Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 172135
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
335 PM MDT SUN AUG 17 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT)
ISSUED AT 330 PM MDT SUN AUG 17 2014

AFTERNOON WATER VAPOR LOOP REVEALED A CLOSED UPPER LOW NORTH OF THE
NORTH DAKOTA BORDER WITH A TROUGH AXIS INTO THE WESTERN DAKOTAS.
CLUSTERS OF INTENSE CONVECTION WERE DEVELOPING AHEAD OF THIS FEATURE.
CYS/RIW RADARS SHOWED A FEW SHOWERS DEVELOPING ALONG A WEAK CONVERGENCE
ZONE FROM SOUTHERN NATRONA TO SOUTHERN CONVERSE COUNTY. THE HRRR MODEL
COMPOSITE REFLECTIVITY LOOP SHOWED THIS ACTIVITY MOVING ACROSS EAST
CENTRAL WYOMING THROUGH LATE AFTERNOON THEN DISSIPATING. WITH VERY DRY
SUB-CLOUD LAYER...CAN EXPECT GUSTY WINDS AND LITTLE IF ANY MEASURABLE
RAINFALL WITH THESE SHOWERS. MAIN CONCERN CONTINUES TO BE FIRE WEATHER
IMPACTS FROM THE GUSTY WINDS AND LOW HUMIDITY FOR ELEVATIONS BELOW
8000 FT. RED FLAG WARNING REMAINS IN EFFECT FOR ALL BUT THE SIERRA
MADRE/SNOWY RANGE ZONES THROUGH 7 PM. GETTING CLOSE TO RED FLAG
CRITERIA OVER THE NEBRASKA PANHANDLE ZONES BORDERING WYOMING.
CONDITIONS WILL IMPROVE THIS EVENING AS WINDS DECREASE AND HUMIDITIES
INCREASE.

A BLEND OF THE 12Z SHORT RANGE MODEL GUIDANCE HANDLES THE LARGE SCALE
PATTERN PRETTY WELL. THE UPPER TROUGH ADVANCES EAST SOUTHEAST ACROSS
THE DAKOTAS AND MIDWEST DURING THE NEXT 24 HOURS. MEANWHILE...A UPPER
RIDGE EXPANDS NORTHWEST FROM THE FOUR CORNERS REGION WITH A HEALTHY
SURGE OF SUBTROPICAL MOISTURE MOVING INTO THE CENTRAL ROCKIES TUESDAY.
PRECIP WATER VALUES MONDAY WILL RANGE FROM A HALF INCH WEST OF THE
LARAMIE RANGE TO AROUND AN INCH FOR THE HIGH PLAINS. TUESDAY...PRECIP
WATER INCREASE TO AROUND 1.25 INCHES EAST OF THE LARAMIE AND 0.75-1.0
INCH TO THE WEST. DIURNAL CONVECTIVE COVERAGE MONDAY WILL BE ISOLATED
AND CONFINED TO THE MOUNTAINS. THE AIRMASS OVER THE PLAINS WILL REMAIN
CAPPED PRECLUDING SHOWER DEVELOPMENT. SHOWER/TSTORM COVERAGE INCREASES
TO SCATTERED TUESDAY AFTERNOON/EVENING AS A POTENT SHORTWAVE RIDES
NORTHEAST ACROSS WYOMING AND COLORADO. DOWNSLOPING WESTERLY WINDS WILL
LIMIT QPF OVER THE EASTERN WYOMING PLAINS...WITH AT LEAST O.25 INCH
AMOUNTS POSSIBLE OVER THE HIGHER TERRAIN AND WESTERN NEBRASKA PANHANDLE.

ABOVE NORMAL WARMTH WILL CONTINUE MONDAY LOWER ELEVATIONS MONDAY AND
EAST OF THE LARAMIE RANGE TUESDAY WITH HIGHS IN THE 80S TO LOWER 90S.
TEMPERATURES WILL TREND SLIGHTLY COOLER WEST OF THE LARAMIE RANGE
TUESDAY DUE TO GREATER CLOUD AND SHOWER COVERAGE.

.LONG TERM...(WEDNESDAY THROUGH SUNDAY)
ISSUED AT 300 PM MDT SUN AUG 17 2014

WARM AND MAINLY DRY WEATHER EXPECTED ACROSS THE CWA WEDNESDAY AND
THURSDAY THOUGH A FEW SHOWERS/TSTRMS POSSIBLE OVER THE HIGHER SRN
MTNS BOTH AFTERNOONS/EARLY EVENINGS. CHANGES LOOK TO BE IN THE
OFFING BEGINNING FRIDAY AND CONTINUING INTO THE WEEKEND AS AN
UPPER TROF SETTLES OVER THE NW PART OF THE COUNTRY AND A PUSH OF
COOLER CANADIAN AIR DROPS DOWN THE HIGH PLAINS SATURDAY AND
SATURDAY NIGHT WITH THE EC CONTINUING TO BE MUCH MORE BULLISH IN
PUSHING THIS COOL AIR ACROSS THE CWA BY LATE SATURDAY...SETTING UP
A MILD DAY FOR SUNDAY. EC HAS BEEN CONSISTENT WITH THIS. SHOULD
ALSO SEE A BIT OF AN UPTICK IN CONVECTION FRIDAY AND SATURDAY AS
THE UPPER TROF NEARS WITH ANY ASSOCIATED IMPULSES ROUNDING THE
BASE OF IT PASSING ACROSS THE AREA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY MORNING)
ISSUED AT 1120 AM MDT SUN AUG 17 2014

VFR CONDITIONS THROUGH MONDAY WITH A RATHER DRY AIR MASS OVER THE
AREA.  A WEAK SFC COOL FRONT WILL MOVE SOUTH ACROSS WY AND WRN
NEBRASKA TONIGHT SWITCHING WINDS TO LIGHT NORTHERLY OVER THE PLAINS.

&&

.FIRE WEATHER...
ISSUED AT 220 PM MDT SUN AUG 17 2014

NORTHWEST WINDS GUSTS OF 25 TO 35 MPH COMBINED WITH RELATIVE HUMDITIES
OF 10 TO 15 PERCENT WILL CREATE CONDITIONS CONDUCIVE TO RAPID FIRE
GROWTH FOR AREAS BELOW 8000 FEET IN SOUTHEAST WYOMING THROUGH EARLY
EVENING. GUSTS APPROACHING 25 MPH AND 10 TO 15 PERCENT HUMIDITIES
OVER THE FAR WESTERN NEBRASKA PANHANDLE WILL ENHANCE THE FIRE WEATHER
THREAT THIS AFTERNOON. FIRE WEATHER CONCERNS WILL BECOME MINIMAL
MONDAY AND TUESDAY AS AN INFLUX OF MONSOON MOISTURE FROM THE SOUTHWEST
INCREASES CHANCES FOR WETTING RAINS EARLY THIS WEEK. WINDS WILL BE
LIGHTER AS WELL. DRIER CONDITIONS RETURN MID WEEK FOLLOWED BY A SLIGHT
INCREASE IN MOISTURE LATE IN THE WEEK. ABOVE AVERAGE TEMPERATURES THIS
WEEK WILL GRADUALLY COOL NEXT WEEKEND.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR WYZ301>304-306-
     308>310.

NE...NONE.
&&

$$

SHORT TERM...JAMSKI
LONG TERM...RE
AVIATION...RE
FIRE WEATHER...JAMSKI




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