Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 280432
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1132 PM CDT Tue Jun 27 2017

.UPDATE...


&&

.AVIATION(06Z TAFS)...

VFR conditions tonight as early morning clouds increase ahead of
an approaching area of showers and thunderstorms. LLWS will
develop during this time but will dissipate by late morning on
Wednesday as breezy south winds develop at the surface. An area of
showers and scattered thunderstorms will move east across
southern Wisconsin through the day with additional development of
strong to severe storms Wednesday late afternoon or evening.
Areas of MVFR cigs and IFR vsbys will be likely in showers or
thunderstorms.


&&

.PREV DISCUSSION... (Issued 931 PM CDT Tue Jun 27 2017)

UPDATE...

Latest HRRR still showing showers/thunderstorms moving into south
central Wisconsin around 7 am, and affecting all of the area
through the late morning. The new NAM is just a little slower, and
has much of the late afternoon and evening re-development across
Northern Illinois, with a second area more across central and
northeast Wisconsin. Strong low level shear with this second area,
with the severe weather threat still looking favorably.

AVIATION...(00Z TAFS)

VFR conditions tonight until early morning as clouds increase
ahead of an approaching area of showers and thunderstorms. LLWS
will develop over south central WI during this time but will
dissipate by late morning on Wednesday as breezy south winds
develop at the surface. An area of showers and scattered
thunderstorms will move east across southern Wisconsin through the
day with additional development of strong to severe storms Wed
eve. Areas of MVFR cigs and IFR vsbys will be possible around and
after any showers or storms.

MARINE...

A Small Craft Advisory is in effect for Wed-Wed night due to
breezy south winds and high waves on Wednesday with the breezy
winds shifting southwest Wednesday night.

BEACHES...A Beach Hazard Statement will likely be needed for
Wed-Wed eve due to breezy sly winds and high waves. Dangerous
structural and longshore currents will likely develop. especially
north of port washington.

PREV DISCUSSION... (Issued 237 PM CDT Tue Jun 27 2017)

SHORT TERM...

Tonight through Friday...Forecast confidence medium.

Sly flow and warm advection will begin tnt but will increase on
Wed when a strong sly LLJ to the west veers to swly at 50-60 kts
as it shifts ewd across srn WI. A shortwave trough will pass
during this time providing upper support. So overall, moderate to
strong warm advection and Q-vector convergence expected for Wed
and lingering into Wed eve. The CAPE will not become appreciable
until late Wed aft-eve although sfc based convection is
questionable due to clouds and cooler temps during the daytime
hours. Thus the best chances for strong or severe storms will be
the evening as warm, moist advection continues via a veering LLJ.
If sfc based convection does occur then all severe threats
including tornadoes would be possible. Some concern for training
convection Wed eve due to the veering LLJ becoming more aligned
with the upper flow, so at least a minor flash flood threat will
be possible. A cold front will gradually pass late Wed nt-Thu AM
with the focus for convection remaining mostly over IL/IA for Thu
and Thu eve, although will still mention chances of tstorms due to
close proximity to the front.

A shortwave trough and compact sfc low will track into se WI late
Thu nt and Fri AM bringing widespread showers and tstorms to srn
WI. The severe threat will likely stay south where higher CAPE
values will be present. The average rainfall expected through Fri
will range from 1.40-2.25 inches with the usual locally higher
amounts. Some rivers may reach minor flood stage due to this.

LONG TERM...Saturday through Tuesday...Forecast confidence low to
medium.

A fairly large upper trough will reside over Ontario, Canada and
the nrn Great Lakes for the weekend. Shortwave troughs will rotate
around the large upper trough into srn WI bringing chances of
showers and tstorms. For early next week it appears a shortwave
trough and low pressure area will remain mainly to the south as it
tracks ewd.

AVIATION(18Z TAFS)...Sct060 cumulus this afternoon and broken at
times through the middle of the afternoon in far ern WI.
Otherwise mo clear skies and VFR conditions tnt until early
morning west of KMSN where clouds will increase ahead of an
approaching area of showers and tstorms. LLWS will develop over
south central WI during this time but will dissipate by late
morning on Wed as breezy sly winds develop at the surface. An area
of showers and sct tstorms will move ewd across srn WI through
the day with additional development of strong to severe storms Wed
eve. Areas of MVFR cigs and vsbys will be possible around and
after any showers or storms. Much lower cigs and vsbys within
tstorms.

MARINE...A Small Craft Advisory is in effect for Wed-Wed nt due
to breezy sly winds and high waves on Wed with the breezy winds
shifting swly for Wed nt.

BEACHES...A Beach Hazard Statement will likely be needed for
Wed-Wed eve due to breezy sly winds and high waves. Dangerous
structural and longshore currents will likely develop.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory from 9 AM Wednesday to 6 AM CDT Thursday
     for LMZ643>646.

&&

$$

Update...Hentz
Tonight/Wednesday and Aviation/Marine...Gehring
Wednesday Night through Tuesday...Gehring


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