818
FXUS65 KCYS 132029
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
229 PM 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 TUESDAY.
- A COLD FRONT WILL DROP TEMPERATURES BACK TO NEAR
CLIMATOLOGICAL AVERAGE FOR MONDAY.
SHORT TERM /THROUGH TUESDAY NIGHT/
ISSUED AT 229 PM MDT SUN APR 13 2025
THIS SUNDAY AFTERNOON, HAVE A COUPLE SHOWERS ALONG THE I-80 CORRIDOR
EAST OF I-25. WHILE THE RADAR IS LOOKING BUSY ACROSS THE BORDER OF
COLORADO AND WYOMING, IT DOESN'T APPEAR AS TO ANYTHING IS MAKING IT
TO THE GROUND AS EXPECTED. RH VALUES RANGE BETWEEN 14 TO 35 ACROSS
THE FORECAST AREA SO A BRIEF SPRINKLE MAY NOT BE POSSIBLE UNTIL
LATER THIS AFTERNOON. HOWEVER, OUR VORT MAX LOOKS TO DIVE SOUTH OUT
OF OUR AREA BY 00Z. SO THESE AREAS MAY NOT SEE A DROP. NORTHERLY
WINDS LOOK TO CONTINUE FOR AREAS EAST OF I-25 UNTIL MONDAY EVENING.
SURFACE HIGH PRESSURE BEGINS TO DROP IN FROM THE NORTHWEST AS A
700MB RIDGE FORMS OVER THE ROCKY MOUNTAINS. THIS IS GOING TO
INCREASE THE WINDS MORE SO IN THE NEBRASKA PANHANDLE AND NIOBRARA
COUNTY THEN THE REST OF FORECAST AREA. IT WILL BE WINDY EVERYWHERE
TOMORROW, BUT NO HIGH WIND HEADLINES ARE EXPECTED TO BE ISSUED FOR
THE PANHANDLE AS WINDS ARE EXPECTED TO PEAK AT 30KNOTS. RH VALUES
ALSO REMAIN 17 AND 25 PERCENT IN THE PANHANDLE SO NO FIRE WEATHER
HEADLINES ARE ALSO EXPECTED, HOWEVER BOTH THE WINDS AND FIRE WEATHER
CONCERNS WILL BE IN THE ELEVATED CATEGORY. TEMPERATURES WILL REMAIN
THE SAME AS SUNDAY WITH THE HIGH TEMPERATURES REMAINING IN THE 50'S
WITH SOME ISOLATED 60'S POSSIBLE IN THE PANHANDLE. THIS IS DUE TO
THAT COOLER AIRMASS SLOWLY PUSHING EAST BUT STILL OVER US DURING THE
AFTERNOON TOMORROW. TUESDAY, THE UPPER LEVEL RIDGE SETS OVER US TO
BOOST HIGH TEMPERATURES BACK INTO THE 60'S AND 70'S WITH 30'S AND
40'S INTO THE OVERNIGHT PERIOD. HOWEVER, THE INTERMOUNTAIN WEST WILL
BE VERY DRY UNDER THIS RIDGE AS RH VALUES WILL DROP INTO THE LOW
TEENS. GUSTY WINDS HOWEVER WONT BE THERE TO MEET THE 35 MPH CRITERIA
BUT WE MAY GET CLOSE ON TUESDAY. WITH NEAR CRITICAL FIRE WEATHER
CONDITIONS PRESENT ON TUESDAY, GOING TO MONITOR MODELS TRENDS FOR
POSSIBLE FIRE WEATHER HEADLINES.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
ISSUED AT 229 PM MDT SUN APR 13 2025
THE LONG TERM FORECAST WILL SEE A SWITCH TO A COOLER AND MORE ACTIVE
PATTERN LATER IN THE WEEK. STARTING WEDNESDAY NIGHT, BOTH THE GFS
AND ECMWF SHOW AN UPPER-LEVEL CLOSED LOW FROM CANADA DROPPING DOWN
INTO THE PACIFIC NORTHWEST. THIS LOW WILL SLOWLY DIVE SOUTH THROUGH
THE END OF THE WORK WEEK AND INTO THE WEEKEND AND LARGELY BE
RESPONSIBLE FOR THE COOLER TEMPERATURES AND PRECIPITATION CHANCES
DURING THIS TIME.
AHEAD OF THIS SYSTEM, A WEAK UPPER-LEVEL DISTURBANCE WILL PASS OVER
THE CWA WEDNESDAY NIGHT. MODELS ARE IN GOOD AGREEMENT, SHOWING SOME
LIGHT PRECIPITATION OVERNIGHT, MAINLY ALONG THE INTERSTATE 80
CORRIDOR AND WEST OF INTERSTATE 25. IMPACTS WILL LIKELY BE MINIMAL,
HOWEVER THE MOUNTAINS COULD SEE SOME LIGHT ACCUMULATIONS. HEADING
INTO THURSDAY, MODELS SHOW A BIT MORE DISAGREEMENT. DESPITE UPPER-
LEVEL LOW PLACEMENT BEING NEARLY IDENTICAL IN IDAHO, THE ECMWF IS
SPEEDIER TO PUSH THE COLD FRONT INTO THE CWA BY THURSDAY AFTERNOON.
THE GFS IS MUCH SLOWER, SHOWING FRONTAL PASSAGE BY EARLY FRIDAY
MORNING. THE SPEEDIER FRONT RESULTS IN A WETTER SOLUTION FOR
THURSDAY, WHILE THE SLOWER FRONT RESULTS IN A WETTER FRIDAY. BY
SATURDAY, THE UPPER-LEVEL LOW WILL DIVE INTO THE GREAT BASIN,
RESULTING IN MOSTLY DRY CONDITIONS. THE MOUNTAINS WILL LIKELY STILL
HANG ON TO SOME LINGERING MOISTURE WHICH COULD LEAD TO CONTINUED
LIGHT SNOW AT HIGHER ELEVATIONS.
TEMPERATURES WILL GRADUALLY DECREASE THROUGH THE END OF THE
WORK WEEK THANKS TO THE INCOMING COLD FRONT. TEMPERATURES WILL
START ABOVE AVERAGE ON WEDNESDAY, BUT DROP TO BELOW AVERAGE BY
FRIDAY AS 700 MB TEMPERATURES FALL BELOW 0C. GIVEN THESE COOLER
TEMPERATURES, IT IS POSSIBLE FOR SOME OF THE LOWER ELEVATION
LOCATIONS TO SEE SOME MINOR SNOW ACCUMULATION, ESPECIALLY AT
NIGHT WITH TEMPERATURES BELOW FREEZING. TEMPERATURES WILL WARM
UP TO ABOUT AVERAGE ON SATURDAY AS SOME OF THE COLD AIR ALOFT IS
KICKED OUT.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1146 AM MDT SUN APR 13 2025
A COLD FRONT THAT MOVED ACROSS THE AREA EARLIER TODAY HAS BROUGHT
GUSTY WINDS TO ALL TERMINALS. THE STRONGEST WINDS ARE EXPECTED THIS
AFTERNOON IN WESTERN NEBRASKA TERMINALS WHERE WINDS COULD GUST TO 40
KTS AT TIMES. WINDS WILL SLOWLY DISSIPATE AFTER SUNSET, BUT BREEZY
CONDITIONS CAN BE EXPECTED TO CONTINUE INTO PART OF THE OVERNIGHT.
BESIDES WIND, A FEW SHOWERS AND/OR THUNDERSTORMS MAY DEVELOP AROUND
THE INTERSTATE 80 CORRIDOR BETWEEN KCYS AND KSNY. LIGHT TO MODERATE
RAIN IS POSSIBLE IN THESE SHOWERS, WHICH COULD CAUSE MINOR
VISIBILITY DROPS THIS AFTERNOON.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MM
LONG TERM...SF
AVIATION...SF
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