Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 260450
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1050 PM MDT TUE AUG 25 2015

.UPDATE...
ISSUED AT 841 PM MDT TUE AUG 25 2015

RAISED POPS UP TO 20 PERCENT FOR WIDELY SCATTERED SHOWERS AND A
FEW TSTORMS ALONG AND WEST OF THE LARAMIE RANGE THROUGH LATE THIS
EVENING BEFORE DISSIPATING.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 222 PM MDT TUE AUG 25 2015

BROAD UPPER-LEVEL RIDGING EXTENDS ACROSS THE WESTERN HALF OF THE US
THIS AFTERNOON. THE RESULTING LARGE SCALE SUBSIDENCE IS CONTRIBUTING
TO GENERALLY WARM AND DRY CONDITIONS ACROSS THE CWA. RECENT WATER
VAPOR SATELLITE IMAGERY SHOWS A PLUME OF MONSOONAL MOISTURE LIFTING
NORTH OVER THE FOUR CORNERS REGION ON THE WEST SIDE OF THE RIDGE. SOME
OF THIS MOISTURE WAS ALREADY CREEPING INTO THE SNOWY AND SIERRA MADRE
MTNS AT 20Z...SO WE SHOULD SEE AN INCREASE IN MOUNTAIN CONVECTION AS
WE HEAD INTO THE LATE AFTERNOON/EVENING HOURS. MORE WIDESPREAD SHOWERS
AND THUNDERSTORMS STILL EXPECTED FROM WED AFTN THROUGH THU WITH THE
PASSAGE OF A STRONG PACIFIC COLD FRONT AND VIGOROUS MID-LEVEL SHORT
WAVE TROUGH. NAM/GFS/ECMWF ALL SUGGEST THE GREATEST PRECIP COVERAGE
ALONG AND WEST OF THE LARAMIE RANGE...WITH MAKES SENSE WITH GENERAL
WESTERLY FLOW AND THE TRAJECTORY OF THE BEST H7-H3 MOISTURE. BETTER
CHANCES FOR THE EASTERN PLAINS SHOULD COME AFTER 15Z THU AS MOST OF
THE MID LEVEL ENERGY AND ASSOCIATED MOISTURE PLUME SHIFTS SLOWLY TO
THE EAST. ONE MORE WARM DAY EXPECTED FOR WED PRE-FROPA. MUCH COOLER
FOR THU AS MOST OF THE MODELS SHOW H7 TEMPS PLUNGING FROM +16 C AT
00Z THU...TO BETWEEN +8 AND +10 C BY 18Z THU. INDEED AN IMPRESSIVE
TEMPERATURE SWING FOR A PACIFIC FRONT...ESPECIALLY FOR AUGUST. MAY
NEED TO REVISE TEMPERATURES DOWNWARD IN THE FUTURE IF IT LOOKS LIKE
PRECIP WILL BE HEAVIER OR MORE WIDESPREAD.

.LONG TERM...(THURSDAY THROUGH NEXT TUESDAY)
ISSUED AT 222 PM MDT TUE AUG 25 2015

MEDIUM TO LONG RANGE MODELS ARE CONSISTENT WITH THE PREVIOUS 12Z
AND 00Z RUNS...SHOWING UPPER LEVEL RIDGING BUILDING BACK INTO THE
FRONT RANGE ON FRIDAY. THIS RIDGE WILL GRADUALLY EXTEND EASTWARD
INTO THE GREAT PLAINS...ALLOWING SOUTHWEST FLOW ALOFT TO INCREASE
OVER WYOMING AND NEBRASKA. IT WILL BE WARM ON FRIDAY AND ESPECIALLY
DURING THE WEEKEND WITH HIGHS IN THE 80S TO MID 90S...WARMEST OVER
THE LOWER ELEVATIONS. MODELS ARE NOW SHOWING A BIT MORE MOISTURE
AND INSTABILITY OVER THE REGION AS SOME SUBTROPICAL MOISTURE
GRADUALLY ADVECTS NORTHWARD ON THE WESTERN SIDE OF THE UPPER LEVEL
RIDGE AXIS. THE 12Z ECMWF SHOWS SOME SHORTWAVE ENERGY PUSHING
NORTHEAST OVER THE FORECAST AREA BY EARLY NEXT WEEK...IMPROVING
THUNDERSTORM CHANCES MONDAY AND TUESDAY. EXPECT MOST OF THIS
ACTIVITY TO BE OVER THE MOUNTAINS...ALONG AND WEST OF THE I25
CORRIDOR...BUT A FEW THUNDER SHOWERS MAY PUSH FAR ENOUGH EAST TO
IMPACT WESTERN NEBRASKA AS WELL. INCREASED POP BETWEEN 15 TO 25
PERCENT FOR WIDELY SCATTERED THUNDER ACROSS THE HIGH VALLEYS AND
HIGH PLAINS EAST OF THE LARAMIE RANGE ACROSS SOUTHEAST WYOMING.
DAYTIME TEMPERATURES WILL CONTINUE TO BE ABOVE NORMAL AND IN THE
80S TO LOW 90S ACROSS THE AREA EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1047 PM MDT TUE AUG 25 2015

GETTING SOME LIGHTNING STRIKES JUST NORTH OF KRWL LATE THIS
EVENING. LATEST HRRR FORECAST RADAR SHOWS THIS ACTIVITY
DISSIPATING IN A FEW HOURS. MOISTURE FROM THE 4 CORNERS AREA
FORECAST TO MOVE NORTH INTO SOUTH CENTRAL WYOMING THIS AFTERNOON.
COULD SEE PREDOMINANT SHOWERS AND ISOLATED THUNDERSTORMS AT KRWL
AND KLAR AFTER 20Z OR SO...PERSISTING INTO THE EVENING HOURS.

&&

.FIRE WEATHER...
ISSUED AT 222 PM MDT TUE AUG 25 2015

WARM AND DRY CONDITIONS ARE OCCURRING ACROSS A LARGE PORTION OF THE
AREA THIS AFTERNOON. RELATIVE HUMIDITY VALUES BETWEEN 10 AND 15 PCT
ARE COMMON ACROSS SOUTHEAST WYOMING...BUT LIGHT WINDS TOPPING OUT
AROUND 10 MPH IN THE VEDAUWOO AREA ARE KEEPING CONCERNS MINIMAL.
THERE WILL NOT BE ANY FIRE WEATHER CONCERNS THROUGH THE END OF THE
WORK WEEK AS A COOLER AND MORE MOIST AIR MASS KEEPS HUMIDITIES
ABOVE 20 PCT ALONG WITH A HIGHER PROBABILITY FOR WETTING RAINS. A
WARMING AND DRYING TREND IS EXPECTED THIS WEEKEND ALONG WITH GUSTY
WINDS. NEAR CRITICAL FIRE WEATHER CONDITIONS ARE STILL EXPECTED
FOR SAT AND SUN.

&&

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

$$

UPDATE...MJ
SHORT TERM...CLH
LONG TERM...TJT
AVIATION...GCC
FIRE WEATHER...CLH


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