Severe Thunderstorm Watch 487

Issued

Jul 16, 2012, 2:53 PM MDT (20:53 UTC)

Expired

Jul 16, 2012, 10:00 PM MDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

2.5 in

Strongest gust expected

60 kt

Counties Carter County, MT, Adams County, ND, Bowman County, ND, Emmons County, ND, Grant County, ND, Hettinger County, ND, Sioux County, ND, Slope County, ND, Butte County, SD, Campbell County, SD, Corson County, SD, Dewey County, SD, Harding County, SD, Lawrence County, SD, Meade County, SD, Perkins County, SD, Potter County, SD, Walworth County, SD, Ziebach County, SD

The Bismarck radar (KBIS), 183 km from the middle of the area, began a volume at 20:53 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.

Two or more tornadoes

20%

One or more EF2 to EF5 tornadoes

5%

Ten or more severe wind reports

10%

One or more gusts of 65 knots or more

20%

Ten or more severe hail reports

10%

One or more hailstones of 2 inches or more

20%

Six or more combined severe hail and wind reports

40%

• Mesoscale Discussion 1476Jul 16, 2:07 PM MDT
• Mesoscale Discussion 1478Jul 16, 5:53 PM MDT
• Mesoscale Discussion 1479Jul 16, 8:40 PM MDT

377 
WWUS20 KWNS 162058
SEL7
SPC WW 162058
MTZ000-NDZ000-SDZ000-170400-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 487
NWS STORM PREDICTION CENTER NORMAN OK
255 PM MDT MON JUL 16 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

       EXTREME SOUTHEAST MONTANA
       SOUTHWEST NORTH DAKOTA
       NORTHWEST SOUTH DAKOTA

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 255 PM UNTIL
1000 PM MDT.

HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 55
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 50 MILES SOUTH
SOUTHWEST OF BAKER MONTANA TO 30 MILES EAST NORTHEAST OF MOBRIDGE
SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...SEVERE STORMS ARE EXPECTED TO INCREASE AND DEVELOP EAST
OFF THE HIGHER TERRAIN OF SERN MT AND WRN SD OVER THE NEXT COUPLE OF
HOURS. DOWNSTREAM AIR MASS IS CHARACTERIZED BY STRONG INSTABILITY
WHERE MOIST POST-FRONTAL LOW LEVEL ELY FLOW IS TOPPED BY 25-30KT
SWLY FLOW ALOFT. RESULTING SHEAR AND THERMODYNAMIC REGIME SHOULD
SUPPORT SUPERCELLS IF STORMS CAN PERSIST AND OVERCOME REMAINING
INHIBITION EAST OF THE HIGHER TERRAIN. DESPITE WARM TEMPERATURES
ALOFT...PERSISTENT LOW LEVEL CONVERGENCE ALONG THE FRONT AND
THERMAL/TRIPLE-POINT LOW...AND MAGNITUDE OF HEATING ALONG AND SOUTH
OF THE FRONTAL ZONE...SHOULD ACT TO OVERCOME REMAINING INHIBITION
AND FAVOR AT LEAST A FEW SEVERE STORMS PRODUCING LARGE HAIL AND HIGH
WINDS SPREADING EAST NEAR THE SD/ND BORDER AREA INTO THIS EVENING.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 27025.


...CARBIN

Severe Thunderstorm Watches in South Dakota, 2012Severe Thunderstorm Watches in North Dakota, 2012Severe Thunderstorm Watches in Montana, 2012Every severe thunderstorm watch in 2012

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.