Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
315 PM CDT Friday may 24 2013
Very short term...tonight and Saturday.
Short range models show high pressure slowly shifting east of the
area tonight and Saturday. Models are trying to bring the 850mb
focused warm air advection northeast into the southwestern portions
of the area this evening...then is shunted further to the southwest
later tonight. This area then gradually pushes back toward the
southwest portions of the area Saturday.
850mb low level jet nose focuses west of the area tonight...before
pointing more into central to northeast Iowa Saturday. Some
disagreement among the models with the placement of these 850mb
features...and subsequent quantitative precipitation forecast. European model (ecmwf) most aggressive with quantitative precipitation forecast across
the southwest half of the area tonight...with the others mainly dry.
The NAM is most aggressive Saturday in a similar area...with the
other models mainly dry.
Given the dry air lingering in the low levels with the high to the
east...will limit probability of precipitation to mainly the south central counties later
tonight and Saturday. Should see broken to overcast middle level clouds
spread across most of the area later tonight and Saturday. These
should limit lows tonight and limit highs on Saturday.
Short term...Saturday night through Monday.
12z NAM appears to be outlier with regards to more northern
placement of warm front and mesoscale-scale convective system over
central WI Sun night as baroclinic zone and enhanced low level
convergence likely to be further south and west. Never the
less...will continue to keep small probability of precipitation south and west of Madison Sat
night and sun due to nearby baroclinic zone. Better threat for
convection Sun night into Monday as northern extent of baroclinic
zones shifts northeast into the vicinity along with pieces of
upstream mesoscale convective system-induced vorticity moving northeast across southern WI.
Persistent southeast surface winds and plenty of clouds will keep temperatures
in check for the Holiday weekend.
Long term...Monday night through Friday.
Sharpening upstream long wave troffing over western Continental U.S. Is expected
early next week as vigorous piece of energy slides into base of
trough. This will result in increasing southerly middle level winds
which will contribute to the strong frontal boundary over the
central Continental U.S. Shifting northward. Medium range guidance in general
agreement however differences of timing of warm front progression
due to amount and areal extent of convection firing along and north
of front in baroclinic zone. By 00z/Wed...Gem and GFS has pushed
warm front into northern WI while European model (ecmwf) has front still suppressed to the
south. Best chance for more widespread convection along and ahead
of northward moving warm front during this period...hence highest chance
probability of precipitation Monday night into Tuesday.
Nearby convection vicinity of warm front could affect portions of southern WI
later periods...especially at night...as capping inversion should
prevent most daytime activity. More Summer-like temperatures and humidity
should settle in during this period as well. Later shifts may be
nuding maximum temperatures further into the 80s.
Threat for stronger convection late next week into the first days of
June as upper level trough moves northeast through the region.
&&
Aviation /00z tafs/...VFR conditions are expected tonight and
Saturday across taf sites. Any precipitation should remain southwest
of the area through this period...as high pressure slowly shifts to
the east. Should see broken to overcast middle level clouds shift
southeast into the area later tonight and linger into Saturday.
Northeast winds at the eastern taf sites late this afternoon will
weaken and shift southeast tonight into Saturday. Light winds will
become southeast tonight and Saturday at Madison.
&&
Marine...
Small Craft Advisory for high waves across the southern two
nearshore marine zones has been cancelled. Northeast winds will
continue to slowly diminish late this afternoon into the
evening...as high pressure slowly moves east. This has allowed any
remaining high waves to subside to under 4 feet.
&&
Mkx watches/warnings/advisories...
WI...none.
Lm...none.
&&
Confidence...
tonight and Saturday...medium to high.
Saturday night through Monday...medium.
Monday night through Wednesday...medium.
Thursday and Friday...low to medium.
$$
Very short term and aviation/marine...wood
short term/long term...mbk
