805
FXUS65 KCYS 052340
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
440 PM MST WED MAR 5 2025
KEY MESSAGES
- A THREE-PART WINTER STORM WILL IMPACT THE AREA TONIGHT
THROUGH FRIDAY MORNING. VERY DIFFICULT TRAVEL CONDITIONS AND
NEAR BLIZZARD CONDITIONS ARE EXPECTED ALONG THE CORRIDOR FROM
MUDDY GAP TO CHADRON.
- PART 1: SNOW TONIGHT INTO THURSDAY MORNING TO AREAS ALONG
AND WEST OF THE LARAMIE RANGE, WITH LIGHT SNOW POSSIBLE FOR
THE HIGH PLAINS.
- PART 2: MODERATE TO HEAVY SNOWFALL AND INCREASING WINDS TO
THE US HIGHWAY 20 CORRIDOR IN ADDITION TO NORTHERN CARBON AND
ALBANY COUNTIES BEGINNING THURSDAY MORNING. THE I-80
CORRIDOR CAN EXPECT A LULL DURING THIS PHASE.
- PART 3: SNOW SHOWERS WILL FILL IN TO THE SOUTH THURSDAY
AFTERNOON AND EVENING, CONTINUING OVER MUCH OF THE HIGH
PLAINS INTO FRIDAY MORNING. UNCERTAINTY IN SNOW TOTALS IS
HIGHEST WITH THIS PHASE.
- A RETURN TO MILD AND DRY CONDITIONS IS EXPECTED TO START NEXT
WEEK ALONGSIDE THE RETURN OF WINDY CONDITIONS FOR MOST OF
SOUTHEAST WYOMING.
SHORT TERM /THROUGH FRIDAY/
ISSUED AT 406 PM MST WED MAR 5 2025
THE NEXT SNOW EVENT IS ON OUR DOORSTEP THIS AFTERNOON. CURRENT GOES
SATELLITE IMAGERY SHOWS DEEP MOISTURE OVERRUNNING MOST OF THE
SOUTHWEST CONUS AHEAD OF A STRONG PACIFIC TROUGH CURRENTLY MAKING
LANDFALL ALONG THE WEST COAST. WHILE WE HAVE ENJOYED SOME SUNSHINE
AND MILD TEMPERATURES TODAY, CLOUD COVER WILL BE ON THE INCREASE
THROUGH THE AFTERNOON AND EVENING HOURS. THE DEEP MOISTURE PLUME OUT
OF THE PACIFIC WILL BRING INTEGRATED WATER VAPOR TRANSPORT VALUES
ABOVE THE 99TH PERCENTILE OF CLIMATOLOGY INTO THE SOUTHERN TIER OF
THE FORECAST AREA. STRONG POSITIVE THETA-E ADVECTION AND MODEST
FRONTOGENESIS WILL MOVE IN FROM THE SOUTHWEST LATER THIS EVENING,
KICKING OFF SNOW FAIRLY QUICKLY ACROSS CARBON AND ALBANY COUNTIES.
THIS FIRST PHASE OF THE EVENT WILL BE OVERNIGHT INTO THURSDAY
MORNING AS THE STALLED FRONTAL BOUNDARY AND OVERRUNNING WARM MOIST
AIR ADVECTION SHIFTS NORTHWARD. BY MID MORNING THURSDAY, WE SHOULD
SEE THE FRONTAL BOUNDARY STRADDLING OUR NORTHERN ZONES, WHILE DRIER
AIR MOVES INTO THE SOUTHERN ZONES. THIS GIVES ENOUGH CONFIDENCE IN A
LONGER BREAK OR LULL IN SNOWFALL TO SPLIT UP WINTER WEATHER
HEADLINES. WINTER WEATHER ADVISORIES WERE ISSUED FOR THE I-80
CORRIDOR FROM RAWLINS TO THE SOUTHERN LARAMIE RANGE COVERING LATE
THIS EVENING THROUGH THURSDAY MORNING, WITH LIGHT TO MODERATE SNOW
ACCUMULATIONS ANTICIPATED.
DURING THE DAY THURSDAY, THE FRONTAL BOUNDARY WILL SHIFT NORTH OF
THE I-80 CORRIDOR AND STALL ROUGHLY POSITIONED FROM MUDDY GAP TO
CHADRON. THE COMBINATION OF STRONG OVERRUNNING ISENTROPIC LIFT, LOW
LEVEL UPSLOPE FLOW, AND LOW TO MID LEVEL FRONTOGENESIS WILL PRODUCE
MODERATE TO HEAVY SNOWFALL ALONG THIS AREA. AT THE SAME TIME, LEE
CYCLOGENESIS WILL OCCUR OVER EASTERN COLORADO, WITH MSLP MODELED TO
DROP TO AROUND 992-MB BY THE LATE AFTERNOON HOURS THURSDAY. THIS
WILL GRADUALLY INCREASE THE SURFACE PRESSURE GRADIENT THROUGH
THE DAY, AND THUS THE SURFACE WINDS. BY THE MID AFTERNOON HOURS,
WE MAY BE LOOKING AT EASTERLY WINDS GUSTING 30 TO 40 MPH ALONG
AND NORTH OF THE NORTH PLATTE RIVER VALLEY. THIS WILL CAUSE
SIGNIFICANT BLOWING AND DRIFTING SNOW AND NEAR BLIZZARD
CONDITIONS AT TIMES, PRIMARILY ALONG THE US HIGHWAY 20 CORRIDOR.
FURTHER SOUTH, FROM ROUGHLY RAWLINS TO SCOTTSBLUFF AND POINTS
SOUTH, FAIRLY MILD TEMPERATURES WILL SPILL WILL DURING THE DAY
THURSDAY WITH SOUTHWEST WINDS WEST OF THE LARAMIE RANGE, AND
SOUTHEAST WINDS TO THE EAST. THESE LOCATIONS MAY WARM UP INTO
THE UPPER 30S TO MID 40S, AND POSSIBLY EVEN A FEW LOW 50S IN THE
LOWER ELEVATIONS OF THE HIGH PLAINS. HOWEVER, THE MILD SURFACE
TEMPERATURES WILL THEN PRODUCE SOME MODEST CONVECTIVE
INSTABILITY BY THE AFTERNOON. ABUNDANT MOISTURE WILL STILL BE
MOVING UP FROM THE SOUTHWEST, WHICH WILL SET THE STAGE FOR SNOW
SHOWERS OF A CONVECTIVE NATURE TO RE-DEVELOP SOUTH OF THE
STALLED FRONTAL BOUNDARY THURSDAY AFTERNOON.
SNOW SHOWERS WILL INCREASE IN COVERAGE THROUGH THE AFTERNOON AND
EVENING HOURS, LEADING INTO THE THIRD PHASE OF THE EVENT. THIS IS
THE LOWEST CONFIDENCE PORTION OF THE SNOW EVENT AS THE SURFACE LOW
BEGINS TO EJECT EASTWARD, PULLING SOME WRAP AROUND MOISTURE BACK
INTO THE AREA. HOWEVER, THIS IS A VERY MESSY EXAMPLE. THE PARENT MID-
LEVEL LOW PRESSURE SYSTEM OVER SOUTHEAST IDAHO WILL BE SLOW TO
WEAKEN EVEN AS A NEW LOW DEVELOPS OVER EASTERN COLORADO. THIS MAKES
FOR A COMPLEX WIND AND LIFTING PROFILE OVER THE HIGH PLAINS THURSDAY
EVENING AND OVERNIGHT. STILL, MODEL GUIDANCE IS FAIRLY CONSISTENT IN
SHOWING LIGHT TO MODERATE SNOWFALL FILLING BACK IN ACROSS MOST OF
THE HIGH PLAINS OVERNIGHT INTO FRIDAY MORNING. THIS WILL BE THE MAIN
WINDOW FOR ACCUMULATING SNOW FOR AREAS SOUTHEAST OF A CHEYENNE TO
ALLIANCE LINE.
OVERALL CONFIDENCE IN THIS SYSTEM IS MEDIUM TO HIGH, AND
CONSIDERABLY HIGHER THAN THE LAST SYSTEM. A HIGH IMPACT EVENT IS ON
TRACK FOR NORTHERN CARBON/ALBANY COUNTIES, AND THE US-20 CORRIDOR
FROM GLENROCK TO CHADRON. THIS AREA CAN EXPECT A WIDESPREAD 6 TO 12"
OF SNOW, WITH LOCALLY HIGHER AMOUNTS IN THE HIGH ELEVATIONS AS
TYPICAL. THIS IS A HIGH CONFIDENCE WINTER STORM WARNING FOR THESE
AREAS. THE GUSTY WINDS WILL PRODUCE SIGNIFICANT BLOWING AND DRIFTING
SNOW, ALONG WITH NEAR BLIZZARD CONDITIONS AT TIMES. THE NEXT TIER OF
ZONES SOUTH OF THIS IS SLIGHTLY LOWER CONFIDENCE. IN PLATTE COUNTY,
THERE WAS NOT ENOUGH CONFIDENCE IN A BREAK OR LULL TO SPLIT OR DELAY
THE START OF THE HAZARD, BUT PERIODS OF MORE FAVORABLE TRAVEL
CONDITIONS MAY BE FOUND MID MORNING THROUGH MID AFTERNOON. THE LAST
AREA OF WINTER STORM WATCHES IN GOSHEN, SOUTHERN SIOUX, AND BOX
BUTTE COUNTIES WAS DELAYED UNTIL A 5PM THURSDAY START TIME. THE
INITIAL TWO PHASES OF THE STORM LOOK TO ONLY PRODUCE LIGHT SNOWFALL
IN THESE ZONES, WITH IMPACTS NOT EXPECTED TO BE WARNING LEVEL.
HOWEVER, THE FINAL PHASE STILL HAS THE POTENTIAL TO PRODUCE GREATER
IMPACTS HERE, AND THUS THE WATCH WAS CONTINUED. LASTLY, THE
REMAINING SOUTHERN ZONES OF THE HIGH PLAINS MAY NEED AN EXPANDED
HEADLINE FOR THURSDAY AFTERNOON THROUGH FRIDAY MORNING, BUT
CONFIDENCE IS TOO LOW AT THIS TIME, AND WE HAVE SOME TIME TO
CONTINUE TO EVALUATE.
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
ISSUED AT 406 PM MST WED MAR 5 2025
ENSEMBLE GUIDANCE REMAINS IN GOOD AGREEMENT ON THE LONG TERM AS
WE SEE CLEARING AND WARMING, IF ONLY STEADILY, AS HIGH PRESSURE
RIDGING OVERTAKES THROUGH THE WEEKEND, WITH THIS FEATURE THEN
SHIFTING EASTWARDS DURING THE EARLY TO MIDDLE PART OF NEXT WEEK
ALLOWING A MORE PROGRESSIVE PATTERN TO BEGIN DEVELOPING ON THE
TAIL END OF THE LONG TERM. TO BEGIN FRIDAY EVENING INTO
SATURDAY, A RIDGE WILL BEGIN OVERSPREADING FROM THE WEST COAST,
CONTINUING TO THEN MOVE ACROSS THROUGH THE REMAINDER OF THE
WEEKEND AND BECOMING OUR DOMINANT WEATHER FEATURE THROUGH THE
BEGINNING OF NEXT WEEK. A STEADY WARMING TREND WILL OCCUR UNDER
THIS RIDGE WITH TEMPERATURES EXPECTED TO RISE AROUND 5 TO 10
DEGREES EACH DAY BEGINNING SATURDAY AND CONTINUING THROUGH THE
WEEKEND, THOUGH LOCATIONS UNDER WINTER WEATHER PRODUCTS THIS
AFTERNOON MAY SEE A BIT OF A SLOWER INCREASE DUE TO THE EXPECTED
SNOWPACK ACROSS THE REGION. THE NBM SEEMS TO HAVE CAUGHT UP
WITH THIS AS TEMPERATURES ARE NOW SEVERAL DEGREES COOLER THAN
PREVIOUS MODEL RUNS, SO MINIMAL EDITS WERE NEEDED TO THESE. BY
MONDAY WE SHOULD SEE ENOUGH WARMING THOUGH TO PRODUCE A SWATH OF
50'S TO 60'S FOR HIGHS OUTSIDE OF OUR WESTERN MOUNTAINOUS
ZONES, WHERE HIGHS WILL LIKELY RANGE MORE IN THE 40'S TO 50'S
OUTSIDE OF THE PEAKS.
OUR FIRST WEATHER CONCERN COMES IN THE FORM OF GUSTY WINDS ON
SUNDAY AND PARTICULARLY INTO MONDAY. AS THE RIDGE BEGINS TO
FLATTEN THE JET WILL BE ABLE TO START CREEPING BACK INTO THE
REGION, WITH 700MB AROUND 40-50 KNOTS, MAXING OUT AT 55 KNOTS ON
MONDAY. THE STRONGEST OF THESE WINDS DON'T LOOK TO BE WIDESPREAD
ENOUGH ACROSS THE REGION AT THIS TIME THOUGH, AND IN HOUSE
GUIDANCE IS DOWN TO AROUND A 30-50% PROBABILITY OF HIGH WINDS
FOR OUR MOST PROBLEMATIC SPOTS INCLUDING BORDEAUX. IT WOULDN'T
BE SURPRISING TO SEE A HIGH WIND WARNING OR TWO, BUT CURRENTLY
NOT EXPECTING A WIDESPREAD HIGH WIND EVENT AT THIS TIME. FINALLY
AS THE RIDGE BEGINS TO SHIFT EASTWARDS AND AN UPPER TROUGH
BEGINS TO ENCROACH UPON THE REGION, WE'LL SEE A SHIFT BACK TO
MORE ACTIVE WEATHER ON TUESDAY AS TEMPERATURES COOL OFF BY A FEW
DEGREES WITH THE RETURN OF CLOUDS AND SOME COOLER AIR, WHILE
PRECIPITATION BEGINS TO POP BACK UP INTO OUR WESTERN ZONES WITH
SEVERAL INCHES OF SNOW POSSIBLE FOR THE DAY ACROSS THE SIERRA-
MADRE AND SNOWY RANGES. OVERALL THOUGH OUTSIDE OF SOME
OROGRAPHIC ENHANCEMENT ACROSS THE MOUNTAINS, QPF AMOUNTS DON'T
LOOK LARGELY IMPRESSIVE THANKS TO THIS BEING A WEAKER SYSTEM AND
A LACK OF FORCING, SO DON'T EXPECT THIS FIRST BATCH OF ACTIVITY
TO BE ANYTHING MORE THAN A MOUNTAIN SYSTEM AT BEST. BUT JUST
BEYOND THE LONG TERM AS THE WAVE TRAIN CONTINUES, WE COULD SEE A
MUCH STRONGER AND MORE IMPACTFUL SYSTEM TO END NEXT WEEK.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 425 PM MST WED MAR 5 2025
WEST FLOW ALOFT WILL PREVAIL TONIGHT, THEN WILL TURN SOUTHWEST
ON THURSDAY AS THE NEXT STORM SYSTEM AFFECTS THE REGION.
WYOMING TAFS...AT RAWLINS, CEILINGS WILL LOWER FROM 5000 FEET
THIS EVENING, TO LIGHT SNOW AND FOG REDUCING VISIBILITIES TO
1 MILE AND CEILINGS TO 1200 FEET FROM 06Z TO 15Z, THEN CEILINGS
WILL INCREASE TO 2500 FEET AFTER 15Z WITH LIGHT SNOW AND FOG
REDUCING VISIBILITIES TO 1 MILE. WINDS WILL GUST TO 25 KNOTS
AFTER 15Z THURSDAY.
FOR LARAMIE, CEILINGS NEAR 15000 FEET WILL LOWER TO 2500 FEET
WITH LIGHT SNOW REDUCING VISIBILITIES TO 4 MILES FROM 08Z TO
12Z, THEN CEILINGS WILL LOWER TO 1500 FEET FROM 12Z TO 15Z, THEN
INCREASE TO 5000 FEET AFTER 15Z THURSDAY. WINDS WILL GUST TO
25 KNOTS UNTIL 08Z.
FOR CHEYENNE, CEILINGS NEAR 15000 FEET WILL LOWER TO 5000 FEET
FROM 07Z TO 12Z, THEN TO 2000 FEET FROM 12Z TO 15Z, THEN
INCREASE TO 5000 FEET AFTER 15Z THURSDAY. WINDS WILL GUST TO
23 KNOTS UNTIL 02Z.
NEBRASKA TAFS...FOR CHADRON AND ALLIANCE, CEILINGS FROM 10000 TO
15000 FEET WILL LOWER TO 2500 FEET WITH LIGHT SNOW AND FOG REDUCING
VISIBILITIES TO 3 MILES FROM 12Z TO 18Z, THEN LIGHT SNOW AND FOG
WILL LOWER VISIBILITIES TO 1 MILE WITH CEILINGS NEAR 1500 FEET
AFTER 18Z THURSDAY. WINDS WILL GUST TO 20 KNOTS AT CHADRON UNTIL
07Z, AND TO 28 KNOTS AT BOTH TERMINALS AFTER 12Z THURSDAY.
FOR SCOTTSBLUFF AND SIDNEY, CEILINGS FROM 10000 TO 15000 FEET
WILL LOWER TO 2500 FEET WITH LIGHT SNOW AND FOG REDUCING
VISIBILITIES TO 3 MILES AT SIDNEY FROM 09Z TO 15Z, AND INCREASE
TO 5000 FEET AFTER 15Z THURSDAY, WHILE SCOTTSBLUFF WILL SEE
LIGHT SNOW AND FOG REDUCING VISIBILITIES TO 3 MILES AND CEILINGS
TO 1500 FEET AFTER 12Z THURSDAY. WINDS WILL GUST TO 23 KNOTS AT
SCOTTSBLUFF UNTIL 02Z, AND TO 25 KNOTS AT SIDNEY AFTER 15Z
THURSDAY.
CYS WATCHES/WARNINGS/ADVISORIES
WY...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY
MORNING FOR WYZ108.
WINTER STORM WARNING FROM 2 AM THURSDAY TO 5 AM MST FRIDAY FOR
WYZ101-102.
WINTER STORM WARNING FROM 2 AM THURSDAY TO 8 AM MST FRIDAY FOR
WYZ103-106-107.
WINTER STORM WARNING FROM 11 PM THIS EVENING TO 8 AM MST
FRIDAY FOR WYZ104-105.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 8 AM MST
THURSDAY FOR WYZ109-110.
WINTER STORM WARNING FROM 8 PM THIS EVENING TO 11 PM MST
FRIDAY FOR WYZ112.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 11 PM MST
FRIDAY FOR WYZ114.
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 8 AM MST
THURSDAY FOR WYZ115>117.
NE...WINTER STORM WARNING FROM 8 AM THURSDAY TO 11 AM MST FRIDAY
FOR NEZ002-095.
WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY
MORNING FOR NEZ003-096.
SHORT TERM...MN
LONG TERM...CG
AVIATION...RUBIN
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