Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 230203
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
903 PM CDT SUN MAY 22 2016
.UPDATE...Quiet weather to continue tonight as high pressure
ridge and dry weather persist over the area. Temperatures will
continue to fall through the 60s into the 50s. Minimum
temperatures appear to be in good shape. Increasing boundary layer
mixing should keep overnight temperatures slightly warmer away
from the lake compared to last night.
.AVIATION/06Z TAFS/...VFR conditions are expected through the TAF
period. Look for southerly winds to strengthen during the day
Monday, with gusts up to 15 kts possible, and perhaps up to 20 kts
near MSN. Showers and thunderstorms will hold off until late
Monday night or Tuesday.
.MARINE...Light and variable winds will become more southeast
overnight as surface high pressure ridge axis slides slowly east.
Will need to start considering whether fog may develop over the
near shore waters later on Tuesday and Wednesday as warmer, more
humid air settles in from the west. Too much uncertainty at this
point to include in forecast.
.PREV DISCUSSION... /Issued 303 PM CDT SUN MAY 22 2016/
TONIGHT AND MONDAY...Forecast confidence is high.
High pressure will drift across the Great Lakes region tonight and
Monday. Winds shifting to the south this evening will increase into
the 10 to 20 mph range Monday morning.
Decent radiational cooling once again will give us low temperatures
in the lower 50s tonight with spotty lower temps like last night.
The 925mb temps topped out around 20C today and will be the same
tomorrow. Therefore, high temperatures will be similar to the highs
today, but a little warmer near the lake with a delayed easterly
Monday night and Tuesday...Forecast Confidence...High
The upper ridge remains over eastern Wisconsin through Monday
evening before the mid/upper level flow becomes southwest, with a
subtle weak 500 mb shortwave pushing across 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, and the far southeast Tuesday afternoon. The Tuesday
afternoon lift may be due to some convective feedback. 700 mb rh
increases a little, but does not saturate. 850 mb rh and moisture
is higher as the southwest flow at 850 mb increases to 40 knots
over south central Wisconsin monday night and to 30s knots over
the southeast Tuesday morning, decreasing to around 25 knots
across the area Tuesday afternoon.
The 12z GFS is slow to push showers into the area during the
evening, but is now a little faster spreading across all of south
central Wisconsin after midnight. The 00Z ECMWF is dry across the
area Monday night. Both the GFS and ECMWF spread precipitation
across the forecast area Tuesday. The GFS has somewhat heavier
rains. The zero to 6 km shear is rather weak around 15 to 20
knots. The severe parameter CWASP increases to around 70 on the
GFS, but is only around 55 to 60 on the ECMWF and NAM. The GFS
forecast sounding at the Sullivan Forecast office has zero to 1 km
cape values increasing to 1200 joules/kg during the afternoon,
with only a weak cap around 850 mb. The severe parameters do get
into the marginal Severe category with unidirectional shear. Hail
would likely be the primary threat.
TUESDAY night AND WEDNESDAY...Forecast Confidence...Medium
The southwest mid/upper level flow becomes a little more zonal as
a 250 mb speed max moves across the Upper Great Lakes.
The GFS is now dropping a surface boundary to the south by
Wednesday while the boundary is more north and diffuse on the
ECMWF. The ECMWF brings more showers and thunderstorms for
Wednesday, while the GFS tends to dry things out with the more
stable low level air. The severe parameter CWASP increases to
around 72 wednesday on the ECMWF, but is lower on the GFS at
around 60. The GFS forecast sounding at the Sullivan Forecast
office has zero to 1 km cape values increasing to 1000 joules/kg
during the afternoon, with a weak cap just below 850 mb. The
severe parameters do manage to get into the marginal Severe
category, but thunderstorms are more questionable on the GFS with
the surface boundary to the south.
Wednesday night and Thursday...Forecast Confidence...Medium
A west southwest upper flow extends across southern Wisconsin
ahead of the main trough over the southern Rockies.
The GFS tries to lift the surface boundary back north late
Wednesday night and Thursday with more showers and thunderstorms.
The ECMWF dries things out Thursday.
The severe parameter CWASP increases to around 75 wednesday on
the GFS, but is lower on the ECMWF at around 50.
Both the GFS and ECMWF now exits the upper trough over the
southern rockies and moves it into the Central Plains with a more
southwest upper flow into southern Wisconsin.
The GFS brings showers and thunderstorms into the forecast area,
while the ECMWF has a more northern focus.
With a more southwest return flow the severe parameter CWASP
increases to around 70 to 80 on the GFS, but is lower on the ECMWF
at around 55.
Saturday and Sunday...Forecast Confidence...Medium
The shortwave lifts northeast into the upper Mississippi Valley
Saturday and across the Upper Great Lakes Monday.
The surface low stays well west as it lifts across the plains.
both models bring mainly light precipitation Saturday and into
VFR conditions are expected through the TAF period. Look for
southerly winds to increase through the day Monday. Showers and
thunderstorms will hold off until late Monday night or Tuesday.
High pressure will keep winds light and wave heights low through
tonight. Southerly winds and waves will increase a bit later Monday
and into Tuesday ahead of an approaching trough of low pressure.
Small craft advisory conditions are not anticipated at this time.
TONIGHT/Monday AND AVIATION/MARINE...MRC
Monday NIGHT THROUGH Sunday...Hentz