771
FXUS65 KCYS 202325
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
425 PM MST MON JAN 20 2025
KEY MESSAGES
- COLD HEADLINES REMAIN IN EFFECT FOR THE REGION THROUGH MIDDAY
TOMORROW AS WIND CHILL VALUES STAY BELOW -20, OR EVEN -30 IN
SPOTS
- WIND HEADLINES GO IN EFFECT TONIGHT FOR THE USUAL AREAS AND
EXPAND ONTO PARTS OF THE PLAINS TOMORROW FOR 60+ MPH GUSTS
- GRADUAL WARMING TREND MID TO LATE WEEK BEFORE THE NEXT
COOLDOWN AND CHANCE OF SNOW ARRIVE FOR THE WEEKEND
SHORT TERM /THROUGH TUESDAY NIGHT/
ISSUED AT 333 PM MST MON JAN 20 2025
SYNOPSIS... A HIGHLY ANOMALOUS UPPER TROUGH ENCOMPASSING MOST OF THE
CONUS AND RESPONSIBLE FOR AN EXPANSIVE DEEP FREEZE STILL CUTS ACROSS
EASTERN WYOMING TODAY, WHILE A RIDGE APPROACHES THE PACIFIC COAST.
FLOW IS NEARLY MERIDIONAL AS THE STATE LIES ON THE PERIPHERY OF THE
TWO. AT THE SURFACE, A STRONG HIGH PRESSURE LIES UNDERNEATH THE
TROUGH, WHILE ONE LOW ENCROACHES INTO MONTANA FROM ALBERTA AND
ANOTHER SPREADS INTO THE FOUR CORNERS FROM THE BAJA.
THIS EVENING INTO TONIGHT... CONTINUED THE COLD HEADLINES AS
TEMPERATURES FAILED TO OR BARELY BROKE 0F THIS AFTERNOON. KEPT THE
WARNING FOR THE WESTERN AND NORTHERN ZONES WHERE WIND CHILL VALUES
WILL LIKELY DIP BELOW -30, AND THE ADVISORY FOR FAR SOUTHEAST WYO
AND SOUTHERN NEB PANHANDLE FOR VALUES CLOSER TO -20. ACTUALLY PUSHED
FORECAST LOWS UP A COUPLE DEGREES AS GUIDANCE TRENDED WARMER. SEEMED
REASONABLE AS SUBSTANTIAL WARM AIR ADVECTION TAKES OVER AT H7 AND
WINDS INCREASE TO HELP LIMIT DECOUPLING. NEVERTHELESS, VALUES REMAIN
BITTERLY COLD, RANGING FROM MID SINGLE DIGITS BELOW ZERO NEAR I-25
CORRIDOR TO MID TEENS BELOW IN THE MOUNTAINS AND NORTHERN PANHANDLE.
HIGH WIND PRODUCTS GO INTO EFFECT AT 06Z FOR THE USUAL RANGES. THE
SURFACE PRESSURE GRADIENT RAPIDLY STEEPENS OVERNIGHT AS THE SURFACE
LOW PUSHES ONTO THE HIGH PLAINS WHILE THE 1050MB HIGH REMAINS OVER
THE COLORADO ROCKIES. THE ENVIRONMENT SUGGESTS A SLAM DUNK EVENT
WITH CRAIG-CASPER H85 HEIGHT DIFFS EXCEEDING 100M AND SIGNIFICANT
SUBSIDENCE TAKING OVER AT H7. IN-HOUSE WIND GUIDANCE SUGGESTS 90%
PROBABILITY OF HIGH WINDS FOR ARLINGTON AND BORDEAUX, INDICATING
VERY HIGH CONFIDENCE. ADDITIONALLY, FORECAST MOST LIKELY MAX WIND
GUSTS REACH 65 MPH, WHILE UPPER QUARTILE SPEEDS APPROACH 75 MPH.
TUESDAY... THE HEART OF THE UPPER TROUGH PUSHES EAST TOWARD THE
GREAT LAKES WHILE THE WEST COAST RIDGE EXPANDS ACROSS THE DESERT
SOUTHWEST, RESULTING IN MORE BROAD NORTHWEST FLOW FOR WYO. THE
SURFACE LOW NEAR THE BLACK HILLS ALSO DEEPENS SOMEWHAT, CONTINUING
THE STEEP GRADIENT ACROSS THE FORECAST AREA AND RESULTING IN
PERSISTENT 2MB/HR PRESSURE FALLS. FLOW AT H5-7 INCREASES SLIGHTLY
OVER SOUTHEAST WYO TOWARD 60 KT, WHILE THE LEADING EDGE OF A PV
ANOMALY AND 100+ KT H3 JET STREAK CROSS YELLOWSTONE. THE CRAIG-
CASPER H85 HGT DIFFS STAY ABOVE 60M EVEN INTO THE NIGHTTIME HOURS.
SHOULD SEE AN EXPANSION OF STRONG SURFACE GUSTS OFF THE HIGHER
TERRAIN AND ONTO THE SURROUNDING PLAINS, EG CENTRAL LARAMIE AND
EASTERN PLATTE COUNTIES. KEPT THE HIGH WIND WATCH FOR CENTRAL
LARAMIE, WHILE EXPANDED TO COVER THE REST OF PLATTE. WILL NEED TO
MONITOR FOR FURTHER INCLUSION FOR CONVERSE, GOSHEN, AND EASTERN
LARAMIE DEPENDING ON THE MAGNITUDE OF MIXING. THE WESTERLY DOWNSLOPE
FLOW WILL ALSO HELP PUSH DAYTIME HIGHS BACK TO SEASONAL LEVELS FOR
AREAS NEAR AND EAST OF I-25. STAYED CLOSE TO NBM MEAN FOR MAX TEMPS
AS THE ENVELOPE WAS FAIRLY NARROW AND LINED UP WITH NUMERICAL
GUIDANCE. HIGHS RANGE FROM LOWER TO MID 30S THERE AND MID 10S TO MID
20S FOR WEST OF THE RANGES. THE WARM AIR ADVECTION AT H7 TAKES A
STEP BACK TOMORROW NIGHT, BUT INCREASED CLOUD COVER AND CONTINUED
GUSTY WINDS WILL HELP KEEP MIN TEMPS ABOVE ZERO FOR THE FIRST TIME
IN SEVERAL DAYS.
LONG TERM /WEDNESDAY THROUGH MONDAY/
ISSUED AT 333 PM MST MON JAN 20 2025
ANOTHER ACTIVE WEATHER PATTERN IS ON THE HORIZON.
WEDNESDAY THROUGH FRIDAY, TEMPERATURES WILL BE WARMER COMPARED TO
THE PREVIOUS DAYS WITH THE UPPER LEVEL RIDGE ADVECTING IN A WARMER
AIRMASS. TEMPERATURES WILL SLOWLY CLIMB OVER THESE FEW DAYS
INCREASING TEMPERATURES FROM THE 20'S AND 30'S INTO THE 30'S AND
40'S FOR MAJORITY OF SOUTHEAST WYOMING AND NEBRASKA PANHANDLE.
FRIDAY MORNING INTO THE AFTERNOON THE RIDGE STARTS TO BREAKDOWN
AHEAD OF THE ARCTIC FRONT EXPECTED TO REACH US FRIDAY NIGHT INTO
EARLY SATURDAY MORNING. THIS WEEKEND, 700MB TEMPERATURES LOOK TO
RANGE FROM -18 TO -25 LIKELY TO BRING COLDER SURFACE TEMPERATURES.
LOOKING AT THE ENSEMBLE MEANS FOR THIS TIME PERIOD TEMPERATURES WILL
LIKELY BE IN THE TEENS DURING THE DAY AND INTO THE SINGLE DIGITS FOR
A MAJORITY OF THE SOUTHEASTERN WYOMING AREA WITH HIGHS BEING IN THE
LOW 20'S IN THE NEBRASKA PANHANDLE. THIS ARCTIC FRONT IS NOT LOOKING
TO BE AS STRONG AS THE PREVIOUS ONE EARLIER IN THE WEEK. A
NBM10/EURO/CANADIAN BLEND WAS USED TO CAPTURE TEMPERATURES WITHIN
THE INTERQUARTILE RANGE OF THE ENSEMBLE VALUES.
LOOKING SPECIFICALLY AT THE WINDS, THERE IS ANOTHER LIKELY WIND
EVENT OCCURRING FRIDAY INTO SATURDAY. THE GFS OMEGA FIELDS SIGNAL A
STRONG MOUNTAIN WAVE PRESENCE LATE FRIDAY MORNING, WITH MAXED OUT
DOWNWARD OMEGA VALUES JUST EAST OF THE LARAMIE RANGE. THIS SUGGESTS
THAT DOWNSLOPE WINDS COULD SPREAD OUT INTO THE ADJACENT ZONES,
INCLUDING CHEYENNE. THE CRAIG TO CASPER 850MB HEIGHT GRADIENT MAXES
OUT AT 95 METERS FRIDAY MORNING AND 65 METERS AT THE 700MB LEVEL. IN
HOUSE RANDOM FOREST GUIDANCE HAS BEEN CONSISTENTLY TRENDING WITH AN
80% PROBABILITY OF HIGH WINDS AT ARLINGTON, WITH A LOWER
PROBABILITY, AROUND 60-80%, FOR BORDEAUX. THIS EVENT WILL NEED TO BE
MONITORED AS IT GETS CLOSER, BUT FOR NOW DID INCREASE WINDS TO GET
HIGH WIND CRITERIA GUSTS INTO THE FORECAST.
AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 421 PM MST MON JAN 20 2025
NORTH FLOW ALOFT TONIGHT WILL TURN NORTHWEST ON TUESDAY AS A
SURFACE LEE TROUGH DEVELOPS.
MOSTLY CLEAR SKIES WILL PREVAIL. EXPECT LOW LEVEL WIND SHEAR AT
RAWLINS FROM 01Z TO 16Z, AT LARAMIE AND CHEYENNE AFTER 07Z, AND
AT THE NEBRASKA TERMINALS AFTER 15Z TUESDAY. WINDS WILL GUST TO
45 KNOTS AT RAWLINS AFTER 01Z, TO 40 KNOTS AT LARAMIE AND
CHEYENNE AFTER 07Z, AND TO 28 KNOTS AT THE NEBRASKA TERMINALS
AFTER 15Z TUESDAY.
CYS WATCHES/WARNINGS/ADVISORIES
WY...EXTREME COLD WARNING UNTIL 11 AM MST TUESDAY FOR WYZ101-102-
104-105-109>111-113-115-116.
COLD WEATHER ADVISORY UNTIL 11 AM MST TUESDAY FOR WYZ106>108-
117>119.
HIGH WIND WATCH FROM 11 PM MST THIS EVENING THROUGH TUESDAY
AFTERNOON FOR WYZ104.
HIGH WIND WARNING FROM 11 PM THIS EVENING TO 5 AM MST
WEDNESDAY FOR WYZ106.
HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING
FOR WYZ107-118.
HIGH WIND WARNING FROM 11 PM THIS EVENING TO 9 AM MST
WEDNESDAY FOR WYZ110.
HIGH WIND WARNING FROM 11 PM THIS EVENING TO 5 PM MST
WEDNESDAY FOR WYZ116-117.
NE...EXTREME COLD WARNING UNTIL 11 AM MST TUESDAY FOR NEZ002-003-
021-095-096.
COLD WEATHER ADVISORY UNTIL 11 AM MST TUESDAY FOR NEZ019-020-
054-055.
SHORT TERM...DS
LONG TERM...MM
AVIATION...RUBIN
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