Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 220941
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
341 AM MDT FRI AUG 22 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 340 AM MDT FRI AUG 22 2014

TODAY...FLOW ALOFT REMAINS SOUTHWEST...WITH ABUNDANT LOW LEVEL
MOISTURE ADVECTION ON LOW LEVEL SOUTHEAST WINDS. WITH A SHORTWAVE
TROUGH ALOFT ROTATING NORTHEASTWARD FROM COLORADO THIS
AFTERNOON... AND ADEQUATE LOW AND MID LEVEL MOISTURE...WILL SEE
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS THIS AFTERNOON AND
EVENING...WITH MOST COVERAGE IN PROXIMITY TO THE BEST LOW LEVEL
THETA-E ADVECTION NEAR THE COLORADO STATE LINE FROM LARAMIE TO
SIDNEY.

TONIGHT...SHORTWAVE TROUGH ROTATES NORTHEAST ACROSS OUR WESTERN
NEBRASKA COUNTIES...PRODUCING MORE WIDESPREAD SHOWERS AND
THUNDERSTORMS...POSSIBLY WITH HEAVY RAIN WITH NEAR SATURATED LOW
AND MID LEVELS AND WEAK STEERING FLOW ALOFT.

SATURDAY...UPPER TROUGH MOVES TO NORTHWEST WYOMING WITH A WEAK
SHORTWAVE TROUGH ALOFT MOVING ACROSS FAR EASTERN WYOMING ALONG
WITH ASSOCIATED COLD FRONT. LOOKS LIKE ENOUGH LOW AND MID LEVEL
MOISTURE FOR ISOLATED TO SCATTERED LATE DAY SHOWERS AND
THUNDERSTORMS... THOUGH LESS COVERAGE VERSUS TODAY.

SATURDAY NIGHT...DRIER AND MORE STABLE AIRMASS ADVECTS IN WITH
ISOLATED TO SCATTERED SHOWERS IN THE CYCLONIC FLOW ALOFT EAST OF
INTERSTATE 25.

SUNDAY...LOOKS LIKE A DRY AND WINDY DAY IN THE WAKE OF THE
SHORTWAVE TROUGH PASSAGE...WITH LOW AND MID LEVEL DRYING TAKING
PLACE WITH DECENT DOWNSLOPE WINDS UP TO 700 MB.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 340 AM MDT FRI AUG 22 2014

00Z MODEL OUTPUT CONTINUES TO SUGGEST THE UNSETTLED PATTERN EARLY
NEXT WEEK WILL DRY FOR WED-FRI. SO FOR MONDAY...MOIST SOUTHWEST
FLOW AHEAD OF POSITIVELY TILTED UPPER TROF WILL BE IN PLACE. AT
THE SFC...PRESSURE FALLS ALONG THE FRONT RANGE WILL PRODUCE
CONVERGENCE IN THE LLVLS. THE COMBINATION OF THE FAVORABLE
UPSLOPE/CONVERGENT SFC PATTERN COMBINED WITH THE APPROACH WILL SET
THE STAGE FOR DECENT PRECIP CHANCES...ESPECIALLY OVR THE ERN
PLAINS. MODEL PROGD SBCAPES OF 1500-1800 J/KG SUGGEST THAT AT
LEAST THE POTENTIAL EXISTS FOR A FEW STORMS TO BECOME MOST LIKELY
OVR THE WRN NEBRASKA PANHANDLE LATE IN THE DAY. TROF AXIS EDGES
CLOSER MONDAY NIGHT...LIKELY LINGERING CONVECTION. MEDIUM RANGE
MODELS BEGIN TO DIFFER SOME ON TUESDAY...AS THE ECMWF BEGINS TO
TREND SLOWER WITH THE TROUGH AXIS. EVEN SO...IT KEEPS THE TROUGH
AXIS OPEN...MORE IN LINE WITH WHAT THE RECENT GFS/GEM OUTPUT. ALL
MODEL SOLUTIONS SWEEP THE TROF AXIS THRU EITHER ON TUESDAY OR
TUESDAY NIGHT. THE ASSOCIATED COLD FROPA WILL OCCUR SOMETIME ON
TUESDAY...PENDING THE SPEED OF THE SYSTEM. TUESDAY WILL REMAIN
UNSETTLED...THOUGH THERMODYNAMIC PROFILE WILL BE LESS FAVORABLE
FOR ORGANIZED CONVECTION. TUESDAY STILL LOOKS LIKE THE COOLEST DAY
OF THE WEEK IN CAA BEHIND THE FRONT. A MUCH DRIER AIR MASS ALONG
WITH RIDGING BEGINS TO BUILD BACK IN TUESDAY NIGHT THROUGH FRIDAY.
LESS MOISTURE MEANS LESS CLOUD-COVER AND RISING HEIGHTS WILL ALLOW
TEMPS TO RETURN TO SEASONAL NORMS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 340 AM MDT FRI AUG 22 2014

RADARS SHOW SOME LIGHT SHOWER ACTIVITY STREAMING NORTHEAST OUT OF
NORTHEAST COLORADO THIS MORNING. THE TRAJECTORY WOULD STEER IT
TOWARDS KSNY...THOUGH OBSERVATIONS SHOW LITTLE IF ANY RAIN WAS
FALLING. OVERALL...EXPECT A VFR DAY AHEAD...THOUGH ISOLATED SHOWER
AND THUNDERSTORMS WILL BE A POSSIBLE FOR MOST SITES. NOT CONFIDENT
ENOUGH IN TIMING OR PLACEMENT TO ADD ANYTHING MORE THAN VCTS. THIS
ACTIVITY WILL LIKLEY LINGER THRU THE EVENING AND INTO THE
OVERNIGHT AT WRN NEBRASKA AIRFIELDS. MAY EVEN SEE A PERIOD OF
MVFR/IFR CIGS OR VISIBILITIES THERE THIS EVENING. ENOUGH
UNCERTAINTY REMAINS TO NOT INCLUDE IN THE TAFS YET. THERE SHOULD
BE A BRIEF BREAK BEHIND THIS ACTIVITY TOWARDS THE END OF THE TAF
PERIOD...HOWEVER MORE CONVECTION WILL BE ON ITS HEELS FOR
SATURDAY.

&&

.FIRE WEATHER...
ISSUED AT 340 AM MDT FRI AUG 22 2014

MINIMAL CONCERNS AS THE WINDS AND HUMIDITIES REMAIN BELOW
CRITICAL THRESHOLDS.

&&

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

&&

$$

SHORT TERM...RUBIN
LONG TERM...HAHN
AVIATION...HAHN
FIRE WEATHER...RUBIN




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