Tornado and Hail in Colorado, August 15, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
245 AM MDT WED AUG 15 2007

.SHORT TERM...THE UPPER LEVEL RIDGE WILL FLATTEN SOME THROUGH
TONIGHT WITH A WEAK MID LEVEL TROUGH MOVING ACROSS THIS AFTN INTO
THE EVENING HOURS.  MEANWHILE SUBTROPICAL MOISTURE WILL REMAIN OVER
THE AREA WITH PRECIPITABLE WATER VALUES JUST ABOVE AN INCH.  SHOULD
SEE SCT TSTMS DEVELOP IN THE MTNS AND FOOTHILLS BY EARLY AFTN WITH
ADDITIONAL ACTIVITY DEVELOPING BY MID TO LATE AFTN OVER NERN CO AS
WELL.  STORMS WILL PRODUCE SOME HEAVY RAINFALL IN A FEW LOCATIONS
HOWEVER WITH 20 KT WLY MID LEVEL FLOW STORMS SHOULD MOVE ALONG.
HIGHS THIS AFTN SHOULD BE SOMEWHAT COOLER THAN TUE AS 850-700 MB
TEMPS DROP BY AROUND 3 DEGREES C.  FOR TONIGHT WILL SEE SOME
LINGERING CONVECTION THROUGH THE EVENING HOURS ESPECIALLY OVER THE
NERN PLAINS WHICH SHOULD GRADUALLY END AROUND MIDNIGHT.

.LONG TERM...PAST SEVERAL SHIFTS THE MODELS HAVE FLOPPED AROUND WITH
THE HOT AIR DOME ASSOCIATED WITH THE MASSIVE UPPER RIDGE CURRENTLY
CENTERED OVER OKLAHOMA. A POSSIBLE REASON FOR THIS DISCONCERTING
OSCILLATION MAY HAVE TO DO WITH THE UNSEASONABLY DEEP/COLD UPPER
TROUGH AND UPR LOW  PULSING OFF THE PACIFIC NW COAST. WEAK
PERTURBATIONS WITHIN THE 500-300 MB QUASI-GEOSTROPHIC FLOW EJECT
FROM THE BASE OF THIS TROUGH AND RIDE UP ALONG THE NWRN EDGE OF THE
RIDGE. COLD AIR ADVECTION AT MID-LEVELS ASSOCIATED WITH THESE
IMPULSES CAUSES HEIGHTS TO FALL DUE TO COOLING THROUGH THE COLUMN OF
AIR OVER THE AREA. FURTHERMORE COOLING WITHIN THE BNDRY LAYER
FOLLOWING THE PASSAGE OF A FAIRLY STG COLD FRONT WEDNESDAY NIGHT IS
EXPECTED TO LOWER DAYTIME TEMPS ON THE PLAINS BY ANOTHER 1-3C ON
THURSDAY. SPATIAL CROSS SECTIONS SHOW DEEP NELY POST-FRONTAL FLOW
PRIOR TO 18Z/THURSDAY AND A NEARLY SATURATED BNDRY LAYER ON THE
PLAINS FOR MUCH OF THE MORNING. AREAS OF LOW CLOUDS AND FOG A
REASONABLE ASSUMPTION ESPLY UP ALONG THE FRONT RANGE. ANOTHER REASON
FOR THE COOLER TEMPERATURES EXPECTED ON THURSDAY. BY AFTERNOON WINDS
EAST OF THE MTNS VEER AROUND TO A S-SELY COMPONENT WHICH APPEARS TO
ADVECT IN DRIER AIR. HOWEVER BY NIGHT FALL THIS SAME FLOW DRAWS IN
HIGHER DEWPTS WHICH MAY AGAIN RESULT IN ANOTHER BATCH OF LOW CLOUDS
AND FOG ON THE PLAINS ESPLY EAST OF A GREELEY AND ELBERT LINE. AS
FOR THUNDERSTORMS CHANCES ON THURSDAY...ATMOSPHERE IN THE HIGH
COUNTRY REMAINS ADEQUATELY WARM AND UNSTABLE FOR SCATTERED
AFTERNOON/EVENING T-STORMS. ALTHOUGH STORM CHANCES DROP OFF PRETTY
QUICKLY THE FARTHER EAST YOU GO WHERE FORECAST SOUNDINGS INDICATE
QUITE A BIT OF CONVECTIVE INHIBITION...ESPLY EAST OF THE I-25 URBAN
CORRIDOR. THEREFORE WILL EITHER LOWER POPS OR REMOVE THEM OUT
THERE.

BY FRIDAY...MODELS SHOW SELY FLOW DEEPENING/STRENGTHENING EAST OF
THE CONTINENTAL DIVIDE AS THE 700-400 MB RIDGE NOSES WESTWARD ACROSS
KANSAS. DURING THE MUCH OF THE DAY THIS FLOW USHERS IN DRIER AIR
LYING ACROSS THE TEXAS/OKLAHOMA PANHANDLES...WITH PRECIPITABLE WATER
VALUES ON FORECAST SOUNDINGS FALLING BELOW AN INCH. EVEN THOUGH THE
LOWER ATMOSPHERE DOES NOT APPEAR TO BE CAPPED...EXPECT TO SEE MOST
OF THE CONVECTION ON FRIDAY IN THE MTNS AND UP AGAINST THE FOOTHILLS
BECAUSE OF SELY STEERING WINDS. 1-2C WARMING ALOFT AND LESS CLOUD
COVER SHOULD RETURN TEMPERATURES ON THE PLAINS TO THE LOWER 90S.

OVER THE WEEKEND...MUCH UNCERTAINTY IN THE MODELS PREVENTS ME FROM
MAKING ANY NOTABLE CHANGES TO THE FORECAST BEYOND FRIDAY. MODELS
DIFFER ON HOW THEY HANDLE THE RATHER POTENT ELY WAVE MOVING UP INTO
TEXAS LATE FRIDAY/ERLY SATURDAY. THIS EVENING/S WRF SHOWS THIS MASS
OF WARM AND VERY MOIST SUBTROPICAL AIR REACHING NERN NEW MEXICO AND
XTRM SERN COLORADO BY 84 HOURS/12Z SATURDAY. WHILE THE GFS HOLDS
THIS MOISTURE LADEN DISTURBANCE BACK OVER TEXAS AND OKLAHOMA. SHOULD
THE WRF TURN OUT TO BE CORRECT...COULD SEE A MUCH WETTER WEEKEND...
AND POSSIBLE EVEN INTO EARLY NEXT WEEK. FOR NOW WILL SIT BACK AND
ALLOW LATER SHIFTS TO HANDLE THIS ONE.

.AVIATION...OVERALL PTRN WILL BE SIMILAR TO TUE WITH SCT TSTMS
AFFECTING THE AIRPORT IN THE 21Z-02Z TIME PERIOD.  CONDITIONS COULD
BRIEFLY DROP TO MVFR IF A STRONGER STORM MOVES OVER THE AIRPORT
OTHERWISE VFR CONDITIONS EXPECTED THROUGH TONIGHT.

&&

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

&&

RPK/BAKER

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
1038 AM MDT WED AUG 15 2007

COZ030>051-161200-
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-
1038 AM MDT WED AUG 15 2007

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

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THE MOUNTAINS AND
FOOTHILLS BY 1 PM...THEN MOVE ACROSS THE NORTHEAST PLAINS DURING
THE AFTERNOON. THE STORMS WILL BE CAPABLE OF PRODUCING HEAVY
RAIN...SMALL HAIL AND GUSTY WINDS.  A FEW LOCATIONS COULD RECEIVE
FROM 1 TO 2 INCHES OF RAIN IN LESS THAN AN HOUR.  THE THUNDERSTORMS
WILL LINGER INTO THE EVENING HOURS BEFORE ENDING BY MIDNIGHT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

ISOLATED AFTERNOON AND EVENING THUNDERSTORMS WILL CONTINUE ACROSS
THE MOUNTAINS AND PLAINS EACH DAY.  A DRIER AIRMASS WILL MOVE ACROSS
COLORADO EARLY NEXT WEEK WITH A REDUCTION IN THUNDERSTORM ACTIVITY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT.

D-L/SWE