Severe Thunderstorm Warning 169, NWS Denver/Boulder, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
1221 PM MDT SUN JUL 24 2011

.UPDATE...WATER VAPOR LOOP SHOWS UPPER LEVEL MOISTURE PLUME HAS
SHIFTED BACK SOUTHWARD. HOWEVER...AT THE SAME TIME LOW LEVEL
MOISTURE WILL CONTINUE TO INCREASE THROUGH THE REST OF THE DAY.
PRECIPITABLE WATER VALUES ARE NOW AROUND 0.30 INCH HIGHER THAN AT
THIS TIME YESTERDAY...AND WE SHOULD REACH VALUES OF AT LEAST 1.0
INCH BY LATE THIS AFTERNOON/EVENING. FORECAST STILL ON TRACK WITH
HIGHER STORM COVERAGE AND LOCALLY HEAVY RAIN POSSIBLE.

&&

.PREV DISCUSSION... /ISSUED 320 AM MDT SUN JUL 24 2011/

SHORT TERM...THERE HAS BEEN A SLIGHT SHIFT TO THE NORTHWEST OF
THE MOISTURE PLUME INTO PORTIONS OF CENTRAL COLORADO. INTEGRATED
PRECIPITABLE WATER TRENDS FROM GPS HAVE SHOWN AN UPWARD TREND IN
MOISTURE VALUES...AS 24HR CHANGES HAVE INCREASED AROUND A QUARTER OF
AN INCH OVER THE FRONT RANGE. SURFACE MOISTURE HAS ALSO INCREASED
WITH DEWPOINTS AROUND 50 EXCEPT EVEN LOWER 60S OVER THE FAR
NORTHEAST PLAINS. PLATTEVILLE PROFILER SHOWING WEAK EAST TO
SOUTHEAST FLOW UP TO AROUND 600MB AND THIS IS PROGGED TO CONTINUE
THROUGH EARLY THIS EVENING. OVERALL...SHOULD SEE AN UPSWING IN
THUNDERSTORM COVERAGE TODAY OVER THE FRONT RANGE FOOTHILLS AND
ADJACENT PLAINS...ESPECIALLY FROM BOULDER AND DENVER AND POINTS
SOUTH. AS LIKE THE PAST FEW DAYS THE STORMS WILL STILL BE MORE
NUMEROUS OVER THE PALMER DIVIDE WITH THE ELEVATED TERRAIN AND HIGHER
MOISTURE. STILL QUITE DRY AIR OVER THE NORTHERN
MOUNTAINS...ESPECIALLY OVER GRAND AND JACKSON COUNTIES.

LONG TERM...THE UPPER RIDGE WILL HAVE MOVED WEST TO BE CENTERED
OVER THE COLORADO AND NEW MEXICO BORDERS BY MONDAY MORNING. THIS
WILL BRIEFLY BLOCK THE MOISTURE FROM THE SOUTHWEST AS WELL AS ALLOW
TEMPERATURES TO WARM. WE SHOULD SEE LOWER TO MID 90S ON THE PLAINS
AND IN THE 70S TO 80S OVER THE HIGH COUNTRY.  CAPES OF 400 TO 1200
J/KG WILL ALLOW WHAT MOISTURE IS AROUND TO BECOME AFTERNOON AND
EVENING THUNDERSTORMS WITH THE MOST ACTIVITY OVER THE MOUNTAINS
FIRST THEN MOVING SLOWLY OVER THE PLAINS. WITH THE LIGHT FLOW
ALOFT...THE STORMS WILL BE SLOW MOVING BUT NOT AS SLOW AS WE SAW
SATURDAY NIGHT.

ON TUESDAY...A PACIFIC TROUGH OVER OREGON WILL CONTINUE TO PUSH
INLAND AND THEREBY PUSH THE UPPER RIDGE BACK TO THE EAST. THIS WILL
BRING SOUTH-SOUTHWESTERLY FLOW ALOFT AND RESUME THE TRANSPORT OF
MONSOONAL MOISTURE. EVEN THOUGH WARMER TEMPERATURES ARE PROGGED AT
700 MB...THE EXTRA MOISTURE AND ASSOCIATED STORMS AND CIRRUS/ANVIL
SHIELDS SHOULD EITHER KEEP THE TEMPERATURES THE SAME OR COOLER. A
COLD FRONT IS EXPECTED TO DROP OUT OF WYOMING AND INTO NORTHEASTERN
COLORADO SOMETIME TUESDAY EVENING INTO THE NIGHT. THIS COULD KEEP
SOME ISOLATED CONVECTIVE ACTIVITY GOING ALL NIGHT.

WEDNESDAY...TEMPERATURES WILL HAVE ONLY COOLED A COUPLE DEGREES IN
THE POST FRONTAL AIRMASS TO BE RIGHT AROUND CLIMATOLOGICALLY NORMAL.
AS THE UPPER HIGH REMAINS TO THE EAST OVER THE MISSISSIPPI VALLEY
THROUGH AT LEAST FRIDAY...SCATTERED CONVECTIVE ACTIVITY AND ABOVE
NORMALS WILL BE THE NORM WEDNESDAY THOUGH FRIDAY. A SLIGHT INCREASE
IN SOUTH-SOUTHWEST FLOW ALOFT WILL SPEED UP STORM MOTIONS...HOWEVER
NOT ENOUGH TO LIMIT THE FLOODING POTENTIAL. WITH PWATS BETWEEN 1 -
1.4 INCHES WITH THE HIGHEST OVER THE EASTERN PLAINS...WILL CONTINUE
TO MONITOR WATER SENSITIVE AREAS.

DID NOT CHANGE THE FORECAST MUCH PAST WEDNESDAY AS THE PREVIOUS
GRIDS REFLECTED THE COMMON TREND BETWEEN THE MODELS OF SLIGHTLY
WETTER AND WARMER THAN AVERAGE CONDITIONS.

&&

.AVIATION...SOME STRATUS HAS DEVELOPED OVER FAR NORTHEAST COLORADO
OVERNIGHT...HOWEVER THE PUSH BACK WESTWARD LOOKS MARGINAL AND GIVEN
THE CONTINUED DRAINAGE SOUTHERLY FLOW WILL NOT PUT IN A LOW CLOUD
DECK BUT STILL HOLD TO A FEW-SCT LOWER STUFF JUST IN CASE. BOTH
HRRR/RUC/NAM DO KEEP THE STRATUS EAST OF THE LOCAL TERMINALS. FOR
LATER TODAY WILL CONTINUE WITH THE HIGHER CHANCES OF STORMS
TODAY...WITH THE BEST CHANCES BETWEEN 22-02Z. COULD BE SOME ILS
APPROACHES IN THE VICINITY OF THUNDERSTORMS.

.HYDROLOGY...THE THREAT OF HEAVY RAIN AND LOCALIZED FLASH FLOODING
WILL INCREASE BY LATER THIS AFTERNOON AND EVENING WITH HIGHER
PRECIPITABLE WATER VALUES OF 1.0 TO 1.25 INCH AND SLOW STORM MOTIONS
UNDER 5 KNOTS.

&&

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

UPDATE...BARJENBRUCH
SHORT TERM...ENTREKIN
LONG TERM....KRIEDERMAN
AVIATION...ENTREKIN

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
1102 AM MDT SUN JUL 24 2011

COZ030>051-251200-
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-
1102 AM MDT SUN JUL 24 2011

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

.DAY ONE...TODAY AND TONIGHT

MOISTURE WILL CONTINUE TO INCREASE ACROSS THE AREA THROUGH THIS
EVENING.  THIS WILL RESULT IN HIGHER THUNDERSTORM COVERAGE...
ESPECIALLY IN AND NEAR THE FRONT RANGE AND ACROSS THE PALMER DIVIDE.

THUNDERSTORMS TODAY WILL BE CAPABLE OF PRODUCING HEAVY RAIN...
HAIL...FREQUENT LIGHTNING AND WIND GUSTS AROUND 50 MPH. DUE TO LIGHT
WINDS ALOFT AND SLOW MOVEMENT OF STORMS TODAY...THE FLASH FLOOD
THREAT WILL BE HIGHER TODAY.  RAINFALL AMOUNTS OF 1 INCH IN 20 TO 30
MINUTES CAN BE EXPECTED FROM THE STRONGEST STORMS.  IF ONE OF THESE
STORMS STALLS IN AN URBAN AREA OR RECENT BURN AREA OF THE
FOOTHILLS...FLASH FLOODING WOULD BE POSSIBLE.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THERE WILL BE A CHANCE OF LATE DAY SHOWERS AND THUNDERSTORMS INTO
NEXT WEEKEND.  THE BEST CHANCE IS EXPECTED ON TUESDAY AND
WEDNESDAY.  HEAVY RAINS WILL BE THE MAIN THREAT WITH THESE
THUNDERSTORMS.  TEMPERATURES WILL STAY SLIGHTLY ABOVE SEASONAL
NORMALS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT...HOWEVER ANY
HEAVY RAINFALL AND FLOODING REPORTS WILL BE APPRECIATED.

BARJENBRUCH/RJK