Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 202252
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
552 PM CDT Sat May 20 2017

.AVIATION(00Z TAFS)...

Surface low pressure will track from western Iowa to northwest
Wisconsin tonight into Sunday morning. An occluded front
stretching east from the low will swing north through the forecast
area between 06-13z Sunday. Look for southeast winds to veer around
to the southwest and west in the wake of the front. Showers and
possibly a thunderstorm may accompany the front as it passes
through. Additionally, winds will diminish in the trough axis that
defines the occluded front. We will see visibilities drop with
the weaker winds and CIGS will remain IFR until the trough swings
through. Look for MVFR CIGS thereafter through the TAF period.
The exception may be across the southeast where CIGS could go to
VFR for a time Sunday morning.

&&

.PREV DISCUSSION... (Issued 331 PM CDT Sat May 20 2017)

SHORT TERM...

Tonight and Sunday...Forecast Confidence is MEDIUM...

Rain associated with the mid level short wave, broad 850 jet, and
warm air advection will continue to lift north of the region this
afternoon. Then we will have a break in the rain until later this
evening. A surface low will move across Iowa into NW WI overnight
with an occluded front moving across southern WI. This brings
another chance for showers. There is up to 300 J/KG CAPE so still
a chance for some thunder. Some fog is possible until this front
clear the area.

The upper low will move across MN with cyclonic flow lingering
through Sunday. Low level moisture will hang on the backside of
this system so clouds will prevail through the day. The GFS is
showing some light precip but most other models are dry.

Sunday night through Wednesday...Forecast confidence medium.

The large occluded low over Ontario, Canada will continue to fill
for Sun nt-Mon. A shortwave trough rotating around the occlusion
will track ewd across central WI Sun nt with any rain chances
staying to the north. Another upper trough approaching from the
nw and occlusion will approach for Mon-Mon nt. A sfc trough will
develop with low level warm advection and a 850 mb thermal ridge
developing over srn WI. Thus sfc temps will rise to near 70F for
Mon. The approaching sfc trough/cold front and upper trough will
bring chances of showers for Mon aft-nt. Very marginal CAPE may
form so slight chances of tstorms Mon aft-eve over south central
WI.

The upper trough may then induce weak cyclogenesis from anywhere
from srn WI to nrn IL and ewd for Tue-Wed. Since the upper trough
may become an upper low while getting re-inforced with shortwaves
from the north, the system speed will be low. Thus rain is likely
on Tue and may linger into Wed. Below normal temps to prevail.

LONG TERM...Thursday-Saturday...Forecast confidence medium.

The large upper trough over the central and eastern Great Lakes
will slowly move ewd Thu-Fri. High pressure will arrive Thu nt-
Fri. The high will then shift ewd for Sat with sly flow and warm
advection. This period will thus see a gradual warming trend.

AVIATION(18Z TAFS)...
400-800ft ceilings will stick around through the evening. Some fog
is possible, especially in the east tonight, but confidence on
this is low. A weak front will move through overnight helping to
somewhat improve ceilings and fog. 1-2kt ceilings will likely
continue into Sunday but they may raise to 3.5-5kft in the east
Sunday afternoon.

MARINE...
Northeast to east winds will continue to weaken today. High waves
will linger through the evening as winds become southeast. There
is a small chance for showers and thunderstorms later this
evening. Southwest winds will approach small craft levels on
Sunday and Monday.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 9 PM CDT this evening for LMZ645-646.

     Small Craft Advisory until 1 AM CDT Sunday for LMZ643-644.

&&

$$

Update...Davis
Tonight/Sunday and Aviation/Marine...Marquardt
Sunday Night through Saturday...Gehring



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