Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 172337
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
530 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 00Z TAFS THROUGH NOON MONDAY)
ISSUED AT 529 PM MDT SUN AUG 17 2014

VFR CONDITIONS THROUGH TONIGHT AND INTO EARLY MONDAY WITH A DRY AIR
MASS OVER MOST OF THE AREA. CURRENTLY WATCHING AN AREA OF TSTORMS
SOUTH OF RAPID CITY...PUSHING SOUTHEAST TOWARDS NEBRASKA. THIS AREA
OF THUNDERSTORMS SHOULD REMAIN EAST OF KCDR AND KAIA THIS
EVENING...SO KEPT VCTS OUT OF THE TAF FOR NOW. OTHERWISE...A WEAK
SURFACE COOL FRONT WILL MOVE SOUTH ACROSS WY AND NEBRASKA TONIGHT
RESULTING IN WINDS SHIFTING INTO THE NORTH BUT REMAINING LIGHT.
THERE IS A HIGHER CHANCE OF SHOWERS AND TSTORMS MONDAY AFTERNOON
ACROSS SOUTHEAST WYOMING...MAINLY IN THE MOUNTAINS.

&&

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

NORTHWEST WINDS GUSTS OF 25 TO 35 MPH COMBINED WITH RELATIVE
HUMIDITIES 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...TJT
FIRE WEATHER...JAMSKI







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