- Täna
- Homme
- Day Three
000
acus01 kwns 201619
swody1
Storm Prediction Center ac 201618
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1118 am CDT Sat Oct 20 2018
Valid 201630z - 211200z
..there is a marginal risk of severe thunderstorms across parts of
Southern Lower Michigan and far Northwest Ohio this afternoon...
...
A few strong storms may produce gusty winds across parts of Southern
Lower Michigan and Northwest Ohio this afternoon.
..Great Lakes vicinity...
A small marginal risk, mainly for isolated strong wind gusts, has
been added to portions of south-central and south-east lower
Michigan into far Northwest Ohio this update. A strong cold front
continues to progress east/southeast across Michigan and line of
low-topped, fast moving thunderstorms has developed ahead of the
front. Poor dewpoints and weak buoyancy will generally limit the
threat. However, surface temperatures have warmed into the low to
mid 50s and some locations are a couple of degrees warmer than
forecast. Modifying rap point forecast soundings with current
surface data indicates very steep low level lapse rates around 8-9
c/km. 0-3km flow remains somewhat marginal, generally less than 35
kt, but the steep lapse rates coupled with fast storm motion and
marginal low level flow could lead to a handful of stronger wind
gusts in the 40-50 mph range as the line of convection shifts
eastward today. For more details, reference mesoscale discussion 1588.
Elsewhere across the lower Great Lakes, showers and low-topped
thunderstorms also will be possible into parts of PA and New York.
Conditions are even less favorable across this area for any sort of
organized severe threat. An isolated waterspout may
also occur over Lake Erie this afternoon given the steep low-level
lapse rates and vertical vorticity along the reinforcing cold front.
In fact, at least a couple of water spouts have already been
reported near Lake City PA.
..southwest deserts...
Low level moistening is occurring ahead of midlevel low off the
coast of California. Isolated surface-based thunderstorms may develop in
conjunction with peak heating, though the bulk of activity is
expected overnight as stronger forcing for ascent overspreads
southern CA/NV/AZ. Any surface-based convection that can develop
earlier in the day could produce some gusty winds with steep lapse
rates and modest vertical shear profiles. However, as nocturnal
cooling occurs, overnight convection will become elevated and severe
threat is expected to remain minimal.
.Leitman.. 10/20/2018
$$
Mesoscale Discussion
000
acus11 kwns 201608
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 201608
miz000-201815-
Mesoscale discussion 1588
National Weather Service Storm Prediction Center Norman OK
1108 am CDT Sat Oct 20 2018
Areas affected...Southern Lower Michigan
Concerning...severe potential...watch unlikely
Valid 201608z - 201815z
Probability of watch issuance...5 percent
Summary...strong damaging gusts (40-50 mph) are possible over the
next several hours as a broken convective line with embedded cells
moves east across Southern Lower Michigan.
Discussion...visible satellite imagery shows a cumulus field
developing over Southern Lower Michigan where surface temperatures
are rising into the middle 50s degrees f. Radar imagery shows a
low-topped convective line with embedded cells showing weak
organizational characteristics located in a south-southwest to
north-northeast line immediately east of Grand Rapids. As a potent
mid-level shortwave trough continues to pivot southeast over the
central Great Lakes this afternoon, large-scale forcing for ascent
will maximize coincident with peak heating.
Modifying rap soundings over Southern Lower Michigan for middle 50s
surface temperatures yields a nearly 9 degree c/km 0-3 km lapse rate
because of very cool mid-level temperatures (-25 degrees c at 500
mb). Although winds in the lowest 3 km are 40 kt or lower per kgrr
VAD data, it seems plausible as the convection slowly organizes,
potential for strong gusts via horizontal momentum transport may
occur. The main threat with the strongest storms is localized wind
damage due to 40-50 mph gusts.
.Smith/guyer.. 10/20/2018
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...DTX...iwx...GRR...
Latitude...Lon 42988486 43008346 42568268 41878309 41788398 42048531
42988486
