Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 241510 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1010 AM CDT Fri Mar 24 2017

.UPDATE...

Upper 40s for highs in the northern forecast area (Marquette to
Sheboygan) are on track- that is the current temp and it`s safe
to say the warm front will stay to the south of that area.
Southerly winds are increasing across far southern WI now as the
warm front heads north, so highs around 70 seem on track there.
The max temps along the I-94 corridor are the least certain for
today. An easterly component to the winds near Lake Michigan north
of Racine will keep temps near the lake a little cooler.

&&

.MARINE...

Small craft advisory still looks good for the start time late this
afternoon north of Port Washington and this evening for points
south. This is due to increasing northeast winds and building
waves as low pressure tracks to the south of Wisconsin through
Saturday.

&&

.PREV DISCUSSION... (Issued 544 AM CDT Fri Mar 24 2017)

UPDATE...
Look at winds across the area, the surface front likely runs from
near Lone Rock to Juneau to Port Washington. It should hover in
this general location through about mid afternoon, then start to
sag south with increasing northeast winds to the north of the
front. Temps will warm quickly after about 9 am this morning.

AVIATION(12Z TAFS)...

The focus for precipitation will likely remain well north of
Milwaukee and Madison through late afternoon, possibly into the
evening hours, based on some of the new guidance rolling in. A
frontal boundary is stalled along a line stretching from near Lone
Rock to Juneau to Port Washington. Very warm temps and southerly
winds are expect south of the front, much cooler northeast winds
can be expected to the north. The front will sag south this
afternoon, pushing south of the state line by 6 pm this evening.

CIGS will gradually lower to MVFR then IFR late this afternoon
into the evening as the cold air mass overspreads the region and
more widespread precipitation moves in. KMSN/KMKE should be MVFR
by 22-23z this afternoon.

PREV DISCUSSION... (Issued 255 AM CDT Fri Mar 24 2017)

TODAY...Forecast confidence is medium.

Clearly the biggest challenge for today will be on temps.  A
classic, very sharp springtime temp contrast will exist across
southern Wisconsin as a frontal boundary stalls right along a
Milwaukee to Madison to Spring Green line at mid day.  To the north,
temps in the upper 40s.  To the south, lower 70s.  Nailing that
front`s exact location is tough, but has big consequences depending
on what side of that front you are on. Convection currently rolling
by to the north will likely help lay out a cooler, reinforcing
outflow boundary.  Ridging sliding by to the north of the Great
Lakes today will help to increase the cold northeast winds over all
but southern Wisconsin.  The battle will be between the southerly
winds ahead of approaching low pressure and those northeast winds
strengthening across Wisconsin. Throw in an earlier northeast wind
along Lake Michigan and you have that micro climate complexity.  The
previous temp forecast is mostly intact, but it is highly dependent
on just where the front finally sets up for early afternoon.  Most
rain chances today will be limited to well north of Milwaukee and
Madison. Precip across Wisconsin for much of today will be up closer
to the h8 frontal boundary located across northern Wisconsin.  That
front will begin to sag south, increasing the chances of rain over
southern Wisconsin as we approach evening.

TONIGHT...Forecast confidence is high.

The cold northeast winds will eventually push that frontal boundary,
and those warmer temps south of the border by early evening.  The
big, closed and stacked low pressure system will continue to
approach Wisconsin tonight, reaching Missouri by Saturday morning.
The h8 boundary sags into southern Wisconsin and will bring with it
the deeper frontogenetic forcing.  Thus, we should see periods of
showers through the night, a thunderstorm is also possible, but they
will be rather isolated.  Nothing severe expected. And, with a
reminder that it`s still March, lows by morning will be in the 30s.

SATURDAY AND SUNDAY - Confidence...Medium
Large 500 millibar low across the central Plains will lift northeast
into lower Michigan by Sunday. This will keep our cwa on the
northern periphery of the steadier rains. Models suggest that the
heavier rains arrive later Saturday morning through the afternoon.
With the low tracking across northern Illinois a steady wind off the
lake and cloud cover will keep things quite chilly so trended below
Superblend guidance on temps, especially closer to the cooler
influence of Lake Michigan. Due to the proximity of the low on
Sunday, the rain is likely to persist though some consensus that
amounts not as heavy as Saturday but still looks like a pretty high
pop scenario. With surface low getting close the winds could go
rather light for a time Sunday which may set up a fog scenario
especially closer to Lake Michigan with potential for a light and
very moist onshore flow. MOS guide from both the NAM and GFS showing
this possibility.

MONDAY - Confidence...Medium
Models are showing another mid level trough axis approaching with a
pocket of vorticity to our south and one to our north with some
suggested phasing trying to take place. The latest GFS shows a more
rain arriving with the southern energy passing to our south. The 12z
Euro keeps the higher amounts to our south. Will bring in the
highest POPS into our southern CWA during the afternoon and evening
as this mid level wave and surface reflection pass through.

TUESDAY AND WEDNESDAY - Confidence...Medium
Mid level flow trends more anticyclonic in the wake of the trough.
Surface ridging also is proggd to suppress precip this period. The
surface high shifts to the east on Wednesday but it appears that a
lingering dry influence will keep any advancing precip at bay with
next system drawing a bit closer.

WEDNESDAY NIGHT AND THURSDAY - Confidence...Medium
Large upper low in the southern Plains is proggd to start lifting
out towards the mid Miss Vly this period. The ECMWF are on the same
page with this idea but the GEM keeps it well south our area being
dominated by more in the way of mid level ridging in the northern
stream. Will follow the Superblend guidance which latches more onto
the consensus of the ECMWF and GFS solution with increasing POPS
into Thursday. The latest ECMWF is much more aggressive on rain
expanding into the area with more qpf than the GFS. This will all
hinge on the speed of ejection of the system and how much the
lingering dry southeast feed will erode any advancing precip. So the
slower and less aggressive GFS may be the best compromise approach
to this scenario for now.

AVIATION(06Z TAFS)...There will be a general lull in the precipitation
overnight into most of Friday. Ceilings should rise well into VFR
category, with visibilities above 6 miles during this period. Could
even see some clearing in the far southern counties at times as
well.

Gusty south to southeast winds should gradually weaken and become
southwest into Friday morning. Northeast winds should then develop
and become gusty Friday night into Saturday night, as low pressure
passes by to the south.

Rain showers will gradually move into the area late Friday afternoon
and over all of the area Friday night, lingering at times into the
weekend. Look for low ceilings and reducing visibilities Friday night
with the rain showers. Some fog may develop at times over the weekend.

MARINE...Northeast winds will increase from north to south across Lake
Michigan today into tonight.  A small craft advisory will be needed
around Sheboygan by late afternoon and the rest of the nearshore
waters down to the WI/IL state line by this evening.  Waves will
gradually build and remain elevated through Saturday night.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory from 7 PM this evening to 3 AM CDT Sunday
     for LMZ644>646.

     Small Craft Advisory from 4 PM this afternoon to 3 AM CDT Sunday
     for LMZ643.

&&

$$

Update...Cronce
Today/Tonight and Aviation/Marine...Davis
Saturday THROUGH Thursday...Collar


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