Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 270842
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
342 AM CDT FRI MAY 27 2016
TODAY AND TONIGHT - Confidence...Medium
Radar mosaic shows several weakening MCS`s to the south. This
weakening has allowed surge of moisture advection to begin spreading
northward. Short term guidance underestimating upstream low level
jet as vertical wind profiler network from WSR-88D showing 40-50kt
jet focused into central IA while IL on weaker eastern side of jet.
The combination of this surge and approaching mid-level jetlet
should carry at least scattered showers and storms across CWA this
morning. Column precipitable water is expected to increase to
around 1.25 to 1.5 inches this morning as this moisture streams nwd.
Low level jet re-energizes this aftn and eve ahead of low pressure
moving into the central plains and becoming slightly negatively
tilted. With deeper moisture in place and MUCapes anywhere from 500-
1500 j/kg, expect scattered to numerous showers and storms to
redevelop, especially over ern CWA. Mid level Lapse Rates only 5-6
degrees and bulk shear mostly in the 25-35kt range. More cloud
cover today should limit instability somewhat but isold severe not
out of the question, mainly later today. Will continue likely
wording into tonight due to nearby low level jet and continuing
surges of low level moisture flux convergence and lingering
Corfidi vectors show slow motion this afternoon and tonight as warm
cloud depth increases to 3-4km. However the Flash Flood Factor
expected to be weak. With PWAT values well above normal, expect
brief heavy rains to accompany t-storms but threat for flooding
looks low at this point.
SATURDAY THROUGH SUNDAY... Forecast confidence is medium.
The weakening upper trough will slide from eastern NE to Lake
Superior during this period. High precipitable water values and weak
instability will persist over southern WI on Saturday. Multiple weak
shortwaves will ripple through the area as well, but timing of these
are very uncertain. All of these factors support continued chances
for showers and thunderstorms in southern WI Sat and Sat night.
The surface low will be tracking through IA and MN on Sat, which
will allow for a tighter pressure gradient in southern WI and lead
to breezy south to southwest winds. Max temps should be around 80,
as long as we see some breaks in the clouds.
By Sunday morning, the main mid level trough will be along the MN/WI
border. The final wave of vorticity advection will bring southern WI
the best chance for showers/thunderstorms Sunday morning, with
chances tapering off from west to east in the afternoon. Winds will
shift to the west in the afternoon. Max temps on Sunday should be
around 80 once again.
Sunday night is the only dry period in the forecast at this time.
MEMORIAL DAY... Forecast confidence is medium.
The mid level flow will become zonal for Monday with possible
ridging per the ECMWF. Several models are showing a weak shortwave
rippling through southern WI, which could produce a few showers and
perhaps a rumble of thunder. Thus, kept the slight chance pops in
the forecast. Southern WI will still be in the mild air mass, so
expect temperatures in the lower 80s inland from the lake.
TUESDAY THROUGH FRIDAY... Forecast confidence is medium.
A closed upper low will make its way across the northern Plains
Monday night through Thursday. The ECMWF is most progressive with
this low which leads to precip timing differences. The occluding
surface low will likely bring showers and thunderstorms to southern
WI Tue and Wed. Then the GFS stalls the precip axis over WI for Thu
and Fri which leads to the slight chance pops in the forecast. The
ECMWF keeps southern WI dry during this period. Temperatures should
be in the upper 70s for much of next week.
Scattered showers and thunderstorms are expected today into
tonight as warm, more humid and unstable air surges northward into
the area. VFR cigs are expected for most of the period but will
briefly lower as some of these showers and storms affect taf
sites. Best chance for storms in eastern taf sites later today
into tonight. Mid-high clouds keeping fog at ba this morning.
Breezy west winds helped dissipate the dense fog over the
near shore waters Thursday afternoon. However today the winds will
be more south to southeast as warmer dewpoints in the low to mid 60s
surge northward over Lake Michigan. Hence expect more fog to
develop and likely to become dense for a time. Most susceptible
area is offshore from Ozaukee and Sheboygan counties where MODIS
images from Thursday showed cooler waters in these areas. Hence wl
be watching webcams of shore areas closely after sunrise.
Mariners will need to watch for scattered thunderstorms, especially
later this afternoon and evening. Gusty winds with these storms may
approach 35 kts, especially at the lakeshore.
Also, tighter pressure gradient south of warm front will allow gusty
south winds to affect lakeshore areas while winds remain less gusty
offshore due to steeper inversion beginning later tonight . Wind
gusts at the shore look to approach Small Craft Advisory levels late
tonight into Saturday.
TODAY/TONIGHT AND AVIATION/MARINE...MBK
Saturday THROUGH Thursday...MRC