Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 270441
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1041 PM MDT TUE MAY 26 2015

.UPDATE...
ISSUED AT 925 PM MDT TUE MAY 26 2015

THUNDERSTORM ACTIVITY CONTINUES TO WEAKEN ACROSS THE AREA THIS
EVENING. THERE ARE STILL A FEW THUNDERSTORMS INTO NIOBRARA COUNTY
IN EAST CENTRAL WYOMING BUT THOSE SHOULD DIE OFF IN THE NEXT HOUR
OR SO WITH ISOLATED SHOWERS THE REST OF TONIGHT. NO CHANGES TO THE

&&

.SHORT TERM...(TONIGHT - THURSDAY NIGHT)
ISSUED AT 352 PM MDT TUE MAY 26 2015

A WEAK SHORTWAVE TROUGH AND ASSOCIATED MID LEVEL VORT MAX CONTINUES
TO MOVE EASTWARD ACROSS WESTERN WY THIS AFTN. THIS...COMBINED WITH
LLVL CONVERGENCE ALONG THE LARAMIE RANGE IS PROVIDING SUFFICIENT
FORCING FOR ISOLATED TO WIDELY SCATTERED CONVECTION ACROSS MUCH OF
SOUTHEAST WY AND THE WESTERN NE PANHANDLE. 15 KT H5 FLOW RESULTS IN
VERY MODEST EFFECTIVE BULK SHEAR VALUES...SO DO NOT EXPECT TO SEE
ANY ORGANIZED SEVERE WEATHER TODAY DESPITE THE MARGINAL RISK ON THE
LATEST SPC DAY 1 OUTLOOK. COULD SEE A FEW STORMS PRODUCE SMALL HAIL
THOUGH WITH THE LATEST MESOANALYSIS SHOWING AROUND 1500 J/KG MLCAPE
VALUES AND A RELATIVELY COOL AIR MASS STILL IN PLACE WITH SFC TEMPS
IN THE LOW TO MID 60S. TORRENTIAL RAIN STILL A POSSIBILITY WITH PWAT
VALUES ON THE ORDER OF 0.7 INCH...SO COULD SEE SOME LOCALIZED MINOR
FLOODING ON SATURATED GROUND IF ANY STORMS HANG AROUND TOO LONG. THE
THREAT FOR SHOWERS AND THUNDERSTORMS SHOULD DECREASE INTO TONIGHT...
BUT GFS/NAM/ECM ALL HANG ON TO SOME WEAK QPF ACROSS OUR WESTERN AND
NORTHERN ZONES AS THE SHORTWAVE AXIS LIFTS NORTHEAST OVERNIGHT. WILL
HANG ON TO LOW-END POPS.

MOIST SOUTHWEST FLOW ALOFT REMAINS IN PLACE ON WEDNESDAY...WITH LEE
TROUGHING TAKING SHAPE ALONG THE WYO/NEB STATE LINE. MAIN CHALLENGE
WILL BE THE EASTWARD PROGRESSION OF THIS FEATURE AS THIS WILL PLAY A
MAJOR ROLE IN PCPN COVERAGE IN THE AFTN. UPPER DIFLUENCE ATOP WEAK
LLVL CONVERGENCE WILL HELP TO INITIATE CONVECTION ONCE AGAIN DURING
THE LATE MORNING THROUGH EARLY EVENING. AHEAD OF THE BOUNDARY...DEW
POINTS ARE PROGGED TO BE IN THE 50S WITH MODEST H7-H5 LAPSE RATES
AROUND 7 DEG C/KM. NAM CAPES BETWEEN 1000-2000 J/KG WOULD SUPPORT A
FEW STRONGER STORMS ONCE AGAIN...SO THE SPC MARGINAL RISK LOOKS GOOD
FOR THE PANHANDLE. OPTED NOT TO MENTION ANY SMALL HAIL ATTM AS THE
POTENTIAL FOR ORGANIZED CONVECTION IS LIMITED. SOME WARM ADVECTION
TOMORROW HELPING TO INCREASE H7 TEMPS TO 5-8 DEG C PER MOST OF OUR
AVAILABLE GUIDANCE...SO SHOULD SEE A FEW MORE 70S FOR HIGHS. THE
OVERALL PATTERN WILL REMAIN THE SAME INTO THU AS A POORLY ORGANIZED
SHORTWAVE SHIFTS ACROSS WESTERN WY. CONVECTION IS LIKELY ONCE AGAIN
IN THE AFTERNOON...THOUGH THE BETTER CHANCE FOR STRONGER STORMS WILL
BE TO THE EAST WITH THE BETTER INSTABILITY.

.LONG TERM...(FRIDAY - TUESDAY)
ISSUED AT 352 PM MDT TUE MAY 26 2015

THE WET PATTERN WILL PERSIST ON FRIDAY AS AN UPPER SHORTWAVE
PASSES ACROSS THE REGION AND INTERACTS WITH SFC UPSLOPE FLOW
BEHIND A COOL FRONT THAT WILL PASS ACROSS EARLY IN THE DAY. THE
RAIN WILL END FRIDAY NIGHT AS THE UPPER WAVE MOVES EAST AND DRIER
AIR FILTERS INTO THE AREA. A RELATIVELY DRY WEEKEND LOOKING TO SET
UP OVER THE AREA AS UPPER RIDGING MOVES ACROSS THE AREA THOUGH
SOME WIDELY SCTD CONVECTION POSSIBLE MAINLY NEAR THE MTNS SUNDAY
AS MOISTURE BEGINS RETURNING NORTHWARD IN RESPONSE TO LEE TROFFING
OVER THE HIGH PLAINS. MONDAY AND TUESDAY WILL SEE MORE TYPICAL
LATE SPRING WEATHER OVER THE CWA WITH AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS AS THE UPPER FLOW TURNS SW AHEAD OF THE
NEXT UPPER TROF THAT WILL MOVE OVER THE WESTERN CONUS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1038 PM MDT TUE MAY 26 2015

VFR CONDITIONS EXPECTED FOR ALL SOUTHEAST WYOMING AND NEBRASKA
PANHANDLE AIRPORTS OVERNIGHT INTO WEDNESDAY. SHOWERS ARE WEAKENING
NOW NORTH OF A LINE FROM WHEATLAND TO CHADRON LATE THIS EVENING
AND SHOULD CONTINUE TO DO SO. CONVECTION EXPECTED TO RETURN
WEDNESDAY AFTERNOON WITH TEMPERATURES CLIMBING BACK INTO THE 70S.
ADDED VCTS WORDING FOR ALL TAFS. WILL NARROW IN ON TIMING AS THE
EVENT GETS CLOSER.

&&

.FIRE WEATHER...
ISSUED AT 352 PM MDT TUE MAY 26 2015

NO FIRE WEATHER CONCERNS WITH RECENT RAINFALL AND CONTINUED DAILY
CHANCES FOR SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE AREA.

&&

.HYDROLOGY...
ISSUED AT 919 PM MDT TUE MAY 26 2015

LATEST RIVER FORECAST HAS BEEN ISSUED. FORECASTS AT THE RIVER
FORECAST POINTS ALONG THE NORTH PLATTE RIVER AND LARAMIE RIVER
HAVE GENERALLY BEEN LOWERED AS MOST THUNDERSTORM ACTIVITY MISSED
THE RUNOFF BASIN TODAY. ACTUAL RIVER CRESTS COULD CERTAINLY BE
ADJUSTED DEPENDING ON EXACT LOCATION OF CONVECTION THE NEXT FEW
DAYS BUT GIVEN THE RANDOM NATURE OF CONVECTIVE ACTIVITY...ANY NEW
PRECIPITATION WILL NEED TO BE CLOSELY MONITORED.

&&

.CLIMATE...
ISSUED AT 352 PM MDT TUE MAY 26 2015

CHEYENNE RECEIVED ANOTHER 0.29 INCH OF RAINFALL WITH A HEAVY STORM
EARLIER THIS AFTERNOON. THIS BRINGS OUR MONTHLY TOTAL TO 5.74
INCHES...BUMPING US TO THE 5TH WETTEST MAY ON RECORD. THE RECORD
IS 6.66 INCHES IN 1904. CHANCES FOR SHOWERS AND THUNDERSTORMS WILL
EXIST EVERY DAY THROUGH THE REST OF THE WEEK. THERE IS A SMALL
CHANCE OF EXCEEDING THE ALL TIME RECORD BEFORE THE END OF THE
MONTH IF ANY HEAVIER STORMS AFFECT THE CITY.

&&

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

$$

UPDATE...SML
SHORT TERM...CLH
LONG TERM...RE
AVIATION...GCC
FIRE WEATHER...CLH
HYDROLOGY...SML
CLIMATE...CLH


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