Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 271713
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1113 AM MDT SUN JUL 27 2014

.UPDATE...
ISSUED AT 1045 AM MDT SUN JUL 27 2014

THE LATE MORNING WATER VAPOR LOOP DEPICTED A UPPER RIDGE AXIS
FROM SOUTHERN GREAT PLAINS TO THE NORTHERN ROCKIES. SUBTROPICAL
MOISTURE CONTINUED TO ADVECT NORTH AND EAST UNDER THE RIDGE FROM
THE DESERT SOUTHWEST ACROSS THE CENTRAL ROCKIES. 12Z REGIONAL
SOUNDINGS INDICATED EAST TO SOUTHEAST FLOW BELOW 750MB TRANSPORTING
LOW LEVEL MOISTURE /50-60 DEGREE DEW POINTS/ INTO SOUTHEAST WY.
PRECIP WATER VALUES ARE BETWEEN 0.50 AND 0.75 INCH. LOW CLOUDS
HAVE BEEN PERSISTENT OVER THE SOUTHEAST WY PLAINS AND SOUTHERN
LARAMIE RANGE THIS MORNING. VIS SATELLITE TRENDS AND FORECAST
SOUNDINGS MAINTAIN LOW CEILINGS UNTIL MIDDAY THEN BECOMING SCATTERED.
LATEST HRRR/WRF/SREF REFLECTIVITY PROGS DEVELOP CONVECTION OVER THE
HIGHER TERRAIN OF SOUTHEAST WY BY MID AFTERNOON...SPREADING SOUTHEAST
IN NORTHWEST STEERING FLOW. COULD SEE AN ISOLATED TSTORM AS FAR EAST
AS CHEYENNE LATER THIS AFTERNOON AND HAVE NUDGED POPS UP TO 15-20
PERCENT FOR CENTRAL LARAMIE COUNTY FOR THE 21Z-00Z PERIOD. LOW-MID
LEVEL SHEAR WILL BE WEAK AND CAPES GENERALLY BELOW 1000 J/KG...SO
SEVERE THREAT WILL BE LOW.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 230 AM MDT SUN JUL 27 2014

TODAY...HEIGHTS ALOFT INCREASE SLIGHTLY AS RIDGING BECOMES MORE
PRONOUNCED ACROSS WESTERN WYOMING. SURFACE HIGH PRESSURE OVER THE
PLAINS STATES KEEPS MOIST EASTERLY LOW LEVEL WINDS ACROSS OUR
COUNTIES. BY THIS AFTERNOON...A LOW AND MID LEVEL THETA-E RIDGE AXIS
DEVELOPS FROM CASPER TO LARAMIE...AND THUS EXPECT ISOLATED TO
LOCALLY SCATTERED THUNDERSTORMS TO ERUPT THIS AFTERNOON OVER AND
NEAR THE SNOWY AND SIERRA MADRE RANGES...DRY ELSEWHERE.

TONIGHT...QUIET AND COOL OVERNIGHT WITH LOSS OF DAYTIME HEATING.

MONDAY...RIDGING ALOFT NOT QUITE AS PRONOUNCED AND WITH A LOW AND
MID LEVEL THETA-E RIDGE AXIS DEVELOPING ACROSS SOUTHEAST WYOMING AND
POSITIVE THETA-E ADVECTION...THUNDERSTORM COVERAGE IN THE AFTERNOON
AND EVENING WILL INCREASE ALONG AND WEST OF INTERSTATE 25.

MONDAY NIGHT...MAY SEE AT LEAST ISOLATED SHOWERS AND THUNDERSTORMS
CONTINUE ALL NIGHT AS LOW AND MID LEVEL MOISTURE REMAINS WITH A WEAK
SHORTWAVE TROUGH ALOFT MOVING OVERHEAD IN NORTHWEST FLOW ALOFT.

TUESDAY...CONTINUES TO LOOK LIKE A DAY WITH SCATTERED TO NUMEROUS
SHOWERS AND ISOLATED THUNDERSTORMS...ESPECIALLY SOUTH OF A RAWLINS
TO SCOTTSBLUFF LINE WHERE THE ATMOSPHERE WILL BE THE MOST MOIST.
COMPROMISED ON HIGH TEMPERATURES...THOUGH THE COOLER NAM MOS HIGHS
COULD BE CLOSEST IF SHOWERS PERSIST MOST OF THE DAY.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 230 AM MDT SUN JUL 27 2014

A LARGE SCALE BLOCKING PATTERN WILL REMAIN IN PLACE ACROSS THE
CONUS THROUGH THE EXTENDED FCST PERIOD. STRONG UPPER-LEVEL RIDGING
OVER THE WESTERN STATES WITH A PERSISTENT TROUGH ANCHORED ALONG
THE EASTERN SEABOARD WILL KEEP THE CENTRAL ROCKIES UNDER ACTIVE
NORTHWESTERLY FLOW ALOFT THROUGH MID TO LATE WEEK. MEDIUM RANGE
MODEL GUIDANCE SHOWS THE BEST MONSOONAL MOISTURE TO BE IN THE WED
TO THU TIME FRAME...FAVORABLY ALIGNED WITH INCREASING MOIST LLVL
UPSLOPE WITH A COLD FRONTAL PASSAGE. THE GFS IS CONSIDERABLY DRIER
THAN THE ECMWF WHICH SHOWS 36 HOUR QPF VALUES WELL IN EXCESS OF 2
INCHES OVER THE SOUTH LARAMIE RANGE. THIS IS A FAVORABLE PATTERN FOR
A WIDESPREAD PCPN EVENT WITH THE POTENTIAL FOR TRAINING CONVECTION.
WPC PRECIP OUTLOOKS ALSO NAIL DOWN THE CO FRONT RANGE INTO SOUTHEAST
WY FOR EXCESSIVE RAINFALL THROUGH MID WEEK. AS SUCH...THIS WILL
DEFINITELY NEED TO BE WATCHED OVER THE NEXT FEW DAYS. TRENDED
HIGHER WITH POPS THIS FCST PACKAGE...AND CONTINUED TO GO SEVERAL
DEGREES BELOW CONSENSUS MOS FOR HIGHS ON WED GIVEN H7 TEMPS BETWEEN
8 AND 10 C AND EXPECTED CLOUDS/PCPN. MOISTURE APPEARS TO BECOME
MORE LIMITED LATE IN THE WEEK...AND SUBSIDENCE STRENGTHENS AS THE
RIDGE SHIFTS SLOWLY EASTWARD. CONVECTIVE CHANCES BEYOND WED SHOULD
BE CONFINED TO THE HIGHER TERRAIN. OVERALL TEMPS SHOULD BE QUITE
SEASONAL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY MORNING)
ISSUED AT 1113 AM MDT SUN JUL 27 2014

MVFR CIGS AFFECTING KCYS EXPECTED TO RISE/BREAK TO VFR EARLY THIS
AFTERNOON WITH VFR ELSEWHERE THROUGH MONDAY MORNING.  ISOLATED
SHOWERS AND STORMS ARE POSSIBLE OVER THE HIGHER ELEVATIONS THIS
AFTERNOON AND EVENING. MOST OF THIS ACTIVITY WILL BE CONFINED TO THE
MOUNTAINS THOUGH SOME MAY COME INTO THE VCTY OF KLAR AND KCYS
MID-LATE THIS AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 230 AM MDT SUN JUL 27 2014

HUMIDITIES WILL CONTINUE TO SLOWLY INCREASE THROUGH TUESDAY AS
LOW LEVEL MOISTURE INCREASES AND CLOUDS AND PRECIPITATION COVERAGE
INCREASE.

&&

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

$$

UPDATE...JAMSKI
SHORT TERM...RUBIN
LONG TERM...HAMMER
AVIATION...RE
FIRE WEATHER...RUBIN




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