Area Forecast Discussion
Issued by NWS Cheyenne, WY

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

000
FXUS65 KCYS 091747
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1147 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 18Z TAFS THROUGH 18Z THURSDAY MORNING)
ISSUED AT 1147 AM MDT WED APR 9 2014

IN ADDITION TO THE BREEZY AFTERNOON WINDS...THE MAIN AVIATION
IMPACT WILL FOCUS ON THE POTENTIAL FOR LOW STRATUS/FOG BEHIND THE
COLD FRONTAL PASSAGE LATE TONIGHT/EARLY THURSDAY. BEFORE THE
FRONT...WINDS WILL GUST TO BETWEEN 25 AND 35 KNOTS AT ALL SITES
THIS AFTERNOON. THE FRONTAL PASSAGE WILL OCCUR BETWEEN
00-06Z...TURNING WEST WINDS NORTHERLY IN ITS WAKE. COOLER...MORE
MOISTURE AND UPSLOPE FLOW BEHIND THE FRONT WILL SET THE STAGE FOR
AT LEAST THE POSSIBILITY OF MVFR CIGS/VSBYS BETWEEN 09-14Z.

&&

.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 UNTIL 7 PM MDT THIS EVENING FOR WYZ310.

NE...RED FLAG WARNING UNTIL 7 PM MDT THIS EVENING FOR NEZ311>313.

&&

$$

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





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.