Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 261801 AAB
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
101 PM CDT Wed Apr 26 2017

.UPDATE...


&&

.AVIATION(18Z TAFS)...

First batch of showers have moved north of the forecast area.
There will be a lull in the shower activity this afternoon, though
some drizzle may occur. Low stratus clouds should continue to move
northeastward into the area this afternoon, remaining between 700
and 900 feet above ground level. Southwest winds will become west
toward evening, with some gusts to around 20 knots in eastern
portions of the area.

The low stratus will linger tonight into Thursday morning, before
rising to around 2000 to 2500 feet above ground level Thursday
afternoon. Winds will become northwest tonight, then back to the
west on Thursday. Gusts of 20 to 25 knots are forecast for
Thursday afternoon, especially in eastern portions of the area.

Rain showers should move northeast into the area again during the
middle and late evening, lingering into Thursday morning. The
showers should move northeast out of the area during the late
morning.

Wood

&&

.PREV DISCUSSION... (Issued 1142 AM CDT Wed Apr 26 2017)

UPDATE...

First area of showers is moving north northeast out of the
forecast area late this morning, associated with differential
cyclonic vorticity advection with passing 500 mb shortwave trough.

There should be a lull in the precipitation until toward evening
and mainly tonight, as the next 500 mb shortwave trough slides
northeast toward the area. Differential cyclonic vorticity
advection with this feature is expected tonight, along with some
middle level frontogenesis response. This should result in another
area of rain showers moving north northeast through the area,
especially in the eastern counties, with small chances for thunder
per forecast soundings.

However, there is some uncertainty here with regards to trends
for tonight. The rainfall amounts may need to be reduced somewhat,
as some mesoscale models are showing the best precipitation
amounts staying near the surface based convection to the
southeast. Thus, rainfall amounts and subsequent impacts on some
area river stages may be reduced.

Wood

MARINE...

A Small Craft Advisory is in effect until 11 PM tonight, due to
breezy sly winds and high waves. Low pressure will then track
north along Lake MI, with wly winds in its wake. Thus another
Small Craft Advisory may be needed on Thu for brisk wly winds.

PREV DISCUSSION... (Issued 648 AM CDT Wed Apr 26 2017)

UPDATE...

AVIATION(12Z TAFS)...An area of showers and tstorms over nrn IL
will move newd across srn WI this AM. Cigs and Vsbys may fall to
MVFR at times. The next area of widespread rain will start by
early evening. Cigs will fall to 1-3 kft but then fall below
1 kft by late evening. Vsbys will fall to MVFR but possibly to
2sm over far ern WI.

PREV DISCUSSION... (Issued 351 AM CDT Wed Apr 26 2017)

Today and Tonight...Forecast Confidence is medium.

Areas of showers will move across srn WI this morning with the
passage of a shortwave trough. The cold front will then slowly
begin to move from w-e across srn WI thus more areas of showers
and possibly a tstorm will occur. Another mild and humid day is
expected.

For tnt, the strong upper trough currently over the srn Rockies
will track to TX then swing newd to IL by 12z Wed. This will
induce cyclogenesis from s-n along the front. The low will track
from srn IL to nrn Lake MI. Well organized low to mid level
frontogenesis and Q-vector convergence will bring widespread
moderate to briefly heavy rainfall rates tonight. Total forecasted
amounts range from one half inch west of Madison to near 1.5
inches in se WI. Rivers will rise again with several rivers likely
reaching bankfull stage and perhaps a few reaching minor flood
stage.

THURSDAY - Confidence...Medium
Primary 500 millibar low vcnty nrn MN will lift north. A
negatively tilted shortwave will move northeast across WI. The
upstream surface low will be lifting northeast from ne WI. Def
zone precip shield lingers for the morning hours with 850 cold
advection wrapping in on nw winds. Some of the 850 temps in the
west drop below zero celsius so some concern for a mix in these
areas especially from the NAM, however other models suggest the
precip may out race the colder profile supportive of a mix. For
now leaned more towards the GFS low level profile and consmos
temps which keep things in liquid form. Precip becomes more
scattered during the afternoon.

FRIDAY - Confidence...Low to Medium
Pattern looks to stay active on the GEM/GFS/NAM front while the
ECMWF keeps the precip to our south. All the models including the
ECMWF show shortwave energy shifting northward into srn WI with
time. However the ECMWF is showing much less of an isentropic
component to the forcing than the wetter solutions. Will steer
towards the blended approach and gradually lift pops north as the
day wears on going the with the consensus of a wetter look.

SATURDAY - Confidence...Medium
A high pressure ridge is proggd to be sprawled across the upper
Midwest with a cool easterly flow. The GFS keeps the next surge of
rain to our south while the GEM and ECMWF bring some light rain
northward especially during the afternoon. So again , we have a
northward push of the POPS into at least the southern CWA as the
day wears on.

SATURDAY NIGHT THROUGH MONDAY - Confidence...Medium to High
Little if any model disparity with next 500 millibar low moving
from the southern Plains up through the western Great Lakes this
period. This will keep things quite wet and unsettled. A southerly
850 jet takes hold Saturday night then better upper dynamics
later Sunday into Sunday night, so likely to see two distinct
precip maxes within the overall wet period. Some elevated CAPE
noted at times so some thunder potential. System occludes as low
shifts across WI. Better convective potential appears to be
setting up in the warm sector ahead of the cold front to our
southeast Sunday into Sunday evening. Bulk of heavier precip wraps
up later Sunday night with cold advection wrapping in from the
southwest. A chilly Monday in the works with brisk west/northwest
winds and lingering cyclonic flow with low level thermal trough
well entrenched.

TUESDAY - Confidence...Low to Medium
The ECMWF lingers the low level cyclonic flow with lingering shra
chances while the GFS builds in 850 ridging and a dry look. Will
go the blended approach on pops/temps.

AVIATION(06Z TAFS)...Look for VFR conditions through the night.
Moisture streaming north ahead of an approaching trough of low
pressure will bring increasing chances of showers. CIGS will
gradually lower to MVFR levels Wednesday with showers and a few
thunderstorms, especially southeast. IFR cigs expected behind a
cold front Wednesday night.

MARINE...A Small Craft Advisory is in effect until 11 PM tonight
due to breezy sly winds and high waves. Low pressure will then
track north along Lake MI with wly winds in its wake. Thus another
Small Craft Advisory may be needed on Thu for brisk wly winds.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 11 PM CDT this evening for LMZ643>646.

&&

$$

Update...Wood
Today/Tonight and Aviation/Marine...Gehring
Thursday THROUGH Tuesday...Collar


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