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Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI
855 PM CDT Thursday Mar 26 2015

Update...
colder air continues to pour south across the area. The existing
cloud deck in the 3500-5000ft range is right in the thermal
dendrite zone. Couple that with a middle level trough moving overhead
and we have a radar lit up with lots of light returns...but it/S
enough to generate some flurries across the area. Very light stuff
though and not likely to accumulate. It/S a bit of different story
along the lake. There is a wind shift working down the
shoreline...going from north-northwest to north-northeast...offering a zone of low level
convergence within favorable fetch and Delta T/S for some light
lake effect snow possible. Any accumulations would be on the order
of a dusting to 1/2 inch and mainly on grassy surfaces. Pavement
temperatures will likely remain above freezing during the time
light snow is a threat.

Clearing is racing southeast out of central Wisconsin and will
likely reach Madison by midnight...but hold off at Milwaukee and
the rest of the southeast until about 3 or 4 am due to the lake
cloud potential with a north-northeast wind.

All in all...despite this winded discussion...not a whole lot
going on really. Temperatures will continue to fall into the teens
overnight.

&&

Aviation/06z tafs/...
clouds will continue to clear out of the area overnight. Madison
should be scattered by 06z Friday with kmke/kues/kenw clearing out
before sunrise. Some light lake effect snow is possible from kmke
south to kenw through about 2 to 3 am. VFR conditions are expected
through the taf period with winds out of the north-northeast.

&&

Marine...
a persistent and somewhat brisk north-northeast wind will bring large waves
and Small Craft Advisory conditions through Friday evening.

&&

Previous discussion... /issued 320 PM CDT Thursday Mar 26 2015/

Tonight...forecast confidence...medium

Cold advection continues with 925 mb cold pool bringing lows in the
teens tonight. Delta T/S and equilibrium levels of 5k to 6k feet
brings the potential of lake effect snow showers/flurries. At this
point going with any accums being under an inch and mainly south of
kmke to the WI/Illinois border. Cloud cover proggd to only slowly decrease
as the night wears on but will likely hang on longer especially in the east
with the lake contribution.

Friday...forecast confidence...medium

Cold advection with pronounced and very cold thermal trough in the
morning hours. Surface ridge axis will be slow to build in but
proggd to do so during the afternoon. 925 temperatures will be well below
zero celsius so a rather chilly day is in the works with temperatures well
below average with some highs remaining in the 20s.

Short term...Friday night through Saturday night - forecast
confidence...high

Good agreement in the models as high pressure looks to move into the
region late Friday night and early Saturday...keeping conditions
quiet but cold. Lows Saturday morning look to be in the lower to middle
teens. NAM soundings show a very dry airmass over the County Warning Area during
this time. Winds will be light and northeasterly Saturday...but
transition to a more southerly component due to the geostrophic
circulation as the high pressure moves off to the southeast late
Saturday.

Long term...Sunday through Monday - forecast confidence...medium

Early Sunday morning looks dry...but winds look to pick up ahead of
a cold front as pressure gradient tightens. The cold front looks
to swings through Sunday afternoon and evening and brings chances
of precipitation. Middle level support looks good for this system as
a 500 mb shortwave impulse...positive vorticity advection...and
good isentropic Omega will be present. Low levels will moisten
from the top-down through the morning hours...supporting this
precipitation. Additionally...decent 850 mb q-vector convergence
and frontogenetical forcing along the cold front will provide good
support for precipitation. P-type looks to be a light rain/snow mix
early...then transition to all light rain during the day. Models
are going pretty bullish with the quantitative precipitation forecast amounts...thus increased
probability of precipitation to likelies over the County Warning Area. Timing appears to be mainly between
12z Sunday and 00z Monday. The European model (ecmwf) has this precipitation finally
moving out after 06z Monday...while the other models have the
precipitation moved out by the afternoon and early evening hours.

Monday night through Thursday - forecast confidence...medium

There are some questions regarding a second system for late Monday
into Tuesday. The European model (ecmwf) is trending more with the GFS for a low
pressure system moving just to the north of our County Warning Area. Previous
European model (ecmwf) run had the low moving straight through our County Warning Area. Went with
slight chance probability of precipitation for now...with most of the precipitation being light
rain.

The European model (ecmwf) is progging a third system moving into the region
during the day Wednesday. There is some disagreement with the
timing of this event as the GFS does not have it arrive until late
Wednesday/early Thursday.

Aviation/00z tafs/...very chilly upper trough across the western
Great Lakes with 500 millibar temperatures around -30c. Kgrb 12z sounding
shows base of strong inversion around 800 millibars with moisture in
the 800-850 millibar layer. Some decrease in low level relative humidity noted tonight
though 500 millibar trough axis does not shift southeast of WI until after
12z Friday. Will keep shsn chances near kmke taf tonight with favorable
onshore flow developing for a time. High pressure builds in especially Friday
afternoon for a gradual decrease in northerly low level flow.

Marine...will issue a Small Craft Advisory from tonight into Friday
night as northerly produces favorable fetch for wave action. Things
settle down heading into Friday night as high pressure settles
across.

&&

Mkx watches/warnings/advisories...
WI...none.
Lm...Small Craft Advisory from 1 am Friday to 1 am CDT Saturday for
lmz643>646.

&&

$$

Update...Davis
tonight/Friday and aviation/marine...collar
Friday night through Thursday...jts

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