734
FXUS65 KCYS 182133
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
233 PM MST WED DEC 18 2024
KEY MESSAGES
- A FAIRLY WIDESPREAD HIGH WIND EVENT WILL OCCUR TODAY AND
TONIGHT FOR THE SOUTHEAST WYOMING WIND PRONE LOCATIONS AND
NEARBY LOWER ELEVATIONS. HIGH WIND WARNINGS WILL CONTINUE FOR
THE WIND PRONE LOCATIONS AND WILL BEGIN AT 3 PM THIS AFTERNOON
FOR NEARBY LOWER ELEVATIONS. HIGH WIND WARNINGS WILL CONTINUE
UNTIL 5 AM THURSDAY.
- IT WILL STILL BE WINDY DURING THE DAYTIME ON THURSDAY, THOUGH
WINDS WILL REMAIN BELOW HIGH WIND CRITERIA.
- DRY AND MILD WEATHER WILL CONTINUE FOR FRIDAY THROUGH THE WEEKEND.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED AT 232 PM MST WED DEC 18 2024
AFTERNOON GOES SATELLITE IMAGERY OVER SOUTHEAST WYOMING REVEALS A
PATTERN OF MOUNTAIN WAVE CLOUDS AND SUBSIDENCE REGIONS INDICATIVE OF
THE HIGH-WIND EVENT CURRENTLY UNDERWAY. A STRONG PRESSURE GRADIENT,
RESULTING FROM A BROAD TROUGH OVER THE MIDWEST AND A FLAT RIDGE OVER
THE SOUTHWEST UNDERNEATH A SHORTWAVE TROUGH, WILL CONTINUE TO
PROVIDE THE INGREDIENTS FOR OUR HIGH WINDS TODAY. GUSTS OVER 50
KNOTS HAVE BEEN REPORTED IN A MAJORITY OF THE FORECAST ZONES
CURRENTLY UNDER THE WARNING, WITH GUSTS AS HIGH AS 45 KNOTS EASTWARD
INCLUDING CHEYENNE PROPER. THIS HIGH WIND EVENT WILL CONTINUE
THROUGHOUT THE AFTERNOON AND EVENING WITH FORECAST GUIDANCE AND
LOCAL MACHINE LEARNING SUPPORT IN EXCELLENT AGREEMENT ON HIGH
PROBABILITIES OF EXCEEDING 50 KNOTS. A PROGRESSIVE TROUGH WILL
RAPIDLY MOVE EASTWARD THROUGH THE NORTHERN ROCKIES OVERNIGHT TONIGHT
WITH A COLD FRONT DRAGGING SOUTHWARD THROUGH THE HIGH PLAINS TONIGHT
THROUGH TOMORROW MORNING. THIS FRONTAL BOUNDARY WILL AFFECT MOST
AREAS EAST OF I-25 IN SOUTHEAST WYOMING AS WELL AS THE NEBRASKA
PANHANDLE, DROPPING TEMPERATURES OVERNIGHT AND RESULTING IN A COOLER
DAY ON THURSDAY. THIS SURFACE FRONT WILL LIKELY STALL OUT SOMEWHERE
ALONG OR JUST NORTH OF CHEYENNE AND THE I-80 CORRIDOR AS MUCH OF THE
GENERAL MOMENTUM CONTINUES EASTWARD RATHER THAN SOUTHWARD. THUS,
OVERNIGHT LOWS TONIGHT AND HIGH TEMPERATURES ON THURSDAY WILL REMAIN
LARGELY UNAFFECTED BY THIS SYSTEM. IN FACT, AFTERNOON HIGHS MAY WARM
BY A DEGREE OR TWO IN CHEYENNE ON THURSDAY, RUNNING AROUND 15
DEGREES ABOVE AVERAGE FOR MID DECEMBER. EXPECT A GENERALLY CLEAR
OVERNIGHT ON THURSDAY NIGHT WITH TEMPERATURES NEAR TO SLIGHTLY ABOVE
AVERAGE. FORECAST CONFIDENCE IS EXTREMELY HIGH THROUGHOUT THE SHORT
TERM. MINOR UPWARD ADJUSTMENTS WERE DONE TO WIND AND TEMPERATURE
GRIDS TO IMPROVE ON MODEL BIASES.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED AT 232 PM MST WED DEC 18 2024
THE OVERALL WEATHER PATTERN DEPICTED BY THE MODELS
HAVE REMAINED CONSISTENT OVER THE PAST FEW MODEL RUNS LEADING TO
HIGH CONFIDENCE IN THE SYNOPTIC SETUP. A RIDGE WILL BEGIN TO PUSH
INTO OUR REGION KEEPING OUR DAYTIME TEMPERATURES ABOVE AVERAGE AND
OUR OVERNIGHT TEMPERATURES WILL BE EITHER SLIGHTLY ABOVE AVERAGE TO
AVERAGE DEPENDING ON HOW CLOUDY THE SKIES GET TO AFFECT RADIATIONAL
COOLING IN THE OVERNIGHT HOURS. LOOKING AT GFS OMEGA FIELDS THIS
WEEKEND, THERE IS A SIGNAL FOR A MOUNTAIN WAVE SETUP ON SUNDAY.
DEPENDING ON HOW STRONG (DEEP) THIS MOUNTAIN WAVE WILL BECOME WILL
CORRELATE TO HOW STRONG THE WINDS WILL BE ESPECIALLY IN OUR WIND
PRONE AREAS. THE UNCERTAINTY WITH THIS MOUNTAIN WAVE IS WITH THE
MAGNITUDE. BEING A FEW DAYS OUT THE MODELS CANNOT RESOLVE THE
COMPLETE DETAILS OF THE MOUNTAIN WAVE. WINDS LOOK TO MEET THE HIGH
WIND CRITERIA FOR THE WIND PRONE AREAS. SUB-WIND PRONE AREAS SUCH AS
CHEYENNE, LARAMIE VALLEY, AND EAST PLATTE COUNTY MAY ALSO REACH
CRITERIA BUT NOT QUITE CERTAIN FOR THOSE.
FOR THE HOLIDAYS, THERE IS A LOW PRESSURE SYSTEM THAT DIVES OUT OF
BRITISH COLUMBIA AND THE PACIFIC NORTHWEST THAT MAY GIVE US SOME
SNOW FOR THE CHRISTMAS TIME PERIOD. THE CURRENT PATH IS PROJECTED TO
SCATHE THE NORTHEAST PORTION OF WYOMING BUT IF THE SYSTEM DIVES
FURTHER SOUTH, THE SYSTEM COULD GIVE US SOME SNOW FOR THE HOLIDAYS.
BEING THE HOLIDAY SEASON WITH MANY TRAVELING THIS SYSTEM WILL BE
MONITORED CLOSELY TO SEE HOW THE MODELS FURTHER RESOLVE THE SYSTEM.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1029 AM MST WED DEC 18 2024
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. WINDS ARE
STILL EXPECTED TO GUST AS HIGH AS 50KTS STARTING IN THE LATE
AFTERNOON TO EARLY EVENING. AROUND 03Z LOW-LEVEL WIND SHEAR WILL
REALLY START TO RAMP UP BETWEEN 50 TO 60 KNOTS AT TIMES AT
AROUND 2,000 FT AGL. NOT EXPECTING TO HAVE ANY VISIBILITY OR
CLOUD ISSUES DURING THIS PERIOD.
CYS WATCHES/WARNINGS/ADVISORIES
WY...HIGH WIND WARNING UNTIL 5 AM MST THURSDAY FOR WYZ101-107-109-
115-118.
HIGH WIND WARNING UNTIL 5 AM MST THURSDAY FOR WYZ104-106-110-
116-117.
NE...NONE.
SHORT TERM...MAC
LONG TERM...MM
AVIATION...MM
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