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000
FXUS65 KCYS 141136
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
536 AM MDT FRI JUN 14 2013

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 531 AM MDT FRI JUN 14 2013

GUSTY WEST-TO-NORTHWEST WINDS HAVE DEVELOPED ALONG AND WEST OF THE
LARAMIE RANGE THIS MORNING AS A STRONG PACIFIC FRONT MOVES EASTWARD
ACROSS THE CWA. MSAS PRESSURE ANALYSIS SHOWS FAIRLY STRONG PRESSURE
RISES IN THE WAKE OF THIS FEATURE...NEAR 4 MB PER 3 HOURS ENTERING
WESTERN CARBON COUNTY AS OF 10Z. AREA OBSERVATIONS HAVE INDICATED A
FEW WIND GUSTS AROUND 45 MPH IN WIND PRONE AREAS NEAR ARL...BUT FOR
THE MOST PART WINDS HAVE REMAINED BELOW 35 MPH. THE REST OF THE CWA
SHOULD SEE A TEMPORARY INCREASE IN SFC WINDS...AS WELL A WIND SHIFT
TO WNW AS THE FRONT CONTINUES TO PROGRESS EWD. A SEPARATE AREA OF
LOCALLY STRONGER WINDS HAS ALSO DEVELOPED OVER OUR PANHANDLE ZONES
ASSOCIATED WITH ENHANCED NEAR-SFC FLOW BENEATH A STRONG NOCTURNAL
LLVL JET. AFOREMENTIONED PACIFIC FRONT WILL KEEP SFC WINDS ELEVATED
THROUGH THE AFTN HOURS...BUT LLVL JET ENHANCEMENT SHOULD END BY MID
MORNING. ASIDE FROM WINDS...THE ONLY OTHER NEAR TERM CONCERN WILL
BE LOW STRATUS ENTERING THE NORTHERN CWA PER RECENT INFRARED SAT
IMAGERY. THE 06Z NAM APPEARS TO HAVE A VERY GOOD HANDLE WITH LLVL
MOISTENING ACROSS THOSE AREAS...SO HAVE INCREASED CLOUD COVER AND
LOWERED FCST HIGHS A COUPLE OF DEGREES OVER CONVERSE AND NIOBRARA
COUNTIES. NAM BUFKIT SHOWS A DECREASE IN LLVL SATURATION BY MID TO
LATE MORNING...AT WHICH POINT CLOUDS SHOULD SCATTER OUT.

WATER VAPOR SATELLITE LOOP SHOWS A STRONG MIDLVL SHORTWAVE TROUGH
TRACKING ACROSS THE INTERMOUNTAIN WEST. MODELS BRING THIS FEATURE
EASTWARD ALONG THE WYOMING AND MONTANA STATE LINE THROUGH THE AFTN
AND EVE HOURS...ALONG WITH SEVERAL WEAKER PIECES OF MIDLVL ENERGY
EMBEDDED WITHIN SOUTHWESTERLY FLOW ALOFT OVER SOUTHEAST WY AND
NORTHERN CO. GFS AND ECMWF ARE BOTH IN GOOD AGREEMENT WITH STRONG
UPPER-LEVEL DIVERGENCE IN THE RIGHT ENTRANCE REGION OF A 100+ KT
H25 JET...MAINLY EAST OF THE LARAMIE RANGE AFTER 00Z SAT. THIS
OCCURS ALONGSIDE INCREASING LLVL CONVERGENCE ALONG AN ELEVATED
WARM FRONT DRAPED FROM NORTH TO SOUTH ACROSS FAR EASTERN WY. AN
INCREASE IN 700-300 MILLIBAR MOISTURE ABOVE UPPER 40S AND LOWER
50S SFC DEWPOINTS LENDS CREDENCE TO MODEL FCST QPF OVER THE EAST
HALF OF THE CWA BETWEEN 00Z AND 12Z SAT. AIR MASS WILL LIKELY BE
CAPPED TO SFC BASED PARCELS...BUT WITH RESPECTABLE ELEVATED CAPE
AND SHOWALTER INDICES AS LOW AS -4C WOULD EXPECT AT LEAST A FEW
ELEVATED SHOWERS AND TSTMS GIVEN DYNAMICS IN PLACE. SOME OF THIS
ACTIVITY COULD CONTINUE WELL INTO THE NIGHT. AS SUCH...CONTINUED
TO MENTION SLIGHT CHANCE POPS THROUGH THE PERIOD.

MOIST UPSLOPE FLOW RETURNS TO AREAS ALONG AND EAST OF THE LARAMIE
RANGE ON SAT...LIKELY SETTING THE STAGE FOR ANOTHER ROUND OF TSTM
ACTIVITY OVER THE HIGH PLAINS. LLVL CONVERGENCE AND MIDLVL COOLING
ASSOCIATED WITH A 700 MILLIBAR SHORTWAVE SHOULD BE SUFFICIENT TO
OVERCOME ANY SURFACE-BASED INHIBITION...BUT WILL HAVE TO WATCH OUT
FOR UPSLOPE-DRIVEN STRATUS EARLY IN THE DAY WHICH COULD LIMIT SFC
HEATING AND RESULT IN A SIGNIFICANT CAP. THE GFS AND NAM ARE WORLDS
APART...WITH THE GFS BREAKING OUT CONVECTION BY MID AFTN AND THE
NAM STRUGGLING TO INITIATE ANYTHING AT ALL WITH AT LEAST 150 J/KG
OF SBCIN. ASSUMING TSTMS DEVELOP...AIR MASS WILL BE VERY STRONGLY
SHEARED WITH 50 TO 60 KTS IN THE 0 TO 6 KM LAYER OWING TO EASTERLY
LLVL FLOW VEERING TO WESTERLY AROUND 700-500 MILLIBARS. THE LLVLS
WILL NOT BE PARTICULARLY MOIST...WITH DEWPOINTS ONLY IN THE UPPER
40S AND LOW 50S. BUT...STEEP MIDLVL LAPSE RATES SHOULD CONTRIBUTE
TO ABOUT 1000-2000 J/KG OF SBCAPE. SUPERCELLS CAPABLE OF PRODUCING
AT LEAST LARGE HAIL AND DAMAGING WINDS ARE POSSIBLE...AND THE SPC
HAS OUR SOUTHEAST ZONES IN A SLGT RISK FOR DAY 2. COULD NOT RULE
OUT A TORNADO OR TWO IN THIS SCENARIO AS WELL GIVEN SUBSTANTIAL
VEERING IN THE LOW LEVELS...BUT WOULD LIKE TO SEE STRONGER SPEED
SHEAR FOR A MORE WIDESPREAD TORNADIC THREAT.

STATUS QUO FOR SUN AS ANOTHER MIDLVL SHORTWAVE AND ASSOCIATED SFC
COLD FRONT SWEEP ACROSS THE AREA. LLVL CONVERGENCE AND MID LEVEL
DYNAMIC SUPPORT WOULD BE THE DRIVING FORCE FOR SHOWER AND TSTM
DEVELOPMENT...POSSIBLY BY LATE MORNING. CAPE AND SHEAR PROFILES
SHOULD ONCE AGAIN BE SUFFICIENT FOR SEVERE STORMS ON SUN AFTN
AND EVE. TEMPERATURES THROUGH THE PERIOD SHOULD BE NEAR OR A BIT
ABOVE SEASONAL NORMS. FRI SHOULD BE THE WARMEST DAY WITH H7 TEMPS
BETWEEN 12-15C CONTRIBUTING TO WIDESPREAD 80S TO NEAR 90F EAST OF
THE FOOTHILLS. OTHERWISE...LOOK FOR UPPER 70S AND LOW 80S THROUGH
THE WEEKEND ACROSS MOST AREAS OUTSIDE OF THE MOUNTAINS AND HIGH
VALLEYS.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 531 AM MDT FRI JUN 14 2013

SUNDAY NIGHT...NEXT WEAK COLD FRONT MOVES SOUTHWARD ACROSS OUR
COUNTIES. NAM AND GFS LOOK TOO BULLISH WITH QPF BASED ON MESOSCALE
AND SYNOPTIC PATTERNS AND TIME OF DAY CONSIDERATIONS...THUS WILL
HAVE ONLY ISOLATED SHOWER AND THUNDERSTORM CHANCES EAST OF THE
MOUNTAINS.

MONDAY...DECENT SETUP FOR ISOLATED TO SCATTERED AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS ALONG AND EAST OF THE INTERSTATE
25 CORRIDOR WITH SHORTWAVE RIDGING ALOFT AND WEAK NORTHWEST FLOW
ALOFT ALONG WITH UPSLOPE SOUTHEASTERLY WINDS AT LOW LEVELS ADVECTING
LOW LEVEL MOISTURE NORTHWESTWARD TO THE SPINE OF THE LARAMIE RANGE.

STEERING WINDS LOOK RELATIVELY LIGHT...THUS EXPECT SOME LOCALLY
HEAVY RAINERS ALONG WITH A FEW STRONG STORMS IN THE AFTERNOON AND
EVENING DUE TO ADEQUATE SHEAR AND INSTABILITY.

TUESDAY...RIDGE AXIS ALOFT MOVES OVERHEAD. WITH SOUTHEASTERLY
UPSLOPE LOW LEVELS ADVECTING MOISTURE NORTHWESTWARD AND MECHANICAL
LIFT AND TYPICAL DIURNAL HEATING AND DIFFERENTIAL HEATING EFFECTS...
EXPECT ISOLATED AFTERNOON AND EVENING THUNDERSTORMS ALONG AND EAST
OF THE LARAMIE RANGE.

WEDNESDAY...PAUCITY OF CONVECTIVE INITIATION EXPECTED IN THE
AFTERNOON AND EVENING DUE TO INVASION OF DRIER LOW AND MID LEVEL
AIR. COMBINED WITH LESS CLOUD COVER...WE WILL SEE WARMER
TEMPERATURES.

THURSDAY...NEGATIVELY TILTED SHORTWAVE TROUGHS ALOFT WILL ROTATE
NORTHEAST ACROSS WESTERN WYOMING AROUND AN UPPER LEVEL TROUGH OVER
THE PACIFIC NORTHWEST. WITH LIMITED LOW AND MID LEVEL MOISTURE AND
WARM MID LEVEL TEMPERATURES PROVIDING SIGNIFICANT CONVECTIVE
INHIBITION...CIN...WILL SEE LIMITED AREAL COVERAGE OF AFTERNOON AND
EVENING THUNDERSTORMS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 531 AM MDT FRI JUN 14 2013

VFR PREVAILS. SURFACE LOW PRESSURE WILL STRETCH AS A TROUGH FROM
WESTERN NORTH DAKOTA SOUTHWARD THROUGH WESTERN NEBRASKA AND TO
NORTHEAST COLORADO THIS MORNING WITH A COLD FRONT STRETCHING FROM
RAPID CITY TO CHEYENNE.

EVEN THOUGH A LOW LEVEL CONVERGENCE AXIS SETS UP FRIDAY AFTERNOON
OVER SOUTHEAST WYOMING...WITH LIMITED LOW AND MID LEVEL
MOISTURE...THUNDERSTORM INITIATION APPEARS UNLIKELY. SURFACE HIGH
PRESSURE DEVELOPS OVER NORTHERN WYOMING FRIDAY EVENING...PRODUCING
NORTH AND NORTHEAST WINDS OVER AERODROMES. ISOLATED THUNDERSTORMS
MAY ERUPT OVERNIGHT EAST OF INTERSTATE 25 AS A WEAK DISTURBANCE
MOVES OVERHEAD AND UPSLOPE DEVELOPS TO THE LARAMIE RANGE.

&&

.FIRE WEATHER...
ISSUED AT 531 AM MDT FRI JUN 14 2013

CHANCES FOR SHOWERS AND STORMS ARE EXPECTED TO INCREASE FROM LATE
FRIDAY AFTERNOON THROUGH THE WEEKEND. STRONG TO SEVERE STORMS ARE
POSSIBLE ALONG AND EAST OF THE LARAMIE RANGE ON SAT AND SUN...WITH
LARGE HAIL AND DAMAGING WINDS POSSIBLE. A STRONG PACIFIC FRONT WILL
MOVE ACROSS THE AREA ON FRI...BRINGING DRY AND BREEZY CONDITIONS TO
AREAS WEST OF THE LARAMIE RANGE. AFTERNOON RELATIVE HUMIDITY VALUES
WILL DROP AS LOW AS THE SINGLE DIGITS OVER WESTERN CARBON COUNTY
THROUGH THE WEEKEND ALONG WITH GUSTY WEST-TO-NORTHWEST WINDS. FUELS
ARE NOT CURRENTLY FAVORABLE FOR LARGE FIRE GROWTH...BUT SEVERAL DAYS
OF THESE CONDITIONS WILL CONTINUE TO DRY THINGS OUT AND MAKE FOR
NEAR CRITICAL FIRE WEATHER CONDITIONS.

&&

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

$$

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