Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
1057 am CDT Thursday may 23 2013
Aviation/18z tafs/...MVFR cloud deck gradually eroding from the
north...becoming scattered across SC WI. Southeast WI will have the clouds
linger quite a bit longer into the afternoon. Water vapor showing
upper cyclonic flow lingering today. Fairly tight pressure
gradient across the County Warning Area resulting in gusty north winds...highest
winds at eastern taf sites. Surface high will settle across
tonight easing the winds and clearing the skies off. The high will
dominate on Friday with a much lighter wind regime and plenty of
sunshine.
Pc
&&
Previous discussion... /issued 432 am CDT Thursday may 23 2013/
Today and tonight...forecast confidence is medium to high.
Upper low and rain showers to exit southern WI from northwest to southeast
throughout the morning with cold and dry air advection to follow.
The upper trough will shift into Michigan this afternoon and dig into
the eastern USA for tonight and Friday. Sunshine is expected by middle morning
over south central WI and early afternoon over far southeast WI. Forecast
soundings show good mixing well inland from the lake given the
drier airmass and full sunshine. Thus 925 mb temperatures around 8c and
850 mb temperatures around 2c yields highs around 60f over south central
WI. An onshore flow will keep high temperatures in the lower to middle 50s
near the lake.
Polar high pressure over the plains will then traverse to western WI
by 12z Sat. MOS guidance and 2 meter temperatures suggest low temperatures will
be middle to upper 30s with only patchy frost expected. No frost
advisory at this time.
Friday through Saturday night...forecast confidence is medium.
High pressure over the area Friday will bring quiet
weather...with a dry airmass per area forecast soundings from
NAM/GFS. Cool temperatures are near Lake Michigan with onshore
winds...with milder values inland.
Forecast gets more tricky for Friday night into Saturday
night...as models are in some disagreement with the placement of
precipitation across the region. The NAM continues to bring
showers and a few thunderstorms into the southwest half of the
area later Friday night into Saturday...lingering into Saturday
night. This is in response to focused 850mb warm air advection and
frontogenesis response over this area later Saturday into Saturday
night...as well as the 850mb low level jet pointing into the area.
GFS shows these features as well. 500mb ridge remains just west of
the area during this time.
Area forecast soundings from the NAM show saturation in the
southwest counties later Friday night...with the low to middle levels
remaining moist Saturday and Saturday night. GFS not nearly as
saturated over the area during this time. Not much elevated
instability is seen...so thunder risk seems to be on the low side.
The GFS/Canadian/ECMWF show lighter quantitative precipitation forecast in the southwest counties
Saturday morning. Kept lower end probability of precipitation in the southwest half of the
area for Friday night into Saturday. Temperatures will remain on
the cool side with onshore flow...especially near the lake.
More disagreement by Saturday night...as the NAM/GFS/Canadian
continue to bring quantitative precipitation forecast into the southwest half of counties...with
the European model (ecmwf) dry. Continued low probability of precipitation for the southwest 2/3 of the
area for now. Strength of high and dry easterly flow will
determine how far east the quantitative precipitation forecast comes into the area.
Sunday through Wednesday...forecast confidence is low.
GFS/European model (ecmwf) continues to show differences in this period. The GFS
continues to bring rounds of showers and a few thunderstorms
through the region Sunday through Monday...as low level warm air
advection zone remains over the region. The European model (ecmwf) keeps the area
dry during this time...as the influence of the high to the east
holds back any precipitation to the southwest. Onshore flow should
keep cool temperatures going...especially near the lake.
Both models do show a general warming trend by Wednesday...as warm
front pushes northeast through the region...and 500mb flow
gradually becomes west to southwest. GFS continues to be a bit
more aggressive with showers and storms near and north of the
front than the European model (ecmwf). For now...will lean towards the consensus
probability of precipitation and temperatures for Sunday through Wednesday.
Aviation/12z tafs/...occasional showers and ceilings from 1-2.5 kft
with areas of MVFR visibilities will end from northwest to southeast across southern WI this
morning. VFR conditions are expected at kmsn around 15z and around
17-18z at the southeast WI taf sites. Brisk and gusty northerly winds will
prevail the remainder of the day with clear skies and much lighter
winds tonight.
Marine...a Small Craft Advisory remains in effect today and tonight
for brisk and gusty northerly winds and very high waves of 6 to 10 feet.
Wind gusts could briefly reach gale force this am. High pressure
will settle over WI and Lake Michigan on Friday with much lighter winds
and smaller wave heights.
&&
Mkx watches/warnings/advisories...
WI...none.
Lm...Small Craft Advisory until 4 am CDT Friday for lmz644>646.
Small Craft Advisory until 1 am CDT Friday for lmz643.
&&
$$
Today/tonight and aviation/marine...gehring
Friday through Wednesday...wood
