Alert archive / Idaho / Special Weather Statements in 2017

Special Weather Statement, NWS Missoula, MT

May 6, 2017Lemhi County, Idaho

NWS Missoula, MT issued this special weather statement at May 6, 2017, 6:35 PM MDT for Lemhi County, Idaho. It was in force for 55 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
May 6, 2017, 6:35 PM MDT (00:35 UTC)
Expired
May 6, 2017, 7:30 PM MDT
In force
55 min
Issued by
NWS Missoula, MT

County Lemhi County, ID

The radar

The Pocatello radar (KSFX), 214 km from the middle of the area, began a volume at 00:38 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 nearest sounding before it

Great_falls, MT (KTFX), launched 00:00Z, 0.6 hours before the alert went out and 380 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-pSkew-T log-p diagram, Great_falls, MT at 00:00Z on 2017-05-07Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 442 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Great_falls, MT at 00:00Z on 2017-05-07The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -18 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
442 J/kg
Mixed-layer CIN
-81 J/kg
Mixed-layer LCL
2097 m above ground
0-6 km bulk shear
48 kt
0-1 km storm-relative helicity
-18 m²/s²
0-3 km storm-relative helicity
87 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.8

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

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

NWS Missoula, MT wrote its last area forecast discussion before this special weather statement went out at May 6, 2:42 PM MDT, 3 hours 53 minutes earlier.

Area forecast discussion, May 6, 2:42 PM MDT, 3 hours 53 minutes before
Area Forecast Discussion
National Weather Service Missoula MT
242 PM MDT Sat May 6 2017

.DISCUSSION...A few showers and thunderstorms are starting to
develop across southwest and west central Montana, and will
continue through the evening. As the shortwave moves northward,
storms are expected to continue and eventually impact northwest
Montana, generally from US 93 Missoula to Kalispell eastward, late
this evening through early Sunday morning. The stronger storms
have a history of 1/2" hail and strong gusty winds in the 40-50
mph range (perhaps stronger).

The cold front will finally push through the region mid to late
Sunday morning. This will push the boundary for convection east
of the Divide and allow a dry and cooler air mass to settle into
the Northern Rockies. Even with plenty of sun, high temperatures
will be only in the mid and upper 50s, or about 10 degrees cooler,
on Sunday. In fact, Sunday will be the coolest day of next week.
Expect dry weather through at least Wednesday.

A large cut-off low pressure system will develop across the
southwest U.S., leaving the Northern Rockies in a general weak
westerly flow with dry conditions. Late Tuesday and Wednesday,
high pressure will nudge its way into the region. This will impact
the area with temperatures back to above-normal, which will be in
the mid and upper 70s for high temps.

Thursday: a big closed low off the Pacific NW coast will
influence the break down of the ridge over our area. An increase
in moisture and instability from the ridge breakdown will be
conducive for development of afternoon/evening thunderstorms.

Beyond Thursday into next weekend, there is some uncertainty with
the models as to what to do with the low off the coast, whether
to cut it off and move it south or slowly move inland. Whatever
the case, it looks to be an unsettled period with showers in the
forecast and temperatures back down to at-or-below normal
readings.

&&

.AVIATION...Showers and thunderstorms are a possibility at KMSO,
KSMN and KBTM this evening through 07/0900z. Some of the stronger
storms this afternoon have a history of 1/2" hail and wind gusts
of 40-50 mph. In addition, expect lower visibility and ceilings
with passing storms.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

In the hours before

Local storm report, May 6, 2:13 PM MDT, 4 hours 22 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
213 PM MDT SAT MAY 6 2017

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

0138 PM     HAIL             5 ENE SULA              45.86N 113.88W
05/06/2017  M0.50 INCH       RAVALLI            MT   TRAINED SPOTTER

            SPOTTER REPORTED 0.5 INCH HAIL LASTING ABOUT
            10 MINUTES, WITH FREQUENT LIGHTNING.

&&

LV
Local storm report, May 6, 2:24 PM MDT, 4 hours 11 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
224 PM MDT SAT MAY 6 2017

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

0155 PM     TSTM WND GST     13 ENE SULA             45.93N 113.74W
05/06/2017  M66 MPH          RAVALLI            MT   MESONET

            RAWS SENSOR REPORTED 66 MPH GUST AS STORM
            MOVED THROUGH. SENSOR REPORTS HOURLY, WITH
            THE HOUR CONTAINING THIS REPORT BEING 1:09PM
            - 2:09PM MDT. ESTIMATED TIME OF GUST IS
            1:55PM MDT BASED ON STORM LOCATION.

&&

LV
Special weather statement, May 6, 2:31 PM MDT, 4 hours 4 minutes before
Special Weather Statement
National Weather Service Missoula MT
231 PM MDT SAT MAY 6 2017

MTZ007-062115-
Butte/Blackfoot Region MT-
231 PM MDT SAT MAY 6 2017

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL DEER LODGE...SILVER BOW
AND SOUTHERN POWELL COUNTIES UNTIL 315 PM MDT...

At 230 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 13 miles northeast of WISDOM to 7 miles
northeast of TWIN BRIDGES. Movement was northeast at 35 mph.

Half inch hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Butte, Anaconda, Silver Bow, Walkerville, Warm Springs, Galen,
Gregson Hot Springs, Divide, Nissler, Crackerville, Fishtrap, DEWEY,
Opportunity, Ramsay, Janney, Newcomb and Melrose.

LAT...LON 4576 11250 4568 11255 4563 11269 4575 11276
      4581 11300 4588 11310 4588 11321 4582 11328
      4581 11334 4576 11337 4580 11343 4628 11277
      4623 11259 4618 11257 4618 11251 4613 11252
      4610 11247 4589 11240 4585 11243 4575 11219
TIME...MOT...LOC 2030Z 219DEG 31KT 4580 11333 4556 11213
Local storm report, May 6, 2:57 PM MDT, 3 hours 38 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
257 PM MDT SAT MAY 6 2017

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

0242 PM     HAIL             1 W GEORGETOWN          46.20N 113.26W
05/06/2017  E1.25 INCH       DEER LODGE         MT   TRAINED SPOTTER

            TRAINED SPOTTERS ESTIMATED QUARTER AND HALF
            DOLLAR SIZED HAIL STONES. THEY WERE WORRIED
            ABOUT VEHICLE DAMAGE. DID NOT GO OUTSIDE YET
            TO CHECK VEHICLES.

&&

LV
Local storm report, May 6, 4:11 PM MDT, 2 hours 24 minutes before
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Special weather statement, May 6, 6:35 PM MDT, 0 minutes before
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The office that day

Everything else NWS Missoula, MT issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 6, 8:45 PM MDTSpecial Weather StatementMSODeer Lodge, Silver Bow75 min
May 6, 7:47 PM MDTSpecial Weather StatementMSOLemhi43 min
May 7, 4:02 AM MDTRiver Flood WarningMSOLemhi72 hr

Nearby

Special Weather Statements in Idaho, 2017Every special weather statement in 2017

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.