Alert archive / Colorado / Severe Thunderstorm Warnings in 1999

Severe Thunderstorm Warning 147, NWS Denver/Boulder, CO

September 3, 1999Adams County, Denver County, Weld County, Colorado

NWS Denver/Boulder, CO issued this severe thunderstorm warning at Sep 3, 1999, 4:29 PM MDT for Adams County, Denver County, Weld County, Colorado. It was in force for 41 min. 1 report came from inside the area while it was in force.

The area

The counties it named, with what was reported inside it.

The facts

Issued: Sep 3, 1999, 4:29 PM MDT (22:29 UTC)
Expired: Sep 3, 1999, 5:10 PM MDT
In force: 41 min
Issued by: NWS Denver/Boulder, CO
Area: Whole counties; the outline is the Mesonet’s reconstruction

Counties Adams County, CO, Denver County, CO, Weld County, CO

What was reported inside it

Time	Report	Where	Remark
Sep 3, 4:58 PM MDT	Hail 1	Bennett, CO

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Sep 3, 4:15 PM MDT	Tornado Watch	SPC	6 hr

The nearest sounding before it

Denver, CO (KDNR), launched 12:00Z, 10.5 hours before the alert went out and 113 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1331 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: -18 m²/s²
0-3 km storm-relative helicity: 36 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

The text of this product is not in the archive. The NWS text archive before 2002 is incomplete.

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Denver/Boulder, CO wrote its last area forecast discussion before this severe thunderstorm warning went out at Sep 3, 3:05 PM MDT, 1 hour 24 minutes earlier.

Area forecast discussion, Sep 3, 3:05 PM MDT, 1 hour 24 minutes before

AREA FORECAST DISCUSSION FOR NORTHEAST AND NORTH CENTRAL COLORADO
NATIONAL WEATHER SERVICE DENVER COLORADO
305 PM MDT FRI SEP 3 1999

MODELS CONSISTENT IN PROGRESSIVE EASTWARD MOVEMENT OF COLD UPPER
TROUGH NEXT FEW DAYS...WITH THE TREND TOWARD COOLER AND DRIER WEATHER
OVER THE CWA.

FOR TONIGHT...STILL HAVE INGREDIENTS IN PLACE FOR POTENTIAL FOR
SOME SEVERE STORMS DURING THE EVENING HOURS.  PLATTEVILLE PROFILER
SHOWING WIND SHEAR BECOMING MORE FAVORABLE...AND MODIFIED SOUNDINGS
STILL GIVING CAPES AROUND 1500 JOULES...BEST NORTHEAST OF THE DENVER
METRO AREA.  UPPER LEVELS OF THE ATMOSPHERE CONTINUE TO COOL AHEAD
OF THE UPPER TROUGH WHICH WILL CONTINUE TO DESTABILIZE THE
ATMOSPHERE.  STILL THINK THE BEST CHANCE FOR SEVERE WILL BE IN
EASTERN WELD...MORGAN AND NORTHERN WASHINGTON COUNTIES WHERE A
BOUNDARY FROM LAST NIGHTS CONVECTION RESIDES.  CONVECTION ALREADY
FIRING OVER MOUNTAINS AND FOOTHILLS IN RESPONSE TO A SHORTWAVE
ROTATING ACROSS WESTERN COLORADO.  LATEST SPEC DISCUSSION STATES THAT
A SR BOX IS FORTH COMING.  SHORTWAVE AND ASSOCIATED CONVECTION TO
PASS EAST OF CWA BY MIDNIGHT...WITH ANOTHER WEAKER SHORTWAVE PROGGED
TO ROTATE ACROSS THE NORTHERN PORTIONS OVERNIGHT.  WILL KEEP SOME
CLOUDS AND SHOWERS OVERNIGHT.  AS MAIN TROUGH PASSES OVER AREA
OVERNIGHT...GUSTY WESTERLY WINDS ALOFT TO DEVELOP.  CROSS SECTIONS
SHOW COMPONENT ALONG AROUND 30 KTS...ENOUGH TO MENTION IN MOUNTAIN
AND FOOTHILL ZONES.

ON SATURDAY...TIMING OF COLD FRONT AND ASSOCIATED SURGE WILL
INFLUENCE MAX TEMPS.  ETA AND AVN FASTER...WITH NGM MUCH SLOWER.
WILL LEAN TOWARD THE FASTER FRONTAL MOVEMENT...WHICH WILL BRING IN
THE COOLER NORTHEAST SURGE OVER THE PLAINS BY EVENING.  AS FOR
POPS...FEEL THAT THERE WILL BE ENOUGH LIFT WITH FRONT AND FAVORABLE
GEOFRONTOGENSIS AT LOW LEVELS TO OVERCOME THE DOWNWARD QG DESCENT
FOR THE CHANCES FOR RAIN.  BIGGEST CHANGE WILL BE IN THE MAX TEMPS
WHERE LOWER TO MID 70S VIA THE FAN GUIDANCE LOOK MORE REASONABLE
THAN THE FWC.  UPSLOPE TAKES HOLD OVERNIGHT AS SURFACE HIGH SLIDES
INTO AREA.  POTENTIAL FOR LOW CLOUDS AND AREAS OF FOG MOST AREAS.

CWA TO BE UNDER SUBSIDENT FLOW SUNDAY AS THE AIR ALOFT MODERATES AND
HELPS TO STABILIZE AIRMASS.  ETA AND AVN INDICATE UPSLOPE TO BE DONE
BY 18Z.  TEMPERATURES TO REBOUND SLIGHTLY WITH NO CHANCE FOR
PRECIPITATION.

IN LONGER TERM...HIGH PRESSURE TO TAKE HOLD...WITH MRF INDICATING
SIGNS OF MOISTURE RETURNING BY MIDWEEK.  LOOKS LIKE THE BETTER
CHANCE FOR THUNDERSTORMS ON WEDNESDAY.   D-L

.DEN...NONE.

In the hours before

Special weather statement, Sep 3, 10:49 AM MDT, 5 hours 40 minutes before

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Local storm report, Sep 3, 4:26 PM MDT, 3 minutes before

LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
 426 PM MDT FRI SEP 03 1999

...PRELIMINARY STORM REPORT FOR SEPTEMBER 03 1999...

TIME(MDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0350 PM    AURORA                    CO   0.75 INCH HAIL
09/03/99   ARAPAHOE

0404 PM    AURORA                    CO   1.00 INCH HAIL
09/03/99   ARAPAHOE

Local storm report, Sep 3, 4:26 PM MDT, 3 minutes before

LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
 426 PM MDT FRI SEP 03 1999

...PRELIMINARY STORM REPORT FOR SEPTEMBER 03 1999...

TIME(MDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0350 PM    AURORA                    CO   0.75 INCH HAIL
09/03/99   ARAPAHOE

0404 PM    AURORA                    CO   1.00 INCH HAIL
09/03/99   ARAPAHOE

The office that day

Everything else NWS Denver/Boulder, CO issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 2, 6:13 PM MDT	Severe Thunderstorm Warning	BOU	Morgan, Weld	47 min
Sep 2, 6:15 PM MDT	Severe Thunderstorm Warning	BOU	Weld	35 min
Sep 2, 6:52 PM MDT	Tornado Warning	BOU	Morgan, Weld	38 min
Sep 2, 7:30 PM MDT	Severe Thunderstorm Warning	BOU	Weld	45 min
Sep 2, 7:46 PM MDT	Tornado Warning	BOU	Weld	44 min
Sep 2, 8:02 PM MDT	Severe Thunderstorm Warning	BOU	Morgan, Weld	43 min
Sep 2, 8:22 PM MDT	Tornado Warning	BOU	Morgan	38 min
Sep 2, 8:31 PM MDT	Severe Thunderstorm Warning	BOU	Logan, Weld	44 min
Sep 3, 3:47 PM MDT	Severe Thunderstorm Warning	BOU	Adams, Arapahoe, Denver	43 min
Sep 3, 3:47 PM MDT	Severe Thunderstorm Warning	BOU	Weld	43 min
Sep 3, 5:02 PM MDT	Severe Thunderstorm Warning	BOU	Adams, Denver, Jefferson	43 min
Sep 3, 5:02 PM MDT	Severe Thunderstorm Warning	BOU	Boulder	43 min
Sep 3, 5:13 PM MDT	Severe Thunderstorm Warning	BOU	Morgan, Weld	32 min
Sep 3, 5:25 PM MDT	Severe Thunderstorm Warning	BOU	Weld	35 min
Sep 3, 5:45 PM MDT	Severe Thunderstorm Warning	BOU	Adams, Denver	45 min
Sep 3, 5:45 PM MDT	Severe Thunderstorm Warning	BOU	Weld	45 min
Sep 3, 5:51 PM MDT	Severe Thunderstorm Warning	BOU	Morgan	39 min

Nearby

Severe Thunderstorm Warnings in Colorado, 1999 Every severe thunderstorm warning in 1999

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive.