815
FXUS65 KCYS 081003
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
303 AM MST SAT MAR 8 2025
KEY MESSAGES
- MILD AND DRY CONDITIONS EXPECTED TO START THIS WEEKEND WITH
THE RETURN OF WINDY CONDITIONS FOR SOUTHEAST WYOMING ON
MONDAY.
- THE NEXT PACIFIC STORM SYSTEM IS FORECAST TO MOVE ACROSS
WYOMING AT THE END OF NEXT WEEK.
SHORT TERM /THROUGH SUNDAY NIGHT/
ISSUED AT 303 AM MST SAT MAR 8 2025
THE UPPER LEVEL RIDGE IS PUSHING INTO THE INTERMOUNTAIN WEST TONIGHT
AND TOMORROW MORNING. THIS UPPER LEVEL RIDGE LOOKS TO PROVIDE ENOUGH
SUBSIDENCE TO KEEP OUR SKIES MOSTLY CLEAR THROUGH THE WEEKEND. WITH
THE SNOWPACK SLOWLY MELTING OVER THE WEEKEND THIS WILL KEEP SOME
MOISTURE AT THE LOWER LEVELS AND HELP CREATE FOG IS SOME AREAS AS
THE MOISTURE GETS TRAPPED UNDER THE NOCTURNAL INVERSION. THIS
SNOWPACK WILL ALSO RESULT IN LOWER DIURNAL MAX TEMPERATURES COMPARED
TO WHAT THE ENSEMBLES ARE DEPICTING. A MENTION OF DENSE FOG WAS
ADDED TO THE GRIDS OVER CONVERSE AND PLATTE COUNTY AS FREEZING FOG
HAS DEVELOPED OVER DOUGLAS AND WHEATLAND WITH VARYING INTENSITIES.
RAP SOUNDINGS DEPICT THE LOWER LEVELS BECOMING UNSATURATED BY 15Z
THIS MORNING. THE RAP SOUNDINGS SHOW THE SAME OCCURRENCE TOMORROW
MORNING. SO THE FOG SIGNAL WILL BE MONITORED TO SEE IF THE TREND
CONTINUES IN LATER RUNS. TEMPERATURES HAVE BEEN RATHER TRICKY
BECAUSE OF THE NEWLY CREATED SNOWPACKS. DOUGLASS AND RAWLINS FOR
INSTANCE ARE IN THE SINGLE DIGITS WITH A POSSIBLE OVERNIGHT LOW IN
THE NEGATIVES WITH LARAMIE NOT TOO FAR BEHIND. MODEL AND ENSEMBLE
GUIDANCE ARE FRANKLY TO WARM IN THIS AREAS SO TEMPERATURE GRIDS
WHERE HAND EDITED USING AS LOW AS NBM 5TH PERCENTILE AND THEN
DROPPING IT FURTHER. TO FURTHER COMPLICATE HIGH/LOW TEMPERATURES OUR
FLOW SWITCHES FROM NORTHERLY TO A WESTERLY THIS WEEKEND FAVORING
DOWNSLOPING AND A POSSIBLE MORE RAPID MELT. THEN MONDAY CONTINUES TO
LOOK TO BE OUR NEXT ELEVATED TO HIGH WIND EVENT. MOST IF NOT ALL OF
OUR REMAINING SNOWPACK SHOULD BE WIPED OUT WITH 50/60 DEGREE DAYS
SUNDAY INTO MONDAY.
LONG TERM /MONDAY THROUGH FRIDAY/
ISSUED AT 303 AM MST SAT MAR 8 2025
ONLY A FEW MINOR CHANGES TO THE MEDIUM TO LONG RANGE FORECAST
PACKAGE AS MODELS AND ENSEMBLES REMAIN IN GOOD AGREEMENT
UNTIL FRIDAY. FOR EARLY TO MIDWEEK, RELATIVELY QUIET AND BENIGN
WEATHER IS FORECAST THROUGH WEDNESDAY WITH WIND AND TEMPERATURES
THE PRIMARY CONCERNS BEFORE THE NEXT PACIFIC STORM SYSTEM MAKES
ITS WAY INLAND WEDNESDAY NIGHT AND THURSDAY.
MAIN FORECAST CONCERN WILL BE THE POTENTIAL FOR STRONG GUSTY
WINDS ON MONDAY, AND MAYBE INTO TUESDAY MORNING. MODELS CONTINUE
TO TREND HIGHER ON 700MB WIND SPEEDS ACROSS SOUTHEAST WYOMING
WITH IN-HOUSE WIND MODELING SHOWING HIGHER PROBABILITIES FOR
STRONG WINDS...AND NOT JUST FOR THE WIND PRONE AREAS. THE
MAIN DIFFERENCE IS THE GFS AND CANADIAN SHOW A NORTHERN PACIFIC
SHORTWAVE A BIT FURTHER SOUTH THAN PREVIOUS SYNOPTIC MODELS WERE
INDICATING, AS A POTENT COLD FRONT SLIPS SOUTH INTO NORTHERN
WYOMING. THESE FEATURES ARE EXPECTED TO INCREASE THE LOW TO
MIDLEVEL PRESSURE GRADIENTS ALONG THE MOUNTAINS. PORTIONS OF
NORTHERN CARBON COUNTY, CONVERSE COUNTY, AND THE I-25 CORRIDOR
BETWEEN WHEATLAND AND CASPER HAVE TRENDED MUCH HIGHER WITH THE
POTENTIAL FOR STRONG GUSTY WINDS MONDAY. GFS AND NAM OMEGA HAVE
ALSO TRENDED MORE AGGRESSIVE WITH VALUES ABOVE -35 UB/S,
HINTING TO VERY STRONG SUBSIDENCE. MOUNTAIN WAVE SIGNATURE IS
ALSO PRESENT ACROSS SOUTHEAST WYOMING WITH SEVERAL DOWNWARD
OMEGA/UPWARD OMEGA COUPLETS FROM WEST TO EAST. IT IS LOOKING
MORE LIKELY WE'LL NEED A HIGH WIND WATCH AT SOME POINT IN THE
NEAR FUTURE IF MODEL TRENDS PERSIST. INCREASED WINDS SLIGHTLY
OVER THE PREVIOUS FORECAST WITH GUSTS AROUND 60 TO 65 MPH IN THE
WIND PRONE AREAS. EXPECT SOME OF THE STRONGER WINDS ALOFT NEAR
THE TOP OF THE BOUNDARY LAYER TO MIX DOWN TO THE SURFACE, SO THE
SUB-WIND PRONE AREAS MAY SEE GUSTS OVER 60 MPH AS WELL. THERE
IS ALSO A CHANCE THESE WINDS MAY PERSIST THROUGH MONDAY NIGHT
AND INTO EARLY TUESDAY MORNING FOR MAINLY THE WIND PRONE AREAS.
OTHERWISE, HIGH TEMPERATURES ARE STILL ANTICIPATED TO BE 10 TO
15 DEGREES ABOVE AVERAGE FOR THIS TIME OF THE YEAR WITH HIGHS IN
THE 50S TO MID 60S. BELIEVE THE SURFACE SNOW PACK EXTENDING FROM
RAWLINS NORTHEAST TOWARDS DOUGLAS/WHEATLAND AND OVER TO CHADRON
NEBRASKA WILL BE MOSTLY MELTED BY MONDAY AND TUESDAY. INCREASED
TEMPERATURES IN THESE AREAS CLOSER TO GUIDANCE.
AS WE HEAD INTO THURSDAY & FRIDAY, MODELS ARE IN GOOD
AGREEMENT WITH THE OVERALL PATTERN BUT ARE STRUGGLING WITH THE
TIMING AND EVOLUTION OF THE NEXT PACIFIC STORM SYSTEM WHICH IS
FORECAST TO INTO THE EASTERN GREAT BASIN REGION ON THURSDAY AND
EVENTUALLY INTO THE FRONT RANGE THURSDAY NIGHT OR FRIDAY. THE GFS
AND CANADIAN ARE NEARLY 12 HOURS MORE PROGRESSIVE COMPARED TO THE
ECMWF, WHICH IS TRENDING SLOWER WITH EACH MODEL RUN. THE GFS IS
SHOWING A MORE ORGANIZED STORM SYSTEM AND RAPID SURFACE CYCLOGENESIS
ACROSS FAR NORTHEAST COLORADO AND CENTRAL NEBRASKA. THE ECMWF IS
MORE DISORGANIZED AND FURTHER EAST WITH SURFACE CYCLOGENESIS.
TRENDED FORECAST TOWARDS THE ECMWF AND THE ENS ENSEMBLES, WHICH
OVERALL DID BETTER FOR THE FIRST STORM SYSTEM THIS PAST WEEK.
BLENDED POP FORECAST WITH THE CONSALL SINCE THE NBM SEEMS WAY TOO
HIGH GIVEN THE RELATIVELY LARGE TIMING DIFFERENCES BETWEEN MODELS
AND ENSEMBLE MEMBERS. REGARDLESS, WILL HAVE TO MONITOR THIS STORM
SINCE IT DOES TRACK OVER THE FOUR CORNERS REGION AND LIFTS NORTHEAST
INTO NORTHEAST COLORADO. TEMPERATURES WILL TREND MUCH COLDER BY
FRIDAY.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 912 PM MST FRI MAR 7 2025
NORTH FLOW ALOFT WILL CONTINUE. SKIES WILL BE MOSTLY CLEAR.
WINDS WILL REMAIN 14 KNOTS OR LESS.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...MM
LONG TERM...TJT
AVIATION...RUBIN
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