Office: CYS
FXUS65 KCYS 171120
AFDCYS
Area Forecast Discussion
National Weather Service Cheyenne WY
355 AM MDT Wed Aug 17 2022
.SHORT TERM...(Today and tomorrow)
Issued at 355 AM MDT Wed Aug 17 2022
Key Impact Messages:
1) No impact messages needed do to quiet weather.
Weather Details: We are tracking an area of low clouds across the
NE Panhandle this morning. This area of low clouds is beginning to
approach the NE/WY border and may move close to Cheyenne. Road
cameras are not showing and significantly reduced visibilities
and or fog. Expect this area of low stratus to dissipate soon
after sunrise.
Short term forecast remains under the influence of an area of high
pressure building across much of the Intermountain West. This area
of high pressure has shutoff the moisture tap and brought in some
dry air into the region. This system will slowly move east today
through Thursday. Mostly clear skies and light winds are expected
with warm temperature. Models are beginning to trend toward this
area of high pressure remaining the main weather feature as latest
model runs want to stall out the high pressure system keeping the
better moisture well south of our area.
.LONG TERM...(Friday through Tuesday)
Issued at 355 AM MDT Wed Aug 17 2022
Precipitation chances Friday through Sunday are trending lower with
the latest ensemble runs bringing very little to no precipitation to
southeast Wyoming and the Nebraska panhandle. The best chance is in
the Snowy and Sierra Madre mountain ranges, and maybe the south
Laramie Range. However, with precipitation chances trending lower,
temperatures have also trended lower this weekend with a backdoor
cold front dropping across the Nebraska panhandle into eastern
Wyoming! Saturday morning looks to be the coolest morning with lows
across southeast Wyoming being 41 to 55 degrees (53 deg F in
Cheyenne) and 53 to 56 degrees across the Nebraska panhandle.
The main uncertainty will be in how far southwest the front drops.
Right now, the GFS has the cold front stalling along a line from
Sidney, Nebraska to near Casper, Wyoming Friday afternoon, then
backing up as a warm front through the day Saturday.
Tuesday another backdoor cool front moves into the Nebraska
panhandle and southeast Wyoming. This front looks to be stronger and
advect both monsoonal and Gulf moisture, greatly increasing the
precipitation chances as it combines with the instability from the
front. Stay tuned for more details as we get closer to mid-next
week.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 520 AM MDT Wed Aug 17 2022
A low stratus deck is bringing IFR with intermittent LIFR CIGS
across the NE terminals this morning. This area of low clouds may
expand toward the KCYS terminal over the next hour. This low status
deck will begin to dissipate between 14-15z, with rapid improvement
to VFR conditions. Expect VFR conditions to prevail through the rest
of the TAF period. Winds will continue to be light across all
terminals at less than 10 knots, become light and variable at times.
&&
.FIRE WEATHER...
Issued at 355 AM MDT Wed Aug 17 2022
Conditions will continue to warm and become drier
today and into Thursday. Minimum relative humidity values may
approach critical conditions for areas west of the Laramie Range
today, then spreading across the rest of the region on Thursday.
The limiting factor that will help keep fire weather concerns low
will be the continued light winds today and Thursday. Moisture
looks to return Carbon and Albany counties by the weekend.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...AW
LONG TERM...LK
AVIATION...AW
FIRE WEATHER...AW
Office: RIW
FXUS65 KRIW 171037
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
437 AM MDT Wed Aug 17 2022
.SHORT TERM...(Today through Thursday)
Issued at 332 AM MDT Wed Aug 17 2022
Any remaining showers taper off by early Wednesday morning. Lows
overnight range from the mid 50s to low/mid 40s. Winds will be
light and variable with skies remaining mostly clear at sunrise.
Wednesday is dry for many with mostly sunny skies and highs slightly
above average. By the late afternoon/early evening a weak shortwave
maked its way through northeastern WY. The disturbance taps into
moisture and provides favorable lift, leading to convective
showers and thunderstorms mainly over the Bighorn Mountains, which
subsequently drift over Johnson County. Other than Johnson
County, the high terrain has the best chance for getting a brief
shower.
Skies will again clear out by Wednesday evening into early morning
Thursday. Most stay dry overnight as the upper level high to the
west shifts further east, shifting flow aloft to a more north-
northwest direction. Thursday will be mostly sunny with highs
still slightly above average. Johnson county may have cooler highs
in the wake of the shortwave that moved through Wednesday. Even
with isolated showers and thunderstorms developing over the high
terrain of western WY by the afternoon, most of the state will
remain dry. Precipitation clears out by late Thurs evening, with
high clouds moving into the western portion of the state.
.LONG TERM...(Thursday night through Tuesday)
Issued at 332 AM MDT Wed Aug 17 2022
Pattern remains relatively unchanged through the extended. A ridge
stays entrenched across the western US until the middle of next
week. A few week disturbances will try to undercut the ridge and
provide some lift to WY. Thursday night monsoonal moisture begins
moving into southwest WY as the first disturbance makes its way
eastward. Slow movement of this disturbance is likely as it
struggles to move east with the ridge acting as a blocking feature.
This will result in isolated to scattered thunderstorms across
southwest WY Friday and Saturday afternoon. By Sunday isolated
thunderstorms are possible in central basins and the Bighorn
Mountains as the disturbance shifts east. PWATs decrease on Monday,
still remaining above normal, as monsoonal flow gets shut off. At
the same time a shortwave passes to the northwest of the area,
providing sufficient lift for showers and storms, especially across
western WY. Wind aloft will consistently be light resulting in very
weak wind shear. This combined with above normal PWATs will continue
the trend of thunderstorms capable of producing localized flash
flooding over the next seven days.
The shortwave is still expected to influence weather on Tuesday with
a shift in the location of convection to eastern portions of the
CWA. This will be where the better moisture and lift exist. Another
weak shortwave passes through on Wednesday with very little jet
support. As of right now this appears to be the day with the most
widespread showers and thunderstorms, especially for northern and
eastern portions of the CWA.
For the first half of the long term period, temps will be moderated
in western WY thanks to rain chances and cloud cover. East of the
divide, where skies will remain mostly clear, highs are not expected
to be record-breaking, but seasonable highs in the upper 80s F and
low 90s F are likely. This should change as cloud cover increases
ahead of the shortwave and a cold front drops down over the north on
Wednesday. Wind will be light through the long term period as this
type of pattern keeps the pressure gradient lax.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 436 AM MDT Wed Aug 17 2022
VFR prevails at all terminals through the TAF period. Very isolated
showers and thunderstorms are possible this afternoon, mainly
impacting KCPR and possibly KPNA. Late this afternoon strong
northerly outflow wind is likely at KCPR with gusts above 30 knots
possible. Other terminals will have wind below 12 knots over the
next 24 hours. Skies will be mostly clear across the area today
through tonight.
Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.
&&
.FIRE WEATHER...
Issued AT 332 AM MDT Wed Aug 17 2022
Today is likely to be the warmest and lowest humidity day of the
week. Temperatures increase by a couple degrees compared to
yesterday (Tuesday), and RHs will drop into the mid to upper
teens during the afternoon hours. Winds will be light, and
generally under 15 mph, except in the immediate vicinity of any
isolated showers or thunderstorms. Most of the limited convective
activity is forecast to remain over the high terrain, but Johnson
county could see an isolated cell drift eastward off the Bighorn
Mountains during the afternoon.
Temperatures cool and and RHs will be a few percentage points
higher on Thursday, as a trough edges in from the east. Light
north and east winds are expected Thursday, with gusts 20 to 25
mph during the afternoon.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...VandenBoogart/Dziewaltowski
LONG TERM...Rowe
AVIATION...Rowe
FIRE WEATHER...VandenBoogart/Dziewaltowski
