Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 260834
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
334 AM CDT TUE JUL 26 2016

.TODAY...Forecast Confidence Is High.

Broad area of weak high pressure will bring light winds and few
clouds today, as it slowly edges eastward across the region today
and tonight. Forecast soundings indicate some scattered diurnal
cumulus, though GFS low-level RH forecasts and NMM WRF indicating
cloud cover could become broken for a time in the far south. Will
keep a more optimistic sky forecast, as GFS forecast soundings
are more in line with the scattered solution favored by the
majority of the guidance.

Model 925 mb temperatures still a degree or two higher than
Monday, so will raise highs a nudge up from yesterday. However,
lakeshore areas, especially the southeast, will see onshore
winds that will hold highs a few degrees lower than inland.

.TONIGHT...Forecast Confidence Is High.

GFS is alone in bringing precipitation into the northern CWA,
ahead of one of a series of weak shortwaves moving through the
zonal flow across the northern states. However, little moisture in
the column on the GFS forecast soundings until after 12Z
Wednesday. All the models show a stronger convectively-enhanced
vorticity maximum well back to the west over eastern South
Dakota/eastern Nebraska.

Will follow the consensus of the models and WPC guidance that
holds precipitation to the north of the CWA through the overnight,
closer to the better convergence, along a weak surface trough
sagging south into northern Wisconsin. Given the slightly higher
925 mb temperatures, and a bit more stirring with light southwest
surface winds overnight, lows will be 3F to 5F warmer than this
morning.

.WEDNESDAY THROUGH THURSDAY NIGHT...Forecast Confidence Is Medium.

Models are in general agreement with weak cold front sliding
southward through the area later Wednesday into Wednesday evening.
It then slides further to the south later Wednesday night into
Thursday night. Models also in decent agreement with a 500 mb
shortwave trough sliding east southeast through the region
Wednesday afternoon into Thursday morning. NAM/GFS/Canadian
models have a better defined shortwave trough/vorticity maximum
passing through the region than the ECMWF.

Adjusting area forecast soundings for expected dew points show
generally tall and somewhat skinny mean layer CAPE values
Wednesday and Thursday, with similar elevated CAPE Wednesday
night. Deep layer shear remains relatively weak during this
period.

Moisture parameters are not as impressive as previous days, so
heavy rainfall may not be as much of a concern. QPF varies among
the models for Wednesday into Thursday, but does trend downward
Thursday night. For now, will continue the chance POPs for this
period.

Warm and humid conditions will linger on Wednesday, with
temperatures cooling for Wednesday night into Thursday night.
Winds will shift northeast during this period, bringing the
coolest temperatures near Lake Michigan.

.FRIDAY THROUGH MONDAY...Forecast Confidence Is Medium.

ECMWF tries to hang onto QPF Friday, as it has a 500 mb shortwave
trough moving east through the area. The GFS does not have this
feature as well defined as the ECMWF, and keeps the area dry. Kept
low POPs for Friday for now, until better agreement on trends can
be found in these models.

High pressure to the northeast of the region Friday night into
Monday may end up keeping the area dry. 500 mb ridge does shift
east into the region on Monday. Not a lot in the way of features
that would bring upward vertical motion to the area.

For now, will continue with the low POPs for this period, but it
may end up dry if the models continue to trend in this direction.
Temperatures should remain near or just below seasonal normals.
Onshore winds should keep lakeshore areas cooler.

&&

.AVIATION/12Z TAFS/...

Any patchy MVFR/IFR fog will dissipate within an hour or two
after sunrise. Expect VFR conditions with scattered late
morning/afternoon cumulus and light winds today, with surface
high pressure sliding over the region. Mainly VFR conditions
expected tonight, though some patchy fog in river valleys/low-
lying areas possible.

&&

.MARINE...

High pressure drifting across the Great Lakes region will keep
winds light today. A lake breeze is expected late this morning
through the afternoon, and again late Wednesday morning. Winds
will turn northeast and increase, as a back-door cold front will
slide down Lake Michigan Wednesday afternoon and evening.

Northeasterly winds will be stronger, in the wake of a weak cold
front on Thursday, that will lead to higher waves along the
nearshore waters. Winds and aves are still expected to remain
below Small Craft Advisory criteria.

&&

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

$$

TODAY/TONIGHT AND AVIATION/MARINE...REM
WEDNESDAY THROUGH MONDAY...Wood



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