Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 270025
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
625 PM MDT FRI SEP 26 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 330 PM MDT FRI SEP 26 2014

A BROAD HIGH AMPLITUDE UPPER RIDGE DOMINATED MUCH OF THE LOWER 48
WITH A DEEP TROUGH ACROSS THE FAR WEST. CLOUD COVER WAS LIMITED TO
THE HIGHER TERRAIN OF SOUTHEAST WY. WINDS EAST OF THE LARAMIE RANGE
WERE LIGHT AND VARIABLE. ALONG AND WEST OF THE LARAMIE RANGE IT WAS
BREEZY WITH WEST TO SOUTHWEST WINDS GUSTING TO 30 MPH. TEMPERATURES
WERE QUITE WARM WITH 80S TO LOWER 90S FOR THE VALLEYS AND PLAINS...
AND 60S AND 70S HIGHER ELEVATIONS.

SHORT RANGE MODEL CONSENSUS KEEPS THE INFLUENCE OF THE UPPER RIDGE
OVER THE CWA TONIGHT WITH MOSTLY CLEAR SKIES...MILD TEMPERATURES
AND LIGHT SOUTHERLY WINDS. SIMILAR TO LAST NIGHT...THE 850MB JET
INCREASES OVER NORTHWEST NEBRASKA WITH SOUTHERLY WINDS GUSTING TO
30 MPH DEVELOPING AFTER 03Z AND LASTING UNTIL AROUND 09Z.

SATURDAY WILL BE ANOTHER WARM AND BREEZY DAY FOR MUCH OF THE CWA
UNDER THE INFLUENCE OF THE UPPER RIDGE OVER THE EASTERN HALF OF
THE CONUS. THE UPPER TROUGH ENTERS THE GREAT BASIN SATURDAY
AFTERNOON...WITH A LARGE SWATH OF SUBTROPICAL MOISTURE STREAMING
NORTHWARD ACROSS THE INTERMOUNTAIN WEST. THE LEADING EDGE OF
THE MOISTURE WILL CREEP INTO CARBON COUNTY DURING THE AFTERNOON.
INSTABILITY AND UPSLOPE WILL RESULT IN WIDELY SCATTERED SHOWERS
AND TSTORMS...ALONG WITH SLIGHTLY COOLER TEMPERATURES IN THE 60S
AND 70S. 80S WILL PREVAIL FOR THE PLAINS. WITH THE RIDGE SLOW TO
EXIT EAST...SHOWERY PRECIPITATION WILL REMAIN WEST OF THE LARAMIE
RANGE SATURDAY NIGHT AND SUNDAY MORNING. AS THE RIDGE RELINQUISHES
ITS GRIP ON THE EASTERN CWA SUNDAY... SHOWERS AND ISOLATED TSTORMS
WILL SPREAD EAST ONTO THE PLAINS DURING THE AFTERNOON AND EVENING.
SUNDAY WILL BE 5 TO 10 DEGREES COOLER REGION-WIDE DUE TO GREATER
CLOUD AND PRECIPITATION COVERAGE. QPF AMOUNTS FOR THE 24 TO 60 HOUR
PERIOD WILL FALL BETWEEN 0,25 AND 0.50 INCHES...WITH 0.50 TO 1.0
INCH TOTALS POSSIBLE WITH THE HEAVIER SHOWERS.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 239 PM MDT FRI SEP 26 2014

THE MAIN CONCERN WITH THIS FORECAST PACKAGE IS THE POTENTIAL FOR
HIGH WIND HIGHLIGHTS ON TUESDAY.

MONDAY-MONDAY NIGHT:
MODELS ARE STILL SHOWING QUITE A BIT OF DIFFERENCES WITH REGARDS TO
CONTINUITY. THE GFS AGAIN IS CLOSING OFF THE UPPER LEVEL WAVE AS IT
LIFTS NORTHEAST OUT OF OUR FORECAST AREA TUESDAY. THE ONLY
DIFFERENCE FROM YESTERDAY`S RUN IS THAT IT SPINS UP THE CLOSED LOW
FURTHER NORTH INTO SOUTH DAKOTA. TODAY`S 12Z RUN OF THE GEM ALSO
SHOWS THE WAVE CLOSING OFF OVER SOUTH DAKOTA COMPARED TO YESTERDAY`S
RUNS WHICH KEPT IT AS AN OPEN WAVE. MEANWHILE...THE 00Z GFS RUN WAS
QUITE DIFFERENT AND DISPLAYED MORE OF AN OPEN WAVE SOLUTION WHICH IS
COMPARABLE TO THE ECMWF/UKMET SOLUTIONS. WE ARE STILL FAVORING THE
OPEN WAVE PATTERN AT THIS TIME...SINCE THE GFS OVERALL TRENDS OVER
THE PAST 10 DAYS HAVE BEEN FAVORING THIS SOLUTION AND THE ECMWF HAS
BEEN KEEPING THAT TREND AS WELL.

THIS WAVE SHOULD PROVIDE AN EXCELLENT TRIGGER FOR SHOWERS AND
THUNDERSTORMS TO DEVELOP ALONG THE LARAMIE RANGE MONDAY
AFTERNOON...DUE TO INFLUENCE OF THE JET MOVING IN FROM THE SOUTH
ALONG COMBINED WITH GOOD UPPER LEVEL DIFFLUENCE AND UPSLOPE FLOW. WE
DID BUMP UP PRECIPITATION CHANCES ON MONDAY AFTERNOON/EVENING MAINLY
EAST OF THE LARAMIE RANGE. SINCE WE ARE LOOKING AT AN OPEN WAVE
PATTERN...WE WOULD EXPECT THINGS TO MOVE THROUGH FAIRLY STEADY WITH
RAINFALL AMOUNTS GENERALLY ONE HALF INCH OR LESS. HOWEVER...IF THAT
SYSTEM DOES CLOSE OFF WE MAY BE LOOKING AT MORE RAINFALL IN THE
PANHANDLE.

TUESDAY-TUESDAY NIGHT:
THIS LOOKS TO BE A FAIRLY WINDY PERIOD WITH GOOD DOWNSCALE
SUBSIDENCE COMBINED WITH A GOOD STRATOSPHERIC INTRUSION ESPECIALLY
NEAR THE WY/CO BORDER. WE FOLLOWED MORE OF THE RAWBLEND MODEL
APPROACH WITH THE WIND SPEEDS SINCE IT TENDS TO DO BETTER IN THESE
SITUATIONS WITH EVEN GREATER WIND SPEEDS IN THE GAP REGIONS. WE
COULD HAVE A FEW LINGER SHOWERS ACROSS THE NORTHERN HALF OF THE AREA
DURING THE AFTERNOON...BUT THE BULK OF THE AREA SHOULD SEE DRY AND
WINDY CONDITIONS WITH GOOD DOWNSLOPE FLOW WHICH MAY HELP GIVE TEMPS
A BIT OF BOOST EAST OF THE LARAMIE RANGE. AT THIS POINT...WE ARE
FAVORING 60S AND 70S EAST OF THE LARAMIE RANGE.

WEDNESDAY-FRIDAY:
ECMWF IS SHOWING THE SIMILAR TRENDS TO YESTERDAY`S RUN OF BRINGING
THE CANADIAN AIR ON THURSDAY NIGHT INTO FRIDAY AS AN UPPER LEVEL
WAVE MOVES INTO THE NORTHERN PLAINS. MEANWHILE...THE GFS KEEPS THIS
SYSTEM FURTHER NORTH...AND IS NOT BRINGING NEAR THE AMOUNT OF COOL
AIR. WE ARE FAVORING TOWARDS A CONSENSUS APPROACH AT THIS TIME WHICH
WOULD KEEP US NEAR SEASONABLE NORMS WITH HIGHS GENERALLY IN THE 50S
AND 60S WITH ONLY A SMALL CHANCES OF RAIN.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY AFTERNOON)
ISSUED AT 625 PM MDT FRI SEP 26 2014

VFR CONDITIONS WILL CONTINUE THROUGH THE TAF PERIOD. SCT MID
LEVEL CLOUDS OCCURRING OVER THE MOUNTAINS AND NEARBY LOCATIONS OF
SOUTHEAST WYOMING WILL LIKELY CONTINUE THROUGH THE PERIOD...WITH
MOSTLY CLEAR SKIES PREVAILING FURTHER EAST. A FEW T-STORMS ARE
POSSIBLE IN THE FAR WEST INCLUDING KRWL LATE SATURDAY
AFTERNOON...WITH WINDS IN THIS AREA DIMINISHING BY 02Z THIS
EVENING AND REMAINING LIGHT THROUGH SATURDAY. FOR LOCATIONS IN
THE NORTHERN PANHANDLE...EXPECT SOUTH WINDS TO REMAIN BREEZY
THROUGH 09Z BEFORE EASING THROUGH THE EARLY MORNING HOURS.
ELSEWHERE...WINDS WILL BE LIGHT THROUGH MUCH OF SATURDAY...WITH
INCREASING SOUTHEASTERLY WINDS EXPECTED LATE SATURDAY AFTERNOON.

&&

.FIRE WEATHER...
ISSUED AT 300 PM MDT FRI SEP 26

WARM...BREEZY AND DRY CONDITIONS WILL CONTINUE THIS AFTERNOON WITH
MINIMUM HUMIDITIES OF 15 TO 25 PERCENT. SIMILAR CONDITIONS ARE
FORECAST FOR AREAS EAST OF THE LARAMIE RANGE SATURDAY...WITH
INCREASING CLOUD COVER AND HUMIDITY TO THE WEST. SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS WILL DEVELOP SATURDAY AFTERNOON ACROSS
MUCH OF CARBON COUNTY. THE PRECIPITATION WILL REMAIN WEST OF THE
LARAMIE RANGE SATURDAY NIGHT AND SUNDAY MORNING...THE SPREAD EAST
ONTO THE EASTERN PLAINS OF WYOMING SUNDAY AFTERNOON. IT WILL BE
MUCH COOLER SUNDAY ALONG AND WEST OF THE LARAMIE RANGE SUNDAY...
BUT STILL WARM TO THE EAST. IT WILL BR BREEZY ACROSS THE PLAINS
SUNDAY. MUCH OF NEXT WEEK WILL BE COOL AND SHOWERY.

&&

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

$$

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






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