Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 181137
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
637 AM CDT Thu May 18 2017

.UPDATE...

Dry wedge should give some sun far southeast this morning
before stratocumulus shield moves in from the west.

&&

.AVIATION(12Z TAFS)...

Dry wedge should give some sun far southeast this morning
before stratocumulus shield moves in from the west. Cigs
will lower to MVFR from the west today. Then expect some decrease
in lower clouds tonight before mid/high clouds move back in late
tonight.


&&

.MARINE...

Brisk southwest winds this morning, as a strong surface low moves
exits across the Lake Huron area. There may be a brief period of
lighter winds/waves, but northeast winds are expected to push down
Lake Michigan this afternoon, with increasing winds and waves.

Will extend the Small Craft Advisory into early Saturday
afternoon due to the persistent northeast winds and higher waves.


.PREV DISCUSSION... (Issued 300 AM CDT Thu May 18 2017)

DISCUSSION...

Today and Tonight...Forecast Confidence is Medium...

Weakening shortwave over the northern Great Lakes will move
northeast as a strong upstream trough moves into Colorado with
weak ridging over the Upper Mississippi Valley. The surface low
exits to the lake Huron area.

Mid levels dry but moisture is trapped below a strengthening
inversion just below 850 mb. This should spread stratocumulus
across much of the forecast area, that will slowly scatter out
later tonight.

Low level cold air advection today, enhanced by developing
northeast winds which will bring Lake Michigan cooling.

A few showers lingering early this morning especially in the
north toward the low. More light showers possible today, from mid
morning into the afternoon, as a cold front drops through the
area.

Friday and Friday night - Confidence...Medium
Mid level ridging early in the day gives way to increasing
southwest mid level flow with trough approaching. The surface high
will be maintaining a northeast flow. The models are showing a
little better precip advancement into the area though the GFS
keeps the rain held back to the western cwa. Some lingering
influence of the dry ne feed probably holding things back at least
a little bit. However seeing the 850 jet ramp up with some better
moisture advection taking place. So will go with the highest pops
spreading into the southwest with lower pops in the northern and
eastern cwa. 850 LLJ translates eastward so plenty of moisture
feeding in on increasing southerly flow. Even though primary mid
level low is still in the Plains seeing evidence of some lead
waves coming through in the southwest flow which will help to
boost pops somewhat. The 00z ECMWF and and GEM are not too bullish
on the precip keeping best qpf to our southwest while the GFS is
the most aggressive bringing the qpf max into the area. Went with
the Superblend pops for now. Seeing several hundred J/KG above
fairly pronounced low level inversion, so will keep thunder
mention in place.

Saturday - Confidence...Medium
Better consensus for rain/tsra with 850 speed max impinging on the
area along with some upper divergence associated speed max on
eastern side of advancing trough. Low pressure proggd to near nrn
IA or srn MN and head northeast from there Saturday night. A mid
level dry slot works in fairly quick Saturday evening which helps
to lower qpf amounts from sw to ne.

Sunday - Confidence...Medium
The low is proggd to lift to near or north of Lake Superior. Cold
advection regime will be in place. Broad mid level cyclonic flow
and some low level troughing could result in some shra potential.
Only the GFS is latching onto any qpf with the ECMWF dry.

Monday through Wednesday - Confidence...Medium
This period will be marked by the evolution of a closed off low
across the Great Lakes or Ohio Valley as energy rides southeast
around the Canadian vortex and forms a new circulation.
Low level cyclogenesis occurs to our south or east which results
in periods of shra with an overall cool regime as wind flow will
be off the lake or northerly esp for Tuesday and Wednesday.

MARINE...Brisk southwest winds this morning, as a strong surface low moves
exits across the Lake Huron area. There may be a brief period of
lighter winds/waves, but northeast winds are expected to push down
Lake Michigan this afternoon, with increasing winds and waves.

Will extend the Small Craft Advisory into early Saturday
afternoon due to the persistent northeast winds and higher waves.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 3 PM CDT Saturday for LMZ643>646.

&&

$$

Update...Hentz
Today/Tonight and Aviation/Marine...Hentz
Friday THROUGH Wednesday...Collar



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