560
acus01 kwns 240608
swody1
Storm Prediction Center ac 240606
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0106 am CDT Thursday may 24 2012
Valid 241200z - 251200z
..there is a slight risk of severe thunderstorms from eastern Kansas/central and northern MO
northward across Iowa...southeastern Minnesota and much of WI...
...
Late night water vapor satellite loop and short term guidance depict a
vigorous middle/upper level disturbance over Nevada/Utah rounding the base of
a larger scale upper trough encompassing much of the western U.S. This
short wave trough and its associated 75-90kt jet streak will emerge
across the Central Plains later this morning before pivoting across
the middle Missouri River valley and then ejecting northeastward toward The
Arrowhead of Minnesota by late evening.
In response to strengthening deep-layer ascent along an already well
established frontal zone draped SW-NE across the Great
Plains...surface cyclogenesis is forecast from Kansas to Iowa through the
morning. Resulting low pressure center is forecast to track rapidly
northeastward along the sharp frontal zone...from southeastern Minnesota into northwestern WI
through late afternoon...while deepening rapidly. Cold front
trailing from the low center will spread east from Iowa to northern Illinois and
south into MO through tonight but its advance and intensity should
gradually diminish over the plains as the primary upper trough moves
north into Canada and stronger large scale support for lift along
the front wanes.
Broad but weakening middle/upper level troughing will persist along the
eastern Seaboard this period with a band of more modest middle level flow
constrained to the immediate East Coast and over portions of the middle
Atlantic. Persistent swath of southerly flow off the Gulf Stream and
Caribbean Sea will maintain a very moist maritime tropical airmass
over the southeast and middle Atlantic.
..upper MS River Valley...
As has been the case with some of the more recent severe storm
episodes...limited low level moisture and strong capping will again
play a role in the evolution of severe weather potential from Iowa and
Illinois north across eastern WI and much of WI today. Despite these
limitations...there is considerable agreement amongst the latest
guidance that substantial shear and forcing will accompany the
developing low pressure system from Iowa north-northeastward across western WI later
this afternoon. Greatest concentration of thunderstorms will likely be along
the cooler side of the surface boundary...at least initially...where
parcels will be forced to achieve an level of free convection elevated above a stable
surface layer. Even in this regime...some hail and evening
occasional stronger wind gusts may occur with cells or line segments
racing northeastward at 40-50kt.
Warm sector to the east of the surface low is likely to remain
capped given plume of very warm air at middle levels streaming northeastward
ahead of the ejecting upper trough. However...overnight rain and
continued southerly flow should allow surface dewpoints to climb into the
low 60s f as far western WI. MLCAPE coincident with the deepening
surface low may reach into the 500-1000 j per kg range and...given
magnitude of forced ascent accompanying the intensifying low
pressure /deepening around 1mb/hour between 18 and 21z per latest
progs/...expect potentially dangerous and fast-moving storms to
develop. The window of opportunity for this development will be
rather small...from about 19-23z and over a relatively confined
region from extreme eastern Minnesota into western/northwestern WI. Forecast conditions in
this time and area appear supportive of a couple of possibly strong
tornadoes and/or fast-moving line segments capable of damaging
winds. Shear and instability values near the low support the current
corridor of high tornado probabilities and an upgrade to greater
probabilities/confidence is possible with the light of day and a
close inspection of overnight storm-scale guidance.
Additional surface-based storm development in the form of lines or
bows may occur through the late afternoon along the advancing cold
front. Magnitude of middle level flow directed into the developing
convection suggests that these storms may pose a threat of damaging
winds as they move east from northestern Iowa into southern WI and portions of northern
Illinois.
...
More isolated to scattered storm development could occur ahead of
the front spreading into MO from late afternoon into the evening.
Larger scale support will be waning along the front in this area.
However...any storms that can develop will do so in a sufficiently
sheared environment where warm/hot boundary layer will contribute
damaging wind potential...and perhaps some hail.
.Carbin/Mosier.. 05/24/2012
Mesoscale Discussion
678
acus11 kwns 241133
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 241133
miz000-wiz000-ilz000-iaz000-mnz000-241230-
Mesoscale discussion 0887
National Weather Service Storm Prediction Center Norman OK
0633 am CDT Thursday may 24 2012
Areas affected...a large part of WI...a small part of the Upper
Peninsula of Michigan...northestern Iowa...far southeastern Minnesota...far northwestern Illinois
Concerning...outlook upgrade
Valid 241133z - 241230z
Summary...a categorical upgrade to moderate risk will occur for a
large part of WI...a small part of the Upper Peninsula of Michigan...northestern
Iowa...far southeastern Minnesota...and far northwestern Illinois with the upcoming issuance of the
1300 UTC day 1 convective outlook.
Discussion...observational trends and latest model guidance indicate
that widespread severe winds will be possible in association with a
squall line that is forecast to cross parts of the upper MS valley
this afternoon into tonight. This line will be in association with a
strong storm system that will traverse the area during the day 1
convective period...and will also feature the threat for tornadoes
and severe hail. The anticipated coverage of severe winds will warrant the
inclusion of a moderate risk in the upcoming 1300 UTC convective
outlook...which will provide additional meteorological details
regarding this scenario.
.Cohen/corfidi.. 05/24/2012
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...MQT...grb...mkx...dvn...dlh...arx...mpx...dmx...
Latitude...Lon 46478868 45648775 44398793 43508876 42249026 42039197
43259303 45159224 46269057 46478868
