Forecast Discussion for GRB NWS Office
FXUS63 KGRB 152337

Area Forecast Discussion
National Weather Service Green Bay WI
537 PM CST Fri Feb 15 2019

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Saturday
Issued at 216 PM CST Fri Feb 15 2019

Generally quiet weather expected in the short term forecast, with
the main focus on cloud trends and temperatures

Surface analysis at 20Z showed an area of low pressure in
southeast Ontario with an inverted trough extending west across
Upper Michigan and far northern Wisconsin. Some shortwave energy
was also lingering across the north. As a result, some lower
clouds were moving into far northern Wisconsin through the
afternoon. Some very light snow or flurries were also being
reported at times. Based on webcams this seemed reasonable. Kept
flurries in the north though the evening.

Tonight, winds will become light or calm at times as the low moves
further east and surface high pressure builds into the area.
Skies will also remain mainly clear, aside from some lower clouds
across the north. This leads to a good setup for radiational
cooling. Lows are forecast to fall into the single digits below
zero across central and north- central Wisconsin, and in the
single digits above zero across eastern Wisconsin. Light winds
should keep the wind chills values from becoming an issue.

Saturday, meso models show some scattered clouds moving in from
the west, but with such dry time sections hesitate to go too
overboard on the sky cover. Overall, expect a partly to mostly
sunny day. Cooler air sticks around, with highs in the lower 20s,
but winds will be lighter.

.LONG TERM...Saturday Night Through Friday
Issued at 216 PM CST Fri Feb 15 2019

The upper air pattern will feature a 500mb trough across western
North America with a building ridge across the southeast United
States. This pattern will lead to a southwest flow aloft with a
weak system on Sunday and then a more potent system late Tuesday
night into Wednesday night.

For Saturday night, high pressure will dominate the weather
pattern, bringing another night of cold temperatures. Low
temperatures will drop to around zero far north to 10 to 15
near Lake Michigan. With clouds on the increase, temperatures
across central and east-central Wisconsin may actually rise a
few degrees after midnight. The system on Sunday is passing
well south of the area, however some light snow may make into
central and east-central Wisconsin Sunday morning and linger
into Sunday evening. An inch or two is possible with this system.
Confidence is moderate in the snowfall amounts at this time. There
is still concern on the extent of the northern edge of the snow
due to dry air from Canadian high pressure. The NAM 12 supports
my concern on the northward extent of the snow as this model
keeps the area dry Sunday and Sunday night.

Otherwise, high pressure will prevail across the region Monday
and Tuesday. Next system approaches from the southwest Tuesday
night. Light snow could make it into our southern counties by
12z Wednesday, thus a small chance of light snow after midnight.
Snow is expected on Wednesday into Wednesday night with several
inches possible as upper system moves across the area. There
may be a few lingering flurries or light snow showers on Thursday
with dry conditions expected on Friday. Below normal temperatures
are expected into early next week, with temperatures moderating
closer to normal by the end of the next week.

.AVIATION...for 00Z TAF Issuance
Issued at 531 PM CST Fri Feb 15 2019

MVFR ceilings and scattered light snow showers or flurries were
reported across north central and far northeast WI at the
beginning of the TAF period, but improving conditions are
anticipated this evening as a ridge of high pressure arrives.
Some models are suggesting patchy fog and low clouds over north
central WI late tonight into Saturday morning, so added some MVFR
VSBYs at RHI. The rest of the area should see VFR conditions
through the period.




LONG TERM......Eckberg

NWS GRB Office Area Forecast Discussion