FXUS65 KCYS 092229

AFDCYS



Area Forecast Discussion

National Weather Service Cheyenne WY

429 PM MDT Fri May 9 2025



.KEY MESSAGES...



- Widely scattered showers and thunderstorms this afternoon will

  have the potential to produce strong, gusty winds.



- Near record high temperatures are expected this weekend into

  early next week.



- Afternoon showers and thunderstorms will be possible again on

  Sunday, and daily from Tuesday onwards.



&&



.SHORT TERM /THROUGH SATURDAY NIGHT/...

Issued at 425 PM MDT Fri May 9 2025



Light northerly flow aloft remains in place over southeast Wyoming 

and western Nebraska today as the region continues to sit on the 

periphery of a ridge of high pressure over the southwestern CONUS. 

Seasonably marginal surface moisture also remains in place, with 

surface dewpoints generally in the 30s throughout the CWA, including 

the mountains of southeast Wyoming. Combined with strong daytime 

heating and cool-ish air aloft remaining in place, surface-based 

CAPE values of around 500-1000J/kg are in place today per RAP-13 

mesoanalysis. Isolated to scattered afternoon thunderstorms can be 

expected to continue through the afternoon, mainly tied to the 

mountains with a south to southwestward drift per Bunkers storm 

motion vectors. As surface heating diminishes later today, expect 

any lingering convection to quickly diminish similar to yesterday 

with a mostly clear overnight expected.



A dry day with even warmer temperatures is expected on Saturday for 

all of southeast Wyoming and western Nebraska. The ridge of high 

pressure over the southwestern CONUS will slide eastward into the 

Four Corners and the axis of this ridge will center right over 

central Wyoming/western Colorado during the afternoon hours. Highs 

will run around 10-15 degrees above average with light surface winds 

generally driven by diurnal terrain circulation patterns. Forecast 

confidence is very high throughout the short-term with only minimal 

adjustments made to PoP blends this afternoon in this forecast 

package.&&



.LONG TERM /SUNDAY THROUGH FRIDAY/...

Issued at 425 PM MDT Fri May 9 2025



A quick look at the long term shows a dry and warm start to next 

week, with a return to cooler and wetter weather by the end of the 

week.



Southwest flow under the ridge Sunday and Monday will lead to warm, 

above average temperatures on both days. 700 mb temperatures on both 

days will climb above +10C, leading to high temperatures in the 70s 

and 80s for most locations. A few lower elevation spots may make a 

run for 90 degree temperatures! As a result of highs being 20+ 

degrees above average, a few locations will make a run at setting 

new records. Although conditions during this time will be mostly 

dry, cannot rule out a few stray storms on Sunday with MUCAPE values 

above 500 J/kg. Model soundings show inverted-v profiles, so its 

likely not much precipitation will make it to the ground. The 

inverted-v profile will also lead to gusty storms, with rogue gusts 

to 50 MPH not out of the question. Dry conditions continue into 

Monday and Tuesday with minimal chances of precipitation.



An upper-level trough will dig into the Great Basin on Wednesday and 

into the Rockies by Thursday, bringing cooler temperatures and a 

better chance for precipitation. 700 mb temperatures will fall to 

0C, leading to high temperatures roughly around average for 

this time of year. This trough will also have some mid-level 

moisture associated with it. This combined with forcing from the

cold front and vorticity maxes aloft will lead to precipitation

chances on both Wednesday and Thursday. Current model soundings

show modest instability with not much of a severe threat.



&&



.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...

Issued at 1131 AM MDT Fri May 9 2025



Main aviation concern for the TAF period will be scattered showers 

and thunderstorms this afternoon and evening. Gusty winds will be 

the primary concern with these storms with rogue gusts over 40 kts 

possible. Cannot rule out small hail with these storms as well, or 

brief visibility reductions in light to moderate rain. Storms will 

dissipate later this evening, leading to a dry and calm

overnight.



&&



.CYS WATCHES/WARNINGS/ADVISORIES...

WY...None.

NE...None.



&&



$$



SHORT TERM...MAC

LONG TERM...SF

AVIATION...SF