SPC AC 280533
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1233 AM CDT Fri Jun 28 2019
Valid 291200Z - 301200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS...UPPER MISSISSIPPI VALLEY AND NORTHEAST...
Severe thunderstorms associated with large hail and damaging wind
gusts will be possible across parts of North Dakota into Minnesota
on Saturday. Additional severe storms with damaging wind gusts may
occur across across parts of the Northeast.
An upper-level ridge will move eastward from the northern Plains
into the Upper Mississippi Valley on Saturday as southwest mid-level
flow becomes establishes across the northern High Plains. At the
surface, a cold front is forecast to advance southeastward across
the northern Plains. A very moist airmass should be in place ahead
of the front with surface dewpoints in the lower 70s F. This should
contribute to moderate to strong instability across the eastern
Dakotas and western Minnesota by Saturday afternoon. Thunderstorms
are first expected to develop in southern Saskatchewan during the
mid afternoon with convection moving southeastward across the
northern half of North Dakota and northwestern Minnesota during the
late afternoon. The storms will have access to moderate deep-layer
shear with forecast soundings showing 0-6 km shear of 45 to 55 kt.
This should support supercell development with a large-hail threat.
Wind damage will also be possible with the stronger downdrafts. Some
uncertainty exists concerning how long the severe threat will
persist into the evening. Have put the southeastern edge of the
slight risk into north-central Minnesota in case the threat lasts
into the late evening.
An upper-level trough will dig southeastward across Ontario on
Saturday as a cold front advances southeastward across the
northeastern U.S. A moist airmass is forecast ahead of the front
with surface dewpoints across southeast New York and southern New
England in the mid to upper 60s F. In response, a pocket of moderate
instability is forecast to develop by Saturday afternoon.
Thunderstorms should develop along the front and move
east-southeastward across the region during the early to mid
afternoon. Moderate deep-layer shear, veered low-level flow and
steep low-level lapse rates will be favorable for damaging wind
gusts with the stronger storms. The severe threat should move toward
the New England coastal areas by late afternoon.
...MAXIMUM RISK BY HAZARD...
Tornado: 2% - Marginal
Wind: 15% - Slight
Hail: 15% - Slight
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z