Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 260234
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
834 PM CST Fri Nov 25 2016

.UPDATE...

I`m having to call an audible on the overnight forecast. Classic
subsidence in the wake of a departing mid level short wave has
ripped a large hole in the overcast across eastern Wisconsin this
evening. This will likely lead to some lower temps and
potentially some fog as dewpoints remain a bit elevated. However,
we also have some low level warm advection that will be spreading
in from the west overnight and this could bring a return of the
lower clouds for a time later tonight into Saturday morning.
Confidence is very low on cloud trends overnight given the latest
developments. We should eventually see all the lower clouds push
off to the east Saturday morning with high clouds moving back in.

&&

.AVIATION/06Z TAFS/...

There is a large amount of unexpected clearing across parts of
south central and southeast Wisconsin in the wake of a mid level
short wave pushing off to the east. KMKE/KUES/KENW and to a lessor
extent KMSN could see a period of clearing skies before more
clouds spread in later tonight into Saturday morning. This
clearing could also lead to the development of fog and IFR
conditions. Confidence is rather low on conditions overnight
given the latest trends. We could see quite the spectrum of flight
conditions, from VFR to IFR across short distances. We should see
improving conditions across all of southern Wisconsin by about
15-16z Saturday with VFR conditions expected thereafter.

&&

.MARINE...

Quiet marine conditions are likely until Sunday night when south to
southeast winds will increase ahead of an approaching low. The low
is expected to not move much Monday and Tuesday, keeping the breezy
winds going. It currently looks like a Small Craft Advisory will be
needed from Sunday night into Tuesday.

&&

.PREV DISCUSSION... /Issued 235 PM CST FRI NOV 25 2016/

TONIGHT AND SATURDAY - Forecast Confidence...Medium.

Light rain/drizzle occasionally mixed with snow in the north will
wind down late this afternoon as a shortwave exits the area. High
pressure will then build in over night behind the departing system.
The primary issue this evening into Saturday will be cloud cover.
The clearing line over western MN and IA has not made much progress
today. Also, several models show additional stratus development this
evening into the night. It`s worth noting that a couple models such
as the GFS are much quicker to clear things out. Overall though,
trended toward a cloudier solution overnight into early Saturday.
Decided to keep temps toward the milder model solutions for tonight
given the expected cloud cover.

Clouds should eventually decrease some tomorrow from southwest to
northeast as warmer air aloft advects in. Temps are expected to be
milder tomorrow as well, with highs a few degrees above normal for
late November.

SATURDAY NIGHT THROUGH MONDAY - Forecast
Confidence...Medium to High.

Short term guidance in good agreement on strong piece of short-wave
energy being ejected into the plains from upstream long wave trof
over western CONUS.  Strong south winds ahead of this system will
rapidly transport deep moisture northward Sunday and Sunday night.
Column precipitable water rapidly doubles to around 1 inch Sunday
night as 50 knot low level jet pivots northeast into WI and weakens.
Will continue categorical pops as expect widespread showers to
affect the area Sunday night.  Despite atmospheric vigor to the
system, not seeing enough elevated instability to warrant adding in
thunder at this point.

Deep moisture remains in place on Monday as showers wan and push to
the northeast.  Low level jet is expected to reinvigorate across
northern IL as a second piece of short wave energy rotates around
occluding low pressure over the northern Plains later.  Therefore
expecting a second period of showers to affect southern WI Monday
night.  Held off on introducing thunder but this would probably be
the better chance with the warm, moist air already in place and
strong low level convergence passing through parts of the area.

EXTENDED PERIOD...

MONDAY NIGHT THROUGH FRIDAY - Forecast Confidence...Medium.

Amplifying short wave transitions to nearly stationary long wave low
pressure trof across central CONUS early in the period.  Low
pressure becomes cut-off early in the period and meanders ENE across
the Great Lakes through the end of the week.  Colder air with the
trof will ooze across southern WI from Tuesday through Thursday,
eventually dropping daily average temps below seasonal normal.

Deep moisture to remain in place Monday night when sfc occlusion and
stronger mid-level short wave rotates around low and across srn WI.
Hence expect second period of showers and will have high pops return
for the overnight period, tapering off Tuesday morning. GEM had been
only medium range guidance showing new cyclogenesis developing along
baroclinic zone laying over southern MS Valley region and moving NNE
toward central Great Lakes.  However 12z ECMWF now trending west and
showing a similar scenario to GEM-NH.  This solution would be close
to bringing a light rain/snow mix to SE WI Wed night. Meanwhile, GFS
has sprawling cutoff upper low across western Great Lakes which
diverts any southeast cyclogenesis much farther east across eastern
CONUS.

Appears cold air intrusion will be here to stay as steering flow to
remain west or northwest through next weekend and the first full
week of December.

AVIATION/00Z TAFS/...

A little drizzle or flurries will linger into late afternoon until a
shortwave clears the area. The main concern then turns to how long
the lower clouds will stick around. Based on the slow progress of
the clearing across western IA and MN and the bulk of 12Z guidance,
have decided to keep it mostly cloudy tonight into Saturday. Should
eventually see clouds decrease and VFR conditions return from the
southwest by Sat afternoon.

MARINE...

Quiet marine conditions are likely until Sunday night when south to
southeast winds will increase ahead of an approaching low. The low
is expected to not move much Monday and Tuesday, keeping the breezy
winds going. It currently looks like a Small Craft Advisory will be
needed from Sunday night into Tuesday.

MKX WATCHES/WARNINGS/ADVISORIES...

WI...None.
LM...None.

$$
TONIGHT AND SATURDAY/AVIATION/MARINE...DDV

&&

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

$$

UPDATE...Davis
TONIGHT/Saturday AND AVIATION/MARINE...DDV
Saturday NIGHT THROUGH Friday...MBK



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