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Storm Prediction Center ac 180728
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0228 am CDT Tuesday Jun 18 2013
Valid 201200z - 211200z
..there is a slight risk of severe thunderstorms for most of ND/MN...Northestern
South Dakota...northwestern Iowa...
...
Large spread exists within model guidance over the handling of a
surface cold front in the northern plains /likely augmented by convective
outflow on d2/ as the NAM and majority of sref members sweep the
front much farther east than the European model (ecmwf)/GFS/UKMET/CMC on d3. This
appears in part due to the NAM ejecting the northern rockies upper-level
low northeastward towards the southern Canadian prairies by early Friday. Other
deterministic guidance remain consistent in tracking a lead
shortwave impulse northward from the northern rockies to the Canadian rockies
as an upstream vorticity maximum rotates across the northwest. This
effectively maintains the upper low over the northern intermountain
west...resulting in stalling of the surface front that may retreat
westward Thursday night into the northern High Plains.
..nrn plains...Upper Midwest...
given the aforementioned discrepancies in the handling of the
synoptic pattern...confidence is low for highlighting significant
severe or higher coverage probabilities at this time. It appears that an mesoscale convective system
will probably be ongoing at 12z/Thursday in vicinity of Montana/ND/Saskatchewan border.
This may continue to move eastward within moderate middle-level westerly flow and
perhaps redevelop/intensify east/southeastward into the diurnal heating cycle
with all modes of severe possible given a moderate to strongly
unstable downstream air mass. A Stout capping inversion and
expanding eml should limit diurnal development with southern extent along
any outflow and confine activity mainly to parts of ND and northwestern Minnesota.
Low-level warm air advection will strengthen Thursday night with a robust low level jet from the
Southern Plains to the middle-MO valley. Along the leading edge of the
capping inversion...either a continuation of diurnal convection or
development of a renewed mesoscale convective system appears possible with attendant severe
wind/hail threats.
.Grams.. 06/18/2013
