Alert archive / Washington / Mesoscale Discussions in 2017

Mesoscale Discussion 67

January 17, 2017Morrow County, Umatilla County, Oregon; 9 counties in Washington

The Storm Prediction Center issued this mesoscale discussion at Jan 17, 2017, 5:47 PM PST for Morrow County, Umatilla County, Oregon; 9 counties in Washington. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Jan 17, 2017, 5:47 PM PST (01:47 UTC)
Expired: Jan 17, 2017, 11:45 PM PST
In force: 6 hr
Issued by: the Storm Prediction Center

Counties Morrow County, OR, Umatilla County, OR, Adams County, WA, Benton County, WA, Columbia County, WA, Douglas County, WA, Franklin County, WA, Grant County, WA, Lincoln County, WA, Spokane County, WA, Walla Walla County, WA

The radar

The Pendleton radar (KPDT), 97 km from the middle of the area, began a volume at 01:49 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 00:00Z, 1.8 hours before the alert went out and 250 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: 1426 m above ground
0-6 km bulk shear: 58 kt
0-1 km storm-relative helicity: 272 m²/s²
0-3 km storm-relative helicity: 299 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

279 
ACUS11 KWNS 180147
SWOMCD
SPC MCD 180147 
WAZ000-ORZ000-180745-

Mesoscale Discussion 0067
NWS Storm Prediction Center Norman OK
0747 PM CST Tue Jan 17 2017

Areas affected...Eastern Washington...North-central/Northeast Oregon

Concerning...Freezing rain 

Valid 180147Z - 180745Z

SUMMARY...Mixed precipitation will overspread the area this evening.
Snow and sleet will be possible across the northern portion of the
area initially, while freezing rain is expected to become
established further south, with rates around 0.05 inches per hour
possible.

DISCUSSION...At 0130Z, a large precipitation shield is beginning to
spread east of the Cascades into portions of eastern Washington and
northern Oregon. With very cold temperatures in the 15-25F range
currently in place, an initial precipitation type of snow or sleet
is possible, especially across the northern portion of the MCD area
where a less substantial warm nose is in place. However, continued
warm advection above an increasingly shallow subfreezing layer will
eventually result in a changeover to freezing rain across the bulk
of the MCD area, such as what has already occurred around Yakima.
Freezing rain rates of up to 0.05 inches per hour will be possible,
with ice accretion likely to be rather efficient given the
antecedent cold airmass that is in place.

..Dean.. 01/18/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...OTX...PDT...

LAT...LON   46352065 46942056 47432023 47961965 48051878 47981806
            47601732 46621765 45961815 45811827 45541872 45421907
            45421940 45401994 45602037 46352065

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jan 18, 4:00 AM PST	Mesoscale Discussion	SPC	Gilliam, Morrow, Sherman	3 hr

Nearby

Mesoscale Discussions in Washington, 2017 Mesoscale Discussions in Oregon, 2017 Every mesoscale discussion 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.