Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 201744
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1244 PM CDT Mon Mar 20 2017

Updated aviation portion for 18Z TAF issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 246 AM CDT Mon Mar 20 2017

Other than high clouds streaming across the western Great Lakes,
the weather was relatively quiet across northeast Wisconsin early
this morning. A disturbance around 700 mb, noted on reflectivity
along the border of North Dakota and South Dakota, will track
through the area this afternoon. The best proxy for this
disturbance appears to be the 850-700 hPa RH field. Given the
light rain tracking through upstream will introduce a small chance
for rain for the area as this feature tracks through this
afternoon. Highs today will be fairly warm, generally from the mid
to upper 40s across the north, with lower to middle 50s across the
south.

Tonight should be mostly clear as a cold front pushes through the
area during the overnight hours. Although the front will lack much
in the way of precipitation, it will pack a fairly potent punch in
the temperature department as 850 hPa temperatures fall a good 10
degrees from today to Tuesday. This cold air and mostly clear
skies should push lows tonight lower than previously expected.
There appears to be a discrepancy with how much lower as the MET
MOS numbers are much lower than the MAV or ECS numbers would
suggest. Given the late arrival of the cold air will side with the
warmer MOS numbers and lower mins tonight several degrees to the
upper teens across the far north, with middle to upper 20s across
the south.

Temperatures on Tuesday will be cooler, but still near normal for
this time of year with highs ranging from the 30s across the
north, with lower to middle 40s across the south. Other than some
lake effect activity across Vilas County, dry weather is expected
for much of the area on Tuesday with very dry RH values noted on
model soundings above 800 hPa.

.LONG TERM...Tuesday Night Through Sunday
Issued at 246 AM CDT Mon Mar 20 2017

Forecast concerns mainly revolve around precip chances and types
during the Thursday thru Saturday time period.  The operational
models have shifted the track of a low pressure system southward
with the 12z and 00z cycles.  The ecmwf has been the most steady
with this system for the past several days now, and has a solution
near the ensemble means.  Will continue to favor its solution.

Tuesday night through Wednesday night...Canadian high pressure will
be sliding southeast across the region from Tuesday night through
Wednesday.  Should see mostly clear and below normal temps over
these two periods.  As the high moves to the mid-Atlantic states on
Wednesday night, moisture will be returning northward over the
northern Mississippi Valley.  Should be seeing increasing clouds as
a result, but a very dry airmass will likely keep a chance of light
snow out of the forecast until very late over north-central WI.

Rest of the forecast...The initial surge of moisture looks to shift
north of the region on Thursday morning.  Then will wait for a
secondary surge of moisture/precip to move northeast into the area
late Thursday afternoon and Thursday night.  Could see a wintry mix
as this precip arrives, due to the wet bulb effect within a dry low
level airmass.  As warmer air continues to surge northward, precip
should change over to all liquid over central and east-central WI
during the evening, but northern WI may have to wait for overnight
for this transition to occur.  Suppose its possible that small
accumulations of snow could occur over the north before the precip
changes to rain. As a warm front surges into southern WI on Friday
to go along with persistent mid-level fgen, periods of rain should
continue through the day.  Then low pressure will pass along the
southern Great Lakes on Friday night into Saturday, with precip
chances continuing, highest over east-central WI.  Some change over
back to snow still appears possible as colder air returns southward
on the backside of the low.  Still too early to get any gauge on
potential accums.  A Hudson Bay high then takes over for the rest of
the weekend and into early next week.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1243 PM CDT Mon Mar 20 2017

Mid level short wave passing over the region today will produce a
period of mid level clouds along with isolated sprinkles or light
showers. High pressure will then build into the area from the
north late tonight into Tuesday for continued VFR conditions.
Lower end VFR clouds may develop across the north Tuesday morning
with sct-bkn050 clouds develop late Tuesday morning elsewhere.
&&

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

$$

SHORT TERM.....Kurimski
LONG TERM......MPC
AVIATION.......TDH



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