Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 160800
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
300 AM CDT Mon Oct 16 2017

Forecast discussion for routine morning forecast issuance

.SHORT TERM...Today...Tonight...and Tuesday
Issued at 259 AM CDT Mon Oct 16 2017

Light winds and breaks in the clouds will lead to frost across
portions of central Wisconsin this morning. The Frost Advisory
will remain in effect through 14Z across Marathon, Wood and
Portage counties. Elsewhere a cold start to the morning will lead
to a warmer day as mostly sunny skies allow temperatures to
rebound to around normal levels with highs in the middle to upper
50s. High pressure will keep the weather dry across the western
Great Lakes to start the work week. Lows tonight will be a bit
warmer as surface winds turn southwesterly, with temperatures
ranging from the upper 30s to the lower to middle 40s. Even warmer
temperatures are expected on Tuesday as warmer air advects in,
allowing highs to rise into the middle to upper 60s.

.LONG TERM...Tuesday Night Through Sunday
Issued at 259 AM CDT Mon Oct 16 2017

Models remain in good agreement with the mean flow across the
CONUS transitioning from near zonal mid-week, to a western CONUS
upper trough/eastern CONUS upper ridge by the end of the work
week. This trough is of a progressive nature, thus reaching the
central Plains by next Sunday. As the mean flow turns southwest
into WI this week, look for temperatures to be well-above normal
through the period. As for precipitation, expect below normal
amounts as Pacific systems stay to our north.

A southwest wind flow (both at the surface and up to 8H) will
continue into WI between high pressure to our southeast and an
area of low pressure well to our north-northwest. The resultant
tight pressure gradient will keep the atmosphere mixed through the
night and prevent temperatures from falling too far despite mostly
clear skies. Look for min temperatures in the lower to middle 40s
north, middle 40s to around 50 degrees south. As the surface low
tracks east into Hudson Bay on Wednesday, it will drag a cold
front into the western Great Lakes during the afternoon. A lack of
low-level moisture/mid-level forcing would preclude any mention of
precipitation, let alone much in the way of clouds. Therefore,
expect a mostly sunny, mild and breezy day across northeast WI as
max temperatures reach the middle 60s north-central WI/near Lake
MI, mainly upper 60s elsewhere.

This weak cold front sweeps across the rest of WI Wednesday
evening and be replaced by a weak ridge of high pressure later
Wednesday night. Only a wind shift from west-southwest to west-
northwest along with a few clouds, will mark the frontal passage.
Min temperatures are expected to cool a bit with readings in the
upper 30s to around 40 degrees north-central, to the upper 40s
east-central WI. As the surface ridge gradually slides to the east
on Thursday, winds will back to the south-southwest and bring weak
WAA back into WI. Expect mostly sunny skies, mild temperatures and
winds under 10 mph to make for a great autumn day. Max
temperatures should drop some on Wednesday, generally in the lower
to middle 60s.

By next Friday, the new upper trough is forecast to hit the West
Coast and begin to move inland. As this occurs, upper heights will
build across the east-central CONUS and 8H temperatures will rise
to around +16C. Under mostly sunny skies, temperatures could reach
around 15 degrees above normal which would place readings in the
upper 60s north-central, upper 60s to lower 70s elsewhere except
middle 60s near Lake MI where south winds may tap colder lake
water temperatures.

This upper trough is progged to roll through the Rockies Friday
night and into the Plains on Saturday. Preceding this trough will
be a cold front that is forecast to move across the Upper MS
Valley toward the Midwest by Saturday afternoon. As one would
expect this far out in time, there are some timing issues with the
location of the cold front next Saturday. For now, have followed
the consensus solution which increases clouds Saturday morning,
then brings a chance of showers to most of northeast WI Saturday
afternoon. Much too early to determine the extent of any
instability, thus have kept thunder out of the forecast for now.
Max temperatures should still be able to hit the middle 60s to
around 70 degrees despite the increase in clouds/rain chances,
mainly due to the mild start to the day.

This progressive, but weakening upper trough sweeps into the Great
Lakes region next Sunday, with the cold front to push through
northeast WI either late Saturday night or Sunday morning. There
should be enough moisture in place before the front arrives, thus
rain chances will be necessary for Saturday night through last
Sunday morning depending on the exact timing of the frontal
passage. Much like Saturday, too many questions regarding
instability to mention any thunder. Temperatures will cool a bit
with clouds/precipitation, thus readings only to reach around 60
degrees north-central, middle to upper 60s eastern WI (still
around 10 degrees above normal).
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1124 PM CDT Sun Oct 15 2017

SCT-BKN stratocumulus and altocumulus clouds will persist until
an upper level disturbance shifts east of the region overnight.
Light west winds are anticipated overnight, but should increase
to 10-15 knots during the late morning and afternoon on Monday.
Surface winds will decrease again by Monday evening, but winds
aloft will increase to 35 to 40 knots, leading to some LLWS by
mid to late evening. This will be the primary aviation concern
during this TAF period.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Frost Advisory until 9 AM CDT this morning for WIZ030-035-036.
&&

$$

SHORT TERM.....Kurimski
LONG TERM......Kallas
AVIATION.......Kieckbusch


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