Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 262211
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
411 PM MDT TUE AUG 26 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 410 PM MDT TUE AUG 26 2014

A RELATIVELY THICK CIRRUS SHIELD CONTINUES TO MOVE OVER THE CWA IN
SOUTHWEST FLOW EARLY THIS AFTERNOON AHEAD OF THE STRONG UPPER LOW
CURRENTLY OVER EASTERN NEVADA. THE CIRRUS HAS MINIMIZED CONVECTION
OVER THE CWA SO FAR TODAY...HOWEVER THERE APPEARS TO BE SOME
THINNING OF THE CLOUDS OVER THE LAST TWO HOURS OR SO BASED OFF A
LOOP OF VIS IMAGERY. A WEAK PIECE OF ENERGY MOVING UP FROM THE
SOUTHWEST THIS AFTERNOON IS SPARKING OFF STORMS OVER THE MOUNTAINS
OF COLORADO...AND WILL INITIATE STORMS OVER THE SOUTHEAST WYOMING
MOUNTAINS AS WELL OVER THE NEXT FEW HOURS. IN ADDITION...A SFC LOW
CONTINUES TO DEEPEN ALONG THE LEE OF THE LARAMIE RANGE WITH SFC
WINDS SHIFTING IN RESPONSE TO THE DEVELOPING LOW. INCREASING LLVL
CONVERGENCE ALONG THE LARAMIE RANGE AND ADJACENT PLAINS IN THE
VCTY OF THE LOW WILL ACT AS AN ADDITIONAL INITIATION POINT...AND
WITH THE ENVIRONMENT EXPECTED TO BECOME INCREASINGLY UNSTABLE IN
THIS AREA WITHIN LVL MOISTURE ADVECTION AND AS CIRRUS DECREASES IN
COVERAGE...WILL SEE SHOWERS AND T-STORMS DEVELOP ACROSS THE PLAINS
THROUGH THE EVENING. MESOANALYSIS DATA SHOWS THAT SBCAPES HAVE
INCREASED TO BETWEEN 500 AND 2000 J/KG FROM WEST TO EAST ACROSS THE
CWA...WITH 30 KTS OF DEEP LAYER SHEAR IN PLACE. SO...SIMILAR TO
YESTERDAY...EXPECT VIGOROUS PULSE TYPE CONVECTION TO OCCUR WITH
THE HIGHEST LIKELIHOOD OF PRODUCING SMALL TO LOW END SEVERE SIZE
HAIL...STRONG DOWNDRAFT WINDS...AND HEAVY RAIN.

THE UPPER LOW WILL STEADILY SHIFT EAST ACROSS UTAH TONIGHT WITH A
STRONGER SHORTWAVE MOVING UP FROM THE SOUTHWEST AFTER MIDNIGHT IN
PERSISTENT SOUTHWEST FLOW. THEREFORE...AFTER A BRIEF BREAK IN
CONVECTION IN THE EARLY OVERNIGHT PERIOD...EXPECT A RESURGENCE OF
DEVELOPMENT THROUGH THE EARLY MORNING HOURS FROM SOUTH TO NORTH
ACROSS THE CWA. A PERIOD OF STRONG ISENTROPIC LIFT WILL OCCUR THRU
THIS TIME AS WELL WITH SOME ELEVATED INSTABILITY PROGGED BY THE
MODELS. MAINTAINED AT LEAST NUMEROUS SHOWERS WITH SOME EMBEDDED
THUNDERSTORMS IN THE FORECAST FOR THIS SCENARIO...WITH MODERATE TO
HEAVY RAIN A LIKELY BET OUT OF SOME OF THIS ACTIVITY AS NAM
FORECAST SOUNDINGS SHOWING A NEARLY SATURATED PROFILE THROUGH THE
MORNING. WILL HAVE TO WATCH CLOSELY FOR ANY CONVECTION THAT
BECOMES STATIONARY OVER TERRAIN FEATURES OR SFC BOUNDARIES AS THE
FLASH FLOOD THREAT COULD INCREASE SUBSTANTIALLY IN THESE AREAS. AT
THIS POINT THO...MOSTLY DRY ANTECEDENT CONDITIONS AND THE FACT
THAT THERE WILL BE SOME FLOW ALOFT PRECLUDES THE ISSUANCE OF ANY
FLOOD HIGHLIGHTS AT THIS TIME.

THE MAIN COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL SLIDE SOUTH
ACROSS THE EASTERN PLAINS WEDNESDAY AFTERNOON...SO THE THREAT FOR
NUMEROUS SHOWERS AND THUNDERSTORMS WILL CONTINUE THRU THE DAY.
OVERALL INSTABILITY WILL BE LESS...BUT WILL AGAIN HAVE TO KEEP A
CLOSE EYE FOR HEAVY RAIN PRODUCERS AND POTENTIAL FLOODING
CONCERNS AS THE FRONT ROLLS ON THROUGH. MUCH DRIER AIR AND OVERALL
WEAKER FORCING WILL MOVE OVERHEAD WEDNESDAY NIGHT AND THURSDAY AS
THE SYSTEM DEPARTS TO THE SOUTHWEST...WITH PERHAPS SOME LINGERING
SHOWERS AND STORMS OVER SOUTHERN PORTIONS OF THE CWA ON THURSDAY
IN WRAPAROUND FLOW.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 410 PM MDT TUE AUG 26 2014

THURSDAY NIGHT...WILL SEE ISOLATED EVENING SHOWERS AND THUNDERSTORMS
SOUTH OF A RAWLINS TO SIDNEY LINE WITH THE DEPARTING SHORTWAVE
TROUGH ALOFT...THEN DRY.

FRIDAY...NEXT PROGRESSIVE SHORTWAVE TROUGH ALOFT SCOOTS OVER THE
DAKOTAS...SENDING ITS ASSOCIATED COLD FRONT SOUTHWARD INTO OUR
COUNTIES DURING THE DAYLIGHT HOURS...AND SPARKING ISOLATED TO WIDELY
SCATTERED LATE DAY THUNDERSTORMS NORTH OF A RAWLINS TO ALLIANCE
LINE...WITH A FEW STORMS OVER THE SNOWY AND SIERRA MADRE RANGES AS
WELL...DRY ELSEWHERE. LATE DAY STORMS WILL BE MOST NUMEROUS ALONG
THE FAVORED UPSLOPE LOCALES FROM DOUGLAS TO LUSK.

SATURDAY...SURFACE LEE CYCLOGENESIS...LEE TROUGHING...DEVELOPS
ACROSS EASTERN MONTANA AND EASTERN WYOMING AS THE SOUTHWEST FLOW
ALOFT STRENGTHENS...AND WITH LIMITED LOW AND MID LEVEL
MOISTURE...THUNDERSTORMS APPEAR QUITE UNLIKELY. WILL BE A BREEZY AND
RELATIVELY WARM DAY FOR THE PENULTIMATE DAY OF AUGUST.

SUNDAY...FOR THE LAST DAY OF AUGUST...A DECENT PACIFIC ORIGIN COLD
FRONT WILL SLIDE EASTWARD ACROSS OUR COUNTIES...THOUGH WITH LIMITED
LOW AND MID LEVEL MOISTURE...SHOWER AND THUNDERSTORM COVERAGE WILL
BE ONLY ISOLATED TO WIDELY SCATTERED.

MONDAY...LABOR DAY...AND THE FIRST DATE OF SEPTEMBER WILL HAVE AN
AUTUMNAL FEEL IN THE WAKE OF THE COLD FRONT. SHOULD BE ENOUGH LOW
AND MID LEVEL MOISTURE FOR ISOLATED TO WIDELY SCATTERED LATE DAY
SHOWERS AND THUNDERSTORMS...AND WITH THE BRISK FLOW ALOFT...LOW
LEVEL GRADIENTS WILL LIKELY BE BRISK ENOUGH FOR A BREEZY TO WINDY
DAY AS WELL.

TUESDAY...ANOTHER FAST MOVING LOW AMPLITUDE SHORTWAVE TROUGH ALOFT
WILL MOVE ACROSS NORTHERN WYOMING AND THE DAKOTAS...SENDING A MOSTLY
DRY AUTUMNAL LIKE COLD FRONT ACROSS OUR COUNTIES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY MORNING)
ISSUED AT 1148 AM MDT TUE AUG 26 2014

THROUGH EARLY THIS EVENING...ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS DEVELOPING...MOST NUMEROUS FROM LARAMIE TO
CHEYENNE TO SIDNEY...PRODUCING LOCALIZED MVFR...TURBULENCE AND
ERRATIC WIND GUSTS TO 45 MPH...OTHERWISE VFR PREVAILS.

AFTER EARLY THIS EVENING...WIDESPREAD SHOWERS AND ISOLATED
THUNDERSTORMS ALONG WITH WIDESPREAD FOG AND LOW CLOUDS...ESPECIALLY
SOUTH OF A RAWLINS TO ALLIANCE LINE...PRODUCING IFR AND MOUNTAIN
OBSCUREMENT...WITH IFR PREVAILING AFTER MIDNIGHT THROUGH EARLY
MORNING WEDNESDAY.

CEILINGS AND VISIBILITIES GRADUALLY IMPROVING WEDNESDAY MORNING...
THOUGH WITH WIDESPREAD IFR AND MVFR SOUTH OF A RAWLINS TO
SCOTTSBLUFF LINE IN SHOWERS...LOW CLOUDS AND FOG. MOUNTAINS
OBSCURED.


&&

.FIRE WEATHER...
ISSUED AT 410 PM MDT TUE AUG 26 2014

A LOW PRESSURE SYSTEM WILL SLOWLY MOVE OVER THE INTERMOUNTAIN WEST
TONIGHT THROUGH THURSDAY...AND INTO THE GREAT PLAINS BY FRIDAY.
THIS SYSTEM WILL BRING PERIODS OF SHOWERS AND THUNDERSTORMS TO
THE DISTRICT THROUGH THIS TIME...WITH A GOOD CHANCE FOR WETTING
RAINS EXPECTED TONIGHT THROUGH WEDNESDAY. DRIER AND WARMER
CONDITIONS WILL THEN TAKE OVER ON THURSDAY AND WILL CONTINUE INTO
THE WEEKEND...WITH GUSTY WEST TO SOUTHWEST WINDS EXPECTED FOR MUCH
OF THE DISTRICT OVER THE WEEKEND.

&&

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

$$

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






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