Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 301554
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
954 AM MDT SUN AUG 30 2015

.UPDATE...
ISSUED AT 941 AM MDT SUN AUG 30 2015

MOSAIC RADAR IS SHOWING SHOWER ACTIVITY DEVELOPING ACROSS FAR
NORTHEAST UTAH AND FAR NORTHWEST COLORADO. ALSO A FEW SHOWERS NOW
SHOWING UP IN SOUTHCENTRAL WYOMING. THIS ACTIVITY WILL SPREAD EAST
ACROSS SOUTHEAST WYOMING THIS AFTERNOON ALONG WITH ISOLATED
THUNDERSTORMS. COOLING MID LEVELS OF THE ATMOSPHERE AND MID LEVEL
CONVERGENCE ASSOCIATED WITH SHORTWAVE TROUGH WILL BE A BIG FACTOR
IN SHOWERS AND THUNDERSTORMS...AS WELL AS THE RIGHT ENTRANCE
REGION OF THE UPPER LEVEL JET. THERE THREAT FOR SEVERE
THUNDERSTORMS IS LOW BUT WITH LARGE TEMPERATURE DEW POINT SPREADS
AND TYPICAL LATE AUGUST INVERTED V SOUNDING PROFILES...STRONG
WIND GUSTS WILL BE POSSIBLE WITH GUSTS TO AROUND 60 MPH NOT
COMPLETELY OUT OF THE QUESTION.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY NIGHT)
ISSUED AT 405 AM MDT SUN AUG 30 2015

SOME HIGH CLOUDS ARE MOVING OVERHEAD EARLY THIS MORNING WITH SOUTH-
SOUTHWEST WINDS ON AVERAGE OF 5 TO 15 MPH OBSERVED AT MANY
LOCATIONS. THE NEAR SFC INVERSION SEEMS TO BE STRONG ENOUGH TO KEEP
THE GUSTY LLVL JET WINDS AT BAY THO SO SHOULD SEE THESE LIGHTER
WINDS PERSIST THRU THE MORNING.

THE LEESIDE PRESSURE TROUGH WILL DEEPEN THIS MORNING AS A STRONG
UPPER LEVEL SHORTWAVE MOVES ACROSS THE PAC NW AND NORTHERN
ROCKIES TODAY. WEST-SOUTHWEST SFC WINDS ARE EXPECTED TO INCREASE
AS THIS OCCURS AND AS THE INVERSION BEGINS TO LIFT AFTER SUNRISE.
FORECAST SOUNDS SHOW A DEEP MIXED LAYER UP TO ROUGHLY 550 MB BY
THIS AFTERNOON...WITH WINDS THRU THE MIXED LAYER MAXING OUT AT 20
TO 25 KTS OVER THE MOUNTAINS AND EAST CENTRAL WYOMING...AND 10 TO
15 KTS TO THE LEE OF THE LARAMIE RANGE AND POINTS EAST.
THEREFORE...EXPECT GUSTY WINDS TO PERSIST THRU THE AFTERNOON
WITHIN A CORRIDOR FROM CARBON COUNTY TO CONVERSE/NIOBRARA COUNTIES
WHILE WINDS SHOULD DIMINISH WITHIN THE DEEPENING LEESIDE TROUGH
ACROSS EXTREME SOUTHEAST WYOMING AND THE WESTERN NEBRASKA
PANHANDLE. HOT TEMPS WILL OCCUR TODAY WITH 80S AND 90S ACROSS
SOUTHEAST WYOMING AND 90S AND PERHAPS A FEW 100 DEGREE READINGS
IN THE PANHANDLE WITH THE THERMAL RIDGE OVERHEAD. A FETCH OF
SUBTROPICAL MOISTURE WILL ADVECT UP AND INTO THE CWA TODAY AS WELL
AND WILL KEEP HUMIDITIES IN THE UPPER TEENS TO LOW 20S ALONG AND
WEST OF THE LARAMIE RANGE WITH MID TO UPPER TEENS ACROSS THE
PLAINS. STILL LOOKING AT THE BEST JUXTAPOSITION OF LOW HUMIDITIES
AND GUSTY WINDS EARLY THIS AFTERNOON ACROSS FWZ 301 SO WILL KEEP
THE RED FLAG WARNING IN PLACE HERE. WINDS SHOULD BE ON THE
DOWNWARD TURN FURTHER SOUTH AND EAST WHEN HUMIDITIES WILL BE AT
THEIR LOWEST SO LOOKING AT ONLY MARGINAL FIRE WEATHER CONCERNS
HERE FOR ZONES 309 AND 310.

SHOWERS AND ISOLATED TSTMS WILL DEVELOP OVER THE MOUNTAINS THIS
AFTERNOON WITHIN THE DEEPEST MOISTURE AND AS WINDS ALOFT INCREASE
WITH THE APPROACHING SHORTWAVE. STILL THINKING SOME OF THIS
ACTIVITY WILL SHIFT TO THE PLAINS THRU THE LATE AFTERNOON AND
EVENING AS THE MOISTURE PLUME CONTINUES TO OVERSPREAD THE CWA.
GUIDANCE CONTINUES TO SHOW ENOUGH MOISTURE TO PRODUCE MODEST
RAINFALL WITH MUCH OF THE ACTIVITY...AND INVERTED-V PROFILES
SUGGEST GUSTY AND ERRATIC WINDS ARE A HIGH LIKELIHOOD AS WELL.

WINDS TONIGHT COULD REMAIN A BIT BREEZY AHEAD OF THE COLD FRONT
THAT IS STILL PROGGED TO DROP SOUTH ACROSS THE REGION STARTING
AROUND SUNRISE ON MONDAY. COOLER TEMPS ARE EXPECTED FOR MONDAY
WITH INCREASING MOISTURE AND UPSLOPE FLOW PROGGED THRU THE
AFTERNOON ACROSS THE PLAINS. A WEAK DISTURBANCE MOVING OVERHEAD IN
SOUTHWEST FLOW SHOULD SPARK OFF MORE AFTERNOON TSTMS IN THE HIGH
COUNTRY AIDED BY STRENGTHENING UPSLOPE FLOW. ADDITIONAL WEAK
VORTICITY AND MOISTURE MOVING OVERHEAD ON THE NOSE OF A JETLET
APPROACHING FROM THE SOUTHWEST ON TUESDAY WILL BRING ANOTHER
ROUND OF SHOWERS/TSTMS TO THE CWA IN THE AFTERNOON.

.LONG TERM...(WEDNESDAY THROUGH SATURDAY)
ISSUED AT 405 AM MDT SUN AUG 30 2015

WE REMAIN UNDER A BROAD SOUTHWESTERLY FLOW ALOFT WEDNESDAY THROUGH
LATE WEEK AS A AMPLIFYING UPPER TROUGH OVER THE PACIFIC NORTHWEST
STARTS TO MOVE EASTWARD. WITH FAIRLY DRY DEEP LAYERED AIRMASS WE
SHOULD SEE LITTLE IN THE WAY OF POPS EXCEPT FOR MAYBE A FEW
ISOLATED AFTERNOON/EVENING STORMS IN THE MOUNTAINS OF SE
WYOMING...MAINLY ON WEDNESDAY. BY THE WEEKEND WE WILL SEE SEVERAL
STRONGER MIDLEVEL IMPULSES MOVE THROUGH THE INCREASING
SOUTHWESTERLY FLOW ALOFT AS THE UPPER TROUGH TO THE NORTHWEST
STARTS TO EJECT OUT TO THE EAST...AND THIS IS EXPECTED TO BRING A
WEAK COLD FRONT DOWN FROM THE NORTHWEST HANGING IT UP ALONG THE
LARAMIE RANGE ON SATURDAY. THIS MAY FOCUS SOME ISOLATED TO
SCATTERED AFTERNOON/EVENING THUNDERSTORMS OVER THE EASTERN HALF OF
THE FORECAST AREA SATURDAY AFTERNOON AND EVENING.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 537 AM MDT SUN AUG 30 2015

AXIS OF DEEPER MIDLEVEL PACIFIC MOISTURE BEING PULLED NORTHWARD
ALONG THE SOUTHERN STREAM JETSTREAK FROM SOUTHERN CALIFORNIA TO
MONTANA MOVING GRADUALLY EASTWARD INTO OUR WESTERN ZONES THIS
MORNING. THIS WILL RESULT IN THE DEVELOPMENT OF SCATTERED
THUNDERSTORMS AROUND RAWLINS AND LARAMIE THIS AFTERNOON SO HAVE
ADDED VCTS MENTION BY MID AFTERNOON FOR THOSE AIRPORTS...THEN AT
CHEYENNE BY EARLY EVENING WITH NO MENTION FARTHER EAST DUE TO THE
MORE ISOLATED COVERAGE OF STORMS AS THEY MOVE OUT ONTO THE PLAINS
BEFORE DIMINISHING. MOSTLY HIGH CIRRUS AT ALL AIRPORTS THIS
MORNING WITH SOUTHWESTERLY WINDS INCREASING BY LATE MORNING EXCEPT
MORE SOUTHERLY IN THE NEBRASKA PANHANDLE THROUGH THE AFTERNOON.


&&

.FIRE WEATHER...
ISSUED AT 405 AM MDT SUN AUG 30 2015

HOT AND RELATIVELY DRY CONDITIONS ARE EXPECTED TODAY OVER MUCH OF
THE DISTRICT...WITH BREEZY WINDS THIS MORNING CONTINUING THROUGH
THE AFTERNOON IN THE HIGH COUNTRY AND FOR CONVERSE/NIOBRARA
COUNTIES. WINDS LOOK TO DIMINISH ALONG AND EAST OF THE LARAMIE
RANGE AFTER NOON TODAY. THE RED FLAG WARNING REMAINS IN EFFECT
FOR FWZ 301 FOR THE COMBINATION OF DRY AND BREEZY CONDITIONS.
INCREASING MOISTURE LATER THIS MORNING AND AFTERNOON WILL GIVE
CHANCES FOR WETTING RAINS MAINLY OVER THE MOUNTAINS AND PLAINS OF
SOUTHEAST WYOMING. CHANCES FOR RAIN WILL CONTINUE OVER THE
MOUNTAINS AND SOUTHERN WYO PLAINS THRU TUESDAY.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR WYZ301.

NE...NONE.
&&

$$

UPDATE...SML
SHORT TERM...RJM
LONG TERM...JG
AVIATION...JG
FIRE WEATHER...RJM



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