Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 171017
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
417 AM MDT FRI APR 17 2015

.SHORT TERM...(TODAY THROUGH SATURDAY NIGHT)
ISSUED AT 415 AM MDT FRI APR 17 2015

CLOSED LOW OVR THE FOUR CORNERS IS FINALLY BEGINNING TO EVER SO
SLOWLY WOBBLE TO THE NORTHEAST TOWARDS COLORADO THIS MORNING. IT
WILL BE SLOW IN DOING SO...ONLY REACHING BETWEEN SALIDA/COLORADO
SPRINGS BY MIDNIGHT TONIGHT. THE WCB HAS BEEN EFFICIENT IN
ADVECTING MOISTURE THUS FAR...THOUGH PRECIP/SNOW RATES HAVE BEEN
TEMPERED SOMEWHAT BY DRY SLOT EXTENDING AND LIFTING NORTH ALONG
THE FRONT RANGE. MAIN FORECAST CHALLENGE CONTINUES TO BE THE
TIMING AND INTENSITY OF ADDL SNOW BANDS...IN ADDITION TO JUST HOW
MUCH THE AREA CAN WARM TODAY. OVERNIGHT TEMPS HAVE HOVERED AROUND
FREEZING BETWEEN 6-7 KFT WHICH HAS MITIGATED THE IMPACTS OF
FALLING SNOW ON AREA ROADWAYS AT LEAST IN THE CHEYENNE AREA...WITH
SOME MELTING OCCURRING UPON IMPACT. THIS CHANGES ABOVE 7 KFT WHERE
TEMPS HAVE BEEN IN THE UPPER 20S. MODELS HAVE BEEN DOING A FAIR
JOB OVERNIGHT...BUT CONTINUE TO BE MUCH TOO WARM WITH TEMPERATURE
PROGS. MODELS CONTINUE TO PROG THE NEXT VORT LOBE AND POCKET OF
ISENTROPIC LIFT TO ROTATE NORTH INTO THE AREA THIS MORNING. THIS
ALONG WITH THE PERSISTENT LLVL UPSLOPE WILL BE RESPONSIBLE FOR
BRINGING ADDL SNOWFALL TO THE AREA. THE ONE FLY IN THE OINTMENT IS
THE POTENTIAL IMPACT THAT THE DRY SLOT MAY HAVE THIS MORNING.
THIS ALONG WITH THUNDERSTORM COMPLEX OVR THE SRN PLAINS MAY ROB
SOME OF THE AVAILABLE MOISTURE. AT ANY RATE...CONFIDENCE REMAINS
HIGH THAT ADDL SNOW ACCUMULATIONS WILL OCCUR TODAY. SIMILAR TO
YESTERDAY...TEMPERATURES AND ALBEIT WEAK DAYTIME INSOLATION ARE
EXPECTED TO MITIGATE SOME OF THE IMPACTS AT LEAST IN THE VICINITY
OF CHEYENNE. THIS WILL BE DIFFERENT OVR THE HIER ELEVATIONS OVR
THE SUMMIT HOWEVER WHERE COLDER TEMPS WILL PERSIST. AS FOR
HEADLINES...HAVE OPTED TO EXTEND CENTRAL LARAMIE COUNTY UNTIL 3 PM
AND THE LARAMIE RANGE...LARAMIE VALLEY AND SNOWY RANGE UNTIL
MIDNIGHT TONIGHT. SNOW WILL FALL TONIGHT AS WELL...THOUGH RATES
SHOULD BE MUCH LESS. HIGHS TODAY WILL REACH THE MID/UPPER 30S AT
CHEYENNE AND LARAMIE WITH 40S AND 50S ELSEWHERE.

THE UPPER LOW WILL REACH THE CENTRAL PLAINS LATE SATURDAY...
ALTHOUGH MOISTURE CYCLING AROUND ITS PERIPHERY WILL CONTINUE TO
PRODUCE PRECIPITATION CHANCES. FORTUNATELY...TEMPERATURES WILL BE
WARMER ON SATURDAY LIMITING SNOW CHANCES TO ONLY THE HIGHEST
ELEVATIONS. HIGHS WILL RETURN TO THE 40S AND 50S EVERYWHERE FOR
SATURDAY.

MODELS PROG WEAK INSTABILITY OVR THE WRN NEBRASKA PANHANDLE TODAY
AND SATURDAY AFTERNOON. SO HAVE ADDED THUNDER MENTION TO THESE
AREAS AS A RESULT.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 415 AM MDT FRI APR 17 2015

SUNDAY...CONTINUED COOL WITH NORTH NORTHWEST FLOW ALOFT
RETARDING HEATING...AND WINDY WITH DEEP UNIDIRECTIONAL NORTH
NORTHWEST WINDS AT LOW AND MID LEVELS AND PROGGED GRADIENTS. MAY BE
SOME OROGRAPHIC TYPE SNOWS PRIMARILY ALONG AND WEST OF INTERSTATE
25...OVER AND NEAR OUR SNOWY...SIERRA MADRE AND LARAMIE RANGES.

MONDAY...ISOLATED SNOW SHOWERS OVER OUR SNOWY AND SIERRA MADRE
RANGES IN NORTH NORTHWEST FLOW ALOFT...OTHERWISE DRY. SLOW WARMING
TREND TEMPERED BY NORTH NORTHWEST FLOW ALOFT.

TUESDAY...WARMING TREND BEGINS IN EARNEST AS THE FLOW ALOFT BACKS TO
NORTHWEST...HEIGHTS ALOFT RISE WITH THE APPROACH OF THE RIDGE ALOFT
OVER THE GREAT BASIN STATES.

WEDNESDAY...CONTINUED MILD AS THE RIDGE ALOFT MOVES OVERHEAD THOUGH
TEMPERATURES STILL LIMITED SOMEWHAT BY LOW LEVEL WINDS REMAINING
FROM AN UPSLOPE COMPONENT EAST OF THE LARAMIE RANGE.

THURSDAY...SLIGHTLY COOLER WITH MORE CLOUD COVER. BOTH THE 17/00Z
GFS AND ECMWF SHOW WIDESPREAD PRECIPITATION AND QPF OVER OUR
COUNTIES...WHICH IS QUITE LIKELY OVERDONE BASED ON THE SYNOPTIC
PATTERN...SO WILL BLEND WITH OUR NEIGHBORS AND KEEP LOW END POPS
GOING.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 415 AM MDT FRI APR 17 2015

MOUNTAINS OBSCURED. IN SNOW...RAIN AND FOG...WIDESPREAD
IFR AND OCCASIONAL MVFR AT RAWLINS...LARAMIE...CHEYENNE AND
SIDNEY...WITH VFR AND MVFR PREVAILING AT CHADRON...ALLIANCE AND
SCOTTSBLUFF.

&&

.FIRE WEATHER...
ISSUED AT 415 AM MDT FRI APR 17 2015

WIDESPREAD MOISTURE AND COOLER TEMPERATURES WILL KEEP FIRE WEATHER
CONCERNS AT BAY FOR THE FORESEEABLE FUTURE.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WINTER STORM WARNING UNTIL MIDNIGHT MDT TONIGHT FOR WYZ114>117.

     WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR WYZ103-
     105-106-110-112.

     WINTER STORM WARNING UNTIL 3 PM MDT THIS AFTERNOON FOR WYZ118.

NE...NONE.

&&

$$

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



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