National Weather Service Raw Text Product

409 
FXUS65 KCYS 242000
AFDCYS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
200 PM MDT WED JUL 24 2002

HIGH PRESSURE ALOFT WILL REMAIN TO THE SOUTH OF THE CWA THROUGH
SATURDAY WITH THE FEATURE BECOMING MORE ELONGATED FROM WEST TO EAST
WITH TIME.  THAT WILL ALLOW THE CWA TO BE IN WESTERLY FLOW ALOFT... 
WITH THE STRONGER WINDS STAYING IN SOUTHERN CANADA.  SEVERAL SHORT
WAVE TROUGHS WILL MOVE OVER THE CWA THROUGH SATURDAY WITHIN THAT
FLOW...PRODUCING A CHANCE OF MAINLY AFTERNOON AND EVENING SHOWERS
AND THUNDERSTORMS EACH DAY.  INITIAL SHORTWAVE TROUGH WAS OVER
SOUTHERN CALIFORNIA AT MIDDAY AND WILL AFFECT THE CWA THURSDAY
AFTERNOON AND EVENING.  ALREADY CLOUDS AND SOME PRECIPIATION
ASSOCIATED.  MODELS DIFFER ON THE TIMING OF THE FEATURE WITH THE
ETA ABOUT 3 TO 5 HOURS FASTER THAN THE AVN.  THE NEXT SHORTWAVE
TROUGH WAS JUST OFF THE PACIFIC NORTHWEST COAST AT MIDDAY AND 
WILL MOVE OVER THE CENTRAL ROCKIES FRIDAY AFTERNOON AND EVENING.
SURFACE LOW PRESSURE TROUGH WILL GENERALLY BE ALONG THE WYOMING
AND NEBRASKA BORDER...BUT GRADIENT SHOULD BE WEAK ENOUGH TO ALLOW
FOR DIURNAL CONVECTIVE WINDS TO DEVELOP IN SOUTHEAST WYOMING.  
SHOULD BE ENOUGH MOISTURE AND DYNAMICS TO PRODUCE A SCATTERED
COVERAGE OF AFTERNOON AND EVENING STORMS THURSDAY AND FRIDAY.  THE
12Z AVN INDICATES SOME DRYING OVER MUCH OF THE CWA...WITH THE ETA
EXTENSION SHOWING QPF OVER SOUTH CENTRAL WYOMING SATURDAY 
AFTERNOON.  OTHER THAN TIMING OF THE SHORTWAVE TROUGHS...MAIN
MODEL DIFFERENCE IS IN THE AMOUNT OF MOISTURE.  THE AVN CONTINUES
TO GENERALLY HAVE HIGHER PRECIPITABLE WATER VALUES THAN THE ETA
BUT QPF DEPICTIONS ARE CLOSER.  BASED ON CURRENT LAPS RAOBS...
WILL GO BETWEEN THE TWO MODELS ON AMOUNT OF PRECIPITATABLE AND
RELATIVE HUMIDITY DEPICTED.  TEMPERATURES WILL BE A BIT COOLER 
THE NEXT FEW DAYS OVER THE CWA THAN THOSE OF TODAY.  IN THE SHORT 
TERM...WIDELY SCATTERED SHOWERS AND STORMS WILL NEED TO BE IN THE 
SOUTHEAST WYOMING BASED ON THE CURRENT ACTIVITY.    

EXTENDED...
MRF DEPICTS A MID LEVEL TROF MOVING ACROSS WY ON SUNDAY...WITH A 
CHANCE OF PRECIP ACROSS ALL OF THE FORECAST AREA. UKMET IS SOMEWHAT 
FASTER WITH THIS WAVE THAN THE MRF.  WILL MAINLY FOCUS A CHANCE OF 
SHOWERS/THUNDERSTORMS FROM THE MOUNTAINS WESTWARD DUE TO SOUTHWEST 
FLOW ALOFT...AND CLEAN OUT THE PRECIP SOMEWHAT EARLIER BASED ON THE 
UKMET. LOW TO MID LEVEL THICKNESS VALUES DROP SOME BY EARLY NEXT 
WEEK...SUGGESTING A BIT OF A COOL DOWN BUT FMR GUIDANCE TEMPERATURES 
STILL LOOK TOO COOL.  THICKNESS RIDGE BUILDS OVER WESTERN UNITED 
STATES GETS PUMPED UP MID-WEEK AS SYSTEM DROPS INTO THE EASTERN 
NORTH PACIFIC. 

.CYS...
WY...NONE.
NE...NONE.

WEILAND/BANN