Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 252058
AFDCYS

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

.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/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/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 18Z TAFS THROUGH WEDNESDAY MORNING)

VFR CONDITIONS WITH LIGHT WINDS CONTINUING THIS AFTERNOON AND INTO
TONIGHT. NO WEATHER IMPACTS TO AVIATION EXPECTED.


&&

.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 WYO...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/DRYING TREND
IS EXPECTED THIS WEEKEND ALONG WITH GUSTY WINDS. NEAR CRITICAL FIRE
WEATHER CONDITIONS ARE STILL EXPECTED FOR SAT/SUN.

&&

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

$$

SHORT TERM...CLH
LONG TERM...TJT
AVIATION...TJT
FIRE WEATHER...CLH



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