Alert archive / Washington / Severe Thunderstorm Warnings in 1997

Severe Thunderstorm Warning 28, NWS Spokane, WA

July 21, 1997Whitman County, Washington; Latah County, Idaho

NWS Spokane, WA issued this severe thunderstorm warning at Jul 21, 1997, 3:26 PM PDT for Whitman County, Washington; Latah County, Idaho. It was in force for 64 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: Jul 21, 1997, 3:26 PM PDT (22:26 UTC)
Expired: Jul 21, 1997, 4:30 PM PDT
In force: 64 min
Issued by: NWS Spokane, WA
Area: Whole counties

Counties Latah County, ID, Whitman County, WA

The radar

The Spokane radar (KOTX), 99 km from the middle of the area, began a volume at 22:29 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

Spokane, WA (KOTX), launched 12:00Z, 10.4 hours before the alert went out and 108 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: 429 J/kg
Mixed-layer CIN: -207 J/kg
Mixed-layer LCL: 1624 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 4 m²/s²
0-3 km storm-relative helicity: 78 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 Spokane, WA wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 21, 1:57 PM PDT, 1 hour 29 minutes earlier.

Area forecast discussion, Jul 21, 1:57 PM PDT, 1 hour 29 minutes before

EASTERN WASHINGTON AND NORTH IDAHO AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WASHINGTON
130 PM PDT MON JUL 21 1997

THUS FAR..ALL TS OVR CWA HAVE BEEN HI-BASED (10-11 kft). FROM
PERSONAL OBSERVATIONS TDY..ALL CURRENT FORCING IS CONFINED TO MID-HI
LVLS. NEG TILT TROF CONTS SENDING WK 'PUSHES' ACROSS CWA..WITH WHAT
APPEARS TO BE THE FRONT EDGE OF THE STRONGEST OF THESE NOW
APPROACHING W SIDE CASCADES. THE OBVIOUS ISSUE THIS FCST PACKAGE MUST
ADDRESS IS WHETHER THE STRONGEST FORCING MECHANISM WILL REMAIN
COHERENT AS PROPAGATES TO E SIDE..AND ITS ABILITY TO ENGAGE (INTO
CONVECTIVE PLUMES) AMPLE MSTR IN VERY LOWEST LAYER OF PBL. THE
PROBLEM IS COMPOUNDED BY THE FACT THE RMNDR OF THE PBL IS QUITE DRY.

12Z Eta/AVN/15Z Meso-Eta INITIALIZATIONS REAL NICE. HAVE GOOD CAPTURE
3-D TROPOSPHERIC STRUCTURE. ATTM MDL SOLUTIONS DEPICTING REAL-WORLD
SITU WELL. DONT HAVE TIME FOR MODEL INTER-COMPARISON..BUT WILL
MENTION THAT PREFER SOLUTIONS OF Eta/Meso-Eta.

FROM WHAT CAN GLEAN FROM SAT AND W SIDE METARS..CD POOL W SIDE
APPEARS TO BE REASONABLY DEEP. IS EVIDENCE OF SPILLAGE OVR CASCADE
CREST ATTM. BELIEVE THAT CD POOL..AND ATTENDANT FORCING MECHANISM
WILL REMAIN COHERENT AS PROPAGATES ACROSS CWA THIS AFTERNOON AND
EVENING. THE THERMAL GRADIENT SUGGESTS THIS FEATURE HAS MDT
STRENGTH..THE QUESTION IS..IS THE APPARENT MSTR CONTENT OF THE PBL
BIASED BY SFC DEW POINTS. I THINK THE ANSWER TO THAT QUESTION IS YES.
SO THE FOLLOWING IS THE SCENARIO I PROPOSE (VERY MUCH LIKE THAT OF
KBOI):

MAINLY MID-HI LVL CONVECTION..WITH DRY-TYPE MICROBURST ENVIRONMENT..
AND OCCASIONAL LIGHTNING. ANY TS THAT APPROACH SVR WILL BE MAINLY BE
CONFINED TO NRN ID..DUE TO HIGH LVL HEAT/MSTR SOURCE OF MTNS THIS
AREA..ALONG WITH ADDITIONAL LIFT MECHANISM. TS TO END THIS EVE CNTRL
BASIN..AROUND 04Z FOR ERN WA S OF SPOKANE COUNTY..AND 07-08Z TIME
FRAME FOR NRN ID.

FOR RMNDR FCST..DRY/SOMEWHAT COOLER HI PRESSURE BUILDS OVR
AREA..REDUCING DAYTIME TEMPS TO SLIGHTLY BLO NORMAL.

DRIFE

...PRODUCTS BELOW ARE PRELIMINARY AND SUBJECT TO CHANGE...
...PLEASE SEE SEACCFSEA AND ZONE FORECAST PRODUCTS...

GEG 057/082/055/086 3100
CQV 059/088/057/091 3100
S86 055/080/052/083 4100
WWP 055/079/052/082 4100
COE 058/080/054/083 4100

The office that day

Everything else NWS Spokane, WA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 21, 3:26 PM PDT	Severe Thunderstorm Warning	OTX	Whitman	49 min
Jul 21, 3:54 PM PDT	Severe Thunderstorm Warning	OTX	Spokane	51 min
Jul 21, 4:15 PM PDT	Severe Thunderstorm Warning	OTX	Ferry	45 min
Jul 21, 4:56 PM PDT	Tornado Warning	OTX	Stevens	49 min

Nearby

Severe Thunderstorm Warnings in Washington, 1997 Severe Thunderstorm Warnings in Idaho, 1997 Every severe thunderstorm warning in 1997

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.