Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
316 am CDT Thursday Jun 20 2013
Today and tonight...forecast confidence is medium.
We have heat and moisture returning to the area today...and there
appears to be some middle level altocumulus castellanus developing on satellite early
this morning confirming this is happening. Some Storm Prediction Center short range
hi resolution models want to try and develop some of this altocumulus castellanus
into showers or a thunderstorm today. But...the bulk of the
forcing with the warm air advection will stay west and north of
the County Warning Area through tonight. Just can/T see enough support in the way
of triggers and forcing across the area to justify precipitation over
most of the area today...and even tonight.
The surface ridge will be trying to hold on across the east while the
surface low is way out in the High Plains. Typically...any
activity would be held closer to the 800 mb jet and moisture axis. The
hires arw and nmm models are basically dry now through 12z
Friday...as well as the Canadian and European model (ecmwf) models. The NAM and GFS
want generate precipitation this afternoon...but this is most likely due
to the poor handling of the surface dew points which look too high. The
GFS has surface dew points climbing into the lower 70s this
afternoon...when lower 60s is probably more likely.
So will limit any precipitation chances to the western County Warning Area late this
afternoon into tonight...and keep the eastern 1/3 to 1/2 dry.
925mb temperatures support highs in the lower to middle 80s...though a
southeast wind will keep it cooler near Lake Michigan...especially
up toward the Sheboygan area. Temperatures won't fall very hard tonight
with the warm air pushing in.
Friday through Saturday night...forecast confidence is medium.
Short term models show gradual southwesterly 850mb warm air
advection and moisture advection into the region during this
period. The NAM and GFS keep the surface warm front north of the
area. The Canadian and European model (ecmwf) try to sag the warm front south into
the area Saturday into Saturday night.
The 850mb low level jet points mainly north of the area
Friday...but tries to focus more over southern/southwestern
Wisconsin Friday night into Saturday...mainly on the NAM/ECMWF. It
then points more to the northwest Saturday night. Tail end of
500mb vorticity maximum does shift east across the area
Friday...with more of these features passing northeastward through
the area at times Saturday into Saturday night.
Feel best chances for showers and storms will be later Friday
night into Saturday morning...with possible mesoscale convective
system fed by 850mb low level jet clipping the northern counties.
Otherwise...probability of precipitation will be more Chancy Friday and Saturday
night...as best upward vertical motion with warm front and low
level jet will be north of the area. Much of this period could
end up dry. If convection does occur...risk for heavy rainfall and
some large hail is there...with good amount of elevated cape and
high precipitable water values.
Thus...have highest probability of precipitation later Friday night into Saturday morning
across the northern counties. Chance probability of precipitation continue elsewhere for
this period. South winds will usher a warm and humid airmass into
the region during this time...with some highs approaching
90...especially if convection does not occur and more sunshine is
observed.
Sunday through Wednesday...forecast confidence is medium.
GFS/European model (ecmwf) continue to show some differences with features during
this period. Southwest flow at 500mb becomes more zonal Sunday
into Tuesday...with various vorticity maxima moving through the
region. Surface warm front does remain north of the area Sunday
into Tuesday as well. Southwesterly flow in the low levels will
continue to bring a warm and humid airmass into the region.
Timing and placement of quantitative precipitation forecast differs between the GFS and European model (ecmwf).
Again...some or most of this period could end up dry...with the
front north of the area. Main trigger would likely be any low
level jet nose interaction with the moist and unstable airmass.
Heavy rainfall would remain possible with higher end precipitable
water values. Used consensus probability of precipitation and temperatures for Sunday into
Tuesday.
More differences occur Tuesday night into Wednesday with timing
and placement of features between the GFS and European model (ecmwf). For
now...will continue use of consensus probability of precipitation and temperatures through
Wednesday.
&&
Aviation/12z tafs/...
VFR conditions expected through the period. Any thunderstorm
activity will be limited to the kmsn taf and that is a pretty
small chance beginning about 03z Friday and continuing into
Friday. Winds will be less than 10 knots.
&&
Mkx watches/warnings/advisories...
WI...none.
Lm...none.
&&
$$
Today/tonight and aviation/marine...Davis
Friday through Wednesday...wood
