000
FXUS65 KCYS 161747
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
1147 AM MDT THU MAY 16 2013

.UPDATE...
ISSUED AT 1137 AM MDT THU MAY 16 2013

CYS WSR-88D SHOWS WIDELY SCATTERED TSTORMS ERUPTING ALONG THE
BACK EDGE OF THE MID LEVEL SHORTWAVE MOVING ACROSS THE HIGH
PLAINS AT LATE MORNING. CAPES UP TO 1000 J/KG AND LOW LEVEL
SHEAR VALUES OF 20-30 KT INDICATIVE OF WIND GUSTS TO 40 KT AND
HAIL TO 3/4 INCH WITH STRONGER CELLS OVER THE SOUTHERN NEB
PANHANDLE. HAVE INCREASED POPS FOR THIS AREA THROUGH EARLY
AFTERNOON. REMAINDER OF ZONE FORECAST ON TRACK.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY NIGHT)
ISSUED AT 330 AM MDT THU MAY 16 2013

IR SATELLITE LOOP SHOWING AN UPPER VORT MAX MOVING NORTHEAST ACROSS
NORTH CENTRAL COLORADO CURRENTLY WITH RADAR SHOWING ISOLATED LIGHT
SHOWERS OVER THE CWA GENERALLY TO THE NORTH AND EAST OF CHEYENNE.
EXPECT THIS WAVE TO CONTINUE MOVING NORTHEAST ACROSS THE AREA
TODAY. TIMING OF THIS FEATURE SUCH THAT ANY INCREASED CONVECTION
SHOULD BE CONFINED TO THE NORTHEAST PART OF THE PANHANDLE INTO
EARLY THIS AFTERNOON...MOVING OUT BY LATE AFTERNOON. ELSEWHERE
VERY WEAK INSTABILITY AND SUBSIDENCE BEHIND THIS SHORTWAVE SHOULD
LIMIT OR EVEN INHIBIT CONVECTION TODAY. TEMPERATURES ON THE MILD
TO WARM SIDE TODAY THEN ABOUT 5-10 DEGREES WARMER ON FRIDAY
ESPECIALLY OVER THE PLAINS AS HEIGHTS RISE IN RESPONSE TO DIGGING
UPPER TROF OVER THE WESTERN PART OF THE COUNTRY. WARMING MID-LEVEL
TEMPS SHOULD ALSO CAP THE ATMOSPHERE ALONG WITH CONTINUED WEAK
INSTABILITY SO MAINLY DRY. MAY HAVE TO WATCH FOR SOME CONVECTION
OVER THE CENTRAL PANHANDLE IF SFC TROF SETS UP A BIT FARTHER WEST
THAN EXPECTED FRIDAY INTO FRIDAY EVENING.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 330 AM MDT THU MAY 16 2013

MODELS IN GOOD AGREEMENT THROUGH THE WEEKEND...AND THEN START TO
DIVERGE BY EARLY NEXT WEEK REGARDING THE SPEED OF THE DEPARTING
UPPER LEVEL TROUGH. ALL MODELS SHOW THE PACIFIC TROUGH PUSHING
INTO THE ROCKY MOUNTAIN REGION ON SATURDAY. DO NOT THINK SHOWERS
AND THUNDERSTORMS WILL BE AS WIDESPREAD AS MODELS SUGGEST ON
SATURDAY...DUE TO DRIER DOWNSLOPE WINDS EARLY THAT MORNING...
RESULTING IN A DRY BOUNDARY LAYER THROUGH MOST OF THE DAY. ANY
AVAILABLE MOISTURE WILL LIKELY BE ALOFT INITIALLY. KEPT POP
BETWEEN 50 TO 60 PERCENT IN THE MOUNTAINS...WITH ONLY 20 TO 30
PERCENT ACROSS THE VALLEYS AND HIGH PLAINS. A BETTER CHANCE FOR
SHOWER AND THUNDERSTORMS IS LIKELY ON SUNDAY...AS THE UPPER LEVEL
TROUGH AXIS WILL BE OVER WYOMING. THE BEST CHANCE FOR MODERATE
RAINFALL AMOUNTS WILL BE WELL NORTH OF I80...FROM DOUGLAS TO
ALLIANCE NEBRASKA. HIGH TEMPERATURES WILL BE TRICKY...WITH MODELS
IN POOR AGREEMENT ON THE AMOUNT OF COOLER AIR AND PRECIP
INTENSITY...ALONG WITH THE TIMING OF THE COLD FRONT ON SATURDAY.
BELIEVE HIGHS IN THE 80S ON SATURDAY ACROSS WESTERN NEBRASKA WILL
LOWER INTO THE UPPER 60S TO LOW 70S BY SUNDAY...AND INTO THE UPPER
50S TO MIDDLE 60S ACROSS MOST OF SOUTHEAST WYOMING ON SUNDAY.

BY EARLY NEXT WEEK...MODELS DIFFER ON THE POSITION OF THE STORM
SYSTEM AS THE UPPER LEVEL TROUGH BECOMES A CLOSED LOW ACROSS THE
GREAT PLAINS. THE 00Z ECMWF SHOWS THE UPPER LEVEL LOW STALLING
OVER THE NORTHERN PLAINS THROUGH TUESDAY...RESULTING IN SLIGHTLY
COOLER TEMPERATURES AND A HIGHER CHANCE FOR PRECIPITATION. THE
OTHER MODELS SHOW THIS SYSTEM MOVING FURTHER NORTH AND EASTWARD BY
MONDAY NIGHT...RESULTING IN DRIER CONDITIONS BY TUESDAY AND
WEDNESDAY. KEPT A LOW CHANCE OF PRECIPITATION THROUGH
WEDNESDAY...BUT KEPT TEMPERATURES NEAR OR SLIGHTLY ABOVE NORMAL.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY MORNING)
ISSUED AT 1137 AM MDT THU MAY 16 2013

VFR CEILINGS AND VISIBILITIES THROUGH EARLY THIS EVENING...EXCEPT
BRIEF MVFR IN VICINITY OF TSTORMS WESTERN NEB PANHANDLE AND
SOUTHEAST WY MOUNTAINS. MAINLY SCATTERED MID AND HIGH CLOUDS
LATER THIS EVENING THROUGH FRIDAY MORNING. IT WILL BE BREEZY
AT TIMES FOR THE WY TERMINALS WITH WEST TO SOUTHWEST WINDS 15 TO
25 KT THROUGH THIS AFTERNOON. WINDS BECOME LIGHT AFTER SUNSET.

&&

.FIRE WEATHER...
ISSUED AT 330 AM MDT THU MAY 16 2013

NO CONCERNS ANTICIPATED THROUGH THE UPCOMING WEEKEND. GUSTY WINDS
ARE EXPECTED TO OCCUR OVER WESTERN DISTRICTS FRIDAY ALONG WITH LOW
AFTERNOON RELATIVE HUMIDITIES BUT FUELS NOT CRITICAL AT THIS
TIME. COOLER CONDITIONS EXPECTED TO SPREAD OVER THE AREA SATURDAY
AND SUNDAY WITH COOL CONDITIONS CONTINUING INTO EARLY NEXT WEEK.
MAINLY DRY TODAY THROUGH FRIDAY THEN INCREASING CHANCES FOR
SHOWERS LATE SATURDAY INTO EARLY NEXT WEEK.

&&

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

$$

UPDATE...JAMSKI
SHORT TERM...RE
LONG TERM...TJT
AVIATION...JAMSKI
FIRE WEATHER...RE