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000
FXUS65 KCYS 070539
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1039 PM MST FRI DEC 6 2013

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 411 PM MST FRI DEC 6 2013

A LOOK AT WATER VAPOR IMAGERY SHOWS THE DEEP UPPER LEVEL TROUGH
REMAINING IN CONTROL OF THE WEATHER PATTERN...WITH A STRONG
EMBEDDED SHORTWAVE DIVING SOUTHWARD ALONG THE PACIFIC COAST. OVER
THE ROCKIES...FLOW ALOFT IS MOSTLY ZONAL IN NATURE BUT WILL BEGIN
TO BACK TO THE SOUTHWEST TONIGHT AS THE SHORTWAVE DIGS INTO
CALIFORNIA. VERY COLD TEMPERATURES OCCURRED ONCE AGAIN TODAY WITH
HIGHS STRUGGLING TO REACH POSITIVE VALUES IN MANY LOCATIONS. HIGH
CLOUDS STREAMED OVERHEAD FROM THE WEST AND A LLVL STRATUS DECK
DEVELOPED IN EASTERN COLORADO AND MOVED UP INTO THE EASTERN
WY/WESTERN NE PLAINS THIS AFTERNOON. LIGHT SNOW WAS ALSO RECORDED
AT MANY LOCATIONS THROUGH THE DAY DUE TO THE VERY COLD AIRMASS AND
UPSLOPE FLOW IN PLACE.

AS THE SHORTWAVE DIGS INTO CA/OR/NV TONIGHT...SFC CYCLOGENESIS
WILL OCCUR OVER THE GREAT BASIN. AS MENTIONED PREVIOUS...FLOW
ALOFT WILL BACK TO THE SOUTHWEST AND WILL STRENGTHEN...INDUCING
WAA OVER THE CWA. THE MOST INTENSE WAA WILL OCCUR LATE SATURDAY
MORNING...WITH A WEAK PSEUDO-WARM FRONTAL FEATURE MOVING NORTHWARD
ACROSS THE CWA EARLIER IN THE MORNING. SO...TONIGHT SHOULD BE
ANOTHER VERY COLD NIGHT AHEAD OF THE WAA SCENARIO...WITH TEMPS
EXPECTED TO PLUMMET WELL BELOW ZERO ONCE AGAIN. WITH THE EAST-WEST
GRADIENT STRENGTHENING IN RESPONSE TO CYCLOGENESIS OUT WEST
...SOUTH-SOUTHEASTERLY WINDS SHOULD BE ON THE RISE OVERNIGHT.
THIS SHOULD HELP TO MODERATE TEMPS SOMEWHAT...ALTHOUGH WILL KEEP WIND
CHILLS FRIGID ESPECIALLY AS THE WINDS FIRST PICK UP AROUND
MIDNIGHT. THEREFORE...ISSUED ANOTHER WIND CHILL ADVISORY IN THE
PANHANDLE FOR READINGS EXPECTED TO BE IN THE MINUS TWENTIES...AND
A WIND CHILL WARNING FOR THE LARAMIE VALLEY BASED ON PERSISTENCE.
THINKING THE COLDEST TEMPS WILL OCCUR AROUND AND JUST AFTER
MIDNIGHT...WITH A SLIGHT RISE AS THE WEAK FRONT MOVES NORTHWARD
THROUGH THE MORNING. LIGHT SNOW SHOWERS WILL INCREASE IN COVERAGE
WITHIN THE CONVERGENCE ZONE OF THE FRONT WHICH LOOKS TO STALL
ALONG THE NORTHERN TIER OF COUNTIES SATURDAY MORNING.

MAX TEMPS FOR SATURDAY WILL BE 5 TO 10 DEGREES WARMER THAN
TODAY...AND SNOW WILL BEGIN TO SPREAD FROM SOUTHWEST TO
NORTHEAST ACROSS THE CWA AS THE STRONG SHORTWAVE MOVES TOWARD THE
ROCKIES. THE STRONGEST SYNOPTIC LIFT WILL REMAIN WELL SOUTH OF THE
FORECAST AREA...BUT STRENGTHENING SOUTHWEST FLOW AT THE JET LEVEL
WILL COMBINE WITH WEAKER EMBEDDED MID LEVEL ENERGY TO PROVIDE SOME
BROAD SCALE LIFT FOR SNOW. THE ASSOCIATED COLD FRONT WILL MOVE
THROUGH FROM THE NORTHWEST EARLY SUNDAY MORNING...AND SO TRENDED
POPS TO FOLLOW FROPA. MAINTAINED CHANCE TO LIKELY POPS WITH THE
FRONT...AND MORE PERSISTENT LIKELY POPS IN THE MOUNTAINS DUE TO
GENERAL OROGRAPHIC LIFT WITH HIGHER SNOW RATES DURING FROPA. DUE
TO LACK OF STRONG SYNOPTIC LIFT...OVERALL SNOW ACCUMULATIONS WILL
BE FAIRLY LIGHT...WITH 3 TO 6 INCHES LOOKING A GOOD BET IN THE
MOUNTAINS AND 1 TO 3 INCHES IN THE HIGH VALLEYS AND ACROSS THE
EASTERN PLAINS.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 411 PM MST FRI DEC 6 2013

A SMALL REINFORCING SHOT OF COLDER AIR WILL KEEP TEMPERATURES
QUITE COLD SUNDAY NIGHT AND MONDAY WHILE THE MAIN UPPER TROF FINALLY
PASSES EAST ACROSS THE REGION. A RETURN TO MILDER AND MAINLY DRY
CONDITIONS WILL THEN BEGIN TUESDAY AND CONTINUE THROUGH THURSDAY
AS THE SFC FLOW BECOMES DOWNSLOPE AND THE COLD AIR MASS MOVES EAST
OF THE REGION. LOOKS LIKE A WINDY PERIOD MONDAY INTO MONDAY NIGHT
AS A SHORTWAVE PASSES BY TO THE NORTHEAST BUT STILL INCREASES THE
SURFACE PRESSURE GRADIENT. MILD CONDITIONS TUESDAY AND WEDS AS THE
UPPER FLOW GRADUALLY BACKS TO WESTERLY. SOME MINOR COOLING MAY
ARRIVE FRIDAY AS A BACK-DOOR FRONT MOVES SOUTH ACROSS THE PLAINS
AND BACKS UP AGAINST THE MTNS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY EVENING)
ISSUED AT 1035 PM MST FRI DEC 6 2013

VFR CEILINGS BETWEEN 4000 AND 10000 FT AGL WILL PREVAIL TONIGHT...
WITH MVFR DEVELOPING BY SUNRISE THROUGH THE VALLEYS OF SOUTHEAST
WY AND WESTERN NE PANHANDLE. SURFACE WINDS WILL BE LIGHT SOUTH TO
SOUTHWEST FOR THE WY TERMINALS AND EAST TO SOUTHEAST FOR THE
NE PANHANDLE TERMINALS. EXTENSIVE MVFR TO LOCAL IFR CEILINGS WILL
SPREAD FROM WEST TO EAST SATURDAY MORNING AND AFTERNOON AS THE NEXT
LOW PRESSURE SYSTEM APPROACHES. LIGHT SNOW WILL LOWER VISIBILITIES
TO MVFR WEST OF THE LARAMIE RANGE SATURDAY MORNING. THE MOUNTAINS
WILL BECOME OBSCURED BY SATURDAY MORNING.

&&

.FIRE WEATHER...
ISSUED AT 411 PM MST FRI DEC 6 2013

NO FIRE WEATHER CONCERNS ARE EXPECTED THROUGH NEXT WEEK. TEMPERATURES
WILL REMAIN WELL BELOW NORMAL THROUGH EARLY NEXT WEEK...THEN
READINGS WILL MODERATE TO AT OR ABOVE NORMAL STARTING ON
WEDNESDAY. THE WIDESPREAD SNOW COVER WILL PERSIST THROUGH THE
EARLY PART OF NEXT WEEK UNTIL TEMPERATURES WARM ABOVE FREEZING.
STRONG WINDS WILL BE POSSIBLE IN AREAS ALONG AND WEST OF THE
LARAMIE RANGE ON MONDAY AND TUESDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...WIND CHILL WARNING UNTIL 9 AM MST SATURDAY FOR WYZ105-115.

NE...WIND CHILL ADVISORY UNTIL 9 AM MST SATURDAY FOR NEZ002-003-
     019>021-054-055-095-096.

&&

$$

SHORT TERM...RJM
LONG TERM...RE
AVIATION...JAMSKI
FIRE WEATHER...RJM