Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 270255
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
855 PM MDT WED AUG 26 2015

.UPDATE...
ISSUED AT 855 PM MDT WED AUG 26 2015

THUNDERSTORM ACTIVITY IS WANING WITH THE LOST OF SOLAR HEATING BUT
MORE IMPORTANTLY THE STRONGER LIFT AHEAD OF A SHORTWAVE HAS
SHIFTED INTO NORTHEAST WYOMING AND FAR WESTERN SOUTH DAKOTA.
FORECAST LOOKS ON TRACK FOR TONIGHT WITH SOME SHOWER ACTIVITY
THROUGH THE NIGHT. REMOVED THE MENTION OF THUNDERSTORMS THE REST
OF TONIGHT. CAN NOT COMPLETELY RULE OUT A FEW LIGHTNING STRIKES
BUT THEY SHOULD BE FEW AND FAR BETWEEN WITH BETTER CHANCES FOR
THUNDERSTORMS REEMERGING LATER THURSDAY.

&&

.SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT...

BROAD UPPER-LEVEL RIDGING REMAINS INTACT ACROSS MUCH OF THE WESTERN
AND CENTRAL CONUS THIS AFTERNOON. A VIGOROUS MIDLVL SHORTWAVE TROUGH
WAS UNDERCUTTING THE RIDGE...AND LIFTING NORTHEAST ACROSS EASTERN UT
AT 20Z. RECENT WATER VAPOR SATELLITE LOOP SHOWS A PLUME OF MONSOONAL
MOISTURE SPREADING NORTHWARD ACROSS COLORADO AND WYOMING ON THE WEST
SIDE OF THE RIDGE. PLENTIFUL CIRRUS HAS NOT HAD MUCH OF AN IMPACT ON
TEMPERATURES TODAY AS CONTINUED WARM 700 MILLIBAR TEMPS (AROUND +16
C OVER KRIW AT 12Z THIS AM) MANAGED TO YIELD WIDESPREAD 90S OVER THE
EASTERN PLAINS. CHADRON HIT 100 F AT 2 PM DESPITE BEING UNDER A VEIL
OF CIRRUS UNTIL EARLY AFTERNOON. NOW...WE SHIFT OUR FOCUS TO CHANCES
FOR PRECIP ASSOCIATED WITH THE AFOREMENTIONED WAVE AN AN IMPRESSIVE
PACIFIC COLD FRONT. MODELS HAVE BEEN TRENDING MUCH SLOWER WITH THIS
SYSTEM...WHICH MAKES SENSE WITH THE LARGER SCALE PATTERN. THIS WILL
MOST LIKELY DELAY THE ONSET OF MORE WIDESPREAD CONVECTION UNTIL 06Z
OR SO...BUT WE WILL CONTINUE TO SEE ISOLATED SHOWERS/STORMS OUT WEST
THROUGH THE EVENING. GREATEST COVERAGE WILL BE ALONG AND WEST OF THE
LARAMIE RANGE WITH THE BEST MOISTURE/FORCING. ON THU...GFS/NAM/ECMWF
ALL SHOW A SECONDARY FRONTAL SURGE ACROSS EAST CENTRAL WYOMING INTO
THE NORTHERN PANHANDLE...WITH GUSTY NORTHERLY WINDS TO FOLLOW. QPF
SIGNALS ARE FAIRLY STRONG FROM ALL MODELS...SO WENT AHEAD AND BUMPED
POPS UP IN THE REGION OF BEST LLVL CONVERGENCE AND PVA. THERE COULD
BE SOME PATCHY FOG EARLY TOMORROW MORNING OVER THE PLAINS AS WINDS
REMAIN LIGHT AND LLVL MOISTURE INCREASES...BUT BUFKIT SOUNDINGS ARE
NOT IMPRESSIVE ENOUGH TO JUSTIFY MENTIONING IN THE GRIDS ATTM. IT
WILL BE QUITE A BIT COOLER TOMORROW WITH H7 TEMPS FALLING TO 8-10 C
BY 18Z THU. WARMER AND DRIER FOR FRI AS UPPER-LEVEL RIDGING BECOMES
RE-ESTABLISHED.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 300 PM MDT WED AUG 26 2015

MODELS ARE IN GOOD AGREEMENT WITH PREVIOUS MODEL RUNS...SHOWING
UPPER LEVEL RIDGING BUILDING OVER THE FRONT RANGE BY THE WEEKEND.
THIS RIDGE WILL GRADUALLY DRIFT EASTWARD INTO THE GREAT
PLAINS...ALLOWING SOUTHWEST FLOW ALOFT TO INCREASE OVER WYOMING
AND NEBRASKA BY SUNDAY AND EARLY NEXT WEEK. IT WILL BE QUITE WARM
OVER THE WEEKEND AS THE RIDGE AXIS SLOWLY SLIDES EASTWARD...WITH
HIGHS IN THE 80S TO MID 90S...WARMEST OVER THE LOWER ELEVATIONS.
MODELS CONTINUE TO SHOW SOME MOISTURE AND INSTABILITY OVER THE
REGION...MAINLY SOUTHEAST WYOMING BEGINNING ON SUNDAY...AS SOME
SUBTROPICAL MOISTURE ADVECTS NORTHWARD ON THE WESTERN PERIPHERY OF
THE UPPER LEVEL RIDGE AXIS. THE NEW 12Z ECMWF SHOWS THE UPPER
LEVEL RIDGE WEAKENING BY THE MIDDLE PART OF NEXT WEEK...ALLOWING A
GREATER COVERAGE OF SHOWERS AND TSTORMS. EITHER WAY...THE TREND
WILL BE FOR AN INCREASED THREAT OF THUNDER SHOWERS BEGINNING
SUNDAY AND POTENTIALLY LINGERING THROUGH THE MIDDLE OF NEXT WEEK.
HOWEVER...DID NOT INCREASE POP TOO MUCH SINCE THE GREATEST
COVERAGE OF ACTIVITY WILL DEPEND ON THE TIMING OF INDIVIDUAL WEAK
SHORTWAVE ENERGY...WHICH IS VERY DIFFICULT TO DETERMINE 5 DAYS
OUT. ADJUSTED POP AND KEPT VALUES BETWEEN 15 TO 25 PERCENT ACROSS
THE HIGH VALLEYS AND HIGH PLAINS...WITH HIGHER VALUES ACROSS THE
MOUNTAINS. DAYTIME TEMPERATURES WILL CONTINUE TO BE ABOVE NORMAL
AND IN THE 80S TO LOW 90S ACROSS THE AREA THROUGH EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 536 PM MDT WED AUG 26 2015

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE
ACROSS THE AREA EARLY THIS EVENING. VERY HEAVY RAIN AND SMALL
HAIL IS THE MAIN THREAT FROM THESE STORMS...OF COURSE SUDDEN AND
ERRATIC WINDS WILL BE POSSIBLE. SHOWER ACTIVE WILL DIE OFF ACROSS
THE PLAINS BY LATE THIS EVENING BUT SHOWER MAIN CONTINUE ACROSS
CARBON COUNTY IN WYOMING INTO THE LATE NIGHT HOURS.


&&

.FIRE WEATHER...
ISSUED AT 229 PM MDT WED AUG 26 2015

MINIMAL FIRE WEATHER CONCERNS THROUGH THE REMAINDER OF THE WEEK. IT
WAS ANOTHER WARM AND DRY AFTERNOON ACROSS SOUTHEAST WYO AND THE NEB
PANHANDLE WITH TEMPS IN THE 90S AND HUMIDITY VALUES AROUND 10 TO 15
PERCENT. HOWEVER...LIGHT WINDS ARE NOT CAUSING TOO MUCH TROUBLE. AN
UPPER LEVEL DISTURBANCE WILL YIELD COOLER AND UNSETTLED CONDITIONS
FROM LATE TONIGHT THROUGH MUCH OF THURSDAY. NO FIRE WEATHER CONCERNS
WITH HIGHER HUMIDITIES AND A GOOD CHANCE OF WETTING RAIN. THERE WILL
BE A TREND TOWARD WARMER AND DRIER WEATHER INTO THE WEEKEND...GIVING
WAY TO THE POTENTIAL FOR ELEVATED FIRE WEATHER CONDITIONS ON
SAT/SUN.

&&

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

$$

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



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