SPC MD 463

MD 0463 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF NORTHEASTERN OR...EASTERN WA...NORTHERN ID...AND FAR NORTHWESTERN MT

Mesoscale Discussion 0463
NWS Storm Prediction Center Norman OK
0200 PM CDT Fri Apr 07 2017

Areas affected...Portions of northeastern OR...eastern WA...northern
ID...and far northwestern MT

Concerning...Severe potential...Watch unlikely 

Valid 071900Z - 072130Z

Probability of Watch Issuance...5 percent

SUMMARY...Isolated strong to locally damaging wind gusts and perhaps
some hail will be possible with developing thunderstorms through the
afternoon/early evening. Due to the marginal nature of the severe
threat, watch issuance is not expected.

DISCUSSION...Beneath a strong, cyclonically curved mid/upper-level
jet, cumulus clouds have become more agitated over the past hour
across the northern Intermountain region per recent visible
satellite imagery. Behind morning convection, some breaks in the
cloud cover have allowed surface temperatures to generally warm into
the 50s and lower 60s outside of high terrain. Although low-level
moisture remains quite limited, with precipitable water values
around 0.5 inch or less, there appears to be sufficient instability
(MUCAPE up to 500 J/kg) to support convective development this
afternoon and early evening. Steep low and mid-level lapse rates per
RAP forecast soundings will encourage efficient downward momentum
transfer in convective downdrafts, and strong to locally damaging
winds may occur with any thunderstorm. In addition, 35-40 kt of
effective bulk shear should support updraft organization within the
strongest cores, and isolated hail approaching severe levels may not
be out of the question. Overall, the severe threat is expected to
remain isolated and marginal given weak instability, and the
likelihood of watch issuance is low. Regardless, convective trends
will be monitored through the afternoon and early evening.

..Gleason/Weiss.. 04/07/2017

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

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

LAT...LON   47931822 48931740 48771590 48031504 46931481 45791523
            44671620 43931692 43841769 44051860 44671894 45851894
            47931822 

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