Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 012222
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
422 PM MDT MON SEP 1 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 422 PM MDT MON SEP 1 2014

MADE NO CHANGES TO THE EARLIER FORECAST UPDATE FOR THE NEXT 12HRS
OTHER THAN TO BUMP UP MAX TEMPS A FEW DEGREES ACROSS THE PLAINS.
ISOLATED TO SCATTERED SHOWERS AND STORMS DEVELOPED MAINLY ALONG
THE COLD FRONT AND PINE RIDGE EARLIER THIS AFTERNOON...WITH THE
STRONGEST ACTIVITY CURRENTLY PUSHING EAST-NORTHEAST OUT OF THE
CWA. A FEW STORMS THAT DEVELOPED OVER THE BIG HORNS ARE NOW RACING
SOUTHEAST TOWARD THE CWA...WITH OTHER WEAKER SHOWERS MOVING OFF
THE LARAMIE RANGE AND OVER THE WYO/NEB PLAINS. DRIER AIR
CONTINUING TO MOVE IN FROM THE WEST WILL LIMIT OVERALL
INSTABILITY SO EXPECT THIS ACTIVITY TO REMAIN ON THE WEAKER SIDE.
THE EXCEPTION MAY BE IN THE SOUTHERN PANHANDLE WHERE DEW POINTS
REMAIN IN THE MID 40S WITHIN AN ENVIRONMENT THAT HAS NOT QUITE
BEEN WORKED OVER YET. SO COULD STILL SEE GUSTY WINDS FROM MORE
ROBUST CONVECTION THAT SHOULD DEVELOP HERE OVER THE NEXT FEW
HOURS.

THE SHORTWAVE WILL SHIFT EAST OF THE AREA LATE THIS EVENING WITH
THE UPPER LEVEL JET LIFTING TO THE NORTH. NAM FORECAST SOUNDINGS
STILL HINT AT THE POSSIBILITY OF PATCHY STRATUS TONIGHT MAINLY FOR
THE LOW RIVER VALLEYS IN THE PANHANDLE SO WILL KEEP SOME CLOUDS IN
THE FORECAST FOR THESE AREAS TONIGHT. OTHERWISE...MUCH DRIER AND
WARMER AIR WILL ADVECT INTO THE CWA AS THE JET LIFTS NORTH AND AN
UPPER LEVEL RIDGE BUILDS OVERHEAD FOR THE NEXT COUPLE OF DAYS.
TUESDAY AND WEDNESDAY LOOK TO BE MOSTLY SUNNY...BREEZY...AND DRY
ACROSS THE FORECAST AREA...WITH THE MAIN CONCERN TRANSITIONING TO
FIRE WEATHER. WENT AHEAD AND UPGRADED THE FIRE WEATHER WATCH TO A
RED FLAG WARNING FOR ZONES 301...LOWER ELEVATIONS OF
302...304...AND 309. AFTER FURTHER REVIEW...LEFT 303 AND 308 OUT
OF THE WARNING AS FUELS HAVE BEEN DEEMED NON-SUPPORTIVE FOR LARGE
FIRE GROWTH. HUMIDITIES ACROSS MUCH OF THE CWA WILL DROP INTO THE
TEENS WITH GUSTS OF 30 TO 40 MPH EXPECTED ALONG AND WEST OF THE
LARAMIE RANGE. FURTHER EAST...FORECAST SOUNDINGS SHOW THAT DEEP
MIXING WITHIN THE BOUNDARY LAYER WILL BE DELAYED TO THE LATER
AFTERNOON SO WINDS SHOULD BE WEAKER WITH GUSTS OF 20 TO 25 MPH AT
TIMES IN THE LATER AFTERNOON. SOUNDINGS SHOW THAT WEDNESDAY WILL
SEE A DEEPER BOUNDARY LAYER OVER THE CWA FOR MOST OF THE DAY...SO
MORE WIDESPREAD GUSTY WINDS AND DRY HUMIDITIES ARE ANTICIPATED
WITH AN EXPANSION OF THE RED FLAG WARNING QUITE POSSIBLE. WILL LET
LATER SHIFTS REFINE TIMING AND LOCATION OF POTENTIAL CRITICAL
CONDITIONS FOR WEDNESDAY. TEMPERATURES WILL WARM BACK TO ABOVE
NORMAL READINGS FOR THIS TIME OF YEAR ON WEDNESDAY.

.LONG TERM...(THURSDAY THROUGH SUNDAY)
ISSUED AT 422 PM MDT MON SEP 1 2014

FRONTAL PASSAGE IS STILL PROGGED FOR THURS MORNING WITH A 15-20
DEGREE DROP IN TEMPS ON THURS COMPARED TO WED.  EAST TO
SOUTHEASTERLY SFC WINDS DEVELOP BY THURS NIGHT AND COMBINED WITH
INCREASING LARGE SCALE ASCENT/ISENTROPIC LIFT...SHOWERS COULD
DEVELOP ACROSS THE CWA.  THE ECMWF CONTINUES THE TREND FROM
YESTERDAYS MODEL SOLN OF BEING MORE AGGRESSIVE ON QPF FOR THURS
NIGHT...ESPECIALLY OVER THE PANHANDLE.  THE GFS AND CANADIAN ARE
QUITE A BIT DRIER SO KEPT POPS IN THE SLIGHT CHANCE CATEGORY FOR
NOW.  SFC HIGH REMAINS ANCHORED OVER THE NORTHERN PLAINS THROUGH AT
LEAST SAT SO LLVL UPSLOPE WILL CONTINUE TO THE EAST OF THE LARAMIE
RANGE...KEEPING TEMPS SLIGHTLY BELOW NORMAL.  WEAK SHORTWAVES WILL
MOVE THROUGH THE FLOW...HOWEVER TIMING IS UNCERTAIN AT THIS POINT.
UNTIL THE MODELS COME INTO BETTER AGREEMENT ON THE LOCATION OF BEST
FORCING AND QPF...IT IS BEST TO KEEP POPS IN THE 20-30 PERCENT RANGE
FOR FRI AND SAT.  IT SHOULD BE NOTED THAT NONE OF THE LONG RANGE
MODELS INDICATE A SUBSTANTIAL AMOUNT OF PRECIP FOR FRI-SAT...ONLY A
FEW TENTHS.  IT DOES APPEAR THAT THE AIRMASS WILL BE MORE UNSTABLE
OVER SOUTHEAST WY...SO BEST CHANCE OF THUNDER WILL BE THERE.
SOUTHWESTERLY FLOW ALOFT STRENGTHENS BY SUN AND WITH A LEE TROUGH
DEVELOPING OVER THE PLAINS...SLIGHT WARMING WITH ENSUE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY MORNING)
ISSUED AT 1228 PM MDT MON SEP 1 2014

VFR CONDITIONS THROUGH THE TAF PERIOD. THE BEST CHANCE OF
AFTERNOON STORMS WILL BE ACROSS THE NEBRASKA
PANHANDLE...PARTICULARLY THE NORTHERN HALF AT CDR AND AIA. BRIEF
HEAVY RAIN AND GUSTY WINDS WILL BE THE MAIN THREAT WITH THE
THUNDERSTORMS. SHOWER ACTIVITY SHOULD WIND DOWN SHORTLY AFTER
SUNSET. BREEZY WEST WINDS WILL DEVELOP THIS AFTERNOON OVER
SOUTHEAST WY WITH GUSTS TO 25-30 KTS COMMON.

&&

.FIRE WEATHER...
ISSUED AT 422 PM MDT MON SEP 1 2014

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE FOR
AREAS ALONG AND EAST OF THE LARAMIE RANGE THROUGH THIS EVENING.
MUCH DRIER CONDITIONS WILL SETTLE IN FOR TUESDAY AND WEDNESDAY
ACROSS THE DISTRICT...WITH WINDY CONDITIONS EXPECTED TO CONTINUE
IN AREAS ALONG AND WEST OF THE LARAMIE RANGE DURING THE AFTERNOON
HOURS. CRITICAL FIRE WEATHER CONDITIONS ARE LIKELY FOR LOWER
ELEVATIONS ALONG AND WEST OF THE LARAMIE RANGE AS A RESULT...WITH
FUELS SUPPORTIVE OF LARGE FIRE GROWTH IN ZONES
301...302...304...AND 309. THEREFORE...UPGRADED THE FIRE WATCH TO
A RED FLAG WARNING FOR THESE ZONES STARTING NOON ON TUESDAY AND
CONTINUING THROUGH 7 PM. CRITICAL FIRE WEATHER CONDITIONS ARE
POSSIBLE AS WELL ON WEDNESDAY FOR THESE SAME AREAS....AND COULD
ALSO EXTEND FURTHER EAST INTO THE EASTERN WYOMING PLAINS.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING FROM NOON TO 7 PM MDT TUESDAY FOR WYZ301-302-
     304-309.

NE...NONE.
&&

$$

SHORT TERM...RJM
LONG TERM...FINCH
AVIATION...FINCH
FIRE WEATHER...RJM





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