Area Forecast Discussion
Issued by NWS Cheyenne, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KCYS 240045 AAA
AFDCYS

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHEYENNE WY
645 PM MDT SAT MAY 23 2015

.UPDATE...FOR EVENING AVIATION FORECAST PACKAGE.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 530 PM MDT SAT MAY 23 2015

THE UPPER LOW IS SITUATED ALONG THE CO/UT BORDER THIS AFTERNOON
WITH A SHORTWAVE MOVING NORTH ACROSS EASTERN COLORADO IN SOUTHERLY
FLOW ALOFT. STRENGTHENING EAST-SOUTHEAST SFC FLOW AHEAD OF THIS
SYSTEM COMBINED WITH PLENTIFUL MIDLEVEL ENERGY AND UPPER LEVEL
DIFFLUENCE IS ALLOWING FOR A FAIRLY BROAD COVERAGE OF SHOWERS AND
THUNDERSTORMS THIS AFTERNOON.  THE INITIAL WAVE OF STORMS
OCCURRED SHORTLY AFTER THE NOON HOUR OVER THE HIGH COUNTRY WHERE
SKIES WHERE MOSTLY CLEAR. FURTHER EAST...CLOUDS NEVER FULLY BROKE
ACROSS THE MUCH OF THE PLAINS BUT SEEMED TO BE ENOUGH TO
DESTABILIZE THE AREA FOR MODERATE THUNDERSTORMS TO DEVELOP WITHIN
STRONG UPPER LEVEL FORCING. ALTHOUGH OVERALL DEEP LAYER SHEAR HAS
NOT BEEN ON THE WHOLE IMPRESSIVE AT 30 TO 40 KTS...LOCALIZED
POCKETS OF HIGHER LLVL SHEAR LIKELY DEVELOPED ALONG BOUNDARIES
NEAR TERRAIN FEATURES SUCH AS THE CHEYENNE RIDGE NEAR SIDNEY AND
JUST WEST OF THE LARAMIE RANGE NEAR BOSLER WITHIN THE
SOUTHEASTERLY FLOW...AND LIKELY CONTRIBUTED TO BRIEF TORNADO
TOUCHDOWNS AND FUNNEL CLOUDS IN THESE AREAS.

HOWEVER...FOCUS HAS TRANSITIONED MORE TO POSSIBLE HEAVY RAINFALL
IN SHOWERS AND THUNDERSTORMS ACROSS THE PLAINS DUE TO CONTINUED
BOUNDARY ACTION...MOISTURE ADVECTION IN UPSLOPE FLOW AND WAA. WENT
AHEAD AND ISSUED A FLASH FLOOD WATCH FOR THE SOUTHERN NEBRASKA
PANHANDLE AND PLATTE...GOSHEN...AND LARAMIE COUNTIES IN WYOMING
FOR THIS AFTERNOON THROUGH MIDNIGHT WITH HEAVY RAINFALL FROM
STORMS EXPECTED TO CONTINUE THROUGH THIS PERIOD AS THE SHORTWAVE
MOVES ACROSS THE AREA. WITH ALREADY SATURATED GROUNDS...WILL NOT
TAKE MUCH FOR FLOODING TO OCCUR IN THESE AREAS. FOR
TONIGHT...GUIDANCE SHOWS ISENTROPIC LIFT INCREASING ACROSS
SOUTHEAST WYOMING ALONG THE INVERTED SFC TROUGH SETTING UP ALONG
THE MOUNTAINS...AND WITHIN WRAP AROUND MOISTURE AND CONTINUED
UPPER FORCING AS THE LOW SLOWLY MOVES NORTHEAST ACROSS WYOMING. SO
EXPECT TO SEE MODERATE TO HEAVY RAIN CONTINUE OVERNIGHT ACROSS
NORTHERN AND WEST PORTIONS OF THE FORECAST AREA...ALTHOUGH CANT
RULE OUT A FEW HEAVIER RAIN SHOWERS FURTHER SOUTH ACROSS THE
PLAINS AS WELL. THE FOCUS FOR BEST FORCING WILL BE ALONG A LINE
FROM EAST-CENTRAL WYOMING TO SOUTH-CENTRAL WYOMING WHERE THE
MIDLEVEL TROUGH WILL SET UP AND AT THE NOSE OF THE INVERTED
TROUGH...SO WENT WITH A FLASH FLOOD WATCH FOR TONIGHT AND TOMORROW
ALONG THIS AREA WHICH INCLUDES CONVERSE...NORTHERN ALBANY...AND
NORTHERN CARBON COUNTIES FOR EXPECTED MODERATE TO HEAVY RAIN TO
PERSIST. LOOKING AT 1 TO 3 INCHES OF RAINFALL FOR NOW...BUT
LOCALLY HEAVIER AMOUNTS ARE POSSIBLE AS WELL ESPECIALLY ALONG
FAVORED TERRAIN FEATURES.

THE UPPER LOW WILL WEAKEN SUNDAY AND BECOME AN OPEN WAVE BY
MONDAY. COLD AIR WILL REMAIN OVERHEAD THROUGH THIS TIME WHILE A
SFC COLD FRONT SHIFTS SOUTHEAST ACROSS THE CWA LATE SUNDAY.
CONTINUED SOUTHEAST FLOW ACROSS THE PLAINS TONIGHT AND SUNDAY
AHEAD OF THE FRONT WILL REDEVELOP THE STRATUS/FOG DECK WHICH
SHOULD STRUGGLE TO BREAK AGAIN ON SUNDAY...BUT GUIDANCE DOES SHOW
SOME HIGHER INSTABILITY ACROSS THE PANHANDLE SO PERHAPS THERE
WILL BE MORE CLEARING IN THIS AREA. THUS WOULDNT BE SURPRISED IF
A FEW STRONGER THUNDERSTORMS DEVELOPED ONCE AGAIN IN ACROSS THE
PLAINS WITHIN THE POCKETS OF CLEARING WITHIN MODEST SHEAR. THE
UPPER TROUGH WILL FINALLY BEGIN TO SHIFT EAST OF THE FORECAST AREA
ON MONDAY ALTHOUGH SLOW ENOUGH TO MAINTAIN CHANCES FOR INSTABILITY
SHOWERS AND THUNDERSTORMS THROUGH THE DAY. WEAK WINDS ALOFT WILL
PROMOTE MODERATE TO HEAVY RAIN PRODUCERS AS PLENTIFUL MOISTURE
WILL REMAIN OVER THE REGION.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 530 PM MDT SAT MAY 23 2015

THE PATTERN WILL BECOME MORE TYPICAL FOR LATE MAY TUESDAY THRU
SATURDAY AS A SERIES OF SHORTWAVES EMBEDDED WITHIN RELATIVELY WEAK
FLOW PASS THRU THE INTERMOUNTAIN WEST. THUNDERSTORM COVERAGE WILL
BE ISOLATED TO SCATTERED AND GENERALLY CONFINED TO THE AFTERNOON
AND EVENING HOURS. ALTHOUGH CLOUDS WILL STILL BE AROUND...EXPECT
TO SEE MORE SUN NEXT WEEK THAN THE PAST FEW. MORE SUNSHINE WILL
ALLOW FOR WARMER DAYTIME TEMPERATURES WHICH WILL BE THE CULPRIT
FOR AFTERNOON/EVENING INSTABILITY AND RESULTANT CONVECTIVE
CHANCES. BRIEF TRANSITORY RIDGE EARLY TUESDAY WILL GIVE WAY TO
BACKING FLOW AS UPSTREAM SHORTWAVE ENERGY SWINGS INTO THE PACNW.
MODELS PUT THE TRANSITORY RIDGE AXIS IN THE VICINITY OF THE WY/NE
STATELINE WHICH WILL BE A GOOD MEASURE OF THE EASTERN EXTENT OF
THE CONVECTION ON TUESDAY. UPSTREAM SHORTWAVE WILL INCH CLOSER FOR
WEDNESDAY...SO EXPECT CONVECTIVE COVERAGE TO INCREASE TO MORE
SCATTERED COMPARED TO TUESDAY. THERE MAY BE A FEW STRONG STORMS ON
WEDNESDAY AS SBCAPES ARE PROGD TO CLIMB TO AROUND 600-1000 J/KG.
UPSTREAM SHORTWAVE FINALLY REACHES WRN WY BY THURSDAY...BUT EXPECT
A GENERAL REPEAT FOR THURSDAY. THE SHORTWAVE FINALLY PASSES THRU
FRIDAY...GIVING WAY TO...AT LEAST IF YOU BELIEVE THE ECMWF
MODEL...A BUILDING RIDGE AND DRYING CONDITIONS FOR NEXT WEEKEND.
AFTERNOON HIGH TEMPERATURES WILL BE NOTICABLY WARMER NEXT
WEEK...WITH GENERALLY 60S OVR SE WY AND LOW/MID 70S ACROSS THE WRN
NEBRASKA PANHANDLE.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 645 PM MDT SAT MAY 23 2015

AFTERNOON SHOWER AND THUNDERSTORM ACTIVITY IS GRADUALLY BECOMING
MORE STRATIFORM MOST AREAS THIS EVENING AND WE SHOULD SEE A
GENERAL DECREASE IN THUNDERSTORM ACTIVITY THROUGH 05Z. AFTER
THAT...HRRR AND NAM MORE CONSISTENT IN WANTING TO LOWER CEILINGS
AND VISIBILITIES ALONG AND EAST OF THE LARAMIE RANGE
OVERNIGHT...SO WE ADVERTISED IFR/LIFR CEILINGS AND VISIBILITIES IN
LIGHT DRIZZLE AND FOG FOR CHEYENNE...SIDNEY AND ALLIANCE WHERE
LIGHT UPSLOPE FLOW WILL CONINUE THROUGH MORNING.
OTHERWISE...EXPECT MAINLY IFR TO BRIEFLY LIFR CEILINGS IN STRATUS
AT CHADRON...AND MVFR AT LARAMIE AND RAWLINS THROUGH
MORNING...ALTHOUGH A FEW SHOWERS AND ISOLATED THUNDERSTORMS WILL
PERSIST INTO LATE EVENING FOR AREAS AROUND LARAMIE AND RAWLINS.

&&

.FIRE WEATHER...
ISSUED AT 530 PM MDT SAT MAY 23 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.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...FLASH FLOOD WATCH UNTIL MIDNIGHT MDT TONIGHT FOR WYZ106>108-118-
     119.

     FLASH FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR WYZ101-103>105-
     109.

NE...FLASH FLOOD WATCH UNTIL MIDNIGHT MDT TONIGHT FOR NEZ019>021-054-
     055.

&&

$$

SHORT TERM...RJM
LONG TERM...CAH
AVIATION...JG
FIRE WEATHER...RJM


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.