Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 201712
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1212 PM CDT Fri Oct 20 2017

.UPDATE...Warm southwesterly breezes and sunshine helping
temperatures rise 1-3 degrees faster than anticipated. May have to
bump up temps several degrees for the afternoon, more into the 76
to 79 degree range, which remains close to the records for today.
No sign of a lake breeze on KMKX/KMKE radars along the lakeshore
due to breezy southwesterly flow. However as the winds lose their
gustiness around 23-00Z, winds may briefly turn onshore for
several hours.

&&

.AVIATION(18Z TAFS)...VFR conditions to continue this period, but
look for a gradual increase in mid-high level cloudiness.
Increasing winds will cause low level wind shear tonight with
winds to 40 knots at 2k feet agl.

&&

.PREV DISCUSSION... (Issued 1009 AM CDT Fri Oct 20 2017)

UPDATE...Another warm day with only wispy passing cirrus expected
as atmosphere remains parched. Southerly breezes may gust as high
as 20 to 25 mph. 925H temps and sunshine will aid the temperature
in peaking in the mid to upper 70s this afternoon, which will be
getting to within a few degrees of the record high for today.

Increasing southerly winds on the backside of departing high
pressure ridge will begin to pull deeper column moisture from the
southern plains toward Wisconsin over the next 24 hours. So
moisture will be in place as strong cold front advances across the
northern plains into Wisconsin later Saturday and Saturday night.

MARINE...Developing breezy south to southwest winds should
prevent lake breeze from making much penetration inland, keeping
the lake breeze close to the shore. Winds are likely to be a bit
more southerly over the near shore waters. Surface water
temperatures have lowered into the mid 50s to around 60 per latest
satellite imagery. Tightening pressure gradient will result in
strengthening southerly winds tonight and Saturday. The warmer
lake waters may allow some of the stronger winds to mix down to
the lake surface later tonight, and especially on Saturday and
Saturday night. Hence a Small Craft Advisory may be issued this
afternoon for this period, likely extending into Sunday.

PREV DISCUSSION... (Issued 640 AM CDT Fri Oct 20 2017)

UPDATE...The forecast is on track for today and tonight. South
winds and warm temps continue.

AVIATION(12Z TAFS)...VFR conditions continue today and tonight.
LLWS is expected to develop tonight via a swly 45 kt LLJ.

PREV DISCUSSION... (Issued 316 AM CDT Fri Oct 20 2017)

SHORT TERM...

Today and Tonight...Forecast Confidence is High.

Sly winds and mostly sunny skies will continue to support a warm
airmass for today. 925 mb temps around 18C yields high temps in
the mid-upper 70s. A swly 45 kt LLJ tonight will then help
maintain the mild temps with lows only in the upper 50s. High
clouds will increase through the night as the upper level flow
becomes sswly with embedded weak vorticity maximums.

LONG TERM...

Saturday and Sunday...Forecast confidence is high:

Low pressure and an associated cold front will approach the area
on Saturday, with models in fair agreement in the trough/front
passage late Saturday night into Sunday. Pretty good surge of
moisture ahead of this system, with model precipitable water
values rising to around 1.50 inches. Decent forcing with this
system too, so bumped pops up even more. Could be a little thunder
Sat night while instability hangs around. A rumble or two is not
out of the question Sunday, but not much instability left as the
main area of showers moves through.

Still looks mainly dry day Saturday, with some sunshine likely.
Bumped high temps up over most models given continued mild temps
aloft. High temps Sunday may end up occurring early in the
morning most places, as it will cool down during the day with the
rain/clouds and frontal passage.

Monday through Thursday...Forecast confidence is low to medium:

Models are still struggling to come into agreement with finer
details of the pattern for early next week. A potent trough will
approach during the day Monday, then slow down as it moves through
Monday night and Tuesday. Timing/strength/placement of resultant
surface low development remains the biggest issue. Though models
all have on and off rain chances Mon-Wed, the differences between
them impact temperatures and precip amounts.

Another trough is progged to move through Thursday or Thursday
night, possibly bringing a few showers. Not a lot of moisture with
this system, so kept precip chances on the lower end.

Temps will be a few degrees above normal Monday, then likely cool
to below normal for Tue/Wed. Should see milder temps Thursday
ahead of the next trough. Consensus of models produced highs
around normal, though a couple models are a few degrees warmer.

AVIATION(09Z TAFS)...VFR conditions continue today and tonight.
LLWS is expected to develop tonight via a swly 45 kt LLJ.

MARINE...A Small Craft Advisory will likely be needed for Sat
into Sun. Breezy sly winds will develop Sat AM and continue
through Sun AM. Waves of 3-6 feet will prevail during this time
with the highest waves north of Port Washington. The winds will
then turn wnwly and decrease Sun afternoon with the passage of a
cold front. The waves will be subsiding through the afternoon.

&&

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

$$

Update...99
Today/Tonight and Aviation/Marine...99
Saturday THROUGH Thursday...99



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