Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 211955
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
255 PM CDT SAT MAY 21 2016
.TONIGHT AND SUNDAY...Forecast confidence is high.
A high amplitude ridge will drift across the Upper Midwest. Very dry
air in place will allow for clear skies tonight and decent
radiational cooling. Min temps will be a bit warmer than last night
given warmer 925mb temps... ranging from the upper 40s to lower 50s.
Sunday will be another very pleasant day with very few clouds. Winds
will be light and variable. A lake breeze will keep temps near the
lake cooler, but they should be able to get into the mid 70s.
Lakeshore temps reached the lower 70s today with a steady east wind
all day. Inland temps will be in the 80 to 83 degree range.
.Sunday Night and Monday...Forecast Confidence...High
The GFS is slightly slower with the upper ridge moving into
Wisconsin. The 700 mb upward motion now stays just to the west of
South Central Wisconsin Monday afternoon with only a modest
increase in 700 mb rh. The forecast soundings are very dry in the
mid levels with little increase in low level moisture, and a
rather weak cap above the mixed layer which reaches up to 860 mb.
The south 925/850 flow leads to further warming across southern
Both the GFS and 00z ecmwf keep any precipitation off to the west.
.monday night and tuesday...Forecast Confidence...High
The upper ridge remains over eastern Wisconsin through Monday
night before the mid/upper level flow becomes southwest, with a
subtle weak 500 mb shortwave pushing into Southern Wisconsin
Tuesday. Upper level divergence and 700 mb upward motion begins,
but is weak, except for moderate lift brushing the dells area
Monday night. 700 mb rh increases a little, but is not close to
saturating. 850 mb rh and moisture does increase with saturation
mainly over south central Wisconsin Tuesday as the southwest flow
at 850 mb increases to 25 to 30 knots.
The 12z GFS is slow to push showers into the area, with some
precipitation after midnight, especially northwest of Madison.
The 00Z ECMWF does bring precipitation across Tuesday, but it is
light. The GFS is mainly dry Tuesday. Both models keep the cold
front to the west. The severe parameter CWASP increases to 65 to
around 70 Tuesday west of Madison. The GFS forecast sounding at
Madison has zero to 1 km cape values increasing to 1900 joules/kg
late afternoon, but there is an increasing cap around 850 mb. The
supercell index does increase to 5.3 with the sounding indicating
a severe watch type potential.
.TUESDAY night AND WEDNESDAY...Forecast Confidence...Medium
The southwest mid/upper level flow continues, with a shortwave
moving across Wisconsin Wednesday. The shortwave is a little
stronger on the ECMWF.
The GFS is trending a little more toward the ECMWF in moving a
surface low towards Iowa and into Wisconsin. The Ecmwf is
just a little stronger and faster with the low. The GFS is a
little faster bringing showers and thunderstorms with the
weakening surface trough and cold front Tuesday night and into
Wednesday. Since the ecmwf is slower with the onset of convection
the severe parameter CWASP increases to around 76 wednesday on
the ECMWF, but is weaker on the GFS as the convection is exiting
A somewhat stronger shortwave moves across Wisconsin on the gfs
thursday with the southwest upper flow continuing.
The ECMWF dries things out Thursday, while the GFS still has
showers and thunderstorms.
Both the GFS and ecmwf now take a shortwave across the southern
The models try to build a weak ridge into Wisconsin.
The shortwave lifts northeast into the central plains on the GFS but
is faster and farther north on the ECMWF with southern Wisconsin
still in a southwest flow aloft.
This again brings a round of showers and thunderstorms back
Friday night on the faster ecmwf and on Saturday on the GFS.
VFR conditions are expected through the TAF period. Winds will
generally be at or below 10 kts. Some scattered high-based diurnal
cumulus clouds are expected again Sunday afternoon.
High pressure will keep winds light and wave heights low through the
weekend, with southerly winds and waves increasing later Monday
and into Tuesday ahead of an approaching trough of low pressure.
TONIGHT/Sunday AND AVIATION/MARINE...MRC
Sunday NIGHT THROUGH Saturday...Hentz