Weather Service Report


284 
FXUS65 KCYS 282308
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
408 PM MST FRI NOV 28 2014

.SHORT TERM...(TONIGHT THROUGH SUNDAY) 
ISSUED AT 402 PM MST FRI NOV 28 2014

HIGH WIND WARNINGS CONTINUE THIS AFTERNOON FOR THE WIND PRONE AREAS 
AS WELL AS THE PLAINS OF EASTERN PLATTE COUNTY. HIGHEST GUSTS SO FAR 
HAVE BEEN IN THE SOUTHERN LARAMIE RANGE FOOTHILLS AND EASTERN PLATTE 
COUNTY WITH GUSTS AROUND 65 MPH OBSERVED IN THE PAST COUPLE OF HOURS 
AT COLEMAN ALONG I25 AND OTTO ROAD SOUTHWEST OF CYS. AM SURPRISED WE 
HAVE NOT BEEN ABLE TO ACHIEVE GUSTS OVER THE I80 SUMMIT...OR ARL/BRX 
YET AS MIXING SHOULD NOT BE INHIBITED. A FEW WAVE CLOUDS ARE HANGING 
AROUND BUT RECENT VISIBLE SATELLITE SHOWS GENERALLY THIN CIRRUS AND 
SFC OBS SHOW DECENT SFC HEATING. PERHAPS THE CAG-CPR GRADIENT IS NOT 
STRONG ENOUGH YET FOR THE GAP AREAS...BUT THOSE VALUES SHOULD CLIMB 
ABOVE 65 METERS AT BOTH 700 AND 850 HPA AFTER 03Z TONIGHT. GAP AREAS 
SHOULD GET WINDIER OVER THE NEXT FEW HOURS...AND KEEP GUSTING AROUND 
60 MPH THROUGH THE NIGHT. WARNING ISSUED EARLIER LOOKS GOOD AND WILL 
MAKE NO CHANGES WITH THE AFTN PACKAGE. NOT A GOOD PATTERN WITH LLVL 
INVERSIONS TO KEEP BIG WINDS GOING OVER THE LOW ELEVATIONS OUTSIDE 
OF THE GAPS OVERNIGHT...SO EXPECT A LULL OVER EASTERN PLATTE COUNTY 
AFTER DARK. 

STILL SOME QUESTIONS AS TO HOW THIS WIND EVENT WILL EVOLVE OVER THE 
NEXT 12 TO 24 HOURS. WARNING CRITERIA GUSTS WILL REMAIN A CONCERN AS 
LONG AS LLVL GRADIENTS REMAIN HIGH. THE NAM SHOWS AT LEAST 60 METERS 
FOR A CAG-CPR GRADIENT AT H85 AND 70 METERS AT H7 THRU 06Z SUN. IT 
WOULD NOT BE SURPRISING IF LATER SHIFTS NEED TO EXTEND THE HIGH WIND 
WARNING BEYOND THE CURRENT 00Z SUN EXPIRATION AS WINDS ALOFT LOOK TO 
REMAIN VERY STRONG. GFS AND NAM CONTINUE TO SHOW A CORRIDOR OF H75-
H8 WINDS ABOVE 50 KTS ALONG AND EAST OF THE LARAMIE RANGE...AS WELL 
AS THE FERRIS AND SEMINOE MOUNTAINS IN NORTHERN CARBON. MIGHT SEE A 
FEW GUSTS CLOSE TO 75 MPH AT BORDEAUX IF THE NAM IS RIGHT. 60 TO 65 
KTS AT H75 IS MORE THAN A LITTLE CONCERNING AT 18Z WHEN AFTN MIXING 
SHOULD PEAK. NOT NEARLY AS MANY CLOUDS TOMORROW WITH FAIRLY DRY RH 
PROGS OVER THE PLAINS. JUST DEPENDS ON WHERE THE LENTICULARS DECIDE 
TO SET UP. MIGHT NEED TO CONSIDER ADDING THE NORTHERN LARAMIE RANGE 
TO THE WARNING AS ALL MODELS SHOW H7 WINDS IN EXCESS OF 60 KTS...75 
KTS PER THE MORE AGGRESSIVE NAM. NOT AN EASY ZONE TO HIT FOR THE 60 
MPH SUSTAINED WITH GUSTS TO 75 MPH CRITERIA THOUGH. FCST SOUNDINGS 
SHOW GOOD LLVL MIXING TOMORROW SO EXPECT WINDS WILL REALLY CRANK UP 
OVER THE PLAINS AS WELL WITH SUCH STRONG FLOW ALOFT. OPTED TO KEEP 
EASTERN PLATTE IN THE WARNING. LATER SHIFTS WILL NEED TO LOOK INTO 
CONVERSE COUNTY AND CENTRAL LARAMIE COUNTY. CONCERN HERE IN CHEYENNE 
IS WEAK COLD ADVECTION AT H7 LATER IN THE AFTN WHICH COULD STEEPEN 
LAPSE RATES. SUBSIDENCE WILL BE IMPRESSIVE TOO IN ASSOCIATION WITH A 
120 KT H25 JET. DID NOT GO WITH A WATCH FOR THIS ZONE AS THE MAV MOS 
GUIDANCE DOES NOT SHOW ANYTHING MORE THAN 25 KTS SUSTAINED. MIGHT 
SEE A BIT OF A BORA ALONG AND JUST EAST OF THE LARAMIE RANGE LATE SAT
NIGHT AS COLD ADVECTION KICKS IN. BULLSEYE OF STRONGEST FLOW ALOFT
IN THE MODELS IS OVER THOSE ZONES AT 06Z SUN. LOOKS A LITTLE MORE
FAVORABLE FOR OUR NEIGHBORS TO THE SOUTH IN THE BOU CWA AS THE
COLD INTRUSION ALOFT IS SLIGHTLY MORE EVIDENT.

ASIDE FROM THE WIND...ANOTHER WARM DAY IS EXPECTED FOR SAT WITH H7 
TEMPS AROUND 2 DEG C OVER THE EASTERN PLAINS AND GOOD DOWNSLOPING 
WINDS ALLOWING FOR COMPRESSIONAL WARMING. BELIEVE IT OR NOT...WINDS 
SHOULD FINALLY START TO COME DOWN ON SUN. WE HAVE A COLD FRONT TO 
THANK FOR THAT WITH FROPA OCCURRING LATE SAT NIGHT. STRONG PRESSURE 
RISES IN EXCESS OF 12 MB / 6 HR SPREADING INTO OUR NORTHERN ZONES 
SHOULD EFFECTIVELY KILL THE LLVL GRADIENTS AND WEAKEN THE ATTENDANT 
FLOW IN THE LOW TO MIDLVLS. PROBABLY STILL STAYING A LITTLE BREEZY 
WEST OF THE LARAMIE RANGE THOUGH AS MODELS TEND TO STALL THE FRONT 
ALONG THE TERRAIN. SFC CONVERGENCE AND INCREASING MIDLVL MOISTURE 
SHOULD SUPPORT LIGHT SNOW PRODUCTION ACROSS THE AREA FROM SOUTHWEST 
TO NORTHEAST. SHOULD ALSO SEE SOME DECENT LIFT IN THE RIGHT REAR 
QUAD OF THE UPPER JET. INCREASED POPS TO NEAR LIKELIES ACROSS THE 
NORTH ON SUNDAY AFTERNOON PER COORDINATION WITH UNR AND RIW. DO NOT 
EXPECT ANYTHING CRAZY WITH THE STRONGEST PVA BEING WELL TO THE NORTH 
OF THE CWA...BUT SHOULD SEE AN INCH OR TWO OF ACCUMULATION. IT WILL 
BE A GOOD 15 TO 20 DEGREES COOLER ON SUN WITH H7 TEMPS FALLING TO 
AROUND -10 DEG C ACROSS THE NORTH PER THE GFS.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) 
ISSUED AT 402 PM MST FRI NOV 28 2014

THE PROGRESSIVE PATTERN CONTINUES DURING THIS PERIOD AS A SERIES OF 
SHORTWAVE TROUGHS RIDE ACROSS THE NRN CONUS VIA SWIFT ZONAL FLOW. 
THE PERIOD WILL BEGIN WITH A STATIONARY SFC FRONT THAT WILL BE 
LOCATED ACROSS CARBON AND ALBANY COUNTIES EXTENDING SOUTH ALONG THE 
FRONT RANGE. FORCING ALONG THE SFC FRONT ALONG WITH MOISTURE AND RRQ 
SUPPORT SHOULD BE ENOUGH TO PRODUCE A PERIOD OF LIGHT SNOW ACROSS 
CARBON...ALBANY AND LARAMIE COUNTIES. THE BRIEF RESIDENCE TIME OF 
THE FORCING WILL LIMIT SNOWFALL TOTALS...WHICH WILL BE GENERALLY 1-3 
INCHES ACROSS THIS AREA. HIGHEST AMOUNTS WILL BE OVER THE 
SNOWY/SIERRA MADRE RANGES. THE FRONT RETREATS QUICKLY FROM WEST TO 
EAST ON MONDAY...BUT NOT BEFORE PRODUCING WHAT LOOKS TO BE THE 
COLDEST DAY OF NEXT WEEK WITH HIGHS ONLY REACHING INTO THE 30S MOST 
PLACES.

ANOTHER BRIEF HIGH WIND EVENT WILL TAKE SHAPE FOR MONDAY NT/EARLY 
TUESDAY AS GRADIENT BEHIND THE DEPARTING FRONT COMBINES WITH A FAST 
MOVING SHORTWAVE TROUGH TRACKING ALONG THE US/CANADIAN BORDER. H7 
WIND PROGS OF AROUND 60 KNOTS SUGGESTS AT LEAST THE POTENTIAL FOR 
HIGH WINDS AT WIND PRONE LOCALES. OTHERWISE MILD TEMPS RETURN FOR 
TUESDAY WITH 40S TO LOW 50S EXPECTED.

FLOW WILL BACK ON WEDNESDAY AHEAD OF AN APPROACHING SHORTWAVE 
TROUGH. TIMING AND STRENGTH DIFFERENCES EXIST ON THIS FTR WITH THE 
GFS STRONGEST AND EARLIER WITH PRECIP ONSET. MEANWHILE THE ECMWF IS 
SIGNIFICANTLY SLOWER AND DRIER BY COMPARISON. FOR NOW WILL GENERALLY 
SIDE WITH THE DRIER OUTCOME...BUT DID KEEP SOME SMALL PRECIP CHANCES 
OVR NRN AND WRN ZONES ON WEDNESDAY. FLOW WILL TURN MORE ZONAL AGAIN 
FOR THU AND FRIDAY AS A WEAK RIDGE DEVELOPS OVR THE WRN CONUS. FOR 
NOW THE LATTER HALF OF NEXT WEEK LOOKS TO REMAIN DRY AND MILD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 402 PM MST FRI NOV 28 2014

VFR CONDITIONS WILL PREVAIL THRU THE PERIOD. STRONG WINDS WILL CARRY 
THE GREATEST IMPACT TO AVIATION INTERESTS OVER THE UPCOMING TAF 
CYCLE. WEST/SOUTHWEST WINDS WILL GUST TO 25-35 KNOTS AT SE WY 
AIRFIELDS THROUGH THE ENTIRE UPCOMING PERIOD. THE LIGHTEST AMOUNTS 
WILL LIKELY BE DURING THE OVERNIGHT HOURS...WHILE THE STRONGEST WILL 
BE DURING THE AFTERNOONS. WINDS WILL BE LESS AT NEBRASKA PANHANDLE 
SITES WITH WEST WINDS AT 10 TO 15 KNOTS WITH OCCASIONAL GUSTS OF UP 
TO 25 KNOTS. WINDS OVER THE PANHANDLE WILL BECOME LESS GUSTY AS WELL 
DURING THE OVERNIGHT HOURS. OTHERWISE...JUST EXPECT DECREASING HIGH-
LEVEL CLOUDS THRU THE PERIOD.

&&

.FIRE WEATHER...
ISSUED AT 300 AM MST FRI NOV 28 2014

MINIMAL FIRE WEATHER ISSUES ANTICIPATED THIS HOLIDAY WEEKEND.
UNSEASONABLY MILD TEMPERATURES WILL CONTINUE THROUGH SATURDAY.
LOWEST RELATIVE HUMIDITIES WILL RANGE FROM 15 TO 20 PERCENT
IMMEDIATELY EAST OF THE LARAMIE RANGE. STRONG AND GUSTY WEST TO
SOUTHWEST WINDS WILL PREVAIL ACROSS MUCH OF SOUTHEAST WYOMING...
MAINLY DURING THE DAYLIGHT HOURS. A ARCTIC COLD FRONT WILL PUSH
SOUTH ACROSS THE PLAINS AND STALL NEAR THE FRONT RANGE
SUNDAY...BRINGING MUCH COLDER TEMPERATURES AND CHANCES FOR LIGHT
RAIN AND SNOW.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WARNING UNTIL 6 PM MST SATURDAY FOR WYZ104-106-107-110-
     116-117.

NE...NONE.
&&

$$

SHORT TERM...CLH
LONG TERM...CAH
AVIATION...CAH
FIRE WEATHER...MJ/CLH

Return to Home page


Western Regional Climate Center, wrcc@dri.edu