Severe Thunderstorm Warning 266, NWS Denver/Boulder, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
305 PM MDT WED AUG 26 2009

.SHORT TERM...A WEAK UPPER LEVEL DISTURBANCE WILL CONTINUE TO MOVE
EAST OUT OF NORTHEAST COLORADO THIS EVENING AND OVERNIGHT AS A DRY
RIDGE OF HIGH PRESSURE BEGINS TO ESTABLISH OVER THE WESTERN UNITED
STATES. VISIBLE/WATER VAPOR SATELLITE CURRENTLY SHOWING SUBSIDENT
EDGE OF CLOUDS AND COVECTION OVR CENTRAL AND SOUTHERN WYO THIS
AFTERNOON AND THIS TREND IS EXPECTED TO CONTINUE OVER NEXT 24HRS.
FOR THIS EVENING HOWEVER...BEST SFC MOISTURE AND CAPES AGAIN RESIDE
MAINLY EAST OF A FORT MORGAN TO LIMON LINE. AS CURRENT CONVECTIVE
ENERGY ROLLS OFF OF HIGHER TERRAIN AND OUT ONTO THE PLAINS...WILL
KEEP THE HIGHER POP GOING FOR POINTS EAST. ITS POSSIBLE TSRA
ACTIVITY COULD CONTINUE INTO THE LATE EVENING HOURS OUT EAST AS FCST
SOUNDING AND TEMPS GRIDS INDICATE ADDITIONAL MID/UPPER LEVEL COOLING
FROM 03Z-09Z. STORM MOVEMENT THIS AFTERNOON IS RATHER SLOW BUT WILL
ANTICIPATE QUICKER STORM MOTION LATER THIS EVE AS WINDS ALOFT TREND
MORE NORTHERLY WITH THE WEAK CAA. FOR THURSDAY...FLOW ALOFT REMAINS
NORTHERLY OVER THE CWA AS RIDGE CONTINUES TO AMPLIFY OVR THE GREAT
BASIN. PERSISTANT SUBSIDENCE IN THE QG FIELD BEGINS AFTER 06Z THUR
WITH SPATIAL CROSS SECTIONS SHOWING DRYING AROUND THE EASTERN SIDE
OF RIDGE. THE DEWPTS OF CURRENT SFC OBS OVR WY/WRN SD AND WRN NEB
RANGE FROM THE UPPER 30S TO MID 50S AND WITH NORTHERLY SFC FLOW
EXPECTED OVR THE AREA THURSDAY...LOWER MOISTURE WILL BE AVAILABLE
FOR STORMS THURS AFTNOON AND EVE. WITH A DRYER AIRMASS AT ALL LEVELS
EXPECTED ALONG WITH MORE AVAILABLE SUN EXPECTED...THURSDAYS GUIDANCE
TEMPS OF NEAR TO SLIGHTLY BELOW SEASONAL NORMALS LOOK IN LINE.

.LONG TERM...STARTING TO LOOK LIKE FALL AS LOW LEVELS ARE HAVING
TROUBLE WARMING UP ENOUGH TO PRODUCE DIURNAL CONVECTION WHILE UPPER
LEVELS REMAIN WARM UNDER THE UPPER RIDGE. NOCTURNAL COOLING WILL
OFFSET THE PLENTIFUL SUNSHINE DURING THE DAY. NORTHERLY FLOW ALOFT
WILL ALSO PREVENT MUCH WARMUP OVER THE NEXT FEW DAYS. LOW LEVEL AIR
WILL ALSO BE DRIER...AND COMBINED WITH WEAK SUBSIDENCE THIS WILL
SEVERELY LIMIT...IF NOT ELIMINATE THUNDERSTORM ACTIVITY. STEERING
WINDS WILL BE A BIT EAST OF NORTH AS WELL...SO ANYTHING THAT FORMS
OVER THE MOUNTAINS SHOULD STAY THERE. HELD ON TO LOW POPS IN THE
MOUNTAINS MAINLY SOUTHWEST OF DENVER...DROPPED THEM ELSEWHERE. THERE
MAY BE A BIT MORE MOISTURE ON SATURDAY BUT AGAIN MAINLY OVER THE
MOUNTAINS. LEFT FORECAST HIGHS ALONE THESE DAYS...DROPPED LOWS A
COUPLE...NEAR THE COOLER GFS MOS GUIDANCE.

MODELS SOLUTIONS ARE CONVERGING WITH A WEAK LOW CUTTING OFF IN THE
TOP OF THE RIDGE AND THEN DRIFTING EAST ACROSS THE NORTHERN ROCKIES
ON SUNDAY OR MONDAY. THIS MAY BE TOO FAR NORTH TO HAVE MUCH
EFFECT...THOUGH THERE WILL LIKELY BE SOME COOLING ALOFT THAT COULD
REMOVE THAT BARRIER FOR CONVECTION. STILL PROBABLY PRETTY LIMITED
THOUGH. RIDGE REBUILDS FOR EARLY NEXT WEEK...IT SHOULD EVENTUALLY
GET A BIT WARMER BUT ON MONDAY AND TUESDAY THERE WILL LIKELY STILL
BE SOME NORTHERLY FLOW AT LOW LEVELS AS THE UPPER LEVELS EDGE
WARMER...AND THE NIGHTS WILL CONTINUE TO LENGTHEN. SO OVERALL...
LITTLE CHANGE WITH MAINLY DRY AND SEASONABLY MILD WEATHER.

&&

.AVIATION...ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE IN THE
VICINITY OF THE DENVER AREA AIRPORTS THROUGH 00Z. BRIEF MODERATE
RAIN AND GUSTY WINDS CAN BE EXPECTED IN AND NEAR THUNDERSTORMS.
THUNDERSTORM AND RAIN SHOWER ACTIVITY WILL BEGIN TO DIMINISH OVER
THE AREA AFTER 03Z AS A WEAK UPPER LEVEL DISTURBANCE CONTINUES TO
EXIT THE REGION. A LARGE RIDGE OF HIGH PRESSURE WILL CONTINUE TO
BUILD OVER THE WESTERN UNITED STATES OVER THE NEXT 24 HOURS. AS THIS
RIDGE AMPLIFIES THURSDAY...A FAIRLY DRY AND MORE STABLE NORTHERLY
FLOW ALOFT EXPECETED FOR NORTHERN COLO WITH ISOLATED GUSTY
THUNDERSTORMS EXPECTED AFTER 20Z THURSDAY.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...NONE.

FREDIN/GIMMESTAD

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE DENVER CO
1128 AM MDT WED AUG 26 2009

COZ030>051-271200-
JACKSON COUNTY BELOW 9000 FEET-WEST JACKSON AND WEST GRAND
COUNTIES ABOVE 9000 FEET-GRAND AND SUMMIT COUNTIES BELOW 9000
FEET-SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/
NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET-SOUTH AND SOUTHEAST
GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/
SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET-LARIMER AND
BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET-JEFFERSON AND WEST
DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR CREEK/NORTHEAST PARK
COUNTIES BELOW 9000 FEET-CENTRAL AND SOUTHEAST PARK COUNTY-LARIMER
COUNTY BELOW 6000 FEET/NORTHWEST WELD COUNTY-BOULDER AND JEFFERSON
COUNTIES BELOW 6000 FEET/WEST BROOMFIELD COUNTY-NORTH DOUGLAS
COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE COUNTIES/
EAST BROOMFIELD COUNTY-ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES
ABOVE 6000 FEET-NORTHEAST WELD COUNTY-CENTRAL AND SOUTH WELD
COUNTY-MORGAN COUNTY-CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES-
NORTH AND NORTHEAST ELBERT COUNTY BELOW 6000 FEET/NORTH LINCOLN
COUNTY-SOUTHEAST ELBERT COUNTY BELOW 6000 FEET/SOUTH LINCOLN
COUNTY-LOGAN COUNTY-WASHINGTON COUNTY-SEDGWICK COUNTY-PHILLIPS
COUNTY-
1128 AM MDT WED AUG 26 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL
COLORADO.

.DAY ONE...TODAY AND TONIGHT

A WEAK UPPER LEVEL DISTURBANCE PASSING OVER NORTHEAST COLORADO THIS
AFTERNOON WILL MOVE EAST OF THE OUTLOOK AREA DURING THE EVENING.
SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER THE MOUNTAINS AND FRONT
RANGE FOOTHILLS BEFORE THE NOON HOUR BEFORE MOVING SOUTHEAST OVER
THE I-25 URBAN CORRIDOR BY 1 PM. ADDITIONAL STORM DEVELOPMENT IS
EXPECTED LATER THIS AFTERNOON FARTHER OUT ON THE PLAINS WHERE
GREATER MOISTURE AND INSTABILITY RESIDES. THE MAIN THREAT FROM
THUNDERSTORMS THIS AFTERNOON AND EARLY THIS EVENING WILL BE LOCALLY
HEAVY RAINFALL AND HAIL. THE GREATEST RISK FOR HAIL APPEARS TO EXIST
EAST OF A GREELEY TO ELBERT LINE. RAINFALL AMOUNTS IN EXCESS OF 1
INCH IN LESS THAN 30 MINUTES WILL ALSO BE POSSIBLE FROM THE STRONGER
STORMS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THERE WILL BE AT LEAST A SLIGHT CHANCE OF LATE DAY SHOWERS AND
THUNDERSTORMS OVER THE FORECAST AREA THROUGH THE PERIOD. THERE MAY
BE A BIT MORE ACTIVITY ON SUNDAY OR MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT.

FREDIN/BAKER/GIMMESTAD

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