511
FXUS65 KCYS 022053
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
253 PM MDT FRI MAY 2 2025
KEY MESSAGES
- CALM AND WARM WEATHER THIS WEEKEND
- INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS MONDAY
THROUGH WEDNESDAY WITH SOME SNOW FOR OUR MOUNTAINOUS REGIONS.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 253 PM MDT FRI MAY 2 2025
UPPER LEVEL RIDGING WILL BE THE DOMINANT PATTERN FOR THE MAJORITY OF
THE SHORT TERM. THIS UPPER LEVEL RIDGE WILL PUSH DRY AIR TO THE
SURFACE TO HELP DEVELOP A STOUT DRY LAYER AT THE SURFACE. THIS DRY
LAYER WILL HELP SUPPRESS ANY CONVECTION THAT TYPICALLY LEAD TO OUR
LIGHT SHOWERS OVER THE PAST COUPLE OF DAYS. A WARMER AIRMASS WILL
RAISE THE HIGH TEMPERATURE ABOUT 10 MORE DEGREES HIGHER SATURDAY
THAN THE ONES OBSERVED TODAY. WARM TEMPERATURES AND MOSTLY CLEAR
SKIES WILL BE A GREAT START TO THE WEEKEND. THE DOWNSIDE IS THE
ELEVATED FIRE CONDITIONS DUE TO THE LOW RH VALUES BEING BETWEEN 14
AND 20. HOWEVER, THE WINDS WILL BE RATHER LIGHT/CALM ALLOWING FOR A
SLOW BURN IF A WILD FIRE WOULD DEVELOP.
SUNDAY, THE UPPER LEVEL RIDGE BEGINS TO PUSH OFF TO THE EAST AS A
BOWLING BALL OF A LOW PRESSURE SYSTEM MAKES ITS WAY NORTHEAST FROM
THE SOUTHERN PACIFIC COAST. THE LOW PRESSURE SYSTEM WILL BUTT RIGHT
UP AGAINST THE RIDGE TIGHTENING THE PRESSURE GRADIENT. WINDS IN TURN
WILL BE RATHER GUSTY EAST OF I-25 AND INTO THE NEBRASKA PANHANDLE.
WHILE THE HEIGHT GRADIENTS ARE BETWEEN -30 AND -50 INDICATING WEAK
TO MODERATE UPSLOPE, OUR IN HOUSE ALGORITHM PUTS A 20-40 PERCENT
CHANCE OF ELEVATED WINDS EAST OF LARAMIE. THE GFS OMEGA FIELDS SHOW
WEAK SUBSIDENCE ALONG THE I-80 CORRIDOR WHICH IS PROBABLY WHY OUR
ALGORITHM ISN'T TOO EXCITED ABOUT THIS POTENTIAL WIND EVENT.
HOWEVER, THERE IS A LOW LEVEL JET BETWEEN 40 TO 50KTS THAT THROUGH
DAYTIME MIXING THESE AREAS WILL BE ABLE TO TAP INTO FOR THOSE
ELEVATED WINDS. RH VALUES ARE ALSO GREATER THAN 20 FOR LIMITED FIRE
WEATHER CONCERNS ON SUNDAY. GIVEN THE CYCLONIC ROTATION OF A LOW OUR
FLOW PATTERN WILL BE FROM THE SOUTH USHERING IN MOISTURE FROM THE
GULF. SO OUR RH VALUES WILL LIKELY BE HIGHER THAN CURRENTLY PROGGED.
SUNDAY AFTERNOON, THE UPPER LEVEL LOW WILL SEND A VORTICITY MAX INTO
OUR REGION TO INCREASE PRECIPITATION CHANCES SUNDAY AFTERNOON AND
EVENING. CURRENTLY THE RAIN LOOKS TO BE CONFINED TO THE MOUNTAINOUS
REGIONS OF THE FORECAST AREA. SUFFICIENT ISENTROPIC LIFT AND THE
VORT-MAX LOOK TO HELP DEVELOP THE RAIN SUNDAY EVENING BUT DUE TO OUR
STOUT DRY LAYER MUCH OF THE LOWER ELEVATIONS ARE LIKELY TO REMAIN
DRY. DUE TO THE OMEGA BLOCK, THIS UPPER LEVEL LOW WILL RESIDE OVER
THE INTERMOUNTAIN WEST OVER THE NEXT COUPLE DAYS.
LONG TERM /MONDAY THROUGH THURSDAY/
ISSUED AT 253 PM MDT FRI MAY 2 2025
THE MAIN FOCUS OF THE FORECAST FOR NEXT WEEK WILL BE THE SPRAWLING
UPPER LEVEL LOW EXPECTED TO DELIVER SEVERAL DAYS OF UNSETTLED
WEATHER TO OUR AREA. MODEL GUIDANCE IS IN GOOD AGREEMENT DEPICTING
AN OMEGA-BLOCK SETTING UP BY THE END OF THE WEEKEND ACROSS THE
CONUS. THIS WILL BE CHARACTERIZED BY A STRONG RIDGE ALOFT OVER THE
UPPER MIDWEST, BOOKENDED BY TWO CLOSED LOWS. THE WESTERN UPPER LEVEL
LOW OVER THE DESERT SOUTHWEST WILL BE THE MAIN WEATHER MAKER OF THE
WEEK AS IT GRADUALLY MEANDERS EASTWARD UNDER THE RIDGE. BY MONDAY,
DEEP SOUTH TO SOUTHEAST FLOW WILL EXTEND ACROSS ESSENTIALLY THE
ENTIRE TROPOSPHERE, ASSISTING IN MOISTURE ADVECTION THAT WILL PUSH
PRECIPITABLE WATER TO AROUND THE CLIMATOLOGICAL 90TH PERCENTILE.
EXPECT SCATTERED TO NUMEROUS SHOWERS AND ISOLATED TO SCATTERED
THUNDERSTORMS TO FILL IN QUICKLY MONDAY AFTERNOON ACROSS THE AREA.
WITH MILD TEMPERATURES ALOFT KEEPING LAPSE RATES DOWN AND NEARLY
VERTICALLY UNIFORM WIND PROFILES, THIS DOES NOT REALLY LOOK LIKE A
SETUP FOR SEVERE WEATHER BUT IT'S HARD TO COMPLETELY RULE OUT GUSTY
WINDS AND/OR HAIL AROUND HERE WITH ANY THUNDER IN THE FORECAST.
THE BEST WINDOW FOR CONSISTENT ACROSS THE AREA LOOKS TO BE TUESDAY
AFTERNOON INTO EARLY WEDNESDAY MORNING AS THE RIDGE ALOFT EXPANDS
WESTWARD OVER THE TOP OF THE CLOSED LOW AND TILTS THE MOISTURE PLUME
MORE EAST TO WEST. DEEP, SATURATED UPSLOPE FLOW SHOULD ALLOW
STRATIFORM PRECIPITATION TO FILL IN ONCE AGAIN. PRECIPITATION TYPE
MAY BE AN ISSUE FOR PORTIONS OF WYOMING WITH THIS SYSTEM. WHILE
AREAS ABOVE ABOUT 8000 FEET CAN EXPECT RAIN CHANGING TO SNOW BY
TUESDAY MORNING, LOWER ELEVATIONS (BETWEEN 5K AND 8K FT) COULD MIX
WITH SNOW LATER TUESDAY INTO EARLY WEDNESDAY. 1000 TO 500-MB
THICKNESS AND 700-MB TEMPERATURES ARE JUST BARELY OUTSIDE OF WHAT
WE'D WANT TO SEE FOR SNOW IN RAWLINS, LARAMIE, AND CHEYENNE, WITH
ABOUT 25% OF ENSEMBLE MEMBERS SUFFICIENTLY COLD FOR SNOWFALL. WHILE
ALL OR MOSTLY RAIN IS STILL THE MOST LIKELY SCENARIO BELOW 7500 FT
OR SO IN ELEVATION, THIS COLDER SCENARIO IS WORTH A MENTION AND
ANOTHER LOOK IN THE COMING DAYS.
ENSEMBLES REMAIN FAIRLY BULLISH ON PRECIPITATION AMOUNTS THROUGH THE
MIDDLE OF NEXT WEEK. THE 50TH PERCENTILE OF STORM TOTAL QPF IS
AROUND 0.75 TO 1.0" FOR THE LARAMIE RANGE AND I-25 CORRIDOR,
DROPPING OFF BOTH TO THE WEST AND EAST TO AROUND 0.4 TO 0.6 IN BOTH
CARBON/ALBANY COUNTIES AND IN THE NEBRASKA PANHANDLE. QPF WAS NUDGED
TO THE NBM 50TH PERCENTILE, WHICH RESULTED IN A SLIGHT CUT COMPARED
TO WPC VALUES. IF WE MANAGE THE 50TH PERCENTILE, THIS SHOULD BE
BENEFICIAL MOISTURE TO ASSIST THE GREEN-UP BUT LIKELY WON'T BE
ENOUGH TO PUT MUCH MORE THAN A DENT IN THE DROUGHT. THE HIGHER END
SCENARIOS, WHILE NOT PARTICULARLY LIKELY, WOULD BE ENOUGH TO HELP
WITH THE DROUGHT SITUATION. THE LOW END SCENARIO IS STILL POSSIBLE
TOO THOUGH, AND WOULD MEAN JUST AROUND 0.1 TO 0.3" FOR MOST OF THE
AREA.
EXPECT SHOWERS TO TAPER OFF WEDNESDAY AS THE MOISTURE PLUME WEAKENS
AS IT BECOMES BISECTED BY A DRY AIR INTRUSION EXPANDING EASTWARD
ACROSS THE SOUTHERN PLAINS. THE CLOSED LOW WILL BE LEFT TO SLOWLY
DECAY THROUGH THE END OF THE WEEK, BUT SHOULD KEEP UNSETTLED WEATHER
GOING THROUGH FRIDAY. HOWEVER, ONCE IT STARTS TO WEAKEN THIS WILL BE
MORE IN THE FORM OF AFTERNOON SHOWERS AND A FEW STORMS, RATHER THAN
WIDESPREAD RAINFALL.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1135 AM MDT FRI MAY 2 2025
VFR CONDITIONS ARE EXPECTED FOR THE FORECAST PERIOD. OTHER THAN
A FEW HIGH CLOUDS FILTERING THROUGH AND SCATTERED CUMULUS
AROUND 5-6 KFT IN THE NEBRASKA PANHANDLE, SKIES WILL BE MOSTLY
CLEAR. NORTH TO NORTHWEST WINDS MAY OCCASIONALLY GUST AROUND 20
TO 25 KNOTS THROUGH THE MID AFTERNOON HOURS BEFORE WEAKENING AND
ROTATING THROUGH EASTERLY TO SOUTHERLY FOR THE OVERNIGHT HOURS
INTO SATURDAY MORNING.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MM
LONG TERM...MN
AVIATION...MN
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page