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000
FXUS63 KGRB 171742
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1242 PM CDT Tue Oct 17 2017

Updated aviation portion for 18Z TAF issuance

.SYNOPSIS...
Issued at 321 AM CDT Tue Oct 17 2017

Mild, quiet mid-autumn weather to continue for the rest of the
week.

Relatively low amplitude large scale flow is in place across
North America, with the main westerlies pretty far north for this
time of year--primarily across southern Canada. The pattern will
gain some amplitude during the week, with a longwave trough
forming near the West Coast and downstream ridging developing mid-
continent. That pattern will likely be be short-lived, as the
development of a much stronger trough out near 160W will result in
a transition to ridging near the West Coast, and troughing over
the Great Lakes region by the end of the period.

Temperatures 10 to 15 F degrees above normal are expected into the
upcoming weekend, then readings will drop back close to normal by
early next week. Normal precipitation for a week at this time of
year is down to a little over 1/2 inch. In addition, we`ve
entered the time of year where receiving significant precipitation
requires a direct influx of Gulf moisture. Dry air and a lack of
dynamics will result in dry weather into the weekend. The best
chance for rain will be with a frontal system crossing the area
this weekend, but that system seems unlikely to bring significant
rains, so amounts are likely to end up below normal for the
period.
&&

.SHORT TERM...Today...Tonight...and Wednesday
Issued at 321 AM CDT Tue Oct 17 2017

Quiet weather is expected as the main westerlies remain to the
north. Edged max temperatures a little above the broad-based
guidance to account for the very mild air mass flowing into the
region. Mins are a little trickier as any areas that decouple
could have temperatures drop a little more than depicted on the
guidance. Edged the typical cool spots down a little to account
for this, but that still left mins well above normal. Rather windy
conditions are expected by Wednesday afternoon as the gradient
tightens ahead of a cyclone tracking across southern Canada.

.LONG TERM...Wednesday Night Through Monday
Issued at 321 AM CDT Tue Oct 17 2017

500mb ridge across the eastern United States will bring above normal
temperatures to the region into the latter half of the weekend. High
temperatures on Friday and Saturday could reach the 70s at some spots.
The normal high temperature for this time of year is in the middle
to upper 50s.

Some significant timing differences with the cold front and the
arrival of rain across the area this weekend. The GFS/Canadian
models were quicker and would bring rain to the area Saturday
afternoon and Saturday night with a lingering chance Sunday
morning. The ECMWF was about to 12 to 18 hours slower and would
bring rain to the area later Saturday night into Sunday. Took a
blend of the model guidance for now until timing differences get
resolved. Perusal of the convective parameters would indicate
there is a slight chance of a thunderstorm with the passage of the
cold front. Severe weather is not expected. Temperatures return
close to or slightly below normal early next week.
&&

.AVIATION...for 18Z TAF Issuance
Issued at 1242 PM CDT Tue Oct 17 2017

Prevailing VFR conditions are expected through the end of the TAF
valid period. There were only some high clouds across the north
at midday. LLWS is a concern in parts of east central Wisconsin
for a few hours after midnight. Other than that, generally clear
skies with just enough surface flow to keep fog from becoming an
issue. Southerly flow increases during the morning on Wednesday
and winds become gusty.
&&

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

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Skowronski
LONG TERM......Eckberg
AVIATION.......MG