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Office: MKX

FXUS63 KMKX 151128
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
528 AM CST Fri Dec 15 2017

.UPDATE...

The area of very light snow was moving across much of the area. A
dusting with a few tenths of fluffy snow. Mainly trace liquid
equivalent.

&&

.AVIATION(12Z TAFS)...

MVFR ceilings this morning. Very light snow/Flurries are expected
most areas, with a dusting as a mid level shortwave drops down.
Cigs should lift to VFR today most areas, with west winds
becoming gusty from mid morning through the afternoon hours. Look
for MVFR/IFR conditions late tonight as a band of light snow
drops in from the northwest. Best chance of accumulation snow
around 1 inch is north of madison and north of Milwaukee.

&&

.PREV DISCUSSION... (Issued 301 AM CST Fri Dec 15 2017)

SHORT TERM...

Today and Tonight...Forecast Confidence is Medium...

A fairly strong mid level trough will drop southeast across mainly
southeast Wisconsin from the northwest early this morning and off
to Lower Michigan by noon. Weak 700 mb upward motion should add to
the very light snow/flurries that will move across, with a
dusting north and east. Then a lull later morning south central
and across the area this afternoon. An upper level jet max then
pushes into Southern Wisconsin tonight, with the left front
quadrant expected to bring 700 mb upward motion and weak upper
divergence. This combined with a developing baroclinic zone,
should result in a band of light snow spreading northwest to
southeast later tonight. Most models point to north areas, but the
RAP is farther south with the max band. Even so only expected
around an inch of snow in the narrow band of max precipitation.

LONG TERM...

Saturday and Sunday...Forecast confidence is medium to high:

The snow will wind down Saturday morning, with a little lingering
precip far northeast in the afternoon. Another half inch or so is
possible in the northeast through the morning.

Kept a low chance of rain and snow going in the south Sunday
afternoon, though models seem to be trending drier for this
period.

Temps will likely be a few degrees above normal through the
weekend.

Monday through Thursday...Forecast confidence is medium:

Models show a little rain or snow Monday or Monday night as a
wave moves through the area. Kept precip chances on the low end
given fairly limited moisture and weak lift. Also, there are
enough differences among models to make it difficult to pin down
a period of higher pops.

It should be dry Tuesday into Wednesday per latest models showing
high pressure building in. Precip chances will then increase
Wednesday night into Thursday as a stronger low pressure system
is progged to move through the region. Models are in decent
agreement with the placement/timing of this low considering it's 6
days out. The model consensus brings the warm sector of the low
into the forecast area, with rain seeming more likely Wed night
into Thursday. Could see a transition to snow from northwest to
southeast Thursday night as the tail end of the precip moves
through. This looks like a decent snow maker for the region, so
will have to keep an eye on future model runs, as a shift south
would bring some of the higher amounts into the forecast area.

Temperatures are expected to be mainly above normal for Monday
through Thursday. Looking ahead...models are still suggesting
much colder temps then arriving for late week into the weekend
behind the departing low.

AVIATION(09Z TAFS)...

MVFR ceilings early this morning. Very light snow/Flurries are
expected most areas, with maybe a dusting as a mid level shortwave
drops down.

Cigs should lift to VFR today, with west winds becoming gusty
from mid morning through the afternoon hours. Look for MVFR/IFR
conditions late Friday night as a band of light snow drops in
from the northwest.

MARINE...

West winds will gust to Small Craft Levels mid morning into the
afternoon as low pressure moves across the upper Great Lakes. SCA
in effect from 6 am til 6 pm CST.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Small Craft Advisory until 6 PM CST this evening for LMZ643>646.

&&

$$

Update...Hentz
Today/Tonight and Aviation/Marine...Hentz
Saturday THROUGH Thursday...DDV



Office: ARX FXUS63 KARX 151118 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 518 AM CST Fri Dec 15 2017 .SHORT TERM...(Today and tonight) Issued at 320 AM CST Fri Dec 15 2017 12.09Z water vapor loop shows a short-wave moving through western WI, which has resulted in scattered flurries across much of the region early this morning. Northwest cyclonic flow and sufficient low-level moisture behind the wave will favor additional flurries for much of the day, especially this morning for areas along and west of the MS River. A strong northwest to southeast thermal gradient will bisect the forecast area today, resulting in highs ranging from the upper teens across north-central WI to the lower 30s across portions of northeast IA. Winds will generally be light from the west. For tonight into Saturday morning, increasing 850-700 hPa warm air advection on the leading edge of ridging aloft, combined with modest lift on the 285 to 295 K isentropic surfaces will result in a band of light snow developing for areas along and east of the MS River. Best chance for accumulations in the 1-2 inch range will be north of I-94 with less than a 1/2 inch southwestward to the MS River. Temperatures tonight will range from the single digits across north-central WI to the lower 20s across MN/IA into southwest WI. .LONG TERM...(Saturday through Thursday) Issued at 320 AM CST Fri Dec 15 2017 Some light snow will continue to accumulate Saturday morning north of I-94 before gradually tapering off into the afternoon. Forecast area remains within the low-mid level thermal gradient, but with ridging aloft, some warmer air will start to make its way into the area, especially south of I-90. Highs will climb into the lower 20s across the north to the upper 30s across the south. Flow aloft becomes quasi-zonal Sunday through Wednesday with the thermal gradient remaining near the forecast area. Primary impact to sensible weather will be near or above normal temperatures with daily highs generally in the 30s, but cannot rule out some spots across the south hitting 40 degrees. Dry conditions will be the general rule for most areas through mid-week, although some light precipitation is possible Sunday afternoon across northeast IA into southern WI as a weakening short-wave ejects northeastward from the Central Plains. Precipitation type will be dependent on near surface temperatures, but right now, rain looks more probable than snow. Could also see some light snow across the north Monday night with another passing short-wave. All eyes are on Thursday as both the GFS/ECMWF move a potent Eastern Pacific trough into the western CONUS, allowing flow aloft across the Upper Midwest to shift to the southwest. The GFS is 6-12 hours faster than the ECMWF, but both models bring a strong lee cyclone northeastward across IA and into southern WI. With ample moisture, a deformation precipitation band moves across the forecast area and at this time appears cold enough for snow. A LOT can change over the course of the next 7 days, so will need to monitor model trends to see if this idea holds or things change. && .AVIATION...(For the 12Z TAFS through 12Z Saturday morning) Issued at 518 AM CST Fri Dec 15 2017 Cold cyclonic flow aloft will continue to generate VFR/MVFR cloud cover today along with scattered snow flurries. Low pressure dropping southeast out of the Dakotas will produce some light snow tonight, but the bulk of this snow is expected to fall along and north of I-94, leaving mainly VFR conditions overnight at KRST/KLSE. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Rogers LONG TERM...Rogers AVIATION...DAS
Office: GRB FXUS63 KGRB 151145 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 545 AM CST Fri Dec 15 2017 Updated aviation portion for 12Z TAF issuance .SHORT TERM...Today...Tonight...and Saturday Issued at 358 AM CST Fri Dec 15 2017 Northwest upper flow will continue to produce mostly cloudy and seasonably cold weather across the region today and Saturday. Light snow produced by a surface and upper level trough should exit the area by midday, except for northcentral Wisconsin where some lake effect snow showers will continue. Partial clearing is possible in the east during the afternoon and evening. Jet energy rotating around the top of the ridge to our west will approach the region later tonight and early Saturday and should provide the upper support to produce some light snow. There is even a weak coupled jet structure and mid level frontogenesis that will help drive precipitation. An inch or two of fluffy snow is expected over all but the far north. The snow should lift north Saturday but diminish as the upper support exits the region. It could end as a little freezing drizzle as the mid level moisture departs but left it out for now. .LONG TERM...Saturday Night Through Thursday Issued at 358 AM CST Fri Dec 15 2017 The pronounced northwest flow pattern over the past week will flatten this weekend, allowing for temperatures to return to near normal on Saturday and then above normal early next week. Timing of upper level disturbances and associated precipitation chances still problematic at the beginning of the period. It now appears that a stronger storm will affect the area toward the end of the forecast period. For Saturday night, added or increased the chances of light snow Saturday evening across northeast Wisconsin as low level winds turn to the southeast. 925mb temperatues off the models would support some light snow shower activity off of Lake Michigan. What is interesting about the Saturday night period is that the GFS/WRF model are now indicating a surface trough across northeast Wisconsin which may increase low level convergence. If this scenario plays out, snow chances and snowfall amounts would need to be increased. After midnight, some of the models would suggest that the mid level moisture would scour out, so freezing drizzle would be possible after midnight. Did end any precipitation at 12z Sunday, but confidence in the end time is low. It is possible that the light snow or freezing drizzle could linger through much of Sunday morning. Yet another clipper system is expected to move across the region Monday night, bringing a chance of light snow to northern Wisconsin. Lake effect snow showers are possible Tuesday into Tuesday night. Attention then turns to a more significant storm that could bring a significant snowfall to portions of the area. The model runs tonight would suggest that the precipitation could be mixed across portions of the Fox Valley and lakeshore region. It is too far out to pinpoint the track of the storm and how much warm air would work into the area which could impact precipitation types and snowfall amounts. Stay tuned!. && .AVIATION...for 12Z TAF Issuance Issued at 544 AM CST Fri Dec 15 2017 variable conditions expected across the region through midday, with some snow showers and MVFR conditions in some places. Mostly VFR weather is expected this afternoon and evening, but lower clouds and light snow will arrive from south to north late tonight and early Saturday as an upper level disturbance moves across the area. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....RDM LONG TERM......Eckberg AVIATION.......RDM