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Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI
907 PM CDT Monday Aug 3 2015

Update...



&&

Aviation/06z tafs/...

VFR this period except MVFR/IFR fog possible mainly in the
Wisconsin River Valley until just after sunrise.

Model low level relative humidity has a good handle on cumulus/SC canopy wrapping
southeastward around Canadian vortex into northern/east central WI. Mainly
scattered cumulus around southern WI will diminish this evening with loss
of heating. However few clouds will remain.

Less wind on Tuesday with high pressure ridge drawing closer
resulting in a more lax gradient. Onshore winds may set up in the
afternoon with lake breeze potential. Scattered diurnal driven cumulus
development is expected once again with greatest coverage likely
in the NE 1/2 of the forecast area.

&&

Previous discussion... /issued 329 PM CDT Monday Aug 3 2015/

Tonight and Tuesday...forecast confidence is high.

Southern edge of broken cumulus/SC field may clip our far northern County Warning Area
before some diurnal dissipation takes hold. Overall little change
this period as broad northwest middle level cyclonic flow prevails.

Some cooler air aloft likely to result in at least more scattered cumulus
development on Tuesday with possible broken conditions...especially in NE
1/2 of the County Warning Area. 925 temperatures remain in about the 18-20c range so
similar highs expected. Airmass is overall to remain quite
parched. With surface ridge axis sliding across a lighter wind
regime will likely allow for the development of an onshore
component.

Short term...Tuesday night through Thursday...forecast confidence
is medium.

Models showing weak high pressure axis lingering across the area
Tuesday night...bringing quiet weather and cool temperatures. GFS
then shows a much different solution for Wednesday into Thursday
than the NAM/ECMWF/Canadian models. The GFS brings low pressure
east toward the region Wednesday into Wednesday night...then
across far northern Illinois Thursday. A 500 mb shortwave trough
accompanies this system Wednesday night through the area on the
GFS...with quantitative precipitation forecast Wednesday into Thursday.

The other models are dry during this time across the area...and
keep this system generally west or northwest of the region. Leaned
toward the drier models given the better agreement...and kept the
dry forecast going for Wednesday into Wednesday night. Kept low
probability of precipitation for Thursday...but think this period will end up dry with the
agreement among the drier models.

Mild temperatures in the upper 70s are expected inland...with
onshore winds keeping somewhat cooler values near the Lake.

Long term...Thursday night through Monday...forecast confidence
is medium.

European model (ecmwf) model is slower with the system than the GFS...delaying
passage through the region until Thursday night and lingering
early on Friday before exiting. This is the system the GFS has
coming through the region Wednesday night and Thursday. Leaned
toward the European model (ecmwf) timing and kept the consensus model blend of probability of precipitation
during this period.

GFS/European model (ecmwf) does have high pressure moving through the region over
the weekend...but kept the consensus probability of precipitation and temperatures given
differences in timing of various 500 mb shortwaves. This period
may end up dry if the high lingers in later model runs.

Aviation/00z tafs/...

VFR this period. Low level relative humidity forecasts have a good handle on cumulus/SC canopy
wrapping southeastward around Canadian vortex into northern/central WI.
Mainly scattered cumulus around southern WI will diminish this evening with loss of
heating. Gusty west-northwest winds will ease this evening.

Less wind on Tuesday with high pressure ridge drawing closer
resulting in a more lax gradient. Onshore winds may set up in the
afternoon with lake breeze potential. Scattered-broken diurnal driven cumulus
development is expected once again with greatest coverage likely
in NE 1/2 of the County Warning Area.

Marine...

Enough of a lingering pressure gradient and decent mixing has
resulted in marginal west-northwest gusts for a Small Craft Advisory. This
will be in effect until 7 PM...when peak mixing eases and gusts
drop below the wind criteria.

&&

Mkx watches/warnings/advisories...
WI...none.
Lm...none.
&&

$$

Update...hentz
tonight/Tuesday and aviation/marine...collar
Tuesday night through Monday...wood

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