Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 201536 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1036 AM CDT SAT AUG 20 2016

.UPDATE...

Numerous showers and thunderstorms have moved off to the north and
east this morning as sfc low pressure moves to the northeast. A
cold front draped across northeast Iowa and southwest Wisconsin,
indicated by a wind shift axis, will slowly make its way eastward
the rest of the morning and into the afternoon today. Some
scattered showers and thunderstorms are possible with this cold
front, especially this afternoon. There is still a Marginal risk
for severe weather along a line from Fond du Lac to Sullivan to
Sharon and points eastward for these afternoon storms.

High temperatures in the 70s look to be on track today given
current temps in the upper 60s and lower 70s now, with a little
break in the rainfall for now before the second round develops
later this afternoon.

&&

.AVIATION/18Z TAFS/...

Area of low pressure over S WI is supporting mainly MVFR and IFR
cigs across the TAF sites this morning. Showers and thunderstorms
that rolled through earlier this morning have moved off to the
north and east. Expect a break for most places throughout the
morning and into the early afternoon before another round of
showers and storms develops along a cold front. High-res guidance
show these storms should be more scattered in nature.

&&

.MARINE...

A Small Craft Advisory will remain in place for this afternoon and
tonight. Low pressure over Wisconsin is expected to strengthen as
it reaches northeast Wisconsin this afternoon. This will result in
increasing south winds before turning to the southwest to west
this afternoon as a cold front passes through. There will be a
chance of thunderstorms with the cold front.

&&

.PREV DISCUSSION... /Issued 337 AM CDT SAT AUG 20 2016/

TODAY AND TONIGHT...Forecast Confidence Is Medium.

Numerous t-storms associated with surge of warm air advection and
frontogenesis shifting north of the area. However next batch of
showers and storms already pushing into the southwest CWA. This
batch associated with approaching mid-level short wave getting
shoved northeast by main wave farther upstream over NE/SD area.

Expect these showers and storms to sweep across southern WI
through mid-morning, followed by diminishing trend. May be enough
time for atmosphere to destabilize as cold front moves through the
eastern CWA this afternoon for one or two storms to take on severe
characteristics.

Short term guidance now in reasonable agreement on low pressure
rapidly intensifying as it moves across WI today. GFS and NAM have
come into better consensus. Hence after early morning activity,
expect more scattered to numerous showers and t-storms to
redevelop later this morning and afternoon.

However, drier air wrapping around the strengthening low pressure
system will reduce the threat across the western area this
afternoon behind the passing cold front.

Sauk county received 1.50 to 2.50 inches of precip Friday
morning, with another three quarters inch overnight. Contemplated
issuing Flash Flood Watch, but expect this morning`s activity to
result in lighter qpf amounts, and more scattered activity along
the front late this morning and early afternoon. Sauk County
dispatch did not report any flooding issues around 07z. Hence wl
not issue FFA at this time.

Patchy fog likely to accompany lighter winds this morning, in
humid airmass as sfc low pressure passes through, and where it is
not raining.

Few showers may affect parts of the north tonight, as mid-level
deformation zone associated with low grazes central WI. Otherwise,
breezy west winds will pull cooler and less humid air across the
area for Sunday.

SUNDAY THROUGH MONDAY NIGHT...Forecast Confidence Is Medium.

Models are in decent agreement with gusty west winds slowly
decreasing on Sunday, as pressure gradient weakens. 500 mb flow
remains cyclonic over the region, as the main shortwave trough
shifts off to the northeast. Differential cyclonic vorticity
advection from another vorticity maximum shifts southeastward
across the northeast half of the forecast area during the day.

Area forecast soundings show scattered to broken cumulus
development during the day. Kept lower end POPs for light rain
showers in the north and east for Sunday, given the above
mentioned features. A cool day is expected, with highs only in the
lower to mid 70s. Cool lows in the lower to mid 50s are forecast
for Sunday night, per 925 mb temperatures.

Models then are in good agreement with showing the 500 mb
cyclonic flow transitioning into a ridge by later Monday night.
High pressure passing south of the region Sunday night into Monday
will result in dry conditions, continuing into Monday night.

South to southwest winds developing Monday into Monday night
should allow for warm air advection to develop. This should lead
to gradually rising temperatures, closer to seasonal normals.

TUESDAY THROUGH FRIDAY...Forecast Confidence Is Medium.

ECMWF/GFS are in decent agreement with features during this
period. They shift the 500 mb ridge to the east Tuesday, with a
shortwave trough shifting through the area in southwest flow
Tuesday night or Wednesday. Warm air advection continues into
Tuesday night, with the cold front passing east through the region
late Wednesday or Wednesday night.

Kept consensus POPs for this period, and may need to raise these
in later forecasts if these models continue to show this trend.
Temperatures look to remain near seasonal normals, with more humid
conditions.

Cold air advection with drier air then should work into the
region for Thursday into Friday. Thursday POPs may need removal in
later forecasts if dry look continues in models. Pleasant
temperatures are expected.

AVIATION/12Z TAFS/...

Several more periods of showers and t-storms will affect TAF
sites, as low pressure and a cold front move through the region.
Patchy stratus will continue to expand, as winds diminish and
more rain pushes through the region. MVFR cigs are expected with
patchy IFR. Fog may also reduce the visibility for several hours
this morning.

MARINE...

Small Craft Advisory will remain in place for this afternoon and
tonight. Approaching low pressure is expected to strengthen as it
passes across Wisconsin today. This will result in increasing
south to southeast winds this morning. The winds will turn to the
west to southwest this afternoon, as a cold front passes through.
Several more periods of showers and t-storms are expected as
these weather features move through the region.

BEACHES...

Strengthening low pressure passing through Wisconsin today will
result in increasing south to southeast winds this morning,
turning to the southwest to west this afternoon after a cold front
moves through. Waves are expected to increase to 2 to 4 feet later
this morning and afternoon, resulting in a Moderate Swim Risk at
Lake Michigan beaches into this evening.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...SMALL CRAFT ADVISORY from 1 PM this afternoon to 10 AM CDT
     Sunday for LMZ643>646.

&&

$$

UPDATE...JTS
TODAY/TONIGHT AND AVIATION/MARINE...MBK
Sunday THROUGH Friday...Wood



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