Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/08/23
Area Forecast Discussion
National Weather Service Cheyenne WY
815 PM MST Tue Mar 7 2023
.UPDATE...
Issued at 806 PM MST Tue Mar 7 2023
Light snowfall continues across portions of southeast Wyoming this
evening. Latest radar imagery shows returns across Laramie County,
however they have been quickly diminishing over the last few
hours. RAP/HRRR forecast soundings continue to show drying aloft
headed into later tonight, especially in the -12C to -18C layer.
Low level saturation remains and will even increase in spots
tonight leading to similar conditions as last night across the
I-80 corridor from Laramie to Cheyenne to Sidney. Dense fog and
freezing drizzle will be hazardous to those out on area roadways,
especially headed into the morning commute with reduced visibility
and a light glaze of ice. Therefore, decided to issue a Winter
Weather Advisory beginning later tonight running through Wednesday
morning. Mainly stuck to the South Laramie Range and Laramie
County in southeast WY, but will need to monitor if these
conditions spread into the southern NE Panhandle.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 315 PM MST Tue Mar 7 2023
A dreary day across much of the CWA between snow showers, fog,
and freezing drizzle. Visible satellite shows low stratus across
parts of the Interstate-80 corridor and the Nebraska panhandle. For
the most part, fog has burned off, although some patchy, but dense
fog lingers in the southern Laramie Range and foothills. Some
scattered snow showers are possible this afternoon, mainly for the
high terrain, but some showers could sneak into the plains. Not
expecting much in the way of impacts or accumulation with these
showers.
Late tonight into tomorrow morning looks like it could be a repeat
of what was seen early this morning, with a good set-up for a period
of dense fog/freezing drizzle and low stratus. Winds will be light,
but with an easterly component, which is favorable for the
development of dense fog and low stratus in and around the Cheyenne
area. Moist southwesterly 700 mb flow into the region will support
RHs above 80 percent for much of the CWA. This gives decent fog and
low stratus potential for most locations. However, the densest fog
will likely be found in the south Laramie Range, Laramie County, and
north of the Pine Ridge in Nebraska, where upslope flow will
dominate. Another potential hazard will be freezing drizzle, mainly
in Laramie County and the southern Nebraska panhandle. Model
soundings continue to show a shallow saturated profile near the
surface between -10C and 0C. Did not have the confidence at this
time to issue a Winter Weather Advisory for the freezing drizzle as
some models did not show as strong a signal for it in the southern
panhandle. Later shifts may have to pull the trigger on an Advisory
once fog starts to develop. Best timing to see fog/freezing drizzle
will between 06Z tonight and 18Z tomorrow morning.
Between the fog, clouds and freezing drizzle in the morning,
Wednesday will be another chilly and gloomy day. Snow chances will
increase through the afternoon, and become more widespread Wednesday
night as an upper-level shortwave pushes through. Decent lift
combined with the moist southwesterly flow aloft with contribute to
light snow overnight with some accumulation. Greatest accumulations
will be along and north of the Pine Ridge. These locations could see
between 2 and 4 inches of snow, with some localized areas up to 5
inches. Winter Weather Advisories may be needed for Niobrara
County, northern Sioux County, and maybe Dawes County. The Snowy
and Sierra Madre Ranges will likely pick up around 6 inches with
this storm. Other locations across the plains may see up to an
inch of snow by Thursday afternoon.
Snow tapers off on Thursday, and behind it, a marginal chance for
high winds for the wind prones. An inverted surface trough will
cause MSLP gradients to steepen along and west of the Laramie Range.
This will lead to approximately 50 kt winds aloft with great
downward omegas over the Laramie Range. At this point, winds don`t
look strong enough to reach high wind criteria, but gusts to 55 MPH
look possible. Luckily, this looks like a very short lived event
during midday Thursday, as the surface trough moves off to the east
rather quickly.
.LONG TERM...(Thursday night through Tuesday)
Issued at 315 PM MST Tue Mar 7 2023
Main Weather Highlights:
1) Periods of accumulating mountain and valley snows possible
throughout the long term forecast period. The best chances for
consistent accumulating snow will be in the Sierra Madre and Snowy
Mountain Ranges with lesser confidence across the valley locations.
2) Widespread breezy conditions expected across much of SE Wyoming
and the Nebraska Panhandle. Some periods of elevated to high winds
will be possible across the wind prone areas, I-80 summit and
portions of Carbon County.
3) Temperatures will gradually warm Friday and Saturday before a
weak cold front knocks temperatures back down on Sunday. Still
looking like temperatures overall should be near or slightly above
seasonal normals for this time of year.
Overview: A consistent progressive zonal flow with weak vorticity
lobes is progged to bring increased winds, and low end valley and
mountain PoP chances for much of SE Wyoming. With the expected
consistent westerly/downsloping winds and weak ridging aloft,
temperatures should warm nicely for areas east of the Laramie Range
Friday and Saturday. Temperatures should climb into the 50s and a
few locations across the Nebraska Panhandle could approach 60F!
Precipitation chances remain on the low end as weak disturbances and
limited moisture availability will keep most of the region dry with
just some low end chances of valley snow showers occurring primarily
across Carbon County with higher end chances for the mountains.
Discussion: Both deterministic models and in-house guidance are
honing in on the potential for high winds to develop across the wind
prone areas late Friday night into Saturday. Mountain wave activity
will possible and if this materializes, some elevated to strong wind
gusts could occur over the south Laramie Range foothills and
portions of the I-25 corridor Saturday afternoon. Parameters aren`t
impressive for high winds to occur with the CAG-CPR 850 and 700 mb
gradients holding between 50-55m range respectively. Strong 700mb
winds between 55-60kt are collocated under stripes of strong
downward omega values across Carbon County, the Arlington wind
prone, and the Laramie Range. The window of greatest concern will be
Friday night beginning across the wind prone areas and Carbon County
and then transition to the Foothills and I-25 corridor Saturday,
pending the severity of the mountain wave activity. If trends hold,
High Wind highlights for the wind prone areas and Carbon County may
be needed.
The breezy conditions should continue in Sunday but not looking like
an one area should see high winds at this time, although a brief
surge in the wind gusts may occur with a weak frontal passage
expected. Temperatures should respond with the warm downsloping
winds Friday and Saturday with temperatures east of the Laramie
Range and into the Nebraska Panhandle jumping into the 50s.
With weak disturbances moving through, mountain snow showers will be
a common occurrence throughout the majority of the long term forecast
period. Limited moisture and upper level dynamics will mainly keep
PoP chances tied to areas of upslope with added orographic
enhancement. Some higher valleys across Carbon County could see some
snow showers that could bring minor accumulation to these areas.
Areas east of the Laramie Range should remain dry until the
strongest disturbance aloft moves through and drags a weak frontal
boundary north to south across the area on Saturday. Some light
precipitation may occur but not expecting much in the way of
accumulation.
Into next week, models are in agreement of building a large
amplitude ridge across the western CONUS allowing for dry conditions
to develop with warming temperatures.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 430 PM MST Tue Mar 7 2023
Tricky aviation forecast for this evening as guidance showing
ceilings lifting. Well past peak heating for the clouds to break
out...so went with a persistence forecast...keeping KSNY down.
Best confidence in KCYS and KCDR as latest HRRR guidance showing
lowering ceilings through the evening hours. Less confidence in
KAIA...KBFF and KSNY. After 06Z however...looks like all airports
east of the Laramie Range will go down to IFR/LIFR. FZDZ an issue
at KCYS and KSNY with low ceilings.
Further out...snow looks to become widespread Wednesday
afternoon/evening for IFR/LIFR conditions to be common.
&&
.FIRE WEATHER...
Issued at 315 PM MST Tue Mar 7 2023
No fire weather concerns are expected for the next week due to
a cold, unsettled weather pattern with accumulating snow. Winds
are expected to increase across southeastern Wyoming on Thursday
and remain strong through Sunday. Temperatures warm Friday and
Saturday.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 10 AM MST Wednesday for WYZ116>119.
NE...None.
&&
$$
UPDATE...MB
SHORT TERM...SF
LONG TERM...AW
AVIATION...GCC
FIRE WEATHER...AM
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1019 PM EST Tue Mar 7 2023
.SYNOPSIS...
Cooler air sets up tonight into Wednesday with high pressure to our
north. Moisture and rain chances gradually return with another
low pressure system and cold front late Thursday through Friday,
followed by cool high pressure on Saturday. A low pressure
system may affect the region Sunday into Monday.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 1000 PM EST: Starting to see mountain wave cirrus clouds
develop across portions of the mtns and NC Foothills tonight. Have
blended in some higher cloud cover to account for these increasing
clouds. No other significant chances were needed.
Otherwise, CAMs depict low-level CAA peaking before midnight
tonight, but tapering off only very slowly leading up to daybreak.
So winds will remain elevated throughout much of the overnight, and
especially across the mountains, breezy conditions are expected
right up until daybreak. After dawn, low-level winds will veer more
NE, cutting off the better CAA and allowing for winds to decline
sharply through Wednesday morning. Another round of deep mixing is
expected tomorrow afternoon, but RAP and GFS profiles don`t depict
as deep of a mixed layer developing, so although dewpoints are
expected to crash again, winds are not expected to be nearly as
high. By mid-afternoon, as the axis of a synoptic ridge sharpens
over the Ohio Valley, thickening cirrus should begin streaming
across the Appalachians and into the western Carolinas...but
isentropic ascent fails to gain much traction until after the end of
the forecast period Wednesday evening, so no mentionable PoPs are
forecast at this time.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 245 PM EST Tuesday: The short-term fcst picks up at 00z on
Thursday with upper ridging building to our west and very broad
upper trofing to our east over the Atlantic. Towards the end of
the period late Friday, another upper trof/closed low will amplify
over the Ohio River Valley and help suppress the upper ridge over
our area. At the sfc, broad Canadian high pressure will be centered
well to our north with NLY to NELY low-lvl flow still over our CWA.
On Thursday, another low pressure system will begin to develop over
the southern Plains and will lift a moist warm front towards our
fcst area from the south. This will result in increased cloud cover
for much of the day, especially across our western zones. Precip
chances also increase as the day wears on with likely PoPs fcst
over our western-most zones by Thursday evening. The warm front
will lift north of our CWA by early Friday with a fairly vigorous
cold front pushing thru the CWA quickly thereafter. The front should
be east of our fcst area by late Friday with broad Canadian high
pressure spreading back over the area in its wake. We`re still not
expecting enough QPF to cause any significant hydro issues for our
area, with most locations expected to get 0.75 inches or less.
Otherwise, high temperatures should approach climatology on Thurs,
and remain at least a category below climo for Fri.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 225 PM EST Tuesday: The extended fcst picks up at 00z on
Saturday with upper trofing passing to our north and suppressing
an upper ridge that has been over the SE CONUS for a number of
days. Over the next 24 to 36 hrs, the trof axis will move off
the Atlantic Coast as near-zonal upper ridging builds back over
the SE. Towards the end of the period early next week, another
upper trof/closed low digs down over the Great Lakes and helps
suppress the upper ridge over our area. At the sfc, a vigorous
cold front will push thru the fcst area quickly on Friday and
should be east of our CWA by the start of the period late Fri/
early Sat. In its wake, broad Canadian high pressure will spread
back over the area from the NW producing gusty winds as the pressure
gradient tightens. The high will be transient and is expected to
slide offshore late Sunday. As that happens, another sfc low is
progged to spin up to our west and translate eastward quickly.
At this time, the track of this system is still fairly uncertain,
but most of the extended guidance has the low moving over our area
early Monday and then off the Atlantic Coast late Mon/early Tues,
with drying high pressure moving in behind it. This system will
likely bring another round of widespread precip to our fcst area
late Sun/early Mon and could produce some snow showers over the
NC mtns, especially at elevations above approx 3500 ft. Otherwise,
temperatures will start out near climatology on Sat and then cool
to below climo for the rest of the period.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Dry and VFR through the 00Z TAF fcst period
as sfc high pressure builds in behind a departing cold front. Low-
end wind gusts are expected to continue through late tonight before
tapering off a few hours prior to daybreak. Winds will be NW at KAVL
overnight with N/NNE winds east of the mtns. KAVL has the best
chance to see SCT to BKN cirrus overnight while the rest of the
terminals remain SKC or FEW250. With such a dry airmass in place,
fog formation is not expected overnight at the terminals. Winds east
of the mtns will turn more NE throughout Wednesday morning before
gradually turning SE Wednesday afternoon and evening across the SC
Upstate terminals. KHKY and KCLT will continue to see NE winds
through the end of the 00Z TAF fcst period. Winds will remain NW at
KAVL Wednesday. Upper-level cirrus will gradually increase Wednesday
afternoon into Wednesday night as upper-level shortwaves track
across the western Carolinas.
Outlook: VFR conditions continue into Thursday. The next round of
rainfall arrives Thursday night, with associated flight restrictions
possible. VFR conditions return through at least the first part
of Saturday.
&&
.FIRE WEATHER...
Cooler temperatures are expected Wednesday as surface high pressure
builds in behind the departing cold front. Dewpoint temperatures are
expected to plummet again, producing minimum RH values in the teens
and lower 20s across much of the fcst area Wednesday afternoon. With
continued dry fuels, another Fire Danger Statement may be needed for
Wednesday. However, calmer winds are expected on Wednesday and this
may act to offset the fire danger potential somewhat.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...DEO
NEAR TERM...AR/MPR
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...AR
FIRE WEATHER...AR
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
958 PM EST Tue Mar 7 2023
...New UPDATE...
.UPDATE...
Issued at 949 PM EST Tue Mar 7 2023
Winds continue to be elevated across much of the area tonight,
especially the central and southern TN valley locations. They are
beginning to lessen in the north where high pressure is beginning
to build in. But down valley pressure gradients will likely remain
high enough to keep those elevated winds going through the
overnight areas. The latest HRRR runs are trending warmer in the
south for overnight lows while maintaining temperatures between 28
degrees and freezing in the north where the freeze warning is
currently located. Wise county is already at 34 degrees with some
lower elevation areas in Virginia around 40. If winds slacken
further and cloud cover doesn`t increase, then I believe the
freeze warning will be ok. Otherwise, no significant changes to
the going forecast. Updated zones and freeze warning products have
been issued.
&&
.SHORT TERM...
(This evening through Wednesday)
Issued at 328 PM EST Tue Mar 7 2023
Key Messages:
1. Freeze warning for Wednesday morning in northeast TN counties and
southwest VA.
2. Dry weather and low relative humidities continue through
Wednesday. Increasing clouds ahead of a passing system.
Discussion:
Gentle ridging at surface and aloft will continue to be
the theme overnight and into Wednesday. A weak 500 mb shortwave will
pass through to our southwest, and guidance seems to be consistent
and persistent about keeping precipitation out of the area in the
short term. Expecting dewpoints to drop off tonight into the teens
in northeast Tennessee and Virginia, upper 20s in the southern
valley. A strong inversion with increasingly dry air aloft will
allow for good radiational cooling, and so have upgraded the
Freeze Watch to a Warning for northeastern Tennessee and into
Virginia. Further south towards Knoxville not expecting a freeze,
and dewpoint depressions would indicate frost formation is
unlikely.
Wednesday looks to be another dry day, with temperatures cooler
than today. Expecting winds to calm into the day on Wednesday, but
relative humidities will drop into the upper 20s over a
widespread portion of our area. Clouds will steadily build
throughout the day becoming overcast in the afternoon.
&&
.LONG TERM...
(Wednesday night through next Tuesday)
Issued at 328 PM EST Tue Mar 7 2023
Key Messages:
1. Increasing rain chances Thursday, peaking Thursday night and
exiting Friday with a cold frontal passage.
2. Below normal temperatures through the weekend into early next
week, with rain chances returning Sunday.
Discussion:
Isentropic lift aloft with top-down moistening will ensue Wednesday
night across southern portions of the area. At the surface, a front
will be stalled to our south, remaining nearly stationary as a low
pressure system tracks across the Mid-MS region. A strengthening
southerly 850 mg flow will override the front, bringing light precip
to southern sections by Thursday morning, spreading north through
the day. Best QG forcing arrives late Thursday night/Friday morning
ahead of the cold front, which sweeps through around midday. One
uncertainty with this system is where the axis of highest QPF
will be, as the GFS focuses on southern sections, and the NAM
prefers northern sections. Either way, it doesn`t look like a
significant rain producer, with high end amounts of a half inch to
one inch possible. The presence of the upper trough over the
central Appalachians may keep a few showers going into Friday
evening behind the cold front.
Temperatures will be dropping below normal on Friday night, and
remain so through the rest of the forecast period as we get a series
of weak shortwave troughs within a broader trough that bring
reinforcing shots of cold air. Highs will generally be in the mid
40s to mid 50s each day, with overnight lows in the 30s to lower
40s. The spread of NBM members remains quite large however, adding
uncertainty to the forecast.
Confidence remains low on the system that is expected to affect the
area on Sunday. The GFS shows a very broad trough with channeled
vorticity crossing the area on Sunday, with a weak surface low near
the Gulf Coast. The ECWMF has a more amplified pattern with a low
that tracks across the TN Valley region. These differences will
impact our precipitation types and QPF amounts, so confidence in
these details is low at this time. A rain/snow mix will continue to
be mentioned for northern sections and the mountains, with only rain
elsewhere.
&&
.AVIATION...
(00Z TAFS)
Issued at 632 PM EST Tue Mar 7 2023
VFR conditions will prevail through the period. Winds will remain
elevated through the night at KTYS and KCHA as high pressure
builds in to the north and gradients down the TN valley remain
high. Some evidence in guidance that gusts to 15-17kt will
continue at KTYS but think a steady 10kt is more likely so I stuck
with that. High and mid clouds increase after daybreak tomorrow.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 42 61 46 56 / 0 10 20 60
Knoxville McGhee Tyson Airport, TN 37 57 41 58 / 0 0 10 50
Oak Ridge, TN 37 57 41 58 / 0 0 10 50
Tri Cities Airport, TN 30 53 35 60 / 0 0 0 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Freeze Warning from 1 AM to 9 AM EST Wednesday for Claiborne-
Hancock-Hawkins-Northwest Carter-Northwest Greene-Sullivan-
Washington TN.
VA...Freeze Warning from 1 AM to 9 AM EST Wednesday for Lee-Russell-
Scott VA-Washington VA-Wise.
&&
$$
SHORT TERM...CD
LONG TERM....DGS
AVIATION...CD
Area Forecast Discussion
National Weather Service Norman OK
546 PM CST Tue Mar 7 2023
...New AVIATION...
.SHORT TERM...
(This evening through Wednesday)
Issued at 404 PM CST Tue Mar 7 2023
As of 3PM, a weak surface low was centered near Bridgeport, TX and
a quasi-stationary frontal boundary extended from there to
Burneyville to Centrahoma. Cold temperatures (in the 40s) are
currently observed over much of northern, west-central and into
southwest Oklahoma. Ahead of the boundary, the Burneyville and
Centrahoma mesonet stations have temperature readings of 76 deg F
and rather moist boundary layer is also present with dewpoint
temperatures in the mid/upper 60`s. Aloft, our area is positioned
under the backside of an upper ridge with WSW flow at H500.
Isolated to scattered showers and thunderstorms are forecast to
develop along/ahead of the frontal boundary late afternoon due to
frontogenetical lift as SBCAPE increases to 1500-2000 J/kg over a
small portion of S/SE Oklahoma (along/east of Love County to
southern Pontotoc County). With low 0-1km shear, not expecting
tornadoes to be much of a threat especially with weak dynamic
lift. However, a weak/isolated tornado cannot be ruled out with
the HRRR showing effective shear around 60 knots. The primary risk
with these initial afternoon/evening storms will be large hail up
to the size of quarters, and damaging wind gusts up to 60 mph.
As a subtle shortwave reaches the Texas panhandle this evening,
a broader area of showers and thunderstorms are expected to
develop along a zone extending from western north Texas to central
Oklahoma later this evening. Though surface temperatures will be
cool, elevated instability (~500-1000 J/kg) may be enough to
produce small hail with a few of these thunderstorms. As we
approach midnight, the concern will transition to heavy rainfall
and the risk of flash flooding. Given the marginal QPF amounts
(1-2.5" possible through tomorrow) compared to criteria, a Flood
Watch has not been issued.
Tomorrow will be cloudy with north winds with showers/thunderstorms
likely. Models have continued to struggle with the temperatures,
but given the conditions just mentioned and latest model
performance, opted to lower highs tomorrow towards CONSSHORT.
Thompson
&&
.LONG TERM...
(Wednesday night through next Monday)
Issued at 449 PM CST Tue Mar 7 2023
A mid-level trough swings across the central Rockies on Wednesday
night, resulting in increased isentropic lift (both in aerial
coverage and depth). This will allow high rain chances for rain
to expand over much of Oklahoma and parts of western north Texas
(generally east of Hwy 81). With moderate and elevated instability
prog`d, thunderstorms are also possible overnight Wednesday and
into Thursday morning. Guidance struggles with the evolution of
this trough and surface wind field. Temperatures continue to be
challenging aspect of the forecast. For instance, the 12Z ensemble
has solutions ranging from 60 to 73 degrees for Thursday at OKC.
For now, opted to go with CONSRAW with highs mainly in the 60s for
Thursday. The antecedent cold front than moves through on
Thursday and rain chances shift SE throughout the day with rain
exiting by Thursday evening. Will see a brief dip in temperatures
on Friday and highs will dip into the 50s and low 60s on Friday.
A lee-surface cyclone then develops Friday night and Saturday and
strong WAA will lead to much warmer temperatures on Saturday, with
highs ranging from the mid-60`s (northeast OK) to low 80`s
(western north TX). The front associated with this system is
prog`d to move through on Saturday night, which will bring a
chance for showers/storms Saturday night into Sunday morning. A
downward trend (though brief) in high temperatures appears
possible Sunday into early next week.
Thompson
&&
.AVIATION...
(00Z TAFS)
Issued at 540 PM CST Tue Mar 7 2023
Widespread MVFR restrictions expected most of the forecast valid
period. Some IFR conditions also expected especially across
central Oklahoma this evening and overnight. Scattered RA and
isolated TSRA expected as well, with activity increasing toward
and after 03Z and lasting through 12Z from southwest and west
central portions of Oklahoma into central Oklahoma. After an
overall lull expected after 12Z, redevelopment of RA and a few
TSRA looks plausible across western north Texas and southwest
Oklahoma by 18Z then spread eastward through the afternoon
tomorrow.
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 43 54 50 66 / 80 40 70 60
Hobart OK 41 54 46 68 / 50 30 60 20
Wichita Falls TX 46 54 51 69 / 60 70 70 50
Gage OK 34 51 40 66 / 20 20 30 10
Ponca City OK 44 54 46 60 / 30 20 60 70
Durant OK 54 60 53 67 / 40 70 70 80
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
SHORT TERM...01
LONG TERM....01
AVIATION...11
Area Forecast Discussion
National Weather Service Pueblo CO
313 PM MST Tue Mar 7 2023
.SHORT TERM...(This evening through Wednesday)
Issued at 253 PM MST Tue Mar 7 2023
Key messages:
1) Freezing Drizzle/Freezing Fog impacts likely across El Paso
county tonight into Wednesday morning with slick roads possible by
the morning commute
2) Critical Fire Weather conditions continue through early evening
across the San Luis Valley and will return again on Wednesday for
the same area
It`s been a challenging forecast today with clouds holding strong
across the southeast plains and temperatures struggling to make it
much above 30 degrees. Models had a hard time resolving the
magnitude and persistence of this event, and suspect it is
under-doing the extent of saturation that occurs again tonight,
particularly across the southeast upslope favored regimes of the
Pikes Peak region. Latest HRRR runs are coming in more deeply
saturated tonight across the plains with classic freezing drizzle
sounding profiles with saturation in the above -10C range. 12z
model suite was a little more liberal with some very light QPF
focused on the El Paso county area tonight through Wednesday
morning. Given that temperatures haven`t warmed above freezing yet
across El Paso county, suspect that road temperatures will have an
easier time cooling tonight below freezing. This, in combination
with an earlier onset and longer duration of saturation, will allow
some light ice accumulation to occur more easily, especially on
elevated roads, side streets and sidewalks. Therefore will be
hoisting a Winter Weather Advisory with the afternoon package for El
Paso county beginning around 11 PM tonight and continuing through 11
AM tomorrow morning. There are still some uncertainties with this
potential high impact but lower side of the spectrum confidence
event. Upslope is weaker overall tonight which may slow or delay
cloud condensation growth at the surface some and limit QPF/ice
deposition a bit. But HRRR and NAMNest suggest a slight increase in
southerly wind speeds between 12z-15z Wed, and there are some MSLP
rises occuring across the eastern plains late tonight into Wed
morning which could justify a slight increase in winds towards
morning as this pressure wave makes its way westward towards the
mountains. All in all, there are enough signals to nudge towards
raising awareness for the potential of slick and hazardous roads
across the Pikes Peak region for the Wednesday morning commute. Fog
could become dense at times overnight as well leading to poor
visibility.
Another area of concern overnight will be the lower east slopes of
the Wet Mountains and portions of eastern Fremont county. Upslope
component looks a little weaker in these areas given a more
southeasterly component to the wind direction...so will hold off on
expanding advisories for now. But these areas will need monitoring
closely. Southeast plains, especially along and north of the
Arkansas River could also see some light ice accumulation from
freezing drizzle, however models show a few degrees T/Td spread at
the surface which could keep the event more stratus than fog/fzdz.
However if models are under-doing the saturation, then it is possible
for some light icing and slick conditions on bridges and overpasses
by morning. Again, will need to monitor trends closely tonight and
make adjustments as needed.
Otherwise, temperatures tomorrow are likely to fall short of the
optimistically warm NBM and have undercut them quite a bit across
the plains. Clouds are likely to hang in tight across the plains
most of the day. Out west, breezy southwest winds will spread back
down into the lower mountains and valleys. Red Flag conditions will
likely return across the San Luis Valley and have upgraded the Fire
Weather Watch to a Red Flag Warning for tomorrow. -KT
.LONG TERM...(Wednesday night through Tuesday)
Issued at 253 PM MST Tue Mar 7 2023
Key Messages:
1) Light mountain snow Thursday. Critical Fire Weather conditions
over the plains with gusty west winds.
2) Calm weather on the plains through Saturday, with warming
temperatures. More light snow possible over the Continental
Divide. Cool-down possible Sunday.
Wednesday Night-Thursday...
A quick-moving upper-wave will pass over the area late Weds into
Thursday, with breezy west winds setting in behind it. The passing
area of lift will potentially allow for a brief shot of light snow
to parts of the Continental Divide, while over the plains a weak
northerly surge of air will move in. While some of the higher
mountaintops will remain cold, the rest of the area will warm
considerably, with high temperatures expected to climb into the high-
50s over most of our southeast plains, while the rest of our lower
terrain stays in the low-50s. Gusty west winds aloft will mix down
towards the surface, with much of the area experiencing gusts of 25-
30 knots. Areas of particular concern will be the mountains/plains
interface and gap-flow regions, where gusty west-northwest
crosswinds could cause some hazardous travel for the I-25 corridor
during early-mid afternoon. Additionally, as temperatures increase
with the return of more widespread sun, critical fire weather
conditions will be possible over most of the eastern plains. Future
highlights, should there be any, will largely depend on fuel status.
Meteorologically-speaking, though, Red Flag Criteria will be
possible anywhere that retains gusty winds for a few hours in the
afternoon, which will be most of our eastern plains.
Friday Onwards...
Zonal flow will set in aloft Friday and Saturday, with gusty south
winds setting in at the surface over our eastern plains. Gusty winds
will continue, and near-critical fire weather conditions may be
possible in some places, but current long-term guidance suggests
that humidity will increase enough to avoid further highlights, at
least for now. Meanwhile, over parts of the Continental Divide, the
westerly flow aloft may bring in enough moisture for more mountain
snow, given the continued orographic support. Chances look good for
a few inches near the Sawatch Range. Temperatures will warm further,
with high-60s over the plains Friday and 70s on Saturday, with the
higher terrain in the 50s-60s. Is it spring already? A weak upper
disturbance is expected to pass quickly to our north early on
Sunday, which will once again give us another chance at light snow
for our mountains. Meanwhile, a possible cold front across the
plains may knock temperatures back down closer to seasonal averages
for Sunday afternoon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 253 PM MST Tue Mar 7 2023
MVFR to IFR cigs will lower into the IFR to LIFR range across the
southeast plains this evening with -FZDZ possible at both KCOS and
KPUB overnight through Wednesday morning. A light accumulation of
ice will be possible, especially across El Paso county including
KCOS, along with IFR to LIFR vis in FZFG. Visibility will improve by
17-18z with cigs returning to MVFR for both KCOS and KPUB for the
afternoon.
KALS will continue breezy with gusts up to 35 kts possible through
early evening. Winds will decrease towards 01z and remain southerly
through the night before increasing again from the southwest at 20-
35 kts by late Wednesday morning. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 6 PM MST this evening for COZ224.
Red Flag Warning from 11 AM to 6 PM MST Wednesday for COZ224.
Winter Weather Advisory from 11 PM this evening to 11 AM MST
Wednesday for COZ084-085.
&&
$$
SHORT TERM...KT
LONG TERM...GARBEROGLIO
AVIATION...KT