428
FXUS65 KCYS 191740
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1040 AM MST THU DEC 19 2024
KEY MESSAGES
- TODAY WILL CONTINUE TO BE WINDY, THOUGH NOT AS WINDY AS IT WAS YESTERDAY.
MAXIMUM TEMPERATURES TODAY WILL BE COOLER THAN YESTERDAY FOR
MOST LOCATIONS EAST OF I-25 AS A COLD FRONT MOVES ACROSS THE
AREA.
- DRY AND RELATIVELY MILD WEATHER WILL DEVELOP FOR FRIDAY
THROUGH THE WEEKEND, WITH ANOTHER POSSIBLE HIGH WIND EVENT
OCCURRING FOR SUNDAY AND SUNDAY NIGHT.
- SOMEWHAT COOLER TEMPERATURES WILL DEVELOP FOR EARLY NEXT
WEEK, WITH SNOW POSSIBLE FOR THE SNOWY AND SIERRA MADRE RANGES
ON MONDAY AND FOR THE MOUNTAINS AND NEARBY LOWER ELEVATIONS
FOR CHRISTMAS DAY.
SHORT TERM /THROUGH FRIDAY NIGHT/
ISSUED AT 245 AM MST THU DEC 19 2024
TODAY...LOW AND MID LEVEL GRADIENTS CONTINUE TO SLOWLY WEAKEN
OVERNIGHT, WITH CRAIG-CASPER 850/700 HEIGHT DIFFERENCES DROPPING
FROM 70/66 METERS AT 06Z TO 65/61 METERS AT 12Z. WINDS CONTINUE TO
SLOWLY WEAKEN, ALTHOUGH SEVERAL SITES SUCH AS RAWLINS, ARLINGTON AND
CENTENNIAL CONTINUE TO HAVE WINDS NEAR OR SLIGHTLY EXCEEDING HIGH
WIND CRITERIA. THUS, WE WILL CONTINUE THE HIGH WIND WARNING AND
REEVALUATE IN THE NEXT FEW HOURS IF EXTENSION BEYOND 5 AM WILL BE
NECESSARY. INITIAL GUIDANCE SUGGESTS THE HIGH WIND WARNING WILL
LIKELY END AT OR BEFORE 5 AM AS GRADIENTS CONTINUE TO WEAKEN.
A FAST MOVING SHORTWAVE TROUGH ALOFT MOVES SOUTHEAST ACROSS THE
CENTRAL PLAINS STATES TODAY, SENDING ITS ASSOCIATED COLD FRONT INTO
OUR NORTHERN AND EASTERN COUNTIES AND PRODUCING A COLDER DAY TODAY
COMPARED TO YESTERDAY. LOW LEVEL GRADIENTS WILL STILL BE SUFFICIENT
TO PRODUCE ANOTHER WINDY DAY, ESPECIALLY FOR THE NEBRASKA PANHANDLE.
700 MB TEMPERATURES NEAR -7 CELSIUS WILL YIELD MAXIMUM TEMPERATURES
ONLY IN THE 40S TO NEAR 50 DEGREES.
TONIGHT...NORTHWEST FLOW ALOFT CONTINUES, AND WITH WEAKENING
GRADIENTS AND WINDS, A COLDER NIGHT IS EXPECTED COMPARED TO THIS
MORNING.
FRIDAY...ANOTHER WARMING TREND IS EXPECTED WITH 700 MB TEMPERATURES
REBOUNDING TO NEAR 4 CELSIUS, AND A SURFACE LEE TROUGH DEVELOPMENT,
PRODUCING DOWNSLOPE WINDS, AND HELPING MAXIMUM TEMPERATURES TO CLIMB
TO THE UPPER 40S TO MID 50S. IT WILL ALSO FEEL PARTICULARLY WARMER
DUE TO WEAKER LOW LEVEL GRADIENTS AND LESS WIND.
FRIDAY NIGHT...RIDGING ALOFT MOVES OVER CENTRAL WYOMING AND WITH A
MODERATING AIRMASS, MINIMUM TEMPERATURES WILL BE NOT AS COLD AS
THURSDAY NIGHT. CONTINUED DRY WITH THE LACK OF LOW AND MID LEVEL
MOISTURE.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
ISSUED AT 245 AM MST THU DEC 19 2024
MEDIUM TO LONG RANGE MODELS REMAIN IN GOOD AGREEMENT THIS
WEEKEND THROUGH TUESDAY NIGHT WITH RELATIVELY SMALL ENSEMBLE
SPREADS MOST DAYS. MODELS SHOW AN UPPER LEVEL RIDGE AXIS
PUSHING INTO THE INTERMOUNTAIN WEST AND THE FRONT RANGE THIS
WEEKEND, RESULTING IN TEMPERATURES WELL ABOVE NORMAL FOR THIS
TIME OF THE YEAR. THE WEATHER WILL REMAIN DRY FRIDAY THROUGH
MOST OF SUNDAY, BUT WINDY CONDITIONS AND THE POTENTIAL FOR
STRONG WINDS ARE EXPECTED SUNDAY THROUGH EARLY MONDAY. MODELS
SHOW A POTENT AND FAST MOVING PACIFIC SHORTWAVE EJECTING
EASTWARD ACROSS IDAHO AND NORTHERN WYOMING SUNDAY. THE 00Z GFS
HAS TRENDED 700MB WINDS HIGHER WITH SPEEDS OVER 70 KNOTS ACROSS
FAR SOUTHEAST WYOMING. THE OTHER MODELS ARE LOWER, BUT STILL
ENOUGH FOR HIGH WIND CRITERIA AS A 100 KT JET MAX SLIDES ACROSS
THE REGION. STRONG LOW LEVEL SUBSIDENCE IS SIMILAR TO THE LAST
FEW HIGH WIND EVENTS ACROSS SOUTHEAST WYOMING, WHICH PEAKS
BETWEEN 12Z AND 18Z SUNDAY (SUNDAY MORNING). KEPT STRONG WINDS
IN THE FORECAST WITH VERY WINDY CONDITIONS OUTSIDE OF THE WIND
PRONE AREAS. THIS IS ANOTHER EVENT WHERE LARAMIE, CHEYENNE,
RAWLINS, AND DOUGLAS/WHEATLAND MAY SEE GUSTS OVER 60 MPH.
OTHERWISE, IT WILL REMAIN MILD THIS WEEKEND WITH HIGHS IN THE
50S TO AROUND 60 ALONG AND EAST OF I-25, WITH HIGHS IN THE 40S
TO NEAR 50 FOR THE HIGH VALLEYS WEST OF THE LARAMIE RANGE.
FOR MOST OF NEXT WEEK, INCLUDING CHRISTMAS DAY, A SLIGHT
PATTERN SHIFT IS EXPECTED BEHIND SUNDAY'S FAST MOVING PACIFIC
SHORTWAVE. MID TO UPPER LEVEL FLOW IS FORECAST TO SHIFT INTO THE
NORTHWEST WHICH SHOULD ALLOW FOR ADDITIONAL SHORTWAVE
DISTURBANCES TO DIG SOUTH OUT OF WESTERN CANADA. OVERALL,
TEMPERATURES WILL TREND COOLER EACH DAY...BUT SHOULD REMAIN
ABOVE AVERAGE FOR THIS TIME OF THE YEAR. MOUNTAIN SNOWFALL IS
FORECAST TO INCREASE ON MONDAY WELL AHEAD OF THE NEXT PACIFIC
SYSTEM. WILL HAVE TO WATCH THIS NEXT PACIFIC STORM SYSTEM, WHICH
MODELS SHOW PUSHING ONSHORE EARLY TUESDAY MORNING AND THEN
THROUGH THE GREAT BASIN REGION TUESDAY NIGHT. ALL MODELS IN
ABOUT A HALF OF ENSEMBLE MEMBERS SHOW INCREASING CHANCES FOR
SNOW CHRISTMAS DAY, ESPECIALLY FURTHER SOUTH ALONG THE I-80
CORRIDOR AND THE MOUNTAINS. LEE SIDE CYCLOGENESIS IS POSSIBLE
IN THIS PATTERN, BUT MOISTURE ADVECTION LOOKS MINIMAL SINCE THE
STORM SYSTEM MOVES QUICKLY ACROSS THE FRONT RANGE. INCREASED
POP ACROSS THE AREA LATE TUESDAY AND INTO CHRISTMAS DAY WITH
TEMPERATURES LOWERING CLOSER TO NORMAL. MODELS THEN SHOW A
STRONG PACIFIC JET STREAM MOVING ONSHORE AND MOVING VERY LITTLE
AFTER CHRISTMAS DAY, WHICH IS A VERY GOOD SET UP FOR SOME MUCH
NEEDED MOUNTAIN SNOWFALL.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1021 AM MST THU DEC 19 2024
VFR CONDITIONS WILL PREVAIL AT ALL TERMINALS TOAY. EXPECT GUSTY
NORTH-NORTHWEST WINDS TODAY AT ALL TERMINALS HOWEVER WINDS WILL
DIE DOWN AFTER SUNSET. CLEAR SKIES AND TRANQUIL WEATHER
EXPECTED OVERNIGHT WITH VFR ONCE AGAIN ON FRIDAY MORNING AT ALL
SITES.
CYS WATCHES/WARNINGS/ADVISORIES
WY...NONE.
NE...NONE.
SHORT TERM...RUBIN
LONG TERM...TJT
AVIATION...MAC
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