Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 021806
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1206 PM MDT SUN AUG 2 2015

.UPDATE...
ISSUED AT 1128 AM MDT SUN AUG 2 2015

THUNDERSTORMS HAVE DEVELOPED QUICKLY LATE THIS MORNING NEAR THE
LARAMIE RANGE...SO INCREASED POP TODAY ALONG AND EAST OF THE
LARAMIE RANGE WHERE SCATTERED COVERAGE IS POSSIBLE. THE
PROBABILITY OF SEVERE TSTORMS IS LOW TODAY...BUT STORM MOTION AND
THE POTENTIAL FOR HEAVY RAINFALL IS THE MAIN CONCERN. STORM MOTION
THIS MORNING IS ACTUALLY A SLOW DRIFT TOWARDS THE SOUTHWEST. IT
WILL BE INTERESTING TO SEE HOW THIS ACTIVITY EVOLVES THROUGH THE
DAY ONCE A FEW PERSISTENT OUTFLOW BOUNDARIES DEVELOP. MAY NEED TO
MONITOR THE POTENTIAL FOR FLASH FLOODING THIS AFTERNOON AND INTO
THIS EVENING.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY NIGHT)
ISSUED AT 300 AM MDT SUN AUG 2 2015

TODAY...FLOW ALOFT REMAINS NORTHWEST. LOOKS LIKE THE NAM PROJECTS A
LOW LEVEL BOUNDARY TO SET UP THIS AFTERNOON ALONG THE WYOMING AND
COLORADO STATE LINE WITH A NICE 850/700 MB THETA-E RIDGE AXIS OVER
NORTHERN COLORADO. THUS...AS NAM DEPICTS...EXPECT ISOLATED TO
SCATTERED THUNDERSTORMS TO DEVELOP ALONG AND NEAR THE COLORADO STATE
LINE...THEN SLOWLY DIMINISH THIS EVENING ALONG THE LARAMIE RANGE.

TONIGHT/MONDAY...MODELS CONSISTENT IN SHOWING MORE MONSOONAL
MOISTURE BEING TAPPED INTO AND MOVING ACROSS OUR COUNTIES MONDAY
AFTERNOON...THOUGH NOW FURTHER WEST THAN PREVIOUS RUNS INDICATED.
STILL THOUGH...WITH A SHORTWAVE TROUGH ALOFT MOVING OVERHEAD AND
INCREASING LOW AND MID LEVEL MOISTURE...WILL CONTINUE OUR FORECAST
WITH ISOLATED TO SCATTERED AFTERNOON AND EVENING THUNDERSTORMS ALONG
AND WEST OF INTERSTATE 25...WITH LESSER ACTIVITY FURTHER EAST.

MONDAY NIGHT/TUESDAY/TUESDAY NIGHT...SHORTWAVE TROUGH ALOFT MOVES
SLOWLY EASTWARD ACROSS OUR NORTHERN COUNTIES...AND WITH PLENTY OF
LOW AND MID LEVEL MOISTURE...WILL SEE SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS OUR NORTHERN COUNTIES...LESS ACTIVITY FURTHER
SOUTH WITH DRIER AIRMASS AND NEGATIVE THETA-E ADVECTION.

.LONG TERM...(WEDNESDAY THROUGH SATURDAY)
ISSUED AT 300 AM MDT SUN AUG 2 2015

MONSOONAL MOISTURE TO REMAIN OVER THE AREA THROUGH AT LEAST
THURSDAY. DEPENDING ON WHICH MEDIUM RANGE GUIDANCE USED...IT COULD
BE LONGER. FORECAST BASED OFF THE MORE MOIST ECMWF THIS FORECAST
CYCLE.

STARTING OFF WEDNESDAY...WE ARE LOOKING AT THE SEMI-PERMANENT
THATS BEEN IN THE AREA TO LAY ALONG THE NEBRASKA
PANHANDLE...MAYBE SLIGHTLY FURTHER EAST. GFS SHOWING THE BOUNDARY
FURTHER EAST AND THUS THE ENTIRE CWFA DRY. ECMWF ON THE OTHER HAND
HAS THE BOUNDARY REMAINING ALONG THE EAST SLOPES OF THE LARAMIE
RANGE...WITH NORTHEAST UPSLOPE FLOW ACROSS THE PANHANDLE. THIS
WOULD GIVE MOST LOCATIONS ALONG AND EAST OF THE LARAMIE RANGE WITH
AT LEAST A SLIGHT CHANCE OF THUNDERSTORMS WEDNESDAY AFTERNOON.

THURSDAY AFTERNOON...A FAIRLY STRONG SHORTWAVE TRACKS ACROSS
NORTHERN WYOMING INTO SOUTH DAKOTA. STRONG SOUTH TO SOUTHEASTERLY
850MB WINDS IN THE PANHANDLE AND A 70KT 250MB JET COULD BE SETTING
US UP FOR ANOTHER ROUND OF SEVERE THUNDERSTORMS AT LEAST FOR THE
SOUTHERN HALF OF THE PANHANDLE AS WELL AS EASTERN LARAMIE
COUNTY...UP INTO GOSHEN COUNTY. SHOWERS AND THUNDERSTORMS LOOK TO
PERSIST INTO THE LATE EVENING HOURS THURSDAY.

AFTER A DRY FRIDAY WITH A TRANSITORY RIDGE MOVING THROUGH THE
CWFA...SATURDAY LOOKS TO BE A REPEAT OF THURSDAY AS ANOTHER
SHORTWAVE MOVES INTO THE AREA FROM THE SOUTHWEST. SHOULD SEE AT
LEAST SLIGHT CHANCE POPS FOR MUCH OF THE AREA WITH BEST CHANCES
ALONG THE WYOMING COLORADO STATE LINE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1206 PM MDT SUN AUG 2 2015

VFR CONDITIONS TO PREVAIL OUTSIDE OF THUNDERSTORM ACTIVITY. MVFR
CONDITIONS ARE POSSIBLE IN MODERATE TO HEAVY RAINFALL WITHIN
THUNDERSTORMS THIS AFTERNOON...WITH THE HIGHEST CONFIDENCE FOR
KCYS. MAINTAINED VCTS ELSEWHERE DUE TO EXPECTED ISOLATED COVERAGE
BUT WILL AMEND TO PREVAILING TSRA AS NECESSARY. WINDS WILL REMAIN
RELATIVELY LOW WITH GUSTS UP TO 20 MPH AT TIMES ACROSS THE
PLAINS THRU THE AFTERNOON. THE EXCEPTION WILL AGAIN BE IN AND
NEAR THUNDERSTORMS WHERE GUSTY ERRATIC WINDS ARE LIKELY.

&&

.FIRE WEATHER...
ISSUED AT 145 AM MDT SUN AUG 2 2015

HUMIDITIES INCREASING THE NEXT FEW DAYS AS LOW AND MID LEVEL
MOISTURE INCREASES ALONG WITH INCREASING CHANCES FOR LATE DAY
SHOWERS AND THUNDERSTORMS.

&&

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

$$

UPDATE...TJT
SHORT TERM...RUBIN
LONG TERM...GCC
AVIATION...RJM
FIRE WEATHER...RUBIN


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