Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 271208
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
708 AM CDT Thu Apr 27 2017
.AVIATION(12Z TAFS)...The rain will end by late morning or early
afternoon. Some snow may mix with the rain mainly north and west
of Madison. Areas of MVFR Vsbys with the precip. this morning.
Cigs will range from 600-2000 ft this morning transitioning to
3.5 kft by late afternoon, then clearing.
.PREV DISCUSSION... (Issued 353 AM CDT Thu Apr 27 2017)
Today and Tonight...Forecast Confidence is high.
Cyclogenesis is underway from far SE WI to an ern LS by early
afternoon. Rainfall rates have been light throughout the night but
moderate rainfall will now push through the area through about 16z
as the negative tilt upper wave moves into srn WI. Cold advection
and the approach of the upper wave may result in a mixture of
rain and snow beginning around 13-14Z mainly north and west of
Madison. Brisk wly winds will develop in the wake of the low
pressure area with gradual drying and subsidence bringing some
clearing to the region tnt. A col will settle over srn WI late tnt
with cool temps and frost expected.
Friday... Forecast confidence is medium.
Rain chances increase across southern WI through Fri afternoon as
a low level jet (LLJ) points into the WI/IL border and the low
level front pivots over the area with the approach of a mid level
wave. This is a brief period of forcing for rain that tapers off
from west to east through Fri evening. The ECWMF keeps southern WI
nearly dry for this period while the other models produce precip.
Friday night is looking cold with decreasing clouds over central
WI. Low temps should drop into the mid 30s for northern portions
of the MKX forecast area. This means patchy frost will be a
Saturday through Sunday night... Forecast confidence is medium.
There is a pretty good chance for dry, raw weather across
southern WI for much of Saturday. We need to wait for the next mid
level wave to reach the area for the rain. The ECMWF is the one
model that spreads precip into southern WI during the afternoon,
but the majority of the precip remains south of the WI/IL border. Brisk
east winds and clouds will keep temperatures cool, with highs in
the mid 40s near the lake and lower 50s inland.
By Saturday evening, the LLJ will nose into southern WI, along
with the 850mb warm front and mid level shortwave. This strong
forcing will bring a round of moderate rain. Elevated
thunderstorms will be possible. Winds will remain steady and
strong out of the northeast since we will remain on the north
side of the surface front.
The stronger forcing will be split to the east and west of
southern WI on Sunday, but elevated instability and ample moisture
will lead to off and on showers and thunderstorms throughout the
day, along with continued gusty northeast winds.
Sunday night will bring another round of moderate rain and
scattered thunderstorms. This is the time where the upper low gets
into the Midwest, along with the surface occluded front.
Monday through Tuesday... Forecast confidence is medium.
The dry slot should track through southeast WI on Monday and bring
a break in the rain, but brisk westerly winds. The wrap-around
region of the occluded system is expected to swing across southern
WI Monday afternoon. 850mb temps will be falling below freezing,
so some snow mixed into the rain is not out of the question for
Mon afternoon/evening before the system moves out.
Quiet and slightly warmer weather will return to southern WI on
Tuesday as that system gets out of the region. The next chance for
rain looks like it will hold off until Thu night.
The IFR stratus over south central Wisconsin will persist through
this morning, before rising to VFR by late afternoon. Westerly
wind gusts of 20 to 25 knots are forecast for this afternoon,
especially in southeastern WI.
Look for the moderate rain showers to move northeast out of the
area during the late morning.
A Small Craft Advisory is in effect from 14z-00z today
for brisk wly winds. Variable Winds early this morning will become
brisk wly by 9 AM as low pressure tracks northward along the
western shore of Lake MI. Wind gusts will range from 25-30 kts.
Winds will weaken after sunset.
LM...Small Craft Advisory until 7 PM CDT this evening for LMZ643>646.
Today/Tonight and Aviation/Marine...Gehring
Friday THROUGH Wednesday...Cronce