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000 
FXUS63 KMKX 180231
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
931 PM CDT Tue Sep 17 2019

.UPDATE...

Fog along the lake has thinned in past hour or two of satellite
imagery. However, with clear skies and winds gradually becoming
light, we are starting to see fog further inland. While there is
some cirrus off to the west streaming towards the area, think that
there is enough dry air aloft to keep skies mostly clear tonight.
So, with all of that in mind have added patchy dense fog to grids
tonight for the entire area. Will wait and see just how widespread
the fog is later to see if a Dense Fog Advisory will be needed. 

&&

.MARINE...

The low clouds and fog along the western portion of Lake Michigan
has thinned this evening and have cancelled the Marine Dense Fog
Advisory. It's possible that some dense fog occurs in the near
shore waters but this shouldn't be as widespread as previous
nights. No other changes are needed to the forecast at this time. 

&&

.PREV DISCUSSION... (Issued 612 PM CDT Tue Sep 17 2019) 

UPDATE...

Fog is more limited compared to yesterday at this time. Thanks in
large part to increased winds out over the waters, which have kept
things mixed through the day. There is some subtle marine fog
pushing inland now but it's very localized. With not nearly as
much cirrus as last night, there is a slightly better shot of fog
development further inland and we will be keeping an eye on that
potential tonight. 

AVIATION(00Z TAFS)...

Mainly VFR conditions are forecast thanks to E/SE winds at or
above 5 kts. Patchy fog down to MVFR is possible overnight and
confidence that dense fog develops is very low at this time. For
now have kept a 4-5SM in the TAFs for fog development overnight.
The E/SE winds continue through the night and into Wednesday with
little change in speeds expected as high pressure remains just off
to the east. 

PREV DISCUSSION... (Issued 244 PM CDT Tue Sep 17 2019) 

SHORT TERM...

Tonight And Wednesday...Forecast Confidence Is High. 

Another quiet 24 hours in store for the area. The pattern remains
more or less unchanged with high pressure east and low pressure 
west. The sfc pressure gradient begins to tighten up a bit on 
Wednesday, so a little more wind moving in. We could see more fog 
later tonight into early Wednesday morning. But, there's more flow
above the shallow inversion, so this should promote some 
mixing, hopefully keeping any fog patchy in nature. 

Mid level ridging across the area will lean a bit to the east on 
Wednesday. This will allow the moisture axis out west to slip east
as well. However, it looks like any showers/storms will stay west
of the area through the day. It may sneak into our far west 
Wednesday night. 

Wednesday Night Through Friday...Forecast Confidence Is Moderate.

Models are still generally showing a surface trough stalling over
central Wisconsin Wednesday night into Thursday, then shifting
northward as a warm front on Friday. There continues to be rather
weak upward vertical motion with this feature, along with a weak
low level jet feed Wednesday night into Thursday. Models seem
rather overdone with QPF during this period, especially in eastern
parts of the area. 

For now, tried to cut back PoPs in the east and kept some PoPs in
the west Wednesday night into Thursday, with low PoPs for 
Thursday night/Friday. A good portion of this period may end up 
dry, especially in eastern parts of the area. Warm and humid 
conditions will continue during this time.

LONG TERM...

Friday Night Through Sunday...Forecast Confidence Is Moderate.

Models are generally showing a 500 mb trough trying to push east
into the region Sunday, with a fairly strong cold front pushing
through the area Saturday night into Sunday. Still some timing and
placement differences with features this far out. This system 
looks like our next decent shot at showers and thunderstorms 
across the area. At this time, the front seems rather progressive,
so am not concerned about heavy rainfall yet. Severe potential is
not great at this time, either. Will continue to monitor the
potential for these hazards, given the recent very wet conditions
across the region. Warm and humid conditions will remain until the
front moves through the region.

Sunday Night Through Tuesday...Forecast Confidence Is Moderate.

A trend toward cooler and less humid conditions, but still pretty
nice weather for this time of year, may occur after the cold
frontal passage Sunday night into early next week. High pressure
to the northeast of the region should bring the quiet weather to
the area. Kept most of this period dry for now.

AVIATION(21Z TAFS)...

Look for VFR conditions until later tonight. We have the threat 
of more fog again tonight, but it shouldn't be as widespread due 
to some elevated winds just above the shallow inversion. The 
period of concern tonight would run from about 10z-14z Wednesday. 
Any fog will clear out very quickly Wednesday morning due to winds
increasing quickly in the morning. Overall, expect light winds 
from the southeast to south during the TAF period. 

MARINE...

The fog over the western and northern half of Lake Michigan is 
being quite stubborn and looks like it has potential to hang in 
through the night. It may also clear out as we begin to see 
somewhat more elevated southeast winds tonight compared to the 
past couple of nights. Too much uncertainty for now, thus will 
keep the marine Dense Fog Advisory running through 10 am on 
Wednesday. 

High pressure from the eastern Great Lakes through New England 
will combine with low pressure over the High Plains to bring a 
rather persistent southeast to south flow across Lake Michigan 
into Saturday. Winds on Saturday may approach 30kts as a cold 
front approaches the area. Winds will veer to the west later 
Sunday into Sunday night as the cold front pushes through.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Dense Fog Advisory until 10 AM CDT Wednesday for LMZ261-362.

&&

$$

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