Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 242208
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
408 PM MDT SUN MAY 24 2015

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 408 PM MDT SUN MAY 24 2015

SHOWERS AND THUNDERSTORMS HAVE EXPANDED IN COVERAGE SINCE THE
EARLIER FORECAST UPDATE...WITH MODERATE RAINFALL  OBSERVED AT
TIMES ALONG WITH SMALL HAIL NEAR CHEYENNE. ACTIVITY IS INCREASING
OVER THE NORTHERN LARAMIE RANGE AND CENTRAL CONVERSE COUNTY AS
WELL...WITH SLOW MOVING THUNDERSTORMS OBSERVED ON RADAR. COULD
STILL SEE SOME HEAVIER RAINFALL TOTALS OUT OF THIS ACTIVITY SO
WILL MAINTAIN THE FLASH FLOOD WATCH. THE STRONGEST STORM SO FAR
THOUGH IS OVER NORTHERN SIOUX COUNTY WITHIN THE SLIGHTLY MORE
UNSTABLE ENVIRONMENT. IT CONTINUES TO TREK EAST TOWARD DAWES
COUNTY WITH FURTHER DEVELOPMENT TO THE SOUTH. EXPECT THESE TRENDS
TO CONTINUE THROUGH THE EVENING.

FOR TONIGHT...THE UPPER LOW WILL FINALLY MOVE NORTHEAST OVER THE CWA
AND WILL WEAKEN. SIMILARLY...THE SFC LOW WILL STEADILY TREK
NORTHEAST WITH  WINDS SHIFTING TO THE NNW BEHIND THE LOW. OVERALL
FLOW SHOULD REMAIN ON THE WEAKER SIDE TONIGHT...WITH AREAS OF FOG
REDEVELOPING OVERNIGHT ACROSS MUCH OF THE AREA. WITH THE NW FLOW
IN PLACE...DRIER AIR SHOULD BEGIN TO FILTER INTO THE CWA WHICH
WILL REDUCE OVERALL COVERAGE OF SHOWERS AND THUNDERSTORMS FOR
MONDAY. HOWEVER...COOLER AIR WITHIN THE UPPER TROUGH WILL REMAIN
OVERHEAD SO EXPECT AT LEAST SCATTERED COVERAGE OF SHOWERS WITH
ISO-T LATE MORNING THROUGH THE EVENING...ESPECIALLY OVER HIGHER
TERRAIN FEATURES.

A WEAK TRANSITORY RIDGE LOOKS TO MOVE OVERHEAD FOR TUESDAY
BRINGING WARMER TEMPS TO THE FORECAST AREA ALONG WITH SUBSIDENCE
ALOFT. SFC HIGH PRESSURE IS FORECAST TO SLIDE SOUTHEAST INTO THE
CENTRAL PLAINS THROUGH THE DAY...WITH SFC WINDS VEERING BACK TO
THE SOUTHEAST AND INCREASING LLVL UPSLOPE FLOW OVER THE CWA
THROUGH THE AFTERNOON. THE COMBINATION OF UPSLOPE AND HIGHER
TEMPS SHOULD MAINTAIN AT LEAST A CHANCE FOR AFTERNOON SHOWERS AND
THUNDERSTORMS...AGAIN ESPECIALLY NEAR TERRAIN FEATURES.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 408 PM MDT SUN MAY 24 2015

AN ACTIVE PATTERN IS EXPECTED TO CONTINUE THROUGH THE WEEK AS LARGE
SCALE TROUGHING REMAINS INTACT ACROSS THE WESTERN US. A FEW EMBEDDED
DISTURBANCES WITHIN MOIST SOUTHWEST FLOW ALOFT COMBINED WITH PERIODS
OF LLVL UPSLOPE WILL PROMOTE DAILY CHANCES FOR CONVECTION THROUGH AT
LEAST THE END OF THE WORK WEEK. GENERALLY WEAK MID LEVEL FLOW / LESS
THAN 25 KTS AT H5 / WILL KEEP CHANCES FOR STRONG TO SEVERE STORMS ON
THE LOW SIDE...BUT THE GFS SUGGESTS SBCAPE AROUND 1500 J/KG ACROSS A
LARGE PART OF THE EASTERN PLAINS ON WED-THU. CANNOT RULE OUT A STRAY
SEVERE STORM...BUT ANYTHING ORGANIZED APPEARS UNLIKELY. EXPECT DAILY
HIGHS TO HOLD FAIRLY STEADY THROUGH THE EXTENDED GIVEN A PERSISTENT
UPPER LEVEL PATTERN IN PLACE. H7 TEMPS AVERAGING AROUND 5 C SUGGEST
HIGHS IN THE 65 TO 75 DEGREE RANGE FOR MOST AREAS. RIDGING ALOFT AND
A PUSH OF DRIER AIR ASSOCIATED WITH A CANADIAN SURFACE HIGH DIPPING
INTO THE UPPER MIDWEST MAY GIVE US A BREAK FROM PRECIPITATION AS WE
HEAD INTO THE WEEKEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1213 PM MDT SUN MAY 24 2015

SCT-TO-BKN COVERAGE OF LOW-LEVEL CUMULUS CAN BE EXPECTED THIS AFTN
ALONG WITH INCREASING SHOWERS AND THUNDERSTORMS. VFR TO MVFR CIGS
SHOULD PREVAIL TODAY...WITH THE WORST CONDITIONS OCCURRING BENEATH
ANY HEAVIER STORMS. SHOWERS MAY CONTINUE THROUGH THE NIGHT ACROSS
MUCH OF THE AREA. IFR/LIFR CONDITIONS ARE POSSIBLE AT KRWL AND MUCH
OF THE WESTERN PANHANDLE AFTER 06Z...CONTINUING THROUGH MID AM
MON.

&&

.FIRE WEATHER...
ISSUED AT 408 PM MDT SUN MAY 24 2015

SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH MUCH OF THE WEEK AND
WILL BRING MODERATE TO HEAVY RAINFALL AT TIMES ACROSS THE DISTRICT.
WITH PLENTIFUL MOISTURE ANTICIPATED...NO FIRE WEATHER CONCERNS ARE
EXPECTED.

&&

.HYDROLOGY...
ISSUED AT 408 PM MDT SUN MAY 24 2015

FORECAST RAINFALL FROM SHOWERS DURING THE NEXT 24 HOURS WILL AVERAGE
BETWEEN 0.25 AND 0.50 INCHES...WITH LOCALLY HEAVIER AMOUNTS POSSIBLE
WITH THUNDERSTORMS. RUNOFF FROM THIS RAINFALL WILL MAINTAIN HIGH
WATER LEVELS ALONG THE LARAMIE RIVER AT LARAMIE AND NEAR FORT
LARAMIE THROUGH EARLY NEXT WEEK. REFER TO THE LATEST RIVER AND FLOOD
STATEMENTS FOR SPECIFIC INFORMATION.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...FLASH FLOOD WATCH UNTIL 6 PM MDT THIS EVENING FOR WYZ101-103>105-
     109.

NE...NONE.
&&

$$

SHORT TERM...RJM
LONG TERM...CLH
AVIATION...CLH
FIRE WEATHER...RJM
HYDROLOGY...MJ/RJM



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