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fxus63 kgrb 221725 

Area forecast discussion
National Weather Service Green Bay WI
1125 am CST Fri Nov 22 2019

Updated aviation portion for 18z taf issuance

Short Saturday
issued at 223 am CST Fri Nov 22 2019

Quiet weather is expected across the western Great Lakes region
through Saturday as the area is in between a high pressure system
to the south and a low pressure system to the north. Clouds and
winds are expected to diminish later this morning as drier air
advects into the region. Highs today will return to below normal
levels, rising into the lower to middle 30s. Mostly clear skies
tonight will allow lows to fall into the lower to middle 20s. A
few clouds and some gusty winds are expected on Saturday as a weak
trough tracks through the western Great Lakes with daytime highs
ranging from the middle 30s across the north, and around 40 across
the south.

Long term...Saturday night through Thursday
issued at 223 am CST Fri Nov 22 2019

Split flow across the Continental U.S. To persist into early next week before
consolidating as an upper high builds toward the Gulf of Alaska and a
deepening upper trough develops over the western Continental U.S. Mid-week.
Models continue to struggle with an initial shortwave trough that
will move across the central Continental U.S. On Tuesday. Even model run-to-
run consistency (or lack thereof) persists, thus confidence
remains low. The flow headed into late next week becomes highly-
amplified with a longwave trough over the western conus, an upper
ridge over the central Continental U.S. And an upper trough over New England.
Possibly another system next weekend? Temperatures will be above
normal into early next week, then settle closer to normal mid-

A clipper system is forecast to move southeast into southern
Ontario Saturday night, accompanied by weak mid-level shortwave
trough. This system appears to be too far north to affect our
weather, other than perhaps bring some clouds to northern WI. Min
temperatures to be in the lower to middle 20s north, middle to
upper 20s south. This system continues to track across southern
Ontario on Sunday and not have any impact on northeast WI. A
prevailing west-southwest wind can be expected with more clouds
around due to the passage of a very weak shortwave trough. Max
temperatures to range from the upper 30s north-central WI, mainly
lower 40s elsewhere.

A second clipper system is expected to drop southeast into
southwest Ontario Sunday night with a cold front reaching western
WI by daybreak. Right now, any precipitation should remain in the
vicinity of the surface low where there is better forcing
associated by an accompanying shortwave trough. Anticipate plenty
of clouds Sunday night with min temperatures in the upper 20s
north, lower 30s south. This clipper is progged to move across
northern sections of the Great Lakes on Monday and bring a chance
of morning light snow north/slight chance of a rain/snow mix
central and east-central WI. As temperatures warm a bit, mainly a
chance of light rain across the forecast area in the afternoon
with perhaps a mix over north-central WI. Max temperatures for
Monday to range from the middle to upper 30s north-central, lower
40s for the rest of the area.

Small chance pops will linger into Monday night as the clipper
gradually pulls northeast into southeast Ontario. Any
precipitation would be very light and should not create any travel
issues. As for the initial system to move into the central Continental U.S.
On Tuesday, models continue to struggle with the amount of digging
the shortwave trough will take, the track and strength of the
associated surface low and how far north to take precipitation.
The 00z GFS remains on a southern track overall with a weaker
surface low. The CMC has flipped back to a northern track with a
stronger low pressure and measurable precipitation over central/
east-central WI. The European model (ecmwf) has also shifted north and is not that
different from the CMC. Until this system can get better sampled
by the upper-air network (sunday), look for model variability to
persist. For now, prefer to focus chance pops across central and
east-central WI with precipitation type either a mix or all rain
as Max temperatures to be in the lower to middle 30s north, middle
30s to around 40 degrees south.

The system would eventually track roughly from the mid-MS valley
northeast into eastern sections of the Great Lakes Tuesday night.
If the CMC/European model (ecmwf) solutions are correct, there would be travel
issues as mixed precipitation would change to all snow and winds
would crank up out of the northeast and lead to an increased risk
of Lakeshore flooding. Once again, it must be stressed that
confidence remains low on how all of this plays out. Stay tuned! A
ridge of high pressure builds into the region on Wednesday and
allow skies to become partly cloudy. Max temperatures to be around
30 degrees north-central, lower to middle 30s elsewhere.

This surface ridge to slide to our east on Thanksgiving day with a
return flow setting up over WI. Also at this time, an upper ridge
is progged to be situated over the east-central Continental U.S.. onset of
warm air advection may bring some clouds and a chance of either light snow or a
rain/snow mix to northeast WI. Max temperatures on Thanksgiving
should be similar to Wednesday or a few degrees below normal for
late November.

Aviation...for 18z taf issuance
issued at 1124 am CST Fri Nov 22 2019

During the late morning clouds started to break apart and
conditions were improving from MVFR to VFR across central and
northeast WI. Expect this trend to continue as high pressure
builds in from the west, with all locations improving to VFR by
mid- afternoon. Skies remain clear through the night. Low level wind shear is
expected late tonight and Saturday morning across northern and
central WI, from about 07z to 15z, at the krhi, kauw, kcwa taf
sites. Southwest winds start gusting to around 15 to 20 kts late
Saturday morning at all sites.

Grb watches/warnings/advisories...


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