Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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811
FXUS63 KMKX 240755
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
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.

&&

$$
Today/Tonight and Aviation/Marine...Davis
Saturday through Thursday...Collar



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