Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 191724
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1124 AM MDT SAT APR 19 2014

.UPDATE...
ISSUED AT 1046 AM MDT SAT APR 19 2014

FORECAST PRETTY WELL ON TRACK FOR TODAY. ONLY CONCERN IS THICK
CIRRUS OVER MOST OF THE SOUTHEAST FORECAST INHIBITING
THUNDERSTORM CHANCES TODAY. COOL NORTHEAST UPSLOPE WILL NOT HELP
WITH SURFACE BASED INSTABILITY EAST OF THE LARAMIE RANGE AND WINDS
WILL BE SLOWER TO COME AROUND TO THE SOUTH THAN MODELS EARLIER
PROJECTED. NAM AND GFS HAS BACKED OFF ON THE SLIGHTLY NEGATIVE
LIFTED INDEX AND LOOKING AT MODEL SOUNDINGS...STEEP SURFACE BASED
LAPSE RATES WILL BE TOUGH TO COME BY EAST OF THE LARAMIE RANGE.
REMOVED THUNDERSTORM MENTION EAST OF THE LARAMIE RANGE FOR
TODAY...BUT KEPT IT GOING TO THE WEST WHERE MORNING SUNSHINE WILL
PRODUCE THOSE STEEPER LAPSE RATES. CAN NOT COMPLETELY RULE OUT
SOME ELEVATED CONVECTION WITH LIGHTNING EVEN EAST OF THE LARAMIE
RANGE AS THE NORTHERN FRINGES OF AN UPPER LEVEL DISTURBANCE WILL
IMPACT THE SOUTHERN CWA...BUT WITH ONLY WEAK FORCING...LIGHTNING
CHANCES ARE REMOTE AT BEST. GUSTY WINDS AND SMALL GRAUPLE
CERTAINLY A POSSIBILITY WEST OF THE LARAMIE RANGE WITH ANY
STRONGER CONVECTION...BUT SEVERE THUNDERSTORMS NOT LIKELY.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)

ISSUED AT 256 AM MDT SAT APR 19 2014

AN UPPER LEVEL DISTURBANCE WILL MOVE OVER THE FORECAST AREA THIS
AFTERNOON...WITH SURFACE WINDS VEERING TO THE SOUTHEAST ACROSS THE
PLAINS AND INCREASING IN STRENGTH. DEW POINTS WILL INCREASE INTO THE
UPPER 30S TO LOW 40S ACROSS THE PLAINS IN THIS MOISTURE ADVECTION
PATTERN WITH WEAK INSTABILITY PROGGED FOR THE AFTERNOON. HIGH CLOUD
COVER WILL KEEP TEMPS ON THE COOL SIDE AND THUS INSTABILITY WILL
BE LOW...BUT THE COMBO OF UPPER SUPPORT AND WEAK INSTABILITY WILL
SUPPORT A GOOD CHANCE FOR RAIN SHOWERS WITH ISOLATED THUNDERSTORMS
THIS AFTERNOON ESPECIALLY FOR THE MOUNTAINS AND NEARBY PLAINS.
LOOKS AS THOUGH AREAS FROM THE LARAMIE RANGE TO THE I-25 CORRIDOR
COULD SEE THE BEST CHANCE FOR STORMS OUTSIDE THE MOUNTAINS WHERE
NAM PAINTS INSTABILITY AS HIGH AS 200 J/KG WITHIN THE
BEST...ALBEIT RELATIVELY WEAK...MOISTURE CONVERGENCE ZONE. SHOULD
SEE WETTING RAINS WITH THIS ACTIVITY AS PRECIPITABLE WATER VALUES
WILL INCREASE TO BETWEEN ONE HALF AND THREE QUARTERS OF AN INCH
THROUGH THE AFTERNOON. CONVECTION WILL DIMINISH THROUGH THE
EVENING AS THE UPPER WAVE WEAKENS AND MOVES EAST.

FOR SUNDAY...A COLD FRONT ASSOCIATED WITH A SHORTWAVE MOVING ACROSS
US/CANADIAN BORDER WILL DROP SOUTH ACROSS THE EASTERN PLAINS IN THE
AFTERNOON. TEMPS WILL WARM INTO THE UPPER 60S TO UPPER 70S IN THE
LOWER ELEVATIONS AHEAD OF THE FRONT...WITH LI`S DROPPING TO AROUND
ZERO. TIMING OF THE FRONT COULD FAVOR DEVELOPMENT OF AFTERNOON
SHOWERS AND A FEW WEAK THUNDERSTORMS...ESPECIALLY ALONG THE LARAMIE
RANGE AND CHEYENNE RIDGE WHERE LLVL FORCING AND INSTABILITY ARE
MAXIMIZED. A WEAK DISTURBANCE MOVING OVERHEAD FROM THE WEST WILL
TRIGGER A FEW TSTORMS OVER THE MOUNTAINS IN THE AFTERNOON AS WELL.

SFC HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT FOR MONDAY WITH MAX
TEMPS EXPECTED TO BE ABOUT 5F COOLER. SFC WINDS WILL VEER BACK TO
THE SOUTH-SOUTHEAST IN THE AFTERNOON AND SO MAY SEE A FEW RAIN
SHOWERS DEVELOP WITHIN THE CONVERGENCE ZONE VCTY LARAMIE RANGE.
COOLER SFC TEMPS AND WAA ALOFT DUE TO A BUILDING UPPER RIDGE FROM
THE WEST WILL MINIMIZE INSTABILITY AND THUS TSTORM CHANCES.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 256 AM MDT SAT APR 19 2014

PRETTY STRONG LOW PRESSURE SYSTEM IN THE EXTENDED EXPECTED TO
BRING VERY STRONG WINDS AND SOME PRECIP CHANCES TO THE CWFA. THESE
ARE THE CHALLENGES IN THE LONG TERM.

FOR MONDAY NIGHT INTO TUESDAY...UPPER LEVEL RIDGING BUILDS INTO
THE AREA WITH 700MB TEMPERATURES CLIMBING FROM +4C MONDAY
AFTERNOON UP TO +8C TUESDAY AFTERNOON. LOOKS LIKE A PRETTY WARM
DAY TUESDAY WITH 80S RETURNING TO THE PANHANDLE AND UPPER 60S/LOW
70S FOR AREAS WEST OF THE LARAMIE RANGE.

A STRONG UPPER LEVEL LOW PRESSURE SYSTEM MOVES INTO SOUTHERN
NEVADA TO NORTHERN UTAH TUESDAY AFTERNOON...THEN INTO WESTERN
WYOMING TUESDAY NIGHT. AHEAD OF THIS LOW...700MB WINDS BECOME
QUITE STRONG WITH THE GFS SHOW 50KTS AT 700MBS WEDNESDAY MORNING.
700MB CRAIG TO CASPER HEIGHT GRADIENT AT 60MTRS TUESDAY NIGHT AND
INCREASES TO 70MTRS DURING THE MORNING WEDNESDAY. WILL NEED TO
MONITOR THIS FOR POSSIBLE WIND HEADLINES DURING THIS
TIME FRAME...AT LEAST FOR OUR WIND PRONE AREAS.

COLD FRONT ASSOCIATED WITH THIS LOW LOOKS TO MOVE INTO THE AREA
WEDNESDAY AFTERNOON WITH 700MB TEMPERATURES FALLING TO -6C ACROSS
CARBON COUNTY WEDNESDAY NIGHT. FOR NOW...BEST CHANCES FOR PRECIP
LOOK TO BE THE MOUNTAINS AND AREAS WEST OF THE LARAMIE RANGE.
AREAS EAST WILL BE IMPACTED BY DOWNSLOPING WINDS...SO KEPT THESE
AREAS DRY.

CONCERNS FOR WIND HEADLINES SHIFTS EAST INTO THE PANHANDLE
WEDNESDAY NIGHT AS GFS 850MB WINDS INCREASE TO 40KTS. SHOULD BE AT
LEAST WIND ADVISORY CRITERIA OUT THERE...CONTINUING INTO THURSDAY
AFTERNOON.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY MORNING)
ISSUED AT 1124 AM MDT SAT APR 19 2014

PLENTY OF MID AND HIGH CLOUDS WILL MOVE OVER THE AERODROMES THIS
AFTERNOON THEN SOME CLEARING EXPECTED TONIGHT.  MAINLY VFR THROUGH
SUNDAY BUT SOME PDS OF MVFR VSBYS POSSIBLE WITH ANY SHOWERS THAT
MOVE ACROSS THE AREA THIS AFTERNOON INTO THIS EVENING.

&&

.FIRE WEATHER...
ISSUED AT 256 AM MDT SAT APR 19 2014

TEMPERATURES WILL BE COOLER TODAY WITH HIGHER HUMIDITIES AND LESS
WIND. CHANCES FOR WETTING RAINS AND ISOLATED THUNDERSTORMS WILL
INCREASE THIS AFTERNOON AND WILL CONTINUE THROUGH THE EVENING AS A
WEATHER DISTURBANCE TRACKS ACROSS THE REGION. ANOTHER COLD FRONT
WILL DROP SOUTH ACROSS THE AREA ON SUNDAY AND WILL BRING A SLIGHT
CHANCE FOR AFTERNOON SHOWERS AND THUNDERSTORMS...ESPECIALLY FOR THE
MOUNTAINS AND AREAS NEAR THE COLORADO BORDER. AFTER A COOLER DAY
MONDAY...EXPECT WARMER AND DRIER CONDITIONS FOR TUESDAY WITH WINDY
CONDITIONS POSSIBLE FOR WEDNESDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&

$$

UPDATE...SML
SHORT TERM...RJM
LONG TERM...CLAYCOMB
AVIATION...RE
FIRE WEATHER...RJM





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