268
FXUS65 KCYS 181002
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
402 AM MDT FRI JUL 18 2025
KEY MESSAGES
- SCATTERED PM SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS THE
AREA ON BOTH FRIDAY AND SATURDAY. A FEW STORMS WILL HAVE THE
POTENTIAL TO BECOME STRONG TO SEVERE.
- A WARMING TREND WITH MORE LIMITED PM THUNDERSTORM CHANCES WILL
TAKE OVER SUNDAY THROUGH TUESDAY.
SHORT TERM /THROUGH SATURDAY NIGHT/
ISSUED AT 400 AM MDT FRI JUL 18 2025
MOSTLY CLEAR SKIES ARE PRESENT OVER THE AREA THIS MORNING, BUT GOES
WATER VAPOR IMAGERY INDICATES THAT INCREASED MID TO UPPER LEVEL
MOISTURE HAS ALREADY PUSHED NORTHWARD INTO SOUTHERN WYOMING AND
SOUTHWEST NEBRASKA. AS THE SURFACE HIGH RETREATS EASTWARD INTO THE
GREAT LAKES REGION, MESOANALYSIS INDICATES SURFACE PRESSURE FALLS
OVER CENTRAL WYOMING. THIS PRESSURE TROUGH WILL NUDGE EASTWARD AS
THE DAY PROGRESSES, PUSHING THE DRYLINE EAST WITH IT. A SUBTLE VORT-
MAX PUSHING OUT OF THE MONSOON REGION WILL ARRIVE THIS EVENING,
PROVIDING SOME FORCING FOR ASCENT AHEAD OF IT. THANKS TO GOOD
POSITIVE THETA-E ADVECTION AND PLENTIFUL MID TO UPPER LEVEL
MOISTURE, WE CAN EXPECT FAIRLY GOOD COVERAGE OF SHOWERS AND
THUNDERSTORMS THIS AFTERNOON. SURFACE RAINFALL WILL BE MORE LIMITED
DUE TO THE BOUNDARY LAYER REMAINING QUITE DRY, BUT THERE WILL BE
AMPLE MOISTURE ALOFT TO STILL GET A FEW DOWNPOURS THROUGH THE DRY
LAYER. FOR MOST OF THE AREA, THE PRIMARY THREAT WILL BE DRY
MICROBURSTS. HOWEVER, THE DRYLINE IS EXPECTED TO STALL ALONG ROUGHLY
A DOUGLAS TO ALLIANCE LINE. NORTHEAST OF THIS LINE, MUCH IMPROVED
SURFACE MOISTURE AND SUFFICIENT DEEP LAYER SHEAR WILL LEAD TO A
HIGHER CHANCE FOR MORE ORGANIZED STRONG TO SEVERE THUNDERSTORMS. A
MARGINAL RISK FOR SEVERE WEATHER IS IN PLACE FOR MOST OF THE AREA
TODAY, WITH A WIND THREAT FOR MOST, AND A MORE LIMITED HAIL THREAT
ALONG AND NORTHEAST OF THE DRYLINE. MODEL GUIDANCE SHOWS ISENTROPIC
LIFT CONTINUING OVER THE AREA WELL INTO THE NIGHT TONIGHT,
SUGGESTING THAT SHOWERS AND THUNDERSTORMS MAY TAP INTO MODEST
ELEVATED INSTABILITY THROUGH THE EVENING AND TOWARDS EARLY SATURDAY
MORNING.
AFTER TODAY'S MONSOON SURGE, THE MID TO UPPER LEVEL MOISTURE WILL
MIX DOWN THROUGH THE BOUNDARY LAYER, RESULTING IN HIGHER HUMIDITY
ACROSS THE ENTIRE AREA TO BEGIN OUR SATURDAY. FORCING LOOKS A LITTLE
WEAKER OVERALL, SO COVERAGE OF THUNDERSTORMS MAY BE MORE LIMITED
COMPARED TO TODAY. THAT BEING SAID, WIDELY SCATTERED THUNDERSTORMS
ARE STILL EXPECTED DURING THE AFTERNOON AND EVENING HOURS SATURDAY.
THE DRYLINE WILL BE SOMEWHAT DIFFUSE, AND MORE APPARENT AS A WIND
SHIFT BOUNDARY SOMEWHERE NEAR THE WY/NE STATE LINE, BUT STRONGER
DEEP LAYER SHEAR WILL BE PRESENT TO THE EAST OF THE BOUNDARY.
FORECAST SOUNDINGS SHOW A HIGHLY UNSTABLE AIRMASS IN THIS AREA TOO,
SO ISOLATED STRONG TO SEVERE THUNDERSTORMS WILL BE ON THE TABLE ONCE
AGAIN. IF STORMS REMAIN DISCRETE, WE MAY SEE SUPERCELL
CHARACTERISTICS DEVELOP OVER THE NEBRASKA PANHANDLE. OUR AREA MAY BE
RIGHT ON THE EDGE OF THE GREATER RISK HERE WITH STORMS MOVING
QUICKLY EASTWARD AND STRENGTHENING AS THEY GO, BUT THIS DEFINITELY
WARRANTS CLOSE WATCHING OVER THE NEXT 36 HOURS.
LONG TERM /SUNDAY THROUGH THURSDAY/
ISSUED AT 400 AM MDT FRI JUL 18 2025
BY SUNDAY, OUR AREA WILL REMAIN UNDERNEATH SOUTHWEST FLOW ALOFT,
SANDWICHED BETWEEN A BROAD TROUGH OVER THE PACIFIC NORTHWEST AND A
BROAD RIDGE OVER THE CENTRAL/SOUTHERN PLAINS. AT THE SURFACE,
PRESSURE FALLS IN THE LEE OF THE MOUNTAINS WILL ONCE AGAIN NUDGE THE
DRYLINE EASTWARD, THIS TIME SETTING IT UP RIGHT AROUND THE
NORTHERN/EASTERN EDGES OF OUR FORECAST AREA. EXPECT A HOTTER AND
DRIER DAY SUNDAY AS THE MONSOON PLUME BECOMES SUPPRESSED MORE TO THE
SOUTH OF OUR AREA. OVERALL THUNDERSTORM COVERAGE LOOKS MUCH MORE
LIMITED SUNDAY COMPARED TO DAYS PRIOR, BUT WE WILL STILL PROBABLY
SEE A FEW RADAR ECHOES GOING UP IN THE AFTERNOON AND EVENING HOURS.
OUR FAR EASTERN ZONES (ALLIANCE TO SIDNEY AREA) MAY STILL NEED TO
WATCH FOR A FEW STRONG TO SEVERE THUNDERSTORMS IF THE DRYLINE ENDS
UP JUST A LITTLE FURTHER EAST THAN CURRENTLY EXPECTED. MONDAY LOOKS
LIKE MORE OF THE SAME AS OUR AREA REMAINS UNDER A FAIRLY DRY
SOUTHWESTERLY FETCH FROM THE SUBTROPICS AND THE DRYLINE CONTINUES TO
HOVER JUST ON THE EDGE OF THE FORECAST AREA. BY TUESDAY INTO
WEDNESDAY, THE BROAD PACIFIC NORTHWEST TROUGH WILL FINALLY MOVER
OVER TOP THE OF THE RIDGE AXIS. THIS MAY DROP A SURFACE HIGH
PRESSURE AND COOL FRONT IN ITS WAKE. THE TIMING ON ITS ARRIVAL
VARIES SOMEWHAT AMONGST THE SUITE OF ENSEMBLES, BUT MOST HAVE THIS
ARRIVING SOMETIME MID WEEK. OVERALL, THE ECMWF ENSEMBLE IS MORE
CONSISTENTLY SHOWING MOISTURE RECOVERY AND THUS HIGHER THUNDERSTORM
CHANCES FOR WEDNESDAY AND THURSDAY, WHILE THE GEFS SYSTEM ON BALANCE
REMAINS DRIER AND CONSIDERABLY WARMER.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 1133 PM MDT THU JUL 17 2025
MAINLY VFR EXPECTED OVERNIGHT, BUT THERE IS A CHANCE FOR LOW
CIGS TO SNEAK BACK INTO KSNY AND KAIA TOWARDS FRIDAY MORNING.
THE PROBABILITY IS TOO LOW TO ADD TO THE TAF AT THIS TIME.
OTHERWISE, EXPECT A LOW-LEVEL JET IN THE NEBRASKA PANHANDLE
THROUGH EARLY FRIDAY MORNING, WHICH MAY PRODUCE TEMPORARY GUSTY
WINDS AT THE SURFACE, AND MARGINAL LLWS WHEN THE SURFACE WINDS
ARE LIGHT.
FRIDAY AFTERNOON WILL BRING A HIGHER CHANCE FOR THUNDERSTORM
IMPACTS FOR MOST TERMINALS. GUSTY WINDS AND LIGHTNING WILL BE
THE PRIMARY HAZARDS. STORM ACTIVITY MAY CONTINUE WELL INTO THE
EVENING.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MN
LONG TERM...MN
AVIATION...MN
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