517
FXUS65 KCYS 051014
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
414 AM MDT SAT SEP 5 2026
KEY MESSAGES
- CHANCES FOR AFTERNOON AND EVENING THUNDERSTORMS CONTINUE UNTIL
MID WEEK.
- A TEMPORARY DRYING TREND BEGINS MID-WEEK AND POSSIBLY
CONTINUES THROUGH THE END OF NEXT WEEK.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 409 AM MDT SAT SEP 5 2026
A DEEPENING UPPER LEVEL LOW IS PUSHING INTO THE PACIFIC NW NEAR
THE BORDER OF CALIFORNIA AND OREGON. THIS UPPER LEVEL LOW WILL
HELP FEED MOISTURE INTO THE INTERMOUNTAIN WEST. THE MODEL
SOUNDINGS SHOW THE INTERMOUNTAIN WEST CLASSIC INVERTED V
SOUNDING. WITH THE IMPROVING THE SURFACE MOISTURE WILL SLOWLY
INCREASE HOWEVER, GUSTY SHOWERS WILL ALWAYS BE A POSSIBILITY AS
THIS REGION IS NOT KNOWN FOR HAVING SATURATED SOUNDINGS LIKE IN
THE SOUTHERN UNITED STATES. DCAPE IS ROUGHLY 1500-1900 JOULES
WITH MUCAPE OF 1500-2000 JOULES TO MATCH. THE UPPER LEVEL LOW
WILL SEND A SHORTWAVE THROUGH THIS REGION THIS AFTERNOON AND
EVENING. THERE IS A PRETTY STRONG CAPE IN THE MORNING AND A
CONVECTIVE TEMPERATURE IN THE UPPER 80'S TO LOW 90'S ACROSS THE
FORECAST AREA. HI-RES GUIDANCE SHOWS THE SHOWERS HAPPENING IN
TWO PHASES. THE FIRST PHASE IS LIGHT SHOWERS ALONG THE WY/NE
BORDER BETWEEN THE 15-18Z. THIS PHASE HAS LOW CONFIDENCE BECAUSE
THERE IS A LOT OF CIN IN THE MORNING AND WE WON'T HAVE THE
DIURNAL HEATING TO ERODE THE CAP LIKE WE WOULD HAVE AT AROUND
21Z OR 3PM TODAY. WHICH IS THE TIMING OF THE SECOND PHASE. THE
HRRR, NAM NEST, AND THE RRFS INITIATE CONVECTION AT THIS TIME.
HOWEVER, THE INITIATE IT ALL IN DIFFERENT PLACES. THE HRRR HAS
THE MOST NORTHERN TRACK WITH STORMS POPPING OFF AROUND THE
SCOTTS BLUFF, BOX BUTTE, MORRILL COUNTY INTERSECTION AND
QUICKLY PUSHING EAST. NAM NEST HAS THE STORMS STARTING IN
LOGAN/SEDGWICK/PHILLIPS COUNTY AREA IN COLORADO AND MOVED INTO
CHEYENNE COUNTY THEN THE STORMS QUICKLY MOVE OUT OF MY AREA AND
INTO GARDEN COUNTY. THE RRFS-MPAS VERSION IS A BLEND OF THE OF
THE TWO PREVIOUS MODELS WITH A CLUSTER OF STORMS STARTING NEAR
THE EASTERN EDGE OF MORRILL/CHEYENNE COUNTY ALONG WITH OTHER
STORMS IN THE CLUSTER OF COLORADO COUNTIES NEAR THE WYOMING/NE
BORDER. LOOKING AT THE GFS AND EURO, THEY DEPICT A STREAM OF
STRONG VORTICITY STRETCHING FROM WELD COUNTY TO GOSHEN COUNTY
THAT PUSHES EASTWARD. THIS STREAM OF VORTICITY MAY BE THE KEY TO
HELPING OUR STORMS BUSTING THROUGH THE CAP. SPC HAS HIGHLIGHTED
THE NEBRASKA PANHANDLE WITH A MARGINAL RISK FOR SEVERE
THUNDERSTORMS TODAY. THE MAIN THREATS WITH THESE STORMS WOULD BE
WIND GUSTS UP TO 60 MPH AND HAIL UP TO 1 INCH. THE HAIL SIZE
MAY BE MORE UP TO PING PONG BALLS OR 1.5 INCHES IF A
THUNDERSTORM CAN SUSTAIN ITSELF. THE EFFECTIVE SHEAR LOOKS TO BE
AROUND 24 KNOTS WITH THE OVERALL BULK SHEAR OF 30- 40KTS WHICH
MAY END UP GETTING THE JOB DONE. WE START TO LOSE MOST OF OUR
SYNOPTIC FORCING BETWEEN 06-09Z AND MOST OF THE HIGH-RES MODELS
HAVE THOSE STORMS JUST EAST OF OUR FORECAST AREA SO NOT REALLY
EXPECTING LINGERING OVERNIGHT SHOWERS BUT WE MAY HAVE STORMS
CONTINUE INTO THE NIGHT. SUNDAY, THAT UPPER LEVEL LOW SLOWLY
PUSHES AGAINST OUR RIDGE CREATING A SLIGHT TIGHTENING OF THE
HEIGHT GRADIENT FOR A BREEZY AFTERNOON AND EVENING. WITH THE
CONTINUAL FEEDING OF MOISTURE THERE WILL BE A LITTLE BIT MORE
MOISTURE FOR STORMS TO UTILIZE. OTHERWISE IT'S PRETTY MUCH A
CUT, COPY, PASTE OF SATURDAY AFTERNOON. THE BULK SHEAR WILL
REMAIN ABOUT 30-40 KNOTS WITH VORT-MAXES AS THE PRIMARY MEANS
FOR SYNOPTIC LIFT. THE DIFFERENCE IS THE CAPE VALUES REALLY
START TO DIE OFF AS THE SUN GOES DOWN AND THE STRONGER CAPE
VALUES BECOME LOCATED IN SOUTH DAKOTA BY THE EVENING INSTEAD OF
THE NEBRASKA PANHANDLE. ALSO THE EXPECTED INITIATION LOCATION IS
ALSO FURTHER WEST STARTING IN PLATTE, GOSHEN, AND EASTERN
LARAMIE COUNTY. SPC ALSO DRAWS THE MARGINAL FOR TOMORROW IN
THESE LOCATIONS AS WELL. AGAIN IT WILL BE FOR HAIL AND WIND.
HONESTLY IN OUR NECK OF THE WOODS, THE WIND COMPONENT IS ALMOST
ALWAYS A SAFE BET. THE HAIL IS KIND OF HIT OR MISS WITH EITHER
WE GET LARGE HAIL OR ACCUMULATING PEA SIZE HAIL. SO WE HAVE A
FUN WEEKEND TO LOOK FORWARD TO. THE DAILY HIGH TEMPERATURES WILL
BE IN THE 80'S AND 90'S THIS WEEKEND AS 700MB TEMPERATURES
REMAIN BETWEEN 15 AND 17C. THE OVERNIGHT TEMPERATURES WILL ALSO
CONTINUE TO BE IN THE 50'S AND 60'S MAKING THE NIGHTLY
EXPERIENCE RATHER ENJOYABLE IF ITS NOT STORMING OVER YOU.
LONG TERM /MONDAY THROUGH FRIDAY/
ISSUED AT 409 AM MDT SAT SEP 5 2026
OUR UPPER LEVEL RIDGE STARTS TO BREAK DOWN AS THE LOW CONTINUES
TO PUSH INWARD FROM THE PACIFIC NORTHWEST. THE LOW STARTS TO
MOVE NORTHWARD OVER OUR RIDGE AS IT MOVES INTO MONTANA/CANADIAN
PROVIDENCES TO THE NORTH OF US. THIS LOW WILL CONTINUE TO PUSH
SHORTWAVES THROUGH OUR REGION MONDAY AND TUESDAY FOR AFTERNOON
AND EVENING SHOWERS. THE RIDGE STARTS TO BUILD BACK OVER US
WEDNESDAY AND THURSDAY STARTING A DRYING PERIOD AS WE GO INTO A
MORE WESTERLY DOWNSLOPING FLOW. THE GLOBAL MODELS SHOW THE UPPER
LEVEL LOW OVER THE HUDSON BAY AREA AT THIS TIME WHICH IS FAR
ENOUGH EAST TO NOT INFLUENCE THE WEATHER PATTERN OVER US.
HOWEVER, EACH OF THE GLOBAL MODELS DO WANT TO BRING IN ANOTHER
SYSTEM INTO THE PACIFIC NORTHWEST AT THE END OF THE WEEK SO MORE
PRECIPITATION MAY BE ON THE WAY NEXT WEEKEND WE JUST WILL HAVE
TO WAIT TO SEE HOW THE MODELS TREND.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 1145 PM MDT FRI SEP 4 2026
OVERALL, STILL EXPECTING A QUIET OVERNIGHT AT ALL TERMINALS WITH
MOSTLY CLEAR SKIES AND LIGHT WINDS. NEWER HI-RES GUIDANCE HAS BEGUN
TO HINT AT POTENTIALLY SOME SHOWERS DEVELOPING EARLIER IN THE
MORNING AROUND KCYS AND SOME OF THE NEBRASKA PANHANDLE TERMINALS.
HOWEVER, CONFIDENCE IN THIS IS LOW, SO KEPT IT OUT OF THE TAFS FOR
NOW. A BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS IS EXPECTED
DURING THE AFTERNOON HOURS ON SATURDAY.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MM
LONG TERM...MM
AVIATION...SF
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page