Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 180156
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
856 PM CDT SAT SEP 17 2016
.UPDATE...Stratocumulus deck over west central WI continued to
shrink and dissipate through the early evening as only a few
patches of sct-bkn around 4k feet remain. With a moderate
overnight inversion expected and temperatures falling a few
degreees below the crossover temperature, need to add at least
patchy fog mention to the late night. Lowered temperatures in a
few locations as well. Lingering thermal trof and weak passing
mid-level short wave may cause some cloud redevelopment but low
levels do dry out during the late night, adding to a better chance
of fog development.
.AVIATION/06Z TAFS/...Stratocumulus deck continued to shrink and
dissipate through the early evening. Only a few patches of sct-bkn
around 4k feet remain in the vicinity. Thermal trof and weak 5H
wave does pass across srn WI late tonight into early Sunday which
may generate more patchy clouds during the late night. However,
low levels begin to dry out later in the night, so thinking some
patchy fog may develop and affect several taf sites late tonight.
For now due to uncertainty, wl keep the visibility restriction in
the MVFR category.
.MARINE...Recent MODIS imagery showed upwelling of colder sub-
surface water has taken place over the past day or so. Lake
surface temps have fallen into the 50s. A weak pressure gradient
is expected across southeast WI and lower Lake MI on Sunday. The
combination of the weak pressure gradient and a tighter thermal
gradient should result in a better chance for a lake breeze to
develop near the lake shore by Sunday afternoon. Hence went with
more SE winds.
.BEACHES...The 2016 Beach Hazard season on Lake Michigan will end
tomorrow, September 18th. The last Recreational Beach Forecast for
beaches along Lake Michigan from Sheboygan county to Kenosha
county will be issued around 5 pm September 18th. The National
Weather Service Beach Hazard Program will return in May 2017,
shortly before the Memorial Day weekend.
.PREV DISCUSSION... /Issued 326 PM CDT SAT SEP 17 2016/
TONIGHT AND SUNDAY...Forecast Confidence...High
The northern portion of high pressure will build into southern
Wisconsin tonight, then slide southeastward a bit on Sunday. Should
see skies eventually turn mostly clear this evening into tonight as
the high builds in and daytime heating is lost. Should see a lot of
sunshine then on Sunday.
Could see a little fog develop tonight, the best chance in low lying
areas such as the Wisconsin River valley. Seems like just enough
wind in the lower levels to keep widespread fog from forming.
Temps tonight and Wednesday will remain a few degrees above normal.
Sunday night through Tuesday...Forecast confidence medium.
Swly flow and low to middle level warm advection is expected Sun
nt into Mon. This is in response to a 120 kt wly jet stream
becoming established along the US and Canadian border. The nose of
the strong upper jet will drive a strong shortwave trough across
the nrn Plains and nrn Great Lakes. The strongest surge of thetae
advection will be Mon morning followed by the gradual passage of
the cold front for the afternoon and evening. Isolated to
scattered showers and tstorms will be possible with the thetae
advection but more favored storm organization will be along the
cold front. MLCAPEs are expected to climb to 500-1000 joules along
the cold front. Expect the initiation to be near the WI and IL
border with at least scattered coverage. The Marginal Risk by SPC
looks good given the deep layer shear of 40-45 kts. Above normal
temps will continue for the early week with lower to middle 80s on
Mon just ahead of the cold front.
LONG TERM...Wednesday through Saturday...Forecast confidence
A low amplitude, but broad upper ridge will shift from the nrn
High Plains to the Great Lakes from Wed to Sat in response to a
large upper trough moving from the wrn USA to the nrn High Plains.
This results in a warm front nosing into srn WI on Wed and
becoming stalled for the remainder of the week. Thus relatively
warm and humid conditions along with good chances of showers and
thunderstorms each day. The cold frontal passage will be Sat or
Could see MVFR ceilings try and sneak into the northwest this evening
into tonight. High pressure will build overhead tonight, so not out
of the question to see some fog develop later in the night.
Otherwise, VFR conditions will then prevail through Sunday under
Winds will be lighter under high pressure Sunday. Southwest winds
could approach Small Craft Advisory levels on Monday as the pressure
gradient tightens ahead of approaching low pressure.
TONIGHT/Sunday AND AVIATION/MARINE...DDV
Sunday NIGHT THROUGH Saturday...Gehring