DAY 2 CONVECTIVE OUTLOOK
SCO/MIDWEST WEATHER SERVICE STEVENS POINT/WHITING WI
1221 PM CDT THU AUG 30 2018
SEVERE THUNDERSTORM FORECAST DISCUSSION:
SUMMARY OF THE 311200Z - 011200Z...INFORMATION.
Scattered thunderstorms are forecast across a large portion of the region this period. While some overnight storms may be ongoing across parts
of Minnesota and Iowa, these should diminish by mid morning. More storms are expected to redevelop later in the afternoon across MInnesota
and Iowa and spread east. Some of these storms may be severe.
CATEGORICAL RISK HEADLINES...
THERE IS A LIMITED RISK FOR SEVERE THUNDERSTORMS EXTENDING FROM UPPER MI ACROSS MUCH OF WI...NORTHWEST IL AND IA.
THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS ACROSS CENTRAL AND SOUTHERN MN INTO NORTHCENTRAL IA AND A PORTION OF WESTERN WI.
Primary belt of westerlies will remain intact from the high plains east to upper NY. Meanwhile broad and stout mid laditude anticyclone from the
western Atlantic and southeast states begins to slowly retrogress westward with time. As all this occurs, upstream mid - to upper level closed low
should approach and move ashore over the Pacific northwest coast. Pieces of energy are forecast to round the base of this feature, then eject
eastward within the westerly flow aloft. It remains unclear at to what extent these pieces of energy will have on any severe weather potential for
our coverage region. At the surface, a cold front across MN will move slowly south and east into an increasingly moist and unstable warm sector
across much of WI into IA and IL.
SEVERE THUNDERSTORM FORECAST DISCUSSION...
Early in the day, broad west southwesterly 500 mb flow around 30-50 kts will exist from the northern Rockies to the Upper Midwest. As mentioned,
embedded within this flow regime, several impulses will likely transit the northern Plains and upper Mississippi Valley on Friday, one early in the
morning and another later in the day. In response to the initial, low amplitude impulse, a pair of low level jets and focused isentropic ascent may
support elevated thunderstorms across parts of eastern NE and IA and also central into northern MN during the morning. In both cases,
steep mid level lapse rates and adequate effective shear could foster isolated large hail and perhaps a couple damaging gusts, considering near
surface stability should not be too large. The greater question lies in how this potential early convection will impact thermodynamic profiles and
resultant chances for additional organized severe storms from the late afternoon through the overnight. Across central and northern MN and
adjacent ND, a front will sag southeast some through the day, but should not make considerable progress, owing to stronger deep layer ascent which
will be lagging behind the aforementioned initial impulses. As the primary trough arrives late, a secondary low level surge and increasing convergence
may foster renewed convective development in the form of a few bowing and or linear segments, primarily capable of damaging wind and sparse
large hail across MN/IA/WI during the evening.
SIGNIFICANT WEATHER CONCERN AREAS:
THE NEXT UPDATE:
The next forecast update is scheduled for 800 AM Friday.
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