Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 141706
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1206 PM CDT Mon Aug 14 2017

.AVIATION(18Z TAFS)...Mid/high clouds from morning convection will
exit eastern CWA next several hours. Seeing an increase in low to
mid clouds upstream across northeast IA into western WI via latest
visible imagery. Weak low level convergence and increasing low
level moisture contributing to increasing low clouds. As cumulus
develop into southern WI, some cigs may be MVFR briefly but should
be mostly lower VFR. Still expect isolated to scattered showers
and a few storms to develop this afternoon into this evening as
short wave trof swings through, but instabilty looks fairly low.

&&

.PREV DISCUSSION... (Issued 940 AM CDT Mon Aug 14 2017)

UPDATE...Scattered showers from weakening MCS will continue to
affect parts of western CWA next several hours. Expect clouds to
thin later this morning and afternoon. Main short wave trof
currently located upstream over eastern MN into western WI will
continue to track eastward next 12-18 hours. It should continue to
generate some showers and a few storms. RAP forecast soundings
not showing much instability this afternoon and evening as wave
moves through. Will continue chance wording into tonight.

MARINE...Light and variable winds will turn to the southeast this
morning ahead of approaching weak surface trof. Winds will turn to
the north to northeast later tonight into Tuesday as the trof
moves through. Winds are expected to remain less than 20 knots
through Tuesday. Strongest winds likely to be Wednesday into
Thursday as low pressure passes through the western Great Lakes.

PREV DISCUSSION... (Issued 632 AM CDT Mon Aug 14 2017)

UPDATE...

Expect the dying MCS to make it into west areas this morning with
just a few showers. Shower/thunderstorm chances increase again
this afternoon and evening.

AVIATION(12Z TAFS)...

Expect the dying MCS to make it into west areas this morning with
just a few showers. Shower/thunderstorm chances increase again
this afternoon and evening.

VFR Mid/high clouds will increase along with scattered cumulus.

IFR/LIFR fog and low stratus clouds may develop late tonight.

PREV DISCUSSION... (Issued 236 AM CDT Mon Aug 14 2017)

SHORT TERM...

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

A broad upper trough moves across the Upper Great Lakes with two
weak shortwaves. One moves through this morning, with a second
slightly stronger one this evening. Weak upper divergence with
weak to moderate 700 mb upward motion mainly with the second
shortwave. 700 mb wind max of 30-35 knots moves across later this
afternoon and tonight. 850 mb wind max is similar but weaker.

Forecast soundings still have dry air between 700 and 850 mb this
morning, with more moisture from the west late morning and
afternoon, bringing zero to 1 km mixed layer CAPE to near 700
Joules/KG. Surface to 3 km shear increases to 25 knots.

Expect the dying MCS to make it into west areas this morning, with
shower/thunderstorm chances increasing again afternoon and
evening.

LONG TERM...

Tuesday through Thursday...Forecast confidence is medium to high:

Models have slowed a bit with the arrival of deeper moisture on
Tuesday, with high pressure over the northern Great Lakes blocking
the way. Went with a dry forecast as a result for Tuesday.

The high will slide eastward Tuesday night into Wednesday,
allowing the deep moisture to get pulled up into the area ahead of
approaching low pressure. Showers and storms will be possible by
later Tuesday night becoming likely Wednesday into Wednesday
night. GFS and NAM precipitable water values are up around 2
inches, so could see some heavy rain.

Low pressure and the associated surface front are expected to be
exiting the area early Thursday morning. Could see a few
showers/storms linger on Thursday until the drier airmass arrives,
but it should be mainly dry by the afternoon.

Temperatures will be within a couple degrees of normal Tue-Thu.

Friday through Sunday...Forecast confidence is low to medium:

There is less certainty among models for Friday into the weekend.
It does look like a shortwave or two will move through during this
period, bringing shower/storm chances. Not great agreement as two
the strength/timing/placement of potential system(s), so kept
precip chances on the low end for now.

Models do agree that temperatures should remain near normal into
the weekend.

AVIATION(06Z TAFS)...

Expect light winds with mainly broken middle to high clouds
lingering over the area overnight into Monday. There may be some
breaks at times, especially on Monday toward the southeastern
portions of the area.

Scattered diurnal cumulus clouds are anticipated by Monday
afternoon. A lake breeze with southeast winds will develop by
afternoon as well near Lake Michigan.

Chances for showers and thunderstorms will increase across south
central Wisconsin Monday, with the best chances toward the
Wisconsin Dells area. These chances should push across the rest of
the area Monday night. Fog and low stratus clouds may develop
Monday night, with visibilities and ceilings down to alternate
minimums possible later in the night.

MARINE...

Light winds are expected across the nearshore waters of Lake
Michigan. A southeast flow is expected today ahead of a weak
trough. Wave heights will be low during this time. Winds and
waves should remain low into Tuesday.

Northeast winds may increase for a time Tuesday, behind the
trough.

Chances for showers and thunderstorms exist this afternoon
and tonight as well. A better chance will be on Wednesday into
Wednesday night.

&&

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

$$

Update...MBK


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