Severe Thunderstorm Warning 133, NWS Denver/Boulder, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
305 PM MDT THU AUG 5 2004

.SHORT TERM DISCUSSION...DECENT MOISTURE PLUME ACROSS AREA AS SHOWN
BY WATER VAPOR IMAGERY. LATEST PRECIPITABLE WATER VALUES HAVE
REACHED AN INCH AND MODEL SOUNDINGS INDICATE AN UPWARD CLIMB TO
AROUND 1.25 INCHES BY LATE AFTERNOON.  SOUTHEASTERLY LOW LEVEL FLOW
CONTINUES TO INCREASE ACROSS PLAINS...ALONG WITH THE BEGINNINGS OF A
DENVER CYCLONE.  GOOD LOW LEVEL MOISTURE IN PLACE...AS NOTED BY 50S
AND LOWER 60S DEWPOINTS.  SO THE POTENTIAL CONTINUES FOR HEAVY RAIN
WITH A BIG CONCERN FOR FLOODING ALONG FOOTHILLS.  ANOTHER AREA OF
CONCERN EXTENDS FROM THE PALMER DIVIDE NORTHEAST INTO WASHINGTON
COUNTY WHERE AREA HAS BEEN SATURATED FROM RECENT RAINS.  RADAR
SHOWING THUNDERSTORMS MOVING ACROSS MOUNTAINS AND FOOTHILLS...
ASSOCIATED WITH SHORTWAVE OVER NORTHWEST COLORADO.  STORMS MOVING
FASTER THAN THE FORECAST STORM MOTION...WHICH IS A GOOD THING.  BUT
THERE IS THE POSSIBILITY OF TRAIN ECHOES...WHICH IS NOT A GOOD
THING.  LATEST MM5 INDICATING BULK OF PRECIPITAION TO OCCUR ALONG
FOOTHILLS AND EAST OF THE DENVER METRO AREA WHILE ETA SHOWING MOST
OF PRECIP WILL BE ALONG FRONT RANGE.  IN EITHER CASE...THERE COULD
BE FLOODING PROBLEMS. SO...WILL KEEP THE FLASH FLOOD WATCH GOING.
LATEST CAPE ANALYSIS INDICATING VALUES REACHING 1500 J/KG ACROSS
PLAINS...SO CANNOT RULE OUT THE POSSIBILITY OF A FEW STORMS
PRODUCING MARGINALLY SEVERE HAIL. DIV-Q PROGS SHOW SHOW UPWARD
FORCING OVERNIGHT...SUGGESTING THAT SOME PRECIPITATION COULD LINGER
ACROSS AREA.  FROM WATER VAPOR LOOPS...THERE APPEARS TO ANOTHER
SHORTWAVE MOVING NORTH ACROSS WESTERN NEW MEXICO.  THIS WAVE SHOULD
MAKE ITS WAY ACROSS THE AREA...SO WILL LEAVE THE ISOLD RW- IN
PLACE.  BOUNDARY LAYER WIND AND MOISTURE PROGS SUGGEST DEVELOPMENT
OF STRATUS AND FOG ACROSS EASTERN PLAINS.  BUT WITH POTENTIAL FOR
LINGERING SHOWERS...WILL NOT MENTION AT THIS TIME.  ON FRIDAY...
MODELS SHIFT THETA-E AXIS EAST TO KANSAS BORDER...AND DROP
PRECIPITABLE WATER VALUES TO BETWEEN .50 INCH AND .75 INCH.  CROSS
SECTIONS AND FORECAST SOUNDINGS SHOW MOST OF MOISTURE ABOVE MOUNTAIN
TOP...SUGGESTING ISOLATED STORM COVERAGE WITH MORE WIND THAN RAIN.
NOT EXPECTING MOISTURE TO BE FLUSHED OUT THAT SIGNIFICANTLY...AND
WITH DAYTIME HEATING...SHOULD SEE SOME AFTERNOON STORMS.  CURRENT
FORECAST GRIDS HAVE THE RIGHT IDEA...AND WILL CONTINUE TREND.
TEMPERATURE AND THICKNESS GRIDS SUGGEST TEMPERATURES REACHING 90
DEGREES ACROSS PLAINS DURING AFTERNOON WHICH IS IN LINE WITH
GUIDANCE.  THIS MAY BE A BIT TOO WARM GIVEN STORM POTENTIAL AND WILL
UNDERCUT A BIT.

.LONG TERM DISCUSSION...A RATHER PERSISTENT WEATHER PATTERN WILL
HOLD IN PLACE OVER COLORADO THROUGH THE FORECAST PERIOD.  THE UPPER
RIDGE OVER NEW MEXICO TODAY WILL RETROGRADE TO ARIZONA OVER THE
WEEKEND...LEAVING COLORADO UNDER MODERATE NORTHWESTERLY FLOW ALOFT.
ON FRIDAY AND SATURDAY...THERE WILL BE SOME LEE TROUGHING AT LOW
LEVELS WHICH WILL ALLOW FOR A LITTLE BIT OF DRYING AND WARMING AT
THE LOWER LEVELS.  HOWEVER...MID AND UPPER LEVELS WILL REMAIN
MOIST...BECAUSE OF THE SUBTROPICAL MOISTURE PRESENTLY TRAPPED
BENEATH THE UPPER RIDGE.  THE PRESENCE OF THE MOISTURE WILL ALLOW
AFTERNOON AND EVENING SHOWER ACTIVITY TO DEVELOP...INITIALLY OVER
THE MOUNTAINS AND FOOTHILLS...THEN SPREADING TO THE PLAINS.  THE
NORTHWESTERLY FLOW ALOFT WILL HELP CREATE A FAVORABLE SHEAR PROFILE
FOR SHOWER ACTIVITY.  ON SUNDAY...A COLD FRONT WILL DROP DOWN FROM
THE NORTHERN PLAINS WITH A REINFORCING SHOT OF COOLER AIR ON
MONDAY.  THE UPSLOPE FLOW BEHIND THESE FRONTS WILL WORK TO COOL THE
AIRMASS BUT ALSO INCREASE MOISTURE LEVELS.  WITH THE NORTHWESTERLY
FLOW CONTINUING ALOFT...THE PATTERN OF AFTERNOON AND EVENING SHOWER
ACTIVITY WILL ALSO CONTINUE.  WITH THE AID OF UPSLOPE FLOW ON SUNDAY
AND MONDAY...THOSE TWO DAYS MAY BE THE MOST FAVORABLE FOR LOCALLY
HEAVY RAIN SHOWERS.  LATER SHIFTS CAN REFINE THE DETAILS AS THE TIME
GETS CLOSER.  GRADUAL DRYING AND WARMING IS EXPECTED THROUGH THE
MIDDLE PART OF NEXT WEEK AS THE UPPER RIDGE EXPANDS OVER THE WESTERN
U.S. AND MID-LEVEL MOISTURE LEVELS EVENTUALLY DECREASE.

&&

.BOU...WATCHES/WARNINGS/ADVISORIES...FLASH FLOOD WATCH UNTIL
MIDNIGHT TONIGHT FOR FOOTHILLS AND PLAINS..ZONES 35..36..38>51.

&&

LESZCYNSKI/DANKERS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
1107 AM MDT THU AUG 05 2004

COZ030>051-061200-
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-
1107 AM MDT THU AUG 05 2004

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

.DAY ONE...TODAY AND TONIGHT

...A FLASH FLOOD WATCH FOR THE FOOTHILLS AND NORTHEAST PLAINS FROM
NOON TODAY THROUGH MIDNIGHT TONIGHT...

A VERY MOIST AIRMASS REMAINS IN PLACE ACROSS COLORADO.  SCATTERED
THUNDERSTORMS WILL CONTINUE TO DEVELOP OVER THE MOUNTAINS...
FOOTHILLS AND ADJACENT PLAINS...THEN SPREAD ACROSS THE REMAINDER OF
THE PLAINS LATER THIS AFTERNOON AND EVENING.  THE MAIN THREAT WITH
THE STORMS WILL BE HEAVY RAIN AND THE POTENTIAL FOR FLOODING.
RAINFALL RATES WILL BE UP TO 2 INCHES IN AN HOUR WITH THE STRONGEST
STORMS.

THE GREATEST THREAT OF FLASH FLOODING EXISTS ACROSS THE PALMER
DIVIDE REGION AND INTO SOUTHERN WASHINGTON COUNTY AS THE GROUND IS
ALREADY SATURATED IN SEVERAL AREAS FROM RAINFALL ON WEDNESDAY.
OTHER AREAS SUSCEPTIBLE TO FLASH FLOODING ARE THE HAYMAN...OVERLAND
AND PICNIC ROCK BURN AREAS.

THERE MAY BE JUST ENOUGH INSTABILITY IN THE ATMOSPHERE TO GENERATE A
SEVERE STORM WITH MARGINAL HAIL UP TO AN INCH IN DIAMETER.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THERE WILL BE AT LEAST A SLIGHT CHANCE OF STORMS EACH AFTERNOON AND
EVENING THROUGH THE MIDDLE OF NEXT WEEK...BUT THE THREAT OF ANY
SEVERE WEATHER WILL BE LOW.  LOCALLY HEAVY RAINFALL WILL BE POSSIBLE
AT TIMES...MAINLY SUNDAY AND MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING TO RELAY
REPORTS OF HEAVY RAINFALL AND FLOODING.

D-L/DANKERS