Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 222012
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
310 PM CDT FRI JUL 22 2016
.TONIGHT AND SATURDAY - Forecast Confidence...Medium.
Will convert the Excessive Heat Warning to a Heat Advisory into
early evening given how the clouds have held back the heat indices.
Will leave ongoing Heat Advisory as is.
Could see a storm or two in the southwest forecast area late this
afternoon into the evening within moisture/instability gradient.
Pretty quiet on the radar for now though. Looks dry then overnight,
with precip chances increasing from west to east on Saturday as
deeper moisture begins to advect eastward and a shortwave
approaches. Just stuck with chance pops through Sat afternoon for
now, due to uncertainty among models in timing of the wave and
resultant storm placement. There are solutions that would bring
storms into at least the west by late afternoon.
Should stay pretty mild tonight. Could see some fog overnight into
early Saturday morning due to light winds, recent rainfall, and high
low level moisture. MOS and soundings support the fog potential,
though will depend on extent of cloud cover.
Highs on Saturday will be up near 90 most places. The exceptions to
this will likely be in the east due to onshore winds and maybe in
the southwest due to higher possible cloud cover or earlier arrival
of showers/storms. Will be another hot and humid one, with heat
indices in the 95-99 range most places, except for near Lake
.SATURDAY NIGHT THROUGH MONDAY - Forecast Confidence...Medium.
The very warm temperatures will continue into Sunday until drier and
slightly cooler air invades southern WI behind passing cold front.
At this time, enough clearing is expected to help temperatures climb
back into the upper 80s to lower 90s on Sunday. The combination of
hot temperatures and lingering dewpoints in the lower 70s is
expected to push the Heat Index back into the 95 to 100 degree range
for the fourth day in a row across much of southern WI. There is
some uncertainty regarding amount of lingering cloud cover and
timing of frontal passage. If confidence increases on hot and humid
conditions continuing Sat and Sun, then next forecast shift may be
issuing a Heat Advisory for four consecutive days of Heat Indicies
reaching the mid 90s to around 100.
Will continue likely wording for thunderstorms Saturday night as
tilting low level jet ushers strong surge of moisture advection
across WI. Better upper level synoptic lift and nose of llj favors
areas to the north, but thinking convection likely to carry along
instability gradient toward the southeast into srn WI overnight.
Corfidi Vectors favor southeast movement and do drop off during the
night. In addition, heights at both 500 and 700 levels drop
slightly overnight on short term guidance indicating weak mid-level
trof passage. After 12z Sunday, GFS and NAM coming into better
agreement on carry surface cold front across southern WI during the
morning and early aftn. Atmosphere may have enough time to recover
but veering low level winds and drier air arrival should limit
redevelopment. Hence wl only carry low chance pops on Sunday. More
comfortable and dry conditions will settle in Sunday night and carry
MONDAY NIGHT THROUGH FRIDAY - Forecast Confidence...Medium.
Drier more zonal flow looks to continue for at least the first part
of the extended period. Temperatures and humidity levels will be
more seasonal. Medium range guidance in fair agreement on zonal
flow carrying short wave trof across the upper midwest around
Wednesday or Thursday. Short wave also amplifies slightly as it
moves across the region. Enough atmospheric moisture will be
available to continue small pops for thunder as weak surface
boundary moves through the area.
.AVIATION/00Z TAFS/...A few MVFR ceilings are lingering in the west
this afternoon, but most places have mixed to VFR. VFR conditions
are then expected into the evening, with some patchy/areas fog then
May see a few storms at times in the west or southwest forecast area
this afternoon through Saturday. Better chance for storms across
southern Wisconsin looks to be Sat evening and overnight.
Could see some fog at times through Saturday due to higher moisture
lingering over cooler Lake Michigan waters. Webcams and satellite
currently not showing fog...but certainly something to keep an eye
Will likely see storms return by Saturday evening or night, with a
chance lingering into at least Sunday morning.
WI...HEAT ADVISORY until 7 PM CDT this evening for WIZ056-062>072.
TONIGHT AND SATURDAY/AVIATION/MARINE...DDV
SATURDAY NIGHT THROUGH FRIDAY...MBK