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000
FXUS65 KCYS 051220
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
520 AM MST WED MAR 5 2014

.SHORT TERM...(TODAY THROUGH FRIDAY)

ISSUED AT 348 AM MST WED MAR 5 2014

CURRENT KCYS RADAR LOOP ONLY SHOWS A FEW SNOW SHOWERS PUSHING
ALONG I25 NEAR THE LARAMIE RANGE TONIGHT AS THE MAIN UPPER LEVEL
DISTURBANCE QUICKLY MOVES SOUTHEAST OF THE FORECAST AREA. THESE
SNOW SHOWERS SHOULD DISSIPATE AROUND SUNRISE. THE MAIN BAND OF
SNOW MISSED THE I80 CORRIDOR BY ABOUT 30 TO 50 MILES YESTERDAY
RESULTING IN ONLY A PERIOD OF RAIN AND SNOW LATE IN THE EVENING
AND SNOW ACCUMULATIONS BELOW ONE INCH NEAR THE COLORADO BORDER.
MOSTLY SUNNY SKIES ARE EXPECTED TODAY WITH TEMPERATURE NEAR OR
SLIGHTLY ABOVE NORMAL...RANGING FROM THE MID 40S TO LOW 50S. ADDED
PATCHY FOG TO THE FORECAST ACROSS THE NORTHERN HALF OF THE
NEBRASKA PANHANDLE THIS MORNING WITH ALLIANCE AND CHADRON
OBSERVING ONE QUARTER MILE VISIBILITY.

STRONG WINDS WILL BECOME THE PRIMARY CONCERN TONIGHT AS A LEE SIDE
SURFACE LOW DEVELOPS ACROSS CENTRAL MONTANA AND MOVES SOUTHEAST
ACROSS THE NORTHERN HIGH PLAINS. MEANWHILE...700MB WINDS WILL
INCREASE BETWEEN 55 TO 60 KNOTS AS A LLVL AREA OF HIGH PRESSURE
REMAINS TO THE WEST OF THE CONTINENTAL DIVIDE. THE COMBINATION OF
A STRENGTHENING SURFACE PRESSURE GRADIENT AND STRONG WINDS ALOFT
MAY RESULT IN STRONG GUSTY WINDS MAINLY ACROSS THE WIND PRONE
AREAS OF SOUTHEAST WYOMING. ISSUED A HIGH WIND WATCH FOR THE
ARLINGTON AREA...SW PLATTE COUNTY BETWEEN WHEATLAND AND
CHUGWATER...AND THE I80 SUMMIT INCLUDING THE EASTERN FOOTHILLS.
MORE CONFIDENT THAT THE ARLINGTON AND BORDEAUX AREAS WILL HIT
CRITERIA COMPARED TO THE I80 SUMMIT...WHICH SEEMS MARGINAL AT
BEST. HOWEVER...HAVE JUST ENOUGH CONFIDENCE TO MENTION THIS
LOCATION IN THE WATCH MAINLY BECAUSE OF UNDER ESTIMATION OF RECENT
EVENTS. GUSTS UP TO 65 MPH ARE POSSIBLE THROUGH THURSDAY MORNING.
GUSTY WINDS WILL SPREAD ACROSS THE VALLEYS AND HIGH PLAINS OF
SOUTHEAST WYOMING THURSDAY AFTERNOON...BUT GUSTS SHOULD REMAIN
BELOW 50 MPH DUE TO LLVL BOUNDARY LAYER MIXING. HIGH TEMPERATURES
WILL REBOUND INTO 50S TO MID 60S THURSDAY AFTERNOON.

THESE MILD TEMPERATURES WILL BE VERY BRIEF AS ANOTHER PACIFIC
STORM SYSTEM WILL QUICKLY MOVE EASTWARD FROM THE EASTERN PACIFIC
OCEAN. MODELS INDICATE ANOTHER UPPER LEVEL SHORTWAVE QUICKLY
MOVING ACROSS THE GREAT BASIN REGION BY THURSDAY EVENING WITH
RAIN/SNOW DEVELOPING AFTER SUNSET...ESPECIALLY WEST OF THE LARAMIE
RANGE. GFS AND ECMWF ARE IN GOOD AGREEMENT...SHOWING MODERATE QPF
AMOUNTS ALONG AND SOUTH OF I80 AND IN THE MOUNTAINS. PRECIPITATION
APPEARS TO BE IN THE FORM OF SNOW...SO WILL HAVE TO WATCH THE
TRACK OF THIS FEATURE FOR POSSIBLE WINTER WEATHER HEADLINES. THE
ECMWF HAS BEEN THE MOST CONSISTENT MODEL...WITH THE GEM AND NAM
RECENTLY BACKING OFF ON STRONG DYNAMIC LIFT. INCREASED POP
BETWEEN 50 TO 80 PERCENT NEAR THE COLORADO BORDER...BUT KEPT
FORECAST QPF LOW FOR NOW. THERE IS LOW TO MIDLEVEL UPSLOPE FLOW
PRESENT WITH GOOD INSTABILITY...BUT NOT TOO IMPRESSED WITH THE
LLVL DYNAMIC FORCING OUTSIDE OF THE UPSLOPE COMPONENT. TO ADD MORE
UNCERTAINTY...THE NAM SHOWS THE MOST SNOWFALL WITH THIS SYSTEM
DURING FRIDAY NIGHT IN CONTRAST WITH THE GFS AND ECMWF WHICH SHOWS
MOST OF THE HEAVY PRECIP DURING THE DAY ON FRIDAY.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY NIGHT)

ISSUED AT 348 AM MST WED MAR 5 2014

AN UPPER LEVEL TROUGH WILL CONTINUE TO DIG SOUTH OF THE FORECAST
AREA FRIDAY NIGHT WITH A FEW SHOWERS COMING OFF THE MOUNTAINS AND
ACROSS THE ADJACENT PLAINS. PRECIP WILL END THROUGH SATURDAY MORNING
AS MUCH DRIER AIR MOVES IN FROM THE NORTH AND WIDESPREAD SUBSIDENCE
OVERSPREADS THE FORECAST AREA ON THE BACKSIDE OF THE DEPARTING TROUGH.
TEMPS WILL WARM A FEW DEGREES FOR SATURDAY UNDER CLEARING SKIES AND
AS HEIGHTS BEGIN TO REBUILD FROM THE NORTHWEST WITH AN APPROACHING
UPPER LEVEL RIDGE. THE ASSOCIATED THERMAL RIDGE AXIS WILL MOVE
OVERHEAD ON SUNDAY...WITH SFC TEMPS WARMING A GOOD 10+ DEGREES
ACROSS THE BOARD. WESTERLY DOWNSLOPE SFC WINDS WILL ADD A FEW
DEGREES TO THE THERMOMETER AS WELL ACROSS THE EASTERN PLAINS.
SHORTWAVE ENERGY MOVING ATOP THE RIDGE WILL WORK TO FLATTEN THE
RIDGE SOMEWHAT ON MONDAY AND FURTHERMORE ON TUESDAY...WITH A SERIES
OF SFC COLD FRONTS MOVING SOUTH ACROSS THE CWA THROUGH THIS TIME.
WILL SEE CONTINUED MILD AND BREEZY WESTERLY WINDS ON MONDAY...WITH A
QUICK SHOT FOR RAIN CHANGING TO SNOW AS THE FIRST FRONT MOVES SOUTH
THROUGH THE AREA IN THE AFTERNOON/EVENING. MODELS DO SHOW SOMEWHAT
DIFFERENT SOLUTIONS WITH A STRONGER STORM SYSTEM MOVING EASTWARD OFF
THE PACIFIC MONDAY NIGHT AND TUESDAY. THE ECMWF IS ALREADY IN THE
DESERT SOUTHWEST WITH THIS FEATURE BY TUESDAY MORNING WHILE THE GFS
HANGS IT BACK IN THE PAC NW AT THIS TIME. WILL MAINTAIN SLIGHT
CHANCE TO CHANCE POPS ACROSS THE CWA FOR MONDAY AND TUESDAY TO
ACCOUNT FOR SYNOPTIC DIFFERENCES BETWEEN MODELS...BUT COULD BE
ANOTHER WIDESPREAD LIGHT TO MODERATE SNOW EVENT AS THE TROUGH AXIS
MOVES OVERHEAD EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 520 AM MST WED MAR 5 2014

MVFR/IFR CIGS WILL CONTINUE TO BE A CONCERN THROUGH MID MORNING
MAINLY AT THE NEBRASKA TERMINALS. THESE CONDITIONS WILL RETURN TO
VFR AS A DRIER AIR MASS TAKES OVER AND DAYTIME HEATING ENSUES
LATER IN THE MORNING. SOUTHWEST WIND GUSTS OF 25 TO 30 KNOTS CAN
BE EXPECTED AT SE WYOMING TERMINALS THIS AFTERNOON...WITH WINDS
INCREASING AT THE NEBRASKA TERMINALS THIS EVENING.

&&

.FIRE WEATHER...
ISSUED AT 348 AM MST WED MAR 5 2014

MINIMAL FIRE WEATHER CONCERNS LATE THIS WEEK AND THROUGH THIS
WEEKEND. DRY CONDITIONS WILL PREVAIL WEDNESDAY AND
THURSDAY...WITH THE POSSIBILITY OF ACCUMULATING SNOW RETURNING TO
THE AREA ON FRIDAY AND SATURDAY. THE WARMEST DAYS WILL BE THURSDAY
AND SUNDAY...WITH RELATIVE HUMIDITIES BOTTOMING OUT AROUND 25 TO 35
PERCENT DURING THE AFTERNOON.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WATCH FROM LATE TONIGHT THROUGH THURSDAY MORNING FOR
     WYZ106-110-116-117.

NE...NONE.
&&

$$

SHORT TERM...TJT
LONG TERM...RJM
AVIATION...RJM
FIRE WEATHER...TJT