Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 281427
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
927 AM CDT Tue Mar 28 2017

.MARINE...North winds will shift more east around high pressure.
This flow will bend northeast through Wednesday. These winds and
subsequent waves are expected to remain below small craft levels.
However the onshore flow will further strengthen heading into
Wednesday and Wednesday night as low pressure approaches. Higher
waves can then be expected with potential small craft advisory
headline needed.

PC

&&

.PREV DISCUSSION... (Issued 623 AM CDT Tue Mar 28 2017)

UPDATE...

AVIATION(12Z TAFS)...

Clearing will continue slowly from the north today. Mainly IFR
ceilings are currently in the south and MVFR north. The MVFR
should continue to progress southward this morning. Most places
should be VFR by late afternoon into early evening as the clouds
exit to the south.

Seeing a few areas of lower visibilities early this morning,
which should improve by mid-morning as daytime mixing increases.

Model soundings show more low clouds and/or patchy fog could form
again by later tonight ahead of an approaching wave.

PREV DISCUSSION... (Issued 308 AM CDT Tue Mar 28 2017)

SHORT TERM...

TODAY AND TONIGHT...Forecast Confidence...High

High pressure will build in from the north today and tonight,
bringing decreasing clouds from north to south. Should see mostly
clear skies across the forecast area by this evening.

Main issue today will be the timing of the departure of clouds and
resultant impact on temps. Think there should be enough sun later in
the day (especially in the north) to help temps get up toward or a
touch above normal values for late March. It will be cooler near
Lake Michigan though due to onshore winds.

High clouds will likely increase late tonight in at least the west
ahead of an approaching trough. Near normal temps are likely
tonight.

WEDNESDAY...Forecast Confidence...high

Upper level ridging builds into the region ahead of a deep cutoff
low over the southern plains. We will sit in a generally diffluent
region ahead of the low, so good jet level divergance will be
realized throughout the day. Most guidance also shows a weak
shortwave pushing though on Wednesday afternoon just behind the
ridge axis.

Associated surface low will begin its treck northeast on
Wednesday. With high RH, strong WAA, and considerable fgen showing
up at 700mb in all models, it looks like the mid level portion of
the warm front extending from the low will push into southern
Wisconsin on Wednesday afternoon. However, everything below about
700mb is dry in all models through 00z. Therefore am not bullish
on precip chances in the afternoon. That said, both GFS and Euro
do show some light QPF before 00z, and I suppose I can`t
completely rule out precip chances, so will stick with slight
chance PoPs in the afternoon in the southwest.

LONG TERM...

WEDNESDAY NIGHT THROUGH FRIDAY...Forecast Confidence...medium

The amplified upper level trough and surface low pressure system
will track across the upper Mississippi valley. Models in good
agreement showing ample jet level divergence and DCVA aloft
through Thursday as the surface low tracks toward the region. The
mid level warm front extending from the surface low will remain
over southern Wisconsin through Thursday evening as the low
passes to the south of the state. Given the good consensus,
comfortable going with high PoPs on Thursday.

There remains some disagreement after 00z Fri regarding exactly
where the low will pass and just how fast the low will leave the
area. On this evening`s runs, the GFS brings the low through
northern IL and pushes it out of the area the quickest. The
Euro/Canadian bring it though central IL, and the NAM, which
appears to be an outlier, brings it though southern IL and pushes
the system through the region much more slowly. Therefore will
gradually tail off PoPs into Friday morning. Models still showing
a thermal profile supporting a snow or rain-snow mix to start the
day on Thursday before switching to all rain by Thursday
afternoon.

NW flow aloft and high pressure at the surface will build into
the region behind the low on Friday, bringing gradually clearing
skies and seasonally cool temperatures. Blended guidance seems to
be too warm on Friday when compared to the raw model output,
likely due to MOS forecasts trending toward climatology. Since
we`ll be right behind the low pressure system, will go with a
forecast a bit closer to the raw model output.

SATURDAY THROUGH TUESDAY...Forecast Confidence...low

Another shortwave will pass through the region Saturday night, but
the associated surface low will be over southern Canada. Some
light rain may be possible on Sunday, but overall little impact on
southern WI. Then, by the beginning of next week, yet another
deep cutoff low will move northeast out of the southern plains.
Considerable disagreement on exactly where it will move to, but
it does look like a strong low pressure system will be moving
somewhere through the midwest, and this will be enough to support
up to chance pops in our CWA.

AVIATION(06Z TAFS)...

IFR CIGS have developed across most of southern WI now and will
generally stay there until mid to late morning (especially south of
Madison and Milwaukee). Could see mainly MVFR across the northern
forecast area. Ridging will eventually bring clearing from north to
south across the area late this morning and into the early
afternoon. CIGS may fluctuate between IFR and MVFR close to Lake
Michigan until 15z today, before gradually improving with the dry
air intrusion. Look for rather steady north to northeast winds at
10kts or less during the TAF period. Some light fog is expected
through mid morning, but the solid overcast clouds should keep it
from getting too dense.

MARINE...

Gusty winds and some higher waves are likely from late Wednesday
night through Friday as low pressure moves through the region. A
Small Craft Advisory will probably be needed during this period.

&&

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

$$
Today/Tonight and Aviation/Marine...DDV
Wednesday THROUGH Monday...BSH


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