Severe Thunderstorm Warning 12, NWS Denver/Boulder, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
230 PM MDT THU MAY 20 2004

...CORRECTION...

.SHORT TERM...THUNDERSTORM POTENTIAL GOES UP THIS EVENING WITH
INFLUX OF DEEP LOW LEVEL MOISTURE ON MODERATELY STRONG SELY FLOW.
MODELS SHOW SFC LOW IN E-CNTRL COLORADO WRAPPING MOISTURE BACK INTO
THE FRONT RANGE THIS EVENING WITH LOWER/MID 50S DEWPTS MOVING UP THE
SOUTH PLATTE VALLEY. CUMULUS POPPPING NOW ALONG THE PALMER DIVIDE
PROBABLY THE SEEDS FOR CONVECTION ON THE PLAINS THIS EVENING.
A SECOND AREA OF NEW CONVECTION OVER THE FOOTHILLS NOW MOVING OVER
THE NRN URBAN CORRIDOR MAY PRODUCE OUTFLOW TO GENERATE STORMS IN THE
METRO AREA NEXT FEW HOURS. DOWNSTREAM OVR NRN ARIZONA A REGION OF
DECENT UPPER TROPOSPHERIC DIVERGENCE PROGGED BY BOTH ETA AND AVN TO
PASS OVR NERN CO BETWEEN 06Z-12Z. SOUNDINGS FROM THE MM5 AND ETA
SHOW PRETTY IMPRESSIVE 0-3KM HELICITIES ALONG A SHARP BNDRY LAYER
SHEAR AXIS LIFTING SLOWLY NEWRD ACRS THE NERN CO PLAINS TONIGHT.
STRONG SFC-700MB WAA ALSO RESPONSIBLE FOR CAPE VALUES IN THE
1500-2500 RANGE AND 700-500 LAPSE RATES IN THE 8-10C/KM RANGE IN
THIS AREA. LATEST SPC CONVECTIVE OUTLOOK HAS PRETTY MUCH ALL OF ERN
CO UNDER A SLIGHT RISK THROUGH 12Z/21. MOIST POST-STORM ENVIRONMENT
WILL ALSO RESULT IN AT LEAST PATCHY FOG ON THE PLAINS LATE.

FRIDAY...ATMOSPHERE DRIES WITH WARM SWLY FLOW ALOFT MIXING DOWN TO
THE SFC BY AFTERNOON. ETA MAYBE A BIT FAST IN FLUSHING LOW LEVEL
MOISTURE OUT. STRONG SOLAR HEATING AND WEAK MID/UPR LEVEL DIVERGENCE
ENOUGH TO PRODUCE AT LEAST ISOLATED STORMS IN THE AFTERNOON...MAINLY
OVER AND NEAR THE MTNS. MAX TEMPERATURES EXPECTED TO BE SOME 5 TO 10
DEGS ABOVE THOSE OBSERVED TODAY.

.LONG TERM DISCUSSION...EASTERN PACIFIC RIDGE CONTINUES TO DROP
ENERGY ALONG THE WEST COAST RESULTING IN A GENERALLY DRY SW FLOW
PATTERN ACROSS CO THRU TUESDAY. SERIES OF WEAK WAVES MOVES ACROSS CO
IN THE SW FLOW BUT NONE OF THESE IS VERY STRONG WITH MOISTURE
LACKING. STRONGEST WAVE LIFTS ACROSS CO ON SAT WITH PRETTY DECENT
JET CORE RIDING INTO SERN CO 00Z SUN WHICH GIVES US SOME DECENT
ASCENT. PROBLEM IS AIRMASS IS FAIRLY DRY...WITH MARGINAL MSTR ACROSS
NRN PTNS OF CWA. WILL MAINTAIN ISOLD POPS TO REFLECT THE RELATIVELY
DRY AIRMASS. SHOULD BE LESS ACTIVITY ON SUNDAY WITH DRIER AIR AND
MORE SUBSIDENT AIRMASS.

AS THE ENERGY DROPS INTO THE PAC NW STATES DURING THIS LONG TERM
PERIOD...ENERGY IS SPLITTING BETWEEN THE NRN AND SRN BRANCHES. NRN
FLOW ENERGY CONTINUES TO DROP DOWN WEAK SURGES INTO NERN CO AND GFS
LONG RANGE STUFF CONTINUES TO SHOW A STALLED FRONTAL BOUNDARY ACROSS
FAR NERN CO WHICH COULD BE A FOCUS FOR ISOLD STORMS INTO EARLY NEXT
WEEK. LATEST GFS SHOWS THE RIDGE ALOFT BUILDING OVER ROCKY MTN
REGION AS CLOSED LOW OFF SRN CA LIFTS NE LATE IN THE WEEK. STILL A
LOT OF DIFFEERNECES IN HOW THE MODELS ARE PHASING THE ENERGY BETWEEN
THE STREAMS. STILL LOOKS GENERALLY DRY IN DAYS 6-7 AND WILL LEAVE
FCST THAT WAY WITH SEASONAL TEMPS.

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

&&

BAKER/ENTREKIN

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
1110 AM MDT THU MAY 20 2004

COZ030>051-211200-
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-
1110 AM MDT THU MAY 20 2004

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

.DAY ONE...TODAY AND TONIGHT

A WEAK FRONTAL BOUNDARY STALLED ALONG THE MONUMENT RIDGE LATE THIS
MORNING WILL SERVE AS A FOCUS FOR SHOWER AND THUNDERSTORM
DEVELOPMENT THIS AFTERNOON. THUNDERSTORMS ARE EXPECTED TO FORM
INITIALLY OVER THE HIGHER TERRAIN OF SOUTHERN JEFFERSON...DOUGLAS
AND ELBERT COUNTIES. THESE STORMS MAY PRODUCE HAIL AND BRIEF HEAVY
RAIN. WINDS ALOFT WILL THEN CARRY THESE STORMS NORTH AND EAST
POSSIBLY OVER THE DENVER METRO AREA LATE THIS AFTERNOON. AGAIN HAIL
AND BRIEF HEAVY RAIN WILL BE THE MAIN THREAT. THIS EVENING
STRENGTHENING SOUTHERLY LOW LEVEL WINDS ON THE PLAINS WILL HELP MOVE
THE FRONTAL BOUNDARY NORTHWARD. STRONG DESTABILIZATION AND WIND
SHEAR ALONG THIS ADVANCING BOUNDARY WOULD SUPPORT THE FORMATION OF
SCATTERED THUNDERSTORMS THIS EVENING...GENERALLY EAST OF AN ELBERT
TO FORT MORGAN LINE. SOME OF THESE STORMS MAY BECOME SEVERE WITH
STRONG WINDS AND LARGE DAMAGING HAIL. THE STRONGLY SHEAR ENVIRONMENT
MAY ALSO PRODUCE A FEW TORNADIC SUPERCELL THUNDERSTORMS. MOST OF
THIS STORM ACTIVITY IS EXPECTED TO END BY AROUND 3 AM.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A GENERAL DRY SOUTHWEST FLOW IN THE UPPER LEVELS WILL KEEP MUCH OF
THE AREA WARM AND DRY. THERE WILL BE ENOUGH MOISTURE AND INSTABILITY
FOR ISOLATED THUNDERSTORMS IN THE AFTERNOON AND EVENING HOURS EACH
DAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY AFTER 4 PM CLOSE TO THE DENVER
METRO AREA AND ON THE NORTHEAST PLAINS OF COLORADO AFTER 6 PM.

BAKER/ENTREKIN