052  
FXUS65 KCYS 212245  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
345 PM MST FRI NOV 21 2014  
   
SHORT TERM
 
(THIS EVENING THROUGH SATURDAY)  
ISSUED AT 345 PM MST FRI NOV 21 2014  
 
QUIET WEATHER IS QUICKLY COMING TO AN END AS WE TRANSITION INTO A  
VERY ACTIVE PATTERN FOR THE SHORT TERM PERIOD. HIGHLIGHTS REVOLVE  
AROUND POTENTIAL FOR VERY STRONG WINDS OVER SOUTHEAST WYOMING AND  
POSSIBLY WESTERN NEBRASKA...AND MOUNTAIN SNOWS. LATEST WATER VAPOR  
SATELLITE LOOP SHOWS A VIGOROUS UPPER-LEVEL SHORTWAVE JUST ABOUT TO  
CRASH INTO THE PACIFIC NORTHWEST THIS EVE. OBJECTIVE UPPER ANALYSIS  
SHOWS A STRONG 110+ KT JET CORE OFFSHORE AT 21Z. THIS WILL BE OUR  
MAJOR WEATHER MAKER OVER THE NEXT COUPLE OF DAYS AS THE SYSTEM MOVES  
RAPIDLY SOUTHEAST AND STRENGTHENS. NOT EXPECTING ANYTHING MAJOR IN  
THE NEAR TERM THOUGH. SHOULD BE A QUIET EVENING WITH WINDS STARTING  
TO RELAX AS MIXING DWINDLES WITH THE LOSS OF AFTN HEATING. A BROAD  
AREA OF SURFACE HIGH PRESSURE WILL KEEP THINGS ON THE DRY SIDE.  
 
THINGS CHANGE QUICKLY INTO TONIGHT. THE NAM H85 CAG-CPR GRADIENT IS  
PROGGED TO CLIMB ABOVE 60 METERS BY ABOUT 09Z SAT. MODELED LLVL FLOW  
IS IMPRESSIVE TO SAY THE LEAST WITH AN EXTENSIVE CORE OF 60 TO 70 KT  
WINDS BETWEEN 700 AND 800 MILLIBARS OVER A GOOD CHUNK OF OUR WYOMING  
ZONES BY SUNRISE. WITH EXCELLENT SUBSIDENCE OVER THE TRADITIONAL GAP  
AREAS AND GOOD 6-HR PRESSURE FALLS ON THE ORDER OF 5-10 MB PER THE  
GFS...CONFIDENCE IS HIGH IN A WIDESPREAD AND POTENTIALLY SIGNIFICANT  
WIND EVENT. WENT AHEAD AND UPGRADED TO A HIGH WIND WARNING WITH ALL  
ZONES STARTING AT 09Z. ARL AND BRX SHOULD HIT FIRST...WITH THE WIND  
CORE ALOFT SPREADING INTO THE SOUTHERN LARAMIE RANGE/FOOTHILLS AT OR  
AROUND SUNRISE. ADDED THE NORTHERN LARAMIE RANGE TO THE WARNING AS  
WELL AS BOTH THE GFS AND NAM SHOW 65 KT WINDS AT H75 TO THE SOUTH OF  
DEER CREEK IN WESTERN CONVERSE COUNTY. THIS MAY BE QUITE THE EVENT  
WITH MULTIPLE GUSTS OVER 70 MPH. ANOTHER EVENTUAL CONCERN IS THE  
POTENTIAL FOR LIGHT SNOW WEST OF THE LARAMIE RANGE LATER IN THE  
AFTERNOON AND EVENING. WITH STRONG WINDS WILL COME THE POTENTIAL FOR  
SIGNIFICANTLY REDUCED VISIBILITIES IN BLOWING SNOW EVEN THOUGH LOWER  
ELEVATIONS SHOULD NOT SEE MUCH FOR ACCUMULATIONS. MADE IT A POINT TO  
MENTION THIS IN THE NPW PRODUCT.  
 
SOMEWHAT CONCERNED THAT SOME OF THE ADJACENT VALLEYS AND HIGH PLAINS  
MAY GET IN ON SOME OF THE WINDY FUN TOMORROW AS WELL. THERE ARE SOME  
KEY DIFFERENCES IN THE GFS AND NAM WHICH WILL HAVE A ROLE IN WHETHER  
OR NOT WE SEE WARNING CRITERIA WINDS AT AREAS SUCH AS CHEYENNE AND  
THE LARAMIE VALLEY. FORECAST SOUNDINGS FROM BOTH MODELS SHOW A BELT  
OF VERY STRONG FLOW NOT FAR OFF THE SURFACE. THE DIFFERENCES ARE IN  
THE MIXING. MAIN LIMITING FACTOR WILL BE CLOUD COVER...BUT BOTH THE  
LOW AND MIDLVL RH FIELDS DO NOT SUGGEST ANYTHING THICK ENOUGH. COULD  
EVENTUALLY SEE AN ABUNDANCE OF LENTICULARS EAST OF THE MOUNTAINS AS  
MOUNTAIN WAVE ACTIVITY BECOMES INTENSE IN THE AFTN. IF THIS DOES NOT  
IMPACT SURFACE HEATING...GFS SOUNDINGS SUGGEST 50-60 KTS AT THE TOP  
OF THE MIXED LAYER AT LARAMIE AND CHEYENNE. THE NAM IS CONSIDERABLY  
LESS...HOWEVER IT DOES SHOW SUBSIDENCE IN ITS OMEGA FIELDS SPREADING  
SLOWLY ONTO THE PLAINS BETWEEN 18-00Z. DECIDED TO ISSUE A HIGH WIND  
WATCH FOR LOWER ELEVATIONS IMMEDIATELY ADJACENT TO THE LARAMIE RANGE  
AND FOOTHILLS. EVEN IF AFTERNOON MIXING IS NOT THE CULPRIT...MODELS  
ARE IN GOOD AGREEMENT WITH A TRANSITION TO A BORA WIND EVENT ON SAT  
NIGHT THROUGH EARLY SUN AS A COLD FRONT SWEEPS ACROSS THE CWA. COULD  
SEE WIND GUSTS RAMP UP AGAIN FOR A FEW HOURS AROUND MIDNIGHT...WITH  
A FEW GUSTS TO 60 MPH POSSIBLE OVERNIGHT.  
 
SUNDAY WILL BE VERY WINDY OVER THE PLAINS OF SOUTHEAST WYOMING AND  
THE WESTERN PANHANDLE. THE CWA WILL BE IN THE POST FRONTAL AIR MASS  
AND THE MODELS SHOW A RIBBON OF 60 TO 70 KTS FROM NEAR LSK SOUTHEAST  
TOWARD SNY AT 00Z MON. WILL LIKELY NEED MORE WIND HEADLINES FOR THIS  
TIME FRAME...BUT WILL GET THROUGH THE SATURDAY EVENT FIRST. NOW THAT  
THE WIND DISCUSSION IS OUT THE WAY...ONTO THE SNOW POTENTIAL. DIDNT  
MAKE ANY CHANGES TO THE WINTER STORM WATCH FOR THE MOUNTAINS...BUT  
IT STILL LOOKS GOOD. FIREHOSE OF AN UPPER JET WITH 150+ KT H25 CORE  
IS PROGGED TO REMAIN ANCHORED OVER THE WESTERN US FOR SEVERAL DAYS  
WITH OUR MOUNTAINS REMAINING IN THE FAVORED LEFT EXIT REGION. THIS  
COMBINED WITH FAVORABLE OROGRAPHICS IN WEST-NORTHWEST FLOW AND AND  
SEVERAL REINFORCING SHOTS OF 700-300 MILLIBAR MOISTURE EMBEDDED IN  
THE ACTIVE FLOW ALOFT WILL SUPPORT PERIODS OF HEAVY SNOW. SHOULD SEE  
ONE OR TWO FEET THROUGH MON WITH ADDITIONAL SNOW POSSIBLE IN THE  
DAYS FOLLOWING. SHOULD BE PRIMARILY A MOUNTAIN EVENT WITH AREAS EAST  
OF THE LARAMIE RANGE STAYING DRY IN DOWNSLOPING LLVL FLOW. MAY SEE A  
FEW RAIN OR SNOW SHOWERS OVER THE NORTHERN PANHANDLE ON SUN AFTN AS  
PVA OVERSPREADS THE AREA.  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 345 PM MST FRI NOV 21 2014  
 
BASED ON GFS/ECMWF MODEL SOLUTIONS...SHOULD SEE A BREAK IN SNOW  
ACCUMULATIONS OVER SOUTHEAST WYOMING MOUNTAINS SUNDAY EVENING WITH  
A SHORTWAVE RIDGE IN PLACE. THEN THE NEXT SHOT OF SNOW LIKELY TO  
DEVELOP AFTER MIDNIGHT SUNDAY NIGHT. COULD SEE SOME LIGHT SNOW  
INTO LOWER ELEVATIONS BUT MOST SNOW ACCUMULATIONS WILL GENERALLY  
BE IN THE MOUNTAINS. VERY LITTLE CHANCE FOR ANY ACCUMULATIONS  
EAST OF THE LARAMIE RANGE SUNDAY NIGHT THROUGH MONDAY. WINDS WILL  
SUBSIDE ACROSS MOST OF THE AREA SUNDAY NIGHT BUT ANOTHER PUSH OF  
STRONGER WINDS POSSIBLE MONDAY NIGHT AS ANOTHER STRONG UPPER LEVEL  
JET MOVES OVER THE AREA. MAIN CONCERN FOR HIGH WINDS WILL BE OVER  
THE FAVORED WIND PRONE LOCATIONS IN SOUTHEAST WYOMING SUCH AS  
ARLINGTON...BORDEAUX AND THE SOUTHERN LARAMIE RANGE.  
 
THE NEXT QUICK MOVING CLIPPER SYSTEM ALONG WITH THE UPPER JET  
WILL BRING A CHANCE FOR LIGHT SNOW SHOWERS THROUGH TUESDAY  
AFTERNOON...INCLUDING INTO THE NEBRASKA PANHANDLE. AT THIS TIME  
NOT EXPECTING MUCH IN THE WAY OF SNOW ACCUMULATIONS...IF ANY. MAINLY  
LOOKING FOR LIGHT SNOW SHOWERS AND FLURRIES.  
 
UNCERTAINTLY REMAINS FOR LATER PORTIONS OF THE WEEK AND HOLIDAY  
WEEKEND GIVEN THE GFS AND ECMFW WERE COMPLETELY DIFFERENT IN  
THEIR SOLUTIONS YESTERDAY. HOWEVER...BOTH MODLES TRENDED TOWARD  
EACH OTHER TODAY AND HAVE RATHER SIMILAR SOLUTIONS. WOULD LIKE TO  
SEE RUN OR TWO OF CONSISTENCY BUT BASED ON LATEST SOLUTIONS IT  
WOULD WARM BOTH THURSDAY AND FRIDAY WITH A FLATTENING RIDGE OVER  
THE NORTHERN ROCKIES PRODUCING DOWNSLOPE WARMING. INTO THE  
WEEKEND THE MODLES SUGGEST A FAST MOVING BUT RELATIVELY WEAK WAVE  
MOVING ACROSS THE AREA...SO NO BIG HAZARDOUS WEATHER THREAT  
EXPECTED AT THIS TIME.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 234 PM MST FRI NOV 21 2014  
 
AVIATION CONCERNS TO MAINLY FOCUS ON WINDS LATE TONIGHT AND INTO  
TOMORROW AND SNOW WHICH WILL DEVELOP OVER THE MOUNTAINS TOMORROW  
AFTERNOON. STRONG WINDS WITH FREQUENT GUSTS TO 50 KTS AND GREATER  
WILL DEVELOP IN THE ARLINGTON AREA AND INTO THE BORDEAUX AREA  
LATE TONIGHT. THESE STRONG WEST TO SOUTHWEST WINDS WILL THEN  
SPREAD INTO THE SOUTHERN AND NORTHERN LARAMIE RANGES TOWARD  
SUNRISE SATURDAY. GUSTY WINDS WILL ALSO SPREAD INTO LOWER  
ELEVATIONS AND INTO THE PLAINS OF SOUTHEAST WYOMING SATURDAY  
AFTERNOON WITH GUSTS OF 30 TO 40 KTS BEING COMMON. WINDS WILL NOT  
BE AS STRONG INTO THE NEBRASKA PANHANDLE BUT STILL BREEZY TO WINDY  
SATURDAY AFTERNOON.  
 
MOUNTAINS WILL BE OBSCURED DUE TO FALLING AND BLOWING SNOW  
SATURDAY AFTERNOON...ESPECIALLY INTO THE SNOWY AND SIERRA MADRE  
RANGES WHERE A WINTER STORM WATCH IS CURRENTLY IN EFFECT. PERIODS  
OF SNOW WILL CONTINUE INTO MONDAY ACROSS THESE MOUNTAINS.  
 
STRONG NORTHWEST WINDS EXPECTED OVER THE NEBRASKA PANHANDLE SUNDAY  
WITH STRONGER WINDS ALSO POSSIBLE INTO SOUTHEAST WYOMING.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 559 AM MST FRI NOV 21 2014  
 
ONE LAST MILD...BREEZY AND DRY DAY IS EXPECTED FOR THE DISTRICT  
TODAY. STRONG WINDS AND PERIODS OF SNOW WILL OCCUR IN AND NEAR THE  
MOUNTAINS OF SOUTHEAST WYOMING THROUGH MIDDLE OF NEXT WEEK. WINDY  
CONDITIONS WILL EXPAND TO THE PLAINS ON SUNDAY AND WILL CONTINUE  
THROUGH MIDWEEK AS WELL  
 

 
   
CYS WATCHES/WARNINGS/ADVISORIES
 
 
WY...WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH MONDAY  
AFTERNOON FOR WYZ112-114.  
 
HIGH WIND WARNING FROM 2 AM SATURDAY TO 5 AM MST SUNDAY FOR  
WYZ103>106-110-116-117.  
 
HIGH WIND WATCH FROM SATURDAY MORNING THROUGH LATE SATURDAY  
NIGHT FOR WYZ101-107-115-118.  
 
NE...NONE.  
 

 
 

 
 
SHORT TERM...CLH  
LONG TERM...SML  
AVIATION...SML  
FIRE WEATHER...RJM  
 
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