400
FXUS65 KCYS 152324
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
524 PM MDT TUE APR 15 2025
KEY MESSAGES
- WARMER AND DRIER WEATHER EXPECTED THROUGH MIDWEEK. THIS WILL
LEAD TO ELEVATED FIRE WEATHER CONCERNS.
- A PATTERN CHANGE IS EXPECTED AT THE END OF THE WEEK THAT WILL
BRING COOLER TEMPERATURES AND PRECIPITATION CHANCES, INCLUDING
SHOWERS, STORMS, AND THE RETURN OF WIDESPREAD SNOW.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED AT 241 PM MDT TUE APR 15 2025
VISIBLE SATELLITE SHOWS BARELY A CLOUD IN THE SKY OVER THE CWA
THIS AFTERNOON THANKS TO THE UPPER-LEVEL RIDGE OVERHEAD.
TEMPERATURES ARE WARMER THAN YESTERDAY, WITH MUCH OF THE CWA
CURRENTLY SITTING IN THE 60S AND 70S. VERY DRY CONDITIONS ARE
ALSO PRESENT, WITH SOME LOCATIONS ACROSS SOUTHEAST WYOMING
SHOWING RELATIVE HUMIDITY BELOW 15 PERCENT. LUCKILY, WINDS HAVE
BEEN RELATIVELY TAME, KEEPING CRITICAL FIRE WEATHER CONDITIONS
AT BAY.
ANOTHER HOT AND DRY DAY IS EXPECTED WEDNESDAY, ESPECIALLY EAST OF
THE LARAMIE RANGE. WITH THE RIDGE GRADUALLY SLIDING EASTWARD
THROUGHOUT THE DAY, TEMPERATURES WILL REMAIN IN THE 60S AND 70S WITH
RELATIVE HUMIDITY BELOW 15 PERCENT FOR MOST OF THE CWA. WINDS WILL
LIKELY BE A BIT STRONGER TOMORROW AS WINDS ALOFT TURN WESTERLY.
WHERE FUELS ARE READY, MARGINAL FIRE WEATHER CONDITIONS WILL BE
POSSIBLE. HOWEVER, INCREASING CLOUD COVER DURING THE AFTERNOON COULD
LIMIT THE WINDOW FOR ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS.
BY WEDNESDAY EVENING, AN UPPER-LEVEL DISTURBANCE WILL ENTER THE CWA,
BRINGING PRECIPITATION CHANCES TO THE MOUNTAINS. HI-RES GUIDANCE
SHOWS THE POTENTIAL FOR SOME SHOWERS TO SNEAK INTO THE LOWER
ELEVATIONS OVERNIGHT AS WELL, BUT THIS SHOULD CLEAR BY THURSDAY
MORNING.
A STRONGER SHORTWAVE WILL PUSH INTO WYOMING ON THURSDAY. THIS
SHORTWAVE WILL PUSH A COLD FRONT THROUGH THE CWA DURING THE DAY AND
BRING A SECOND ROUND OF FAIRLY WIDESPREAD PRECIPITATION TO THE AREA.
SURFACE TEMPERATURES WILL LIKELY BE WARM ENOUGH ACROSS MOST OF THE
CWA THAT PRECIPITATION WILL START AS RAIN, BUT QUICKLY TRANSITION TO
SNOW AFTER SUNSET AND BEHIND THE COLD FRONT. 700 MB TEMPERATURES
WILL DROP QUICKLY BELOW -10C, ALLOWING FOR WELL BELOW FREEZING
TEMPERATURES OVERNIGHT ON THURSDAY. THESE COLD TEMPERATURES WILL
LIKELY ALLOW SNOW TO ACCUMULATE IN THE LOWER ELEVATIONS ONCE THE
GROUND IS SUFFICIENTLY COLD. IT IS ALSO WORTH MENTIONING THAT MODEL
SOUNDINGS FROM THE GFS SHOW DECENT SURFACE CAPE VALUES. IT IS
POSSIBLE THAT A FEW THUNDERSTORMS COULD DEVELOP BETWEEN LARAMIE
AND SIDNEY AHEAD OF THE COLD FRONT. THE NAMNEST DOES SHOW A FEW
CELLS DEVELOPING IN THE SOUTHERN PANHANDLE THURSDAY AFTERNOON.
AS WE GET CLOSER TO THE EVENT, SNOW TOTALS WILL CONTINUE TO GET
IRONED OUT AS THIS LOOKS LIKE A MULTI-DAY STORM.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED AT 241 PM MDT TUE APR 15 2025
AN ACTIVE PATTERN MORE TYPICAL OF SPRINGTIME ACROSS OUR AREA WILL
CONTINUE INTO EARLY NEXT WEEK. ON FRIDAY, OUR AREA WILL BE IN THE
WAKE OF AN UNUSUALLY COLD STORM SYSTEM FOR THIS TIME OF YEAR. 700-MB
TEMPERATURES IN THE -8 TO -12C RANGE PER THE LREF MEAN WILL BE BELOW
THE CLIMATOLOGICAL 10TH PERCENTILE. COMBINED WITH CLOUDY SKIES AND
LOW-LEVEL UPSLOPE NORTHEASTERLY WINDS, EXPECT HIGHS PERHAPS 20F OR
MORE BELOW AVERAGE FOR MID APRIL, STRUGGLING TO BREAK FREEZING FROM
RAWLINS TO CHEYENNE, AND IN THE MID 30S TO LOWER 40S FURTHER NORTH
AND EAST. MOST SYNOPTIC FORCING WILL BE TO OUR SOUTH BY DAYBREAK
FRIDAY, BUT THE UPSLOPE FLOW AND MODEST FRONTOGENESIS RESULTING FROM
THE SURFACE FRONT GETTING CAUGHT UP ALONG THE TERRAIN BARRIER WILL
KEEP SNOW SHOWERS AROUND THROUGH THE DAY. THIS ACTIVITY LOOKS
LARGELY OROGRAPHIC, SO EXPECT MORE MOISTURE CLOSER TO THE MOUNTAINS,
TRAILING OFF TO THE NORTH AND EAST. THE REVERSE PRESSURE GRADIENT IS
ALSO EXPECTED TO LEAD TO SOME GUSTY NORTHEAST WINDS PARTICULARLY IN
CARBON COUNTY.
BY SATURDAY, MOISTURE ASSOCIATED WITH THIS SYSTEM SHOULD BE MAINLY
TO THE SOUTH, BUT COOL AIR WILL REMAIN IN PLACE OVER THE AREA. MEAN
700-MB TEMPERATURES ARE HOVERING IN THE -4 TO -8C RANGE SATURDAY
AFTERNOON, SUPPORTING HIGHS STILL BELOW AVERAGE BUT ROUGHLY 10F
WARMER THAN FRIDAY AS CLOUDS GRADUALLY BREAK AND CLEAR. AS THE
CLOSED LOW BEGINS TO EJECT OVER THE CENTRAL PLAINS ON SUNDAY,
ANOTHER NORTHERN BRANCH SHORTWAVE TROUGH WILL RACE INLAND. WHILE
HIGHS SHOULD GET CLOSER TO AVERAGE FOR THIS TIME OF YEAR, THE
APPROACHING TROUGH WILL PREVENT A WARM UP BACK TO THE WELL ABOVE
AVERAGE TEMPERATURES. IN ADDITION, THIS FEATURE WILL INCREASE THE
PRESSURE GRADIENT AND LEAD TO A PERIOD OF GUSTY WINDS. CURRENT
PROBABILITIES FOR HIGH WINDS FOR THE WIND PRONE AREAS GENERALLY
RANGE FROM ABOUT 10 TO 30% ON SUNDAY. EXPECT ANOTHER PERIOD OF LIGHT
MOUNTAIN SNOW SHOWERS WITH THIS WAVE, BUT SIGNIFICANT ACCUMULATION
IS NOT LIKELY. THE PATTERN WILL REMAIN ACTIVE INTO EARLY NEXT WEEK
AS A SERIES OF SHORTWAVE TROUGHS CONTINUES TO STREAM INLAND FROM THE
PACIFIC NORTHWEST. HOWEVER, THE VAST MAJORITY OF ENSEMBLE MEMBERS
SHOW SUCCESSIVE EVENTS AS FAIRLY MINOR DISTURBANCES WITH A LOW
PROBABILITY FOR WIDESPREAD PRECIPITATION.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 521 PM MDT TUE APR 15 2025
WEST FLOW ALOFT WILL CONTINUE. SCATTERED TO BROKEN CLOUDS NEAR
15000 FEET WILL OCCUR. WINDS WILL GUST TO 28 KNOTS AT RAWLINS
AND LARAMIE UNTIL 01Z, TO 20 KNOTS AT ALLIANCE UNTIL 07Z, AND
TO 28 KNOTS AT THE WYOMING TERMINALS, SCOTTSBLUFF AND SIDNEY
AFTER 15Z WEDNESDAY.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...SF
LONG TERM...MN
AVIATION...RUBIN
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