230
FXUS65 KCYS 130712
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
112 AM MDT SUN APR 13 2025
KEY MESSAGES
- NEAR CRITICAL FIRE WEATHER CONCERNS FOR LOW RH VALUES AND
LIGHT WINDS FOR THE LOWER ELEVATIONS OF EAST-CENTRAL WYOMING
AND THE FAR NORTHERN NEBRASKA PANHANDLE ON SUNDAY.
- A COLD FRONT WILL DROP TEMPERATURES BACK TO NEAR
CLIMATOLOGICAL AVERAGE FOR SUNDAY AND MONDAY.
SHORT TERM /THROUGH MONDAY/
ISSUED AT 1256 AM MDT SUN APR 13 2025
A COLD FRONT IS DROPPING SOUTHWARD ACROSS THE HIGH PLAINS AND
INTO THE WYOMING HIGH COUNTRY EARLY THIS SUNDAY MORNING. SURFACE
OBSERVATIONS INDICATE WIND SHIFTS OUT OF THE NORTH FROM CASPER
THROUGH DOUGLAS AS OF 07Z, WITH THE SURFACE FRONT LIKELY
SOMEWHERE ALONG OR JUST SOUTH OF THAT CORRIDOR. THICKER CIRRUS
CLOUDS EVIDENT ON GOES SATELLITE IMAGERY CURRENTLY OBSTRUCT ANY
IR SIGNATURES OF THIS FRONT IN WYOMING, HOWEVER SOME
INDICATIONS OF COOLER SURFACE IR TEMPERATURES DRAINING SOUTHWARD
INTO THE FAR NE PANHANDLE HAVE BECOME EVIDENT OVER THE PAST
HOUR. THIS FRONTAL BOUNDARY WILL QUICKLY DIVE SOUTHWARD THROUGH
THE NIGHT, REACHING THE COLORADO BORDER IN AREAS EAST OF THE
LARAMIE RANGE BY DAYBREAK SUNDAY. FARTHER WEST, THIS SURFACE
FRONTAL BOUNDARY WILL HAVE A TOUGHER TIME SQUEEZING SOUTHWARD
THROUGH THE HIGHER TERRAIN, HOWEVER HIGH-RES GUIDANCE DOES PUSH
THE BOUNDARY AT LEAST TO I-80 IN RWL AND LAR BY AROUND 18Z.
GUIDANCE HAS CONTINUED THE TREND OF BACKING OFF ON ANY
APPRECIABLE PRECIPITATION ALONG AND JUST BEHIND THIS BOUNDARY.
SOME SATURATION IN THE MID LEVELS IN WESTERLY FLOW WILL BRING A
FEW SNOW SHOWERS TO THE SIERRA MADRE AND SNOWY RANGE LATE
TONIGHT AND ENDING ON SUNDAY MORNING. HOWEVER, VERY DRY SURFACE
BOUNDARY LAYERS IN FORECAST SOUNDINGS WILL PRECLUDE ANYTHING
OTHER THAN ISOLATED LOW-END POPS IN THE VALLEYS SUCH AS LARAMIE
AND FARTHER EAST THROUGH CHEYENNE. AS SURFACE FLOW EAST OF THE
LARAMIE RANGE CONTINUES TO VEER TO A MORE NORTH-NORTHEASTERLY
COMPONENT THROUGH THE DAY ALONG AND JUST SOUTH OF THE CHEYENNE
RIDGE, SOME ADDITIONAL PRECIPITATION MAY BE ABLE TO REACH THE
GROUND ALONG THE WY/CO BORDER GIVEN INCREASED SURFACE
SATURATION. HOWEVER, THE BEST TIMING OF ANY LINGERING MOISTURE
ALOFT WITH MORE FAVORABLE SURFACE FLOW LOOKS FAIRLY OFFSET, AND
IT IS NOT LIKELY THAT ANY SHOWERS ALONG THE CO BORDER WILL
AMOUNT TO ANYTHING MORE THAN A FEW HUNDREDTHS OF AN INCH OF
LIQUID.
ANOTHER DAY OF COOLER WEATHER IS EXPECTED ON MONDAY AS THE BASE
OF THE UPPER-LEVEL TROUGH MOVES THROUGH AND 500MB HEIGHTS REACH
THEIR MINIMUM. STILL, TEMPERATURES WILL TOP OUT AROUND OR
SLIGHTLY ABOVE SEASONAL AVERAGES WITH A MOSTLY SUNNY DAY
EXPECTED AREA-WIDE. EXPECT CRISP NIGHTS ON SUNDAY AND MONDAY
NIGHT WITH TEMPERATURES IN THE MID TO UPPER-20S THROUGHOUT MOST
LOCATIONS. FORECAST CONFIDENCE IS HIGH THROUGHOUT THE SHORT-TERM
PERIOD WITH MINIMAL ADJUSTMENTS MADE IN THIS PACKAGE.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
ISSUED AT 155 PM MDT SAT APR 12 2025
MUCH OF THE LONG TERM FORECAST REMAINS UNEVENTFUL AS BOTH THE GFS
AND ECMWF SHOW UPPER-LEVEL RIDGING OVER THE CWA THROUGH AT LEAST MID-
WEEK. GRADUAL WARMING IS EXPECTED MONDAY THROUGH WEDNESDAY AS THE
RIDGE BUILDS INTO THE ROCKIES. 700 MB TEMPERATURES WILL RISE THROUGH
THIS TIMEFRAME, WITH TEMPERATURES ALOFT MAXING OUT AROUND 7C BY
WEDNESDAY. BY TUESDAY AND WEDNESDAY, HIGH TEMPERATURES ACROSS THE
AREA WILL BE ABOUT 10 DEGREES ABOVE AVERAGE. THIS TRANSLATES TO
HIGHS IN THE MID 60S TO UPPER 70S. DUE TO SUBSIDENCE UNDER THE
RIDGE, MOSTLY SUNNY SKIES ARE EXPECTED WITH MINIMAL CHANCES FOR
PRECIPITATION. CLOUDS WILL BEGIN TO INCREASE WEDNESDAY EVENING AS
THE NEXT STORM SYSTEM APPROACHES WITH A PATTERN CHANGE.
HEADING INTO THE END OF THE WORK WEEK, THERE IS SOME MODEL
DISAGREEMENT BETWEEN THE GFS AND ECMWF. THE ECMWF SHOWS A MUCH
WETTER SOLUTION, WITH A PROLONGED PERIOD OF MOISTURE AS AN UPPER-
LEVEL CLOSED LOW SPINS OVER THE GREAT BASIN THURSDAY INTO THE
WEEKEND. THE GFS SHOWS THE POSITIONING OF THIS LOW FURTHER WEST,
LIMITING WIDESPREAD PRECIPITATION ACROSS THE AREA, AS WELL AS
SHOWING LIGHTER QPF AMOUNTS. DUE TO THIS DISCREPANCY, DECIDED TO
LOWER POPS ON THURSDAY AND FRIDAY AS THE NBM SEEMED MUCH TOO
AGGRESSIVE. LOWERED POPS TO HAVE "CHANCE" WORDING INSTEAD OF
"LIKELY" AS THIS SYSTEM IS ALSO STILL 6 TO 7 DAYS OUT. DESPITE THERE
BEING DISAGREEMENT REGARDING PRECIPITATION, MODELS HAVE BETTER
CONSISTENCY ON TEMPERATURES. BOTH THE GFS AND ECMWF SHOW A FRONT
ARRIVING AT SOME POINT ON FRIDAY THAT WILL BRING COOLER TEMPERATURES
TO THE REGION. HIGH TEMPERATURES ON FRIDAY AND SATURDAY COULD
BE BELOW AVERAGE WITH HIGHS POTENTIALLY ONLY IN THE 40S AND 50S
ACROSS THE CWA.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1032 PM MDT SAT APR 12 2025
VFR CONDITIONS EXPECTED OVER THE NEXT 24 HOURS. BREEZY WINDS
HAVE MOSTLY SUBSIDED THIS EVENING, BUT WILL RESUME AGAIN
TOMORROW MORNING AND LASTING INTO THE EVENING FOR ALL SITES,
WITH GUSTS 30-40 KNOTS EXPECTED. A CHANCE AT SOME SHOWERS IS
POSSIBLE FOR THE WYOMING TAF SITES, BUT THIS RISK IS ON THE LOW
SIDE AND THEY SHOULD BE PASSING AT BEST FROM THE OVERNIGHT HOURS
THROUGH INTO THE AFTERNOON HOURS TOMORROW.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MAC
LONG TERM...SF
AVIATION...CG
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