Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
1005 PM CDT Wednesday may 22 2013
Update...
The middle level low over northeast Iowa will move southeast. The
showers will continue overnight. A windshift extends from near
Mineral Point to Janesville. Showers and storms were occurring just
north of the boundary...but will loss of heating these showers
have diminished a little so mainly moderate rains expected.
As the upper trough pushes southeast...the area of showers will
also move slowly south along with the boundary.
&&
Aviation/06z tafs/...
IFR/LIFR ceilings mainly north a a boundary from Mineral Point to
Janesville. As this boundary pushes south the moist northeast low
level flow will bring the IFR/LIFR south.
Expect drying Thursday afternoon when ceilings will rise to VFR from
the north.
&&
Previous discussion... /issued 301 PM CDT Wednesday may 22 2013/
Thursday night and Friday...forecast confidence is high.
Canadian high pressure will settle over the area. Temperatures Thursday
night will drop into the 30s most places with the coldest readings
along The Kettle Moraine spine in southeast Wisconsin. We could
see some patchy frost in that area.
Friday looks sunny with temperatures just a few degrees below
normal. Areas near Lake Michigan will be much cooler due to the
expected easterly wind.
Friday night and Saturday...forcast confidence is medium.
The ridge begins to drift east by Friday night. A surge of warm
advection will try to bring in some thunderstorms across the west
after midnight continuing into Saturday. The NAM is very
aggressive with this...both in quantitative precipitation forecast and eastward extent...while
the GFS/ECMWF/Gem are slower and also keeping it farther west.
The consensus approach looks reasonable and only brings a chance
for showers and thunderstorms to the southwest half of the
forecast area...mainly southwest of Madison. As the associated
low level jet weakens on Saturday...this should help to diminish
any lingering precipitation by Saturday afternoon.
Sunday through early next week...forecast confidence low to medium.
We will be in a rather steady...unchanging pattern during this
period. High pressure will be holding over the Great Lakes while
low pressure holds over the Central Plains. Aloft...the right
rear quadrant of the upper jet will be hovering over the
area...providing a rather sustained area of upper divergence/upward vertical velocity
over the County Warning Area. At the same time...in the lower levels...the low
level jet will be persistent...stretching from Kansas...Missouri
into Iowa. We could see upper level ridge riding showers and
storms roll in from the northwest from time to time...mainly
across the SW forecast area. While our northeast forecast area
could remain dry...protected from the drier airmass with the high
pressure system. It is difficult at this point to know just where
this pattern will lock in. Drier and cooler air from the east
will be competing with more moist air trying to push in from the
west. This explains the rather extended period of chcy rain in the
forecast.
Aviation/00z tafs/...as upper low opens up and progresses a bit
quicker eastward from Iowa...MVFR ceilings will become prevalent.
Some IFR ceilings too are expected especially with any rain showers. Gusty
northeast winds will start increasing after 6z. These gusty winds
will persist for much of Thursday especially at the eastern taf
sites.
Marine...as surface trough axis slides southeast overnight gusty
northeast winds will increase with cold advection. Decent fetch will
lead to some high wave action. Close call on the gale potential
Thursday but for now elected to keep the Small Craft Advisory in
place.
&&
Mkx watches/warnings/advisories...
WI...none.
Lm...Small Craft Advisory from 4 am Thursday to 4 am CDT Friday for
lmz644>646.
Small Craft Advisory from 1 am Thursday to 1 am CDT Friday for
lmz643.
&&
$$
Update...hentz
tonight/Thursday and aviation/marine...collar
Thursday night through Wednesday...Davis
