Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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140
FXUS63 KMKX 270204
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
904 PM CDT TUE JUL 26 2016

.UPDATE...

High pressure will provide a persistence forecast for tonight.
Skies will be clear and we could see some patchy fog out there
later tonight. Shallow stuff that will mix out readily by/shortly
after sunrise.

The forecast for Wednesday is rather tricky with various model
guidance out of agreement with respect to initial timing of
possible thunderstorm development in the afternoon. Some guidance
holds things off until later in the evening, while others fire it
off by mid afternoon. It would appear the early model trends are
too quick to push the triggering boundary south into the area.
But, we`ll have to see how the activity upstream overnight
behaves. If it remains on the weaker side, then redevelopment
tomorrow will occur farther to our west and north, delaying onset.

&&

.AVIATION/06Z TAFS/...

Similar to last night, VFR conditions can be expected overnight,
but there could be about an hour of reduced vsbys due to shallow
fog just prior to sunrise, especially toward KMSN. Wednesday will
be VFR with a chance of showers and thunderstorms entering the
forecast toward mid afternoon. Timing is questionable and could be
delayed until after 00z Thursday. Coverage/chances look low enough
to leave out of the TAF until after 00z Thu. At this point, no
severe weather is expected with these storm chances.

&&

.MARINE...

Light wind regime remains in place into Wednesday with
high pressure. May see an uptick in an onshore component
Wednesday night into Thursday as low pressure and a frontal boundary
sag south of the area.

&&

.PREV DISCUSSION... /Issued 321 PM CDT TUE JUL 26 2016/

TONIGHT - Confidence...High

Influence of surface high expected to keep the area dry. Meso models
and most synoptic, except the GFS, keep the area quiet with better
forcing closer to the frontal boundary across northern WI. So expect
the diurnally drive cu field to dissipate with only some patchy fog
potential for the balance of the night.

WEDNESDAY - Confidence...Medium

500 millibar shortwave approaches from the Plains. The progs also
show a surface low or a trough (depending on the model) moving into
the srn MN/nrn IA vcnty. The models are keeping the better
convective chances closer to the low/trough and also near frontal
boundary that sags a bit further south from nrn WI. Model QPF
placement tied this front shows that the northern CWA would be most
vulnerable to seeing shra/tsra. In fact the ECMWF and GEM have
trended more towards the wetter look of the GFS. So have the higher
POPS in place there and in some cases went above Superblend in the
far north. 925 temps remain in the low 20s even some mid 20s celsius
from the NAM so more toasty temps well into the 80s expected.
Evolving onshore flow will turn it cooler lakeside.

THURSDAY ...Confidence...MEDIUM

Precip and thunderstorm chances continue through Thursday as a
weak area of low pressure moves south of the state. Additional
forcing is provided by another mid level shortwave, and upper
level divergence redevelops over southern WI as a secondary weak
upper jet max develops over eastern Upper Michigan into Ontario.
Drier and cooler air moves in across the region as winds shift to
the northeast. Highs in the upper 70s are expected for the later
half of the week.

FRIDAY THROUGH SATURDAY...Confidence...MEDIUM

Models are trending drier for this period. Upper forcing is lacking
but there are subtle shortwaves within NW upper flow. There is some
weak warm air advection and surface convergence which is resulting
in models showing some spotty precip at times. Instability is
marginal especially closer to Lake Michigan and lacking during the
overnight hours. Model consensus yields slight chance pops during
this period and will only maintain any thunder chances during the
daytime hours.

SUNDAY THROUGH TUESDAY...Confidence...MEDIUM
High pressure develops early in this period over the Great Lakes.
A ridge/trough pattern sets up over the conus and then shifts into
WI bringing dry weather and warmer temperatures. There is
disagreement beyond this time about whether the ridge will
maintain itself.

AVIATION/00Z TAFS/...
VFR mostly skc through much of tonight. Patchy fog may develop
later tonight with the light wind regime. Increasing chances of
tsra for TAF sites as Wednesday afternoon wears along with better
mid level support and southward sagging frontal boundary from nrn
WI. All in all VFR conditions expected to prevail.

MARINE...
Light wind regime remains in place into Wednesday with
high pressure. May see an uptick in an onshore component
Wednesday night into Thursday as low pressure and a frontal boundary
sag south of the area.

&&

.MKX Watches/Warnings/Advisories...
WI...None.
LM...None.
&&

$$

UPDATE...Davis
TONIGHT/Wednesday AND AVIATION/MARINE...Collar
Wednesday NIGHT THROUGH Tuesday...Marquardt



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