Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 221510
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1010 AM CDT THU SEP 22 2016
.UPDATE...No change to Flash Flood Watch at the moment. Will
reevaluate the need for an extension for afternoon package as all
12z data arrives. Focus for further development will be 850/925
baroclinicity setting up north of where surface boundary sets up
to our south. Meso models showing various solutions with respect
to where best precip zone lays out. Seeing greater focus in the
southwest half of the cwa from the NAMNest and HRRR. 06z GFS and
00z ECMWF tend to favor the meso solutions that skew more towards
the southwest CWA. 500 millibar heights will be building tonight
into Friday. So focus will largely be in the low levels with
isentropic forcing associated with 850/925 baroclinic zone.
.AVIATION/18Z TAFS/...Webcams show a continuation of fog
dissipation in the eastern CWA closer to the Lake. IFR/LIFR cigs
slow to erode but have seen some improvement in this regard. As
low level boundary sags to our south tonight the guidance
continues to support a reinforcing of the lower cigs across more
of the CWA which would linger into Friday. This is supported by
the MOS data and BUFKIT soundings. Convective trends will be
watched carefully tonight as lingering 850/925 baroclinic zone
and overrunning associated with it acts as focus for further
development tonight into Friday. meso models show some
disagreement on placement but a little more emphasis being placed
towards the southwest cwa.
.MARINE...Southeast winds will back east, and then northeast winds
tonight and increase overnight into Friday. Winds and waves are
expected to remain below small craft advisory levels, but conditions
will be more elevated than what we`ve seen over the past few days.
Small craft may want to exercise caution, especially Friday
afternoon and night.
.PREV DISCUSSION... /Issued 324 AM CDT THU SEP 22 2016/
TODAY AND TONIGHT...Forecast confidence is medium.
Unfortunately, the pattern remains largely unchanged through
tonight. Much of our meso-scale guidance is struggling in this weak
flow, high moisture environment. The one positive aspect is that
we`ll see more in the way of mid level ridging as a short wave exits
early today. This should help decrease the convection today as the
deeper support wanes. Still, with precipitable water values are in
the 1.7 to 1.8 range, very high for later September, and with the
sfc-h8 front still lingering, we have a persistent chance of showers
and storms through tonight. That sfc front will eventually push
south tonight as sfc ridging pushes south across the Great Lakes.
The better rain chances should stay north and west of Madison today
and even into tonight. Despite the sfc front being south tonight,
the 850mb front will be to the north and this is where the elevated
convection will focus. Given the overall weak low level flow, any
storms are highly influenced by the outcome of previous storms.
Meaning, the cold pool outflow will kick out boundaries that then
become new genesis regions for new storms. These areas are tough to
predict and is why our high resolution models struggle.
The main flooding concerns remain across Sauk, Marquette and
Columbia county where rainfall amounts have been the highest over
the last few days. Will keep the flash flood watch going, but will
trim out Sheboygan and Dodge counties due to the lack of decent
rainfall there and the drier look there today and tonight. The
areal flood warning for Sauk, Marquette and Columbia counties goes
until 815 this morning and I`ll keep that going as runoff from all
the rain could still cause some water problems.
FRIDAY AND SATURDAY...Forecast Confidence...Medium
Deep moisture will remain overhead through the end of the week.
Precipitable water values will be 1.5 inches or better Friday and
Saturday. Kept precip chances going Friday into Saturday morning
as southern Wisconsin will remain in the baroclinic zone between
upper troughing to the northeast and ridging to the south. It
won`t take much forcing to kick off more showers/storms in this
environment. Best rain chances are expected to be in northern
portions of the forecast area.
With the forecast area sitting within the temperature gradient,
will see highs Fri/Sat ranging from above normal southwest to
near or slightly below normal northeast.
SUNDAY THROUGH WEDNESDAY...Forecast Confidence...Medium
The 00Z ECMWF came in quite a bit different for the extended,
looking a bit more like the GFS now. The ECMWF is now not
developing a second upper low to the southwest by mid week as it
had been doing. Now, it pushes the first low east early in the
week faster than the GFS, bringing dry weather by Monday night.
Decided to linger pops into mid-week given the slower GFS and
previous ECMWF runs.
Trended temps cooler Monday through Wednesday given the ECMWF is
now cooler like the GFS. Forecast temps are still milder than the
coolest model solutions given the uncertainty and model
variability the last couple days. Overall though, looks like the
first fall-like temps of the season could arrive by mid-week.
Overall, expecting VFR conditions at the TAF sites through this
evening, or about 04z Fri. There are lingering chances of showers
and storms, but they should be focused mainly north and west of
Madison. The most uncertainty is around Madison where things could
become wetter than expected. Brief MVFR conditions are possible
around any stronger convection. Winds will remain light, generally
below 10kts. A cold front is expected to slip south of the area
this evening. The northeast winds in the wake of the front are
expected to bring IFR cigs across all of Wisconsin after about 04z
Fri. Those conditions could linger into Friday night.
Northeast winds are expected to develop tonight and
into Friday. Winds and waves are expected to remain below small
craft advisory levels, but conditions will be more elevated than
what we`ve seen over the past few days. Small craft may want to
WI...FLASH FLOOD WATCH until 7 PM CDT this evening for WIZ046-047-056-
TODAY/TONIGHT AND AVIATION/MARINE...Davis
Friday THROUGH Wednesday...DDV