storm total accumulations towards Winter Weather Advisory
thresholds in some of the higher elevation zones from Island Park
to Soda Springs. Totals in the Snake Plain remain below general
Advisory thresholds, but if the timing of the band narrows to
mainly impact the evening commute, this may be enough to tip the
scale toward a headline. Will hold on issuance for now, and
maintain awareness via social media and continuation of the
Special Weather Statement issued this morning. Winds briefly
become breezy behind the front Thursday night, but below
widespread concerns for blowing snow. A few lingering snow showers
are expected to remain into Friday mainly across the southern and
eastern highlands, but otherwise high pressure is forecast to
return. Models support low level moisture remaining entrenched in
the lower elevations, so there is a high confidence in seeing the
return of stratus and maybe fog Friday night. DMH
LONG TERM...SATURDAY THROUGH NEXT WEDNESDAY...
A nearly stationary ridge of high pressure off the Pacific coast
will remain the dominant synoptic wx enforcer across the region this
weekend into early next week, supporting dry conditions and light
winds with an active storm track well north of SE Idaho, but also a
return of temp inversions and a more stagnant airmass with attendant
risks for fog/low stratus each overnight into the mornings. The
ridge may tend to trend/retrograde a bit further west with time as a
shortwave trough rides the flow between the ridge and departing
trough (by this time a longwave trough feature blanketing the
central/ern US). Confidence remains low on the exact track of the
shortwave and how significantly it "cuts" into the ern side of the
ridge Mon into Tue...most models continue to keep precip largely
east of the CWA while the 12z deterministic GFS now brings snow
across all of SE Idaho, illustrating this uncertainty. This type of
(at least somewhat) wetter scenario has about 20-30% support in
cluster analysis right now, but with none of the clusters really
producing any widespread precip in our CWA. For now, we hold with
the NBM blend which continues to limit PoPs to the Island Park
region and immediate WY border. High temps remain stagnant in the
mid-20s to lower 30s each day, generally near or just slightly below
climo norms for mid-January. - KSmith
AVIATION...
IFR cigs are likely to continue to hold on today although improving
back toward the MVFR threshold, with all terminals then trending
back into lowering cigs/vsbys after sunset as the near-sfc airmass
continues to remain quite moist. HRRR/NBM guidance offers a slightly
less saturated and more "messy" picture overnight tonight into Thu
AM with regard to fog/stratus coverage compared to the past 2
nights, which if anything just lowers our confidence in coverage of
potential fog (and last night did not verify as dense as HRRR
guidance suggested). For now, trended into a 4-6 SM BR regime with
IFR low stratus dominating, and will monitor trends on fog
development. Except for KSUN which should continue to follow it`s
normal diurnal wind cycle, winds at the rest of the TAF terminals
are so light in the guidance that confidence in anything beyond
variable is also low, and indeed the guidance is split on whether NE
down-valley flow or SW up-valley flow will dominate in the Snake
Plain. For now, went with light up-valley flow, but all speeds
should remain below 7kts. Snow with our next system arrives Thu
afternoon, and we kick this off at 22z for now in the longer KSUN
TAF period (pending elsewhere in the next TAF package). We may need
to consider at least VCSH in advance of the main show at the rest of
the terminals, perhaps as early as 16-17z, as mid-level clouds
moving in atop the continued low stratus may support a "seeder-
feeder" effect and some light snowfall. - KSmith
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$