Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 261015
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
415 AM CST Sat Nov 26 2022

.SHORT TERM...
(Issued 415 AM CST Sat Nov 26 2022)

Today through Sunday night:

A low pressure trough approaching from the Northern Plains this
morning will cause southwest to west winds to become gusty. The
mostly clear skies will continue into early this afternoon before
the cloud cover begins to increase ahead of an approaching low
pressure system. Despite the increasing cloud cover warm
temperatures and dry conditions will continue through tonight.
Temperatures have really over preformed the previous few days so
adjusted temperatures up to around the 90th percentile for
guidance for today. This does track really well with the 950mb
temperatures which are expected to be around 6-8 degrees C. What
this means for surface temperatures is highs in the mid 50s with a
few locations even approaching 60. For those of you who are
wondering where the record high temperatures sit for today, MSN
has a record high of 65 and MKE is 67 respectively.. So not quite
there with todays highs temperatures.

Rain chances return to southern Wisconsin early Sunday morning as
a low pressure system tracks across central Illinois eastward
toward Ohio. Expect much of the forecast area to get rainfall by
mid morning Sunday as deformation aloft helps to spread out the
precip field around the low. There will still be a chance for a
few snowflakes to mix in during the morning hours Sunday, but
these chances are expected to be low with little to no snow
accumulations expected. This chance for a few snowflakes will be
limited to a few hours at best where surface temperatures will be
around freezing. Otherwise soundings are pretty consistent on
having a deeper warmer layer near the ground which will keep any
precip as rain. Temperatures are expected be a little cooler and
closer to normal for late November Sunday and Sunday night as
winds shift to northerly.

Patterson

&&

.LONG TERM...
(Issued 415 AM CST Sat Nov 26 2022)

Monday through Friday:

Expect the start of the work week to be influenced by brief upper-
level ridging and a surface ridge extending northward from a surface
high tracking to our south for Monday. Will be looking at high temps
for Monday in the lower 40s, but could see some creep into the mid
and even upper 40s and overnight temps are progged to fall into the
lower 30s for southern WI.

Meanwhile as we see the ridge shifting east into Tuesday and
southerly flow and WAA increase with temps warming into the upper
40s and low 50s, models continue to prog a trough deepening over the
Pacific Northwest overnight Monday and moving into the Northern
Rockie Region earlier on Tuesday. Both the 00z ECMWF and GFS
solutions depict this strengthening trough to interact with a
mid- level shortwave trough trekking across south central Canada
somewhere over the Upper Midwest later Tuesday into Wednesday.
Despite a general agreement between the models on upper-level
pattern through midweek, there is still a bit of uncertainty in
the timing and strength of the system, especially as the latest
00z run has more of a negatively tilted trough while the GFS in
more neutral as the system evolves. Overall as this system works
its way across the central CONUS Tuesday and Wednesday, it is
likely to bring a more active weather pattern to Upper Midwest and
southern WI.

Associated with the upper-level system and its broad area of lift
from the mid-level dCVA, the surface features tend to mimic the two
mid-level troughs where a surface low tracks across the south
central Canada while another stronger low develops in the lees of
the CO Rockies. The northern low looks to gradually meander eastward
into the upper Great Lakes through the day Tuesday, while the
southern low deepens to sub 1000mb across the Central Plains before
lifting into the mid-Mississippi River Valley during the same time.
As these two lows draws closer, most models including the latest
ECMWF/EPS and GFS/GEFS are in agreement the lows will merge/phase
somewhere across the Upper Midwest with the southern low associated
with the main mid-level trough dominating.

While the two surface lows begin to interact, there is once again
a general agreement between ECMWF, GFS, and CMC of the track of
the low as it lifts northward with the center of the
southern/stronger low tracking over southern IA/northern MO by
Tuesday afternoon and elongating as it is progged to phase with
the northern low. However, the phasing is where models begin to
start to diverge a bit where the GFS phases quicker and does not
pivot as far north as the ECMWF solutions, which pivots the low a
bit further west across southern WI. Nevertheless the minor
differences between solutions, there is still a fairly good
consensus of the low to track north and eastward across WI and
into the Upper Great Lakes through Wednesday, which will keep
southern WI on the warm side of the system for Tuesday before the
cold air pushes in behind the system into Wednesday.

Taking a look at precip chances associated with the upper-level
dynamics and surface features, there is a decent chance of southern
WI seeing its next bout of precip. However, the latest 00z EPS and
GEFS are not favoring higher amounts of QPF at this time, especially
given the phasing of two surface features. In fact the ensemble
probabilities for seeing a tenth of an inch or more of QPF within
24 hr is actually low to medium for most of southern WI as the
higher potentials are looking to be closer to the center of the
two lows. Additionally there is concern with the where the dry
slot sets up, which if you believe the 00z ECMWF and the GFS runs
will be over our eastern areas. So precip amounts will be
dictated by the tracks and where the two lows phase and will be
subjected to change over the coming days. Regardless of QPF
amounts, any precip that does develop across southern WI Tuesday
looks to fall in the form of rain especially given the ample low-
level WAA ahead of the system and 850mb temps ranging around
2C-5C. However, any southern shift in the low track or earlier
phasing could end up affecting precip types and amounts and bears
watching how things trend over the coming days.

The phased surface low is progged to lift north and east of the area
overnight Tuesday into Wednesday and a strong push of Arctic air
will filter in behind the system. There is a potential to see
another burst of precip on the backside of the system given hints of
a few ripples of mid-level vorticity on the backside of the trough
aligning with the deformation and the strong push of CAA. However,
models disagree on available moisture with the GFS keeping things
more saturated, while the ECMWF is indicating more dry air. Again
some uncertainty is still at play, but with any precip that does
develop on the backside of the system in the colder airmass would
likely fall as snow through the first half of the day Wednesday.

Otherwise, drier air moves in behind the midweek system as a strong
+1030mb surface high along with upper-level ridge builds down into
the Central Plains and the push eastward for the end of the week
into the weekend. Although too far out for any specific details
given the difference in the models, but there are hints of another
system trekking across the region for next weekend.

Wagner

&&

.AVIATION...
(Issued 415 AM CST Sat Nov 26 2022)

VFR conditions are expected to persist through tonight. Mostly
clear skies early this morning will continue into the early
afternoon. Clouds cover will then begin to increase from the south
Saturday afternoon and evening leading to overcast skies by
tonight. Stronger southwest to west winds aloft this morning will
bring some low level wind shear to most terminal sites. As the
surface winds increase and the strong winds aloft mix down after
sunrise this morning the LLWS will diminish. Southwest winds will
be gusty today before shifting to northerly early Sunday morning.
Later Sunday morning through Sunday evening, chances for rain and
a few snowflakes return to southern Wisconsin.


Patterson

&&

.MARINE...
(Issued 415 AM CST Sat Nov 26 2022)

Southwest winds will increase across the Lake early this morning
and will continue to be gusty throughout the day. A few gusts to
gale force will be possible across the far northeastern portions
of Lake Michigan this afternoon and evening. These gusty winds are
due to a tightening pressure gradient across the Great Lakes
Region. A Small Craft Advisory is in effect through tonight for
the gusty southwest winds.

Early Sunday morning winds will shift to northerly and remain
gusty as a low pressure system tracks across Illinois to Ohio.
Winds are expected to remain below gales as this low pressure
system passes Sunday. Another Small Craft Advisory may be needed
Sunday. High pressure will build into the Great Lakes Region
behind this low on Monday bringing lighter winds.

Patterson

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 10 PM
     Saturday.

&&

$$

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