Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 302031
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
330 PM CDT FRI SEP 30 2016

.TONIGHT AND SATURDAY - Forecast Confidence...High.

More of the same this period. Cloud cover, northeast winds, cool
temperatures, showers, drizzle. All in place to due to the
persistence of the cutoff/stacked low that is proggd to waffle
northward towards southern lower Michigan by days end Saturday.
A little wedge of DAVA has worked in which has really cut back on
the precip coverage across srn WI. As the low lifts north the progs
are showing an increase in DCVA throughout the night and is further
enhanced on Saturday as the circulation center arrives closer to the
lower Michigan vicinity. The NAM solution wraps in DAVA from the
north Saturday afternoon while the other models hang onto the sct
shra regime. Although looking at some of the meso solutions into the
afternoon appears we may see a diminishment in much of the west with
POPS confined more to the east.

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

Persistent nearby upper low will become more progressive early in
the period in response to long wave troffing advancing into the
western CONUS.  Upper low will remain in close enuf proximity to
Wisconsin Saturday night before it begins weakening and moves off to
the east.  Portions of eastern WI still likely to see a period of
light rain Saturday night as mid-level deformation and weak
isentropic omega with low condensation pressure deficits brush the
area.  Upper low loses its grip on Wisconsin late Saturday night
into early Sunday leaving behind cool, thermal trof and deep low
level moisture.  Plenty of lingering cloud cover on Sunday should
keep temperatures somewhat in check but lack of rain should allow
daytime temps to rise into the mid 60s which is near normal for
early October.

Enough subsidence may wear away some of the clouds Sunday night. The
lingering high humidity and light winds would then result in areas
of fog.  Too much uncertainty regarding cloud cover at this point to
go more than patchy fog across western CWA closer to incoming ridge
axis.  The quiet, seasonal conditions will continue into Monday as
the short-wave ridging moves through the western Great Lakes.

.EXTENDED PERIOD...

MONDAY NIGHT THROUGH FRIDAY - Forecast Confidence...High trending to
Medium.

Weather pattern initially becomes more progressive through mid-week
as upper low separates from west coast long wave trof and moves
across the Rockies into the northern Plains.  Short wave ridging
ahead of this feature should result in quiet, dry weather across
southern Wisconsin early in the period on through Tuesday night. By
midweek, GFS and GEM guidance in good agreement on tropical
disturbance moving northward through western Atlantic, possibly
grazing east coast. 00Z ECMWF about 24 hours slower with NNW track
of disturbance in western Atlantic.  This system will likely cause
progressive pattern to slow across upper midwest and southern Canada
later in the week.  Never the less, enough progression in upper
pattern to sweep cold front across Wisconsin around Thursday as low
moves from the northern Plains in Canada. South winds ahead of the
front usher a return of deeper moisture as column precipitable water
increases to over an inch.  Hence wl continue chance pops for shra
and isold t beginning Wed, carrying into Thu night.  Significant
cooldown behind passing front with 850H temps from ECMWF dropping
below 0C Thursday night.  Temperatures may drop into the 30s both
Saturday night and Sunday night pending cloud cover.  Will need to
start thinking about frost potential, especially Saturday night
when lightest boundary layer winds would be expected.

&&

.AVIATION/00Z TAFS/...

Stacked/cutoff low vcnty srn IN continues to pivot moisture westward
into srn WI. Embedded spokes of energy result in an uptick in shra
across the area. Low cigs and some lwr vsbys are accompanying this
moisture feed and the moisture from the lake as well. However vsbys
where reduced are mostly of the MVFR variety. Most cigs likely to be
IFR category but a few are LIFR and some are sneaking into the MVFR
category. So some variability out there. This is expected to persist
for much of this forecast period as additional rounds are forcing
result in more shra. Pressure gradient remains supportive of gusty
northeast winds with the highest gusts closer to the lake.

&&

.MARINE...Small craft advisory continues into the night due to the
persistent northeast fetch. Wind speeds are proggd to ease but only
a bit heading into Saturday morning. So a little concerned going
expiration of 09z may be too soon given the ne fetch duration.
Looked at waterspout potential too heading into Saturday. 850 temps
cool a smidge though taking an average of warmer mid lake and cooler
nearshore temps, it seems that better potential (higher delta t and
slightly deeper CCD) would be towards mid lake. Will leave out of
forecast for now.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...

WI...None.
LM...Small Craft Advisory LMZ643>646 until 4 AM CDT Saturday.

$$
TONIGHT AND SATURDAY/AVIATION/MARINE...COLLAR
SATURDAY NIGHT THROUGH FRIDAY...MBK



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