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000
FXUS65 KCYS 260449
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1049 PM MDT SAT MAY 25 2013

.UPDATE...
ISSUED AT 617 PM MDT SAT MAY 25 2013

SHOWERS AND THUNDERSTORMS HAVE NOT BEEN VERY NUMEROUS OVER THE
CWA LATE THIS AFTERNOON AND EARLY THIS EVENING. POTENTIAL STILL
EXISTS OVER THE PANHANDLE THIS EVENING FOR STRONG OR EVEN SEVERE
STORMS...ESPECIALLY THE NORTHERN PORTION. THAT AREA IS AHEAD OF
A SURFACE BOUNDARY CURRENTLY ALONG THE EASTERN WYOMING BORDER.
AHEAD OF THE BOUNDARY STILL EXISTS MOIST AND UNSTABLE AIR WITH
CAPE VALUES BETWEEN 1000 AND 2000 J/KG/. MINIMAL THUNDERSTORM
COVERAGE EARLY THIS EVENING MAY BE DUE TO THE PERSISTENT CIRRUS.
ALSO...THE LOW LEVEL THETA RIDGE AXIS BEING EAST OF THE CWA...
EXCEPT FOR THE FAR NORTHERN PANHANDLE. IN A RECENT UPDATE MADE
SOME ADJUSTMENTS TO THE POPS AND CLOUDS. WILL TAKE A LOOK SOON AT
THE POSSIBILITY OF LOW CLOUDS AND FOG REDEVELOPING OVER PARTS OF
THE PANHANDLE LATER TONIGHT.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 230 PM MDT SAT MAY 25 2013

VISIBLE SATELLITE LOOP SHOWS PARTLY CLOUDY SKIES WITH CONVECTION
JUST STARTING TO INITIATE NEAR THE NEBRASKA BORDER THIS AFTERNOON.
RELATIVELY QUIET RIGHT NOW WITH ONLY SOME VIRGA SHOWING UP ON
RADAR. SURFACE BOUNDARY/DRYLINE FEATURE JUST WENT THROUGH KIMBALL
NEBRASKA INDICATIVE OF THE SURFACE DEWPOINT DROP BY 7C IN ONLY A
HALF AN HOUR AND WINDS SHIFTED INTO THE SOUTHWEST. THIS BOUNDARY
IS LOCATED NEAR KIMBALL AND EXTENDS NORTHWEST TO NEAR GUERNSEY
WYOMING...AND FURTHER NORTH TO AROUND THE DOUGLAS AREA. THIS
BOUNDARY WILL CONTINUE TO MOVE SLOWLY EAST THIS AFTERNOON.
DEWPOINTS AHEAD OF THIS BOUNDARY ARE IN THE 50S TO NEAR 60 INTO
WESTERN NEBRASKA WITH DEWPOINTS IN THE TEENS AND 20S WEST OF THE
BOUNDARY. PRETTY GOOD CONVERGENCE ALONG THIS BOUNDARY...AND WITH
AMPLE MOISTURE AHEAD OF IT...THERE IS CONCERN FOR SEVERE
THUNDERSTORMS EAST OF A LINE FROM LUSK WYOMING TO SIDNEY NEBRASKA.
MODEL SOUNDINGS CONTINUE TO INDICATE LOW LI/S DOWN TO AROUND -7C
AND CAPE VALUES AROUND 2000 TO 2500 J/KG IN THESE AREAS WITH 30 TO
50 KNOTS OF SHEAR...ESPECIALLY OVER THE NORTHERN NEBRASKA
PANHANDLE. WILL CONTINUE TO MONITOR AND EVALUATE THE
ENVIRONMENT...WITH THE POTENTIAL OF A SEVERE TSTORM OR TORNADO
WATCH AFTER 3 PM THIS AFTERNOON.

FOR TONIGHT...THE SHORTWAVE RESPONSIBLE FOR THE STRONGER TSTORMS
WILL QUICKLY PUSH EAST OF THE FORECAST AREA LATE THIS EVENING.
THINK THE POTENTIAL FOR FOG IS A BIT LESS TONIGHT...BUT ADDED
PATCHY FOG TO LOCATIONS WHICH ARE MORE LIKELY TO SEE SOME RAINFALL
THIS EVENING. OTHERWISE...TEMPERATURES WILL REMAIN MILD TONIGHT.

FOR SUNDAY AND MONDAY...POTENTIAL FOR TSTORMS WILL SHIFT A BIT
FURTHER WEST DURING THE DAY AS ANOTHER SHORTWAVE TROUGH PUSHES
ACROSS SOUTHEAST WYOMING LATE IN THE DAY. HOWEVER...ANY SEVERE
WEATHER THREAT SHOULD SHIFT A LITTLE FURTHER NORTHEAST OVER
CENTRAL NEBRASKA AND SOUTHERN SOUTH DAKOTA. SIMILAR CONDITIONS ARE
EXPECTED ON MONDAY AS ANOTHER SHORTWAVE ALOFT TAKES A VERY SIMILAR
TRACK COMPARED TO SUNDAY...BUT THE SEVERE WEATHER THREAT WILL BE
EVEN LESS WITH DRIER NORTHWEST WINDS. TEMPERATURES WILL REMAIN
ABOVE NORMAL...BUT WILL LOWER A FEW DEGREES ON MONDAY.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 111 PM MDT SAT MAY 25 2013

TUESDAY...SIMILAR SOUTHWEST FLOW PATTERN ALOFT CONTINUES WITH WEAK
SHORTWAVES ROTATING NORTHEAST ACROSS OUR COUNTIES. SURFACE TROUGH
FORMS FROM CENTRAL WYOMING SOUTHEAST TO EASTERN COLORADO...ACTING AS
A FOCUS FOR ISOLATED TO SCATTERED AFTERNOON AND EVENING
THUNDERSTORMS...SOME STRONG TO POSSIBLY SEVERE.

WEDNESDAY...INITIAL NEGATIVELY TILTED SHORTWAVE TROUGH ALOFT ROTATES
ACROSS OUR COUNTIES AND WITH ADEQUATE LOW AND MID LEVEL
MOISTURE...EXPECT SCATTERED AFTERNOON AND EVENING THUNDERSTORMS
ALONG ITS ASSOCIATED SURFACE TROUGH AXIS.

THURSDAY...SLOW MOVING STACKED UPPER TROUGH LIES ACROSS WYOMING
PRODUCING WEST AND SOUTHWEST WINDS OVER OUR COUNTIES. OUR NORTHERN
AND WESTERN COUNTIES WILL BE CLOSE ENOUGH TO THE UPPER CIRCULATION
FOR SCATTERED LATE DAY SHOWERS AND THUNDERSTORMS...WHILE DOWNSLOPING
WINDS WILL LIMIT AREAL COVERAGE FROM WHEATLAND SOUTH TO COLORADO.

FRIDAY...WINDY AND COOL DAY AS THE MAIN SHORTWAVE TROUGH ALOFT
ROTATES TO OUR EAST...PRODUCING SCATTERED LATE DAY SHOWERS AND
THUNDERSTORMS NORTH OF A DOUGLAS TO SCOTTSBLUFF LINE...WITH
DOWNSLOPING WINDS PRODUCING A RAIN SHADOW EFFECT FURTHER SOUTH.

SATURDAY...LESSER AFTERNOON AND EVENING THUNDERSTORM COVERAGE AS A
WEAK SHORTWAVE RIDGE ALOFT PREVAILS...AND LOW AND MID LEVEL MOISTURE
WANES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY EVENING)
ISSUED AT 1043 PM MDT SAT MAY 25 2013

VFR FOR AIRPORTS ACROSS SOUTHEAST WYOMING WITH VERY DRY AIR IN
PLACE. A DRY LINE LAYS ALONG THE WYOMING/NEBRASKA BORDER THIS
EVENING AND SHOULD NOT MOVE MUCH OVER THE NEXT 12 TO 18 HOURS. EAST
OF THE LINE...COULD SEE LOWER CEILINGS TOWARDS 10Z WITH MOIST LOW
LEVEL AIR IN PLACE. WENT MVFR WITH CEILINGS AROUND 1500 FEET AT
KCDR AND KAIA. SREF AND HRRR SUPPORT THIS SOLUTION. THEY ALSO SHOW
LOWER CEILINGS POSSIBLY MAKING IT INTO THE KSNY AREA TOWARDS 12Z.
FOR NOW...KEPT THEM VFR AND WE WILL NEED TO MONITOR FOR THE 12Z
TAFS.

&&

.FIRE WEATHER...
ISSUED AT 135 PM MDT SAT MAY 25 2013

A SURFACE BOUNDARY SEPARATING MOIST UNSTABLE AIR TO THE EAST AND
DRY STABLE AIR TO THE WEST WILL EXTEND FROM NORTHEAST WYOMING TO
THE NEBRASKA PANHANDLE. THIS BOUNDARY WILL BE THE FOCUS FOR
THUNDERSTORM DEVELOPMENT THIS AFTERNOON AND EVENING...AND AGAIN
SUNDAY AFTERNOON. DRY CONDITIONS AND GUSTY WINDS WILL CONTINUE
ACROSS MAINLY CARBON AND ALBANY COUNTIES THIS WEEKEND...AND INTO
FAR EASTERN WYOMING BY MONDAY. TEMPERATURES WILL BE 10 TO 15
DEGREES ABOVE NORMAL THROUGH EARLY NEXT WEEK. DUE TO GREEN
FUELS...FIRE WEATHER CONCERNS REMAIN LOW.

&&

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

$$

UPDATE...WEILAND
SHORT TERM...TJT
LONG TERM...RUBIN
AVIATION...CLAYCOMB
FIRE WEATHER...TJT