Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 270504
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1004 PM MST THU FEB 26 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 318 PM MST THU FEB 26 2015

ONGOING UPSLOPE SNOW EVENT IS THE MAIN CONCERN INITIALLY.
VISIBILITIES HAVE BEEN THE LOWEST AND SNOWFALL RATES THE HIGHEST
AT CHEYENNE REALLY ALL DAY LONG. THIS AS LLVL EASTERLY UPSLOPE
FLOW INTERACTS WITH THE FAVORABLE LEADING EDGE OF SHORTWAVE ENERGY
DIVING SOUTHEAST INTO THE HIGH PLAINS/FRONT RANGE. 12/18Z MODELS
SHOW LLVL LIFT INCREASING ACROSS LARAMIE COUNTY THRU THE REST OF
THE EVENING HOURS. MODELS HAVE CONTINUED TO TREND SNOWFALL AMOUNTS
UP ACROSS CENTRAL/SOUTHERN LARAMIE COUNTY ESPECIALLY FOR THIS
EVENING. SO IN AN EARLIER UPDATE...OPTED TO ISSUE A WINTER WEATHER
ADVISORY FOR CENTRAL LARAMIE COUNTY INCLUDING WRN FOOTHILLS
LOCATIONS EFFECTIVE THRU 10Z FRIDAY. EXPECT GENERALLY 2 TO 4
INCHES TO FALL...WITH THE HIGHEST AMOUNTS IN AREAS NEAREST THE
CHEYENNE RIDGE. LIFT/SNOW WILL DIMINISH SIGNIFICANTLY WITH THE
PASSAGE OF THE MID-LEVEL/H5 TROUGH FRIDAY 09-12Z. AMOUNTS WILL BE
SIGNIFICANTLY LIGHTER OUTSIDE OF LARAMIE COUNTY WITH THIS
SYSTEM...WITH PERHAPS AN INCH OR SO AT LARAMIE... WHEATLAND AND
KIMBALL. RAWLINS AND LOCATIONS TO THE NORTH OF THE NORTH PLATTE
RIVER VALLEY WILL SEE NOTHING AT ALL OR JUST SOME FLURRIES.
FORTUNATELY WINDS ARE ONLY PROGD TO BE AROUND 10 KNOTS...SO DONT
EXPECT BLOWING SNOW TO BE A CONCERN. ANOTHER COLD NIGHT AHEAD WITH
LOWS FALLING INTO THE SINGLE DIGITS OR SINGLE DIGITS BELOW ZERO.

QUICK SHORTWAVE RIDGE AXIS WILL USHER IN A MOSTLY DRY DAY FOR
FRIDAY WITH PERHAPS A FEW DEGREES OF WARMING BENEATH A VERY BRIEF
LLVL THERMAL RIDGING. EVEN SO HIGHS ON FRIDAY WILL ONLY REACH THE
TEENS AND 20S.

THE NEXT COLD FRONT WILL SLIDE FROM NORTH TO SOUTH DURING THE DAY
ON SATURDAY AS THE PATTERN FLATTENS AHEAD OF THE FORMING CUT-OFF
OVR THE GREAT BASIN. MOISTURE WILL BE LIMITED INITIALLY ON
SATURDAY AWAITING THE ARRIVAL OF AN EJECTING SHORTWAVE ENERGY AND
RESULTANT FAVORABLE ISENTROPIC LIFT/OVERRUNNING SET-UP. SNOW WILL
OVERSPREAD MUCH OF THE SOUTHERN TIER OF COUNTIES LATE SATURDAY AND
ESPECIALLY SATURDAY NIGHT. ALTHOUGH EXPECT THE BULK OF THE BEST
LIFT TO REMAIN SOUTH OVER COLORADO...SHOULD SEE SOME AT LEAST
LIGHT ACCUMULATIONS ESPECIALLY ALONG THE I80 CORRIDOR.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 318 PM MST THU FEB 26 2015

A RATHER COLD PATTERN EXPECTED TO PERSIST OVER THE REGION FOR MOST
OF THIS PERIOD WITH MONDAY LIKELY BEING THE MILDEST DAY THIS
PERIOD. INITIALLY THE CWA WILL BE UNDER CONFLUENT UPPER FLOW
BETWEEN ONE STREAM EMANATING FROM WESTERN CANADA INTO THE
NORTHERN PLAINS AND THE OTHER FROM THE SOUTHWEST CONUS AHEAD OF AN
UPPER LOW OFF THE CAL COAST. STILL CHILLY ACROSS THE AREA SUNDAY
AS A COLD SFC HIGH OVER THE HIGH PLAINS SHIFTS EAST DURING THE
DAY. A SHORTWAVE WILL MOVE INTO THE PACIFIC NW ON MONDAY AND PHASE
WITH THE CALIFORNIA UPPER LOW CREATING A LARGER SCALE UPPER TROF
OVER THE WESTERN CONUS MONDAY NIGHT. AT THE SAME TIME LEE TROFFING
WILL DEVELOP OVER THE HIGH PLAINS WHICH WILL SCOUR OUT THE COLDER
AIR AND BRING A SHORT PERIOD OF WARMING TO THE CWA FOR MONDAY.
MOISTURE FROM THE SOUTHWEST SHOULD GET CAUGHT UP IN THE SWLY FLOW
AHEAD OF THE UPPER TROF AND ADVECT OVER THE CWA MONDAY NIGHT AND
TUESDAY. THE NEXT SURGE OF COLD AIR WILL THEN DROP SOUTH OVER THE
HIGH PLAINS EARLY TUESDAY AND WILL AID IN THE DEVELOPMENT OF SNOW
OVER THE REGION TUESDAY INTO TUESDAY NIGHT. QUITE COLD AGAIN WEDS
WITH SNOW ENDING EARLY AS THE SURFACE HIGH SETTLES ACROSS WY AND
THE MAIN UPPER TROF AXIS PASSES ACROSS LEAVING A NW FLOW ALOFT
OVER THE REGION. MAINLY DRY THURSDAY WITH WARMER TEMPS AGAIN AS
DOWNSLOPE FLOW RETURNS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1001 PM MST THU FEB 26 2015

PROBLEM AREAS LOOK TO BE KCYS AND OUR SOUTHERN NEBRASKA AIRPORTS
OVER THE NEXT 12 HOURS OR SO WITH SOUTHEAST UPSLOPING WIND. WORST
AREA WILL BE KCYS WHICH IS CURRENTLY IFR IN SNOW. SNOW EXPECTED TO
CONTINUE ANOTHER COUPLE HOURS...THEN AFTER IT STOPS...DO BELIEVE
LOWERING CEILINGS WILL MOVE IN. COULD PERSIST MOST OF THE DAY
FRIDAY WITH SOUTH TO SOUTHEAST UPSLOPE WINDS CONTINUING. PRETTY
FAVORABLE WINDS FOR UPSLOPE AT KBFF...KAIA AND POSSIBLY KSNY AS
WELL.

&&

.FIRE WEATHER...
ISSUED AT 318 PM MST THU FEB 26 2015

COLD TEMPERATURES AND UNSETTLED CONDITIONS WILL SUPPRESS ANY FIRE
WEATHER CONCERNS FOR THE FORESEEABLE FUTURE.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER WEATHER ADVISORY UNTIL 3 AM MST FRIDAY FOR WYZ117-118.

NE...NONE.
&&

$$

SHORT TERM...CAH
LONG TERM...RE
AVIATION...GCC
FIRE WEATHER...CAH


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