Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 271731
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1131 AM MDT MON JUL 27 2015

.UPDATE...
ISSUED AT 1107 AM MDT MON JUL 27 2015

EXTREME RED FLAG CONDITIONS STILL ON TRACK FOR THIS
AFTERNOON...ESPECIALLY TO THE WEST OF THE LARAMIE RANGE. FUELS IN
FIRE WEATHER ZONE 306 (UPPER NORTH PLATTE RIVER BASIN) HAVE BECOME
CRITICAL AND THIS ZONE HAS BEEN ADDED TO THE RED FLAG WARNING.
RH VALUES AND WINDS IN ZONE 310 WILL BE MORE MARGINAL NEAR THE SFC
TROUGH...HOWEVER WILL KEEP THEM IN THE WARNING. THE THREAT FOR A
STRONG TO MARGINALLY SVR STORM IS STILL MOSTLY CONFINED TO THE
FAR EASTERN ZONES WHERE THE RUC SHOWS CAPE VALUES OF AROUND 1250
J/KG BY LATE AFTN.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY NIGHT)
ISSUED AT 145 AM MDT MON JUL 27 2015

ONE MORE HOT DAY FOR SOUTHEAST WYOMING AND THE NEBRASKA PANHANDLE
TODAY...THEN COOLER READINGS FOR THE REST OF THE WORK WEEK
FOLLOWING THE PASSAGE OF A COLD FRONT TONIGHT. GUSTY WEST TO
SOUTHWEST WINDS WILL ACCOMPANY THE VERY WARM AIR TODAY. IN FACT
WIND SPEEDS WILL APPROACH HIGH WIND WARNING CRITERIA ACROSS MUCH
OF CARBON COUNTY AND INTO WESTERN CONVERSE COUNTY THIS AFTERNOON
WITH WIND GUSTS TO 50 MPH OR GREATER. THE COMBINATION OF STRONG
WINDS AND WARM TEMPERATURES WILL PRODUCE VERY LOW HUMIDITY
VALUES...AND WITH THAT COMES AN EXTREME RISK FOR RAPIDLY SPREADING
WILDFIRE. A RED FLAG WARNING IS IN EFFECT FOR MUCH OF SOUTHEAST
WYOMING DUE TO THESE HAZARDOUS CONDITIONS.

SWITCHING FROM FIRE DANGER IN SOUTHEAST WYOMING TO SEVERE
THUNDERSTORM CHANCES INTO THE NEBRASKA PANHANDLE. HOT AND HUMID
AIR INTO THE PANHANDLE WILL SET THE STAGE FOR THUNDERSTORMS THIS
AFTERNOON. THERE IS SOME UNCERTAINTY AS TO WHERE THUNDERSTORMS
WILL ACTUALLY DEVELOP BUT A PUNCH OF DRY AIR AHEAD OF AN UPPER
LEVEL TROUGH OVER THE NORTHERN ROCKIES WILL LIKELY BE THE TRIGGER
WHICH SETS OFF THUNDERSTORMS TODAY. THUNDERSTORMS COULD DEVELOP
ANYWHERE FROM ALONG THE NEBRASKA/WYOMING BORDER TO JUST EAST OF
THE FORECAST AREA THIS AFTERNOON...BUT THAT WILL DEPEND ON WHERE
A DEVELOPING DRY LINE/STRONGEST LOW LEVEL CONVERGENCE OCCURS.
BEST GUESS AT THIS TIME IS FOR THUNDERSTORM DEVELOPMENT IN THE
WESTERN NEBRASKA PANHANDLE. THUNDERSTORMS THAT DEVELOP WILL HAVE A
HIGH LIKELIHOOD OF QUICKLY BECOMING SEVERE. 00Z NAM SHOWING
UPWARDS OF 4000J/KG SB CAPE AT 21Z TODAY FROM AROUND CHADRON TO
SIDNEY. SHOULD THIS BE THE CASE THEN LARGE HAIL AND DAMAGING
WINDS WILL BE POSSIBLE. THUNDERSTORMS THAT DEVELOP WILL QUICKLY
MOVE EAST AND OUT OF THE FORECAST AREA BY EARLY EVENING.

COOLER DRIER AIR WILL SETTLE INTO THE REGION TUESDAY AND WEDNESDAY
WITH VIRTUALLY NO CHANCE FOR PRECIPITATION. TEMPERATURES TUESDAY
WILL BE CLOSER TO NORMAL WITH HIGHS MAINLY IN THE 80S ACROSS THE
PLAINS WITH 70S INTO THE HIGHER ELEVATIONS OF SOUTHEAST WYOMING
OUTSIDE OF THE MOUNTAINS. TUESDAY WILL BE BREEZY TO WINDY ACROSS
THE FORECAST AREA WITH GUSTY WEST TO NORTHWEST WINDS IN PLACE.
RELATIVELY LIGHT WINDS WILL BE IN PLACE WEDNESDAY AND SLIGHTLY
WARMER TEMPERATURES WITH HIGHS MAINLY IN THE 80S.

.LONG TERM...(THURSDAY THROUGH SUNDAY)
ISSUED AT 300 AM MDT MON JUL 27 2015

THE UPPER RIDGE CENTER OVER THE SOUTHERN HIGH PLAINS WILL
RETROGRADE WEST OVER THE FOUR CORNERS BY THIS WEEKEND. THIS
PATTERN WILL SUPPORT A WEST TO NORTHWEST FLOW ALOFT OVER THE CWA.
PRECIPITATION CHANCES WILL BE ALMOST NON-EXISTENT. THE EXCEPTIONS
MAY BE ISOLATED TSTORMS OVER THE FAR EASTERN ZONES LATE THURSDAY
WITH WEAK LOW LEVEL CONVERGENCE...AND OVER THE SOUTHEAST WY
MOUNTAINS SUNDAY AFTERNOON DUE TO SOME SUBTROPICAL MOISTURE AND
OROGRAPHIC LIFT. LIGHT WINDS WILL PREVAIL WITH A WEAK SURFACE
PRESSURE GRADIENT. TEMPERATURES WILL AVERAGE SLIGHT ABOVE SEASONAL
NORMALS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1107 AM MDT MON JUL 27 2015

THE MAIN CONCERN WITH THIS TAF ISSUANCE IS THE POTENTIAL FOR
THUNDERSTORMS THIS AFTERNOON.

LATEST WATER VAPOR LOOP WAS SHOWING THE STRONG UPPER LEVEL TROF
MOVING THROUGH IDAHO. MEANWHILE...THE DRY SLOT WAS STARTING TO
PUSH INTO WESTERN COLORADO. THE SURFACE TROF WAS SITUATED ALONG
THE LEE SIDE OF THE LARAMIE RANGE WITH THE BULK OF THE HIGHER
DEWPOINTS EAST IN THE NEBRASKA PANHANDLE. AS THIS UPPER LEVEL TROF
PUSHES EAST TODAY...THIS SHOULD HELP INITIATE SOME STRONG TO
SEVERE STORMS ALONG THE SURFACE TROF LATE THIS AFTERNOON. AS A
RESULT...THE NEBRASKA TAF SITES HAVE A PRETTY GOOD SHOT OF SEEING
SOME OF THESE STORMS THIS AFTERNOON. THE MAIN CONCERN WITH THESE
THUNDERSTORMS WILL STRONG GUSTY WINDS AND LARGE HAIL. THE UPPER
LEVEL TROF AND ITS ASSOCIATED SURFACE FRONT IS PROGGED TO SHIFT
THROUGH THE WYOMING TAF SITES EARLY THIS EVENING BEFORE 03Z WHILE
THE NEBRASKA TAF SITES SHOULD SEE THIS WIND SHIFT TO THE NORTHWEST BETWEEN
BETWEEN 03Z- 06Z. GUSTY WINDS UP 50 MPH MAY BE POSSIBLE AFTER
THIS FRONT MOVES THROUGH.

&&

.FIRE WEATHER...
ISSUED AT 204 AM MDT MON JUL 27 2015

A RED FLAG WARNING IS IN EFFECT TODAY FOR PORTIONS OF SOUTHEAST
WYOMING WHERE GRASSES AND OTHER QUICK TO DRY VEGETATION IS SUPPORTIVE
OF RAPID FIRE GROWTH. UNSEASONABLY STRONG WEST TO SOUTHWEST WINDS
WILL COMBINE WITH VERY LOW HUMIDITIES TO PRODUCE EXTREME FIRE
CONDITIONS TODAY...PARTICULARLY OVER PORTIONS OF CARBON COUNTY AND
FAR WESTERN CONVERSE COUNTY WHERE WIND GUSTS TO 50 MPH ARE LIKELY.
COOLER TEMPERATURES WILL SPREAD ACROSS THE REGION TUESDAY BUT
GUSTY WEST TO NORTHWEST WINDS AND LOW HUMIDITIES WILL MAKE FOR
MARGINAL FIRE CONDITIONS.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR WYZ301-302-304-
     306-310.

NE...NONE.
&&

$$

UPDATE...ZF
SHORT TERM...SML
LONG TERM...MAJ
AVIATION...REC
FIRE WEATHER...SML/MAJ



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