Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 240230
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
930 PM CDT TUE AUG 23 2016
The HRRR has been consistent in pushing the MCS into the forecast
area from west to east tonight then exiting the southeast mid/late
Morning. New 00Z NAM is similar, just a little slower.
Influence of the upper shortwave and at least a portion of the
low level jet will arrive mainly after 06z tonight. So expect the
MCS crossing the Mississippi River to move across south central
and southeast Wisconsin. Look for MVFR cigs/vsbys in the
showers/Thunderstorms with some IFR during the early morning
hours. Appears that towards mid morning that precip should wind
down as the low level jet axis of shortwave shift east. Some
redevelopment possible Wednesday afternoon depending on where
sfc/850 millibar convergence and instability set up.
MARINE...A Small Craft Advisory (SCA) is now in effect from North
of Port Washington until Wednesday afternoon for breezy south
winds and waves of 4 to 6 feet. The winds and waves will decrease
some by late evening but increase again Wednesday.
BEACHES...South winds will generate high waves again Wednesday,
especially north of Port washington where a moderate rip current
threat is expected that will cause structural and longshore
currents. Thus dangerous swimming conditions will exist again
.PREV DISCUSSION... /Issued 327 PM CDT TUE AUG 23 2016/
TONIGHT - Confidence...Medium
A southerly flow along with a continuation of the drier low level
anticyclonic regime will gradually give way to more moisture and
better dynamics as the night wears on. The mid level ridge axis
will shift to our east and allow for a shortwave trough to arrive
later in the night. In addition, a portion of the 850 LLJ will veer
towards srn WI. This combo will result in shra/tsra moving into srn
WI after 06z. Seeing several hundred j/kg of elevated CAPE so
thunder seems likely, especially given the negative tilted nature of
the 500 millibar wave riding through. With the southerly flow
continuing and gradual uptick in moisture would expect temps to be
pretty close to the MOS numbers or in some cases a smidge above,
more towards the 3 hourly values.
WEDNESDAY - Confidence...Medium
Numerous shra/tsra likely ongoing during the early/mid morning hours
as mid level wave and LLj impact the area. The wave whisks off to
the east fairly quickly as the morning wears on so expect the
effects of subsidence to take hold, especially as influence of LLJ
peels off to the east as well. MOS and LLVL RH progs show an
abundance of cloud cover lingering. This and boundary implications
from the morning convection will have a say on how the setup unfolds
for the afternoon. The ML CAPE from the ECMWF nudges values up to
1000-1300 J/KG during the afternoon suggesting at least some breaks
taking shape. Mesoscale details will drive how the afternoon
scenario unfolds though mid level support holds off until after this
period. A much more humid day in the works as dew points expected to
be either side of 70.
WEDNESDAY NIGHT AND THURSDAY...Forecast Confidence Medium
Frontal passage has slowed from 24 hours ago as slow-moving closed
500 mb low opens up into a positively-tilted trough as it tracks
across far southern Canada just to the north of the northern Great
Lakes. Bulk of the ongoing showers and storms at the start of the
period shift southeast overnight with better 850 mb moisture
transport, but expect scattered to broken coverage showers and
storms overnight with frontogenetic forcing along the surface front.
00Z ECMWF and 12Z GFS develop a slightly stronger surface wave along
front ahead of a secondary 500 mb short wave that lifts across the
region Thursday morning, with QPF clipping far southern/southeastern
WI as mid-level moisture and 700 mb omega brush by the far south.
12Z NAM has a weaker surface wave and keeps pcpn just out of the far
south through the day Thursday.
Front finally drops far enough south for pcpn to clear for Thursday
afternoon. Will see highs around 80 as cold advection does not
kick in until Thursday night.
THURSDAY NIGHT AND FRIDAY...Forecast Confidence High
Mid-level subsidence and drying overspread region under confluent
500 mb flow. Looking for dry...cool weather as surface high pressure
slides across the region. Cold advection drops 925 mb temperatures
around 6C and they hold there through the day Friday. This will
yield slightly below normal temperatures with lows in the mid to
upper 50s away from the lake and around 60 lakeside, and mid-70
highs for Friday.
LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...Forecast Confidence
Next wave moves across the Dakotas Saturday, and lifts northeast
across the northern Great Lakes Sunday. Will back off precipitation
chances until after 06Z Saturday and then keep them over just the
western counties through 12Z Saturday where low-level jet and
moisture transport are just getting into the CWA. Focused warm
advection and forcing with the wave keep higher PoPs over the
western and northern CWA.
Will ignore the Canadian GEMNH that closes the wave off over MN and
slowly moves it to Lake Superior by 12Z Monday and trend towards a
blend of the the more progressive timing of the GFS and ECMWF, which
push the wave east of northern WI by late Sunday afternoon at the
latest. Still, there will be short wave energy and small chances of
showers in the busy zonal flow over the northern U.S. through the
remainder of the extended.
AVIATION/00Z TAFS/...Influence of low level anticyclonic flow
will persist into this evening with partly sunny skies. Precip
associated with upstream shortwave and low level moist axis will
remain to our west. Influence of the upper shortwave and at least a
portion of the LLJ will arrive mainly after 06z tonight. So expect
an uptick in shra/tsra activity associated with these features.
Appears that towards mid morning that precip should wind down as LLj
and axis of shortwave shift east. Some redevelopment possible
Wednesday afternoon depending on where sfc/850 millibar convergence
and instability set up.
MARINE...A Small Craft Advisory (SCA) is in effect from North Point
Lighthouse to Sheboygan until 10 pm for breezy sly winds and waves
of 3 to 5 feet. The winds and waves will decrease some by late
evening but again may reach SCA conditions for Wednesday afternoon.
BEACHES...A Beach Hazard Statement is in effect from Milwaukee
to Sheboygan until 10 pm. Sly winds will generate high waves that
will cause strong structural and longshore currents. Rip currents
will also be possible. Thus dangerous swimming conditions will exist
through this evening.
WI...BEACH HAZARDS STATEMENT until 10 PM CDT this evening for WIZ052-
LM...SMALL CRAFT ADVISORY until 3 PM CDT Wednesday for LMZ643.
TONIGHT/Wednesday AND AVIATION/MARINE...Collar
Wednesday NIGHT THROUGH Tuesday...REM