833  
FXUS65 KCYS 311149  
AFDCYS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHEYENNE WY  
550 AM MDT FRI OCT 31 2014  
   
SHORT TERM
 
(TODAY THROUGH SUNDAY)  
ISSUED AT 352 AM MDT FRI OCT 31 2014  
 
MAIN FORECAST IMPACT TODAY WILL BE MORNING FOG. 09Z SATELLITE FOG  
PRODUCT SHOWS WELL DEFINED AREA OF LOW CLOUDS/FOG EXTENDING FROM  
NORTHEAST WY THRU AREAS NORTH OF THE PINE RIDGE...SOUTHEAST INTO  
CENTRAL NEBRASKA. THIS IN LIGHT EASTERLY FLOW AS 1040MB SFC HIGH  
SETTLES INTO THE DAKOTAS. LLVL INVERSION IS STEEPENED BY AN  
APPROACHING UPSTREAM RIDGE. DEW POINT DEPRESSIONS ARE WITHIN 2-3F  
ACROSS THE WRN NEBRASKA PANHANDLE AND AREAS IN SE WY ALONG THE  
STATELINE. LATEST HRRR SHOWS THE AREA OF FOG PROGRESSING WESTWARD  
INTO THE WRN NEBRASKA PANHANDLE THRU DAYBREAK AND INTO THE SE  
WYOMING PLAINS SHORTLY THEREAFTER. THIS SOLUTION SEEMS REASONABLE  
GIVEN EARLY MORNING DEW POINT DEPRESSION TRENDS. FOG LOOKS TO BE  
FAIRLY PATCHY AT THIS POINT...ALTHOUGH IT MAY BE LOCALLY DENSE IN  
SOME AREAS. THE LATEST HRRR SHOWS FOG /LOW CLOUDS PERSISTING  
ACROSS LARAMIE COUNTY THE LONGEST THIS MORNING NOT DISSIPATING  
UNTIL AROUND MIDDAY. OTHERWISE...A DRY DAY AHEAD AS RIDGE AXIS  
PASSES THRU THE CWFA. CLOUDS WILL BE ON THE INCREASE THO AS WELL  
AS MOISTURE ABOVE H5 BUMPS INTO THE RIDGE AXIS. THE OTHER CONCERN  
TODAY IS THE POTENTIAL FOR WIND ADVISORY SPEEDS IN THE NRN  
NEBRASKA PANHANDLE...SPECIFICALLY NR THE PINE RIDGE. ALL OUTPUT IS  
POINT TO MARGINAL WINDS WITH A LOCAL MAXIMUM OVR THE PINE RIDGE.  
MODELS OFTEN UNDERDO WIND SPEEDS FOR THIS AREA IN STRONG SSE SFC  
FLOW. SO...WILL ISSUE A WIND ADVISORY FOR SIOUX...DAWES...AND BOX  
BUTTE COUNTIES EFFECTIVE 16Z-01Z TODAY.  
 
FLOW BACKS TO THE SOUTHWEST AHEAD OF THE WRN CONUS TROUGH FOR  
SATURDAY. THIS WILL RESULT IN THE WARMEST DAY OF THE PERIOD AS THE  
LEE-SIDE TROUGH DEVELOPS AND AMPLIFIES. HIGH TEMPS SATURDAY WILL  
RISE WELL INTO THE 60S WITH LOW 70S ACROSS E-C WY AND PORTIONS OF  
THE WRN NE PANHANDLE. BREEZY CONDITIONS WILL DEVELOP...SOUTHWEST AT  
20 TO 30 MPH WEST OF THE LARAMIE RANGE...SOUTH/SOUTHEAST AT 10 TO 20  
MPH OUT ON THE ERN PLAINS.  
 
MODELS CONTINUE TO SPLIT THE ENERGY OF THE NEXT TROUGH ON  
SUNDAY...WITH ONE PIECE EJECTING NORTHEAST ACROSS MONTANA WHILE THE  
SOUTHERN SYSTEM APPROACHES THE FOUR CORNERS. THIS MEANS A LATER  
ARRIVAL IN PRECIP CHANCES...WHICH WILL LIKELY NOW HOLD OFF UNTIL  
SUNDAY AFTERNOON OR AFTER. BEST CHANCES WILL BE IN OROGRAPHICALLY  
FAVORED AREAS OF THE SNOWY AND SIERRA MADRE RANGES. THICKER CLOUD  
CANOPY AND APPROACHING COLD FRONT WILL YIELD A COOLER DAY  
SUNDAY...WITH HIGHS NR 50 WEST AND IN THE UPPER 50S AND LOW 60S  
EAST.  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 352 AM MDT FRI OCT 31 2014  
 
LONG RANGE MODELS CONTINUE TO COME INTO BETTER AGREEMENT WITH THE  
PACIFIC STORM SYSTEM FORECAST TO PUSH ACROSS THE CENTRAL ROCKY  
MOUNTAINS EARLY NEXT WEEK. MODELS INDICATE SPLIT FLOW WILL DEVELOP  
ACROSS THE GREAT BASIN REGION LATE THIS WEEK...AND IT APPEARS THE  
SOUTHERN PORTION OF THE ENERGY AND UPPER JET WILL IMPACT SOUTHEAST  
WYOMING AND WESTERN NEBRASKA AS THE NORTHERN PORTION WILL BE  
EJECTED NORTHEAST INTO MONTANA ON SUNDAY. THIS WILL ALLOW THE  
SOUTHERN BRANCH OF THE JET TO BECOME MORE DOMINANT INTO EARLY  
MONDAY MORNING...WITH THE POTENTIAL FOR RAIN/SNOW ALONG I80.  
MODELS ARE TRENDING SLOWER WITH THE SOUTHERN SYSTEM...WITH MOST OF  
THE PRECIPITATION HOLDING OFF UNTIL MONDAY. THE ECMWF IS THE MOST  
AGGRESSIVE...WITH THE GFS AND NAM A CLOSE SECOND...SHOWING DECENT  
QPF AMOUNTS AS A 100KT JET DEVELOPS AND PUSHES NORTHWARD OUT OF  
THE SOUTHWEST UNITED STATES. EVEN WITH THE INCONSISTENCIES BETWEEN  
INDIVIDUAL MODEL RUNS REGARDING TIMING BETWEEN SUNDAY AND  
MONDAY...CURRENT 00Z MODELS ARE IN GOOD ENOUGH AGREEMENT TO  
INCREASED POP BETWEEN 30 TO 50 PERCENT ALONG THE I80 CORRIDOR  
NORTHWARD TO THE PLATTE RIVER VALLEY. EXPECT RAIN TO MIX WITH AND  
CHANGE TO SNOW DOWN TO 5500 FEET. HOWEVER...ACCUMULATIONS APPEAR  
MINIMAL AT THIS TIME SINCE MOST OF THE PRECIP WILL OCCUR DURING  
THE DAY...BUT WILL KEEP AN EYE ON THIS AS SOME SLIGHT TIMING  
DIFFERENCES ARE LIKELY. TEMPERATURES ON MONDAY ARE EXPECTED TO BE  
10 TO 15 DEGREES BELOW NORMAL WITH HIGHS STRUGGLING TO REACH 4O TO  
45 DEGREES...AND MODELS CONTINUE TO TREND COOLER...SO THESE VALUES  
MAY BE A LITTLE TOO HIGH. LOW TEMPERATURES IN THE TEENS TO MID  
20S ARE EXPECTED BY LATE MONDAY NIGHT AS THE COOLER AIR SETTLES  
OVER THE REGION...BUT WITH SOME CLOUD COVER OVER THE  
AREA...TEMPERATURES WILL PROBABLY NOT LOWER ANY COLDER THAN 20 IN  
MOST LOCATIONS. PRECIPITATION WILL BE PRETTY LIGHT FURTHER TO THE  
NORTH BUT MAY SEE MODERATE QPF VALUES AROUND 0.50 INCHES ALONG THE  
I80 CORRIDOR WHERE THE BEST DYNAMICS WILL BE LOCATED.  
 
THE UPPER LEVEL TROUGH WILL PUSH EAST OF THE REGION LATE MONDAY  
AND INTO TUESDAY OF NEXT WEEK RESULTING IN BROAD NORTHWEST FLOW  
ALOFT AND COOL TEMPERATURES. MAINLY DRY CONDITIONS ARE EXPECTED  
INTO THE MIDDLE OF NEXT WEEK WITH HIGH TEMPERATURES INCREASING TO  
NEAR NORMAL...AND GENERALLY IN THE 50S AND LOW 60S. THE ONLY MINOR  
CONCERN IS SOME MODEL DISAGREEMENT WITH A RELATIVELY STRONG COLD  
FRONT ON WEDNESDAY. THE GEM IS THE ONLY MODEL INDICATING A BACK  
DOOR COLD FRONT PUSHING SOUTH THROUGH THE AREA ON  
WEDNESDAY...WHICH WILL RESULT IN TEMPERATURES 10 TO 15 DEGREES  
COOLER THAN OUR CURRENT FORECAST INDICATES. HOWEVER...THE GEM  
CONTINUES TO BE THE OUTLIER SO WILL NOT ADJUST THE FORECAST FOR  
WEDNESDAY TOO MUCH AT THIS TIME.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH TONIGHT)  
 
SURFACE HIGH PRESSURE IS CURRENTLY MOVING SOUTHWARD OVER THE GREAT  
PLAINS THIS MORNING...WHICH HAS RESULTED IN SURFACE WINDS ACROSS THE  
HIGH PLAINS SHIFTING INTO THE SOUTH AND SOUTHEAST. UPSLOPE FLOW WILL  
CONTINUE THIS MORNING WITH PATCHY FOG POSSIBLE ALONG WITH LOW CIGS.  
PERIODS OF IFR ARE EXPECTED OVER THE NEXT FEW HOURS BUT CONDITIONS  
WILL IMPROVE BY NOON AS SKIES WILL CLEAR OUT FROM WEST TO EAST.  
WINDY CONDITIONS WILL DEVELOP BY LATE THIS MORNING AND WILL CONTINUE  
THROUGH THIS AFTERNOON AND THIS EVENING OVER MOST OF THE FORECAST  
AREA.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 352 AM MDT FRI OCT 31 2014  
 
ALTHOUGH A DRY DAY...A CLOUDY OR FOGGY START IN MANY AREAS EAST  
OF THE LARAMIE RANGE THIS MORNING. THIS WILL BE SLOW TO LIFT AND  
BURN OFF...LIKELY NOT UNTIL LATE THIS MORNING OR AROUND MIDDAY.  
WINDS WILL BE BREEZY WITH GUSTS OF 30 TO 40 MPH COMMON ACROSS MUCH  
OF THE AREA. HUMIDITIES WILL FALL INTO THE UPPER TEENS OVER  
CARBON/ALBANY COUNTIES THIS AFTERNOON. SATURDAY WILL OFFER THE  
WARMEST DAY WITH HIGHS RISING INTO THE 60S TO LOW 70S OVER MUCH OF  
THE SOUTHEAST WYOMING PLAINS. THE NEXT SYSTEM WILL BRING COOLER  
TEMPERATURES ALONG WITH COOLER TEMPERATURES BY LATE SUNDAY AND  
ESPECIALLY ON MONDAY.  
 

 
   
CYS WATCHES/WARNINGS/ADVISORIES
 
 
WY...NONE.  
NE...WIND ADVISORY FROM 10 AM THROUGH 7 PM FOR NEZ002-003-095-096.  
 

 
 

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