Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 252204
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
404 PM MDT MON AUG 25 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 404 PM MDT MON AUG 25 2014

VIGOROUS CONVECTION HAS DEVELOPED OVER THE SNOWY AND SIERRA MADRE
MOUNTAINS EARLY THIS AFTERNOON AHEAD OF A SHORTWAVE FEATURE MOVING
UP FROM SOUTHWESTERN CO. THE ENVIRONMENT HERE IS RELATIVELY UNSTABLE
WITH 500 TO 1000 J/KG OF SBCAPE ANALYZED ON MESOANALYSIS...WITH
LLVL LAPSE RATES OF 7 TO 8 C/KM. AS THE STORM NEAR LARAMIE EARLIER
ALREADY PRODUCE SMALL TO SEVERE SIZE HAIL...WOULD EXPECT ONE OR
TWO MORE STORMS TO ORGANIZE LIKE THIS THROUGH THE LATE
AFTERNOON...WITH THE MAJORITY OF STORMS PRODUCING MODERATE TO
HEAVY RAIN...SMALL HAIL...AND GUSTY WINDS THROUGH THE EVENING.
FURTHER EAST ACROSS THE PLAINS...EAST-SOUTHEASTERLY UPSLOPE FLOW
IS STRENGTHENING AHEAD OF THE UPPER WAVE WAVE...ALTHOUGH
INSTABILITY PARAMETERS ARE NOT TOO IMPRESSIVE. SO WOULD EXPECT THE
CONVECTION COMING OFF THE MOUNTAINS LATE THIS AFT AND EVENING TO
NOT BE AS VIGOROUS OVER THE PLAINS. STILL CANNOT RULE OUT GUSTY
WINDS AND SMALL HAIL AS THE APPROACHING SHORTWAVE WILL HELP
GENERATE STRONG UPDRAFTS AT TIMES THRU THIS EVENING. SHOULD SEE A
BREAK IN THE ACTIVITY LATE TONIGHT WITH ANOTHER ROUND OF SHOWERS
AND T-STORMS DEVELOPING IN THE LATE MORNING AND AFTERNOON TOMORROW
AHEAD OF A STRONGER WAVE EJECTING OUT AHEAD OF THE MAIN LOW
SITUATED OVER NV/UT. PERSISTENT SOUTHEASTERLY FLOW OVER THE PLAINS
WILL CONTINUE TO ADVECT IN HIGHER DEW POINTS THROUGH THE
DAY...WITH SBCAPE VALUES INCREASING TO BETWEEN 500 AND 1500 J/KG
THROUGH THE DAY. SHEAR WILL BE LESS THO...AND WILL AVERAGE AROUND
30 KTS ACROSS THE CWA. SO THERE WILL ONCE AGAIN BE POTENTIAL FOR
STRONG STORMS...ESPECIALLY IN THE EAST WITHIN THE RELATIVELY
UNSTABLE ENVIRONMENT WHERE A WEAK CAP IS IN PLACE...BUT LIKELY
WILL SEE LESS ORGANIZATION AND MORE VERTICAL UPDRAFTS WHICH WILL
LEND TO MORE A HEAVY RAIN AND SMALL HAIL TO MARGINAL SEVERE HAIL
THREAT.

THE MAIN UPPER LOW WILL MOVE INTO WESTERN COLORADO ON
WEDNESDAY...WITH MODELS INDICATING A GOOD DOSE OF MID LEVEL ENERGY
AND LOW-MID LEVEL CONVERGENCE SUPPORTING WIDESPREAD LIFT ACROSS THE
CWA. SO WILL MAINTAIN THE TREND UPWARD FOR POPS ACROSS THE AREA FOR
WEDNESDAY. NOT A WHOLE LOT OF INSTABILITY IS PROGGED DURING THIS
TIME...SO LIKELY TO BE A STEADY MODERATE RAINFALL WITH ANY FLOODING
POTENTIAL TO REMAIN LOCAL. TEMPERATURES WILL REMAIN BELOW NORMAL
THROUGH WEDNESDAY.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 404 PM MDT MON AUG 25 2014

WEDNESDAY NIGHT...SLOW MOVING UPPER TROUGH SLIDES ACROSS OUR
COUNTIES...WITH AT LEAST SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS PREVAILING WELL INTO THE EVENING HOURS...AND SCATTERED
SHOWERS AFTER MIDNIGHT.

THURSDAY...SHORTWAVE TROUGH MOVES SLOWLY INTO WESTERN NEBRASKA AND
WESTERN KANSAS WITH A MORE STABLE AIRMASS MOVING IN ACROSS OUR
COUNTIES AND ONLY SOME LEFTOVER SHOWERS AND THUNDERSTORMS IN THE
AFTERNOON FROM CHADRON TO KIMBALL TO CHEYENNE AND LARAMIE.

FRIDAY...LOW AND MID LEVELS DRY OUT AS RIDGING ALOFT DEVELOPS
OVERHEAD...THUS A DRY AND WARMER DAY ON TAP.

SATURDAY...THE DRY AND WARMER TEMPERATURES CONTINUE INTO LABOR DAY
WEEKEND AS FASTER SOUTHWEST FLOW ALOFT MOVES OVER MONTANA...INDUCING
SURFACE LEE TROUGHING OVER THE EASTERN SLOPES OF THE ROCKIES...AND
FURTHER DRYING OUT OUR LOW LEVELS.

SUNDAY...SOUTHWEST FLOW ALOFT STRENGTHENS AND WE MAY SEE ISOLATED
LATE DAY SHOWERS AND THUNDERSTORMS WITH A SLIGHT INCREASE IN LOW AND
MID LEVEL MOISTURE.

MONDAY...LOW AMPLITUDE SHORTWAVE TROUGH ALOFT MOVES ACROSS MONTANA
AND WYOMING...SENDING A COLD FRONT INTO OUR NORTHERN COUNTIES IN THE
AFTERNOON...AND WITH ADEQUATE LOW AND MID LEVEL MOISTURE...WE EXPECT
ISOLATED LATE DAY SHOWERS AND THUNDERSTORMS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY AFTERNOON)
ISSUED AT 404 PM MDT MON AUG 25 2014

VFR PREVAILS. ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS FROM 20Z TO 02Z...PRODUCING LOCALIZED
TURBULENCE...MVFR AND ERRATIC WIND GUSTS. 09Z TO 15Z...AREAS OF IFR
IN FOG AND LOW CLOUDS AT LARAMIE AND CHEYENNE AND WESTERN NEBRASKA
TAF SITES.

&&

.FIRE WEATHER...
ISSUED AT 404 PM MDT MON AUG 25 2014

A SERIES OF WEATHER SYSTEMS WILL BRING ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS TO THE DISTRICT TODAY THROUGH
WEDNESDAY. THE BEST CHANCE FOR WETTING RAINS WILL BE DURING THE
AFTERNOON AND EVENING HOURS...ALTHOUGH THE POSSIBILITY DOES EXIST
FOR SHOWERS TO CONTINUE THROUGH THE OVERNIGHT PERIOD. GUSTY WINDS
AND SMALL HAIL ARE POSSIBLE WITH THE STORM ACTIVITY AS WELL.
MINIMUM HUMIDITIES WILL REMAIN 30 PERCENT OR HIGHER THROUGH
WEDNESDAY...WITH DRIER AND WARMER WEATHER RETURNING THURSDAY
THROUGH FRIDAY AS HIGH PRESSURE BUILDS INTO THE AREA.

&&

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

$$

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






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