Severe Thunderstorm Watch 421

Issued

Jul 14, 2014, 2:05 PM MDT (20:05 UTC)

Expired

Jul 14, 2014, 9:00 PM MDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

1.5 in

Strongest gust expected

60 kt

The Missoula radar (KMSX), 193 km from the middle of the area, began a volume at 20:06 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

10%

One or more EF2 to EF5 tornadoes

2%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

10%

Ten or more severe hail reports

30%

One or more hailstones of 2 inches or more

10%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 1372Jul 14, 1:27 PM MDT
• Mesoscale Discussion 1383Jul 14, 5:42 PM MDT
• Mesoscale Discussion 1386Jul 14, 8:16 PM MDT

673 
WWUS20 KWNS 142003
SEL1  
SPC WW 142003
IDZ000-MTZ000-WYZ000-150300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 421
NWS STORM PREDICTION CENTER NORMAN OK
205 PM MDT MON JUL 14 2014

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 
  NORTHEAST IDAHO
  WESTERN MONTANA
  NORTHWEST WYOMING

* EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 205 PM UNTIL
  900 PM MDT.

* PRIMARY THREATS INCLUDE...
  ISOLATED DAMAGING WIND GUSTS TO 70 MPH POSSIBLE
  ISOLATED LARGE HAIL EVENTS TO 1.5 INCHES IN DIAMETER POSSIBLE

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 115
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 50 MILES NORTHWEST
OF SALMON IDAHO TO 45 MILES EAST SOUTHEAST OF WEST YELLOWSTONE
MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 417...WW 418...WW
419...WW 420...

DISCUSSION...SCATTERED THUNDERSTORMS ARE FORMING OVER NORTHEAST ID
AHEAD OF A STRONG UPPER TROUGH.  OTHER STORMS WILL FORM ACROSS THE
WATCH AREA THROUGH THE AFTERNOON AND EARLY EVENING HOURS.  STRONG
VERTICAL SHEAR AND STEEP LAPSE RATES WILL POSE A RISK OF ORGANIZED
STORMS CAPABLE OF HAIL AND DAMAGING WINDS.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 27030.


...HART

Severe Thunderstorm Watches in Montana, 2014Severe Thunderstorm Watches in Idaho, 2014Severe Thunderstorm Watches in Wyoming, 2014Every severe thunderstorm watch in 2014

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.