Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 281314 AAA
AFDMKX

Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
814 AM CDT Sun May 28 2017

.UPDATE...


&&

.AVIATION(12Z TAFS)...

Expect area of showers and a few storms to move through the
eastern portions of the area over the next few hours, exiting by
later this morning. 2 mile visibilities and 2500 foot ceilings are
possible in the showers and storms. Otherwise, look for VFR
conditions into this afternoon.

There is another chance for showers and storms between 19Z today
and 00Z Monday. Small hail and gusty winds are possible in any
storms, but they will be scattered in nature. Diurnal cumulus
clouds around 5000 feet are expected this afternoon as well. Lake
breeze may try to flip the northwest to west winds to the
northeast near the lake this afternoon, but not enough confidence
to mention in lakeshore TAF sites. VFR conditions are forecast
into tonight, with westerly winds.

&&

.PREV DISCUSSION... (Issued 330 AM CDT Sun May 28 2017)

TODAY AND TONIGHT...Forecast Confidence Is Medium.

Area of showers continues to develop across the western counties
and points to the southwest and northeast of there. This is in
association with some low level frontogenesis response, as well as
with differential cyclonic vorticity advection associated with
approaching 500 mb shortwave trough.

These features will shift east through the area through the
middle to late morning hours, bringing this area of showers
through the area. This is supported by several mesoscale models.
Area forecast soundings support isolated thunderstorms as well.

The mesoscale models suggest that another broken band of showers
may shift east through the area this afternoon, with a secondary
cold front and perhaps some differential cyclonic vorticity
advection. It appears that dew points may lower somewhat this
afternoon, with westerly winds.

Still, area forecast soundings suggest several hundred J/kg of
mean layer CAPE this afternoon. There is enough instability and
shear for some small hail and gusty winds with any storms this
afternoon. No severe weather is expected. Kept chance PoPs going
for the eastern 2/3 of the area this afternoon. Highs should be
around or in the lower 70s across most of the area.

Cold air advection tonight should bring drier air into the region,
and perhaps bring clearing skies to western portions of the area.
It may clear out more in the east than currently forecast. Lows
should remain in the lower to middle 50s.

Memorial Day and Tuesday...Forecast confidence is medium

Mid level low will move from Lake Superior across Ontario. The
surface low will remain fairly stationary over Ontario so westerly
flow will dominate. Several waves of vorticity will drop through the
region with more pronounced shortwaves moving through each
afternoon. Weak frontogenesis on Monday and a few hundred J of Cape
by the more conservative ECMWF result in showers and thunderstorm
chances. The morning should start out with some sun, especially
in the south, but expect scattered afternoon cloud development.

There are precip chances again on Tuesday with weak warm
air advection, but very little instability so will hold of on
thunder mention. 850 winds increase to 25-30 knots during this time
and steep low level lapse rates will promote mixing and breezy west
winds both days.

Wednesday and Thursday...Forecast confidence is high.

Surface high pressure will slide south of the state bringing mainly
dry weather and sunny skies. Precip and thunder chances return
Thursday night with return flow, a push of warmer low level air, and
an approaching frontal boundary.

Friday through Sunday...Forecast confidence is low.

A frontal boundary looks to be over the region on Friday bringing
precip and thunder chances through the day. Then models diverge. The
ECMWF brings low pressure and precip through the region while the
GFS has high pressure. As a result, a lot of uncertainty with
temperatures too.

AVIATION(06Z TAFS)...

High based sct showers will prevail for the early morning hours
until a second round of rain arrives mainly after 09Z. This area
of showers and slight chances of tstorms will last through the
entire morning and will lead to Cigs of 1-3 kft and Vsbys of 2-5SM
including light fog. The main area of rain will exit to the east
by afternoon with Cigs rising to sct-bkn050 along with good Vsbys.
Small chances of showers and tstorms will remain however.

MARINE...

There is the possibility of some fog development over the
nearshore waters of Lake Michigan this morning with the showers
moving through. Dew points will remain high enough where some fog
may form. For now, will hold off on a fog mention and watch area
web cameras to see if it does form.

A few thunderstorms are possible this morning with the passing
showers. Thunderstorms this afternoon may produce small hail and
gusty winds.

Gusty west winds are expected Memorial Day, with frequent gusts to
25 knots possible. The tight pressure gradient may linger into
Tuesday, with more frequent 25 knot gusts possible. A Small Craft
Advisory may be needed for Memorial Day and Tuesday.

&&

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

$$

Update...Wood
Today/Tonight and Aviation/Marine...Wood
Monday THROUGH Saturday...Marquardt


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