Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/19/23
Area Forecast Discussion
National Weather Service Cheyenne WY
410 PM MST Sat Nov 18 2023
.SHORT TERM...(This evening through Sunday)
Issued at 345 PM MST Sat Nov 18 2023
A shift in the current weather pattern arrives this evening as the
leading edge of an upper-level trough pushes across the Rockies.
Expect shower activity to develop across the mountains this evening
and push into the Interstate-80 corridor and potentially as far east
as Interstate-25. Based off Hi-Res guidance, showers this evening
look convective in nature, especially those moving across Carbon and
Albany counties this evening. The RAP shows approximately 100 to 200
J/kg of CAPE, which, as stated in the previous forecast package,
could lead to a rumble of thunder or two. It could also lead to some
brief moderate rain/snow at times. 700 mb temperatures are around
-2C to 0C which will likely keep snow levels above 7000 feet, and as
a result, keep impacts to a minimal. Not looking at much in the way
of accumulations, especially in the lower elevations. The Snowy and
Sierra Madre Ranges could pick up a quick 2 to 5 inches of snow
overnight.
During the day Sunday looks relatively benign. Hi-Res does not show
much in the way of precipitation, however, there is moist low-levels
with westerly flow which could trigger some orographic snow showers
over the mountains. The better precipitation chance will be Sunday
night as a closed 500 mb low develops just east of the CWA. There is
some uncertainty associated with this system as the GFS and ECMWF
have differing low placements. However, both models do show a fairly
vertically stacked low and mid-level low. The surface low remains
further south. Regardless, the placement of the 500 mb low, whether
its the GFS in Nebraska, or the ECMWF in Kansas, taps into deep
gulf moisture. This moisture will wrap around the north side of
the low and eastward into the Nebraska panhandle. The synoptic
models/ensembles are having a hard time resolving any
precipitation across the panhandle, so relied heavily on Hi-Res
guidance for PoPs. Hi-Res does show some pretty good precipitation
across western Nebraska. Since the bulk of precipitation will
fall Sunday night into Monday morning, did increase QPF and
snowfall amounts for areas east of the Laramie Range. Snowfall
amounts could be enhanced along the Pine Ridge and for areas north
of it as northerly upslope flow will dominate in these areas.
Overall, accumulations should be minimal across the lower
elevations, but the mountains could pick up a few inches.
Snow showers will taper off Monday afternoon. Monday will be on the
windy side and the cool side as the CWA sits on the backside of the
low. 700 mb temperatures will be around -6C leading to high
temperatures in the 30s and 40s. Strong northerly winds will make it
feel even colder with frequent gusts up to 40 MPH possible.
.LONG TERM...(Monday night through Saturday)
Issued at 200 PM MST Sat Nov 18 2023
A big pattern shift is on tap just in time for the Thanksgiving
holiday which will bring much colder temperatures and the threat of
snow to the region. Prior to this pattern shift, conditions are
expected to continue to be dry and mild with light winds. The winds
could increase across the wind prone areas on Wednesday ahead of the
advancing storm system.
Monday night through Wednesday will be a continuation of the quiet
and mild conditions we have experienced over the past couple of
days. Models are in good agreement in a deep ridge-trough-ridge
pattern locked in from west to east across the CONUS. Much of the
Intermountain West and Front Range will be under the high amplitude
ridge with the Front Range under the influence of a dry, northwest
to northerly flow. The CAA is rather weak so temperatures will
continue to be in the 50s across much of the region on Tuesday and
Wednesday. The ridge will begin to breakdown and flatten out
Wednesday with the flow shifting back toward the west which will
signal the beginning of the upcoming pattern shift. Embedded in this
westerly flow are pieces of shortwave energy that may be strong
enough to initiate some elevated wind gusts across the Arlington and
Bordeaux wind prone areas. In house models are already giving a 40%
probability of high winds occurring at Bordeaux Wednesday morning.
Long range models are in agreement of a pattern shift but differ
some on the exact evolution of the storm system and the track. All
indications point toward some type of long wave, negatively tilted
trough ejecting out of the Pacific northwest with a baroclinic zone
be dragged south out of Canada. Timing of the CAA amongst the models
are in relatively good agreement, but the timing of main trough
axis differs buy some 12hrs with the GFS bringing the system in the
region Thursday night and the ECMWF having a Friday morning arrival.
This system looks to bring much colder temperatures and the chances
of some widespread snow to the region with accumulating snow
possible across the valleys.
Big differences emerge toward next weekend with the ECMWF showing
the potential for some cold, arctic air advecting into the region
with a cold core low dropping out of central Canada. This is only
one model with little ensemble support but something to watch going
forward.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 405 PM MST Sat Nov 18 2023
Primary concern with the 00Z TAFS will be lower conditions at KRWL
and KLAR. Best chances look to be at KLAR this evening as short
term guidance shows rain and snow showers developing and becoming
fairly widespread. IFR conditions looking fairly good for KLAR and
followed HRRR guidance on timing. With less confidence...held off
on lower conditions at KRWL. Would not be surprised if they go
down...but will continue to monitor and amend the TAF as needed.
VFR conditions elsewhere.
&&
.FIRE WEATHER...
Issued at 122 AM MST Sat Nov 18 2023
No fire weather concerns this weekend through next week with a
more unsettled and much colder weather pattern expected. Increasing
clouds expected today with some rain/snow shower activity this
evening for mainly Carbon and Albany counties. Can`t rule out a
few rumbles of thunder. Otherwise, much colder weather expected
for next week with a good chance for snow.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...SF
LONG TERM...AW
AVIATION...GCC
FIRE WEATHER...TJT
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
301 PM PST Sat Nov 18 2023
.SYNOPSIS...Showers and isolated thunderstorms are forecast this
afternoon through tonight. Strong winds are expected in Del Norte
and Humboldt counties this evening. Shower activity will diminish
late tonight and Sunday as a colder and more stable airmass
settles over the region. Mainly dry weather is expected through
the week with light rain possible Wednesday.
&&
.DISCUSSION...Showers continue across the area this afternoon.
These are driven by a sharp upper level trough and a strong upper
level jet. The HREF mean shows CAPE peaking around 250 j/kg mid
afternoon across much of the area. This will bring the potential
for some thunderstorms. Some of these may be stronger with gusts
to 40 mph and possibly pea sized hail. Locally heavier downpours
are expected with these showers. This could cause some debris flow
so have left the flash flood wash in effect. Behind the front
winds are expected to quickly become northwest and increase to 40
to 50 mph in Humboldt and Del Norte counties. The NAM is showing
winds of 45 kt at 925 mb over the waters this evening and the HRRR
shows winds of 40 kt at just 1000 feet above the surface. The
water vapor satellite shows rapid mid level drying indicating
sinking air. This will likely bring these stronger winds to the
surface. These are only expected to last a few hours at most, but
have opted to issued a wind advisory for this evening in Humboldt
and Del Norte counties. Snow levels are expected to drop this
evening and tonight as the colder air moves in, however showers
will be diminishing as this occurs. Snow levels may drop down to
3500 to 4000 by morning, however by this time most of precip will
have ended. Mendocino and Lake counties will see showers end
tonight and some areas may clear out. However, fog is likely to
develop in the valleys and this will keep most of the valleys from
dropping below freezing. Shower coverage will continue to
diminish in the north Sunday morning with mainly dry conditions by
the afternoon. It is still possible a few showers will pop up
over the interior in the afternoon, but confidence is low on this
and will leave them out of the forecast.
Sunday night into Monday morning is expected to be a chilly night
in many areas. This may result in frost, even along the coast.
Some areas could see freezing temperatures as well, but
confidence is low on that. There could be too much moisture
lingering. Monday and Tuesday are both expected to be dry with
highs in the interior in the upper 60s. It is possible there will
be lingering valley clouds through midday in the north and this
may keep temperatures cooler than expected. So have dropped
forecast highs for Monday and Tuesday in the interior valleys
north of Hwy 36. Light offshore flow is expected to keep the coast
clear and this should allow temperatures to warm into the low 60s
as well.
Wednesday and early Thursday some of the the ensembles are
showing a weak system clipping the northern portion of the area.
The NBM is showing a 40 to 80 percent chance of 0.1 inches in 48
hours in Humboldt and and Del Norte counties, highest in the
north. Dry weather is expected to return for friday and the
weekend. Chilly overnight lows and pleasant afternoons are
expected in most areas. The northern valleys may see low clouds
and fog overnight and through midday keep the temperatures cooler,
although I have not adjusted the forecast to account for that
yet. MKK
&&
.AVIATION...Showers activity continue moving across the region
ahead of a strong front. The primary concern for the aviators during
the next few hours will be strong LLWS, with gusty W-NW winds as
secondary. A rapid wind shift and quick increase W-NW is expected
around 23Z along the coastal terminals. Strong gusty winds from
30 to 40 kts is expected from 23Z to 4Z tonight along the coastal
terminals. MVFR conditions, dropping to IFR/LIFR conditions with
heavy rain are expected to continue tonight across the coastal
waters. VCTS activity remain possible for mainly ACV and CEC
through 19/09Z. HIRES model guidances are suggesting showers
gradually tapper off overnight into Sunday.
&&
.MARINE...A rapid wind shift and increase NW winds is expected
during the next few hours into early evening. ASCAT Scatterometer
wind were showing stronger winds than expected across the offshore
waters early this afternoon. Gale force winds with gusts up to 40
knots will be likely across the coastal waters as result. Have
extended the Gale Warning into the inner waters a result. In
addition, a large northwesterly swell will build in behind the
front late tonight, peaking at about 15 feet at 12 seconds.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
Wind Advisory until 9 PM PST this evening for CAZ101>106.
Flash Flood Watch until 7 PM PST this evening for CAZ102.
NORTHWEST CALIFORNIA COASTAL WATERS...
Gale Warning until 10 PM PST this evening for PZZ450-455.
Hazardous Seas Warning from 10 PM this evening to 4 PM PST
Sunday for PZZ450.
Gale Warning until 11 PM PST this evening for PZZ470-475.
Hazardous Seas Warning from 11 PM this evening to 4 PM PST
Sunday for PZZ470-475.
&&
$$
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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
555 PM CST Sat Nov 18 2023
...Aviation Update...
.DISCUSSION...(This evening through Saturday)
Issued at 308 PM CST Sat Nov 18 2023
Key Messages:
* Rain will begin overnight tonight and persist through the day
tomorrow and into Monday. It will be seasonally cool and cloudy.
* The bulk of our November moisture in the form of liquid is
expected with this system.
* Dry for mid-week, including Wednesday and Thursday
(Thanksgiving), but colder starting Thursday.
* Next system arrives Friday with a 60-70 percent chance of at
least 1 inch of snow which may impact post holiday weekend
travel.
Tonight - Monday:
A broad deep trough is approaching the middle of the country from
the west. This system will bring our extended period of
precipitation beginning tonight and persisting off and on through
Monday. A number of small disturbances will round the base of the
trough as a very broad close low develops. Plentiful moisture
originating from the west coast of Mexico in the tropics will be
advected out ahead of this trough. The ECMWF ensemble shows PWAT
anomalies 1.5-3+ times normal for late November. This means that
the rain will be more efficient.
Almost the entirety of south central Nebraska and north central
Kansas will see at least 0.5 inch of rain (80% chance). The
multi-model ensemble NBM indicates that a smaller area angled
from northwest to southeast from roughly Lexington to Hebron, NE
has at least a 50% chance of seeing at least 1 inch of rain with
this system. Meanwhile the ECMWF Ensemble (a part of the NBM)
focuses the area that has a 50% chance of seeing 1 inch of rain a
bit further south, primarily in north central Kansas. Regardless,
the reality is that south central Nebraska and north central
Kansas will see rain over the next 48 hours, which will help the
area make some small progress in the drought. Models also indicate
that there could be some areas with MUCAPE ahead of the primary
wave which could bring some non-severe thunderstorms at times.
This will help those areas see higher amounts of rain.
The monthly normal for rainfall for November at KGRI is 1.10
inches. So far in November KGRI has received 0.04 inches. The
remainder of the precipitation after this system for November
looks to come in the form of frozen liquid. Thus this system will
likely bring the bulk of our seasonal normal precipitation for
November.
The trough/upper low will tighten up as it moves eastward for
Tuesday. The impact for south central Nebraska and north central
Kansas will be breezier northerly winds and cool temps before
surface high pressure builds in for the second half of the day.
Wednesday - a popular travel day for the Thanksgiving weekend
will be seasonally pleasant as lee troughing develops.
West/southwest winds and mostly sunny skies will promote a
relatively nice day for travel, and any outdoor activities you may
have planned.
The next cold front arrives Wednesday night and Thanksgiving will
be cold - a shock to our system really with highs in the 30s to
40s. As we move into the weekend - the ECMWF Ensemble indicates a
near 80-90 percent chance that highs will be at or below freezing.
In combination to this cold, is the next potential for
precipitation which will come in the form of snow. The EC Ensemble
indicates that precipitation would begin late Thursday and
continue with at least off and on chances until mid Saturday as a
couple of disturbances impact the area. For areas along and north
of I-80, this system has a 70-80 percent probability of bringing
1 inch of snow by Saturday evening with a 30-50 percent chance of
greater than 3 inches of snow. For the remainder of the area south
of I-80 into north central Kansas there is a 60-70 percent chance
of 1 inch of snow, and less than a 30% chance of exceeding 3
inches. This is a system to watch as it may impact post- holiday
travel.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 542 PM CST Sat Nov 18 2023
The HRRR model has the precipitation coming into our TAF sites a
little earlier than advertised in our previous TAFS. We expect to
see the rain in Kearney first and then Grand Island shortly
thereafter. Once the rain moves in it will be rather steady
through much of the morning and then could be a little more spotty
by afternoon. KEAR is most likely to see breaks in the rain by
later in the afternoon. The ceilings and visibility are expected
to fall once the rain moves in. At this point visibility will
likely be more MVFR, but ceilings are expected to be IFR through
most of the day on Sunday. There is some uncertainty in the
ceilings and they will probably bounce around some between LIFR,
IFR, and low end MVFR. However, the predominate ceiling category
for Sunday is expected to be IFR.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...Billings Wright
AVIATION...Wesely
Area Forecast Discussion
National Weather Service Jacksonville FL
858 PM EST Sat Nov 18 2023
...New UPDATE...
.UPDATE...
Issued at 850 PM EST Sat Nov 18 2023
For the latest NE FL and SE GA Daily Key Messages please visit:
https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf
Mostly clear skies expected to prevail tonight with loss of daytime
heating and winds will be light to calm. With dewpoint depressions
down to near 2 deg or less as of 8 PM per half the METAR observations,
some patchy fog is expected to form. The fog is expected to form
over the next few hours, mainly over the eastern zones where better
moisture pooling is located. This agrees with the latest HRRR and
the LAMP guidance, from coastal southeast GA southward through
the JAX metro area, to near Keystone Heights and Palatka. Fog may
increase in coverage for inland northeast FL after midnight,
especially east of I-75 toward the St Johns River basin. Locally
dense fog will be possible. No significant change to lows in the
lower 50s inland southeast GA to mid to upper 50s for northeast FL
and coastal southeast GA.
For marine forecast, we have the small craft advy (SCA) for just
the offshore northeast FL waters rest of tonight, and seas at the
buoys nearshore down to about 5 ft or so. Marginal exercise
caution (SCEC) headline was retained for nearshore for now.
Noting the local NWPS is over-forecasting heights by about 1-1.5
ft so blended NWPS guidance with the GFS- wave.
&&
.NEAR TERM...
Issued at 1259 PM EST Sat Nov 18 2023
Finally sunshine today as dry air advection under NNW low level winds
between a departing wake trough sliding southward across FL and
high pressure building northwest of the region, scouring out the
persistent cloudiness across the area. Partly cloudy skies will
continue through late afternoon as diurnally enhanced cumulus
stream over the area with mild, but above normal high temperatures
in the mid to upper 70s.
With recent rainfall and moist surface conditions under mostly
clear skies tonight, ground fog is expected to form across inland
areas after sunset as winds decouple. A feature that could limit
the extent and persistence of fog tonight will be another
wake/backdoor surface trough axis that will slide from NNE to SSW
across the area from the Carolinas tonight. The trough axis could
keep boundary layer winds mixed at times and bring the potential
for some shallow clouds/stratus, but it could also promote
moisture pooling near the trough given its slow drift across the
area. At this time, favored a more `foggy` solution with patchy
fog developing this evening through midnight for most locations,
including the local coast, then fog expansion and coverage
increasing to areas of fog for coastal SE GA counties SSW along
the St. Johns River basin where higher daily rainfall occurred and
winds tonight are expected to be near calm. Confidence still not
high enough for dense fog verbiage (visibility < 1/4 mile) at this
time.
Mild, above normal low temperatures will range in the 50s inland
to near 60 toward the coast.
&&
.SHORT TERM...
(Sunday through Monday night)
Issued at 1259 PM EST Sat Nov 18 2023
Mostly clear and partly cloudy skies anticipated for Sunday as
high pressure conditions build in over the forecast area with more
cloudy conditions returning on Monday with a chance for widely
scattered light showers developing over inland areas Monday
afternoon. Coastal troughing will bring convective activity to
offshore waters, but will have a negligible affect for coastal and
inland areas. Potential for foggy early morning developments
during this period with heavier developments expected over north
central Florida and and extending into northeast Florida counties.
High temperatures for this period will be in the upper 70s with
overnight low temperatures dropping down into the lower to mid 50s
for inland areas and in the upper 50s to lower 60s for areas near
the coast and along the St Johns River.
&&
.LONG TERM...
(Tuesday through next Saturday)
Issued at 1259 PM EST Sat Nov 18 2023
High pressure is expected to move have moved offshore before
midweek with the prevailing flow shifting to become more out of
the west-southwest. Showers and storms are anticipated to cross
over the region ahead of an advancing cold front pressing in from
out of the northwest, likely to stall either along or just to the
south of north central Florida. Drier air and cooler conditions
are forecasted to be in place for Thursday however there is a
potential for high pressure to recede to the northeast ahead of an
advancing trough that could potentially bring a return to stormy
conditions before the weekend. Disparity in forecast model
products for the end of the week and into the weekend are keeping
confidence for that period low at this time.
&&
.AVIATION...
(00Z TAFS)
Issued at 700 PM EST Sat Nov 18 2023
Some scattered to broken cumulus clouds linger this evening but
should slowly dissipate late tonight. Still looking at least some
patchy fog development for the TAF sites, but forecast confidence
is a bit lower than usual. Have adjusted some of the timing,
generally starting some MVFR vsby BR by about 05z and then some
IFR by 07z-08z. Overall, looks like best chance of IFR or lower
is at GNV and VQQ. MOS guidance is a still a bit more optimistic
on the fog potential, so expect some changes in the forecast for
later tonight to refine the fog forecast. Continued to advertise
prevailing VFR by 14z Sunday, with scattered cumulus developing
near 3-4 kft in the aftn hours. Winds will be light initially but
become northeast to easterly by the afternoon near 5-10 kts.
&&
.MARINE...
Issued at 1259 PM EST Sat Nov 18 2023
Northerly winds will prevail over the waters today trailing a
departing trough and high pressure building west of the region.
The high will shift the north of the region Sunday, then northeast
into Monday with a return of easterly winds over the local
waters. A front approaches from the west Tuesday into Wednesday
with increasing southerly winds and a low chance of thunderstorms.
Rip Currents: High rip current risk for all local beaches today
with lingering 3-4 ft swells and periods of 10-11 seconds. A
moderate rip current risk is expected for all beaches Sunday.
&&
.HYDROLOGY...
Issued at 1259 PM EST Sat Nov 18 2023
Tidal Flooding: Extended the Coastal Flood Advisory for the upper
St. Johns River basin south of Racy Point which includes Putnam
and inland Flagler counties where Haw Creek rose into Minor Flood
with 4-6 inch storm total drainage funneling into the basin. The
diurnal high tide seiche from downtown JAX to Satsuma continued to
produce minor tidal flooding during the higher evening high tides
near Buffalo Bluff to Satsuma, so confined the river Coastal Flood
Advisory to just this upper portion of the basin and extended
through 10 pm this evening (1-2 hrs after high tide).
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 54 76 57 76 / 0 10 10 10
SSI 60 74 62 74 / 0 0 10 10
JAX 56 77 58 76 / 0 0 10 10
SGJ 60 76 61 76 / 0 0 10 10
GNV 56 79 56 79 / 0 0 0 0
OCF 56 79 57 80 / 0 0 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory until 10 PM EST this evening for FLZ038-
137.
High Rip Current Risk until 4 AM EST Sunday for FLZ124-125-133-
138.
GA...High Rip Current Risk until 4 AM EST Sunday for GAZ154-166.
AM...Small Craft Advisory until 4 AM EST Sunday for AMZ472-474.
&&
$$
Area Forecast Discussion
National Weather Service North Platte NE
528 PM CST Sat Nov 18 2023
.KEY MESSAGES...
- Significant rainfall, over 1/4 inch, is likely across north
central Nebraska Sunday and Monday.
- Accumulating snow is possible Friday and snow chances have
increased to 40 to 50 percent across wrn and ncntl Nebraska.
Confidence in the forecast is medium.
- Subfreezing high temperatures are likely Friday and Saturday.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 315 PM CST Sat Nov 18 2023
A very unusual weather situation developing as three separate
weather features combine to produce widespread rain across parts of
western and north central Nebraska Sunday and Monday.
Satellite and radar show a subtropical disturbance across the srn
Rockies which will move east and phase with a nrn stream disturbance
moving through the Great Basin. An additional upper level
disturbance off the WA/OR coast will drop southeast and the three
systems will form a large upper low across the central Plains by
Monday morning.
The overall evolution of the storm system is slower today with rain
chances just isolated until 12z Sunday. A blend of the HREF and
short term model blend was the basis for definite POPs east of
highway 83 Sunday. This is well supported by the NAM, HREF, HRRR and
RAP models. The HREF was the farthest west with predicted QPF.
Isolated thunderstorm chances are in place along and east of highway
83 Sunday. This forecast leans on the 800mb elevated CAPE shown in
the NAM model. The instability should diminish by early Sunday
evening.
The temperature forecast uses the short term model blend plus bias
correction which is appropriate for strong advections of
temperature, moisture and evaporative cooling from precipitation.
Temperatures aloft in the NAM Monday continue to show the potential
for a changeover to wet snow across northwest Nebraska and perhaps
the western Sandhills. This is supported by the SREF probabilities
and BUFkit but the lift in BUFkit is weak and the near sfc
temperatures in the NBM Monday support wet no accumulating snow. The
wrap-around light rain and gusty winds will exit wrn Nebraska Monday
afternoon and ncntl Nebraska Monday evening. The models are in very
good agreement with this feature.
&&
.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 315 PM CST Sat Nov 18 2023
Attention in the long term continues to focus on the arrival of an
arctic cold front and the potential for accumulating snow Friday.
The morning runs of the ECM/GFS/ICON/GEM plus the available
ensembles have converged on an east west band of snow moving through
Nebraska early Friday morning and throughout the day into the
evening. Confidence in this occurring is medium; there is a chance
the track of the upper level support for snow will shift south and
west favoring KS and COLO.
Nonetheless, it is worth noting h850-300mb RH in ECM and GFS is
above 95 percent during the day Friday and this suggests fairly
strong frontogenesis will be in place. This moisture and very cold
air aloft ranging from -5C at h850mb to -20C or colder at h500mb,
will be quite favorable for snow growth processes. The models are
also hinting that closed h700mb low will form across KS. The track
of this low would dictate where the heaviest snow will fall and POPs
for this forecast have increased 50 percent across wrn Nebraska.
The temperature forecast for subfreezing highs Friday and Saturday
are about 15 degrees below average for this time of year. The
deterministic ECM suggests highs could be 20 degrees below the
average. The blended forecast is close to the ensemble means of the
GFS and ECM.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 528 PM CST Sat Nov 18 2023
VFR will continue through the overnight hours for western and
north central Nebraska, then aviation weather concerns arise
tomorrow. Cloud cover increases and ceilings lower ahead of a
low pressure system, then rain showers develop during the day.
The heaviest showers will likely occur in central Neb,
generally BBW to VTN and points east, although MVFR to IFR
ceilings are expected to the west as well (including LBF).
Light and variable winds tonight become east/northeast tomorrow
and also increase toward evening.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Snively
Area Forecast Discussion...UPDATED
National Weather Service New Orleans LA
946 PM CST Sat Nov 18 2023
...NEW UPDATE...
.UPDATE...
Issued at 937 PM CST Sat Nov 18 2023
Cool and mostly clear conditions this evening across the region.
Over the last hour or two, some lower visibilities have come in
for Houma and Pascagoula, however, widespread fog isn`t
anticipated overnight as temps will tend to chase the dewpoints.
Winds have dropped off to near calm for many sites across the
CWFA allowing for some radiational cooling to take place, but just
off the deck dry air continues to filter into the region from the
north. Went ahead and drop`d temperatures a degree or two,
especially with a very weak northerly flow over our drainage
basins. Overall, temps could even be a degree or two cooler than
currently progged unless upper level clouds begin to filter into
the region, which is currently in the forecast, especially over
the cool favored northern tier. This can be seen on the 00z RAOB
from out back here with a moistening layer just below 500mb or so.
Outside of lowering MinT`s a degree or two, no other changes were
made to the ongoing forecast for the near term. (Frye)
&&
.SHORT TERM...
(This evening through Tuesday)
Issued at 206 PM CST Sat Nov 18 2023
Big story in the near term is the recent frontal passage
introducing drier, cooler air into the area, with a building CAA
regime pressing south this evening. The increase in dry
air/subsidence has also began to break up low clouds owing to
intervals of sunshine here and there to end the day which is good
news for those tired of the gray, dreary recent days. We`ll see
the direr air continue to press south tonight, with the main focus
being temperatures come daybreak Sunday. As mentioned in the
morning update, quite the balance of whether CAA can allow winds
to periodically break above calm to allow some sfc/low-level
mixing and upper- level clouds can build in from the northwest to
offset radiational cooling processes. For now, model soundings
indicate enough noticeable decoupling in the lowest PBL
regardless of 10-15kt winds situated right above the ground to
promote light radiative cooling, but will watch this as well as
how thick upper- level cirrus can advect overnight. With so many
pros/cons for/against a cooler solution, didn`t venture too far
away from deterministic NBM but did apply a cooler bias to the
drainage basins of Pearl River and Pascagoula where southward
filtering drainage will be more than enough to make things
chillier. This settles many areas into the 40`s by daybreak so
it`ll be distinctly more chilly come daybreak but will monitor if
this changes in the near term.
Meanwhile going into Sunday, looking nice overall with CAA
backing down and patchy high clouds. Deterministic highs already
came in close to the 75th but added in a sprinkle of 90th to keep
the warmer bias/trend going in support of ample sunshine/surface
heating and the reduction of CAA. By tomorrow afternoon, we begin
to reestablish a southerly return flow as surface high pressure
drifts just to our east. Also, did aim much drier with dewpoints
17-23Z towards the 10th percentile in NBM guidance to account for
strong PBL mixing tomorrow.
The bulk of this discussion will transition into focusing on the
severe weather threat Monday & Tuesday, so will dive deep into the
weeds starting out with a synoptic overview. Our main player will
be the evolution of a deepening western US longwave trough axis
over time, with eventual downstream low genesis over the south-
central Plains late Sunday into Monday. As with everything, there
are intricate details in the overall pattern and a noticeable
spread in short vs long-range guidance which is typical for this
time frame as CAMs begin to first touch on the system in the
extended hours versus global long-range solutions. Did take a very
in-dept look through all trends of the GFS, ECMWF compared to
extended hour RRFS-A and NAM solutions now coming into the picture
which depict some differences. NAM/RRFS-A have targeted one
feature upstream that changes the downward/forward trough
evolution that can make for a big difference in solutions - the
upstream impulse crossing northern California early Sunday. CAMs
pick this up but keep the energy in tact as it rotates around the
periphery of the longwave trough, keeping in an embedded shortwave
axis transitioning neutral to nearly negative tilt going into
Monday over the southern US. With energy lingering upstream
following the passage, across the PacNW which also gets caught up
into the flow, this morphs the entire trough shape, "flattening"
the base of the trough. This would suggest a more
southern/stronger surface low potential over the ARK-LA-TX region
to central MS given sufficient downstream divergence placement,
ample lift and a distinct enhancement of areal shear ahead of the
developing system late Monday into Tuesday. Last few hours of the
RRFS-A and proximity soundings illustrate this supportive of
mixed mode to mainly supercellular convective initiation
along/ahead of the front with 350+ m2/s2 0-1km SRH and well over
70kt 0-6km bulk shear - absolutely plenty for severe weather,
especially for areas along and north of I-10/12 underneath
maximized lift. Timing would be Monday evening into overnight and
potentially out of here early Tuesday given a faster solution,
with possible transitional storm mode into QLCS as it races east
keeping a isolated tornado threat going into the overnight hours.
Meanwhile, recent global trends identify the upstream northern
Cal impulse but absorb it into the enhanced flow upstream of the
trough, never really allowing it to impact the trough orientation,
staying mainly positive-tilt which typically leads to a more
northern low and weaker. This would be a transitional threat for
our area, with greatest threat for western and northern areas but
diminishing during the transition east overnight from both a lack
of diurnal instability and best dynamic lift ejecting north. I
will say however, the latest 12Z deterministic ECMWF is starting
to hint at the embedded impulse rounding the periphery of the
trough, reaching central Texas 21Z Monday and now has the surface
low reflection a bit farther south. Going to need to iron out the
details in the synoptics but the CAM`s hint at a more dynamic,
southward solution would be something of concern. Typically with
these deeper, southward lows we tend to have more backed (SSE)
surface winds owing to even greater low-level hodograph curvature
supportive for supercells. Don`t want to get too much into the
weeds until guidance can align better, and anticipating better
clarity starting tomorrow where we can dive more into the
mesoscale but for now, even at a minimum, a low-end severe weather
event appears likely for atleast parts of the area, with focus
for western and northern areas (less for coastal SE LA) and will
be monitored very closely. We`ll get into the late hours of the
HRRR and other HREF members tomorrow afternoon which should reveal
more details plus should be initializing the actual shortwave by
the time its now crossing into northern California. Stay tuned
for specifics.
Otherwise, guidance continues to suggest this activity pressing
out of here quicker which may lead to a drier day overall on at
Tuesday after this activity gets out of here. Expect clearing with
cooler conditions and a brisk NW wind following the front during
the day and continuing into the evening. (KLG)
&&
.LONG TERM...
(Tuesday Night through Friday night)
Issued at 206 PM CST Sat Nov 18 2023
There continue to be some discrepancies between the various model
ensemble member solutions. Interestingly enough, the operational GFS
and Euro have basically switched roles with the 12z GFS pushing the
front well into the Gulf while the 12z Euro now hangs it back closer
to the coast resulting in cloudier conditions and lingering rain
chances. Both still indicate some kind of low forming on the tail
end of the front, but impacts vary based on the front location. 12z
Euro ensemble mean solution not available yet, but the 12z GEFS mean
is fairly similar to both its operational run and the NBM. That
being said, really didn`t see much need to make any significant
changes to the NBM through the extended.
Resultant forecast is close to previous with a slight increase in
cloud cover and POPs Wednesday night and Thursday, mainly across
southern areas and the Gulf. This is a reflection of continued
uncertainty in where the front will eventually stall and how the
possible low will evolve and move. Should the pattern trend toward
the front stalling closer to the coast with a low tracking through
the northern Gulf or near the coast, further adjustments to the
forecast will be necessary. Those adjustments would be toward a
wetter, and possibly warmer Wednesday and Thanksgiving Day.
For the time being, though, temperatures look to be below normal
through the second half of the work week with no significant rain
chances beyond Tuesday night. Expect a gradual warming trend into
the weekend. (DM)
&&
.AVIATION...
(00Z TAFS)
Issued at 516 PM CST Sat Nov 18 2023
VFR conditions expected to prevail through the cycle. Winds will
shift from a northerly direction early on...become light and
variable for most...then shift to a southerly or southeasterly
direction later on in the cycle on Sunday. (Frye)
&&
.MARINE...
Issued at 206 PM CST Sat Nov 18 2023
Persistent offshore flow is expected this evening and into tonight
following a recent frontal passage. Surface offshore flow relaxes
later tonight and into the day on Sunday, with winds eventually
becoming back to onshore Sunday and Monday. Increasing onshore
flow is expected to lead to a steady increase in waves/seas to
around 2 to 4 feet offshore, to 3 to 6 feet for outer 20-60nm
zones with winds picking up to 10-15kts. Next cold front and
associated strong to severe storms will race east across the
waters Monday night into Tuesday morning. Main threats are winds
34 knots or greater and waterspouts with this activity, but will
quickly press east by early Tuesday followed by drier air. Strong
NW mainly offshore flow will build in following the frontal
passage with seas returning 2-4ft, to 3-6ft for 20-60nm zones,
decreasing going into mid week. (KLG)
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 42 70 51 73 / 0 0 30 50
BTR 45 73 56 80 / 0 0 20 40
ASD 45 71 53 76 / 0 0 10 40
MSY 54 70 60 78 / 0 0 10 30
GPT 47 69 53 73 / 0 0 10 30
PQL 42 72 49 76 / 0 0 10 20
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&
$$
UPDATE...RDF
SHORT TERM...KLG
LONG TERM....DM
AVIATION...RDF
MARINE...KLG
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
933 PM CST Sat Nov 18 2023
.UPDATE...
Issued at 920 PM CST Sat Nov 18 2023
I have made a few small changes to the forecast for tonight into
Sunday evening. The surface high was located through southeast MO
and southern IL this evening and light winds across the southeast
half of the CWA and clear skies have resulted in efficient
radiational cooling at a faster pace and greater magnitude than
anticipated. As a result I have lowered mins within this region,
especially the eastern Ozarks into southern IL.
The other change was to increase/expand the hourly footprint of
POPs (20-30+ percent) from 21z-03z across central MO. Much of the
guidance including the RAP and NAM are showing increasing mid-
level moisture and attendant mid-level frontogenetic forcing and
convergence across this region after 21z. While low-level
moisture will remain a bit limited this early in the rainfall
event across that area, the aforementioned mid-level combo
suggests some light measurable rain from a mid cloud deck would be
possible in that time frame before greater forcing/moisture and
more widespread rainfall arrive.
Glass
&&
.KEY MESSAGES...
- Confidence is high (90%+) in measurable rainfall (0.01")
occurring Sunday night into Tuesday, with 50-70% chance of at
least 0.5" of rainfall along and south of the I-70 corridor.
- Temperatures will remain above normal through the end of this
weekend, with confidence high (70-90%) that temperatures will
then run right at or below normal Monday through the end of the
week.
&&
.SHORT TERM... (Through Late Sunday Night)
Issued at 217 PM CST Sat Nov 18 2023
Current water vapor imagery shows northwesterly flow aloft over the
CWA on the backside of a trough pushing into the Northeast. At the
surface, observations show an area of high pressure centered roughly
over to just east of the CWA. This pattern has kept our weather
quiet and skies clear, with temperatures running just above
climatological normals. Tonight, the surface high will continue
moving eastward, with weak southerly flow advecting warmer air
into the CWA overnight and causing temperatures to run a few
degrees warmer than compared to last night.
The southerly flow will persist into Sunday, helping temperatures
warm above what was experienced on Saturday. Although, increasing
mid- to upper-level clouds ahead of our next weather system will
help to offset this warming somewhat, with temperatures topping
out just a few degrees warmer Sunday afternoon compared to those
on Saturday.
As we get into Sunday evening into the overnight hours, an upper-
level trough will eject out into the Great Plains as a low-level jet
ramps up over the Central Plains and Middle Mississippi Valley ahead
of a surface low moving eastward out of the Panhandle Region. The
low-level jet will aid in moisture advection ahead of the low and
pair with forcing from the approaching trough to lead to an
increasing chance (30% increasing to 70%) of rain over portions of
central and southeastern Missouri during the late evening into the
overnight hours.
Elmore
.LONG TERM... (Monday through Next Saturday)look i
Issued at 217 PM CST Sat Nov 18 2023
The aforementioned trough will continue to push eastward on Monday,
dragging its surface low with it. Ensemble guidance consensus has
been trending northward with the surface low`s track relative to our
CWA, with it now expected to pass through southeastern Missouri and
southern Illinois on a northeastward trajectory. While confidence
has been high (90%+) in a majority of the CWA seeing measurable
rainfall (0.01"), this slight northward shift in the low`s track has
increased the probability of more of the CWA seeing at least 0.5" of
total rainfall. The probability of this threshold tops out at
roughly 50-70% along and south of the I-70 corridor, with about a 30-
50% chance of 0.5" north of that corridor.
As the trough continues eastward and the surface low makes its way
into toward the Northeast, rain will tapper off west to east during
the day Tuesday, with deep northwesterly flow on the backside of the
trough ushering in a colder airmass into the CWA. However, to what
amplitude and orientation this trough holds through over the Midwest
still varies among ensemble guidance. This impacts temperatures,
with spread among ensemble guidance actually increasing over the
last few initializations to as much as 10-15 degrees within the IQR.
One factor that has been consistent is that the 75th percentile
remains at to just below climatological normals, with the
probability that we remain below normals being 70-90%
through the end of the week. Ensemble guidance has recently begun
pulling toward the warmer end of the distribution, causing the
slight decrease in the probability that we will see below normal
temperatures through this stretch.
As we get into the weekend, the consensus among ensemble guidance is
that a trough will develop over the Great Plains, but ensembles
vary look idrastically in the amplitude and progression of this
trough, leading to high uncertainty in the track of its surface
reflection. A minority (20% or less) of ensemble members produce
light snow at any point Friday into Sunday somewhere across the
CWA. If snow accumulation does occur, confidence is high (90%)
that amounts would be light, as the early week system will send a
cold front to the Gulf and limit moisture return ahead of any
weekend system. Again, the majority of ensemble guidance keeps the
CWA snow-free next weekend, but we will continue to monitor this
portion of the period for any impacts.
Elmore
&&
.AVIATION... (For the 00z TAFs through 00z Sunday Evening)
Issued at 526 PM CST Sat Nov 18 2023
VFR flight conditions are expected through the forecast period. A
few high clouds will move into the area later tonight with
increasing/thickening high-mid clouds on Sunday.
Glass
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
631 PM EST Sat Nov 18 2023
.SHORT TERM...(This evening and overnight)
Issued at 1250 PM EST SAT NOV 18 2023
Aside from some high clouds here and there and some scattered low
clouds across the Keweenaw, mostly sunny skies have dominated Upper
Michigan today, temps to warm into the mid to upper 40s in many
locations.
RAP analysis and water vapor imagery overhead show a longwave broad
trough axis extending north of Lake Erie up to James Bay with a
shortwave embedded within the trough shifting southeast through
northeastern Ontario. This shortwave is expected to continue its
southeast journey overnight while mid-level ridging and a surface
high build eastward across western Ontario and the Upper Great
Lakes. With the passage of the shortwave, its possible (~30%) some
low level convergence in eastern Lake Superior, combined with an
slight influx of colder air aloft to around -8 to -10C will result
in some lake effect showers developing and pressing into eastern
Upper Michigan. Some model soundings suggests a couple hours of
enough saturation for precip, but DGZ access within this layer
appears minimal. The same soundings also suggest an inverted V
signature, suggesting sprinkles or flurries would be more likely
then noteworthy accumulations if anything does fall. Elsewhere,
expect cloud cover to decrease as you move west and south. Overnight
lows should dip into the upper 20s to low 30s.
.LONG TERM...(Sunday through Saturday)
Issued at 356 PM EST SAT NOV 18 2023
Key Messages:
-Temperatures average near normal Sunday-Tuesday, but the western UP
appears warmer than east. Below normal temps arrive by late Tuesday
and persist through the end of the extended forecast period.
-Little to no precipitation until late Monday night or Tuesday.
-For anyone with Thanksgiving holiday travel plans, please continue
monitoring forecasts for updates to potential for rain/snow mix
Tuesday transitioning to several days of possible lake effect snow.
There is good agreement in the extended forecast through Monday
night under split flow aloft. However as we progress through the
middle to late part of next week, uncertainty grows as guidance
spreads, muddling the forecast. The extended starts relatively quiet
with near normal temps. Temps drop down below normal Wednesday as
upper level flow begins to merge and northwest flow with negative
height anomalies cool the region down. This latter part of the
extended forecast starts of with low chances for synoptic snow
followed by persistent chances for LES behind it, however trends in
guidance have suggested that light showers are the most likely
solution next week.
Some lingering light lake effect showers or flurries over the
eastern lakeshore areas is possible Sunday morning, however dry
weather will quickly follow with mostly clear skies returning to the
entire U.P. in the afternoon as brief mid level ridging pushes in
from the west and sfc high pressure builds over the Upper Great
Lakes. This will yield a relatively quiet weather day with near
normal temps in the mid 30s to low 40s. These quiet conditions
continue overnight into Monday as east to southeast winds diminish,
becoming calm over the east and high clouds increase in from the
southwest. Weak southeasterly flow off Lake Michigan will advect
higher dew points over south central. The 3 km NAM and ARW are
trying to squeeze some light freezing drizzle out of this. That
being said, even with the upsloping flow and moisture advection, the
3km NAM model soundings are the only ones that really emphasize the
low level moisture so low cloud development is the likely solution.
The dry weather is expected to continue through Monday and most of
Monday night, possibly into Tuesday as high pressure builds
southeast into southern Ontario and then tracks east. This leads up
to the main story of the extended forecast, which still
unfortunately has some uncertainty in the model guidance. A mid
level trough traversing the northern end of the Canadian Prairie
Provinces on Monday amplifies as it digs southeast through Manitoba
into Ontario Monday night. Meanwhile, a closed low over the Central
Plains will slide over the Mid Mississippi Valley Monday and Monday
night. As the trough continues to dig south through Ontario,
reaching over the U.P. on Tuesday, the closed low lifts northeast
over the Great Lakes Basin and phases with it. As we progress into
Tuesday night onward, guidance really starts to diverge. General
consensus is that the stronger feature is the sfc low to our south,
which keeps the more widespread synoptic precip to our south and
east and means the primary forcing for synoptic scale precip is
limited to the cold front off the low to the north. That being said,
there are a few stronger members of both GFS and ECMWF ensembles
that suggest the low tracks farther north and west through the Great
Lakes Basin which would yield more precip in the south and eastern
U.P. Overall, we can expect a rain snow mix to start late monday
night into Tuesday that transitions to all snow on Tuesday behind
the cold front and subtropical low.
Tuesday night onward, snow showers will primarily depend on lake
effect development. The northwesterly to westerly flow behind the
cold front will likely bring the coldest airmass of the season, with
850mb temperatures behind the cold front on Tuesday dropping to
around -10C Tuesday night and maintaining around -10C well through
next week. This will result in highs dropping down in to the mid 20s
to mid 30s and lows in the teens to low 20s. Winds chills will also
be a concern for holiday travelers Tuesday night onward, especially
as we close in on next weekend when some interior locations could
see wind chills approach zero. These colder temps over the lake will
also provide supportive Lake sfc to 850mb Delta-T for LES, however
ensemble probabilities for LES have been diminishing. The latest GFS
and ECMWF probabilities of only 1 inch in 24 hours Tuesday night
onward do not exceed 50% with the GFS yielding lower probabilities
than the ECMWF. Another thing to note is that probabilities for LES
have trended down in the last few ensemble runs.
The good news is that the current spread in both the deterministic
and ensemble model guidance likely stems from the fact that the mid
level trough and 500 mb vorticity maxima responsible for this storm
system is still over the northeast Pacific Ocean where observations
are sparse. As this trough moves onshore on Sunday, model guidance
should start approaching a much better consensus. In the meantime,
if you have any holiday travel plans, continue to monitor the
forecast as guidance begins to hone in on a solution.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 630 PM EST SAT NOV 18 2023
A weak cold front will settle s into Upper MI tonight. Shallow low-
level moisture following the front combined with cooling to increase
overlake instability will result in stratocu/MVFR cigs developing at
CMX/SAW overnight. These MVFR cigs probably won`t scatter out to VFR
at SAW on Sun since a light onshore wind continues thru the day. At
CMX, optimistically scattered MVFR cigs out to VFR in the early aftn
as low-level flow becomes anticyclonic, but even here, MVFR cigs may
hang on. At IWD, postfrontal air mass won`t be as cold and low-level
flow quickly becomes anticyclonic. Thus, maintained VFR at IWD thru
the fcst period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EST SAT NOV 18 2023
West to northwest winds this evening around 20-25 kts over the
western third of the lake and 25-30 kts over the eastern two thirds
of the lake will gradually veer northerly through tonight as a low
pressure system tracks east of the lake. Winds will diminish below
20 kts across the lake from west to east tonight through Sunday
morning. Winds are expected to stay below 20 kts through Monday as
high pressure builds over the Upper Great Lakes. As this high
pressure shifts eastward and a cold front pushes over the Lake on
Tuesday, northwest winds to 20-30 kts are expected behind the front.
Strong cold air advection in the middle part of next week leaves
some potential for gales, with the best potential between Tuesday
evening and Thursday afternoon.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JTP
LONG TERM...Jablonski
AVIATION...Rolfson
MARINE...Jablonski
Area Forecast Discussion
National Weather Service Pueblo CO
858 PM MST Sat Nov 18 2023
.UPDATE...
Issued at 853 PM MST Sat Nov 18 2023
Made a few minor grid updates to the precipitation chances
overnight across the Plains. Looks like it should remain dry
through Sunday morning. Mozley
&&
.SHORT TERM...(This evening through Sunday)
Issued at 247 PM MST Sat Nov 18 2023
Key messages:
- Snow showers over the higher terrain tonight. Isolated rain
showers possible over the southeastern plains early.
- Increasing showers by later in the day tomorrow, mainly over the
mountains.
- Snow level dropping to around 7000 ft by late afternoon. Slightly
cooler.
Detailed discussion:
Tonight...
An initial shortwave embedded in the deepening longwave trough
over the region is going to move through tonight and provide a few
snow showers over the higher elevations, with possibly 1 to 3
inches over the highest peaks on the southwest facing slopes. As
the associated low ejects out over the plains earlier this evening
and establishes a convergence boundary over the southeastern
plains, there could be some isolated showers, although these will
be very light. These will likely occur through the evening and
then move out of the CWA by around midnight. Cloud cover over this
area will keep the temperatures more modified, and therefore some
of the far southeastern plains will only get down into the 40s
for lows tonight. Also, along the banana belt with weak
downsloping winds, temperatures will also be relatively warmer,
with upper 30s. Elsewhere across the plains, temperatures will
fall to around the freezing mark, or slightly below within the
lower Arkansas River Valley. Lows will generally be in the upper
teens and 20s for high country.
Tomorrow...
Southwesterly flow with moisture advection is going to allow for
snow showers over the higher terrain to continue throughout the
morning tomorrow. A secondary low within the longwave trough will
slide down towards the south near the Four Corners area, and help to
destabilize the mid levels and provide increased PVA. This will
allow for the snow to slightly increase in intensity over the higher
terrain, mainly over the eastern San Juan Mountains and La Garitas
initially, and then filling in towards the north over the central
mountains throughout the afternoon. Some of these showers will spill
over into the San Luis Valley and upper Arkansas River Valley. With
snow levels beginning just over 8000 ft, most of these will be in
the form of rain through the early afternoon, but as the snow level
decreases by later in the afternoon down to around 7000 ft, there
will be some of these showers transitioning over to snow.
Through the afternoon, some of the higher peaks over the
southwestern mountains could receive up to 6 inches of snow, or
locally higher, depending on where the more convective snow showers
materialize with bursts of occasionally heavier snow. There is a
lesser probability (less than 50 percent) of snow over the eastern
mountains through the afternoon, with perhaps only up to 2 inches of
snow over the southern Sangre de Cristo mountains. Any very light
and isolated showers that make it out over the adjacent plains will
be in the form of rain, and given the amount of dry air near the
surface, will likely evaporate before reaching the ground (virga).
It will be slightly cooler tomorrow in general for most locations
with increasing clouds throughout the day. Highs over the plains
will be in the upper 50s to mid 60s, in the 40s to low 50s for the
high mountain valleys, upper ARV and SLV, and in the 20s and 30s for
the highest elevations. -Stewey
.LONG TERM...(Sunday night through Saturday)
Issued at 247 PM MST Sat Nov 18 2023
Key Messages:
- Another round of snow for the mountains and Palmer/Raton Ridges
Sunday Night and Monday with travel impacts expected for the passes
and Winter Weather Advisories posted for the mountains south of
highway 50.
- Very windy on Monday with the potential for gusts nearing high
wind criteria across eastern El Paso county, the Raton Ridge, and
northeast portions of the southeast plains
Models and ensembles are in better agreement for the Sunday
Night/Monday timeframe though there are still some vulnerabilities
with forecast snow amounts in the Pikes Peak region on Monday, and
with the magnitude of strong northerly winds across the plains on
Monday where there is the potential for winds to approach or exceed
high wind criteria.
Energy dropping down the back side of the broad trough/upper low
into the 4 corners region Sunday night will close off a circulation
center before shifting southward into NM and ejecting/merging with
the broad central plains upper low. Snow will ramp up quickly
Sunday evening across the Continental Divide, particularly the
southwest mountains as upper forcing moves in. As the upper low
intensifies, it pulls H7 winds from a more northeast upslope
component across the plains with snow spreading into the east facing
slopes of the southeast mountains during the evening. However with
models and ensembles converging on a more westward storm track with
the energy dropping through the Great Basin, this has continued the
trend towards lighter QPF for the southeast mountains and adjacent I-
25 corridor. In fact, strong northerly winds (downsloping) off the
Palmer Divide on Monday really diminish precipitation for southern
El Paso and Pueblo counties. The central plains upper low wobbles
back westward as energy rotates around its northern and western
side. This tightens the pressure gradient and brings the potential
for near high wind criteria gusts on Monday across portions of the
plains. Deformation band also shifts westward setting up a band of
rain/snow showers across the plains on Monday with the snow level
wavering around 5500 to 6kft. This band looks less consolidated in
latest runs, though Palmer Divide and to a lesser extend the Raton
Ridge could see some snow accumulations Monday into Monday evening,
especially for northern areas. For now have hoisted Winter Weather
Advisories for the southern mountains south of highway 50 where the
National Blend of Models progs greater 50 to 70% chance of greater
than 6 inches of snow across the higher elevations of the southern
Sangres and eastern San Juan mountains. This may end up being a
marginal event for some of our southern mountains, but given this is
a period where travel will be ramping up for the Holiday week, have
decided to include these areas in the advisory as passes will likely
see some travel impacts. Greater uncertainty exists to the north
across the Pikes Peak region where snowfall amounts in going
forecasts are still prone to change. Given the wrap around on
Monday, heaviest accumulations will be delayed until after Sunday
night and have opted to hold off on Winter Weather Advisories at
this time. While NBM shows fairly high probabilities (50 to 70%)
chance of 4 inches or more of snow, these probs decrease to around
40 percent or less for the 6 inches or more category. So there is
more spread in the solutions up that way which is likely a
reflection on the differences in timing on how quickly the upper low
pulls off to the east. Given the later start time to the event, will
let another model cycle come in before deciding on the need for
advisories for Teller and northern El Paso counties. Either way, do
expect some travel impacts across that area for the Sunday
night/Monday morning travel period, especially as winds increase
Monday morning with the potential for some blowing snow.
For the remainder of the southeast plains, this still looks like a
warm system with precipitation falling as rain. EC Ensembles show a
20-30% prob of wind gusts exceeding 58 mph across northern and
eastern El Paso and Kiowa counties with higher probs (up to 60%)
along the Ridge of the Raton Pass. Canadian wind gust swaths also
indicate this potential though more so to the north. However GFS,
HRRR and NAMNest are keeping gusts below high wind criteria.
Overall, there is not enough confidence for a high wind watch at
this point.
System pulls away from the area Monday evening with dry weather and
rebounding temperatures for Tuesday and Wednesday. The next storm
system will bring another round of snow during the Thanksgiving
Holiday Weekend along with much colder temperatures, especially next
Friday and Saturday when highs may top out in the 30s. -KT
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 247 PM MST Sat Nov 18 2023
VFR conditions are expected to prevail for all TAF sites (KALS,
KCOS, and KPUB) throughout the forecast period. Winds will be mainly
diurnally driven at all terminals. SHRA is possible in and around
the vicinity of all stations through this evening, with less of a
chance at KCOS, and especially KPUB. Highest confidence of SHRA
occurrence with be at KALS until 03Z, and then tomorrow after 18Z.
-SHRASN could be onstation at KALS after 23Z. FROPA will occur at
KCOS and KPUB around 02Z, although this may occur sooner, where
winds out of the SE at both locations is expected to switch to a
NNW`ly direction, then weaken tonight. They will eventually switch
around to the SE at KCOS and ESE at KPUB by later in the afternoon
tomorrow, towards the end of the forecast period. Winds at KALS will
be primarily out of the SW, and then weaken to become L&V by late
evening. They will begin to pick back up out of the SW at KALS by
afternoon tomorrow and come around to the WNW as -SHRASN chance
increases.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 AM Sunday to 5 AM MST Monday for
COZ066-068.
Winter Weather Advisory from 5 PM Sunday to 11 PM MST Monday for
COZ073>075-080.
&&
$$
UPDATE...MOZLEY
SHORT TERM...STEWARD
LONG TERM...KT
AVIATION...STEWARD