035
FXUS65 KCYS 011256
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
656 AM MDT FRI MAY 1 2026
KEY MESSAGES
- WARMER AND DRIER WEATHER RETURNS TODAY AND WILL CONTINUE
THROUGH SUNDAY, LEADING TO ELEVATED FIRE WEATHER CONDITIONS.
- COOLER AND MORE UNSETTLED WEATHER IS EXPECTED TO RETURN MONDAY
THROUGH WEDNESDAY. RAIN SHOWERS, SNOW SHOWERS, AND
THUNDERSTORMS WILL BE POSSIBLE.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 310 AM MDT FRI MAY 1 2026
SKIES CONTINUE TO CLEAR ACROSS THE AREA THIS MORNING AS YESTERDAY'S
WEAK STORM SYSTEM PUSHES WELL TO OUR SOUTH. GOES WATER VAPOR IMAGERY
SHOWS SIGNIFICANTLY DRIER AIR IN THE MIDDLE TO UPPER ATMOSPHERE
OVERHEAD. A LITTLE BIT OF SURFACE MOISTURE STILL REMAINS, WHICH HAS
LEAD TO FAIRLY WIDESPREAD RADIATION FOG IN THE LARAMIE VALLEY. THIS
SHOULD BURN OFF WITHIN A FEW HOURS OF SUNRISE. A NARROW RIDGE WILL
ATTEMPT TO FILL IN OVER THE NORTHERN ROCKIES TODAY, BRINGING WARM
AND DRY WEATHER BACK TO THE AREA FOR THE NEXT FEW DAYS. FOR TODAY,
EXPECT 700-MB TEMPERATURES TO GRADUALLY WARM BACK TO AROUND 0C BY
THE END OF THE DAY, WHICH WILL SUPPORT HIGH TEMPERATURES NEAR
SEASONAL AVERAGES. DRY AIR ALOFT WILL MIX DOWN THIS AFTERNOON, AND
SEND HUMIDITY DOWN TO AROUND 15 TO 20%. NORTH WINDS WILL ALSO
DEVELOP OVER THE PLAINS TODAY, AND WE CAN EXPECT OCCASIONAL GUSTS OF
15 TO 25 MPH. THUS, FIRE WEATHER CONDITIONS WILL BE ELEVATED TODAY,
BUT WE SHOULD REMAIN OUTSIDE OF CRITICAL.
THE STRENGTH OF THE RIDGE OVERHEAD WILL PEAK ON SATURDAY WITH 700-MB
TEMPERATURES AROUND +3 TO +5C. HIGHS WILL CLIMB TO THE MID 60S TO
MID 70S, WHICH WILL BE ABOUT 10F ABOVE SEASONAL AVERAGES. THE
AIRMASS OVERHEAD WILL ALSO BE EXCEPTIONALLY DRY. NAEFS MEAN
PRECIPITABLE WATER VALUES ARE AROUND 0.10 TO 0.25 INCHES, WHICH IS
AS LOW AS THE 2.5 PERCENTILE FOR PORTIONS OF THE AREA. HUMIDITY WILL
EASILY DROP BELOW CRITICAL THRESHOLDS, WITH SINGLE DIGIT RH EXPECTED
TO SHOW UP OVER THE HIGH PLAINS. WITH THE RIDGE AXIS CLOSE TO
OVERHEAD, WINDS SHOULD REMAIN FAIRLY LIGHT, BUT NORTHWEST FLOW ON
THE PERIPHERY OF THE RIDGE COULD PRODUCE WIND GUSTS OF 15 TO 25 MPH
OVER THE HIGH PLAINS. THE MOST LIKELY SCENARIO KEEPS US OUT OF
CRITICAL DUE TO WINDS REMAINING TOO LIGHT, BUT WITH HUMIDITY AS LOW
AS IT IS EXPECTED TO BE, WE WILL NEED TO WATCH SATURDAY CLOSELY FOR
FIRE WEATHER CONDITIONS. SUNDAY WILL BE ANOTHER WARM DAY, BUT THE
RIDGE OVERHEAD WILL BEGIN TO WEAKEN AS A POWERFUL, CLOSED UPPER
LEVEL LOW MOVES INTO THE WEST COAST AND WEAK SHORTWAVES DROP
DOWN FROM THE NORTH. FORECAST HIGHS ARE FAIRLY SIMILAR TO
SATURDAY, BUT MOISTURE WILL BEGIN TO RECOVER FAIRLY RAPIDLY.
WHILE A WEAK BOUNDARY WILL IMPROVE DEWPOINTS ALONG AND NORTH OF
THE NORTH PLATTE RIVER VALLEY, THE MOISTURE RECOVER WILL BE
PRIMARILY ALOFT FOR THOSE FURTHER SOUTH. AS A RESULT, WE CAN
EXPECT TO SEE A RETURN OF THE AFTERNOON AND EVENING VIRGA
SHOWERS, WITH POTENTIAL FOR GUSTY WINDS.
LONG TERM /MONDAY THROUGH THURSDAY/
ISSUED AT 310 AM MDT FRI MAY 1 2026
A VERY COMPLEX AND MESSY SYNOPTIC WEATHER PATTERN IS SETTING UP FOR
THE EARLY PART OF NEXT WEEK. THE WEEKEND RIDGE WILL FADE TO THE
SOUTH AS THE SPRAWLING UPPER LEVEL LOW ELONGATES AND SPREAD INLAND.
MEANWHILE, THE BROAD UPPER LEVEL LOW OVER THE HUDSON BAY REGION WILL
RETROGRADE WESTWARD, PUSHING THE STORM TRACK OF WEAK UPPER LEVEL
SHORTWAVE TROUGHS CLOSER TO THE NORTHERN ROCKIES. WHILE THERE WILL
BE POTENTIAL FOR WIDESPREAD BENEFICIAL PRECIPITATION, THE
REALIZATION OF THIS POTENTIAL WILL DEPEND ON THE COMPLEX INTERACTION
BETWEEN THESE TWO FEATURES. BY MONDAY AFTERNOON, MOST ENSEMBLE
MEMBERS SHOW AN ELONGATED BAND OF ELEVATED MOISTURE STRETCHED ACROSS
ROUGHLY THE ENTIRE I-80 CORRIDOR THROUGH THE WESTERN US FROM
CALIFORNIA TO NEBRASKA. THIS IS SPREAD BETWEEN THE CLOSED LOW TO THE
WEST AND THE MAIN BROAD UPPER LEVEL LOW TO OUR NORTHEAST. ENSEMBLE
MEAN PRECIPITABLE WATER VALUES CLIMB ABOVE 0.5 INCHES FOR MUCH OF
THE AREA BY MONDAY AFTERNOON AS WELL. MONDAY'S PRECIPITATION CHANCES
LOOK TO BE MAINLY CONVECTIVE, BUT THIS WILL GRADUALLY BECOME MORE
SYNOPTICALLY DRIVEN HEADING INTO TUESDAY AS FRONTOGENESIS ASSOCIATED
WITH THE NORTHERN BRANCH TRAIN OF SHORTWAVES MOVES INTO THE AREA.
MOISTURE IS PLENTIFUL, BUT FORCING IS MUCH MORE MUDDLED, WHICH
INCREASES THE UNCERTAINTY REGARDING PRECIPITATION OUTCOME MONDAY PM
THROUGH TUESDAY NIGHT. THERE IS REASON FOR CAUTIOUS OPTIMISM
CONCERNING THE POTENTIAL FOR BENEFICIAL PRECIPITATION, WITH THE
HIGHEST ODDS GENERALLY ALONG THE I-80 CORRIDOR. STILL, WE ARE STILL
SEVERAL DAYS OUT AND WE HAVE SEEM MANY PROMISING SYSTEMS THIS SEASON
FIZZLE INTO NOTHING IN THE LAST FEW DAYS LEADING INTO THE EVENT.
WITHOUT A CLEAR SIGNAL FOR WIDESPREAD LIFT, THE OFFICIAL FORECAST IS
SOMEWHAT CONSERVATIVE ON BOTH POPS AND QPF.
ENSEMBLES (PARTICULARLY THE ECMWF ENSEMBLE) MADE A FAIRLY
SIGNIFICANT SHIFT TOWARDS A WETTER SOLUTION ACROSS THE I-80 CORRIDOR
LAST EVENING. LOOKING AT TOTAL QPF BETWEEN MONDAY AFTERNOON AND
WEDNESDAY MORNING, THE ECMWF ENSEMBLE JUMPED SIGNIFICANTLY IN THE
00Z SUITE. THE HIGHEST PROBABILITIES FOR BENEFICIAL MOISTURE ARE
ALONG THE I-80 CORRIDOR. CURRENTLY, LARAMIE AND CHEYENNE HAVE
ROUGHLY A 60-70% CHANCE FOR 0.25" OR MORE, AND A 40% CHANCE FOR
0.5" OR MORE. RAWLINS, WHEATLAND, SCOTTSBLUFF, AND SIDNEY ALL
HAVE AROUND A 40-50% CHANCE FOR 0.25" OR MORE, AND A 20-30%
CHANCE FOR 0.5". FURTHER NORTH, THESE PROBABILITIES DROP OFF
MORE. THE ENSEMBLE MEMBERS IN THE WETTER CLUSTERS GENERALLY HAVE
LOWER 500-MB HEIGHTS ON THE WESTERN PERIPHERY OF THE BROAD
RIDGE OVER CENTRAL NORTH AMERICA, WHEREAS MEMBERS WITH A MORE
POWERFUL RIDGE OVER THE PACIFIC NORTHWEST POSITIONED FURTHER
EAST KEEP THE AREA DRIER. ANOTHER CAVEAT TO THIS SYSTEM IS THAT
THE WETTER ENSEMBLE MEMBERS ARE ALSO THE COLDER ENSEMBLE
MEMBERS. THIS WOULD MEAN THAT IN THE WETTER SCENARIO, WE WOULD
LIKELY SEE RAIN CHANGING OVER TO SNOW MONDAY NIGHT INTO TUESDAY.
TUESDAY WOULD LIKELY BE CONSIDERABLY COLDER THAN THE CURRENT
NBM MEAN. IF THE DRIER SCENARIO PLAYS OUT, TEMPERATURES WOULD
ALSO LIKELY REMAIN WARMER. IN THIS SCENARIO, WE COULD EXPECT
SPOTTY RAIN SHOWERS, WITH SNOW MAINLY CONFINED TO AREAS ABOVE
7000 FT OR SO IN ELEVATION.
THE UNSETTLED WEATHER PATTERN WILL MOVE OUT OF THE AREA BY
WEDNESDAY MORNING. AFTER THIS, ENSEMBLES ARE IN GOOD AGREEMENT
SHOWING STRONG RIDGING WORKING BACK INTO THE AREA AND THUS
PUSHING HIGH TEMPERATURES BACK ABOVE SEASONAL AVERAGES FOR THE
SECOND HALF OF NEXT WEEK.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 525 AM MDT FRI MAY 1 2026
LAR IS DEALING WITH DENSE FOG THIS MORNING. EXPECT FOG TO BURN
OFF BETWEEN 13Z AND 15Z. VFR CONDITIONS WILL PREVAIL AFTER THAT.
ELSEWHERE, EXPECT VFR FOR THE FORECAST PERIOD. NORTHERLY WINDS
WILL OCCASIONALLY GUST TO AROUND 20 KNOTS LATE THIS MORNING
INTO THE EARLY EVENING HOURS. THE WIND DIRECTION MAY BE VARIABLE
AT TIMES OVERNIGHT.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MN
LONG TERM...MN
AVIATION...MN
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