Alert archive / Oregon / Mesoscale Discussions in 2007

Mesoscale Discussion 1925

August 31, 20074 counties in Idaho; 12 counties in Oregon; 5 counties in Washington

The Storm Prediction Center issued this mesoscale discussion at Aug 31, 2007, 2:28 PM MDT for 4 counties in Idaho; 12 counties in Oregon; 5 counties in Washington. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 31, 2007, 2:28 PM MDT (20:28 UTC)
Expired: Aug 31, 2007, 4:30 PM MDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 21 counties

Adams County, ID, Nez Perce County, ID, Payette County, ID, Washington County, ID, Baker County, OR, Crook County, OR, Deschutes County, OR, Gilliam County, OR, Grant County, OR, Harney County, OR, Lake County, OR, Morrow County, OR, Umatilla County, OR, Union County, OR, Wallowa County, OR, Wheeler County, OR, Asotin County, WA, Benton County, WA, Columbia County, WA, Garfield County, WA, Walla Walla County, WA

The radar

The Pendleton radar (KPDT), 162 km from the middle of the area, began a volume at 20:31 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 664Aug 31, 3:05 PM MDT

The nearest sounding before it

Boise Airport, ID (KBOI), launched 12:00Z, 8.5 hours before the alert went out and 215 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2409 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 17 m²/s²
0-3 km storm-relative helicity: 53 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
ACUS11 KWNS 312028
SWOMCD
SPC MCD 312028 
IDZ000-ORZ000-WAZ000-312230-

MESOSCALE DISCUSSION 1925
NWS STORM PREDICTION CENTER NORMAN OK
0328 PM CDT FRI AUG 31 2007

AREAS AFFECTED...OR...WA...ID

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 312028Z - 312230Z

STRONG TO SEVERE THUNDERSTORM ACTIVITY IS EXPECTED TO INCREASE
ACROSS PARTS OF ERN ORE/WA AND WRN ID OVER THE NEXT FEW HOURS. A
WATCH IS POSSIBLE FOR SOME OF THESE AREAS WITHIN 1-2 HOURS.

VISIBLE SATELLITE IMAGERY AND LIGHTNING STRIKE DATA INDICATE A
GRADUAL INCREASE IN DEEP CONVECTION NOW OCCURRING FROM THE CASCADE
RANGE EWD/NEWD ACROSS MUCH OF ERN ORE. ADDITIONAL STORMS HAVE
PERSISTED ACROSS NERN WA. STORM COVERAGE AND INTENSITY ARE EXPECTED
TO INCREASE THROUGH THE AFTERNOON AS LIFT ASSOCIATED WITH A SHORT
WAVE TROUGH AND FRONTAL BAND SPREAD EWD INTO INCREASINGLY UNSTABLE
AND WEAKLY CAPPED AIR MASS. LATEST OBJECTIVE ANALYSIS DATA WAS
SHOWING POCKETS OF SBCAPE EXCEEDING 1000 J/KG ACROSS ERN ORE/WA
WHERE DIURNAL HEATING HAS BOOSTED SURFACE TEMPERATURES INTO THE 80S
F. RELATIVELY HIGH-BASED STORMS DEVELOPING ATOP A WELL-MIXED
BOUNDARY LAYER WILL POSE A THREAT FOR DAMAGING DOWNBURST
WINDS...ESPECIALLY WITHIN THE CORRIDOR OF HIGHER DCAPE VALUES
INDICATED FROM RDM AREA NNEWD ACROSS THE COLUMBIA RIVER VALLEY.
FURTHERMORE...BELT OF 50-55KT MID LEVEL FLOW SPREADING EAST WITH THE
UPPER TROUGH WILL CONTRIBUTE TO STRENGTHENING SHEAR ACROSS THE
REGION THAT SHOULD SUPPORT A FEW SUPERCELLS WITH ATTENDANT THREAT
FOR ISOLATED LARGE HAIL DEVELOPING THROUGH LATE AFTERNOON/EARLY
EVENING. A WATCH IS POSSIBLE AS THIS SCENARIO BECOMES MORE EVIDENT
IN THE NEXT 1-2 HOURS.

..CARBIN.. 08/31/2007

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MSO...BOI...OTX...PDT...MFR...

42991815 42582071 43232131 43972131 46211976 46651672
45361589 44131647

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 31, 3:02 PM MDT	Severe Thunderstorm Watch	SPC	Benewah, Bonner, Kootenai, Latah, Lewis, Nez Perce and 1 more	7 hr

Nearby

Mesoscale Discussions in Oregon, 2007 Mesoscale Discussions in Washington, 2007 Mesoscale Discussions in Idaho, 2007 Every mesoscale discussion in 2007

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.