039
FXUS65 KCYS 090414
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
914 PM MST SAT MAR 8 2025
KEY MESSAGES
- MILD AND DRY CONDITIONS EXPECTED TO START THIS WEEKEND WITH
THE RETURN OF WINDY CONDITIONS FOR SOUTHEAST WYOMING ON
MONDAY. HIGH WIND WATCHES HAVE BEEN ISSUED FOR PORTIONS OF
THE WIND PRONE AREAS.
- THE NEXT PACIFIC STORM SYSTEM IS FORECAST TO MOVE ACROSS
WYOMING AT THE END OF NEXT WEEK.
SHORT TERM /THROUGH MONDAY NIGHT/
ISSUED AT 208 PM MST SAT MAR 8 2025
VISIBLE SATELLITE IMAGERY SHOWS BARELY A CLOUD IN THE SKY OVER THE
REGION, BUT IT ALSO SHOWS EXPANSIVE SNOW COVER OVER THE NORTHERN
HALF OF THE CWA. TEMPERATURES IN THE SNOWPACKED AREAS ARE
OVER-PERFORMING GIVEN THE AMPLE SUNSHINE, SO BUMPED UP
AFTERNOON HIGHS A BIT, MAINLY IN CARBON COUNTY AND THE NORTHERN
NEBRASKA PANHANDLE.
SUNNY SKIES WILL PERSIST INTO THE DAY SUNDAY AS THE UPPER-LEVEL
RIDGE OVER THE GREAT BASIN PUSHES EASTWARD INTO THE ROCKIES.
700 MB TEMPERATURES BY THE AFTERNOON WILL APPROACH +4C! THESE
ANOMALOUSLY WARM TEMPERATURES ARE IN THE 90TH PERCENTILE FOR
NAEFS CLIMATOLOGY, SO THE RETURN OF ABOVE AVERAGE HIGHS ARE
EXPECTED. HIGH TEMPERATURES IN THE 50S AND 60S ARE EXPECTED FOR
MOST LOCATIONS, WHICH WILL LIKELY LEAD TO MUCH OF THE EXISTING
SNOWPACK MELTING OFF IN THE LOWER ELEVATIONS. THESE ANOMALOUSLY
WARM TEMPERATURES ALOFT WILL CONTINUE INTO THE DAY MONDAY.
TEMPERATURES ON MONDAY WILL LIKELY BE EVEN WARMER THAN SUNDAY,
AIDED BY DOWNSLOPING WINDS FOR AREAS EAST OF THE LARAMIE RANGE.
HIGHS COULD EVEN APPROACH 70 DEGREES IN THE SOUTHERN NEBRASKA
PANHANDLE! PRECIPITATION IS NOT EXPECTED DURING THIS TIME AS
SUBSIDENCE UNDER THE RIDGE KEEPS CONDITONS DRY.
DESPITE THE PLEASANT WEATHER, HIGH WINDS MAY ONCE AGAIN REAR ITS
PESKY HEAD SUNDAY NIGHT INTO MONDAY. THE UPPER-LEVEL RIDGE ON MONDAY
WILL WEAKEN AND FLATTEN OUT AS A SHORTWAVE MOVES ALONG THE
CANADIAN/U.S. BORDER. THIS WILL LEAD TO FAST FLOW ALOFT AS 500
MB HEIGHT GRADIENTS COMPRESS ACROSS WYOMING. ALTHOUGH THE
SIGNAL FOR HIGH WINDS IS NOT OVERLY STRONG, IT IS STILL THERE.
800 TO 700 MB WINDS MAX OUT AT 50 TO 55 KTS WITH STRONG
SUBSIDENCE OVER THE USUAL SOUTHEAST WYOMING WIND PRONES.
GRADIENTS, BOTH HEIGHT AND MSLP, LOOK RATHER UNIMPRESSIVE FOR
THIS EVENT. DID STILL DECIDE TO ISSUE A HIGH WIND WATCH FOR
BORDEAUX, ARLINGTON, AND EAST PLATTE COUNTY. HIGH WINDS LOOK
MOST LIKELY IN THESE AREAS AS THEY ARE COLOCATED WITH THE
STRONGEST WINDS AND SUBSIDENCE. WILL ALSO HAVE TO MONITOR
CONVERSE COUNTY FOR POTENTIAL HIGH WINDS, BUT HELD OFF FOR NOW
AS THE WIND DIRECTION IS NOT THE MOST FAVORABLE. WINDS WILL BACK
OFF LATE MONDAY AFTERNOON, WITH HIGH WIND WATCHES ENDING AT 5 PM
MONDAY.
LONG TERM /TUESDAY THROUGH SATURDAY/
ISSUED AT 208 PM MST SAT MAR 8 2025
AFTER MILD AND DRY WEATHER FOR MOST OF THE WEEK, ANOTHER STORM
SYSTEM IS EXPECTED TO PUSH THROUGH THE AREA TOWARDS THE END OF THE
WEEK. ON TUESDAY, EXPECT MORE ABOVE AVERAGE TEMPERATURES, THOUGH
PERHAPS A FEW DEGREES COOLER THAN MONDAY THANKS TO A SLIGHT DROP
BEHIND A SHORTWAVE PASSING TO OUR NORTH, AND A LITTLE BIT MORE CLOUD
COVER. WEDNESDAY SHOULD BE A TOUCH WARMER WITH MORE SUNSHINE. THE
INFLUENCE OF THE NEXT STORM SYSTEM MAY BEGIN TO BE FELT ON THURSDAY
AS A DEEP TROUGH DIGS IN ALONG THE WEST COAST. AS IS TYPICAL, THE
DOWNSTREAM RIDGE WILL AMPLIFY OVER THE PLAINS WITH SOUTHWEST FLOW
INCREASING OVER THE REGION. DESPITE INCREASING CLOUD COVER, MOST OF
THE AREA SHOULD REMAIN FAIRLY WARM THURSDAY. THERE WILL ALSO BE A
CHANCE FOR HIGH WINDS IN THE TYPICAL SOUTHWEST FLOW AREAS. CURRENT
MODEL GUIDANCE SHOWS UNIMPRESSIVE SURFACE PRESSURE GRADIENTS, BUT A
DECENT SIGNAL FOR HIGH WINDS ALOFT. NAEFS MEDIAN 700-MB WINDS OVER
KRWL ARE AT 49 KNOTS THURSDAY MORNING. IN-HOUSE GUIDANCE GIVES ABOUT
A 30 TO 40% CHANCE OF HIGH WINDS ALONG I-80 FROM RAWLINS TO
ARLINGTON.
AFTER THAT, ATTENTION SHIFTS TO THE POWERFUL PACIFIC TROUGH EXPECTED
TO CROSS THE ROCKIES AND EJECT INTO THE PLAINS BETWEEN LATE THURSDAY
AND EARLY SATURDAY. ESSENTIALLY ALL ENSEMBLE MEMBERS SHOW A POTENT
TROUGH MOVING THROUGH IN THIS TIME PERIOD, BUT THERE ARE SUBSTANTIAL
DIFFERENCES IN TIMING AND EXACT LOCATION WHICH COULD AFFECT THE
PRECIPITATION OUTCOME. CLUSTER SEPARATION IS PRIMARILY JUST BETWEEN
THE MAJOR ENSEMBLE SYSTEMS. THE ECMWF ENSEMBLE SHOWS A SHALLOWER,
MORE PROGRESSIVE, AND LESS NEGATIVELY TILTED TROUGH THAT IS SLOWER
TO ARRIVE, WHILE MOST GEFS MEMBERS HAVE A DEEPER UPPER LEVEL LOW
THAT CLOSES OFF FASTER, ARRIVES SOONER, AND BECOMES MORE NEGATIVELY
TILTED. THIS IS THE PRIMARY DIFFERENCE SEPARATING QPF BETWEEN
MEMBERS, WITH THE GEFS MEAN SIGNIFICANTLY HIGHER THAN THE ECMWF
ENSEMBLE MEAN. THERE ARE ALSO QUITE A FEW SIMILARITIES TO THE STORM
SYSTEM FROM EARLY LAST WEEK. THE PROGRESSIVE NATURE WILL MAKE IT
DIFFICULT TO WRAP UP THE TROWAL IN TIME FOR OUR AREA, AND SOME
MEMBERS SHOW ANOTHER ELONGATED UPPER LEVEL LOW THAT MAY FORCE
MOISTURE ON A LONGER ROUTE. ON THE FLIP SIDE, THERE ARE ALSO A FEW
ITEMS THIS SYSTEM HAS GOING FOR IT THAT THE LAST ONE LACKED,
INCLUDING A MORE FAVORABLE TRACK OF THE UPPER LEVEL AND SURFACE LOW,
MUCH STRONGER AND MORE RAPID SURFACE CYCLOGENESIS (MODELS ARE
BORDERING ON MEETING CRITERIA FOR A BOMB CYCLONE, I.E. A 24-MB DROP
IN 24 HOURS OR LESS), AND THUS MORE SUBSTANTIAL FRONTOGENESIS ON THE
BACK SIDE THAT COULD OVERCOME THE LESS FAVORABLE NORTHWEST SURFACE
WIND DIRECTION. WE ARE STILL OVER 5 DAYS AWAY FROM THIS SYSTEM, SO
ITS NOT WISE TO GET TOO FAR INTO THE WEEDS THAT WILL LIKELY CHANGE
IN THE COMING DAYS. BUT, THE OVERALL TAKE-AWAY AT THIS TIME IS THAT
THERE IS HIGH CONFIDENCE IN A POWERFUL STORM MOVING THROUGH THE AREA
AROUND FRIDAY. STRONG WINDS DURING AND AFTER THE SYSTEM ARE VERY
LIKELY AS WELL. WHETHER THE SNOW AMOUNTS ARE ENOUGH TO MAKE THIS A
MAJOR SYSTEM REMAIN HIGHLY UNCERTAIN AT THIS TIME, BUT THE MOST
LIKELY SCENARIO IS ADVISORY-LEVEL SNOWFALL AMOUNTS THAT COULD BE
PACK A SLIGHTLY HIGHER IMPACT DUE TO THE STRONG WINDS.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 911 PM MST SAT MAR 8 2025
NORTHWEST FLOW ALOFT WILL CONTINUE. MOSTLY CLEAR SKIES WILL
PREVAIL WITH OCCASIONAL SCATTERED CLOUDS NEAR 15000 FEET. WINDS
WILL GUST TO 21 KNOTS AT RAWLINS UNTIL 15Z, WITH WINDS GUSTING
TO 32 KNOTS AT ALL TERMINALS AFTER 15Z.
CYS WATCHES/WARNINGS/ADVISORIES
WY...HIGH WIND WATCH FROM SUNDAY EVENING THROUGH MONDAY AFTERNOON
FOR WYZ106.
HIGH WIND WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY
AFTERNOON FOR WYZ107.
HIGH WIND WATCH FROM MONDAY MORNING THROUGH MONDAY AFTERNOON
FOR WYZ110.
NE...NONE.
SHORT TERM...SF
LONG TERM...MN
AVIATION...RUBIN
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