Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 191529 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1029 AM CDT Sun Aug 19 2018

.UPDATE...

Allowed the Dense Fog Advisory to end at 9 AM CDT across portions
of the area. There may still be patchy dense fog toward the
Reedsburg and Wisconsin Dells areas for another hour or two.
Otherwise, any lingering fog will mix out with daytime heating by
early this afternoon.

Diurnal cumulus clouds should be scattered to broken into this
afternoon, as daytime heating increases. Winds will east to
southeast into the afternoon near Lake Michigan. Highs should
reach the lower 80s inland, with slightly cooler values near the
lake.

May see patchy fog later tonight, though it should not be as
widespread as this morning, with middle to high clouds moving into
the region.

Still looks like there will be a good shot at heavy rainfall
across portions of the area Monday afternoon into Monday night.
Latest CAMs suggest that convection will pivot across southern
and eastern parts of the area during this period.

High precipitable water values, with moist adiabatic and
saturated forecast soundings, will bring a favorable heavy
rainfall and possible flooding/flash flooding setup. Some of this
may occur over parts of the area that already has seen flooding
and heavy rainfall from last Thursday and Friday. Will consider
parts of the area for a Flood Watch for Monday afternoon/night.

&&

.MARINE...

Light east to southeast winds are expected into this afternoon
across the nearshore waters of Lake Michigan. Waves will be light,
generally 1 foot or less.

Onshore winds will increase later tonight into Monday night,
before backing north early Tuesday morning. Gusty north to
northwest winds are then expected Tuesday into Tuesday night,
before weakening, with low pressure passing by to the south.

This period will see increasing waves, into the 2 to 4 foot range
Monday, and 3 to 5 feet Monday night. Waves should remain in the
3 to 6 foot range Tuesday into Tuesday night, highest toward the
open waters of Lake Michigan. A Small Craft Advisory will likely
be needed for Monday night into Tuesday night.

&&

.PREV DISCUSSION... (Issued 628 AM CDT Sun Aug 19 2018)

UPDATE...

Fog continues across the central portion of the forecast area.
This should dissipate quite rapidly between 8 and 9 AM.

AVIATION(12Z TAFS)...

Dense fog will remain a concern for another hour or two at the
terminals, with the exception of KMKE, where fog has stayed to the
west. Fog is expected to dissipate rather quickly between 8 and 9
AM, with VFR then expected for the rest of the day.

Winds will increase from the east and southeast this evening into
the overnight hours, as low pressure approaches from the west. A
few gusts will be possible at MKE, with a steady breeze elsewhere.
Precipitation will begin to move toward the area tomorrow
morning, but the terminals should remain dry until after 12Z.

PREV DISCUSSION... (Issued 246 AM CDT Sun Aug 19 2018)

DISCUSSION...

Early this Morning through Tonight...Forecast Confidence is
High...

Fog is again a concern this morning across the area. Fog is fairly
widespread as of 2 AM, but visibilities have been somewhat
variable, ranging from 1 to 2 miles to a 1/4 mile. Will continue
to keep an eye on vis trends and potential need for a Dense Fog
Advisory at some point.

Fog will lift within a few hours of sunrise, with today likely to
be quite similar to yesterday, with highs around 80.

Southeast winds will start to increase this evening, continuing
through the overnight hours as low pressure deepens to our west.
Precipitation will start to move into the far southwestern edge of
the forecast area around sunrise Monday morning.

Monday through Tuesday - Confidence...Medium
Closed 500 millibar low vicinity of Omaha or just south is proggd
to open into a more progressive wave as it heads east/northeast
this period passing east of the area early Tuesday. Considerable
moisture will advect north/northwestward ahead of the low in the
amplifying thermal ridge area/warm conveyor belt region ahead f
the advancing low. This in combo with increasing dcva with the
advancing mid level trough will lead to widespread rain and
thunderstorms. A modest upper jet is proggd ahead of the low with
enhanced divergence within this left exit region later Monday into
Monday evening. Still looks like a decent amount of rain with
this system as appreciable cyclogenesis tracks across or just
south of se WI. The GFS which had been a much weaker and further
south solution has really joined forces with the earlier
advertised track/strength of the GEM/ECMWF with the consensus
pointing to this low tracking through the extreme southeast
WI/extreme northeast Illinois vicinity. Progs still keying on
Monday afternoon into at least parts of Monday night for the
heaviest precip potential. This system has the look of a classic
low scenario with the initial waa/most advection surge with the
laying out of a def zone band of rain, potentially heavy, on the
nw side, which could set up across parts of the cwa and
potentially add to the woes of areas already hit by heavier rains
this past Friday. A little early to zero in on exactly where that
band sets up but could see where eventually a surgical type FFA
could come into play focusing on portions of the interior of the
cwa that got hit hard Friday. As the low heads east Tuesday would
expect any lingering rain to gradually wind down. Overall a
cloudy, damp and breezy period is shaping up with some hefty rain
totals looking likely for parts of the cwa.

Tuesday night through Thursday night - Confidence...Medium
Expecting a prolonged quiet period as ridging builds in.
We`ll get back to some warming temps again as the high clears to
the east by about Thursday and a return flow sets up. Pattern is
suggesting any precip with next system will stay to our west or
northwest.

Friday through Saturday - Confidence...Low to Medium
Models are showing a shortwave trough that would move through
Friday afternoon or Friday night. This is faster than the prior
run. An ssw 850 jet is proggd to increase moisture ahead of this
trough and there would be appreciable upper dynamics in play to
support a potential round of shra/tsra Friday or Friday night.
Models may still bounce around on the details of this so for now
will just ride with the blended guidance. Looks like some pretty
warm air is poised to return late in this period and beyond.

AVIATION(09Z TAFS)...IFR ceilings and visibility will be the main
concern this morning, with areas of fog and stratus across the region.
Conditions should improve within a few hours of sunrise.

VFR is expected today, with east to southeast winds. Winds will
start to increase this evening, as low pressure deepens to the
west. Some gustiness will be possible, especially at KMKE, where
winds will be coming right off of Lake Michigan.

MARINE...Quiet conditions are expected through the daytime hours
today. Southeast to east winds will increase later this evening into
tonight, as low pressure develops and approaches from the west.
15 to 20 knot gusts are expected overnight into Monday, with waves
building to 2-3 feet by Monday morning.

North winds then increase early Tuesday as the surface low pulls
east of the area. 20-25 knot gusts are expected for much of the
day Tuesday, with waves increasing to 3-5 feet, especially near
open waters. A Small Craft Advisory will likely be needed for this
timeframe.

BEACHES...Onshore flow will increase later tonight, with 2-3 foot
waves along the Wisconsin shoreline Monday night. Elevated winds and
waves will then continue through the day Tuesday, as winds become
gusty from the north.

Increased winds and waves will result in a risk for rip currents
and strong structural currents.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

Update...Wood
Today/Tonight and Aviation/Marine...Boxell
Monday THROUGH Saturday...Collar


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