Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 091037
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
437 AM MDT WED APR 9 2014

.SHORT TERM...(TODAY THROUGH THURSDAY NIGHT)
ISSUED AT 435 AM MDT WED APR 9 2014

A LOOP OF WATER VAPOR IMAGERY FROM EARLY THIS MORNING SHOWS AN UPPER
LEVEL RIDGE AXIS MOVING OVER THE FORECAST AREA WHILE AN UPSTREAM
SHORTWAVE MOVES ALONG THE US/CANADIAN BORDER. THE MSAS SURFACE CHART
SHOWS THE LEE SIDE PRESSURE TROUGH DEEPENING IN ADVANCE OF THIS
WAVE...AND WEST TO SOUTHWEST WINDS HAVE REMAINED ON THE BREEZY SIDE
OVERNIGHT ALONG AND WEST OF INTERSTATE 25 AS A RESULT. GUSTS OF 30
TO 40 MPH HAVE BEEN COMMON IN THIS AREA...ESPECIALLY NEAR ARLINGTON
AND IN THE SOUTHERN LARAMIE RANGE AND FOOTHILLS.

THESE DRY DOWNSLOPE WINDS WILL REMAIN IN PLACE TODAY AS THE UPPER
WAVE MOVES EAST ACROSS THE NORTHERN ROCKIES AND INTO THE CENTRAL
PLAINS. EXPECTING GUSTS OF 50 TO 55 MPH IN THE TYPICAL WINDY AREAS
OF SOUTHEAST WYOMING AS THE GRADIENT IS EXPECTED TO REMAIN STRONG
AND FORECAST SOUNDINGS SHOW DEEP MIXING UP TO AROUND 650 MB WHERE
WINDS SHOULD BE AROUND 45 KT. 30 TO 40 MPH GUSTS ARE EXPECTED
ELSEWHERE AS FORECAST SOUNDINGS SHOW WINDS AT THE TOP OF THE MIXING
LEVEL TO AVERAGE AROUND 35 KT IN THESE AREAS. SOUNDINGS ALSO SHOW
THE BOUNDARY LAYER TO BE VERY DRY THIS AFTERNOON ESPECIALLY FOR THE
EASTERN PLAINS EVEN WITH SOME CLOUD COVER MOVING OVERHEAD IN THE
LATER AFTERNOON. SO UNDERCUT GUIDANCE ON HUMIDITIES AS THE MODELS
TYPICALLY ARE TOO HIGH ESPECIALLY WITH THE DRY DOWNSLOPE WINDS IN
PLACE. THE RED FLAG WARNING FOR FWZ 310-313 LOOKS TO BE IN GOOD
SHAPE AS A RESULT...WITH HUMIDITIES PROGGED TO DROP INTO THE LOW
TEENS FOR MUCH OF THE AFTERNOON WITH WINDS GUSTING 30 TO 40 MPH. BY
LATE AFTERNOON...VERY WARM TEMPS IN THE 60S AND 70S WILL COMBINE
WITH INCREASING MID LEVEL MOISTURE TO DESTABILIZE THE ATMOSPHERE
OVER MUCH OF THE CWA. THE COLD FRONT ASSOCIATED WITH THE UPPER WAVE
WILL APPROACH FROM THE NORTH THROUGH THE LATE AFTERNOON...AND WILL
PROVIDE SOME FOCUS FOR AT LEAST ISOLATED TSTORMS IN NORTHERN
PORTIONS OF THE CWA. IN ADDITION...OROGRAPHIC FORCING WILL ALSO
LIKELY INITIATE A FEW STORMS IN WESTERN PORTIONS OF THE CWA. MODELS
LOOK TO BE TRENDING SLIGHTLY FURTHER SOUTH WITH THE MID LEVEL
MOISTURE PLUME WITH THE MAIN TRIGGER FOR CONVECTION IN THIS AREA
LOOKING TO BE THE SOUTHERN LARAMIE RANGE. MAINTAINED LOW POPS IN
THIS AREA THO AS THE OVERALL MOISTURE CONTENT LOOKS TO REMAIN LOW
DUE TO THE DRY DOWNSLOPE FLOW AND SO AM NOT EXPECTING MUCH
SHOWER/STORM ACTIVITY AS A RESULT.

THE COLD FRONT WILL SLIDE SOUTH ACROSS THE EASTERN PLAINS THROUGH
THE EVENING WITH INCREASING CHANCES FOR SHOWERS MAINLY IN THE
NORTHERN HALF OF THE CWA THROUGH THE EVENING WHERE THE DEEPEST
MOISTURE WILL BE PRESENT WITHIN THE MID LEVEL BAROCLINIC BAND. SOME
PATCHY FOG IS POSSIBLE ALONG AND JUST TO THE EAST OF THE LARAMIE
RANGE AS THE FRONT STALLS HERE OVERNIGHT AND WINDS VEER TO A
NORTHEAST UPSLOPE FETCH BEHIND THE FRONT. THE NEXT UPPER LEVEL
SHORTWAVE WILL APPROACH FROM THE NORTHWEST ON THURSDAY MORNING AND
WILL PUSH THE FRONT BACK EASTWARD THROUGH THE DAY. ALTHOUGH TEMPS
WILL BE SLIGHTLY COOLER FOR THURSDAY...MORE MOISTURE LOOKS TO BE
AVAILABLE FOR SHOWERS AND TSTORMS IN THE AFTERNOON ESPECIALLY
ALONG THE PROGRESSIVE FRONT. EXPANDED CHANCE POPS TO INCLUDE MORE
OF THE EASTERN PLAINS WITH THE TSTORM THREAT REMAINING AN ISOLATED
THREAT. WINDS ALONG AND WEST OF THE LARAMIE RANGE WILL INCREASE
ONCE AGAIN AS THE SURFACE PRESSURE GRADIENT INCREASES DUE TO THE
EASTWARD TREK OF THE FRONT...WITH GUSTS OF 45 TO 50 MPH LIKELY
THROUGH THE AFTERNOON. CONVECTION WILL DIMINISH QUICKLY THROUGH
THE EVENING AS THE UPPER WAVE TREKS EASTWARD ALONG WITH THE
SURFACE FRONT.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 400 AM MDT WED APR 9 2014

DRY...WINDY AND UNSEASONABLY MILD WEATHER FRIDAY UNDER INCREASING
ZONAL FLOW ALOFT AS SHORTWAVE ENERGY PROGRESSES SOUTHEAST THROUGH
THE NORTHERN ROCKIES AND PLAINS. HIGH TEMPERATURES IN THE 60S TO
MID 70S CAN BE EXPECTED EAST OF THE LARAMIE RANGE. 00Z ECMWF AND
GFS ARE IN BETTER AGREEMENT WITH A DIGGING TROUGH WEST OF THE
CONTINENTAL DIVIDE THIS WEEKEND. CANADIAN AIR SURGES SOUTHWARD
SATURDAY NIGHT AND SUNDAY IN ADVANCE OF THE TROUGH...WITH
OVERRUNNING MOISTURE SETTING THE STAGE FOR WIDESPREAD RAIN AND
SNOW SHOWERS. SIGNIFICANT SNOW ACCUMULATIONS WILL BE POSSIBLE OVER
THE HIGHER TERRAIN WITH LESSER AMOUNTS FOR THE HIGH PLAINS. AFTER
HIGHS IN THE 50S AND 60S SATURDAY...IT WILL BE ABOUT 25 DEGREES
COLDER SUNDAY. BRISK NORTHERLY WINDS WILL PRODUCE WIND CHILLS IN
THE TEENS AND 20S.

THE UPPER TROUGH SHIFTS SOUTHEAST OF THE CWA SUNDAY NIGHT WITH
PRECIPITATION ENDING. UPPER RIDGE TRANSLATES EAST FROM THE GREAT
BASIN ACROSS THE FRONT RANGE AND HIGH PLAINS MONDAY AND MONDAY
NIGHT. MOISTURE INCREASES TUESDAY IN ADVANCE OF THE NEXT UPPER
TROUGH MOVING THROUGH THE PACIFIC NORTHWEST AND NORTHERN ROCKIES.
700MB TEMPERATURES MODERATE FROM -3C MONDAY TO 3C TUESDAY. HIGHS
IN THE 40S TO AROUND 50 MONDAY WARM TO THE 50S TO AROUND 60 TUESDAY.
BREEZY TO WINDY CONDITIONS RETURN TO SOUTHEAST WYOMING EARLY NEXT
WEEK WITH THE PRESENCE OF A LEE SIDE SURFACE TROUGH.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 300 AM MDT WED APR 9 2014

WEST TO SOUTHWEST WINDS WILL INCREASE EARLY THIS MORNING WITH
WINDY CONDITIONS THROUGH THE DAYLIGHT HOURS. GUSTS OF 25 TO 40
KT WILL PREVAIL DURING THE AFTERNOON. EXPECT VFR CONDITIONS WITH
INCREASING HIGH CLOUDS TODAY. A COLD FRONT WILL MOVE SOUTH ACROSS
THE HIGH PLAINS TONIGHT WITH WIDELY SCATTERED RAIN AND SNOW SHOWERS
OVER EAST CENTRAL WYOMING AND NORTHERN NEBRASKA PANHANDLE. A FEW
WEAK TSTORMS WILL BE POSSIBLE AS WELL. CEILINGS WILL LOWER TO
BETWEEN 5000 AND 10000 FT AGL TONIGHT. MOIST UPSLOPE AIR WILL LEAD
TO LATE NIGHT PATCHY FOG DEVELOPMENT EAST OF THE LARAMIE RANGE WITH
MVFR CEILINGS AND VISIBILITIES POSSIBLE.

&&

.FIRE WEATHER...
ISSUED AT 435 AM MDT WED APR 9 2014

A RED FLAG WARNING REMAINS IN EFFECT FOR ZONES 310 TO 313 FROM 10
AM TO 7 PM TODAY FOR MINIMUM AFTERNOON HUMIDITIES EXPECTED TO FALL
INTO THE LOW TEENS COMBINING WITH WESTERLY DOWNSLOPING WINDS OF 30
TO 40 MPH. THERE IS ALSO A SLIGHT CHANCE FOR LIGHT RAIN AND ISOLATED
TSTORMS THIS AFTERNOON MAINLY IN NORTHERN AND WESTERN ZONES. A
BETTER CHANCE FOR MORE MORE WIDESPREAD SHOWERS AND STORMS IS
EXPECTED THURSDAY AFTERNOON.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...RED FLAG WARNING FROM 10 AM THIS MORNING TO 7 PM MDT THIS
     EVENING FOR WYZ310.

NE...RED FLAG WARNING FROM 10 AM THIS MORNING TO 7 PM MDT THIS
     EVENING FOR NEZ311>313.

&&

$$

SHORT TERM...MAZUR
LONG TERM...JAMSKI
AVIATION...JAMSKI
FIRE WEATHER...MAZUR





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