Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 111916

Area Forecast Discussion
National Weather Service Green Bay WI
216 PM CDT Sun Mar 11 2018

Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Monday
Issued at 215 PM CDT Sun Mar 11 2018

The main forecast concern to be on extent of precipitation,
especially for later tonight through Monday, as a cold front and
shortwave trough move through the region.

The 19z MSAS surface analysis showed an area of high pressure over
the central and eastern sections of the Great Lakes region. A cold
front extended from central Ontario southwest to near Minneapolis.
Radar mosaic has been picking up on some sprinkles or flurries
over the MN arrowhead in the vicinity of the cold front.

A shortwave trough is forecast to drop south-southeast from
Ontario into Lower MI tonight. While there is a weak surface
reflection shown by the models, the main lift and forcing are
aloft in the form of a mid-level shortwave and upper-level jet
streak. Winds will also turn northwest later this evening through
the overnight hours as the cold front moves through the area.
These northwest winds, coupled with modest CAA, will add lake
enhancement to the synoptic snow chances across north-central WI.
Based on the location of the strongest forcing, may need to
continue a chance of snow showers/flurries across eastern WI
through most of the night. Central WI appears to be spared any
snow of consequence and remain mostly cloudy through the night.
Plenty of clouds will prevent temperatures from falling anywhere
as cold as previous nights. Look for min temperatures to range
from the lower 20s north-central WI, to the upper 30s across
east-central WI.

The lake effect snow showers would continue through Monday with
favorable trajectories (north-northwest), albeit any accumulations
would be minimal since much of western Lake Superior still has
ice. Otherwise, there is still some concern for convective
development Monday afternoon as low-level lapse rates steepen and
another shortwave moves southeast into Lower MI. Would not be
surprised to see at least some rain and/or snow showers over most
of the forecast area, but any precipitation would be scattered at
best and brief at that. A decent amount of clouds will limit
diurnal warming and prefer the cooler side of guidance. Therefore,
max temperatures to range from the lower 30s north-central, upper
30s to around 40 degrees elsewhere (slightly cooler near Lake MI).

.LONG TERM...Monday Night Through Sunday
Issued at 215 PM CDT Sun Mar 11 2018

Despite a lack of deep moisture, a fairly substantial mid-level
PV anomaly will track through the western Great Lakes Monday night
as the area remains under cyclonic flow. This should be enough to
produce light snow showers and or flurries during the overnight
hours. A push of cold air on Tuesday and continued cyclonic flow
will continue light snow showers across the north with assistance
from Lake Superior, with flurries elsewhere. MAV guidance on
Tuesday is too warm as 850 mb temperatures are solidly in the
middle teens below zero. Therefore will side with the cooler
guidance with expected highs from the middle 20s to around 30.

High pressure will then dominate the region during the middle part
of the week, bringing dry weather to the western Great Lakes as
temperatures moderate back to the 40s.

Precipitation chances will then return by the end of the week as
a low pressure system tracks through the western Great Lakes
region. NWP models are not in agreement regarding the timing of
this system, therefore POPs and confidence remain low this far
out. Once this system exits by Saturday, another one is forecast
to take aim for the region on Sunday. Just like the system on
Friday, this one is fairly low confidence given the differing
solutions offered by the models this far out.

.AVIATION...for 18Z TAF Issuance
Issued at 1236 PM CDT Sun Mar 11 2018

Low-end VFR cigs to persist across central WI this afternoon,
while only mid-clouds are expected over eastern WI. The
combination of an approaching cold front, mid-level shortwave
trough and upper-level jet streak will push into the Great Lakes
starting this evening with cigs dropping to MVFR over central WI
this evening and eastern WI after midnight. There will be a chance
for light snow showers or flurries north and east tonight as these
weather features provide enough lift and forcing. Furthermore, a
wind switch to the northwest may bring some lake enhancement into
north-central WI. The lake effect snow showers will continue
across north-central WI on Monday. Elsewhere, the warming March
sun will combine with a cool pool of air aloft to bring at least
some sprinkles or flurries to much of the area, especially during
the afternoon. There could be a few snow or rain showers around as
well. Cigs are forecast to be high-end MVFR or low-end VFR through
much of Monday.



SHORT TERM.....Kallas
LONG TERM......Kurimski
AVIATION.......Kallas is the U.S. government's official web portal to all federal, state and local government web resources and services.