Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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757
FXUS63 KMKX 240241
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
941 PM CDT FRI SEP 23 2016

.UPDATE...

.AVIATION/06Z TAFS/...Ceilings will mainly range from 1-3 kft
for overnight and through Sat am. Areas of drizzle or very light
showers will be possible over south central WI Sat am and may
limit vsbys to mvfr. Most cigs will rise to 3.5 kft by the middle
afternoon hours. Patchy fog may also occur south and west of KMSN
for the early morning hours of Sat.


&&

.MARINE...East to northeast winds of 10-15 kts will maintain wave
heights of 2-4 feet for early Sat am with slightly lesser wave
heights expected for Sat afternoon and evening. The waves will
increase once again for late Sat night and Sun as sely winds
increase to 10-20 kts. Waves may build to 3-5 feet north of Port
Washington while remaining 2-4 feet to the south. Thus a Small
Craft Advisory may be needed on Sun north of Port Washington.


&&

.PREV DISCUSSION... /Issued 328 PM CDT FRI SEP 23 2016/

TONIGHT AND SATURDAY...Forecast Confidence...Medium

850 baroclinic zone will linger across the area through the night. A
weak low level jet and weak warm air advection may provide enough
forcing for a few showers through early Saturday morning. Low level
moisture will remain along this boundary through Saturday keeping
the CWA under a blanket of low stratus.

Even with a light east wind of 5+ knots, think there will be patchy
fog, especially in SW WI with ample low level moisture.

The 850 boundary will shift east on Saturday as mid level ridging
moves into the region. High pressure over Ontario will shift east
bringing drier air from the east to southern WI. It will not be
enough to erode cloud cover but some some areas in the far east may
see a few breaks in the clouds during the afternoon.

SATURDAY NIGHT...Forecast Confidence High.

Warm advection kicks in as southeast winds veer south ahead of
deepening trough over the northern Plains. Will bring chance PoPs
into the western CWA after 06Z with omega due to frontogenetic
response to the warm advection and channel of 850 mb moisture
transport shifts into western Wisconsin. The increasing clouds and
some mixing from 25 knot winds around 1k feet at the top of the
shallow nocturnal inversion will keep lows in the lower 60s, with
some upper 50s in the far north and northeast.

SUNDAY AND SUNDAY NIGHT...Forecast Confidence High

Showers and thunderstorms likely in the west Sunday morning,
spreading over all of southern Wisconsin during the afternoon and
lingering in the east in the evening as deepening trough and surface
front cross the region. Modest lapse rates produce tall skinny CAPE
values between 500 and 1000 Joules/kg with minimal shear.
Precipitable water values in the 1.5 to 1.8 inch range so some heavy
downpours possible. Location of potential heavy rain will have to
monitored in later runs to see if it will affect areas that are
flooded from heavy rains earlier in the week. The showers and storms
will slowly diminish from west to east Sunday night as dry mid-level
air spreads across southern Wisconsin.

MONDAY...Forecast Confidence Medium.

Timing showers out of eastern Wisconsin Monday relies on whether
slower GFS, which closes off the upper low sooner than the other
models, or faster 12Z NAM and ECMWF solutions occur. However these
faster models still drop a significant short wave through the base
of the trough Monday morning. Will limit slight chance PoPs to the
far east in the morning and far north in the afternoon closer to the
700 mb omega and mid-level moisture rotating around the 500 mb low.

LONG TERM...MONDAY NIGHT THROUGH FRIDAY...Forecast Confidence
Medium.

Will hold on to slight chances for showers Monday night and during
the day Tuesday as area still under the western flank of mid-upper
level cyclonic flow. Upper ridging and surface high build in
Wednesday as upper jet shifts north of the Canadian border and keeps
area dry.

Weak subtropical jet does lift a short wave trough into the Plains
Thursday night and Friday, but broad high covering the eastern U.S.
holds better return moisture flow well west across the Plains
through Friday night into Saturday morning. Below normal
temperatures Tuesday rise back to normal levels Wednesday, and then
above normal for Thursday and Friday.

AVIATION/00Z TAFS/...

East winds are expected through Saturday. There is a small chance
for showers through Saturday morning.

An axis of low level moisture will remain across southern WI through
Saturday morning. The southwest part of the state is likely to see
IFR ceilings and fog late tonight through Saturday morning. MVFR
ceilings and patchy fog are likely across the rest of southern WI,
except for the far east.

Northeast flow off Lake Michigan is bringing drier air to parts of
far eastern WI which makes a challenging forecast. With little
change to the overall pattern, expect ceilings to continue to bounce
around through the afternoon and evening at KUES, KMKE, and KENW.
MVFR ceilings are likely to redevelop tonight as daytime mixing
subsides.

MARINE...

Northeast winds will become east tonight. Winds and waves will
approach Small Craft Advisory levels but are expected to remain
below. A cold front will move through the region Sunday, shifting
winds to the south and then west by Monday.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...None.
&&

$$

UPDATE...Gehring
TONIGHT/Saturday AND AVIATION/MARINE...Marquardt
Saturday NIGHT THROUGH Friday...REM



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