Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 012145
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
345 PM CST Wed Mar 1 2017
.TONIGHT...Forecast Confidence Is High.
A shortwave trough will eject from the western Great Lakes into
New England, with cyclonic flow persisting aloft. Areas of light
to moderate snow this afternoon will taper off this evening, as
the upper support with the mid/upper wave wanes. We`ll see
additional chances for some light snow or flurries late tonight,
as warm advection precedes a weak mid-level wave dropping down
from the northern Great Plains. Any accumulations should be quite
minor. Lows tonight will fall well below freezing, so slippery
conditions will develop on untreated roadways.
Given the current band of moderate snow producing visibilities of
around 1/2 mile, decided to expand the Winter Weather Advisory
into our southeast areas ahead of it. While additional snow totals
shouldn`t be significant, decided this would be a prudent option
given that rush hour is now underway.
.THURSDAY THROUGH SATURDAY...Forecast Confidence Is Medium.
The main feature of interest for Thursday will be a 500 mb
vorticity maximum that is expected to slide southeast across
southern Minnesota, Iowa and into northern Illinois. The models
are in decent agreement with the timing and placement of this
feature. The resultant differential cyclonic vorticity advection
clips southwest Wisconsin Thursday afternoon. Modest mid level
frontogenesis response passes across southwest Wisconsin as well.
There is fairly deep moisture in the air column in the dendrite
snow growth zone in this area, and is somewhat drier to the
However, the models have trended drier with the QPF. The 18Z NAM
is now keeping the area dry Thursday, similar to the 12Z Canadian.
The 12Z GFS keeps light QPF in the area, with the 12Z ECMWF only
showing very light amounts. Thus, backed off a bit with PoPs for
Thursday into Thursday evening, and these may need more reduction
if later model runs continue their drier trend.
High pressure then moves southeast through the region for later
Thursday night into Friday, bringing quiet weather.
Another 500 mb vorticity maximum and some low to mid level
frontogenesis response again pass southeastward close to or over
southwest Wisconsin Friday night. This may bring another round of
light snow to the area. All models show light QPF across the area.
Thus, kept PoPs going for mainly Friday night.
.SATURDAY NIGHT THROUGH WEDNESDAY...Forecast Confidence Is Medium.
Saturday night into Monday night looks to be a warmer period across
the area, with steady warm air advection pushing into the region.
Temperatures should gradually rise above seasonal normals as a
Increasing moistures advection into the region Monday into Tuesday
should help bring increasing chances for showers and perhaps a
few thunderstorms early next week. The passing cold front Monday
night should help with upward vertical motion, and bring somewhat
cooler temperatures for later in the week.
Periods of light snow will bring a mix of MVFR and IFR ceilings
and visibilities into this evening. Conditions should improve to
prevailing VFR for most areas later tonight. We`ll see occasional
wind gusts to around 20 knots into this evening, before winds
decrease. There is a slight chance for flurries tonight west of
Madison, with another chance for light snow Thursday afternoon.
Any accumulations would be very light.
Gusty northwest winds will persist for the nearshore waters into
early tonight, and a Small Craft Advisory remains in effect until
4 AM. Thereafter, expect subsiding winds and waves to remain below
Small Craft levels on Thursday.
WI...Winter Weather Advisory until 6 PM CST this evening for WIZ046-
LM...Small Craft Advisory until 4 AM CST Thursday for LMZ643>646.
TONIGHT AND AVIATION/MARINE...SPM
Thursday THROUGH Wednesday...Wood