Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 201539 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
939 AM CST Mon Nov 20 2017

.UPDATE...

The forecast is on track for today.

&&

.MARINE...

Small craft advisory in effect for 15 to 25 kt winds with gusts
to 30 knots today through Tue afternoon. Strongest low level
southerly winds expected to be this afternoon into the evening.
Possible a few gusts could reach Gale levels but with
strengthening low level inversion over the lake, thinking
strongest wind gusts will remain elevated. Strong cold front will
pass across the near shore waters Tuesday morning resulting in the
winds shifting to the northwest and strengthening once again
after a brief 1-2 hour lull.


&&

.PREV DISCUSSION... (Issued 516 AM CST Mon Nov 20 2017)

UPDATE...Large area of cirrus will sweep across southern WI next
hour or so from the northwest. GOES-16 microphysics enhancement
showing developing thin spots in cirrus shield so widespread
filtered sunshine still expected later this morning and afternoon,
which will aid in temperatures rising to around 50 and gusty
southwest winds this afternoon. Gusts of 30 to 35 mph will be
possible for several hours this afternoon.

AVIATION(12Z TAFS)...Will continue low level wind shear for
several hours at KENW as low level jet brushes far southern WI.
Otherwise, large area of cirrus about to sweep across southern WI
through the morning. Low to mid level moisture remains sparse
ahead of approaching cold front so VFR conditions to continue
through tonight into Tuesday morning. Low level wind shear
conditions return tonight as strong low level jet sets up across
the area.

PREV DISCUSSION... (Issued 326 AM CST Mon Nov 20 2017)

DISCUSSION...

TODAY and TONIGHT - Confidence...Medium to High.

Short term guidance in good agreement.  Core of colder air which
accompanied 300H jet axis has shifted off to the east late Sunday.
This has allowed more zonal flow to usher warmer air into southern
WI and the region overnight, which will continue into tonight ahead
of approaching strengthening cold front.

A warmer day lies ahead as increasing southwest winds carry milder
925H temperatures in the 5 to 7C range into southern WI.  Can not
get too excited however as breezy southwest winds will add a chill
to the air.  In addition, widespread cirrus over the northern Plains
continues to race southeast and will be spreading across southern WI
early this morning.  This cirrus is a result of high level warm air
and moisture advection as well as passing right entrance region of
upper jet. Cirrus should thin later this morning or early afternoon
so at least partial sunshine can be expected.  The limited sunshine
and dry southwest breezes should still allow daytime temperatures to
warm into the upper 40s to  around 50.  Could even be a little
warmer, but hesitant to go to warm due to high clouds.  Low level
winds strengthen this afternoon and tonight.  Could experience some
gusts of 30 to 35 mph for an hour or two before surface cools a few
degrees this evening.  The strong low level mixing and passing mid-
high clouds will keep temperatures mild until late tonight and
Tuesday morning when cold front sweeps through.

Tuesday - Confidence...medium
Cold advection will be dominant with gusty northwest winds. 925
temps fall into the single digits celsius. Low level RH progs
show increasing stratus/stratocu potential from mid morning into
the afternoon so expect a good deal of cloud cover as low level
thermal trough becomes established.

Wednesday - Confidence...Medium
Low level thermal trough eases with westerly 925/850 flow setting
up. More sun and less wind than Tuesday with high pressure
ridging into into the area from the south.

Thanksgiving - Confidence...Medium
Fairly benign northwest mid level flow. Weak surface/850 trough
swings through that heralds in a little more warm air advection.
Dry pattern continues.

Friday - Confidence...Medium
Low level thermal ridging maxes out ahead of cold front approaching
from the northwest. 925 temps reach 10c or even a little higher.
Seeing some cloud potential increasing a bit earlier so not ready
to boost the Superblend in a meaningful fashion just yet. Looks
like best potential for shra arrives Friday night.

Saturday and Sunday - Confidence...Medium
Another round of cold air advection sets up in the wake of the
fropa. Coldest 925 temps arrive Saturday night into Sunday
morning.

AVIATION(09Z TAFS)...AMDAR descent sounding into KMKE measured
southwest winds at 44 knots at about 1500ft above the ground.
Hence added low level wind shear into eastern TAFs through the
early morning. VFR conditions to continue with passing mid-high
clouds this period. Even stronger low level winds expected over
southern WI later this afternoon and tonight. Winds are expected
to increase to 45 to 55 knots less than 2K feet off the surface
resulting in an even stronger case for low level wind shear
despite gusty surface winds.

MARINE...Several vessels in and near the near shore waters have
been reporting sustained winds of 18 to 23 knots last several hours.
Lake temperature is in the mid to upper 40s, which is creating a
steep low level inversion over the lake surface. This is allowing
gusty southwest winds to mix down to the lake surface and will
continue to do so through the morning with gust potential up to 30
knots.  Hence wl move up start of Small Craft Advisory to current
time.

Strongest low level winds expected to be this afternoon into
the evening.  Possible a few gusts could reach Gale levels but with
strengthening low level inversion over the lake, thinking
strongest wind gusts will remain elevated. Hence wl hold off on
upgrading to Gale Warning for now. Strong cold front will pass
across the near shore waters Tuesday morning resulting in the
winds shifting to the northwest and strengthening once again after
a brief 1-2 hour lull.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 6 PM CST Tuesday for LMZ643>646.

&&

$$

Update...Cronce
Today/Tonight and Aviation/Marine...MBK
Tuesday THROUGH Sunday...Collar



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