Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KMKX 160432

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1132 PM CDT Tue Aug 15 2017


We could still see a period of MVFR/IFR fog from about 09-13z
Wednesday. Otherwise, look for mainly VFR conditions until showers
and storms arrive Wednesday evening. Winds will be light less than
10 knots through most of the TAF period.


.PREV DISCUSSION... (Issued 855 PM CDT Tue Aug 15 2017)

Look for quiet conditions across the area overnight. The high
clouds are thinning as the showers/storms over central/eastern
Iowa have dissipated. The nearest convection is over Nebraska and
western Iowa and is expected to move very little overnight. Thus,
the clearing skies may allow more fog/stratus to develop
overnight, but it should burn off fairly quickly after sunrise.
The HRRR and some of the larger scale models were bringing a band
of showers/storms into southwest Wisconsin between about 5am and 9
am with a surge of warm/moist air advection. They have backed off
a bit on this, but there are still some qpf elements being
depicted, so small chc still ok. In collaboration with upstream
offices, we decided to back off pops for Wed afternoon. Bringing a
dry period once the morning stuff dissipates and we wait for the
main surge toward evening.


Light easterly winds overnight into early Wednesday morning will
gradually turn southeast Wednesday afternoon. The winds Wednesday
night and eventually veer southwest on Thursday. Winds and waves
will approach small craft advisory levels later Wednesday night
through Thursday, especially north of Port Washington.

PREV DISCUSSION... (Issued 601 PM CDT Tue Aug 15 2017)


MVFR/IFR VSBYS due to fog are possible over parts of southern
Wisconsin later tonight, between about 07-13z Wednesday. We may
see enough high cloudiness to prevent that fog from forming. If
the high clouds thin out quicker, fog becomes more likely.
Otherwise, CIGS will remain VFR through most of the TAF period. We
could see a line of showers and possible thunderstorms push into
south central Wisconsin around 11-14z, but then dissipate by mid
to late morning. The bulk of the next round of showers and storms
associated with approaching low pressure will arrive later
Wednesday evening into Thursday morning.

PREV DISCUSSION... (Issued 300 PM CDT TUE AUG 15 2017)

TONIGHT AND WEDNESDAY - Forecast Confidence...Medium.

Mid and upper level moisture advection will occur tonight ahead of
troughing approaching from the west. This will bring an increase in
cloud cover, especially late. Some fog development is expected, but
this will be modulated by the thickness and extent of cloud
coverage. 850-700 mb layer warm advection will increase, providing
some weak forcing for ascent. The NAM/RAP and a few of the
convective allowing models suggest that scattered rain showers may
reach areas west of Madison late tonight towards morning. Will bring
some low end PoPs to these areas. These PoPs may need to be
increased if a stronger signal is seen towards precipitation among
the short term guidance during this time.

Deep layer moisture will increase from the southwest on Wednesday,
with precipitable water values reaching around 1.5 inches by
afternoon. We could see a shower or storm with building instability
(with the best instability west of Madison) during the afternoon,
otherwise the best rain chances should hold off until the evening,
when moisture transport increases and precipitable water values
climb towards 2 inches.

WEDNESDAY NIGHT THROUGH FRIDAY - Forecast Confidence...Medium
to High.

Short term guidance remains in good agreement on vigorous short wave
trof and surge of moisture advection and convergence moving rapidly
northeast across southern WI Wednesday night. Column precipitable
water will be in the 1.5 to 2" inch range which is 150 to 200
percent of normal for this time of year.  Warm cloud depth increases
to over 11k feet.  Will increase to categorical wording as expect a
swath of showers and thunderstorms to move rapidly northeast across
southern WI overnight.  Heavy rainfall will accompany the showers,
but since they will remain progressive, the flooding threat will
remain low.  Elevated CAPE over 1000 j/kg so some small hail may
accompany some of the storms.

Expect the showers and storms to move off to the east late in the
night into early Thursday.  Lingering cyclonic curvature and
lingering low to mid level moisture may trigger a few showers and
storms during the day as lapse rates increase to 7-8 degrees through
700h mb.

Quiet and dry conditions are then expected to finish off the work
week.  Temperatures continue to remain around seasonal normal.


FRIDAY NIGHT THROUGH TUESDAY - Forecast Confidence...Low to

Medium range flip-flopiness continues with the Friday/Friday night
period.  Medium range guidance however has come into better
agreement on bringing sharpening mid-level trof across WI later
Friday night into Saturday.  Precipitable water around 1.25 inches
at the time so wl continue chance pops for showers and a few storms.

Upper level steering flow backs to more zonal to WSW after Saturday
short wave moves through.  Short wave ridging in shifting winds
should keep the rest of the weekend dry.

Monday afternoon eclipse viewing remains in jeopardy as warmer air
spreads northward into the upper midwest Sunday night and Monday.
While shower and t-storm chances are very low over the western CWA,
there is a better chance for some mid/high level clouds.

The chance for showers and storms will increase Monday night and
Tuesday as another in a series of mid level waves passes through the

Temperatures for most of the period will remain near or slightly
above seasonal normal for mid-August.

AVIATION(21Z TAFS)...Low clouds and areas of fog should develop
tonight. Prevailing ceilings should mostly be MVFR, but visibilities
could drop to IFR where fog develops, especially in the WI River
valley. Prevailing VFR tomorrow, with a slight chance for a shower
or thunderstorm.

MARINE...Northeast winds this evening will veer southeast for
tonight into Wednesday, with winds and waves remaining below small
craft advisory levels. Winds may approach small craft levels
Wednesday night into Thursday as low pressure moves across Wisconsin
and towards Lake Superior.




Tonight/Wednesday and Aviation/Marine...SPM
Wednesday Night through Tuesday...SPM is the U.S. government's official web portal to all federal, state and local government web resources and services.