Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/18/23
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
946 PM CST Fri Feb 17 2023
.UPDATE...
Issued at 946 PM CST Fri Feb 17 2023
Once again only minor changes were made with this update, mainly
blending observed trends and recent guidance into the overnight
forecast. HRRR, GLAMP, and NBM guidance has trended to a rather
dispersive signal for any fog, and probabilities of formation have
fallen to around 20% as of this writing, so we once again held off
introducing it to the forecast. Regional 00 UTC RAOBs showed less
dry air aloft and stronger winds above the ground than typically
associated with radiation fog profiles, too. Radar imagery shows
some echoes developing in northeastern MT as midlevel warm air
advection begins, but our confidence in these being manifest as
any precipitation at the ground is too low to add any chance of
that to the forecast at this time, either.
UPDATE Issued at 552 PM CST Fri Feb 17 2023
Only minor changes were made with this update cycle. Mixing has
begun to subside with the approach of sunset and winds are thus
diminishing as expected. The Williston/Williams County radar is
showing a few light returns in that area so we have continued a
mention of flurries over northwest/north central ND this evening
as a weak impulse crosses the area. Otherwise, recent HRRR runs
have suggested fog could develop overnight in south central ND,
but GLAMP and NBM probabilities of its development are only in
the 40% range, so we haven`t added it to the forecast yet.
&&
.SHORT TERM...(This Evening through Saturday night)
Issued at 343 PM CST Fri Feb 17 2023
Mild conditions are expected again on Saturday with some very
light snow possible Saturday night.
In the upper levels this afternoon, a broad longwave trough was
located across southern Canada with an open shortwave crossing
southern Saskatchewan and Manitoba. The associated surface
pressure response has created breezy to windy conditions this
afternoon across western and central North Dakota, with a wind
shift provided by a kink in the pressure field as winds shift to
the northwest while the trough passes. The weak cold air advection
associated with this trough will be overtaken by another warm air
push on Saturday with 850mb temperatures reaching or exceeding 0
C in southern North Dakota. High temperatures will be mild again
in the 30s to lower 40s, but with lighter winds. Light snow will
be possible Saturday night as the low associated with the earlier
warm air push crosses northern North Dakota but ensemble
probabilities of greater than one inch of accumulation are low.
.LONG TERM...(Sunday through Friday)
Issued at 343 PM CST Fri Feb 17 2023
A pattern change towards much colder temperatures with chances for
snow next week highlights the long term forecast period.
Modestly cooler temperatures are expected Sunday behind the
previous low. Then a clipper moves across the state Sunday night
through Monday with accumulating snow more likely across the
north and east. Greater than 50% probabilities of one inch or more
of snow stretch from northwest North Dakota through the northern
James River Valley, maximizing over the Turtle Mountains and north
central where higher probabilities of greater than two inches
also exist. With this clipper comes increased northwest winds
during the day Monday, especially for the western and southern
areas of the surface low. The overlap of 850mb winds and cold air
advection may allow for surface winds to approach advisory
criteria, and even more of an impact, combine with the falling
snow to potentially create blowing snow where greater winds and
snow coincide.
Tuesday begins a period of two sets of snowfall chances. A
transition to zonal flow brings a speed max across a tight
baroclinic zone on Tuesday, draped from Montana across the
Dakotas. There remains moderate model uncertainty regarding the
north- south placement of this baroclinic zone and the subsequent
axis of accumulating snow with a washed out probability field from
the NBM. Then through midweek a more significant western CONUS
trough develops with a Colorado low ejecting through the region
Wednesday- Thursday. Again the northern extent of potentially
heavy snowfall is in question, especially with a surface high
building through the Dakotas as it passes. The ensemble signal for
heavy snow is more apparent with this low, where greater than 50
percent probabilities of at least 6 inches of snow is across
South Dakota through southern Minnesota. That isn`t to say there
isn`t room in the ensemble field for heavy snow to shift north
into North Dakota but as described by the previous shift, the
probabilities favor south of the border or especially south of the
North Dakota I-94 corridor.
The surface high previously mentioned will also be associated with
an Arctic airmass impacting the region Tuesday through Friday. By
Wednesday highs should struggle to exceed zero degrees and
widespread wind chill hazards look possible each night Wednesday
through Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 946 PM CST Fri Feb 17 2023
VFR conditions will likely prevail through most of the 00 UTC TAF
cycle across most of western and central ND. There`s a low, 20%
chance of IFR fog or stratus developing tonight and early Saturday
over central ND, but those odds have decreased and so we continue
to refrain from including any mention of that in the TAFs. Winds
will be light overnight and tend south to southwest mainly around
10 kt on Saturday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...CJS
SHORT TERM...AE
LONG TERM...AE
AVIATION...CJS
Area Forecast Discussion
National Weather Service Burlington VT
931 PM EST Fri Feb 17 2023
.SYNOPSIS...
Light snow tapers off early this evening giving way to a
seasonably cold and mostly sunny Saturday. Above normal
temperatures return for Sunday into early next week before a
cool down mid week. The weather pattern is generally quiet with
a couple of weak systems bringing light snow and rain showers
before a potential storm system arrives on Thursday.
&&
.NEAR TERM /THROUGH SATURDAY NIGHT/...
As of 926 PM EST Friday...Made some additional minor tweaks to
pops and temp grids thru midnight. This included continuing chc
pops on the east side of the CPV associated with northerly
flow, caa, and some enhanced moisture from Lake Champlain. Radar
shows several weak streamers that have been impacting the BTV
area with vis btwn 3-5sm and just minor snow accumulations. As
ridge axis builds into cwa, winds aloft become more westerly and
better moisture wl dissipate so anticipate areal coverage to
decrease aft midnight. Any lingering snowfall accumulations wl
be a dusting to 0.5" at most. Otherwise, did note the new 00z
HRRR is dropping parts of the SLV temps to near 0F, so have made
a minor lowering of temps acrs this region. Rest of the fcst in
good shape this evening.
Previous discussion below:
Forecast has panned out really well for a multi-faceted storm
system, one that has our CWA straddling both the cold and warm
sectors. The main message for early this afternoon is that the
freezing rain threat is now over, with pretty much the entire
area below freezing and changed over to snow. Noted that
Springfield in southeast VT is still at 33F as of this writing,
but webcams in Mendon show even the southern Greens changed
over to snow. We opted to let the Winter Weather Advisories
expire for all our zones with only an additional inch of snow
accumulation expected. The clearing line now almost all the way
to the St Lawrence valley per the visible satellite imagery.
For the remainder of this afternoon, snow showers continue
especially for the eastern Champlain valley, BTV and the western
slopes of the Greens due to blocked flow, with the Froude number
remaining in subcritical threshold below 0.5 per the NAM
guidance. The additional snow is great news as it provides traction on
surfaces that might have frozen over or coated with a thin
layer of ice underneath. Winds will also be gusting 25-30 mph
out of the northwest as low level lapse rates steepen with the
air aloft cooling. It certainly feels a lot more like winter out
there with wind chills falling into the single digits and teens
after we had a tease of spring over the last few days.
Any lingering mountain snow showers will wind down overnight tonight
as ridging and drier air move into the region. Clearing skies and
subsiding winds along with a bit of fresh snow will allow
temperatures to drop into the single digits in many locations, with
just the Champlain and lower Connecticut Valleys remaining at or
above 10F. H5 ridging moves overhead tomorrow, with its axis
shifting to our east by mid/late afternoon. Overall expect it
should be a rather nice day with plentiful sunshine, though it
could be a bit breezy with increasing south/southwest flow
around the back of the high, especially in the St Lawrence and
Champlain Valleys due to channeling or Bernoulli effect. Also,
the clouds could return for the St Lawrence valley in the
afternoon but it stays mostly sunny elsewhere. Otherwise, we
will see partly to mostly sunny skies and highs in the upper 20s
to mid 30s, which is actually right about where we should be
for this time of the year.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 300 PM EST Friday...Quiet weather for Sunday as low level
ridging slowly progresses east and offshore. As such, partly
sunny skies and nil PoPs look good for now. Southerly flow will
set up, boosting temperatures into the upper 30s/lower 40s area
wide under partly sunny skies. A broad increase in clouds is
expected Sunday night ahead of our next frontal system, but
conditions should remain dry. Lows holding mild under continued
south flow - mainly 30s.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 300 PM EST Friday...Scattered/numerous rain/snow showers
then on tap for Monday/Monday evening with passage of the
aforementioned front, with frozen precip favored in elevated
terrain during the day, and area wide Monday evening before
tapering off under modest cold thermal advection. Any
accumulations should be light. A few additional/scattered rain
snow showers then possible again on Tue/Wed with the passage of
another weak system, the Euro being the most bullish among this
morning`s deterministic output. Temperatures remain seasonably
mild through this mid week time frame with highs in the mid 30s
to lower 40s.
Thereafter, a larger system tracking east-northeast from the central
states will likely affect the area later next week with the
potential for a variety of precipitation types. This morning`s Euro
is the coldest with mainly snow, with the GFS/GEM camps on the
milder side showing snow transitioning to a mix. Time will tell how
this pans out. For now have leaned toward blended national guidance,
which leans a bit toward the colder Euro idea. Behind this system,
indications suggest a period of colder weather by next weekend.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Through 18Z Saturday...Mix of MVFR and VFR conditions will trend
VFR through 12Z as low clouds gradually scatter. Wrap around
snow showers from departing low pressure system should diminish
as moisture thins over the next few hours with improving
visibilities at SLK and MPV, where occasional IFR visibilities
are still possible through 04Z. As a surface ridge continues to
build in, northwest winds in the 7 to 14 kt range will diminish
overnight. Winds then become southwesterly mainly 5 to 10 kts
after 12z, and on the breezy side at MSS and SLK with 20-25 kt
gusts after 15z. The favorable fetch of moisture off Lake
Ontario could induce enough low level moisture for MVFR ceilings
after 18Z, but for now have indicated SCT deck at MSS until
confidence increases.
Outlook...
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Washingtons Birthday: Mainly VFR, with areas MVFR possible.
Chance SHRA, Chance SHSN.
Monday Night: Mainly VFR, with areas MVFR possible. Chance SHSN.
Tuesday: VFR. Chance SHSN, Slight chance SHRA.
Tuesday Night: Mainly VFR, with local IFR possible. Slight chance
SHSN.
Wednesday: VFR. Slight chance SHSN, Slight chance SHRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Chai
NEAR TERM...Chai/Taber
SHORT TERM...JMG
LONG TERM...JMG
AVIATION...Chai/Kutikoff
Area Forecast Discussion
National Weather Service Grand Forks ND
950 PM CST Fri Feb 17 2023
.UPDATE...
Issued at 949 PM CST Fri Feb 17 2023
Clouds and not much else have been the main impacts from the
shortwave that is currently pushing into northern ND. Not much in
the way of flurries seen in obs or on web cams, and although
there are a few weak radar returns in the far west it seems not
much is reaching the ground. Temps have been staying in the teens
to 20s, and continue to think readings will stay above zero
overnight.
UPDATE Issued at 547 PM CST Fri Feb 17 2023
Adjusted cloud cover a bit for current satellite trends, but
overall forecast seems on track. Still think we will get some
flurries later tonight as a weak clipper pushes into the area.
Agree with previous shift that impacts seem minimal.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 228 PM CST Fri Feb 17 2023
Overview:
Impacts in the short term are minimal, with the introduction of two
systems out of a zonal flow. First moves through tonight, with the
second Saturday night into Sunday afternoon. Each brings the chance
for some snow. Blowing/drifting snow will be possible, but looks to
be on the little to no impact side.
Today - Saturday morning:
System tracks through southern Canada this afternoon and overnight
bringing stronger winds to eastern ND and NW MN. Daytime mixing and
temperatures in the 20s to 30s have allowed for some areas to gust
up to 30mph on a isolated basis. There is little to no impacts
associated with blowing/drifting snow as the snowpack is fairly
crusted over. As we loose daytime heating winds will slowly subside,
but chances for some flurries or a light snow shower will increase
along and north of Highway 200. Chances are low (20-30%), but still
noticeable in CAMS and HRRR guidance. Thus, added some flurries
Highway 200 northward from 00z through 07z as the system moves
through. Little to no impacts are expected from the flurries or
breezy conditions.
Saturday afternoon - Sunday:
Temperatures warm into the 20s to lower 30s Saturday afternoon, with
clouds lingering around the area ahead of another system moving in
by Saturday night into Sunday. Another clipper translates across the
northern plains bringing some breezy north winds and light
accumulating snow for areas in eastern ND and NW MN. Winds have the
potential to gust up to 35mph during the daylight hours Sunday. Snow
accumulations look to remain light, with up to an inch possible for
areas along and north of Highway 2. Best chances to see up to an
inch will be toward Lake of the Woods. Blowing/drifting snow should
be minor in impacts, with some light pillow drifts possible and
slight reductions to visibility from the newly falling snow. This
looks to be a quick window of breezy winds as by the evening
guidance has the winds subsiding ahead of another system moving in
by Monday.
.LONG TERM...(Sunday through Friday)
Issued at 228 PM CST Fri Feb 17 2023
Key Messages:
-Light snow and gusty winds will introduce some wintry impacts for
much of the region late Sunday into Monday, especially impacting the
Monday morning commute.
-Much colder air arrives Tuesday - Friday.
-While high uncertainty remains, a potentially impactful winter
weather system is expected to affect the northern Plains across the
middle of the week.
Sunday night into Monday System...
The next successive shortwave is progged to impact the region late
Sunday into Monday. This system looks to pack a little more of a
punch than the Saturday night system. Ensemble guidance is beginning
to gain more certainty in the surface low position. Over 90% of
ensemble guidance is indicating a surface low developing over
eastern Montana and traveling within the mean flow into eastern
North Dakota and northwestern/west central Minnesota. As a result,
there is increasing confidence in a swath of light snow extending
across much of the forecast area. Latest NBM probabilities of
exceeding 1" of new snow with this system are in the 40-60% range
from the I-94/Highway corridor southward, with 70-90% probabilities
from I-94 northward toward the international border. There remains a
low, 10-15%, chance for probabilities of exceeding 4". As a result,
looking at a generalized area of 1-3 inches of new snowfall. Gusty
winds out of the north-northwest are also expected to accompany this
system. While light, with a new, blowable snowpack likely to fall,
blowing and drifting snow will be possible throughout the day on
Monday. Otherwise, with winds shifting to a northwesterly direction,
stout CAA is expected to work into the region beginning Monday night
and lasting through the remainder of the week. Highs in the single
digits on either side of zero and lows well below zero will likely
result in at least advisory criteria wind chills throughout the
week ahead. Regardless, there will be increasing chances for snow
from Wednesday into Thursday.
Wednesday into Thursday System...
After a brief reprieve on Tuesday, an upper level pattern shift will
begin to work into the northern Plains. Cluster analysis continues
to indicate a deepening upper low building in over the western
CONUS. The degree of deepening will have a large bearing on how the
flow pattern evolves over the northern Plains. A stronger upper low
would yield more southwesterly flow aloft, while a weaker upper low
would yield more zonal flow aloft. While subtle, these differences
will have a strong determination on eventual storm track and
evolution. Latest ensemble guidance hints at an increasing
likelihood of the surface low tracking across the central Plains,
while the upper low tracks to the north of it. This upper low track
looks to introduce wintry impacts to the region as a result. Latest
NBM probabilities of exceeding 1" are in the 25-50% range from the
international border toward the Highway 200 corridor, and the 60-90%
range from the Highway 200 corridor southward (increasing
probabilities further southward). Furthermore, NBM probabilities
exceeding 4" are in the 50-70% range from the I-94 corridor
southward, with still 30-40% probabilities of exceeding 8", lending
credence to the idea that there may be higher snowfall totals
possible with this system. This does look to be a rather progressive
system, but given the strong nature of it, could yield some higher
impacts across the region. As a result, will continue to monitor
latest trends in ensemble guidance as details become clearer.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 547 PM CST Fri Feb 17 2023
Currently VFR with diminishing winds. Several of the model
solutions bring quite low IFR ceilings down into the Red River
Valley and western MN, but given upstream obs this seems a bit
overdone. Do have ceilings going down to MVFR later tonight into
tomorrow morning, but will keep IFR out for now. Winds will
continue to drop, eventually shifting to a more southerly
direction and picking up to near 10 kts by the end of the period.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...JR
SHORT TERM...Spender
LONG TERM...Rick
AVIATION...JR
Area Forecast Discussion UPDATED
National Weather Service Hanford CA
435 PM PST Fri Feb 17 2023
.Update to Air Quality Issues Section...
.SYNOPSIS...Dry conditions will continue across the area through
the holiday weekend. Above normal temperatures will return to the
area as well. Chances for rain and snow will come in on Tuesday
night and Wednesday with much cooler temperatures expected across
the area by Wednesday. Unsettled weather with cooler than normal
temperatures and showery conditions will prevail next Thursday and
Friday.
&&
.DISCUSSION...Central CA is currently under a southerly flow
between an upper ridge over the Great Basin and an upper low off
the central CA coast near 130W which is currently dropping
southward. Satellite imagery is showing high clouds being pulled
up northward into our area, but dry air in the lower and mid
layers are maintaining dry conditions across our area.
SREF is indicating that the offshore low will continue dropping
southward to off the Socal coast tonight and further south to off
the Baja coast by Saturday. The result of this will be continued
dry weather across our area along with more high clouds. While MOS
guidance is indicating that minimum temperatures in the San
Joaquin Valley tonight will approach the freezing mark, NBM
probabilistic guidance is indicating the chances of sub-freezing
temperatures in the outlying areas of the San Joaquin Valley on
Saturday morning are at 40 percent or less so have decided not to
issue a Freeze highlight. Have also noticed the DESI HRRR is
showing a continuation of the upper level moisture surge across
our area tonight suggesting more high clouds streaming over our
area. This will keep likely keep minimum temperatures up by a few
degrees from MOS guidance.
The SREF is showing the offshore low slowly approaching the Baja
coast between Saturday night and Monday night with a ridge axis
extending inland into central CA. This will result min a warming
trend across our area through the holiday weekend with the latest
NBM probabilistic guidance indicating the most of the San Joaquin
Valley will have between a 35 and 55 percent chance of
temperatures exceeding 70 DEG F on Presidents Day.
The offshore low is progged to move inland into northwestern
Mexico by next Tuesday as an anomalously cold upper trough drops
south ward out of the Gulf of AK and into the PAC NW. This trough
will drop further southward into central CA on Tuesday night and
Wednesday and bring much cooler temperatures to our area along
with chances of precipitation. NBM is indicating that high
temperatures on Wednesday in the San Joaquin Valley will generally
be in the lower 50s just two days after approaching the 70 DEG F
mark. QPF progs are showing the Sierra Nevada will pick up between
half an inch and an inch of liquid precipitation between Tuesday
night and Wednesday night while the adjacent foothills pick up
between a quarter inch and a half inch during the same time frame.
Rain shadowing will limit precipitation in the San Joaquin Valley
to generally a tenth of an inch or less at most locations. Snow
levels are progged to plummet from 5000 to 6000 feet at the onset
of the event on Tuesday night to below 1000 feet by late Wednesday
night.
Another cold trough is progged to drop southward over CA on
Thursday and Friday which will maintain below normal temperatures
and chances of precipitation across the area through the end of
next week. The biggest concern for this period will be with low
snow levels is that travel will be impacted over the Sierra
foothills and over the major passes in the Tehachapi Mountains
between Wednesday and Friday of next week. QPF projections are
suggesting that between 3 and 6 inches of new snow could
accumulate in Mariposa, Oakhurst and Three Rivers and
accumulating snow could also impact the Tehachapi, Lebec and
Frazier Park areas. Probabilistic guidance is even indicating a
40 to 50 percent chance of subfreezing minimum temperatures across
much of the San Joaquin Valley next Thursday and Friday mornings
while precipitation remains very much possible. As a result,
freezing precipitation and/or light snow cannot be ruled out for
the San Joaquin Valley next Thursday and Friday mornings. However,
a lot of spread still exists amongst the medium range ensemble
members concerning the exact track of the second trough next week
which reduces forecaster confidence for the latter portion of next
week.
&&
.AVIATION...VFR conditions will prevail across the central
California interior for the next 24 hours.
&&
.AIR QUALITY ISSUES...
ISSUED: 02/17/2023 14:15
EXPIRES: 02/18/2023 23:59
On Saturday February 18 2023, Fireplace/Wood Stove Burning Status
is: No Burning Unless Registered in Fresno, Kern, Kings, and Madera
Counties. Burning Discouraged in Merced and Tulare Counties, and
Kern (Greater Frazier Park Area) and Sequoia National Park and
Forest.
&&
.CERTAINTY...
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is low.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
and/or to provide feedback.
&&
.HNX WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
public/aviation/fire wx...DAS
pio/idss...JEB
weather.gov/hanford
Area Forecast Discussion
National Weather Service Pocatello ID
120 PM MST Fri Feb 17 2023
.SHORT TERM...Tonight through Sunday. Early afternoon satellite
imagery was showing a broad upper ridge across the NE Pacific with a
well defined short-wave disturbance riding over the ridge into SW
Alaska. Numerical models drive this disturbance SE through British
Columbia tonight and into/through the NRN Rockies Saturday afternoon
through Sunday afternoon. Current forecast snowfall accumulations
for Saturday afternoon through Sunday afternoon fall between the
75th and 90th percentile of ensemble members for that time frame and
are satisfying Winter Weather Advisory criteria across a broad swath
of the ERN mountains (5-10 inches) and eastern foothills from
Pocatello through St Anthony (3-5 inches) in a moderately moist
upslope NW flow. Light snowfall is expected to linger into Sunday
afternoon and evening as we continue to see moisture streaming over
the ridge ahead of the next impactful storm system set to arrive
Monday night/Tuesday. You can get all the specifics on that system
in the Long Term section below. Temperatures should moderate tonight
as clouds overspread the region ahead of the first disturbance and
remain seasonably cool through Sunday. Huston
.LONG TERM...Sunday night through next Friday. We continue to expect
a significant, long-duration winter storm system to impact SE Idaho
for much of the upcoming week, with the greatest impacts currently
focused in the Mon afternoon through Wed eve timeframe. This complex
event will begin as an atmospheric river-supported NW stream of
moisture feeding across the nrn Rockies Mon and Tue, transitioning
into some sort of closed mid-level low riding down the back/west
side of a Canadian parent low and setting up shop near our area Wed,
transitioning into the overall associated trough elongating SW
toward CA with potentially multiple embedded low pressure centers or
at least a split-trough pattern at play Thu and Fri...(so the flavor
you should be taking from all this is "long duration shenanigans"
and "lots of moving parts"). The 12z suite of long-range
deterministic models don`t currently bring the overall trough axis
through SE Idaho until sometime Fri or Fri night...no bonafide end
to precip chances is foreseen until this happens! (Even then, early
signals are another system may be on the heals of this one out
toward next weekend.) Confidence is still relatively low in the
exact mechanics of many of these moving parts (including tracks and
positions), which will have a major impact on resultant timing of
heaviest precip, snowfall totals for a given location, and wind. The
ECMWF remains noticeably drier overall compared to the wetter GFS
(which is also potentially skewing EC-based EFI/SOT values), and
while 500mb height cluster analysis isn`t in terrible disagreement
Wed, by Thu and Fri multiple scenarios are at play, especially in
regard to how far SW the overall trough elongates. We`ll also note
that today`s deterministic runs bring the closed mid-level low much
closer to/over our CWA compared to yesterday (so things are still
changing a bit in the guidance), and that as far as ending this
system...all ensemble clusters currently keep the trough axis either
over or west of our CWA through at least Fri. We really need to
continue monitoring some trends here before getting too specific on
exact numbers/details, but a few other useful things on our mind at
this juncture: 1) Most of this system will favor heavy snowfall in
areas that perform well on deep-layer WNW flow, 2) Warmer high temps
in the 40s Mon from Pocatello west across Shoshone, Burley, and
Malta would favor rain for the first day of the system and
potentially hold accumulations near zero here until Tue, 3) Tue high
temps have ticked up a few degrees in the forecast, increasing
uncertainty in this same corridor on snow accumulations for day 2 of
the event as well, 4) The blowing/drifting snow signal remains solid
throughout Mon-Wed with WSW winds gusting 30+ MPH, which would be
especially problematic almost everywhere outside of the warmer
corridor just discussed until sometime Tue/Tue night, and then
everywhere Wed, 5) The overall flavor of this system still looks to
target the mntns/highlands near and east of I-15 for the most
significant accumulations...potentially measured in feet at least
from the passes up into the backcountry, and finally 6) Depending on
the exact track of the low, there is some low-confidence potential
in a Snake Plain convergence band Wed AM which could enhance
snowfall totals in the plain. Right now, the NBM 3-day probability
of exceeding 4 inches of snow is 60-90% across ALL of our mntns, and
10-30% for places like Pocatello, Idaho Falls, and Rexburg. We
continue to encourage everyone to stay tuned as the forecast evolves
over the next few days, and bear in mind that widespread travel
impacts will be very possible in the Mon afternoon through Wed eve
(if not into Thu) timeframe. We`ll dig into better specifics on
timing, accumulations, and winds as the event approaches. Colder
temps are likely toward the end of this system Thu-Fri, although
perhaps not quite as cold as what we just saw over the past several
days. - KSmith
&&
.AVIATION...A departing ridge of high pressure will maintain
relative control of our wx through the 18z TAF period (through Sat
AM), maintaining dry, partly sunny, VFR conditions with very light
winds less than 10kts and just some high clouds drifting through at
times. Fog/low stratus potential is low again tonight/Sat AM, with
the HRRR once again the most aggressive among the guidance envelope
and favoring the Arco Desert region. Thus, have again hinted at this
at KIDA with VCFG and SCT005 (we saw very BRIEF issues this this
last night/this AM). Sat afternoon/eve, expect a shortwave trough to
spread snow across the region, along with a bit more wind initially
out of the SW. MVFR cigs/vsbys are likely at most terminals by late
afternoon or early eve with this system. - KSmith
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 AM Saturday to 11 AM MST Sunday for
IDZ053-054-058-060-062-063-065-066.
Winter Storm Warning from 11 AM Saturday to 11 AM MST Sunday for
IDZ064.
&&
$$
Area Forecast Discussion
National Weather Service Phoenix AZ
447 PM MST Fri Feb 17 2023
.UPDATE...
Updated Aviation
&&
.SYNOPSIS...
High pressure over the Intermountain West will help bring breezy to
windy conditions today, especially at higher elevations. As an upper-
level ridge builds across our region, a gradual warm up will occur
for the weekend. Uncertainty remains regarding our next system for
early next week, which will meander off the California Coast for the
next several days. A stronger system has a chance to bring gusty
winds and an elevated chance for rain Wednesday.
&&
.DISCUSSION...
Cool, dry air will stick around today and keep temperatures below
normal with highs in the middle to upper 60s. High pressure over the
Intermountain West has caused the surface pressure gradient to
tighten over Central Arizona creating windy conditions. On the east
side of our CWA, for the high terrain areas, a Wind Advisory remains
in effect until 3 PM MST today, but it is unlikely that it will be
extended as most areas in the original advisory will start to see
winds diminish this evening. Latest HRRR runs show some higher
terrain areas may continue to see isolated 40 mph gusts tonight. In
the lower elevations of South-Central Arizona, winds will not be as
strong, but gusts 20-25 mph will last through tonight, especially
for areas immediately east of Phoenix. These winds will cause
difficult driving conditions at times and some minor impacts can be
expected where gusts remain elevated.
Heading into the weekend, low-amplitude ridging will bring us a
gradual warming trend. The latest NBM and HRRR models show
temperatures slightly above normal with highs forecasted in the
lower to mid 70s Saturday. It will still be breezy over the higher
terrain of our eastern CWA. Probabilities of wind gusts exceeding 30
mph will be >80% through around 08Z before decreasing further. By
Sunday, high temperatures will once again be in the low to mid 70s.
Mid to high level clouds will move out of the region Saturday
morning and conditions will be clear for the remainder of the day.
Sunday morning looks to be clear as well until more mid to high
clouds spread over the region Sunday afternoon.
Looking ahead to next week, ensemble clusters show uncertainty
surrounding the timing of our next system. A low pressure center
will spin off the West Coast and remain there over the weekend. This
system is expected to move over our region beginning early next
week. Some clusters show the onset of the system beginning Monday,
while others show a Tuesday time frame. Latest NBM forecasts have
temperatures remaining slightly above normal for Monday and Tuesday.
However, model spread remains due to the uncertainty of the timing
of the previously mentioned system. PoPs for this system remain low
(5-20%) Mon-Tues. The GFS along with model clusters show a more
vigorous trough moving through the Great Basin starting Wednesday.
Temperatures associated with this system may run around 10 degrees
below normal. As of now, windy conditions are possible across most
of South-Central Arizona and Southeast California, along with an
increased chance of precipitation (40-70%) for the eastern areas of
our CWA.
&&
.AVIATION...Updated at 0000Z.
South-Central Arizona including KPHX, KIWA, KSDL, KDVT:
Gusty east winds will be the primary weather issue through
Saturday morning under periods of thicker high cigs. Just off the
surface, E-SE winds at 20-40kts will pick up overnight. KIWA has
the highest potential to reach LLWS potential for the TAF. While
not as strong Saturday, the east component should prevail well
into the late afternoon. Winds turn to southerlies around sunset
before becoming light and variable Saturday night.
Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather issues should exist through Saturday morning
under periods of thicker high clouds. At KBLH, north winds will be
preferred the majority of the period, becoming southerly Saturday
afternoon. At KIPL, there also may be a tendency for directions to
back more westerly after sunset. After sunrise winds will be light
and variable.
&&
.FIRE WEATHER...
Below normal temperatures are expected this morning before a
gradual warming trend takes hold this weekend due to building high
pressure across the west. Temperatures will be at or above normal by
Saturday. Below normal RHs are expected the next few days, generally
bottoming out around 15-20 percent each afternoon. Surface wind
speeds are expected to increase this morning, bringing breezy
conditions to south-central Arizona through this afternoon. Lighter
wind speeds will return through the rest of the weekend into early
next week. Meanwhile, a low pressure system will meander in the
eastern Pacific early this weekend, however there is some
uncertainty with regard to if and when impacts and precipitation
will next affect the Desert Southwest.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Worley
AVIATION...Macfarlane/Heil
FIRE WEATHER...Leffel
Area Forecast Discussion
National Weather Service Pueblo CO
251 PM MST Fri Feb 17 2023
.SHORT TERM...(This evening through Saturday)
Issued at 251 PM MST Fri Feb 17 2023
Key Messages:
1) Saturday is looking warmer and breezier for most with increasing
cloud cover.
2) Damaging winds are possible for our southern Sangres and the
southern I-25 corridor, beginning tomorrow afternoon.
Currently..
Water vapor imagery shows us wedged in between three main features
that will influence our weather over the next 24 hours. A departing
trough is pushing off to our east, with a longwave trough axis to
our north. Another low is present off the coast of Baja, California.
This leaves us under a ridge of high pressure, with clear skies,
warming temperatures and downsloping winds prevailing across much of
our forecast area. Most of our plains locations have warmed into the
low 30s as of 2pm. Visible satellite imagery reveals a lot of
snowpack melting this afternoon as well.
Rest of Tonight and Tomorrow..
Downsloping winds will continue to keep temperatures slightly warmer
for our banana belt locations tonight, with most of these locations
only dropping into the mid and upper 20s. Further east, especially
through the Arkansas River Valley, we`ll see lows falling into the
teens above zero, with another night of single digits and teens
below zero expected for the high country.
Tomorrow..
As the ridge breaks down overhead through tomorrow morning, an
embedded shortwave trough moves in by tomorrow afternoon. This
shortwave trough will interact with the longwave trough north of us,
and the low coming onshore over the Baja peninsula throughout the
day tomorrow, bringing increasing westerly flow and increasing cloud
cover to our area. A combination of cloud cover and existing
snowpack will likely keep daytime highs in the mid and upper 50s
tomorrow on our plains. Westerly winds start to really ramp up
across our southern Sangres tomorrow afternoon, as the jet axis
approaches from our southwest. A High Wind Watch has been issued for
the southern Sangres and the southern I-25 corridor from tomorrow
afternoon until Sunday afternoon.
.LONG TERM...(Saturday night through Friday)
Issued at 251 PM MST Fri Feb 17 2023
Key Messages:
1. High Wind Watch in effect through 11am on Sunday morning for the
southern Sangres, Huerfano, and Las Animas Counties. Wind gusts in
excess of 60 mph are possible.
2. Heavier mountain snow possible from Tuesday through Thursday with
the potential for snow over the mountain valleys and the plains,
though still uncertain.
Saturday Night and Sunday:
A west to east oriented jet streak moves from south to north
positioning itself in a favorable position for mountain wave
activity over the southern Sangre de Cristo Mountains and the
Spanish Peaks region Saturday evening through Sunday morning. Model
sounding show a distinct mountain top inversion with a hint of
reverse shear. There are varying outcomes from models with CAMs
resolving the mountain wave. The 18z HRRR has an interesting output
where it resolves a mountain wave at the beginning of the long term
period, but as the night time inversion sets up the winds decrease,
then once the inversion dissolves after sunrise on Sunday the strong
winds return. The NAMNest on the otherhand keeps the strong winds
from the mountain wave continuing through the overnight, then
weakening as the inversion breaks but continuing throughout the day
on Sunday. So overall, there is still a bit of uncertainty of what
will occur, but we do have confidence that a mountain wave will form
over the aforementioned region. The intensity and if the winds
continue during the overnight will be the main point of uncertainty.
There are some signals of a weaker mountain wave forming over
western El Paso County, on the lee of the Ramparts, Pikes Peak, and
Cheyenne Mountain. This wave would form a little later, after
midnight, and wind gusts would be around 40 - 50 mph. Since this
isn`t in the most favorable location, since the jet axis is a bit
further south, we have excluded this from the High Wind Watch. We`ll
keep reevaluating, though. Wind gusts during the late morning and
evening will be from the west-northwest gusting from 35 to 45 mph,
with the strongest winds on the western portion of the plains.
Strong wind over the central mountain are expected on Sunday
afternoon as well, which may reach close to High Wind Warning
criteria winds. The mountain valleys are expected to have wind gusts
around 40 to 45 mph on Sunday as well. Overall, a very windy day for
most!
Snow showers are expected over the Continental Divide, specifically
over the Sawatch Range throughout the day on Sunday, but relatively
minor accumulation of around 3 to 6 inches are expected.
Low temperatures Sunday morning will be in the teens to 30s over the
plains and the single digits to 20s over the mountain valleys, with
the coldest temperatures being over the valley floor over the San
Luis Valley and upper Rio Grande Valley. Plan on temperatures in the
40s to 50s over the plains and the 30s to 40s over the mountain
valleys. I dropped max temperatures by a few degrees to incorporate
snowpack, as well.
Monday through Friday:
We are monitoring the potential for a heavier mountain snow event
from early Tuesday through Thursday. A long wave trough over the NW
US is expected to interact with a closed low over the desert SW, the
resulting model derived outcome from these interactions are a fairly
potent SW to NE oriented jet streak funneling Pacific based moisture
towards our mountains. These kind of interactions between two
dynamic systems are hard to resolve via modeling, so we`ll have to
keep an eye out, but we are have higher confidence of this storm
occurring since the ensembles are in fair agreement. The EPS and
GEFS total QPF through Thursday morning have in excess of 1.0" of
liquid falling over the eastern San Juans. A cold front associated
with this complex system is being resolved to propagate over the
plains at some point on Wednesday, which may bring some snow over
the plains, however, the main brunt of the QPF is staying over the
NE plains of CO. Cold air is associated with the airmass proceeding
the cold front, so some cold days and nights are possible Wednesday
and onward.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 251 PM MST Fri Feb 17 2023
VFR conditions are expected at all three TAF sites, KCOS, KPUB, and
KALS for the next 24 hours. Mid and upper-level cloud cover will
increase through the period. Southerly and southwesterly winds
gusting up to 25kt are expected at KALS tomorrow afternoon and
evening. Increasing westerly winds are expected for KCOS and KPUB
tomorrow as well, especially after 18Z tomorrow afternoon.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Saturday afternoon through Sunday morning
for COZ074-075-087-088-094.
&&
$$
SHORT TERM...EHR
LONG TERM...SKELLY
AVIATION...EHR
...Update to aviation forecast discussion...
.DISCUSSION...
Issued at 249 PM CST Fri Feb 17 2023
Key Points:
- Very high fire danger Saturday, especially across east central and
north central KS
- Warm into early next week, some precip chances mid-week
Low-amplitude upper ridge is beginning to make its way across the
central Plains, leading to a warming trend in temperatures today and
into the weekend. A closed low is noted in the eastern Pacific off
the CA coast. At the surface, high pressure sits over TX/OK and a
more robust low pressure system has developed in Manitoba/Ontario,
leaving a trailing front into the northern Plains.
The upper ridge quickly moves overhead tonight with a transition to
southwest flow as we head into Saturday. Weak perturbations in the
flow look to induce a deepening lee sfc trough, which results in a
tightening pressure gradient across east central KS overnight and
through the day Saturday. A 40-50 kt LLJ is also progged to move
into the area during the morning and afternoon, then push east in
the evening. Mixing up to 900mb plus the pressure gradient should
allow for sustained southwest winds of 20-25mph with gusts of 30-
40mph, strongest along and south of I-70. This is also supported by
HREF data. There could be isolated locations that reach wind
advisory criteria, so wouldn`t rule out a headline if winds trend
higher, but at this time this looks like a marginal concern not
widespread enough to warrant a headline. The bigger story will be
elevated fire danger as drier air is advected into the area from the
southwest. (See fire wx section for further details.) Some high
clouds moving in from the southwest could keep high temperatures
down slightly, but think the winds should be enough to bring us into
the 50s area-wide. A few models are hinting at light QPF in east
central KS late afternoon and early evening as well. Think the dry
air in the low-levels should prevent this from reaching the ground
so have kept a dry forecast, but wouldn`t be surprised to see some
virga develop.
Sunday sees a transition to mainly zonal upper flow with lighter
winds as the sfc trough moves across the area. This weak boundary
looks to only have a small effect on temperatures with highs in the
upper 40s near the KS/NE border while still reaching the 50s
elsewhere. The aforementioned upper low is progged to slowly move
into northern Mexico and eventually rotate into the southern CONUS
while phasing into the northern stream trough. Precip chances
increase Tuesday and more so Wednesday into Thursday, but plenty of
uncertainty remains in the evolution of that system. Highs remain in
the 50s and 60s until Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 510 PM CST Fri Feb 17 2023
VFR conditions will continue in a dry lower troposphere and
notable boundary layer mixing through the bulk of this
forecast. Low-level jet development suggests at least some gusts
will reach the surface through much of the nighttime period and
should present more of a turbulence instead of wind shear
situation. The stronger winds should reach the surface by 18Z and
persist through the end of this forecast.
&&
.FIRE WEATHER...
Issued at 249 PM CST Fri Feb 17 2023
This morning`s 12Z sounding from DDC showed a dew point of
6 degrees, and some sfc obs in central and southwest KS have
continued to show dew points in the single digits to low teens.
Additionally, forecast soundings in our local area indicate very dry
air aloft, especially above 900mb. So if we mix to 900mb or perhaps
even a bit deeper, this could be problematic for fire weather. The
RAP and HRRR are lowest on model guidance regarding RH, but they
have generally been handling dew points well, so think those
solutions aren`t necessarily far-fetched and shouldn`t be ignored.
Have incorporated the 15Z RAP dew points into this forecast package
and ended up with RH in the 20-25% range across much of the area.
This is still on the low end of guidance, but would not rule out
parts of north central KS dropping as low as 10-15% as RAP/HRRR have
indicated. If we continue to trend lower on RH with the next
forecast cycle, a Red Flag Warning may be needed. Currently, at
least expect very high fire danger with 20-25% RH combined with
southwest winds gusting 30-40mph.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Picha
AVIATION...65
FIRE WEATHER...Picha