Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 172201 CCA
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
400 PM MDT WED SEP 17 2014

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 400 PM MDT WED SEP 17 2014

SCATTERED SHOWERS WITH A FEW EMBEDDED THUNDERSTORMS CONTINUE OVER
PORTIONS OF THE CWA THIS AFTERNOON...MAINLY ALONG THE INTERSTATE 80
AND 25 CORRIDORS. THE MAIN OUTFLOW BOUNDARY WITH THE INITIAL BURST
OF ACTIVITY EXTENDS FROM WESTERN KIMBALL COUNTY...SOUTH INTO
COLORADO...THEN BACK UP INTO SOUTHEAST ALBANY COUNTY. OBSERVED WINDS
WITH THIS FEATURE WERE AS HIGH AS 45 MPH EARLIER ON...WITH THE
STRONGEST ACTIVITY CURRENTLY LOCATED AT THE EASTERN AND WESTERN
EXTENTS OF THE BOUNDARY. COULD STILL SEE GUSTY WINDS AND BRIEF
MODERATE RAIN WITH THIS ACTIVITY...WHICH WILL SHIFT SOUTHEAST OVER
THE NEXT FEW HOURS. OTHERWISE...ISOLATED LIGHT RAIN SHOWERS WITH A
FEW CLAPS OF THUNDER WILL BE THE RULE ELSEWHERE THROUGH SUNSET.
WINDS ACROSS THE PLAINS ARE STILL EXPECTED TO BECOME A MORE
SOUTHEASTERLY UPSLOPE COMPONENT OVERNIGHT...WITH INCREASING LLVL
MOISTURE IN THIS PATTERN ENOUGH TO KEEP MENTION OF PATCHY FOG IN THE
EASTERNMOST ZONES OF NEBRASKA.

THE UPPER LEVEL RIDGE AXIS WILL MOVE OVERHEAD ON THURSDAY AS A DEEP
TROUGH DIGS INTO THE WEST COAST. TEMPS WILL INCREASE A FEW DEGREES
FROM TODAY...WITH 90S MORE WIDESPREAD IN THE LOWER ELEVATION OF THE
NEBRASKA PANHANDLE. WINDS WILL CONTINUE TO BE OUT OF THE SOUTH BUT
WILL BE LIGHT FOR THE MOST PART. A WEAK DISTURBANCE IN THE FLOW
COULD GENERATE A FEW SHOWERS OVER THE HIGH PEAKS...BUT LIKELY WILL
BE JUST SOME VIGOROUS CU OVER THE MOUNTAINS. THE UPPER TROUGH
LOOKS TO SPLIT THROUGH THURSDAY AND NIGHT...WITH THE NORTHERN
PIECE MOVING ACROSS THE NORTHERN ROCKIES ON FRIDAY. THE
ASSOCIATED COLD FRONT LOOKS TO MOVE ACROSS THE CWA EARLY FRIDAY
AFTERNOON ONCE AGAIN...WITH INCREASING CHANCES FOR SHOWERS AND
THUNDERSTORMS EXPECTED THROUGH THE DAY ALONG WITH COOLER
TEMPERATURES.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY )
ISSUED AT 400 PM MDT WED SEP 17 2014

MEDIUM RANGE MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A CLOSED UPPER
LOW OVER SOUTHERN CA EARLY IN THE PERIOD. THIS FEATURE IS NESTLED IN
BEHIND A HIGH AMPLITUDE UPPER RIDGE ANCHORED OVER THE ROCKY MOUNTAIN
REGION...LIKELY SLOWING ITS PROGRESS. SATURDAY AFTERNOON SHOULD BE A
PLEASANT DAY IN THE POST FRONTAL AIR WITH SEASONAL TEMPS AND PRECIP
CHANCES CONFINED TO THE MOUNTAINS. THE GFS/ECMWF BOTH MOVE THE UPPER
LOW NORTHEAST ACROSS THE GREAT BASIN ON SUN AFTN. MOISTURE INCREASES
IN THE 700-500 MILLIBAR LAYER AFTER 00Z OWING TO DIFFLUENT SOUTHWEST
FLOW ALOFT. CHANCES FOR PCPN SHOULD INCREASE FROM SW TO NE THROUGH
MON NIGHT...SO ONLY CHANGES TO THE INHERITED GRIDS WERE TO INCREASE
POPS SLIGHTLY. COOLEST DAY OF THE PERIOD SHOULD BE MON. LLVL UPSLOPE
FLOW IS PROGGED TO RAMP UP AS WELL WHICH SHOULD KEEP CLOUDS AND PCPN
GOING THROUGH THE DAY EAST OF THE LARAMIE RANGE...MUCH LIKE WE SAW
EARLIER THIS MONTH. GFS H7 TEMPS ARE ONLY IN THE SINGLE DIGITS C AND
ECM MOS SUGGESTS HIGHS ONLY IN THE LOWER 60S FOR SOUTHEAST WY. WE
LOWERED TEMPS BY A COUPLE OF DEGREES WITH THE EXPECTED SLOW PROGRESS
OF THE SYSTEM. WARMING AND DRYING TREND ENSUES THROUGH MIDWEEK WITH
PCPN ENDING BY TUE MORNING BENEATH UPPER-LEVEL RIDGING.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY MORNING)
ISSUED AT 1122 AM MDT WED SEP 17 2014

VFR CONDITIONS ARE EXPECTED TODAY. SHOWERS AND ISOLATED TSTMS ARE A
POSSIBILITY ALONG AND WEST OF THE LARAMIE RANGE AFTER 18Z WED. ADDED
VCTS TO TERMINALS AS FAR EAST AS KCYS. GUSTY AND ERRATIC SFC WINDS
ARE THE PRIMARY HAZARD FROM THIS ACTIVITY GIVEN THE DRY AIR IN THE
LOW LEVELS. SOUTH-TO-SOUTHEAST WINDS WILL BRING AMPLE MOISTURE INTO
THE WESTERN NE PANHANDLE LATE TONIGHT AND EARLY THU. PATCHY FOG AND
LOW CIGS MAY DEVELOP AFTER 09Z AND PERSIST THROUGH 15Z. MOST LIKELY
SITES FOR IFR CIGS OR VSBYS ARE KSNY AND KAIA. KBFF COULD ALSO SEE
SOME LOWER CLOUDS OR MINOR VSBY REDUCTIONS WITH LIGHT UPVALLEY FLOW
AROUND SUNRISE.

&&

.FIRE WEATHER...
ISSUED AT 400 PM MDT WED SEP 17 2014

SCATTERED SHOWERS WITH A FEW EMBEDDED THUNDERSTORMS WILL CONTINUE
THROUGH EARLY THIS EVENING FOR MUCH OF SOUTHEAST WYOMING. LIGHT
RAIN...GUSTY WINDS TO 40 MPH...AND OCCASIONAL LIGHTNING IS EXPECTED
WITH THE STRONGEST ACTIVITY WHICH WILL OCCUR ACROSS SOUTHERN ALBANY
COUNTY AND LARAMIE COUNTY. WARM AND DRY CONDITIONS WILL OCCUR ON
THURSDAY...WITH HUMIDITIES LOOKING TO DROP TO 15-25 PERCENT IN THE
AFTERNOON. WIND GUSTS WILL GENERALLY BE 20 MPH OR LESS THROUGH
THIS TIME. THE NEXT CHANCE FOR SHOWERS AND THUNDERSTORMS WILL
OCCUR FRIDAY...WITH TEMPERATURES COOLING TO MORE NORMAL VALUES
FOR THIS TIME OF YEAR THROUGH THE WEEKEND.

&&

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

$$

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









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