Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 210228
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
928 PM CDT FRI MAY 20 2016

.UPDATE...High clouds to persist much of the night across parts of
southeast CWA as deformation due to mid-level low pressure over
Illinois moves slowly east-southeast. Clouds should thin across
cwa from west to east as circulation moves slowly off to the east.
Bumped up overnight temperatures slightly due to lingering clouds,
especially in the east.

&&

.AVIATION/06Z TAFS/...VFR conditions will persist through the forecast
period under high pressure. High clouds will gradually clear from
NW to SE overnight. A period of 6000 ft cigs could develop during
the day Saturday as a weak shortwave sweeps through the area,
especially for MSN and UES.

&&

.MARINE...Mostly light and variable winds to continue through the
weekend into Monday as nearly stationary high pressure area
remains nearby. Expect winds to turn onshore during the late
morning and afternoon.

&&

.PREV DISCUSSION... /Issued 257 PM CDT FRI MAY 20 2016/

SHORT TERM...

TONIGHT AND SATURDAY...Forecast confidence is high.

A weak upper level shortwave trough crossing the Midwest brought
extensive high clouds to southern WI today. The clouds will
gradually move out from NW to SE overnight. With the dry air and
surface high pressure overhead, expect temperatures to drop into the
40s. Increasing 925mb temps and the high clouds will keep min temps
a little warmer than previous nights.

A weaker shortwave will drop down from the ND/MN border overnight
into Saturday morning. The GFS is producing light precip, but this
is an outlier and is responding to weak instability and steep low
level lapse rates. Given dry air in place and upstream conditions
today, I am confident on the dry forecast and that we will just have
more widespread diurnal cumulus clouds. Max temps will be warmer
than today, with highs in the mid to upper 70s inland from the lake.

Saturday Night and Sunday...Forecast Confidence...High

The large upper ridge over the plains moves into the Upper
mississippi valley toward evening Sunday. Little in the way of
upper divergence of 700 mb upward motion.

700 mb rh remains low with the ridge across Wisconsin. there is an
increase in 850 mb rh sunday under the ridge. This increases the
cape a little, but zero to 1 km mixed layer cape is only around 25
joules/kg and there is a developing cap just under 700 mb.

The surface flow becomes more southerly on Sunday as the center of
the high moves across the Great lakes. However, there will still
be a lake breeze off Lake Michigan during the afternoon.

Sunday Night and Monday...Forecast Confidence...High

The upper ridge moves across Wisconsin with the southwest flow
developing over the Mississippi Valley region late monday
afternoon. The 700 mb upward motion begins over South Central
Wisconsin Monday afternoon with only a modest increase in 700 mb
rh. The forecast soundings are very dry in the mid levels with
little increase in low level moisture, and a rather strong cap
above the mixed layer which reaches up to 850 mb.

The south 925/850 flow to lead to further warming across southern
Wisconsin.

Both the GFS and 00z ecmwf keep any precipitation off to the west.

LONG TERM...

monday night and tuesday...Forecast Confidence...High

The mid/upper level flow becomes southwest with a subtle weak
shortwave pushing into Southern Wisconsin. The 12z GFS is slow to
push showers across the area, keeping them mainly over south
central Wisconsin. The 00Z ecmwf does bring precipitation across,
but it is light.  Both models keep the cold front to the west.
the severe parameter CWASP increases to 65 to around 70 Tuesday.

TUESDAY night AND WEDNESDAY...Forecast Confidence...Medium

The southwest mid/upper level flow continues, with a shortwave
moving across Wisconsin Wednesday.

The GFS is trending a little more toward the ECMWF in moving a
surface low towards Iowa. The Ecmwf is stronger and faster with
the low. The GFS brings showers and thunderstorms with the
weakening cold front Tuesday night, while the ECMWF keeps the
front to the west but has thunderstorms more Wednesday.

the severe parameter CWASP increases to around 75 wednesday on
the ECMWF, but is farther southwest on the GFS with the higher
values.

THursday and Friday...Forecast Confidence...Medium

A somewhat stronger shortwave moves into the central plains on the
ECMWF. The GFS is a little weaker and more north with a closed low
lagging behind over the Southwest U.S Friday.

The ECMWF dries things out Thursday, while the GFS still has
showers and thunderstorms Thursday into Friday. The ECMWF
eventually brings showers and thunderstorms back later Friday
ahead of a strong low near South Dakota.

AVIATION/00Z TAFS/...

VFR conditions will persist through the forecast period under high
pressure. High clouds will gradually clear from NW to SE overnight.
Expect a period of BKN VFR cumulus clouds inland Saturday with the
passage of a weak shortwave.

MARINE...

High pressure will keep winds light and wave heights low through the
weekend, with southerly winds and waves increasing Monday ahead of
an approaching trough of low pressure.

&&

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

$$

UPDATE...MBK/JTS
Tonight/Saturday And Aviation/Marine...MRC
Saturday Night Through Friday...SJH


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