Alert archive / Utah / Severe Thunderstorm Warnings in 1999
Severe Thunderstorm Warning 47, NWS Salt Lake City, UT
NWS Salt Lake City, UT issued this severe thunderstorm warning at Aug 30, 1999, 12:48 PM MDT for Box Elder County, Utah. It was in force for 57 min. No storm report in the archive falls inside the area while it was in force.
The area
The counties it named.
The facts
- Issued
- Aug 30, 1999, 12:48 PM MDT (18:48 UTC)
- Expired
- Aug 30, 1999, 1:45 PM MDT
- In force
- 57 min
- Issued by
- NWS Salt Lake City, UT
- Area
- Whole counties; the outline is the Mesonet’s reconstruction
County Box Elder County, UT
The radar
The Salt Lake City radar (KMTX), 60 km from the middle of the area, began a volume at 18:51 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The watch it was issued in
The SPC watch in force over the same counties when this warning went out.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Aug 30, 12:30 PM MDT | Severe Thunderstorm Watch | SPC | 8 hr |
The nearest sounding before it
Salt Lake City I, UT (KSLC), launched 12:00Z, 6.8 hours before the alert went out and 129 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.
- Mixed-layer CAPE
- 137 J/kg
- Mixed-layer CIN
- -257 J/kg
- Mixed-layer LCL
- 2547 m above ground
- 0-6 km bulk shear
- 18 kt
- 0-1 km storm-relative helicity
- 149 m²/s²
- 0-3 km storm-relative helicity
- 199 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.4
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 Salt Lake City, UT wrote its last area forecast discussion before this severe thunderstorm warning went out at Aug 30, 10:30 AM MDT, 2 hours 18 minutes earlier.
Area forecast discussion, Aug 30, 10:30 AM MDT, 2 hours 18 minutes before
UTAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SALT LAKE CITY UTAH 1030 AM MDT MON AUG 30 1999 SYNOPSIS...MOISTURE WILL SURGE NORTH ACROSS UTAH TODAY ALONG WITH STRONG SOUTH WINDS...IN ADVANCE OF A COLD FRONT WILL MOVE INTO NORTHWEST UTAH EARLY TUESDAY. DISCUSSION...STRONG SURFACE PRESSURE GRADIENT ACROSS STATE COUPLED WITH STRONG WINDS ALOFT WILL RESULT IN ADVISORY LEVEL WINDS ACROSS MOST ZONES. WARNING LEVELS MAY BE REACHED WITH HELP FROM CONVECTIVE OUTFLOWS...BUT ONLY EXPECT ISOLATED EVENTS...THUS OPTED FOR ADVISORY PRODUCT. CONVECTION VERY ACTIVE IN THE FAR WEST CWFA THIS MORNING AND HAVE UPDATED POPS IN MOST ZONES FOR PERIOD 1 AND 2. NEW ETA BRINGS FRONT INTO NW CWFA BY MIDNIGHT THEN IMPLIES IT INTO UT COUNTY BY TUES MIDDAY. NOT SURE HOW FAR SOUTH FRONT WILL GO AS 700 WINDS NEVER GO AROUND TO NW. THUS THINK FRONT MAY RETREAT QUICKLY. WILL WAIT FOR MORE MODEL DATE BEFORE ADDRESSING DAY 2. SLC 552 CDC 752 BURCH .SLC...WIND ADV TIL 10PM MOST ZONES.
The office that day
Everything else NWS Salt Lake City, UT issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 29, 6:40 PM MDT | Flash Flood Warning | SLC | Garfield | 50 min |
| Aug 29, 8:14 PM MDT | Flash Flood Warning | SLC | Washington | 61 min |
| Aug 30, 1:38 PM MDT | Severe Thunderstorm Warning | SLC | Box Elder, Cache | 67 min |
| Aug 30, 2:02 PM MDT | Severe Thunderstorm Warning | SLC | Box Elder, Davis, Salt Lake, Tooele, Weber | 58 min |
| Aug 30, 3:09 PM MDT | Severe Thunderstorm Warning | SLC | Utah, Wasatch | 36 min |
| Aug 30, 4:10 PM MDT | Flash Flood Warning | SLC | Washington | 3 hr |
Nearby
Severe Thunderstorm Warnings in Utah, 1999Every 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.