138
FXUS65 KCYS 272354
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
554 PM MDT MON APR 27 2026
KEY MESSAGES
- A MESSY PATTERN IS ANTICIPATED TODAY THROUGH MUCH OF THE
UPCOMING WEEK, ALLOWING FOR ONGOING PRECIPITATION CHANCES
ACROSS THE ENTIRE CWA. THE BEST CHANCE FOR PRECIPITATION WILL
BE MONDAY NIGHT, WITH WIDESPREAD RAIN AND SNOW SHOWERS.
- A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR THE SIERRA MADRE
AND SNOWY RANGES FROM 6PM SATURDAY THROUGH 6AM MONDAY.
- THE MESSY, UPPER-LEVEL PATTERN CONTINUES MID-WEEK THROUGH AT
LEAST FRIDAY BEFORE WEAK RIDING RETURNS FOR THE WEEKEND.
SHORT TERM /THROUGH WEDNESDAY/
ISSUED AT 237 PM MDT MON APR 27 2026
THE INTERMOUNTAIN WEST IS CURRENTLY UNDER SOME VERY BRIEF AND WEAK
RIDGING AHEAD OF THE NEXT SHORTWAVE PUSHING INTO THE HIGH PLAINS.
SOME OF THE CLOUDS HAVE DISSIPATED LEADING TO A CLEARING ALONG
THE CENTRAL PORTION OF THE SOUTHEAST WYOMING AND THE MAJORITY OF
THE SOUTHERN HALF OF THE NEBRASKA PANHANDLE. THE RAP MODEL
WANTS TO PLACE BETWEEN 200-700 JOULES OF CAPE IN THE MOUNTAINS
OF CARBON AND ALBANY COUNTY, HOWEVER A MIX OF LOW-MID LEVEL
CLOUDS HAVE KIND OF PARKED THEMSELVES OVER THAT REGION FOR MUCH
OF THE DAY. THE AREA THAT WOULD BE MOST LIKELY WITH THE HIGHEST
POTENTIAL ENERGY WOULD BE THE AREA THAT HAVE CLEARED OUT THIS
MORNING TO ALLOW DIURNAL HEATING TO MAKE THE AREA WEAKLY
UNSTABLE. THERE SHOULD BE ENOUGH CAPE FOR RAIN SHOWERS TO
UTILIZE THE ENERGY TO CREATE A VERY WEAK UPDRAFT SEPARATING THE
ICE CRYSTALS IN THE CLOUD, POLARIZE THE SHOWER, AND PRODUCE SOME
BOLTS OF LIGHTNING MUCH LIKE YESTERDAY. SOME LIGHT SHOWERS HAVE
ALREADY BEGUN TO FORM IN THE MOUNTAINS AND THESE SHOWERS ARE
EXPECTED TO MOVE NORTHEAST FROM THE SIERRA MADRE AND SNOWY
MOUNTAIN RANGES. A FAST MOVING TROUGH WILL IMPACT THE REGION
LATER TONIGHT. LOOKING AT LOW-LEVEL WATER VAPOR AND SURFACE
OBSERVATIONS THERE IS A SUFFICIENT AMOUNT OF MOISTURE FOR THE
WAVE TO LIFT. SOME LOBES OF STRONG VORTICITY WITH MODEST WARM
AIR ADVECTION (WAA) SHOULD GIVE US DECENT PRECIPITATION AMOUNTS
INTO THE OVERNIGHT PERIOD. THE HI-RES MODELS GENERALLY PUT THE
HIGHEST ACCUMULATIONS IN THE SUMMIT/FOOTHILL AREA BETWEEN
LARAMIE AND CHEYENNE AROUND MIDNIGHT TONIGHT. THIS CORRELATES TO
THE TIMING OF THE TROUGH AXIS AND STRONGEST WAA PUSHING THROUGH
OUR SECTION OF THE INTERMOUNTAIN WEST. AS THE WAVE PUSHES
THROUGH OVERNIGHT, THE SHOWERS SHOULD SLOWLY PUSH NORTHEAST WITH
SOME AREAS EXPERIENCING THE COLD RAIN TRANSITION TO A LIGHT
SNOW OVERNIGHT. OUTSIDE OF THE THE MOUNTAIN RANGES, SNOW
ACCUMULATIONS WILL GENERALLY RANGE FROM A VERY LIGHT DUSTING TO
POSSIBLY 0.5INCHES. THERE MAY BE SOME VERY ISOLATED AREAS THAT
MAY SEE AN INCH OF SNOW OVERNIGHT BUT ITS VERY LOW CONFIDENCE AS
THE MODELS START TO DISAGREE HOW THE SHOWERS WILL EVOLVE
OVERNIGHT DUE TO DIFFERENT PLACEMENT OF ENHANCED PRECIPITATION
PAST THE FOOTHILLS. FOR WEDNESDAY, A WEAK SHORTWAVE EJECTS OUT
OF THE PARENT LOW OVER THE HUDSON BAY LEADING TO A SLIGHT TROUGH
TO DIVE THROUGH THE INTERMOUNTAIN WEST. MOST MODELS AREN'T
"EXCITED" BY THIS WAVE IN ANY MEANS BUT SOME SHORT LIVED SHOWERS
MAY BE PRODUCED AS THERE LOOKS TO BE SOME VORTICITY TO ENHANCED
THE SYNOPTIC LIFT. MOST MODELS HAVE THE SHOWERS DISSIPATING BY
WEDNESDAY AFTERNOON WITH NO TO VERY LITTLE PRECIPITATION
ACCUMULATIONS.
TEMPERATURES THIS WEAK SHOULD BE FAIRLY CONSISTENT THE FIRST HALF OF
THE WORK WEEK AS 700MB TEMPERATURES BOUNCE BETWEEN 1C AND -3C
THROUGH WEDNESDAY AFTERNOON. THIS SHOULD KEEP THE DAILY HIGH
TEMPERATURES IN THE 40'S AND 50'S WITH OVERNIGHT TEMPERATURES IN THE
20'S AND 30'S.
LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
ISSUED AT 237 PM MDT MON APR 27 2026
AS WE HEAD INTO THE LONG TERM PERIOD, UNSETTLED CONDITIONS WILL
CONTINUE AS THE 500MB PATTERN REMAINS ACTIVE. THIS IN PART IS DUE TO
A ROBUST UPPER-LEVEL LOW CENTERED OVER ONTARIO GIVING US
NORTHWESTERLY FLOW WITH WEAK SHORTWAVES DROPPING SOUTH INTO OUR CWA.
THIS WILL KEEP CHANCES OF PRECIPITATION ELEVATED THURSDAY INTO
FRIDAY MORNING. AS WE PROGRESS IN THIS FORECAST PERIOD, THE UPPER-
LEVEL LOW DRIFTS OFF TO THE EAST WHILE RIDGING NOSES INTO OUR CWA
FROM THE WEST. THIS WILL PUT AN END TO THE PRECIPITATION BY FRIDAY
AFTERNOON AFTER AN UNSETTLED WEEK. THE AFOREMENTIONED RIDGE WILL BE
THE PRIMARY FEATURE CONTROLLING CONDITIONS HERE LOCALLY HEADING INTO
AND THROUGH THE WEEKEND, KEEPING US DRY. KEEP IN MIND, THERE ARE
SOME DISAGREEMENT IN THE MAIN GLOBAL DETERMINISTIC MODELS (GFS AND
ECMWF) WITH THE PLACEMENT AND STRENGTH OF SAID RIDGE. WELL, ALL GOOD
THINGS WILL COME TO AN END IF YOU WANT MORE CHANCES OF
PRECIPITATION. STARTING OFF NEXT WEEK, EVEN THOUGH THERE IS SOME
MODEL SPREAD, ANOTHER ACTIVE PATTERN WILL COMMENCE AS ANOTHER UPPER
LEVEL LOW SLIDES EAST ACROSS THE INTERMOUNTAIN WEST TO OUR DOORSTEP
POSSIBLY BY TUESDAY OF NEXT WEEK. HOWEVER, THERE IS SIGNIFICANT
MODEL SPREAD WHICH CREATES UNCERTAINTY, SO OVER THE NEXT FEW DAYS WE
WILL GET A CLEARER PICTURE.
LETS BRIEFLY TALK ABOUT TEMPERATURES AND WINDS, REALLY NOTHING TO
WRITE HOME ABOUT ON EITHER. SO, THE FOCUS WILL BE ON TEMPS AND WHAT
THEY WILL DO. STARTING OUT THE LONG TERM, 700MB TEMPS REMAIN COOL
BUT GRADUALLY INCREASE BY SATURDAY INTO THE +2 TO +4C RANGE AND A
FEW DEGREES WARMER ON SUNDAY. THIS TRANSLATES TO HIGHS ON THURSDAY
CLIMBING INTO THE LOWER 50S ALONG AND WEST OF THE I-25 CORRIDOR WITH
MID-TO-UPPER 50S TO THE EAST. AS MENTIONED ABOVE, 700MB TEMPS WILL
INCREASE GRADUALLY OVER THE WEEKEND AND BY SUNDAY HIGHS WILL SOAR
INTO THE MID-TO-UPPER 60S WEST OF I-25 AND 70S TO THE EAST, WARMEST
ACROSS THE NEBRASKA PANHANDLE. THIS WONT LAST LONG AS COOLER
TEMPERATURES WILL RETURN AS WE HEAD INTO EARLY NEXT WEEK.
AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 553 PM MDT MON APR 27 2026
COMPLICATED FORECAST ASSOCIATED WITH NUMEROUS SHORTWAVE TROUGHS
PROPAGATING ACROSS SE WYOMING AND W NEBRASKA BRINGING A COMBINATION
OF PRECIPITATION, LOW CEILINGS, AND DECREASED VISIBILITY. FOR THE
WYOMING TERMINALS, EXPECT IFR CONDITIONS AFTER 02Z GIVEN
VISIBILITIES OF 2-3 SM AND CIGS BELOW 3 KFT UNTIL 16Z ONCE
PRECIPITATION IS EXPECTED TO BE TO THE EAST OVER NEBRASKA. WINDS ARE
EXPECTED TO RANGE FROM 5-10 KNOTS.
FOR THE NEBRASKA TERMINALS, PRECIPITATION COVERAGE IS EXPECTED TO
INCREASE AFTER 06Z. CIGS WILL FALL BELOW 1 KFT ESPECIALLY IN THE
VICINITY OF ANY SHOWERS RESULTING IN IFR CONDITIONS. CONFIDENCE IN
THE PRECIPITATION COVERAGE AND TIMING IS LOW AND WILL ULTIMATELY
DEPEND ON THE WHEN EXACTLY THE VORTICITY MAXIMUM EJECTS OVER OUR
REGION. 5-10 KNOT WINDS WILL BE VARIABLE IN DIRECTION THROUGHOUT THE
TAF PERIOD.
CYS WATCHES/WARNINGS/ADVISORIES
WY...WINTER WEATHER ADVISORY UNTIL 3 PM MDT TUESDAY FOR WYZ112-114.
NE...NONE.
SHORT TERM...MM
LONG TERM...RZ
AVIATION...NB
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