Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 270256
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
956 PM CDT THU MAY 26 2016
.UPDATE...The large upper low centered over CO will gradually move
into the central Great Plains for Fri afternoon and night. This
will send a series of shortwave troughs into S WI during this time
along with the arrival of a sly 25-30 kt llj during Fri morning.
This will aid in moisture transport and warm advection as well as the
northward movement of the warm front through S WI. There will be
scattered showers and isolated tstorms late tnt toward the sw cwa
on the leading edge of the precipitation currently over S IA.
However the precipitation should remain rather weak with limited
CAPE and high CIN over S WI. With the arrival of the
aforementioned llj Fri morning, PWS will rise to at least 1.5
inches with MLCAPEs building to perhaps 1000 J/KG. Mesomodels
suggest several rounds of showers and tstorms Fri into Fri nt but
no severe tstorms are expected.
.AVIATION/06Z TAFS/...Little to no fog tnt given the drier airmass
that arrived Thu afternoon and the high cloud cover that is
currently overspreading S WI. Rounds of showers and tstorms will
then occur Fri into Fri night with the passage of a warm front and
shortwave troughs aloft. A humid airmass will lead to prevailing cigs
around 3.5 kft but with areas of mvfr cigs possible. Much lower
cigs and vsbys in or near tstorms.
.MARINE...Sly winds 10-15 kts and waves of 1-3 feet will prevail
for Fri-Sun. Dense fog will occur at times due to a humid airmass
over the relatively cool waters of Lake MI.
.PREV DISCUSSION... /Issued 327 PM CDT THU MAY 26 2016/
TONIGHT - Confidence...Medium
Weak mid level ridging has taken hold in the wake of the morning
convection. Meso models such as the hrrr, rap and arw are showing a
mostly dry scenario until perhaps later in the night when the low
level anticyclonic flow breaks down somewhat. Some 850 return flow
and a renewed ripple in the mid level flow may be enough generate a
few shra/tsra mainly into the sw cwa later in the night. Per coord
with surrounding wfos have trended pops down and slower than
previously. The NAM and GFS are both showing a little better
potential for precip later and this is reflected in the GFS MOS
pops. Meanwhile the 12z ECMWF has the cwa dry all night. So will
keep the area dry for much of the evening and then nudge the pops sw
to ne later in the night.
FRIDAY - Confidence...Medium
Expecting an uptick in shra/tsra acrs the area with ssw 850 LLJ
strengthening and pointing more into srn wi. The 500 millibar flow
will be ssw and timing ripples in the flow will be challenging.
Splitting the difference between the GFS and NAM we end up with arnd
1000 j/kg. Profile is fairly unidirectional and if anything the CAPE
is leaning more towards the taller/skinny variety. No SPC risk at
this time per SWODY2 though noticed that proggd MBE velocities per
BUFKIT trend slower in the afternoon so perhaps some localized
FRIDAY NIGHT THROUGH SUNDAY...Forecast confidence is medium.
The overall pattern will remain unchanged through the weekend.
We`ll continue to see chances of showers and storms through the
weekend, with the best chance probably Friday evening and again
late Saturday afternoon/evening. Any more specific timing or
resolution on intensities is very difficult given the subtleties
of the forcing mechanisms. We`ll continue to see mid level
troughing west of the area with a series of weak embedded short
waves rotating north through the area during this period. The low
level jet will vary in intensity, but the best jet configuration
is probably on Saturday. Deep wind shear and available CAPE is not
very impressive, thus any focus on severe threat centers on the
isolated stuff. Nothing big and organized at this time. Still warm
and humid, so not a bad holiday weekend overall.
MEMORIAL DAY...Forecast confidence is medium.
The upper level flow configures to zonal, instead of the
persistent cyclonic/trofy pattern we`ve been in. Monday could
actually be dry, but there are some conflicting solutions and
that`s the reason for the small chc`s in the forecast. It looks
like much of the day will be dry with chance likely coming in
later in the afternoon...if at all. Still warm.
TUESDAY THROUGH THURSDAY...forecast confidence is medium.
We seem to get back into the unsettled pattern again by mid week.
A large mid level trough begins to push out of the northern/central
plains with its requisite embedded short waves that will bring the
threat of more showers and storms from time to time. We stay warm
and humid, so there`s enough of that around to support any
convection that tries to fire.
AVIATION/00Z TAFS/...Just expecting some cu and cirrus into the
evening hours with overall quiet wx regime in the wake of the
morning convection. May see a few more shra/tsra creep back into the
area later tonight but more likely on Friday as southerly LLJ
increases and aims into srn wi. The mid level flow pattern will also
be largely from the ssw and may bring a few ripples in the flow into
the area. So this combo may result in sct/nmrs shra/tsra acrs srn wi
from time to time on Friday. By and large a VFR period but will have
to watch for some patchy fog later tonight into friday morning as
winds settle and airmass remains fairly moist. Any onshore component
could pull some of the fog/stratus over the lake into parts of ern
WI later tonight/early Friday.
MARINE...Winds and waves will remain below small craft advisory
levels through at least the weekend. A marine dense fog advisory is
in effect for most of Lake Michigan, including the nearshore waters
and will remain a concern through about mid morning on Friday. Per
webcams there has been some improvement with some wind, but the
persistence of the overall warm and very humid airmass over the
Upper Midwest will result in fog being a concern at least overnight
into early friday.
TONIGHT/Friday AND AVIATION/MARINE...Wood
Friday NIGHT THROUGH Thursday...Davis