Rock River, Wyoming Weather Forecast Discussion

751
FXUS65 KCYS 281105
AFDCYS
Area Forecast Discussion
National Weather Service Cheyenne WY
505 AM MDT Sun Sep 28 2025
.KEY MESSAGES...
- Warm temperatures continue today, though isolated to scattered
  showers are possible across western portions of the region.
  Breezy conditions across the Panhandle today.
- Slightly cooler temperatures on Monday behind a departing
  upper- level trough. Isolated to scattered precipitation
  chances out west once again.
- Drier conditions return late week as another upper-level ridge
  moves overhead.
&&
.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 154 AM MDT Sun Sep 28 2025
Mostly clear skies ongoing across northern and eastern portions of
the CWA this morning as some upper-level clouds begin to move into
southern and western portions of the CWA. Winds have slowly
decreased tonight with most locations only at around 10kts, compared
to the gustier day prior. Southerly winds across the CWA will
continue into the morning and afternoon hours and begin to increase
once more. As of now, no precipitation is currently detected on
radar, despite the clouds moving into portions of the region.
Today, upper-level ridging will slowly break down as an upper-level
trough pushes into the Four Corners region and upper-level flow
turns southerly to southwesterly over the CWA. Southerly winds are
expected to develop throughout the atmosphere today, with several
500mb vorticity lobes advecting through the flow, allowing for
decreasing heights. 700mb height gradients will subtly strengthen
this afternoon as the high over the eastern CONUS meanders slightly
westward ahead of the approaching trough. As a result, the 700mb jet
will increase to around 30 to 35kts in some locations. Looking at
some less common pressure fields from the GFS, the 800mb winds will
increase across western Nebraska with the strengthening 700mb height
gradients and jet. While the strongest wind increases at 800 and
850mb are expected across central Nebraska, gusty winds are still
expected to bleed into the Nebraska Panhandle resulting in another
breezy day across this region. GFS omega fields do suggest some
modest subsidence across the northern Panhandle near the Pine Ridge
early this morning with additional subsidence present across the
southern Panhandle later this afternoon into the evening hours.
Therefore, gusty winds are expected through the day in the
Panhandle, with potential for a brief lull in the mid-morning hours.
Aside from the gusty winds this afternoon, southerly 700mb flow will
also act to advect in warmer 700mb temperatures, leading to surface
temperatures in the low-70s to mid-80s across the CWA. Chadron looks
to be the warm spot today due to warming 700mb temperatures and
downslope warming given the strong, southerly winds expected this
afternoon. Unlike the past few days, some isolated to scattered
showers may develop this afternoon, primarily across the higher
terrain of Carbon and Albany counties. Even a rumble or two of
thunder cannot be ruled out. However, isolated rain showers cannot
be ruled out throughout much of Albany and Carbon counties this
afternoon. Dry conditions across the Panhandle with mostly drier mid-
level will prevent any significant precipitation potential for
locations east of the Laramie Range.
For Monday, the upper-level trough will traverse across the CWA
leading to southerly winds shifting to the northwest. A weak ridge
will attempt to develop and push through the region late Monday
night, but will be quickly pushed out of the region ahead of the
next upper-level trough expected to traverse across the region
Tuesday and Wednesday. With the fairly unsettled upper-levels on
Monday and several 500mb vorticity lobes pushing through, a few more
isolated to scattered showers will be possible in similar areas as
to Sunday. A rumble or two of thunder cannot be ruled out once
again. Widespread precipitation is not expected as the window for
precipitation is pretty short, given the intruding upper-level
ridge. Southwesterly flow at 700mb is expected throughout the day
Monday, leading to some increased winds across western Carbon County
and further supporting some orographic lift across the Sierra
Madres. 700mb flow will remain warm despite some weak cold air
advection across the region. While 700mb temperatures will be warm,
the cold air advection will allow slightly cooler temperatures, with
highs in the upper-60s to mid-80s. Chadron once again looks to be
the warmest location on Monday as light downslope winds act to warm
temperatures slightly throughout the afternoon hours.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 150 PM MDT Sat Sep 27 2025
No major changes were made to the long term forecast with this
update. The synoptic weather pattern for most of the week will be
characterized by a broad ridge encompassing most of the central and
eastern CONUS, leaving southwest flow aloft over our area. A
disorganized disturbance will slowly move across the area through
Monday, keeping a little bit of unsettled weather in the picture
into the early part of the work week. This system will have a
moisture tap to a last gasp of the monsoon, pushing precipitable
water to over the 90th percentile of climatology for most of the
area. We will have a little bit of forcing from the upper level vort-
max moving through tapping into some marginal instability. As a
result, look for a few scattered showers and thunderstorms in the
afternoon and early evening hours, mainly concentrated over and near
the SE Wyoming higher terrain.
This disturbance will exit the area by early Tuesday, while another
shortwave trough passes well to our northwest. With good ensemble
agreement on our area remaining on the periphery of the ridge,
expect fairly warm and dry weather to dominate most of the week
ahead. We may see a gradual warming trend peaking Thursday or Friday
with fairly minimal precipitation chances. Southwest winds may be
gusty at times, especially in Carbon county.
Models diverge somewhat as we approach Friday and into the weekend.
There is good agreement that the trough hanging near the Pacific
northwest for most of the week will push inland over the northern
Rockies, but considerable spread in terms of how deep the broad
longwave trough will be, and thus the tracks and timing of any
individual shortwave ejecting over the area. At a minimum, expect
temperatures to drop for Saturday, likely closer to average. The
official forecast includes chances for rain showers and mountain
snow returning Friday PM and continuing into the weekend, but only a
minority of ensemble members are showing widespread substantial
precipitation. Each shortwave may also bring the potential for an
increase in winds (shown by the deterministic GFS), but there is not
clear ensemble support for a notable wind event at this time.
&&
.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 503 AM MDT Sun Sep 28 2025
VFR conditions expected to continue this morning as winds remain
mostly light. KCDR has been gusty all night and will continue to
be gusty throughout the day. Other terminals in western Nebraska
see increasing winds by the late-morning hours. Gusty winds are
expected to persist through the afternoon and evening hours.
There is a small, 10%, chance of low ceilings near KCYS this
morning. At this time, this threat does not look likely and
clouds should remain in the upper-levels.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...AM
LONG TERM...MN
AVIATION...AM

NWS CYS Office Area Forecast Discussion