Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 031154
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
554 AM MDT MON AUG 3 2015

.SHORT TERM...(TODAY THROUGH TUESDAY NIGHT)
ISSUED AT 221 AM MDT MON AUG 3 2015

FRONTAL BOUNDARY LAYING ALONG THE EAST SLOPES OF THE LARAMIE RANGE
THIS MORNING. WATER VAPOR IMAGERY SHOWING AN UPPER DISTURBANCE
OVER EASTERN UTAH...PULLING MONSOONAL MOISTURE NORTH. DEWPOINTS IN
NORTHWESTERN COLORADO APPROACHING THE MID AND UPPER 50S...WHILE
OUT IN CARBON COUNTY...DEWPOINTS IN THE LOW TO MID 40S ARE BEING
OBSERVED. FORECAST CHALLENGES DEAL WITH TIMING OF MOISTURE
SURGE...THE POSSIBILITY OF DRY THUNDERSTORMS INITIALLY OUT WEST
AND SEVERE THUNDERSTORM POTENTIAL EAST OF THE LARAMIE RANGE THIS
AFTERNOON AND EVENING.

USED THE ECMWF SOLUTION FOR ONSET OF MOISTURE SURGE INTO THE
WESTERN CWFA THIS AFTERNOON. THERE IS A BRIEF DECREASE IN PWATS
OUT NEAR RAWLINS LATE THIS MORNING THROUGH ABOUT 21Z...WHEN PWAT
INCREASES TO NEAR .9 INCHES. CAPE FORECAST FOR 18-21Z SHOWING NEAR
700J/KG FOR RAWLINS...AMPLE FOR ISOLATED DRY THUNDERSTORM
DEVELOPMENT. MAY NOT BE LONG ENOUGH FOR FIRES TO SPREAD TOO
MUCH...BUT WOULD NOT BE SURPRISED TO SEE SOME FIRE STARTS ACROSS
CARBON COUNTY TODAY. THEY HAVE BEEN REALLY DRYING OUT OVER THE
WEEKEND WITH AFTERNOON HUMIDITIES FALLING INTO THE SINGLE DIGITS
EACH DAY FOR THE PAST 4-5 DAYS. WILL MENTION DRY THUNDERSTORMS IN
THE MORNING FIRE WEATHER FORECAST FOR LATE THIS MORNING/EARLY
AFTERNOON.

ATTENTION TURNS TO OUR ZONES EAST OF THE LARAMIE RANGE THIS
AFTERNOON AND EVENING. AGREE WITH SPC PULLING THE MARGINAL RISK
FOR SEVERE THUNDERSTORMS FURTHER WEST THIS AFTERNOON. MODEL POINT
SOUNDINGS FORECASTING CAPE OF ANYWHERE FROM 1500-1800 J/KG UP BY
DOUGLAS TO 2500 TO 2700 J/KG NEAR ALLIANCE AND CHADRON THIS
AFTERNOON. DID INTRODUCE SEVERE THUNDERSTORM WORDING INTO THE
FORECAST FOR THIS AFTERNOON AND EARLY EVENING AND WILL UPDATE
SEVERE WORDING IN THE MORNING HWO. WITH LACK OF SHEAR..THESE STORM
WOULD BE THE PULSE TYPE THAT WE HAVE SEEN THE PAST COUPLE
AFTERNOONS OUT IN THE PANHANDLE. STORM MOTIONS ARE FORECAST TO BE
FAIRLY SLOW AS WELL...DOUGLAS TO CHADRON...FROM THE NORTH AT
10KTS. SO FLASH FLOOD THREAT WILL DEFINITELY BE THERE. DAY SHIFT
MAY WANT TO ISSUE A FLASH FLOOD WATCH FOR THIS AFTERNOON DEPENDING
ON LATER UPDATES FROM MODELS. WILL MENTION THREAT IN THIS MORNINGS
HWO AS WELL.

ECMWF BRINGS THE UPPER SHORTWAVE INTO THE AREA TUESDAY AROUND NOON
TIME OR SO. COULD BE ANOTHER SEVERE THUNDERSTORM THREAT FOR THE
PANHANDLE TUESDAY AFTERNOON AS THIS TAKES PLACE...THOUGH NOT AS
GREAT AS TODAY.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 221 AM MDT MON AUG 3 2015

THE MAIN CONCERN WITH THIS PORTION OF THE FORECAST PACKAGE WILL BE
WHEN THE BEST POTENTIAL FOR CONVECTION WILL BE THROUGH THE
WEEKEND.

WEDNESDAY-THURSDAY:
BLENDED/DETERMINISTIC MODELS ARE IN PRETTY GOOD AGREEMENT IN
BRINGING A WEAK MID LEVEL SHORTWAVE THROUGH THROUGH NORTHERN
WYOMING ON WEDNESDAY NIGHT INTO THURSDAY. THIS FEATURE WILL TEND
TO BREAK DOWN THE RIDGE WHICH WILL BE PRESENT THROUGH MUCH OF THE
DAY WEDNESDAY. AS THIS SHORTWAVE/JET STREAK PUSHES THROUGH...IT
WILL TEND TO INCREASE THE MOISTURE TRANSPORT AHEAD OF IT AND YIELD
TO SOME SCATTERED EVENING/OVERNIGHT THUNDERSTORMS ACROSS THE
NORTHERN PORTIONS OF THE FORECAST AREA. THIS SHORTWAVE/SURFACE
FRONT SHOULD PUSH THROUGH THE NEBRASKA PANHANDLE ON THURSDAY
AFTERNOON AND MAY BRING MORE SCATTERED SHOWERS AND THUNDERSTORMS
TO THAT REGION. OTHERWISE...TEMPERATURES WILL REMAIN ON THE WARM
SIDE WITH HIGHS GENERALLY IN THE 80S. DEPENDING ON THE TIMING OF
THE FRONT...WE MAY SEE TEMPERATURES A BIT WARMER ON THURSDAY
MAINLY EAST OF THE LARAMIE RANGE WHERE DOWNSLOPE FLOW MAY BE
PRESENT. WE WILL STAY ON THE CONSERVATIVE SIDE FOR NOW...BUT WE
MAY BOOST TEMPERATURES A BIT MORE AS TIME GETS CLOSER.

FRIDAY-SUNDAY:
THE MODELS ARE IN GENERAL AGREEMENT IN SHOWING AN UPPER LEVEL
RIDGE BUILDING OVER THE AREA ON FRIDAY WHICH SHOULD YIELD TO
FAIRLY DRY CONDITIONS ALONG WITH HIGHER FIRE DANGER. HOWEVER...THERE
IS QUITE A BIT OF UNCERTAINTY HOW THINGS MAY PAN OUT LATE
SATURDAY INTO SUNDAY. THE MODELS SEEM TO BE A BIT AGGRESSIVE ON
SHIFTING THE RIDGE EAST OF THE AREA BY SATURDAY EVENING AND
BRINGING BACK SOME OF THE MONSOONAL MOISTURE SATURDAY NIGHT. THEN
IT IS QUICK TO SHOVE OUT THE MOISTURE EVEN THOUGH OUR SYNOPTIC
PATTERN DOES NOT CHANGE THAT MUCH. AS A RESULT...WE COULD END UP
HAVING A CHANCE OF THUNDERSTORMS THROUGH EARLY NEXT WEEK. WE WILL
STICK CLOSE TO SUPERBLEND FOR NOW WHICH KEEPS THINGS MOSTLY DRY ON
SUNDAY WITH HIGHS STAYING RATHER MILD IN THE 80S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 546 AM MDT MON AUG 3 2015

LATEST WATER VAPOR LOOP WAS SHOWING A FAIRLY COMPACT UPPER LEVEL
DISTURBANCE IN NORTHEAST UTAH. THIS FEATURE IS EXPECTED TO LIFT
NORTH INTO WYOMING TODAY. AS THIS OCCURS...WE WILL SEE MORE
MOISTURE CONTINUE TO STREAM NORTH INTO AREAS WEST OF THE LARAMIE
RANGE THIS MORNING. AS A RESULT...WE MAY SEE RAIN/ISOLATED
THUNDERSTORMS MOVE TOWARDS THE RWL TAF AROUND 14Z OR SO. THE REST
OF THE TAF SITES MAY SEE SOME SCATTERED CONVECTION BEGIN TO BREAK
OUT DURING THE AFTERNOON. ANY STORM THAT DOES DEVELOP WILL BE A
SLOW MOVER AND MAY YIELD TO PULSE TYPE SEVERE STORMS ALONG WITH
HEAVY RAINFALL.

&&

.FIRE WEATHER...
ISSUED AT 330 AM MDT MON AUG 3 2015

ACTIVE WEATHER THE NEXT 24 TO 48 HOURS AS MONSOONAL MOISTURE
BEGINS TO MOVE INTO THE AREA FROM THE SOUTHWEST. THUNDERSTORMS
OVER CARBON COUNTY COULD BE INITIALLY DRY LATE THIS MORNING AND
EARLY AFTERNOON BEFORE TURNING WET. COULD SEE SOME FIRE STARTS AS
A RESULT. SOUTHWESTERLY WINDS BEGIN TO INCREASE WEST OF THE
LARAMIE RANGE LATE THIS AFTERNOON AND THE MONSOON MOISTURE WILL
SPREAD EAST OF THE LARAMIE RANGE BY EARLY EVENING. BY THIS
EVENING...MOST AREAS ARE LIKELY TO SEE WETTING RAINS THAT WILL
CONTINUE INTO TUESDAY.

&&

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

$$

SHORT TERM...GCC
LONG TERM...REC
AVIATION...REC
FIRE WEATHER...GCC


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