410
FXUS65 KCYS 131150
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
545 AM MDT TUE OCT 13 2026
KEY MESSAGES
- COOLER TEMPERATURES WILL PREVAIL FOR THE REST OF THE WEEK WITH
INCREASING CONFIDENCE IS WIDESPREAD RAINFALL TUESDAY EVENING THROUGH
THURSDAY MORNING.
- ACCUMULATING SNOW IS LIKELY ABOVE 8500 FT IN ELEVATION TUESDAY
EVENING THROUGH THURSDAY MORNING.
- NEAR FREEZING TEMPERATURES ARE POSSIBLE (20 TO 40% CHANCE EAST
OF I-25) WEDNESDAY NIGHT. A GROWING SEASON-ENDING FREEZE IS
INCREASINGLY LIKELY THURSDAY NIGHT INTO FRIDAY MORNING ACROSS
THE ENTIRE AREA.
SHORT TERM /THROUGH WEDNESDAY/
ISSUED AT 349 AM MDT TUE OCT 13 2026
AREAS OF SHOWERS ARE MOVING NORTHEAST FROM LARAMIE THROUGH GLENDO
AND LUSK. FOG IS ALSO BEING OBSERVED ALONG THE LARAMIE FOOTHILLS,
WITH PATCHY AREAS EASTWARD ALONG I-80 NEAR KIMBALL AND SIDNEY. THIS
IS SHOWING UP NICELY ON THE NIGHT FOG AND MICROPHYSICS GOES
PRODUCTS. OTHER LOCATIONS EAST OF I-25 ARE OTHERWISE UNDER A LOW
CLOUD DECK THAT MAY LOWER ENOUGH TO PRODUCE AREAS OF FOG THROUGH THE
MORNING. A SUBTLE MID LEVEL SHORTWAVE ASSOCIATED WITH THE CURRENT
SHOWER ACTIVITY WILL CONTINUE TO MOVE NORTHEAST OUT OF THE AREA
THROUGH THE MORNING. BEHIND IT SINKING AIR WILL DAMPEN MORE
WIDESPREAD RAIN POTENTIAL THROUGH THE MAJORITY OF THE MORNING
AND EARLY AFTERNOON AND REDUCE CLOUD COVERAGE. THIS REDUCED
CLOUD COVERAGE MAY ALLOW AFTERNOON HIGH TEMPERATURES TO REACH A
FEW DEGREES ABOVE THE FORECAST FOR PORTIONS OF THE SOUTHERN
NEBRASKA PANHANDLE. OTHERWISE, HIGHS ARE EXPECTED TO BE IN THE
HIGH 50S TO LOW 60S FOR MOST LOCATIONS OUTSIDE OF THE RANGES.
TOWARDS EVENING AN INCREASE IN DEEP LAYER MOISTURE AND SYNOPTIC LIFT
ON THE ADVANCING EASTERN FLANK OF THE UPPER LEVEL LOW WILL START TO
INCREASE CLOUD COVERAGE AND PRECIPITATION FROM SOUTHWEST TO
NORTHEAST. PWATS ARE ELEVATED AT BETWEEN 0.5 AND 0.75", WITH
BASICALLY THE ENTIRE AREA IN THE 90TH TO 95TH PERCENTILE FOR THIS
TIME OF YEAR. IN OTHER WORDS, SHOWERS WILL BE RATHER EFFICIENT
RAINFALL PRODUCERS, PARTICULARLY IF MORE CONVECTIVELY ENHANCED BANDS
DEVELOP. HIGH RESOLUTION MODELS ARE DEPICTING AREAS IN THE
INTERMOUNTAIN BASINS AND ALONG THE LARAMIE RANGES RECEIVING
QPFS OF BETWEEN 0.75 AND 1 INCH THROUGH WEDNESDAY MORNING. THE
UPPER ENDS OF THESE PREDICTIONS ARE UPWARDS OF 2 INCHES. NOT
IMPOSSIBLE AT LOCATIONS WHERE TRAINING CONVECTION OCCUR. IN
ADDITION TO THE WIDESPREAD RAIN IS SNOW AT MOUNTAIN PEAKS. THE
SNOW LEVELS ARE ANTICIPATED TO DROP BELOW 10 KFT AROUND SUNSET
TOMORROW ALLOWING PRECIPITATION TO TRANSITION INTO SNOW AT OUR
HIGHER ELEVATIONS. THESE LEVELS SHOULD DROP GRADUALLY THROUGHOUT
WEDNESDAY TO 9 OR 8 KFT. THE NORTHEASTERLY FLOW SHOULD BE
OPTIMAL FOR SNOWFALL ON THE NORTH AND EAST FACE OF THE SNOWY
RANGES WHERE TOTALS FOR THE FIRST HALF OF THIS EVENT ARE
FORECASTED TO REACH AROUND 8 INCHES. THERE IS A 20-30% CHANCE
THAT TOTALS REACH 12". WINTER WEATHER ADVISORIES MAY BE
NECESSARY IN THE FUTURE FOR THE SNOWY MOUNTAIN ZONES IF TRENDS
HOLD. OTHER SUMMITS LOOKS TO ALSO RECEIVE A FEW INCHES OF SNOW,
THOUGH AS MENTIONED THE FLOW IS NOT AS IDEAL OR MOISTURE
MISPLACED FOR HIGHER AMOUNTS. OVERNIGHT LOWS GENERALLY IN THE
LOW 40S TO MID 30S CAN BE EXPECTED WITH AREAS OF FOG OVER THE
NEBRASKA PANHANDLE.
A WET AND DREARY DAY IS SHAPING UP FOR WEDNESDAY AS THE UPPER LEVEL
LOW ADVANCES INTO THE CWA. MULTIPLE ROUNDS OF SHOWERS AND ISOLATED
THUNDERSTORMS CAN BE EXPECTED THROUGHOUT THE DAY. THE HREF AND SPC
REFS ARE IN GOOD AGREEMENT THAT THE FOCUS OF THIS RAIN WILL BE ALONG
THE NORTHERN AND EASTERN FOOTHILLS OF THE LARAMIE RANGE WHERE
UPSLOPE FLOW IS THE GREATEST. A LOCAL MAXIMUM OF 2 INCHES OF RAIN IS
SUPPORTED BY THESE HIGH RESOLUTION ENSEMBLE MODEL SUITES NEAR
WHEATLAND. ELEVATED WINDS NEAR THE LOW PRESSURE CENTER IN CARBON AND
ALBANY COUNTIES COULD BE EXPERIENCED. IF THE LOW PRESSURE
SYSTEM IS ON THE STRONGER ENVELOPE OF SOLUTIONS, WIND GUSTS OF
40 TO 50 MPH ARE POSSIBLE. THESE WINDS WOULD GIVE WIND CHILLS 10
DEGREES BELOW AIR TEMPERATURE. GIVEN THE WIDESPREAD SHOWER AND
CLOUD COVERAGE AFTERNOON HIGH TEMPERATURES ARE EXPECTED TO PEAK
IN THE MID 40S OVER MUCH OF OUR WYOMING AREAS AND LOW TO MID 50S
OVER THE NEBRASKA PANHANDLE.
LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
ISSUED AT 349 AM MDT TUE OCT 13 2026
PRIMARY FORECAST CONCERN WILL BE THE PACIFIC STORM SYSTEM
EXPECTED TO MOVE ACROSS THE REGION MIDWEEK, BRINGING WIDESPREAD
RAINFALL, MOUNTAIN SNOW (DOWN TO ELEVATIONS OF 7500 FEET,
POSSIBLY LOWER BUT LIMITED CONFIDENCE), WINDY CONDITIONS, AND
MUCH COOLER TEMPERATURES.
ALL MODELS SHOW THE POTENT MID TO UPPER LEVEL LOW LIFTING
NORTHEAST ACROSS COLORADO WEDNESDAY NIGHT, AND GRADUALLY INTO
SOUTHERN NEBRASKA BY THURSDAY. BOTH THE ECMWF AND GFS
DETERMINISTIC SHOW THIS GENERAL TREND, WITH THE 500MB LOW
TRACKING ACROSS NORTHEAST COLORADO. THE SURFACE LOW IS QUITE A
BIT SOUTH, SO NOT EXPECTING (SO FAR) A "SLOW" STACKED STORM
SYSTEM AT THIS TIME WITH THE SURFACE LOW DEVELOPING ACROSS
EASTERN COLORADO AND TRACKING EAST-NORTHEAST INTO EASTERN
NEBRASKA BY EARLY THURSDAY MORNING. HOWEVER, THE NAM AND
CANADIAN ARE FURTHER NORTH WITH THE STORM SYSTEM, SHOWING IT
HUGGING THE CO/WY BORDER WITH A PRONOUNCED DRY SLOT MOVING INTO
THE EASTERN PLAINS WEDNESDAY NIGHT. DUE TO THESE REMAINING
UNCERTAINTIES, DID NOT INCREASE QPF TOO MUCH WEDNESDAY NIGHT
THROUGH THURSDAY, BUT EXPECT A DECENT RAINFALL FOR MOST OF THE
EASTERN PLAINS GIVEN GOOD UPSLOPE FLOW, PERSISTENT ISENTROPIC
LIFT, AND SOME JET DYNAMICS DUE TO AN EXITING 110 KNOT JET MAX.
PRECIPITATION AND PRECIPITATION TYPE IS A LITTLE LESS CLEAR
FURTHER WEST, MAINLY ALONG AND WEST OF THE I-25 CORRIDOR. MODELS
HAVE TRENDED A BIT COLDER, LIKELY DUE TO SOME DYNAMIC COOLING
WITH THIS STORM SYSTEM. 700MB TEMPERATURES ARE NOW BETWEEN -2C
TO -5C ACROSS THE AREA. WITH AN ISOTHERMAL LAYER NOTED BETWEEN
1500 FT TO 5000 FT ON AREA SOUNDINGS, THIS IS COLD ENOUGH TO
SUPPORT SNOW, AT LEAST, DOWN TO 7000 FEET...INCLUDING THE
LARAMIE VALLEY AND THE HIGH VALLEYS ACROSS CARBON COUNTY.
FURTHER EAST, IT IS VERY CLOSE FOR ELEVATIONS DOWN TO 6000 FEET,
INCLUDING CHEYENNE, WHERE A MIX RAIN/SNOW IS CERTAINLY POSSIBLE
WEDNESDAY NIGHT INTO THURSDAY MORNING. BASED ON CURRENT MODEL
AND ENSEMBLE DATA, INTERMITTENT CHANGE OVER(S) TO SNOW AND
RAIN/SNOW MIX ARE EXPECTED BETWEEN 6500 TO 7500 FEET WHERE SOME
LIGHT ACCUMULATION POSSIBLE ON GRASSY AND ELEVATED SURFACES.
HOWEVER, MOST OF THESE VALLEYS (WEST OF THE LARAMIE RANGE) WILL
STRUGGLE WITH SOME EASTERLY DOWNSLOPE FLOW OFF THE LARAMIE RANGE
AS WINDS START TO INCREASE AND SHIFT EAST AND SOUTHEAST. THIS
IS WHY POP IS A BIT LOWER FOR LARAMIE, SARATOGA, AND RAWLINS.
HIGH CONFIDENCE THAT THE MOUNTAINS WILL RECEIVE ACCUMULATING
SNOWFALL WITH WINTER WEATHER ADVISORY CONDITIONS EXPECTED
WEDNESDAY THROUGH THURSDAY. MAY NEED TO ISSUE THESE SHORTLY, BUT
WE HAVE ADDITIONAL TIME TO FINE TUNE THE ACCUMULATION DETAILS.
THE BIGGER QUESTION IS THE ARLINGTON/ELK MOUNTAIN ARE AND THE
I-80 SUMMIT BETWEEN LARAMIE AND CHEYENNE. CURRENTLY, SNOWLEVELS
ARE LOW ENOUGH TO WARRANT WINTER WEATHER ADVISORY AMOUNTS.
HOWEVER, NOT VERY CONFIDENT ON QPF AMOUNTS IN THIS AREA AND IF
ANY SNOW WILL STICK TO THE ROADWAYS. WILL CONTINUE TO MONITOR
THIS POTENTIAL WITH FUTURE UPDATES.
OTHERWISE, MODELS HAVE TRENDED A BIT STRONGER ON WINDS LATE
WEDNESDAY NIGHT AND THURSDAY WITH A STRONGER PRESSURE GRADIENT
BEHIND THE SURFACE LOW AND 700MB WINDS INCREASING OUT OF THE
NORTH BETWEEN 40 TO 50 KNOTS. NORTH WINDS GUSTING UP TO 45 MPH
POSSIBLE THROUGH THURSDAY AFTERNOON ACROSS THE EASTERN PLAINS.
PRECIPITATION WILL DIMINISH FROM WEST TO EAST THURSDAY INTO
EARLY FRIDAY MORNING WITH CLEARING SKIES. THIS IS OUR MOST
FAVORABLE PERIOD TO SEE FROST AND A HARD FREEZE. CURRENTLY,
FORECAST LOW TEMPERATURES ARE IN THE 20S TO NEAR THE UPPER TEENS
ACROSS SOUTH CENTRAL WYOMING, INCLUDING THE LARAMIE VALLEY. MID
20S TO LOW 30S FORECAST FOR THE EASTERN PLAINS. THIS IS
GENERALLY AROUND THE 25TH TO 50TH PERCENTILE OF THE NBM AND THE
12Z GRAND ENSEMBLE WHICH SEEMS TO FIT THIS GENERAL PATTERN AS
SOME COLDER AIR SNEAKS AROUND THE BACKSIDE OF THE STORM SYSTEM
THURSDAY NIGHT. WOULD LIKE TO NOTE THAT THE NEW 00Z GRAND IS
EVEN COLDER WITH 25TH PERCENTILE LOWS AROUND THE MID TEENS TO
LOW 20S. FREEZE AND/OR FROST HEADLINES EXPECTED, BUT WILL WAIT
UNTIL THIS STORM IS THROUGH THE AREA FIRST. FRIDAY WILL BE
SEASONABLY COOL UNDER NORTHWEST FLOW ALOFT WITH HIGHS IN THE 50S
TO LOW 60S.
MEDIUM TO LONG RANGE MODELS APPEAR TO BE IN REASONABLE AGREEMENT
FOR NEXT WEEKEND, SHOWING A BROAD RIDGE AXIS TRANSLATING
EASTWARD INTO THE FRONT RANGE FROM THE EASTERN PACIFIC. EXPECT
DRIER WEATHER WITH PLEASANT DAYTIME TEMPERATURES FOR MID OCTOBER
WITH HIGHS IN THE 60S TO LOW 70S...AND SOME MID 70S FOR WESTERN
NEBRASKA. LOW TEMPERATURES WILL BE SEASONABLE AND GENERALLY IN
THE 30S TO LOW 40S INTO NEXT MONDAY MORNING.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 545 AM MDT TUE OCT 13 2026
STRONG PACIFIC STORM SYSTEM BEINGS TO TRACK EAST TOWARDS THE AREA
TODAY AS A STATIONARY FRONT LINGERS ACROSS THE MOUNTAINS OF
SOUTHEAST WYOMING. RAIN SHOWERS AND AREAS OF FOG CONTINUE THIS
MORNING WITH A BRIEF BREAK THIS AFTERNOON AND INTO EARLY THIS
EVENING AS THE STATIONARY COLD FRONT TEMPORARILY LIFTS NORTHEAST AS
A WARM FRONT. ANOTHER ROUND OF SHOWERS AND POSSIBLE THUNDERSTORMS
THIS EVENING THROUGH TONIGHT.
HAZARDS/WEATHER TRENDS: WIDESPREAD (L)IFR AND PATCHY FOG WILL
CONTINUE FOR ALL WESTERN NEBRASKA TERMINALS AND KCYS UNTIL 16Z TO
19Z WITH GRADUAL CLEARING THROUGH THE AFTERNOON. A BRIEF BREAK IN
THE SHOWER ACTIVITY UNTIL THIS EVENING. CONFIDENT ENOUGH TO ADD TS
TO A PROB30 GROUP FOR KLAR AND KCYS. OTHERWISE, SHOWER ACTIVITY AND
MVFR VIS AND CIGS WILL REDEVELOP FROM WEST TO EAST AFTER 04Z
WEDNESDAY WITH IFR CONDITIONS POSSIBLE AFTER 06Z ACROSS THE
SOUTHEAST WYOMING TERMINALS IN PERIODS OF RAIN SHOWERS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...DENSE FOG ADVISORY UNTIL 7 AM MDT THIS MORNING FOR WYZ116-117.
NE...NONE.
SHORT TERM...RV
LONG TERM...TJT
AVIATION...TJT
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