Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 290217
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
917 PM CDT WED SEP 28 2016

.UPDATE...

Waterspouts not expected tonight anymore over Lake Michigan. No
reports of waterspouts were received, we had several strong
velocity couplets over the open waters. One was a 70 knot gate to
gate shear off the MKE terminal doppler. Most of the couplets were
on the east end of the storms, so waterspouts would likely not be
seen from shore through the heavy rain.

&&

.AVIATION/06Z TAFS/...

Strong northeast winds winds just above the ground will lead to
marginal low level wind shear inland from Lake Michigan. Closer
to the shoreline, expect a little higher sustained northeast winds
and periodic wind gusts of 20 to 25 knots.

Periods of clouds (bases 2500-3500 ft) will be possible over
southeast WI through the overnight hours as low pressure sits over
northern Indiana and northeast6 flow spreads moisture inland.

Mainly vfr ceilings Thursday, although some brief mvfr,
especially in showers off Lake Michigan.


.MARINE...

Persistent northeast winds due to a tight pressure gradient between
high pressure nosing south out of Canada and low pressure holding
fairly stationary over the Ohio Valley will continue to produce high
waves through Thursday night. A small craft advisory is in effect.

A large delta-t over the lake, water temp - 850 temp in C, combined
with rather deep convective cloud depths will continue to bring
shower potential mainly Thursday.

&&

.PREV DISCUSSION... /Issued 327 PM CDT WED SEP 28 2016/

TONIGHT AND THURSDAY... Forecast confidence is medium.

Dry air is working into east central WI this afternoon. This air is
wrapping counter-clockwise around low pressure that is spinning over
northern Indiana. The dry air will clear out the showers and clouds
over southeast and south central WI this evening.

Low temps will range from the upper 40s over south central WI to the
upper 50s near Lake MI. Temperatures are tricky tonight because the
clear skies will help with radiational cooling. However, a strong
easterly low level jet will keep winds elevated and perhaps some
gusts will break through the weak inversion. This will keep the low
levels more mixed and help to warm the temperatures. The onshore
winds will also help to warm the temps closest to the lakeshore.

Clouds will come and go over far southeast WI overnight as waves of
vorticity and corresponding upward motion rotate around the closed
upper low. In addition, the onshore flow from Lake MI may result in
some lake clouds via lake to 850 mb temp differences of 8C. I kept
the chance of showers out of southeast WI tonight, but there is a
small chance that the batch of showers currently over southern lower
MI could clip WI. Waterspouts could accompany those showers as they
track across Lake Michigan late this evening.

THURSDAY NIGHT THROUGH SUNDAY...Forecast confidence is medium.

The main influence during this long period will be the large and
slow moving closed upper level low that will track from the Ohio
Valley to the eastern Great Lakes...a rather short distance for 3
days of travel. This will result in a very persistent forecast for
southern Wisconsin, one characterized by a steady northeast flow,
abundant cloudiness, and on and off rain showers. Highs will hold
in the 60s, with lows in the lower to mid 50s. We should see a
surge of moisture flow west across the area Friday into Friday
night as the upper low begins to lift north. Then look for the
precip to gradually dissipate as the low drifts east by Sunday.

MONDAY AND TUESDAY...Forecast confidence is medium.

In the wake of the departing the upper low, we should get under a
period of ridging that would bring mostly dry conditions early
next week. Temps will warm into the lower 70s under more sunshine
and a better wind field.

WEDNESDAY...Forecast confidence is medium.

Another low pressure system should be approaching from the west by
the middle of next week, bringing our next chance of rain.

AVIATION/00Z TAFS/...

Dry air and resultant clearing skies will spread westward across
southeast and south central WI this evening.

Strong northeast winds winds just above the ground will lead to low
level wind shear inland from Lake Michigan. Closer to the shoreline,
expect a little higher sustained northeast winds and periodic wind
gusts of 20 to 25 knots.

Periods of clouds (bases 2500-3500 ft) will be possible over
southeast WI through the overnight hours as low pressure sits over
northern Indiana and waves of energy flow westward across Lake
Michigan.

MARINE...

Persistent northeast winds due to a tight pressure gradient between
high pressure nosing south out of Canada and low pressure holding
fairly stationary over the Ohio Valley will continue to produce high
waves through Thursday night. A small craft advisory is in effect.

A large delta-t over the lake, water temp - 850 temp in C, combined
with rather deep convective cloud depths will bring favorable
waterspout conditions to southern Lake Michigan today. The low level
wind convergence axis over the lake is also helping. The
International Center for Waterspout Research model is highlighting
southern Lake Michigan for a WP threat, but the focus is clearly in
the far southern basin. Any decent convective cells over the lake
could develop a WP.  So mariners are cautioned to remain alert if on
the water through the evening hours.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...SMALL CRAFT ADVISORY until 7 AM CDT Friday for LMZ646.

     SMALL CRAFT ADVISORY until 1 AM CDT Friday for LMZ643>645.

&&

$$

UPDATE...Hentz
TONIGHT/Thursday AND AVIATION/MARINE...MRC
Thursday NIGHT THROUGH Wednesday...Davis


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