643
FXUS65 KCYS 291739
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1039 AM MST WED JAN 29 2025
KEY MESSAGES
- DRY AND FAIRLY TRANQUIL WEATHER IS EXPECTED THROUGH WEDNESDAY.
EXPECT MILD TEMPERATURES ALONG AND EAST OF I-25, BUT AREAS TO
THE WEST WILL REMAIN COLD, ESPECIALLY AT NIGHT.
- THERE IS A SLIGHT CHANCE FOR STORM SYSTEM TO IMPACT THE FAR
SOUTHEAST PORTION OF THE FORECAST AREA WEDNESDAY NIGHT AND
THURSDAY.
- WIDESPREAD STRONG WINDS RETURN FOR THE WEEKEND ALONGSIDE
SEASONABLY WARM TEMPERATURES.
SHORT TERM /THROUGH FRIDAY/
ISSUED AT 411 AM MST WED JAN 29 2025
QUIET WEATHER CONTINUES THROUGH THE DAY AS THE SURFACE HIGH MOVES
FURTHER SOUTHEAST CREATING SOME CALMER WINDS FOR TODAY. TRIED TO
GUAGE THE DIURNAL TREND FOR LARAMIE AND RAWLINS AS TEMPERATURES AND
DEWPOINTS WERE SEVERAL DEGREES OFF FROM OBSERVATIONS. TWEAKED
TEMPERATURES FOR RAWLINS TO HAVE A HIGH TEMPERATURE OF 25 AS
MOST OF THE ENSEMBLES HAD THE HIGH TEMPERATURE IN THE LOW TO
UPPER 20'S COMPARED TO THE NBM'S 31 DEGREES. FOR LARAMIE THE
ENSEMBLES PLACED THE HIGH TEMP IN THE MID 30'S WHILE THE NBM HAD
LARAMIE'S TEMP IN THE LOW 40'S. TONIGHT INTO TOMORROW MORNING,
THE CLOSED LOW BEGINS TO EJECT NORTHEAST FROM THE SOUTHWESTERN
DESERT INTO THE HIGH AND CENTRAL PLAINS. HI-RES GUIDANCE SHOWS A
SLIGHT JOT TO THE NORTHWEST AS THE SYSTEM WOBBLES AS IT PASSES
THROUGH THE HIGH PLAINS. IT DOES LOOK TO JUST SWIPE THE SOUTHERN
BORDERING COUNTIES OF THE NEBRASKA PANHANDLE. HI-RES GUIDANCE
DOES PLACE A SMALL FRONTOGENTICAL BAND OVER THE PANHANDLE BUT
UNCERTAIN IF THE MOISTURE CONTENT WILL BE THERE FOR ANYTHING
SUBSTANTIAL. THE HREF PLACES A PROBABILITY OF EXCEEDING 0.01
INCHES FOR QPF DURING THAT TIME FRAME. HOWEVER, WITH THAT
FRONTOGENTICAL BAND AND SOME WEAK DIVERGENCE ALOFT, A LITTLE BIT
MORE QPF MAY BE ABLE TO BE SQUEEZED OUT. THE QPF FROM WPC WAS
CUT IN HALF AS GUIDANCE BETWEEN THE HI-RES, ENSEMBLES, AND
GLOBAL MODELS ALL HAD A COUPLE HUNDREDTHS FOR OUR REGION.
LOOKING AT THE MODEL SOUNDINGS, THE ATMOSPHERE REMAINS
UNSATURATED AT THE SURFACE AND ABOVE 650MB. SO BETWEEN 700MB AND
650MB IS WHERE MAJORITY OF OUR MOISTURE CONTENT LIES. THE
SOUNDINGS ALSO SUGGEST THAT WE DONT REMAIN SATURATED FOR LONG
(ONLY A COUPLE HOURS). SO ITS FAIRLY UNCERTAIN HOW MUCH WILL
REACH THE SURFACE WITH A 100MB LAYER OF DRY AIR BENEATH IT. THE
LOW SHOULD MOVE OUT OF THE AREA THURSDAY AFTERNOON, WITH A
SLIGHTLY BREEZY NORTH WIND DEVELOPING OVER THE HIGH PLAINS IN
ITS WAKE.
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
ISSUED AT 411 AM MST WED JAN 29 2025
ZONAL FLOW IN THE LONG TERM WILL LEAD TO AN ACTIVE PERIOD OF WEATHER
ACROSS THE CWA. THE ZONAL FLOW PATTERN BEGINS ON FRIDAY AS AN UPPER-
LEVEL LOW PUSHES OUT OF THE REGION AND INTO THE CENTRAL PLAINS. THIS
WILL SET THE STAGE FOR ZONAL FLOW ACROSS CONUS FOR AN EXTENDED
PERIOD OF TIME. ALTHOUGH LONG RANGE MODELS ARE IN AGREEMENT
REGARDING A ZONAL FLOW PATTERN, BOTH THE GFS AND ECMWF ARE
CONFLICTED IN WHERE THE 250 MB JET SETS UP. THIS DETAIL IS VITAL
SINCE IT WILL LARGELY DETERMINE WIND, PRECIPITATION, AND
TEMPERATURES ACROSS THE FORECAST AREA IN THE LONG TERM.
THE GFS HAS THE MORE ACTIVE PATTERN OF THE TWO MODELS, PREDICTING A
250 MB JET IN A MORE SOUTHERN POSITION OVER THE CWA. THIS SET UP
LEADS TO A PROLONGED PERIOD OF HIGH WINDS AS THE JET SITS DIRECTLY
OVERHEAD. IT COULD ALSO LEAD TO A PROLONGED PERIOD OF PRECIPITATION
AS WELL, WITH MID-LEVEL MOISTURE BEING FUNNELED IN FROM THE PACIFIC.
STARTING WITH THE WINDS, THE GFS SHOWS AN UPTICK IN 700 MB WINDS
FRIDAY AFTERNOON IN RESPONSE TO AN INCREASING MSLP GRADIENT ACROSS
THE CWA. 700 MB CAG-CPR HEIGHT GRADIENTS WILL STAY ABOVE 55 METERS
FRIDAY NIGHT AND THROUGH THE WEEKEND. WINDS ALOFT WILL MAX OUT
AROUND 70 KTS WITH PLENTY OF SUBSIDENCE TO BRING THESE WINDS DOWN TO
THE SURFACE. STRONGEST WINDS WILL LIKELY OCCUR FRIDAY NIGHT INTO
SATURDAY, HOWEVER, HIGH WINDS ARE EXPECTED TO CONTINUE ON SUNDAY.
THE FIRST HALF OF THIS WIND EVENT LOOKS TO BE FAIRLY WIDESPREAD.
HIGH WINDS WILL BE LIKELY IN THE SOUTHEAST WYOMING WIND PRONES. BUT,
HIGH WINDS WILL HAVE THE POTENTIAL TO SPREAD INTO WIND PRONE
ADJACENT AREAS, AND PERHAPS EVEN INTO THE NEBRASKA PANHANDLE! 60 KT
WINDS WITH GOOD SUBSIDENCE COULD GET THESE WINDS DOWN TO THE
SURFACE. IN-HOUSE GUIDANCE IS ALREADY ADVERTISING HIGH WINDS IN BOTH
THE WIND PRONES AND WIND PRONES ADJACENT AREAS THIS WEEKEND.
ASIDE FROM WIND, THE GFS IS ALSO ADVERTISING A WETTER WEEKEND.
PRECIPITATION WILL BEGIN TO MAKE ITS WAY INTO THE HIGH TERRAIN AS
EARLY AS FRIDAY, SPREADING OUT INTO THE PLAINS BY SUNDAY. FROM
THERE, PRECIPITATION WILL LINGER ACROSS MUCH OF THE CWA THROUGH THE
BEGINNING OF NEXT WEEK. THIS PATTERN WILL ALSO LEAD TO COOLER
TEMPERATURES THIS WEEKEND AND NEXT WEEK DUE TO INCREASED CLOUD COVER
AND THE FARTHER SOUTH POSITIONING OF THE JET.
THE ECMWF STILL SHOWS A BREEZY SOLUTION, WITH THE JET JUST A
BIT FURTHER NORTH COMPARED TO THE GFS. HOWEVER, THE LOCATION OF
THIS JET DOES LEAD TO DRIER CONDITIONS, WITH MOST MOISTURE
GETTING CAUGHT UP IN THE HIGH TERRAIN OF WESTERN WYOMING. THE
CAVEAT IS THAT THE ECMWF DOES SHOW A WARMER WEEKEND AND WARMER
TEMPERATURES NEXT WEEK AS 700 MB TEMPERATURES STAY AROUND 0C AND
ABOVE.
GIVEN THE LACK OF MODEL AGREEMENT, DECIDED TO RUN A MAJORITY OF THE
LONG TERM WITH THE NBM. HOWEVER, DID INCREASE WINDS ACROSS THE
FORECAST AREA FRIDAY THROUGH SUNDAY TO ACCOUNT FOR THE POSSIBILITY
OF HIGH WINDS. DID ALSO INCREASE POPS SLIGHTLY ABOVE THE NBM TO
ACCOUNT FOR THE GFS PRECIPITATION CHANCES OVER THE WEEKEND AND INTO
THE BEGINNING OF NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1036 AM MST WED JAN 29 2025
AVIATION CONCERNS REMAIN MINIMAL FOR MOST TERMINALS OVER THE
NEXT 24 HOURS, WITH VFR CONDITIONS ALONGSIDE WINDS GENERALLY 10
KNOTS OR LESS. KSNY WILL HAVE A CHANCE OF LIGHT SNOW TOMORROW AS
A BAND SETS UP JUST TO THE SOUTH OF THE TERMINAL. HIGH
RESOLUTION GUIDANCE CONTINUES TO BE SPREAD ON THE POSSIBILITY OF
ACTIVITY HERE, BUT THERE IS MODERATE TO HIGH CONFIDENCE THAT
HEAVIER SNOW WILL REMAIN TO THE SOUTH. ADDED A PROB30 FOR LIGHT
SNOW BETWEEN 12-18Z TO ACCOUNT FOR A LIGHT SNOW SHOWER OR TWO
MOVING INTO THE SITE AND BRINGING MVFR CONDITIONS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MM
LONG TERM...SF
AVIATION...CG
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