Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 260832
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
332 AM CDT Fri Apr 26 2019

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Saturday
Issued at 332 AM CDT Fri Apr 26 2019

A secondary cold front continues to sweep through the western
Great Lakes early this morning. Ahead of the front dew points in
the 40s are causing areas of fog, locally dense, across east-
central and northeast Wisconsin. Behind the front dew points have
fallen into the 20s as gusty northeasterly winds and the drier air
have scoured out the fog across central and north-central
Wisconsin. The front will cause the fog to clear in the next few
hours as winds turn northwesterly and become gusty. The gusty
winds will continue for the balance of the day, occasionally
gusting to around 30 mph at times as high pressure builds in
across the upper Mississippi Valley. Highs today behind the cold
front will only rise to around 50 across the north, with highs in
the middle to upper 50s across central and east-central Wisconsin.

The aforementioned high will drift through the western Great Lakes
region tonight, as temperatures fall into the 20s across the
north, with lower 30s across the south.

A low pressure system will then track through central Illinois on
Saturday, bringing a swath of snow through southern Wisconsin. The
arrival of the snow looks to be delayed from previous runs,
holding off until later Saturday morning across much of the area.
There is also some concern regarding the northern extent of the
precipitation as many of the models, especially the hi-res models,
keep much of the precipitation just to our south or right along
our border. This is due to a high pressure system just to the
north across southern Canada pumping dry air on northeasterly
winds across the northern Great Lakes. This dry air is problematic
as many models show the lowest levels of the atmosphere going
from fairly dry to wet bulbing below freezing with moderate snow
on Saturday. Also a concern is the time of day this system is
slated to move through. Since the bulk of the precipitation is
forecast during the daytime hours that would make it difficult to
keep surfaces cold enough for snow to stick as the sun would bring
incoming solar radiation to the surface, even through thick
clouds. The dry air in place and model inconsistencies do not give
much in the way of faith in the forecast for our area on Saturday
as there is a real chance the area could see little to no snow
accumulation. With that in mind tightened the POP gradient across
the area on Saturday and lowered QPF amounts a bit for the
forecast area given the southern trend of the models. Taking all
of this into consideration the current forecast only brings 1 to 2
inches of snow on Saturday, with a few locations possibly
approaching 3 south of a line from Wisconsin Rapids, to Waupaca,
to Manitowoc.

.LONG TERM...Saturday Night Through Thursday
Issued at 332 AM CDT Fri Apr 26 2019

Forecast concerns mainly revolve around precip chances early next
week. The upper air pattern will generally consist of troughing
across the northwest conus and ridging over the southeast conus. The
western Great Lakes will be between these features, with energy
ejecting out from the trough in the west to provide periods of
precip chances at times.  Once the storm system departs on Saturday
evening, the next period of precip is likely to occur during the
Sunday night through Monday night timeframe.  Medium range models
are in much better agreement with the details of the system, so will
use a blend of the ecmwf and gfs.  Will then give the edge to the
ecmwf for later periods.

Saturday night through Sunday night...Low pressure will be rapidly
departing the region across northern Indiana and Ohio on Saturday
night.  Light snow across central and east-central WI will be
exiting by mid-evening with little potential for additional
significant accumulations.  As the system exits, a very dry airmass
will return from late evening through the overnight resulting in
clearing skies.  High pressure will be centered across the region on
Sunday morning.  But as it rapidly moves to the east, will see
clouds return on Sunday afternoon and evening from the west ahead of
the next system.  Dry air will initially keep precip off to the west
on Sunday evening, but its looking like precip chances will arrive
overnight as pwat/moisture transport axis moves across the area. Web
bulb profiles over north-central WI suggest will see the majority of
precip fall as snow on Sunday night, with accumulations possible.
Highs on Sunday will return to the upper 40s and lower 50s.

Rest of the forecast...Widespread precipitation will likely continue
on Monday morning with moisture transport and isentropic ascent axis
over the area.  Thermal profiles warm over the course of the morning
across the northwoods, but not before more snow accumulations will
be possible.  Some indications that a few inches of accumulations
will be possible.  Dry slotting will push in from the southwest on
Monday afternoon, which will taper precip off to more of a drizzle.
Eventually though, the inverted trough weakens by late Monday night
or early Tuesday morning, which should end the light nuisant precip
at most locations.  After a period of dry weather, precip chances
will increase once again towards the Wednesday or Wednesday night
period and continue into Thursday.  Due to the clouds and periods of
precip, temperatures will likely remain below normal next week.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1034 PM CDT Thu Apr 25 2019

Some MVFR to possibly IFR visibilities are possible where rain has
fallen this evening; however, dry air will filter in from the west
overnight, which will help to improve visibilities. This will be
behind a secondary cold front that will slide through the area
overnight into Friday morning, leading to gusty northwest winds
throughout the day, especially during greater afternoon mixing.
Gusts will likely be in the 20 to 30 knot range Friday. The next
feature of concern will be a low pressure system sliding just to
the south of the area Saturday afternoon into Saturday evening.
This may bring a rain/snow mixture to the CWA/AUW/MTW/GRB/ATW TAF
sites, with the greatest chance being across the farther south TAF
sites. This may bring lower ceilings and visibilities; however,
this will depend on how far south the low treks. Dry high pressure
to the north will likely lead to a sharp cutoff in the
precipitation and cloud cover to the north.
&&

.HYDROLOGY...
Issued at 332 AM CDT Fri Apr 26 2019

Rivers and streams across northeast WI remain at high levels.
This includes high flows in and around area dams as excess water
is being released from earlier rainfall and snowmelt. The recent
rainfall should not impact current river levels much as only 0.25
to 0.40 inches of rain fell. Please monitor the latest river
forecasts for further information on flooding in your local area.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....Kurimski
LONG TERM......MPC
AVIATION.......Cooley
HYDROLOGY......Kurimski


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