Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/15/23
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
912 PM CDT Thu Sep 14 2023
.UPDATE...
Issued at 904 PM CDT Thu Sep 14 2023
Still some lingering light showers across the eastern CWA this
evening, and the HRRR has backed off a bit recently on the widely
scattered redevelopment it had showed. Will maintain the 20 POPs
that were inserted earlier this evening until around 06Z and see
where things look at that point. Otherwise, aside from tweaks to
POPs and sky grids, no significant changes to the forecast for the
overnight period.
&&
.SHORT TERM...(This Evening through Friday Night)
Issued at 236 PM CDT Thu Sep 14 2023
A cold front is draped northeast to southwest from Roberts to Lyman
counties this afternoon. It will continue to push east through the
evening. Thunderstorms have begun to develop in the warm sector
ahead of the front. Areas near Watertown may see a couple of storms
before the front exits, but with very little instability available
isolated activity is all that`s expected in this forecast area. No
severe storms are forecast.
The HRRR still shows near-sfc smoke from Canadian wildfires moving
in to central SD behind the showers later this evening and into
Friday morning. It looks like a more potent shortwave embedded in
the upper trough will help to drag the smoke south Friday. Also
increased sky cover to account for the elevated smoke through 18z
Friday, but may need to extend it through Friday night. Dry
conditions are forecast for Friday with high pressure settling in
Friday night.
.LONG TERM...(Saturday through Thursday)
Issued at 236 PM CDT Thu Sep 14 2023
The temperature roller coaster continues, rounding the top of the
hill Monday and Tuesday of next week with highs mainly in the 80s. I
wouldn`t be surprised to see a couple of 90 degree readings Monday
over central SD, and about 10 degrees above normal for this time of
year. Most locations will be about 10 degrees below record highs
Monday. Forecast solutions are pretty consistent on the overall
trend beyond Tuesday with moderating temperatures and increasing
dewpoints.
Getting to the overall forecast pattern, there are some differences.
We`ll start out under a mostly clear sky Saturday morning as the
500mb trough exits east. The main concern weather wise may be how
much smoke is still around near the surface, streaming in from the
Canadian wildfires from the northwest. The 12Z run of the HRRR still
keep the potential going into Saturday morning. Given the steering
direction, most of the the smoke should shift east of our area by
Sunday afternoon. Expect the 500mb ridge centered over WY/eastern MT
at 06Z Sunday to move across the Dakotas Sunday before zonal to
northwest flow returns Sunday night. This is where the forecast gets
a little more uncertain, with the intensity and location of a couple
of troughs/lows at 500mb over southwestern Canada and off the CA
coast. Either way, confidence is high in zonal to southwesterly flow
should return for the Northern Plains by 00Z Wednesday. Thursday
should bring us southwesterly flow at 500mb, but the low could be
anywhere from eastern WY to western ID. The large differences and
lack of confidence is showing up in nearly a 15 degree spread in the
high temperatures for Thursday (25th-75th percentile from NBM). Will
continue to go with the a blended solution, with the potential for
significant changes for later Wednesday and beyond. The highest
chances for precipitation looks to be Thursday, and even then only
in the 30% range.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 636 PM CDT Thu Sep 14 2023
Terminals KABR,KATY,KPIR,KMBG
The SHRA/TSRA activity from earlier this afternoon has departed
the region to the east, leaving behind mid and high clouds.
Generally VFR conditions are forecast through the period. Will be
watching a band of smoke (FU) moving southeast into north central
SD this evening, which may temporarily bring MVFR VSBY to KMBG.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...TMT
SHORT TERM...Wise
LONG TERM...KF
AVIATION...TMT
Area Forecast Discussion
National Weather Service Cheyenne WY
540 PM MDT Thu Sep 14 2023
.SHORT TERM...(This evening through Saturday night)
Issued at 117 PM MDT Thu Sep 14 2023
Cold front that moved through the area overnight is now located
across west central Nebraska into northeast Colorado through
northwestern Colorado this afternoon. Radar showing light to
moderate rain across the central CWA from roughly the Snowy
Range...northeast into the northern Panhandle.Mesowest
observations showing some pretty good QPF amounts at 0.1 to 0.2
inches the past 6 hours on northern facing slopes. Outside of
these north facing slopes...precip amounts have been generally
less than 0.1 inches.
Look for rain to come to a pretty quick end this evening as front
continues to drop south into southern Colorado. HRRR and RAP
simulated radar showing area of precip sliding southwest into
Nebraska and northwestern Kansas this evening. By 06Z or so...all
rain should be coming to an end.
Pleasant weather Friday with sunny skies and afternoon
temperatures in the 60s and low 70s. One concern for Friday night
into Saturday morning will be the possibility of a frost event at
Laramie and Saratoga. Getting low 30s for Saturday morning at
Laramie and Saratoga. With clearing skies and light
winds...definitely looking like frost headlines and possibly
freeze headlines will be needed for these two zones. GFS 700mb
temperatures +4 to +6C Friday will climb to +8 to +10C Saturday.
Looking at 70s across southeast Wyoming and low 80s in the
Panhandle.
.LONG TERM...(Sunday through Thursday)
Issued at 117 PM MDT Thu Sep 14 2023
Overall, the weather pattern through most of the long term looks
pleasant with dry conditions and warm fall days. By mid next week,
the pattern changes with wetter and cooler weather possible by the
end of the week.
Upper-level ridging over western CONUS will create an excellent fall
weekend across the CWA. Starting on Sunday, warm 700 mb temperatures
ranging from +8 to +12C will hover over the region. This will lead
to above average temperatures, about 5 to 10 degrees above normal
for most locations. Highs will be in the 70s and 80s during the
afternoon, which will continue into Monday and Tuesday as the warm
700 mb temperatures sit overhead. Could see a tad bit breezier
conditions across Wyoming on Monday and Tuesday as the ridge aloft
flattens out into more zonal flow. Also cannot rule out an isolated
high terrain shower or two Monday and Tuesday as weak vorticity
maximums pass through the CWA. However, low-levels are quite dry so
confidence in any showers developing is low. Overall, the time
period between Sunday and Tuesday is expected to be dry with mostly
sunny skies.
The pattern begins to change a bit Wednesday as a strong trough
begins to push south into western CONUS from Canada. As models
currently stand, most of Wednesday will be dry as the trough is
still far enough off to the northwest. By Wednesday evening, the
trough enters western Wyoming. Lift ahead of the trough may be
enough to produce some light showers across the CWA Wednesday night.
Looking further ahead, models are still a bit out of phase with
regards on how to handle late next week`s trough and cold front.
Both the ECMWF and GFS differ on timing of frontal passage and if
the CWA sees any precipitation. Although confidence is still low,
temperatures could cool off greatly as both models show a pretty
strong front. A strong front also means a higher likelihood of
strong winds occurring sometime late next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 524 PM MDT Thu Sep 14 2023
A passing weather disturbance will produce some scattered showers
this evening, with clearing skies overnight and Friday morning in
the wake of the disturbance.
Wyoming TAFS...Broken ceilings around 5000 feet AGL will clear
this evening at Rawlins.
Ceilings will lower to 2500 feet AGL this evening at Laramie with
fog reducing visibilities to 3 miles from 05Z to 14Z, then skies
will clear.
Expect occasional light rain at Cheyenne until 02Z, with
visibilities near 3 miles and ceilings near 2500 feet AGL. From
05Z to 14Z, expect overcast ceilings at 1500 feet AGL with fog
reducing visibilities to 3 miles. Then VFR ceilings will become
clear by midday on Friday.
Nebraska TAFS...Scattered to broken clouds from 7000 to 10000 feet
AGL will prevail through early morning Friday at Chadron and
Alliance, then skies will become clear.
At Scottsbluff and Sidney, ceilings near 6000 feet AGL will occur
through early evening, then expect areas of fog reducing
visibilities to 3 miles and ceilings near 1500 feet AGL to develop
and continue until 15Z, with skies then becoming clear. Winds will
gust to 30 knots at Sidney until 02Z.
&&
.FIRE WEATHER...
Issued at 117 PM MDT Thu Sep 14 2023
Cold front that moved through southeast Wyoming and Nebraska
Panhandle early this morning has brought fairly widespread light
to moderate rain to the area. Some moderate rainfall has been
reported in northern slopes of mountains and higher hills. Much
cooler temperatures behind the front has kept afternoon humidity
high. No fire weather concerns over the next day or two. Rain
comes to an end tonight as front continues to move southeast.
Warmer and drier weather returns Friday through the weekend.
Humidity becomes critical Sunday...but winds are expected to remain
below critical levels.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...SF
AVIATION...RUBIN
FIRE WEATHER...GCC
...Update to aviation forecast discussion...
.DISCUSSION...
Issued at 254 PM CDT Thu Sep 14 2023
Key Points:
- Scattered showers Friday into Friday night, otherwise dry into
early next week
- Slight warm-up early next week, otherwise temperatures hover near
average for this time of year
19Z water vapor imagery depicts an upper low circulating over
Saskatchewan and Manitoba with its trough axis extending through the
northern Plains into the Four Corners region. Ridging is noted off
the Pacific Northwest coast. At the surface, high pressure has been
pushing east with low pressure set up in the Dakotas ahead of the
aforementioned upper low. Associated frontal boundary is in
northwestern NE.
Quiet and dry conditions are expected to continue tonight with cloud
cover gradually increasing into the day tomorrow. There are some
hints of isentropic lift toward central KS bringing a few showers
into our western counties ahead of the front as early as sunrise,
although the HRRR appears to be the most robust on this idea with
most other CAMs keeping precip to the west until late morning or
early afternoon. Forecast soundings do show a little better moisture
in the column later in the morning, but the best saturation doesn`t
occur until the evening and overnight time period. Overall, the best
lift appears to be displaced north as the core of the upper low
passes just north of the international border Friday into Saturday.
With this in mind, am hesitant to go higher than 30-40 percent PoPs.
In any case, instability looks rather weak with lapse rates
struggling to reach 6 deg C/km and MLCAPE struggling to reach 100
J/kg.
Regardless of precipitation, a weak frontal boundary looks to pass
through the area Friday evening into early Saturday, though little
change in temperature is expected. Some moisture pooling looks to
take place behind the boundary Friday night and could linger into
Saturday morning, but a drier air mass should move in later Saturday
and especially Sunday behind the departing upper trough axis.
Upper ridging looks to return Sunday, although this looks short-
lived as a more active pattern takes place into early next week.
Increasing WAA should bring temperatures into the upper 80s,
potentially near 90 Monday and Tuesday. Exact placement and timing
of weaker disturbances lead to higher uncertainties on precip
chances at this time, but long-range guidance suggests a deeper and
more amplified trough developing in the western CONUS by mid-week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 606 PM CDT Thu Sep 14 2023
VFR conditions will persist through the TAF period at all sites.
Winds will generally remain out of the south during the period and
under 10 knots before some scattered rain showers will move in
from the west late in the period. Added mention of VCSH for KMHK
after 18z.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Picha
AVIATION...Griesemer