Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
314 am CDT Tuesday Oct 21 2014
Today and tonight...forecast confidence is medium.
Low pressure over the eastern Great Lakes will continue to drift off
to the east while a Canadian high pressure ridge axis builds across
the western lakes. Northerly winds will bring low level cold
advection to the area and Delta T/S over the water will climb to
around 10c. Winds will also be turning northeast with time today and
all this complicates the main forecast challenge for today...cloud
cover. It/S still very extensive to the north and northeast...but
showing some holes to the northwest. It looks like the clouds will
hang in longer across the east than previously expected...possibly
into the late afternoon. The clearing line should slice through the
middle of the forecast area by middle to late morning. Some of the mesoscale
models produce some speckled very light quantitative precipitation forecast near the lake...but
Don/T believe it will be enough to measure. Will leave out any
precipitation mention at this time...but will keep an eye out over the lake
for any lake effect showers/sprinkles headed for the shore.
We should eventually see clearing for tonight with high pressure
overhead. Weather none with chilly temperatures.
Wednesday - confidence...medium
surface/850 ridge axes shift east. Middle level ridge axis right
across WI with large upper low in the far eastern US with trough
approaching from the plains. Lingering influence of the high
starts to wane in the afternoon as low level winds shift from an
easterly direction to more southerly. Moisture/dynamics
wise...things are still looking better to our west in the plains
closer to the advancing vorticity and low level trough.
Thursday and Thursday night - confidence...medium
upper dynamics approach along with lower level trough. Moisture
advection increases with time though 850 low level jet relatively weak.
Gem/NAM and European model (ecmwf) are all aggressive in bringing rain across County Warning Area
especially during the afternoon with the western County Warning Area having the better shot in the
morning. GFS has a drier look with little in the way of rainfall
reaching far eastern County Warning Area by 00z. So have boosted probability of precipitation across the
western and central County Warning Area and kept probability of precipitation lower in the far east to
account for potentially slower saturation with lingering dry air
though if European model (ecmwf)/NAM/Gem trends persist these probability of precipitation will need
boosting prior to 00z as well. With forcing shifting east during
Thursday night have trended probability of precipitation lower with time...though better
probability of precipitation in the east during the evening hours...as European model (ecmwf) shows
secondary upper wave riding southeast which may linger probability of precipitation a bit
longer in the eastern County Warning Area.
Friday through Sunday - confidence...medium
broad middle level ridging takes hold with a warming trend. The
mildest air per the GFS gets drawn northward for Sunday as low
pressure organizes with developing middle level trough pushing into
The Rockies. The GFS shows 925 temperatures warming to near 19c. Per
collab with surrounding offices...boosted the superblend temperatures a
bit for Sunday. Even the somewhat cooler European model (ecmwf) suggests that
inland highs may be too cool per the superblend.
Sunday night and Monday - confidence...low
models diverge with track of surface low evolving from the
western trough. The GFS takes a southern track with precipitation more
across central/southern WI with the low moving through southern WI on Monday.
Meanwhile the European model (ecmwf) has the low track further northwest with
little if any precipitation in southern WI and the warm wedge of 19c pushing
into southern WI Monday. Superblend takes into account the cooler
solution of the GFS but will be too cool and need boosting if
later runs support the European model (ecmwf).
Aviation/12z tafs/...winds will shift from north to northeast by middle
morning as a high pressure ridge builds south out of Canada. Low pressure
will be located over the eastern Great Lakes. Low level cold air advection
pushing down the lake will likely keep clouds locked in over the southeast
Wisconsin taf sets through middle to late afternoon. Look for the ceilings
to become MVFR between 12-15z this morning. Kmsn is more questionable
with respect to cloud cover. Ceilings should remain VFR and clear that area
by late morning...possibly earlier. VFR conditions are expected tonight
under quiet high pressure. There is some concern that the lower clouds
may hang on in the southeast into the evening...but will for now will
go with clearing skies by sunset.
Marine...persistent north then northeast winds will keep elevated
waves of 3 to 5 feet within the nearshore waters through this
Lm...Small Craft Advisory until 1 am CDT Wednesday for lmz643>646.
Today/tonight and aviation/marine...Davis
Wednesday through Monday...collar