Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 181252
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
752 AM CDT Mon Sep 18 2017

.UPDATE...


&&

.AVIATION(12Z TAFS)...

Will have to watch a band of clouds dropping down from the
northeast this morning. Look for a brief period of lower
ceilings, particularly across the northeast forecast area.

Showers are possible tonight. Ceilings should mainly stay VFR
with these showers.

&&

.PREV DISCUSSION... (Issued 328 AM CDT Mon Sep 18 2017)

SHORT TERM...

Today And Tonight...Forecast Confidence Is Medium.

A weak upper level shortwave over the northern and central Plains
will move across the Upper Mississippi Valley this evening. As it
does, a 95 knot 250 mb jet will lift northeast across northwest
Wisconsin, with southern Wisconsin in the right entrance region.
This increases the upper divergence and weak 700 mb upward motion.

Low levels are very dry, but mid level RH does increase. Only
chance of light showers expected. High clouds will increase this
morning, and should limit any organized areas of fog. However,
still some patchy fog in low areas, especially east.

Tuesday Through Wednesday Night...Forecast Confidence Is Medium.

NAM/Canadian keep the 500 mb shortwave trough and decent low to
mid level moisture passing slowly east northeast through the area
on Tuesday. The GFS/ECMWF generally shifts these off to the east.
Thus, the NAM/Canadian models keep some QPF across the area
Tuesday, with the GFS/ECMWF relatively dry. Continued to mention
mainly lower end PoPs for Tuesday morning, trending mainly dry in
the afternoon. Continued warm temperatures in the middle to upper
70s are forecast inland, with slightly cooler readings near the
lake with onshore winds.

Southwesterly low level jet to the west of the area Tuesday
slides east toward the area Tuesday night, into the area on
Wednesday, stalling over the region into Wednesday night. Warm air
advection occurs over the region as well. The NAM is showing
decent low level frontogenesis response fields over the area later
Tuesday night, with the other models not showing much if any of
this. Kept small PoPs for the NAM scenario, though would not be
surprised if later Tuesday night ends up dry.

Cold front then moves east toward and slows or stalls over the
area Wednesday into Wednesday night, as 500 mb flow remains
southwesterly over the region. There is decent low level
frontogenesis response fields that accompany the front, highest in
the western portions of the area. There is a fair amount of
elevated CAPE that develops over the area during this time, with a
rather strong cap for mean layer parcels. Deep layer and
effective layer bulk shear is not impressive. This elevated CAPE
would have to be tapped by the low level jet in the area.

Continued trending up PoPs Wednesday afternoon into Wednesday
evening, then downward later in the night. This will be the best
shot at some meaningful rainfall over the area this week. Warm and
humid conditions are expected on Wednesday, with middle 80s
inland and somewhat cooler values near the lake with onshore
winds.

LONG TERM...

Thursday Through Sunday...Forecast Confidence Is Medium.

Models continue to show an amplified 500 mb ridge and anticyclone
over the central and eastern Great Lakes region during this
period. This maintains southwesterly flow over the region during
this time. The main track for low pressure systems will remain to
the west and northwest of the region.

The remnants of the cold front on Thursday may keep a few showers
or storms in the area. Otherwise, models are showing southerly
flow in the low levels lingering through the weekend, with the
area firmly in the warm sector airmass. This should result in warm
temperatures continuing, with somewhat humid conditions.

AVIATION(09Z TAFS)...

VFR conditions are expected most places through Monday. Localized
IFR ground fog mainly in east areas early this morning. Will have
to watch an area of clouds dropping down from the north later
tonight into Monday morning. Could see a brief period of lower
ceilings, particularly across the northeast forecast area.

Showers are possible later Monday into Monday night. Ceilings
should mainly stay VFR with these showers.

MARINE...

Winds will become northeast and gusty for a time this morning.
This will cause waves to build to near 3 feet north of the
Milwaukee area. Right now, it looks like conditions should stay
just below Small Craft Advisory criteria. Lighter winds and lower
waves are then expected into Tuesday.

&&

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

$$

Update...Hentz
Today/Tonight and Aviation/Marine...Hentz
Tuesday THROUGH Sunday...Wood



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