Issued by NWS Cheyenne, WY
000
FXUS65 KCYS 212011
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
211 PM MDT TUE OCT 21 2008
.SHORT TERM...TONIGHT THROUGH THURSDAYS...
VIGOROUS UPPER SHORTWAVE CONTINUES TO BE DRIVEN SOUTHEAST THROUGH
THE CWA BY A 135KT H3 JET STREAK EXTENDING FROM BRITISH COLUMBIA
TO NORTHERN UTAH ATTM. AS OF 19Z...SURFACE COLD FRONT HAD JUST
PUSHED THROUGH ALLIANCE...SCOTTSBLUFF...AND WHEATLAND. THIS FRONT
WILL CONTINUE SOUTH CLEARING THE AREA BY 4 OR 5 PM. A BIT MORE
PREFRONTAL CONVECTION THAN EARLIER ANTICIPATED WITH KCYS CARRYING
-TSRA FOR A BRIEF TIME THIS AFTERNOON. THE RAIN/SNOW LINE HAS
TRAILED THE FRONT BY ABOUT 100 MILES OR SO...AND HAS MADE IT
THROUGH KCPR AT AROUND 1 PM. EXPECT THE RAIN/SNOW LINE TO SHIFT
SOUTH SLOWLY THROUGH THE REMAINDER OF THE DAY. INCREASED
PRECIPITATION CHANCES AS IT LOOKS LIKE THE MAJORITY OF THE AREA
WILL AT LEAST GET SOME PRECIPITATION ALONG THE FRONT. SNOW AMOUNTS
STILL LOOK ON TRACK WITH GENERALLY 2 TO 5 INCHES EXPECTED ABOVE
8000 FEET...AND AN INCH OR LESS ANTICIPATED OUT ON THE PLAINS.
SOME NORTH FACING SLOPES OF THE NORTHERN LARAMIE RANGE AND
SNOWIES/SIERRA MADRES MAY RECEIVE LOCALLY GREATER AMOUNTS. THE
NEXT CONCERN FROM THIS SYSTEM WILL BE THE WINDS. SO FAR TODAY...
SURFACE WINDS HAVE REMAINED BELOW ANY HILITE CRITERIA. HOWEVER...
THIS WILL CHANGE AS THE WHOLE SYSTEM AMPLIFIES...TIGHTENING THE
SURFACE PRESSURE GRADIENT BETWEEN THE UPSTREAM SURFACE HIGH...AND
THE DEEPENING SURFACE LOW. AS A RESULT...HAVE ISSUED A WIND
ADVISORY TONIGHT THROUGH TOMORROW FOR THE MAJORITY OF THE NEBRASKA
PANHANDLE...WITH THE EXCEPTION OF CHEYENNE/MORRILL COUNTIES WHERE
A HIGH WIND WARNING HAS BEEN HOISTED. DO NOT THINK THAT
CHEYENNE/MORRILL COUNTIES WILL HIT CRITERIA UNTIL TUESDAY...HOWEVER
OPTED TO KEEP IT SIMPLE WITH POST-FRONTAL ADVISORY WINDS A GOOD
BET OVERNIGHT. PRECIPITATION CHANCES WILL DROP OFF LATE TONIGHT
AND DURING THE DAY ON WEDNESDAY. IN FACT...FOR WEDNESDAY AFTERNOON
AND NIGHT...THE ONLY PRECIPITATION CHANCES WILL BE IN THE FAR
EAST. COOLED TEMPERATURES SOME TOMORROW IN STRONG CAA BRINGING IN
-9 TO -10C AIR AT H7. TEMPERATURES WILL MODERATE ON THURSDAY...
BENEATH CLEARING SKIES.
.LONG TERM...THURSDAY NIGHT THROUGH MONDAY...
CUTOFF LOW WILL MOVE EAST AWAY FROM THE FORECAST AREA THU NIGHT.
NORTHWESTERLY FLOW ALOFT FRI THROUGH MON WILL BACK TO MORE WESTERLY
TUE AHEAD OF AN UPPER RIDGE APPROACHING FROM THE WEST. WEAK SURFACE
BASED LEESIDE TROUGHING IS PROGGED FOR THU NIGHT AND FRI. FRI WILL
BE DRY AND NOT AS COOL AS THE DOWNSLOPE FLOW BOOSTS TEMPERATURES. A
WEAK BACKDOOR TYPE PACIFIC COOL FRONT WILL MOVE THROUGH THE AREA
LATE SATURDAY...BUT MOISTURE AND LIFTING DYNAMICS ARE LACKING. SAT
WILL BE A FEW DEGREES WARMER AHEAD OF THE FRONT...THEN SUNDAY WILL
BE A FEW DEGREES COOLER BEHIND THE FRONT. BOTH SAT AND SUN WILL BE
DRY WITH JUST SOME MID AND HIGH LEVEL MOISTURE AROUND. MON WILL BE
DRY AND A FEW DEGREES WARMER AS HEIGHTS AND THICKNESS VALUES
INCREASE UNDER A TRANQUIL SURFACE PATTERN. WEAK LEESIDE TROUGHING
WILL KEEP TUE DRY WITH TEMPERATURES A BIG ABOVE NORMAL.
&&
.AVIATION...
STRONG SURFACE COLD FRONT WILL CONTINUE TO PUSH SOUTH MAKING IT
THROUGH AREA TERMINALS BY THIS EVENING. STRONG NORTHERLY WINDS
BEHIND THE FRONT WILL GUST TO 25 TO 35 KNOTS AT TIMES. RAIN WILL
TRANSITION TO SNOW THIS AFTERNOON AND THIS EVENING AS TEMPERATURES
COOL. MVFR/IFR CIGS WILL OCCUR IN -RA/-SN SHOWERS OVERNIGHT. SNOW
CHANCES WILL WANE FROM WEST TO EAST DURING THE DAY ON WEDNESDAY.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...HIGH WIND WARNING FROM 6 PM TUESDAY TO 6 PM WEDNESDAY FOR NEZ021-
NEZ055.
WIND ADVISORY FROM 6 PM TUESDAY TO 6 PM WEDNESDAY FOR NEZ001-
NEZ002-NEZ003-NEZ019-NEZ020-NEZ054.
&&
$$
SHORT TERM/AVIATION...HAHN
LONG TERM...JR
