188 
FXUS65 KCYS 070511
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1111 PM MDT Thu Oct 6 2022

.UPDATE...
Issued at 745 PM MDT Thu Oct 6 2022

The cold front has accelerated its push towards the Laramie range
in the last few hours, with GOES satellite imagery showing the
low-cloud deck moving into the Sidney area as well as northern
Laramie county. This is a few hours ahead of most hires guidance,
which warranted some minor tweaks to the forecast. Dropped
temperatures for the next few hours and also nudged the winds up
immediately behind the front. The faster southwestward progression
of the front has also boosted confidence in the cloud-deck
intersecting the terrain near the I-80 summit, which lead to the
issuance of a Dense Fog Advisory through Friday morning. Showers
have also begun to develop near the North Platte River Valley,
with some lightning strikes already observed. Expect this activity
to expand and continue through much of the overnight as isentropic
lift supports continued redevelopment in a similar area through
about 12z. 

&&

.SHORT TERM... (This evening through Friday night) 
Issued at 355 PM MDT Thu Oct 6 2022

KEY MESSAGES:

1) Scattered showers and isolated thunderstorms possible overnight 
Thursday night across the central and northern Nebraska panhandle 
and portions of east central Wyoming.

2) Areas of fog possible in areas that receive precipitation 
Thursday night/early Friday morning. Fog that does develop will 
impact morning commute, clearing by mid-morning.

3) Widespread chances of frost across all of southeast Wyoming and 
the Nebraska panhandle Friday night/early Saturday morning.

DISCUSSION: The main story this afternoon through tonight is the 
cold temperatures with the passing cold front and scattered showers 
with isolated thunder possible. Temperatures behind the cold front 
are currently sitting in the 40s, creating a 20 to 25 degree 
temperature gradient across our CWA this afternoon. 

Hires guidance shows scattered showers developing in the Nebraska 
panhandle and far east central Wyoming (east of the Laramie Range) 
late tonight and slowly moving east overnight. Isolated thunder 
cannot be ruled out, however confidence is currently low. Portions 
of the Nebraska panhandle may receive up to 0.20 to 0.30 inches of 
rain, which will not help a ton with the drought deficit, but will 
make some short-term gains! With light winds and moist conditions 
following the showers, areas that received precipitation, may also 
see fog development early Friday morning.

Areas west of the Laramie Range will remain mostly clear overnight 
with temperatures cooling to the low- to mid-30s by sunrise Friday 
morning. Due to these near-freezing temperatures, areas of frost are 
possible, especially in the valleys. Friday throughout the day will 
be dry and cool with highs in the 50s across southeast Wyoming and 
the Nebraska panhandle. There is higher confidence in frost and 
freeze development Friday night/early Saturday morning as the low 
temperatures then will be in the low- to mid-30s across all of 
southeast Wyoming and the Nebraska panhandle. Frost advisories are 
possible. 

.LONG TERM...(Saturday through Thursday) 
Issued at 235 PM MDT Thu Oct 6 2022

The extended forecast includes seasonal to slightly above average 
temperatures from this weekend into early next week, with a strong 
cold front bringing the high temperatures below normal potentially 
by mid-week. Precipitation chances look low at this time until we 
have the strong cold front bring the opportunity back in our favor 
by the middle of next week. 

This weekend will be pleasant as surface high pressure propagates 
across the Northern Plains to the southeast. Cold air aloft at 700mb 
will take its time to slide to the southeast along with the dome of 
high pressure. Morning temperatures are likely to bottom out in the 
20s to middle 30s for a majority of the cwa, so we will monitor the 
forecast in the next 24 hours to see if any headlines are warranted 
with respect to Frost/Freeze criteria. With weak CAA being present, 
several areas will struggle to reach seasonal temperatures on 
Saturday. There will be a gradual trend of temperatures warming at 
700mb from west to east as we transition into the afternoon hours of 
Saturday, with 700mb temperatures warming to near +5C. The lower 
boundary layer will mix these temperatures down to the surface on 
Saturday afternoon, resulting in daytime highs in the 60s for most 
areas, but much cooler air will remain present in the higher terrain 
where the highest peaks in the cwa will struggle to get out of the 
40s.

Sunday will be more of the same as pleasant conditions are expected 
across the area. A cut-off ULL will reside over the Baja California 
and Four Corners region for Sunday. There are some members of the 
model guidance that attempt to show this moisture scooting north 
into CO toward our southern forecast zones, primarily along the I-80 
corridor of SE WY in the mountain terrain. Have kept PoPs out of the 
forecast in the event that we can get better Hi-res data sampling to 
sort this out. The most likely scenario that will play out is 
orographic enhancement resulting in a few sprinkles, and breezy 
winds. Daytime highs are forecast to be about 5 degrees warmer, with 
highs in the 60s to lower 70s, especially east of I-25 into the NE 
Panhandle. 

Monday-Wednesday continue to be a struggle for models to get a good 
handle on. Multiple shortwaves are progged at this time to either 
eject out of the Pacific Northwest to our northeast, a cut-off ULL 
parking itself over the California coastline between Monday-
Wednesday, or a longwave trough bringing precipitation coupled with 
a strong cold front. The highest confidence we have is the cold 
front at this time. Surface high temperatures ahead of this cold 
front will be above average, with highs in the middle 60s to upper 
70s for Monday and Tuesday. The highest daytime temperatures are 
likely in the NE Panhandle. The cold front will result in 
temperatures being on the order of 20 degrees cooler by Wednesday, 
should trends with model guidance on temperatures continue. The 
biggest change over the past 12 hours is that the extended model 
guidance for the GFS and EC model have backed off the precipitation 
opportunities quite a bit, but the Canadian model still hangs onto 
the rain showers for the cwa, with possible mountain snow showers. 
This trend has been present for several days where the models are 
struggling to be consistent, thus we will continue to monitor the 
forecast at this time.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1108 PM MDT Thu Oct 6 2022

Cold front lays along the Laramie Range this evening. Upslope
easterly winds across the Panhandle and eastern Wyoming plains
will create widespread IFR/LIFR conditions through the morning
hours. HRRR supports this and followed its guidance on the 06Z
TAFs. Stratus could stick around through 18Z before lifting.

&&

.FIRE WEATHER...
Issued at 249 PM MDT Thu Oct 6 2022

No fire weather concerns through Monday due to well above 
critical humidity values and cool to cold temperatures. Areas of 
wetting rains possible in the Nebraska panhandle late Thursday 
night into early Friday morning. Next possible day for potential fire
weather concerns is Tuesday. Concerns are limited and generally 
isolated to far southeast Wyoming and the southern Nebraska 
panhandle.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Dense Fog Advisory until 9 AM MDT Friday for WYZ106-116>118.

NE...None.
&&

$$

UPDATE...MN
SHORT TERM...LK
LONG TERM...BW
AVIATION...GCC
FIRE WEATHER...LK