- Day Three
acus01 kwns 010555
Storm Prediction Center ac 010554
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1254 am CDT Monday Sep 01 2014
Valid 011200z - 021200z
..there is a slight risk of severe thunderstorms from lower Michigan and southeastern WI
through the Midwest...middle MS valley to eastern Kansas and far northestern OK...
Isolated to scattered severe thunderstorms should develop along and
ahead of a weak cold front from parts of the southern Great Lakes
region southwestward across Indiana...Illinois...Missouri into
eastern Kansas and far northeast Oklahoma. Damaging winds and large
hail will be possible with the strongest storms...while a tornado
cannot be ruled out across the southwestern extent of the slight
risk area. A few strong wind gusts will be possible this afternoon
across far eastern Wyoming into parts of southern South Dakota and
..lower Michigan/southeastern WI to middle MS valley to southeastern Kansas/northestern OK...
A progressive shortwave trough is expected to track northeastward from the
upper MS valley through the upper Great Lakes early in the forecast
period...reaching Ontario and western Quebec by late afternoon/early
evening. Although the strongest 500-mb height falls /60-90 M/ are
forecast to spread through the northern extent of the upper Great
Lakes...30-60 meter falls should occur across the eastern WI and lower
Michigan portion of the slight risk area. Meanwhile...an upstream
shortwave trough and attendant speed maximum are expected to move from
the central rockies through the Central Plains this afternoon to the
Midwest and southern Great Lakes later Monday night.
A cold front associated with the lead shortwave trough is expected
to extend from Western Lake Superior south-southwestward through central Iowa into
central Kansas at 12z. This boundary will advance to a position from
eastern Upper Michigan through southeastern Iowa into southeastern Kansas and north central OK to
the Texas Panhandle by late afternoon. Frontal convection will likely
be ongoing at the beginning of the period...enhanced primarily by
ascent ahead of the upper MS valley shortwave trough. Additional
storms may also be ongoing at daybreak across eastern Kansas into central/
southern MO within a low-level warm air advection regime. Gusty winds and isolated hail
may occur with the early morning activity...though greater thunderstorm
coverage and severe weather threat will be possible across the
slight risk area later today.
Strongest boundary-layer heating should occur across southeastern Kansas/southwestern MO
and OK where surface temperatures will warm into the 90s. As a
result...instability is expected to be greatest along the trailing
portions of the front where the eastern extent of steep lapse rates will
contribute to moderate-strong instability /MLCAPE 2000-3000 j per
kg/. Despite weaker midlevel lapse rates and some uncertainty in
degree of surface heating...due in part to early day convective
debris...moderate instability should also develop east-northeastward from MO to
New thunderstorm development should occur from southeastern WI into lower Michigan and eastern
Iowa to Indiana from late morning into the afternoon in vicinity of
the cold front and any differential heating boundaries attendant to
early morning convection. A 50-60 knots southwesterly midlevel jet accompanying
the lead trough will result in strengthening bulk shear for the
potential for organized storms producing damaging winds and hail.
Meanwhile...thunderstorms are expected to back-build southwestward through MO to southeastern
Kansas during the middle-late afternoon as the cap weakens. Low-level
winds will remain backed to southerly into southeastern Kansas...northestern OK and southwestern MO
enhancing convergence into the cold front and potential outflow
boundary from early morning storms. Strengthening westerly midlevel
winds across Kansas/MO by late afternoon will result in strong bulk
shear for organized storms including supercells with the strong
instability supporting the potential for very large hail and strong
wind gusts. The aforementioned zone of backed low-level winds will
enhance low-level shear for a tornado threat into the early evening.
..ern Wyoming/southwestern South Dakota and western/central Nebraska...
A fast-moving midlevel impulse is expected to track east-southeastward from the
northern rockies to this discussion area by late this afternoon. Despite
surface dew points in the 40s...steep lapse rates...with 500-mb
temperatures around -15 c accompanying the impulse...will result in
marginal instability /MLCAPE 500-1000 j per kg/ this afternoon.
Thunderstorms are expected to develop within this northwest flow regime with
locally strong wind gusts being the primary threat.
acus11 kwns 010503
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 010502
Mesoscale discussion 1654
National Weather Service Storm Prediction Center Norman OK
1202 am CDT Monday Sep 01 2014
Areas affected...parts of central and eastern Kansas
Concerning...Severe Thunderstorm Watch 480...
Valid 010502z - 010630z
The severe weather threat for Severe Thunderstorm Watch 480
Summary...it does not appear out of the question that a new severe
weather watch will be needed before the currently scheduled 06z
Discussion...the Southern Plains southerly low-level jet is reaching
peak intensity /50-60+/...and enhancement of warm advection...within
the Lower/Middle tropospheric baroclinic zone on the southern periphery
of upper troughing spreading across the Central Plains ...
maintaining vigorous storm development north of Great Bend into
areas south of Emporia. The rear/western edge of stronger activity
is expected to continue gradually shifting east southeastward across
central and portions of southeastern Kansas through the 06-09z time
frame...as the low-level jet veers. Wdss-ii mesh data suggests that
stronger activity may still be producing marginally severe
hail...aided by strong shear in the cloud-bearing layer...and the
continuing presence of steep middle-level lapse rates. Even though
activity is generally rooted above a stable surface-based layer to
the north of the conglomerate outflow boundary/surface front...it
does not appear out of the question that heavy precipitation loading
and downward momentum Transfer may still contribute to occasional
strong surface gusts that could reach severe limits.
..please see www.Spc.NOAA.Gov for graphic product...
Latitude...Lon 38949825 39009710 38789557 38169472 37599508 37309653
37529784 37699880 38079933 38579938 38949825