Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 200041

Area Forecast Discussion
National Weather Service Green Bay WI
641 PM CST Sun Feb 19 2017

Updated aviation portion for 00Z TAF issuance

.SHORT TERM...Tonight and Monday
Issued at 226 PM CST Sun Feb 19 2017

Unseasonably mild temperatures will continue through the middle
of this week. Under partly cloudy to mostly cloudy skies, low
temperatures tonight will be in the 30s. Normal high for this
time of year is around 30. Based on guidance trends from last
night which were too cool, used the lowest three hourly temperatures
from guidance for lows at most spots. This is a few degrees
higher than the numerical guidance output.

High temperatures on Monday may be tempered some due to increasing
southeast flow, mostly cloudy skies and rain during the afternoon.
High temperatures across northeast Wisconsin near the bay and lake
may actually occur early Monday evening as winds turn to the
southwest and away from the colder waters. Looking at the convective
parameters for Monday afternoon, indices were approaching values
where thunder could occur. Per coordination, decided to leave
thunder out for Monday afternoon. Would not be surprised if there
was a clap or two of thunder.

.LONG TERM...Monday Night Through Sunday
Issued at 226 PM CST Sun Feb 19 2017

A cold front sweeping through the region on Monday night will
bring moderate rainfall as it sweeps through the western Great
Lakes. Rainfall amounts could reach or exceed half of an inch
given the juicy airmass as PWAT values exceed one inch. A few
rumbles of thunder are also possible given the mid level lapse
rates and some modest MUCAPE, especially across the southern cwa.
Despite the passage of the aforementioned cold front, temperatures
on Tuesday will actually reach or exceed Mondays highs as the
front lacks a significant push of cold air.

A low pressure system tracking through the northern Great Lakes
will bring the next chance of rain to the area Wednesday and
Wednesday night. Although the models show moisture with this
system will be fairly limited, keeping POPs relatively low and
confined to the north, the system will make up for with a push of
cold air Wednesday night as 850 mb temperatures plummet below zero
across the area. This will bring an end to the very warm
temperatures of the last week as highs Thursday are limited to the
mid 30s to the mid 40s.

Attention then turns to the system approaching the area late in
the week and into the weekend which will have a significant impact
on the western Great Lakes region. There is still a good deal of
model discrepancy amongst the NWP models in the track of this low,
which is contingent on how the low coming out of the plains
interacts with the low tracking across Canada. The more northern
solution offered by the ECMWF has a stronger low in Canada and
brings it close enough to the Canadian low to pull the plains low
further north putting a swath of heavy snow north and west of the
Fox Valley. The GFS solution maintains a weaker Canadian low which
does not pull the plains low north with a swath of heavy snow
across central and east-central Wisconsin. Overall it appears the
area is in store for a fairly significant snow storm late next
week into early next weekend, the main question appears to be
where the heaviest snow will fall. Given the different model
solutions and dependency on the low across Canada confidence is
fairly low in where this swath will set up.

.AVIATION...for 00Z TAF Issuance
Issued at 640 PM CST Sun Feb 19 2017

Good flying weather expected overnight with the exception of some
low level wind shear as a low level jet from the southeast around
25 knots sits about five hundred feet above the ground. Ceilings
and visibilities will lower Monday as southeast winds bring moist
and mild air into the area. SHowers are likely during the
afternoon and evening, which will bring conditions into IFR range.



SHORT TERM.....Eckberg
LONG TERM......Kurimski
AVIATION.......RDM is the U.S. government's official web portal to all federal, state and local government web resources and services.