000
FXUS65 KCYS 161108
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
508 AM MDT SUN JUN 16 2013

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 500 AM MDT SUN JUN 16 2013

A FEW WEAK SHOWERS DEVELOPED OVER THE HIGH COUNTRY EARLY THIS MORNING
AHEAD OF A SHORTWAVE TROUGH MOVING TO THE NORTHWEST ACROSS THE GREAT
BASIN. A LINE OF SHOWERS AND ISOLATED STORMS DEVELOPED IN THE NORTHERN
PANHANDLE AS WELL ALONG WHAT LOOKS TO BE A WARM FRONT THAT IS MOVING
NORTH ACROSS THIS AREA. SHOULD SEE THIS ACTIVITY CONTINUE FOR THE
MOST PART THIS MORNING.

THE UPPER RIDGE AXIS WILL REMAIN OVER THE ROCKIES AS A SECOND UPPER
LEVEL WAVE WILL BEGIN TO DROP SOUTH INTO THE NORTHERN PLAINS THIS
AFTERNOON. AN ASSOCIATED WEAK COOL FRONT SLOWLY MOVING SOUTH ACROSS
THE FORECAST AREA EARLY THIS EVENING. FIRST THOUGH...A DEVELOPING
LEE SIDE TROUGH WILL MOVE SOUTHEAST ACROSS THE EASTERN PLAINS LATE
THIS MORNING AND AFTERNOON WITH SFC WINDS SHIFTING TO THE NORTH AND
THEN NORTHEAST THROUGH THIS TIME. TEMPERATURES WILL BE WARMER TODAY
THAN YESTERDAY AS A THERMAL RIDGE MOVES OVER THE FORECAST AREA AHEAD
OF THE COOL FRONT. WITH CONTINUED ENERGETIC AND MOIST SOUTHWEST FLOW
OVERHEAD IN ADDITION TO A NUMBER OF SFC FORCING MECHANISMS IN
PLACE...WILL SEE ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS ACROSS
THE FORECAST AREA TODAY. LOOKS TO BE A BROADER COVERAGE OF ACTIVITY
FOR TODAY THAN YESTERDAY WITH THE FOCUS FOR INITIATION ALONG THE
DEVELOPING LEE TROUGH IN ADDITION TO THE HIGHER TERRAIN FEATURES
THAT ARE THE MOUNTAINS AND CHEYENNE RIDGE. UPWARDS OF 2000 J/KG OF
CAPE WITH MINIMAL CAP ALONG AND EAST OF THE LARAMIE RANGE COMBINED
WITH 40 TO 50 KT OF DEEP LAYER SHEAR WILL INCREASE CHANCES ONCE
AGAIN FOR SOME OF THE STORMS TO ORGANIZE AND BECOME SEVERE. WITH
WEAK LOW LEVEL SHEAR AND HIGH LCLS IN PLACE DUE TO WARMER TEMPS OVER
THE MAJORITY OF THE REGION...THE MAIN THREATS WILL ONCE AGAIN BE
LARGE HAIL AND DAMAGING DOWNBURST WINDS. INCREASING LOW LEVEL
SHEAR AND LOWER LCLS LATE THIS AFTERNOON AHEAD OF THE LEE TROUGH
IN THE SOUTHERN NEBRASKA PANHANDLE WILL BRING A LOW POSSIBILITY
FOR AN ISOLATED TORNADO AS WELL. ALTHOUGH THE MAIN LIKELIHOOD OF
SEVERE POTENTIAL WILL BE EAST OF THE LARAMIE RANGE...CANNOT RULE
OUT A COUPLE STORMS APPROACHING SEVERE LIMITS OUT WEST ESPECIALLY
FOR DOWNBURST WINDS AS FORECAST SOUNDINGS IN THIS AREA SHOW A
PRONOUNCED INVERTED-V PROFILE BY LATE AFTERNOON. COULD SEE OVERALL
ACTIVITY LAST LONGER INTO THE NIGHT DEPENDING ON THE MOVEMENT OF
THE COOL FRONT AS IT PUSHES SOUTH ACROSS THE FORECAST AREA IN THE
LATE EVENING.

THE UPPER LEVEL RIDGE AXIS WILL REMAIN OVER THE ROCKIES AND WILL
AMPLIFY SLIGHTLY ON MONDAY AS THE NORTHERN SHORTWAVE FEATURE DIGS
INTO THE NORTHERN PLAINS. TEMPERATURES AT THE SURFACE AND ALOFT WILL
BE SLIGHTLY COOLER OVERALL BEHIND THE COOL FRONT...WHICH LOOKS TO
REMAIN STALLED ALONG THE LARAMIE RANGE THROUGH THE DAY.
EAST-SOUTHEASTERLY UPSLOPE WINDS BEHIND THE FRONT WILL INCREASE
MOISTURE ADVECTION AND WILL PROVIDE STRONG CONVERGENCE ALONG THE
LARAMIE RANGE. SO THE THREAT FOR SHOWERS AND THUNDERSTORMS WILL
CONTINUE FOR THE FORECAST AREA THROUGH MONDAY. SLIGHTLY COOLER TEMPS
ALOFT WILL REDUCE THE CAP IN THE AFTERNOON...SO ONCE AGAIN EXPECTING
SOME STORMS TO BECOME SEVERE ALONG AND EAST OF THE LARAMIE RANGE IN
THE AFTERNOON.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 500 AM MDT SUN JUN 16 2013

THE UPPER LEVEL PATTERN WILL BE DOMINATED BY RIDGING FROM THE
ROCKIES TO THE EASTERN GREAT PLAINS...WITH TROUGHS ANCHORED OVER
THE WESTERN AND EASTERN CONUS. THE MODELS CONTINUE TO BRING WEAK
UPPER LEVEL DISTURBANCES FROM THE GREAT BASIN UP AND OVER THE RIDGE
INTO THE GREAT PLAINS THROUGH THE EARLY PART OF THE WEEK. A SURFACE
DRY LINE OR TROUGH WILL BE QUASI-STATIONARY ACROSS THE EASTERN
WYOMING AND COLORADO PLAINS DURING THE SAME TIME PERIOD. MOIST
UNSTABLE AIR ALONG AND EAST OF THIS FEATURE WILL INTERACT WITH THE
DISTURBANCES TO PRODUCE MAINLY AFTERNOON AND EVENING CONVECTION.
TSTORM COVERAGE WILL GENERALLY BE SCATTERED EAST OF THE LARAMIE
RANGE...WITH MORE ISOLATED COVERAGE TO THE WEST. SOUTHERLY WINDS
WILL BE BREEZY TUESDAY...WITH MORE WIDESPREAD BREEZY CONDITIONS
ACROSS THE WESTERN PANHANDLE AND WEST OF THE LARAMIE RANGE FOR
WEDNESDAY. WEDNESDAY WILL BE DRY WITH THE UPPER RIDGE AND SUBSIDENT
FLOW OVER THE CWFA. A FRONT WILL PUSH SOUTH ACROSS THE HIGH PLAINS
LATE THURSDAY WITH WINDS SHIFTING FROM SOUTHERLY TO EASTERLY. A
LOW LEVEL MOISTURE AXIS WILL EXTEND FROM EAST CENTRAL WYOMING TO
THE WESTERN PANHANDLE FRIDAY AND SATURDAY. ISOLATED DIURNAL
CONVECTION WILL ONCE AGAIN DEVELOP ALONG AND EAST OF THIS BOUNDARY.

TEMPERATURES THROUGHOUT THE LONG TERM PERIOD WILL AVERAGE SEASONAL
NORMALS. WARMEST PERIOD WILL BE THE END OF THE WEEK WITH DRIER
SOUTHWEST FLOW IN PLACE AND 700MB TEMPERATURES FROM 14 TO 18C.
TEMPERATURES WILL COOL SLIGHTLY FOR THE WEEKEND AS HIGH PRESSURE
RIDGE BUILDS SOUTH THROUGH MONTANA AND WYOMING.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY EVENING)
ISSUED AT 1041 PM MDT SAT JUN 15 2013

EXPECTING FAIRLY CALM CONDITIONS OVERNIGHT. THE LATEST HRRR MODEL
IS SHOWING SOME IFR CEILINGS AT KSNY AND KCYS AROUND THE 09-10Z
TIME FRAME. GIVEN THE HIGH FALSE ALARM RATE WITH THE HRRR THE PAST
COUPLE WEEKS THOUGH...DECIDED TO GO AGAINST THIS GUIDANCE AND ONLY
HAVE SCT008 IN THE TAFS. ANOTHER ROUND OF CONVECTION SUNDAY
AFTERNOON WITH BEST CHANCES FOR TSTMS AT KCYS...KBFF AND KSNY.

&&

.FIRE WEATHER...
ISSUED AT 500 AM MDT SUN JUN 16 2013

A NUMBER OF WEATHER DISTURBANCES MOVING OVER THE DISTRICT THROUGH
EARLY THIS WEEK WILL MAINTAIN CHANCES FOR SHOWERS AND THUNDERSTORMS
THROUGH THIS TIME. ENOUGH MOISTURE LOOKS TO BE AVAILABLE FOR WETTING
RAINS OUT OF MOST STORMS...ALTHOUGH BREEZY SOUTHWEST WINDS AND
HUMIDITIES IN THE LOW TEENS ARE EXPECTED AGAIN TODAY FOR THE HIGH
COUNTRY WHICH COULD ATTRIBUTE TO LITTLE RAINFALL IN THIS AREA.
HUMIDITIES WILL REMAIN ON THE LOW SIDE OUT WEST FOR THE NEXT COUPLE
OF DAYS IN ADDITION TO BREEZY SOUTH TO SOUTHWEST WINDS.

&&

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

$$

SHORT TERM...RJM
LONG TERM...JAMSKI
AVIATION...CLAYCOMB
FIRE WEATHER...RJM