Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 281554 AAA
Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1054 AM CDT SUN AUG 28 2016
Area of low stratus and fog still hanging around from west to east
across the central portions of the forecast area. This should
continue to slowly erode and mix out into the early afternoon
hours, as daytime heating continues. May still see some scattered
to broken diurnal cumulus development, though not confident in
High pressure will slide east across the area today, then slowly to
the east tonight into Monday. Decoupling winds and dew points
remaining in the 60s should lead to another good chance for fog
later tonight into Monday morning, with dense fog possible. Will
continue to evaluate potential, and the need for a headline.
Easterly winds are expected this afternoon near Lake Michigan,
which will keep temperatures there a little cooler than inland. As
long as low clouds mix out early this afternoon, highs should get
into the upper 70s to lower 80s inland, per 925 mb temperatures.
Fog and low stratus clouds should gradually mix out by early
afternoon across Madison, Waukesha and Milwaukee, with VFR
conditions expected this afternoon. Winds will become easterly at
the eastern sites this afternoon, and southeast at Madison. May
see scattered to broken diurnal cumulus develop, but uncertainty
exists with this occurring.
Another round of fog, with dense fog possible, should occur by
later this evening into Monday morning. High pressure moving
slowly east of the area will bring light/calm winds once again,
with a moist airmass lingering. Visibilities below alternate
minimums, down to 1/2 to 1 mile, seem reasonable between 06Z and
14Z Monday. It may begin earlier.
1/4 mile or less visibilities are possible with dense fog, but
may leave out of 18Z TAFs for now, until better handle on timing
and areal extent is attained. May also see low stratus develop
with the fog, with very low ceilings near airport minimums.
Once the fog and low stratus mix out by middle to late morning on
Monday, the rest of the day should be VFR category with scattered
to broken diurnal cumulus cloud development.
Nearshore waters will remain in a light wind regime through
Monday. Moist air over the cool nearshore waters will result in
periods of fog, possibly into Monday night.
Enough breaks in the clouds last night to get a MODIS snapshot of
the lake surface temps around 07z. Lake surface temps at the time
were mostly in the mid 50s to mid 60s, with a cool spot in the
lower 50s offshore of the Ozaukee/Sheboygan county line. Surface
dew points wl remain in the 60s, resulting in areas of fog.
Light and variable winds will turn light onshore late this
morning and early afternoon, and then veer back to predominantly
offshore tonight. The fog may become dense tonight.
.PREV DISCUSSION... /Issued 245 AM CDT SUN AUG 28 2016/
TODAY AND TONIGHT...Forecast Confidence is medium.
A strong shortwave just north of Lake Superior will move east
northeast with Southern Wisconsin in the right entrance region of
the weakening upper jet as it moves off into southeast Canada.
Then a weak zonal flow extends across southern Wisconsin tonight.
Little in the way of any 700 mb upward motion until towards
sunrise in areas northwest of Madison.
700 mb west winds diminish this morning and remain light through
tonight as a weak 700/850 mb ridge builds back across southern
Wisconsin. 700 mb RH remains low but does increase a little north
areas late tonight.
Dense Fog should mix out by mid/late morning, which should give
mainly scattered cumulus, and a warm day. Light winds will become
easterly during the afternoon near Lake Michigan.
Forecast soundings show zero to 1 km CAPE increases to around 700
Joules/kg this afternoon, but has a cap around 850 mb, along with
dry air above the cap. Therefore do not expect much potential for
showers. limited moisture below the cap and this dries tonight.
As a result expect fog potential again tonight.
MONDAY - Confidence...Medium
Surface high shifts a bit to the east into the eastern Lakes. 850
high proggd vcnty of se WI or ne IL. Light wind regime likely to
allow for some morning fog. 591DM broad mid level ridging is
expected. So will keep POPS quiet...in the single digits per MOS.
925 temps rise just a smidge into the lower 20s celsius with a
better hint of a return flow.
TUESDAY - Confidence...Medium
Surface/850 boundary expected to focus a chance of shra/tsra. Mid
level flow becomes more cyclonic from the northwest though better
vorticity resides to the northeast and southwest of the CWA. So
expect low level convergence acting upon instability axis ahead of
the front to be the primary focus mechanism for convection. Main
cool push arrives Tuesday night as 925 winds turn northwest and
WEDNESDAY THROUGH SATURDAY - Confidence...Medium
Shaping up to be a rather quiet with dominating surface high. Low
level thermal trough will be in place with 925 temps both Thursday
and Friday in the low to mid teens celsius. Surface high shifts east
on Saturday to allow for a return flow and a moderation in the 925
thermal pattern to the upper teens or lower 20s celsius.
AVIATION/12Z TAFS/...Widespread IFR/LIFR in fog/stratus expected
early this morning. Vsbys will improve to VFR with morning mix-out
by mid/late morning. Winds will be light through the period with
low-level moisture bringing another good chance for fog by
midnight tonight into Monday morning.
MARINE...Will see areas of fog as high low-level moisture moves
over the cooler waters of the lake trough early morning. Expect
light east winds by afternoon.
TODAY/TONIGHT AND AVIATION/MARINE...Hentz
Monday THROUGH Saturday...Collar