Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 190231
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
931 PM CDT Mon Mar 18 2024

.KEY MESSAGES...

- Polar airmass over the region for much of the week with the
  exception of a brief mild period on Tuesday.

- Snow accumulations are possible late Thursday through Thursday
  night. The next system develops Saturday night and continues
  through Sunday night.

&&

.UPDATE...
Issued 930 PM CDT Mon Mar 18 2024

No major changes to the forecast this evening. Mid-level clouds
associated with 850hPa WAA have begun to make their way into
southern Wisconsin which may keep low temperatures a few degrees warmer
overnight, especially in areas closer to central Wisconsin.
Otherwise, dry and windy conditions are still expected on
Tuesday.

Falkinham

&&

.SHORT TERM...
Issued 421 PM CDT Mon Mar 18 2024

Tonight through Wednesday:

Westerly winds will diminish into this evening before shifting
to southwesterly and increasing late tonight ahead of a low
pressure system progressing across southern Ontario late tonight
into Thursday morning. Expect lows in the upper 20s to near 30
degrees tonight. A brief period of cloud cover associated with
the initiation of WAA late tonight may keep temperatures
from falling into the 20s in central Wisconsin.

Tuesday morning, dry and gusty conditions are expected, with a
cold front draped south of the low pressure system progressing
through southern Wisconsin Tuesday afternoon and shifting winds
northwesterly. Generally expecting dry and windy conditions,
with dewpoint depressions as the main forecast challenge. A
pocket of subsiding moist air riding along the back side of the
exiting shortwave and mixing heights rising to near 5000 ft
ahead of the cold front may result in dewpoint temperatures
rising to the upper 20s. On the other hand, dewpoint
temperatures in the lower teens are expected to advect into the
area and may keep moisture levels lower than modeling indicates
during peak mixing hours. The main impact of this concern is the
relative humidity values falling into the 20 percent range if
dry conditions prevail, which could lead to fire weather
concerns. Expect high temperatures in the upper 40s to near 50
degrees.

Tuesday night, clear skies and northwesterly winds will lead to
lows in the lower 20s.

Wednesday, northwesterly winds and mixing heights up to 5000 ft
will bring in drier and cooler air, with highs in the mid-30s.
Relative humidity values may fall to near 20 percent in
southwestern Wisconsin.

MH

&&

.LONG TERM...
Issued 421 PM CDT Mon Mar 18 2024

Wednesday night through Monday:

After a quiet and cool Wednesday night and Thursday, the pattern
shifts to become more active Thursday night through the weekend.
The first system to keep an eye on is a CAA driven trough
propagating southward through southern Wisconsin Thursday night
into Friday. The GFS appears to be the outlier and produces a
closed low, leading to a deformation band and potentially higher
precipitation amounts. Meanwhile, the ECMWF and Canadian keep
the trough open with much less precipitation. For the time
being, confidence remains in accumulating snowfall during the
morning commute on Friday, with snow likely (70 to 90 percent
chance) throughout the overnight hours Thursday into early
Friday morning. Snow tapers off through Friday.

The next system in the long range develops Saturday, with model
discrepancy remaining quite high. GFS deepens the previous
system off the Gulf Stream and drags an arctic airmass into
Wisconsin ahead of the next system, leading to deep, cold air
and snow potential along the warm front. However, ECMWF and
Canadian favor a less intense Atlantic system and therefore less
cold air in place ahead of the warm frontal feature. This would
lead to more of a rainfall concern. All solutions remain
consistent with a blocking Greenland high, leading to a
persistent precipitation pattern through early next week.

MH

&&

.AVIATION...
Issued 930 PM CDT Mon Mar 18 2024

Mid-level ceilings around 10kft associated with WAA have begun
to make their way into southern Wisconsin this evening. These
clouds are expected to mostly dissipate by Tuesday morning, with diurnal
cumulus around 5kft then expected to develop Tuesday afternoon.
However, VFR conditions will prevail throughout the TAF period.

Low level wind shear is expected at MSN and JVL late tonight
into Tuesday morning as 850hPa winds of 40-45KT move through
southwestern Wisconsin. Gusty northwesterly winds of around 25KT
associated with boundary layer mixing of these higher wind
speeds and a cold front progressing through Wisconsin will
impact all sites on Tuesday. Winds will then decelerate Tuesday
night.

Falkinham

&&

.MARINE...
Issued 421 PM CDT Mon Mar 18 2024

Northwesterly winds will continue to slowly diminish through this
afternoon, shifting to become westerly this evening and increasing
overnight as high pressure builds southward into the Lower
Mississippi Valley and low pressure moves southeastward across
southern Ontario. A few gusts may approach gale force across the
southern half of the lake Tuesday morning. Winds will shift to
northwesterly Tuesday afternoon as an associated cold front
sinks southeast across the lake. A Small Craft Advisory is in
effect early Tuesday morning through Tuesday evening due to
elevated winds. Building high pressure in the northern Great
Plains may result in a few gales in the northern half of the
lake Wednesday as the low exits.

Winds will remain northwesterly through Wednesday, slowly
diminishing into Thursday.

MH

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...Gale Warning...LMZ080-LMZ673-LMZ675-LMZ777-LMZ779-LMZ874-
     LMZ876-LMZ878...4 AM Tuesday to 1 PM Tuesday.

     Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...4 AM
     Tuesday to 7 PM Tuesday.

&&

$$

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