wy discuss
Office: CYS
FXUS65 KCYS 112332
AFDCYS
Area Forecast Discussion
National Weather Service Cheyenne WY
532 PM MDT Fri Jul 11 2025
.KEY MESSAGES...
- Strong storms and heavy rainfall expected this afternoon and
evening with a slight risk (2 of 5) of severe weather,
alongside a slight risk of heavy rainfall.
- Temperatures will be warming Sunday through Monday, before a
potent cold front brings cooler temperatures for Tuesday and
Wednesday, with another warming trend for Thursday and Friday.
Shower and thunderstorm chances will be greatest for Tuesday
and Wednesday.
- Elevated fire weather conditions expected late this weekend
and early next week.
&&
.SHORT TERM /THROUGH SATURDAY/...
Issued at 1222 PM MDT Fri Jul 11 2025
Cumulus field and some showers are already developing across
the area as we expect thunderstorm initiation shortly in Albany
County. Storms will form around the frontal boundary just over
the border in Colorado and continue to evolve eastwards through
the afternoon and evening primarily along the I-80 corridor,
though a few stragglers just north of this could be possible.
Low to mid level flow is quite slow, so any storms that do form
should slowly propagate eastwards bringing a heavy rainfall
threat with them alongside supportive PWAT values peaking around
125-150% of normal. Widespread QPF values are forecast around
0.5-1 inch which should keep us just outside of flooding, but if
we get clustered storms to train over a location some localized
flooding can't be ruled out. Meanwhile for the severe threat,
mesoanalysis shows instability rising with widespread MUCAPE
around 1000-2000 J/kg and surface to 3km wind shear 25-30 knots,
supportive of isolated initial stronger storms capable of large
hail and damaging wind gusts. That being said, LCL heights are
still sitting at around 1500-2000 feet, so storms will struggle
to reach the surface and should keep the tornado threat limited
(but can't be fully ruled out). With the slow motion, storms
will likely congeal into clusters quickly and we should see the
hail threat begin to wane while the wind threat remains enhanced
as activity continues eastwards through Nebraska. The bulk of
the strongest storm activity should vacate the CWA by around 9
to 10 PM, with a few lingering showers or weak storms possible
after that time but most precipitation should be fully out of
our area by midnight.
Overnight soundings are supportive of low clouds and possible
fog for our usual problematic spots (Laramie Summit through
western Cheyenne and also along I-80 into Sidney) with this
clearing out as the sun rises. High pressure builds and brings a
clearing and warming trend, though a few isolated terrain
driven showers or weak storms can't be fully ruled out on
Saturday. These will be brief and mostly inconsequential, and
should quickly dissipate as the sun sets. Otherwise a pleasant
summer day is on tap with highs beginning to rebound back into
the upper 70's to mid 80's as warming returns, continuing into
Sunday.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 1222 PM MDT Fri Jul 11 2025
Sunday...Ridging aloft builds overhead with 500 mb heights nearing
5920 meters. Warm temperatures aloft should limit convective chances
and produce a dry day. Decent warming trend with maximum
temperatures in the mid 80s to mid 90s with 700 mb temperatures near
17 Celsius.
Monday...Another hot day expected with 700 mb temperatures near 16
Celsius. Looks like enough low and mid level moisture for isolated
to widely scattered afternoon and evening showers and thunderstorms.
Tuesday...A progressive shortwave trough aloft moving across Montana
and North Dakota will send a fairly strong cold front southward
across our counties, dropping high temperatures into the upper 70s
and 80s. With decent low level upslope winds and plenty of low and
mid level moisture, we expect to see scattered afternoon and evening
showers and thunderstorms.
Wednesday...Another relatively cool day for mid July with low level
upslope, plenty of cloud cover and high temperatures in the 70s to
lower 80s. Adequate moisture for scattered afternoon and evening
showers and thunderstorms, most numerous near the Colorado state
line where the moisture will be the deepest.
Thursday...GFS shows a relatively strong cold front moving southward
across our counties in response to a shortwave trough aloft moving
over the Dakotas. However, this solution may be too fast, and thus
will continue to show maximum temperatures in the upper 70s to mid
80s, which matches well with our neighboring offices. Adequate
moisture for isolated to scattered afternoon and evening
thunderstorms.
Friday...Ridging aloft builds overhead, producing another warming
trend. 700 mb temperatures near 15 Celsius yield high temperatures
from the mid 80s to lower 90s. Despite the ridge and warm
temperatures aloft, it looks like enough low and mid level moisture
for isolated to widely scattered thunderstorms focused near the
southern Laramie Range.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 521 PM MDT Fri Jul 11 2025
Northwest flow aloft will continue. A Severe Thunderstorm Watch
is in effect until 11 PM tonight for Albany, Laramie, Banner,
Morrill, Kimball and Cheyenne Counties. Drier weather is
expected for Saturday.
Wyoming TAFS...For Rawlins, skies will be mostly clear. Winds
will gust to 25 knots until 03Z.
For Laramie, ceilings will range from 6000 to 9000 feet until
08Z, with occasional thunderstorms until 02Z, producing wind
gusts to 30 knots, visibilities to 4 miles and ceilings near
5000 feet, then ceilings will be near 1500 feet in fog and
3 mile visibility from 08Z to 15Z, then skies will be clear.
Winds will gust to 25 knots until 02Z.
For Cheyenne, ceilings will range from 4000 to 8000 feet until
04Z, with occasional thunderstorms until 02Z, producing wind
gusts to 45 knots, visibilities to 4 miles and ceilings near
3500 feet, then ceilings will range from 1000 to 2000 feet from
04Z to 15Z, then scattered clouds near 10000 feet will prevail.
Winds will gust to 23 knots until 02Z.
Nebraska TAFS...For Chadron, Alliance and Sidney, scattered to
broken clouds from 4500 to 7000 feet will prevail until 15Z,
then skies will be clear. Winds will gust to 30 knots until 03Z.
For Sidney, ceilings will range from 3500 to 4500 feet until
06Z, with occasional thunderstorms until 03Z, producing wind
gusts to 40 knots, visibilities to 2 miles, then ceilings will
be near 1500 feet from 06Z to 15Z, then scattered clouds near
5000 feet will occur. Winds will gust to 32 knots until 03Z.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...CG
LONG TERM...RUBIN
AVIATION...RUBIN
Office: RIW
FXUS65 KRIW 120345
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
945 PM MDT Fri Jul 11 2025
.KEY MESSAGES...
- Cooler temperatures overnight into Saturday morning.
- Rain showers diminish and push southeast out of the area with
improving skies and dry conditions overnight into Saturday.
- Dry and warming trend return for the weekend and into the
start of next week with the potential for fire weather
conditions by Monday.
&&
.UPDATE...
Issued at 1236 PM MDT Fri Jul 11 2025
A cold front has moved across much of the Cowboy State overnight.
The frontal passage has brought relief to the recent heat that
enveloped the region over the past week. Highs today will reflect
this relief with temperatures in the mid to upper 70s east of the
Divide and upper 70s to low 80s west of the Divide. Scattered
showers and isolated thunderstorms moved across northern WY this
morning but have now dissipated. Another round of showers and
thunderstorms is expected to develop this afternoon. The best
chances of seeing a shower or thunderstorm look to be east of the
Divide, especially across central WY. CAMs have highlighted portions
of the Wind River Basin, eastern Sweetwater County and southern
Natrona County. Overall, dynamics are not overly impressive but
there does look to be some favorable components that may lead to a
strong or near severe storm. CAPE values are marginal ranging from
500 to 1000 J/kg with some shear present but not overly
impressive. PWAT values look to be above normal with values
ranging from 0.75 to 1.00 in. These dynamics will lead to the
possibility of a few hazards as a result of any strong storms
that develop. These hazards look to be hail, strong gusty
outflow winds, and isolated heavy downpours. Very isolated flash
flooding cannot be ruled out, especially in poor drainage
locations but the overall concern for this is not very high. As
mentioned earlier, CAMs highlight central WY especially portions
of the Wind River Basin. SPC's day 1 outlook supports this with
a sliver of marginal chances for severe thunderstorms being
drawn across central WY into southwestern WY. Showers and
thunderstorms look to start developing shortly after noon over
northern WY and gradually tracking southeast through the
remainder of the afternoon and evening. Convection moves out of
the area around sunset with quiet weather prevailing overnight
through the weekend.
The weekend sees warmer and drier conditions return to the area with
highs reaching the upper 80s to mid 90s. These warm temperatures and
dry conditions may lead to fire concerns by Monday. Winds are
looking to increase Monday along with low min RH values and warm
temperatures. These components may lead to portions of the state
seeing elevated to near critical fire weather conditions. This
possibility will continue to be monitored as we head into the
weekend. The next chance for precipitation does not look to arrive
until the start of next week as a trough moves across the region.
Another front moves through the area around Tuesday night bringing
in a brief period of cooler temperatures. The remainder of the week
looks to have increased chances for precipitation as multiple
disturbances move through the region.
&&
.DISCUSSION...
Issued at 259 AM MDT Fri Jul 11 2025
When I was surfing the net before I left for work, I happened
upon an old commercial I have not seen since my youth, many eons
ago. It is for the antacid Rolaids. And the question asked in
it is: How do you spell relief? And the answer is spelled out:
R-O-L-A-I-D-S. And this relates to this question, how do you
spell relief from the heat? And the answer is C-O-L-D F-R-O-N-T.
A cold front is currently moving through the area, having
passed through the humble Riverton weather abode a bit ago with
wind gusts close to 50 mph with the strong cold advection. Both
Greybull and Buffalo have gusted over 50 mph as well. These
strong wind gusts should slowly end though. The big change today
will be much cooler temperatures that will move in today East
of the Divide, where some locations will be up to 20 degrees
cooler than yesterday, with a place like Buffalo struggling to
get out of the 60s. It will feel more like May than July. It
will remain warm West of the Divide though, with temperatures
close to yesterday's highs though. As for convection, we do have
some instability but not a ton, maximum CAPE values max out at
around 1000 J/Kg in some of the mountains but it is generally
around 500 J/Kg or less. Lifted indices generally drop down as
low as minus 2. Much of the area, except for southwestern
Wyoming, may see a shower or storm but the chance is generally
at most 1 out of 4, with up to a 2 in 5 chance in some of the
mountain ranges. Most of this looks like an early show, with
most over around 6 pm and all over by sunset.
The weekend at this point looks relatively uneventful with mainly
dry conditions under northwest flow. Many people will be suffering
from temperature whiplash though with near to above normal
highs returning Saturday and especially Sunday with widespread
90s in the lower elevations East of the Divide and some
locations getting close to 100. Fire weather concerns look low
though with wind remaining light to moderate.
Active weather then begins ramping up again starting Monday. On
Monday a shortwave will approach the area and bring a chance of
showers and storms, mainly across northern portions of the
state. This will also tighten the pressure gradient across the
area and bring a gusty wind which will likely increase fire
weather concerns, especially in southern Wyoming. Following
that, a more potent cold front will drop southward into the area
and bring a better chance of showers and storms, possibly both
on Tuesday and into Wednesday. Details on which day will be
wetter and details of where the storms may fire are still highly
uncertain though. Cooler temperatures will also move in for
midweek as a trough lingers across the area. So, it looks like
we will be riding the temperature rollercoaster as we head into
through the middle of July.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 945 PM MDT Fri Jul 11 2025
VFR conditions expected throughout the entirety of the period.
All rain showers have pushed southeast of the CWA with dry
conditions through the weekend. Light winds overnight with
clearing skies west to east of the Divide. Winds increase after
18-19Z due to daytime heating and mixing to the surface. Gusts
up to 18kts at JAC/PNA/CPR and up to 25kts at RKS/BPI through
01Z with radiational cooling towards sunset and overnight into
Sunday morning. Few to scattered high clouds remain throughout
the period with more ample sunshine than previous days, with no
other weather elements expected at this time.
Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on smoke, icing, and turbulence
forecasts.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Dziewaltowski
DISCUSSION...Hattings
AVIATION...Lowe
