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000
FXUS63 KGRB 200315
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1015 PM CDT Fri Apr 19 2024

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Scattered snow showers could result in briefly reduced
  visibilities tonight over north-central Wisconsin. Any snow
  accumulation will be minimal.

- Elevated fire weather conditions are possible on Sunday and
  Monday afternoons due to low relative humidities ranging from
  25 to 30 percent and sustained winds of 10 to 20 mph.

- Next chance for precip returns late Monday through late Tuesday.
  Rain will be the main precipitation type, but some snow may mix
  in across the far north on Tuesday.

&&

.DISCUSSION...
Issued at 200 PM CDT Fri Apr 19 2024

Short Term...Tonight and Saturday

Breezy day across much of the area. Peak gusts have reached around
40 mph at times, especially central to east-central Wisconsin.
Clouds have steadily built from northwest to southeast as
vigorgous shortwave within broad upper trough works toward the
area. Thus far, snow showers over north-central WI have been very
isolated and light. Given steep low-level lapse rates (9-10c/km in
lowest 1.5km) and the approaching sharp PV anamoly/shortwave,
expect snow showers to increase especially over north-central WI
along and north of the track of the wave. Not much for snow
accumulations, but brief lower visibility could occur as has
occurred upstream today at times in northeast MN. These diurnally
enhanced snow showers will fade away early this evening.

Then, later this evening and overnight, more snow showers or flurries
could occur again mainly northern areas as another embedded shortwave
within the larger scale trough rotates across. This wave along
with deeper moisture (to H6) and NW winds flowing across western
Lake Superior with H85 temps down to -9c to -11c (water temps of
3-4c) should result in at least scattered snow showers due to weak
lake enhancement and upslope lifting into north-central WI. Snow
accumulations will be minor, generally under an inch over Vilas
County. Chilly night no matter where you are at with readings in
the mid 20s northern Wisconsin, to only the lower 30s from the Fox
Valley to the lakeshore.

On Saturday, we`ll be in wake of the shortwave moving through
tonight so there will probably be subsidence to start the day.
Even so, we`ll also be on the edge of the thermal trough and there
will be sufficient low-level moisture. Liked and retained previous
shifts idea of adding some small chancy pops for light snow
showers/sprinkles with coverage maxing out late morning into the
early afternoon. NW winds will be breezy, though not as strong as
we have seen today. High temperatures will range from the lower
40s north-central WI, to the mid to upper 40s elsewhere.

Long Term...Saturday Night Through Friday

Precipitation...Quiet weather remains expected for the second half
of the weekend as an upper trough slowly lifts to the northeast.
Then a shortwave energy and an associated surface low will bring
precipitation to the region during the late Monday afternoon through
Tuesday time frame.

The shortwave is looking more disjointed in the latest forecast
cycle and the large spread with the timing/strength of the impulse
makes it difficult to add high resolution to the forecast.
Regardless, guidance generally points to around 0.15 to 0.30 inches
of precipitation, which is trending down compared to the forecast
yesterday.

Still think that dynamics are relatively robust given the 40+ kt low
level jet and mid-level lapse rates of  7 C/km will accompany the
shortwave.  That could lead to a few thunderstorms, but probability
looks low at this time.

Probabilities remain low (less than 20%) for snow on the backside of
the system across northern WI on Tuesday.  If snow were to occur,
warm temperatures during the daylight hours would lead to near zero
impacts.

Another chance of precipitation will occur late next week from a
southern stream system.

Temperatures:  Will be on a roller coaster ride over the next week,
but no anomalous cold or heat is expected.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1006 PM CDT Fri Apr 19 2024

Another round of scattered snow showers is expected to impact NC
WI overnight, with possible MVFR/IFR vsbys at the RHI TAF site
during the early part of the TAF period. A few snow showers or
flurries may linger into Saturday morning before ending. Ceilings
should prevail in the 4000-6000 ft AGL range for much of the TAF
period, though MVFR ceilings may accompany any snow showers, and
may also move into NC WI late tonight into Saturday morning.
Gusty WNW winds will decrease slightly overnight, increase again
late Saturday morning, then diminish Saturday evening. Clearing
skies are anticipated by sunset.

&&

.FIRE WEATHER...
Issued at 200 PM CDT Fri Apr 19 2024

Moderating temperatures and a dry airmass will lead to elevated fire
weather days on Sunday and Monday. Winds will be a little stronger
on Sunday compared to Monday with sustained values of 15-20 mph and
gusts up to 30 mph (sustained winds 10-15 mph with gusts to 25 mph
on Monday).  While elevated fire weather conditions will be present
each day, concern is a little higher on Sunday due to
slightly stronger winds.

Another period of elevated fire weather conditions is possible next
Wednesday and Thursday as a Hudson Bay high pressure system moves
into the region.  PWATs are forecast to be 20% of normal according
to the GFS ensemble.  Because of the proximity of the high, winds
will likely be below critical criteria.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....JLA/MPC
AVIATION.......Kieckbusch
FIRE WEATHER...MPC