Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 260838
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
238 AM MDT SAT JUL 26 2014

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 235 AM MDT SAT JUL 26 2014

TODAY...BY THIS AFTERNOON...NAM SHOWS A LOW LEVEL CONVERGENCE
BOUNDARY SETTING UP FROM NEAR RAWLINS TO CHEYENNE. LOOKS LIKE ENOUGH
CONVERGENCE ALONG THE BOUNDARY TO SPARK ISOLATED AFTERNOON
THUNDERSTORMS FROM RAWLINS TO CHEYENNE...WITH GREATEST AREAL
COVERAGE OVER THE SOUTHERN LARAMIE RANGE.

TONIGHT...STORMS WILL DECREASE QUICKLY THIS EVENING WITH LOSS OF
DAYTIME HEATING AND AS COOLER AIR BUILDS SOUTHWARD.

SUNDAY...COMBINATION OF RIDGING ALOFT STRENGTHENING ALONG WITH THE
LOW LEVELS BECOMING MORE STABLE...WILL PRODUCE A DRY DAY ASIDE FROM
PERHAPS AN ISOLATED AFTERNOON THUNDERSTORM OVER OUR SOUTHERN
MOUNTAINS. COOLER DAY WITH THICKNESS FALLS AND UPSLOPE EAST WINDS.

SUNDAY NIGHT...ANOTHER COOL AND DRY OVERNIGHT PERIOD WITH LIGHT
SOUTHEAST WINDS.

MONDAY...CONTINUED RELATIVELY COOL FOR LATE JULY PER THICKNESS
TRENDS. LOOKS LIKE ENOUGH LOW AND MID LEVEL MOISTURE RETURN TO
PRODUCE ISOLATED LATE DAY THUNDERSTORMS ALONG AND WEST OF INTERSTATE
25...DRY ELSEWHERE.

.LONG TERM...(TUESDAY THROUGH FRIDAY)
ISSUED AT 235 AM MDT SAT JUL 26 2014

MEDIUM RANGE MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A LARGE SCALE
UPPER RIDGE ENCOMPASSING MUCH OF THE WESTERN US THROUGH THE EXTENDED
PERIOD. THIS FEATURE WILL DRIFT SLOWLY EASTWARD WITH TIME...BUT THE
MAIN RIDGE AXIS SHOULD STAY WEST OF THE CWA THROUGH FRI. THIS KEEPS
ACTIVE NORTHWEST FLOW ALOFT INTACT OVER THE CENTRAL ROCKIES THROUGH
MOST OF THE NEXT WEEK...CONTRIBUTING TO FREQUENT CONVECTIVE CHANCES
AND SEASONABLE TEMPERATURES. BEST CHANCE FOR WIDESPREAD PCPN APPEARS
TO BE FROM TUE AFTN THROUGH WED WHEN BOTH THE GFS AND ECMWF BRING A
SUBSTANTIAL WAVE OF 700-300 MILLIBAR MOISTURE ALONG THE EDGE OF THE
RIDGE. THIS OCCURS ALONG WITH THE PASSAGE OF A LLVL COLD FRONT WHICH
ENHANCES MOIST LLVL UPSLOPE OVER THE PLAINS. CANNOT RULE OUT MORE OF
A PROLONGED/WIDESPREAD PCPN EVENT HERE WITH MANY LOCATIONS SEEING A
DECENT AMOUNT OF RAINFALL. MIDLVL SUBSIDENCE STARTS TO SPREAD INTO
THE AREA LATE IN THE WEEK. HOWEVER...LLVL UPSLOPE PERSISTS AND THE
MODELS DO HANG ON TO AVAILABLE MID AND HIGH LEVEL MOISTURE. OPTED TO
GO WITH ISOLATED POPS ON THU/FRI AFTN AND EVE. OVERALL TEMPERATURES
THIS PERIOD SHOULD BE RIGHT AROUND SEASONABLE NORMS. MAIN CHALLENGE
WILL BE HIGHS WED WITH THE ENHANCED LIKELIHOOD OF PLENTY OF CLOUDS
AND POSSIBLE PCPN. TRENDED A FEW DEGREES BELOW CONSENSUS MOS FOR THE
HIGH PLAINS GIVEN HIGH CONFIDENCE IN PERSISTENT LLVL UPSLOPE PLAYING
A ROLE HERE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1118 PM MDT FRI JUL 25 2014

VFR CONDITIONS ARE EXPECTED OVERNIGHT WITH WEST-TO-SOUTHWEST WINDS
IN PLACE ACROSS THE AREA. OVERALL IMPACTS TO AVIATION INTERESTS WILL
BE MINIMAL OVER THE NEXT 24 HOURS. SHOWERS AND THUNDERSTORMS WILL BE
POSSIBLE AFTER 20Z SAT...WITH THE GREATEST COVERAGE EXPECTED ALONG
THE LARAMIE RANGE AT KCYS AND KLAR. BRIEF MVFR CONDITIONS AND GUSTY
OR ERRATIC WIND GUSTS CAN BE EXPECTED WITH THAT ACTIVITY THROUGH THE
EARLY EVENING HOURS.

&&

.FIRE WEATHER...
ISSUED AT 235 AM MDT SAT JUL 26 2014

HUMIDITIES WILL RANGE FROM 10 TO 15 PERCENT THIS AFTERNOON FROM
RAWLINS TO DOUGLAS...THOUGH FORTUNATELY WITH MINIMAL WINDS.
HUMIDITIES WILL INCREASE SUNDAY AND MONDAY LESSENING THE FIRE
WEATHER CONCERNS.

&&

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

$$

SHORT TERM...RUBIN
LONG TERM...HAMMER
AVIATION...HAMMER
FIRE WEATHER...RUBIN






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