Severe Thunderstorm Warning 31, NWS Denver/Boulder, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
255 PM MDT THU JUN 11 2009

.SHORT TERM...ANOTHER ACTIVE AFTERNOON ONGOING WITH A LINE OF
SHOWERS HAVING MOVED EAST OF THE DENVER METRO AREA ALREADY.
SOUTHEASTERLY WINDS ON THE EAST SIDE OF THE CONVECTION AND AN 80
KNOT JET MAX MOVING OVERHEAD ARE COMBINING WITH THE MOIST ATMOSPHERE
AND DAYTIME HEATING TO DESTABILIZE THE AIRMASS AND PRODUCE ORGANIZED
CONVECTION.  TORNADO WATCH FOR THE PLAINS EAST OF DENVER AND THE
PALMER DIVIDE WILL BE IN EFFECT UNTIL 9 PM MDT. IT IS STILL POSSIBLE
THAT ANOTHER ROUND OF WEAKER SHOWERS MAY COME OUT OF THE MOUNTAINS
THIS EVENING AND TAP INTO UNSTABLE AIR OVER WELD COUNTY THAT HAS NOT
BEEN OVERTURNED YET.  SCATTERED THUNDERSTORMS AND SHOWERS WILL WIND
DOWN DURING THE EVENING AS THE JET STREAK ALOFT MOVES EASTWARD.
WESTERLY FLOW ALOFT OVERNIGHT SHOULD BRING A LITTLE BIT OF DRYING TO
THE URBAN CORRIDOR OVERNIGHT.

FOR FRIDAY...THE NAM SHOWS A LITTLE BIT OF RIDGING ALOFT AS MODERATE
WESTERLY WINDS ALOFT CONTINUES.  AT LOWER LEVELS...A WEAK FRONTAL
SURGE IS FORECAST TO MOVE IN LATE IN THE MORNING.  AS THE FRONT
STALLS OVER EASTERN/NORTHEASTERN COLORADO...THE STAGE COULD BE SET
FOR ANOTHER ROUND OF AFTERNOON CONVECTION.  FOR THE TIME BEING...
WILL CONTINUE WITH THE 30 PERCENT CHANCE OF THUNDERSTORMS ACROSS THE
FORECAST AREA.  MODEL SOUNDINGS CONTINUE SHOWING MODEST INSTABILITY
DURING THE AFTERNOON.  THE MOS GUIDANCE IS CALLING FOR A WARMER DAY
ON FRIDAY...IN SPITE OF THE NORTHERLY FLOW LATE IN THE MORNING.
WARMER TEMPERATURES COULD LEAD TO STRONGER INSTABILITY.  THE HIGHEST
THREAT FOR STRONG STORMS IS GOING TO DEPEND ON WHERE THE WEAK FRONT
STALLS.  THE PALMER DIVIDE WILL BE THE MOST LIKELY CANDIDATE TO
BECOME A FOCUS FOR THE AFTERNOON SHOWERS.  AS LONG AS THIS WEAK
UPPER LEVEL PATTERN REMAINS IN PLACE...FORECASTING THE SCATTERED
THUNDERSTORMS IS THE BEST THING TO DO.

.LONG TERM...THE MDLS MAINTAIN A PERSISTENT SOUTHWESTERLY FLOW ALOFT
OVER THE CWFA THROUGH THE LONG TERM.  A TROF ALONG THE WEST COAST
WILL CONTINUE SEND DISTURBANCE EMBEDDED IN THE FLOW ALOFT WHICH WILL
KEEP NORTHEAST COLORADO AN A ACTIVE PATTERN.  ON FRIDAY NIGHT...
THE MDLS PUSH A FRONTAL BOUNDARY INTO THE NORTHEASTERN PLAINS AND
URBAN CORRIDOR.  AS A RESULT...BOUNDARY LYR MSTR WILL REMAIN HIGH
OVER THE AREA.  INTERACTIVE SOUNDINGS INDICATE THE SOUNDINGS WILL
BECOME COMPLETELY SATURATED AFTER 06Z FRIDAY NIGHT.  THE NAM12 IS
ESPECIALLY GENEROUS WITH QPF AND THIS COULD BE THE RESULT OF A
PASSING SPEED MAX.  NOT SURE IF PCPN WILL BE AS WIDESPREAD AS
ADVERTISED BUT ENUF TO WARRANT BUMPING UP THE POPS SLIGHTLY...A
CARRYING OVER PCPN PAST MIDNIGHT.  ON SATURDAY...ANOTHER ACTIVE DAY
IS PROGGED.  THE TROF TO THE WEST OF THE STATE IS EXPECTED TO PUSH
ANOTHER DISTURBANCE ACROSS THE CWFA.  INTERACTIVE SOUNDINGS FCST
CAPES FM 1500-2500 J/KG.  GOOD SHEAR AS WELL WITH 80+ KTS AT 250
MB.  SOME WEAK MID LEVEL QG ASCENT AS WELL.  WITH ALL THE CLD COVER
OVHD AND FROPA FRIDAY NIGHT...I DROPPED THE TEMPERATURES BY 2-3
DEGREES.  FCST OF 80 MAY HAVE TO HOLD OFF UNTIL TUESDAY.  ALSO
INCREASED THE POPS FOR SATURDAY AS WELL AS SUNDAY.  LOW LEVEL POOL
OF MSTR CONTINUE OVER THE NERN PLAINS ON SUNDAY...WITH A TROF TO THE
WEST.  SOUTHWESTERLY FLOW ALOFT CONTINUES INTO NEXT WEEK WITH A
CLOSED LOW FORMING OVER SRN CA.  WEAK DISTURBANCES WILL CONTINUE TO
AGITATE TO AMS OVER NERN CO AND TRIGGER TSTMS...ESPECIALLY IN THE
AFTN AND EVNG HOURS.  HARD TO DISCERN TOO MANY DETAIL BEYOND 48 HRS
SO ANY ADJUSTMENTS TO THE GRIDS WILL BE MINOR.

&&

.AVIATION...THUNDERSTORMS HAVE MOVED EAST OF THE AIRPORT AT THIS
TIME BUT WILL CONTINUE AFFECTING THE EASTERN GATES FOR A COUPLE MORE
HOURS.  A FEW SHOWERS MAY STILL MOVE OUT OF THE MOUNTAINS DURING THE
EVENING...BUT CHANCES FOR ADDITIONAL STRONG STORMS AFFECTING DENVER
AREA AIRPORTS LOOKS LOW.  DRIER AIR MOVING OUT OF THE MOUNTAINS THIS
EVENING SHOULD KEEP ANY LOW CLOUDS AND STRATUS OVERNIGHT WELL EAST
OF DENVER.  VFR CIGS AND VSBYS SHOULD LAST ALL NIGHT.  ON FRIDAY...A
WEAK FRONTAL SURGE WILL MOVE INTO DENVER AROUND 18Z.  ANOTHER ROUND
OF THUNDERSTORMS ARE EXPECTED DURING THE AFTERNOON WITH MVFR CIGS.

&&

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

KDRBY/COOPER

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
1053 AM MDT THU JUN 11 2009

COZ030>051-121200-
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-
1053 AM MDT THU JUN 11 2009

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

.DAY ONE...TODAY AND TONIGHT

SHOWER AND THUNDERSTORM ACTIVITY IS EXPECTED TO INCREASE AGAIN THIS
AFTERNOON ACROSS NORTHEAST COLORADO.  A VERY MOIST AIRMASS REMAINS
IN PLACE OVER COLORADO WITH EASTERLY AND SOUTHEASTERLY WINDS HELPING
TO HOLD MOISTURE AGAINST THE FOOTHILLS.  EVEN THOUGH IT HAS BEEN
MOSTLY CLOUDY THIS MORNING...ENOUGH HEATING IS EXPECTED TO CAUSE THE
AIRMASS TO BECOME UNSTABLE DURING THE AFTERNOON HOURS.  AN UPPER
LEVEL WEATHER DISTURBANCE WILL ALSO BE MOVING OVER THE REGION...
CAUSING STORMS TO BECOME MORE ORGANIZED.  SOME STORMS MAY BECOME
SEVERE OVER THE NORTHEAST PLAINS THIS AFTERNOON WITH DAMAGING HAIL
LARGER THAN ONE INCH IN DIAMETER...DAMAGING GUSTY WINDS AND POSSIBLY
A BRIEF TORNADO.  LOCALLY HEAVY RAINFALL WITH THUNDERSTORMS MAY ALSO
CAUSE LOCAL FLOODING PROBLEMS.  RAINFALL RATES UP TO ONE INCH IN 30
MINUTES OR LESS WILL BE POSSIBLE.

ALL AREAS EAST OF THE FRONT RANGE FOOTHILLS WILL HAVE THE CHANCE TO
SEE SEVERE THUNDERSTORMS DEVELOP...ALTHOUGH AREAS EAST OF A FORT
MORGAN TO LIMON LINE WILL NOT SEE STRONG THUNDERSTORM ACTIVITY UNTIL
AFTER 3 PM.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

AN UNSETTLED WEATHER PATTERN WILL REMAIN IN PLACE THROUGH EARLY NEXT
WEEK WITH A CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS EACH DAY.
THERE WILL ALSO BE A THREAT OF A FEW SEVERE STORMS EACH DAY OVER THE
PLAINS AND FRONT RANGE URBAN CORRIDOR.  LOW LEVEL MOISTURE COMBINED
WITH DAYTIME HEATING AND INSTABILITY...ALONG WITH SUFFICIENT WIND
SHEAR IN THE ATMOSPHERE...WILL KEEP THE THREAT OF SEVERE
THUNDERSTORMS IN THE FORECAST.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED AFTER 1230 PM.

DANKERS/COOPER

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PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE DENVER CO
804 PM MDT THU JUN 11 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0802 PM     HAIL             SEVERANCE               40.52N 104.85W
06/11/2009  M0.88 INCH       WELD               CO   AMATEUR RADIO

0745 PM     HAIL             4 NE FORT COLLINS       40.60N 105.01W
06/11/2009  M0.88 INCH       LARIMER            CO   TRAINED SPOTTER

0445 PM     HAIL             4 N BUCKEYE             40.88N 105.10W
06/11/2009  M2.50 INCH       LARIMER            CO   TRAINED SPOTTER

0429 PM     HAIL             4 N BUCKEYE             40.88N 105.10W
06/11/2009  M1.00 INCH       LARIMER            CO   TRAINED SPOTTER

0230 PM     HAIL             DEER TRAIL              39.62N 104.04W
06/11/2009  M1.00 INCH       ARAPAHOE           CO   TRAINED SPOTTER

0151 PM     HAIL             8 SE ARAPAHOE PARK      39.55N 104.60W
06/11/2009  M1.00 INCH       ELBERT             CO   TRAINED SPOTTER

0143 PM     HAIL             12 S STRASBURG          39.56N 104.30W
06/11/2009  M1.00 INCH       ELBERT             CO   TRAINED SPOTTER

0142 PM     HAIL             N PARKER                39.51N 104.76W
06/11/2009  M1.50 INCH       DOUGLAS            CO   TRAINED SPOTTER

            ALSO LOTS OF QUARTER SIZE HAIL

0126 PM     HAIL             PARKER                  39.51N 104.76W
06/11/2009  M0.75 INCH       DOUGLAS            CO   AMATEUR RADIO

0126 PM     HAIL             E PARKER                39.51N 104.76W
06/11/2009  M0.88 INCH       DOUGLAS            CO   AMATEUR RADIO

&&

JK

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DENVER CO
1013 PM MDT THU JUN 11 2009

COZ036-039-040-120500-
JEFFERSON AND WEST DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR
CREEK/NORTHEAST PARK COUNTIES BELOW 9000 FEET CO-
NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE
COUNTIES/EAST BROOMFIELD COUNTY CO-
BOULDER AND JEFFERSON COUNTIES BELOW 6000 FEET/WEST BROOMFIELD
COUNTY CO-
1013 PM MDT THU JUN 11 2009

THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A SIGNIFICANT
WEATHER ADVISORY FOR

  NORTHEASTERN JEFFERSON COUNTY
  WESTERN ARAPAHOE COUNTY
  WESTERN ADAMS COUNTY
  DENVER COUNTY
  BROOMFIELD COUNTY

AT 1010 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
THUNDERSTORM CAPABLE OF PRODUCING MARBLE SIZE HAIL...AND WIND GUSTS
TO AROUND 40 MPH.  THIS STORM WAS LOCATED OVER GOLDEN...OR 14 MILES
WEST OF DENVER...MOVING EAST AT 20 MPH.

LOCATIONS IN THE ADVISORY INCLUDE BUT ARE NOT LIMITED TO WHITE RANCH
OPEN SPACE...FEDERAL HEIGHTS...WHEAT RIDGE...WESTMINSTER...
THORNTON...NORTHGLENN...NORTHERN LAKEWOOD...GOLDEN...DENVER...
COMMERCE CITY...BROOMFIELD AND ARVADA.

THIS STORM HAS PRODUCED MARBLE SIZE HAIL AND BRIEF HEAVY RAIN IN
THE FOOTHILLS WEST OF GOLDEN.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS STORM WILL PRODUCE DANGEROUS CLOUD-TO-GROUND LIGHTNING. IF
OUTDOORS...STAY AWAY FROM ISOLATED HIGH OBJECTS SUCH AS TREES AND
MOVE INDOORS IF POSSIBLE. WHEN INDOORS...STAY AWAY FROM WINDOWS AND
DOORS AND AVOID USING LAND LINE TELEPHONES UNLESS IT IS AN EMERGENCY.
TRY TO UNPLUG UNNECESSARY ELECTRICAL APPLIANCES BEFORE THE
THUNDERSTORM APPROACHES. REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE
IN DANGER OF BEING STRUCK BY LIGHTNING.

&&

LAT...LON 3994 10496 3966 10489 3970 10525 3987 10530
TIME...MOT...LOC 0410Z 266DEG 17KT 3973 10522

GIMMESTAD

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DENVER CO
1040 PM MDT THU JUN 11 2009

COZ040-045-120530-
CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES CO-
NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE
COUNTIES/EAST BROOMFIELD COUNTY CO-
1040 PM MDT THU JUN 11 2009

THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A SIGNIFICANT
WEATHER ADVISORY FOR

  NORTHERN ARAPAHOE COUNTY
  ADAMS COUNTY
  NORTHEASTERN DENVER COUNTY

AT 1038 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
THUNDERSTORM CAPABLE OF PRODUCING MARBLE SIZE HAIL...AND WIND GUSTS
TO AROUND 40 MPH.  THIS STORM WAS LOCATED OVER NORTHEASTERN
DENVER...MOVING EAST AT 20 MPH. ANOTHER LINE OF STORMS EXTENDED FROM
BENNETT TO 10 MILES NORTHEAST OF BYERS.

LOCATIONS IN THE ADVISORY INCLUDE BUT ARE NOT LIMITED TO
WATKINS...STRASBURG...SHAMROCK...MANILA VILLAGE...LEADER...BYERS...
BENNETT...DENVER INTERNATIONAL AIRPORT...EASTERN THORNTON...
NORTHEASTERN DENVER...COMMERCE CITY AND NORTHERN AURORA.

THIS STORM HAS PRODUCED BRIEF BUT VERY HEAVY RAINS...UP TO THREE
QUARTERS OF AN INCH IN 10 MINUTES...IN COMMERCE CITY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS STORM WILL PRODUCE DANGEROUS CLOUD-TO-GROUND LIGHTNING. IF
OUTDOORS...STAY AWAY FROM ISOLATED HIGH OBJECTS SUCH AS TREES AND
MOVE INDOORS IF POSSIBLE. WHEN INDOORS...STAY AWAY FROM WINDOWS AND
DOORS AND AVOID USING LAND LINE TELEPHONES UNLESS IT IS AN EMERGENCY.
TRY TO UNPLUG UNNECESSARY ELECTRICAL APPLIANCES BEFORE THE
THUNDERSTORM APPROACHES. REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE
IN DANGER OF BEING STRUCK BY LIGHTNING.

&&

LAT...LON 3979 10371 3970 10371 3970 10491 3994 10492
      3997 10371
TIME...MOT...LOC 0438Z 273DEG 17KT 3979 10487

GIMMESTAD

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE DENVER CO
1104 PM MDT THU JUN 11 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1059 PM     HAIL             1 N PARKER              39.52N 104.76W
06/11/2009  M1.00 INCH       DOUGLAS            CO   TRAINED SPOTTER

1055 PM     HAIL             2 E BENNETT             39.76N 104.39W
06/11/2009  M0.75 INCH       ADAMS              CO   TRAINED SPOTTER

            4 INCHES OF HAIL ON THE ROAD.

0802 PM     HAIL             SEVERANCE               40.52N 104.85W
06/11/2009  M0.88 INCH       WELD               CO   AMATEUR RADIO

0745 PM     HAIL             4 NE FORT COLLINS       40.60N 105.01W
06/11/2009  M0.88 INCH       LARIMER            CO   TRAINED SPOTTER

0445 PM     HAIL             4 N BUCKEYE             40.88N 105.10W
06/11/2009  M2.50 INCH       LARIMER            CO   TRAINED SPOTTER

0429 PM     HAIL             4 N BUCKEYE             40.88N 105.10W
06/11/2009  M1.00 INCH       LARIMER            CO   TRAINED SPOTTER

0230 PM     HAIL             DEER TRAIL              39.62N 104.04W
06/11/2009  M1.00 INCH       ARAPAHOE           CO   TRAINED SPOTTER

0151 PM     HAIL             8 SE ARAPAHOE PARK      39.55N 104.60W
06/11/2009  M1.00 INCH       ELBERT             CO   TRAINED SPOTTER

0143 PM     HAIL             12 S STRASBURG          39.56N 104.30W
06/11/2009  M1.00 INCH       ELBERT             CO   TRAINED SPOTTER

0142 PM     HAIL             N PARKER                39.51N 104.76W
06/11/2009  M1.50 INCH       DOUGLAS            CO   TRAINED SPOTTER

            ALSO LOTS OF QUARTER SIZE HAIL

0126 PM     HAIL             PARKER                  39.51N 104.76W
06/11/2009  M0.75 INCH       DOUGLAS            CO   AMATEUR RADIO

0126 PM     HAIL             E PARKER                39.51N 104.76W
06/11/2009  M0.88 INCH       DOUGLAS            CO   AMATEUR RADIO

&&

JK