Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Green Bay WI
611 am CDT Wednesday Oct 22 2014
Updated aviation portion for 12z taf issuance
Short term...today...tonight...and Thursday
issued at 330 am CDT Wednesday Oct 22 2014
The latest RUC analysis and satellite/radar imagery show a large
high pressure system stretching from Quebec to the western Great
Lakes to the Gulf Coast. Outside of a small area of broken stratus
around Chicago...clear skies exist across the region thanks to
strong subsidence beneath a middle-level ridge. The next storm system
is moving across The Rockies and the northwest Great Plains where a
few lightning strikes are occurring. As this storm system moves
east...precipitation chances and timing are the main forecast concerns.
Today...Canadian high pressure will slowly shift to the central
Great Lakes...but very dry air will exist through the column.
Although will see cirrus begin to invade the central and western
portions of the state during the afternoon...should see sunny skies
with highs a few degrees warmer in many locations than yesterday.
Tonight...a shortwave trough and associated cold front will move
across the plains and into the northern Mississippi Valley late.
The very dry air will remain overhead to start the evening but
should see clouds increase middle to late evening over north-central
Wisconsin and overnight across northeast Wisconsin. Models indicate
a few showers could move into north-central Wisconsin around
midnight in the middle-level moisture advection regime and left a small
chance to account for this scenario. But better chances will move
into the Route 39/51 corridor late. The increasing clouds and
tightening pressure gradient calls for a warmer night. Lows ranging
from the lower 30s northeast to around 40 west.
Thursday...the shortwave and cold front will weaken as it moves east
across the state. A band of rain will accompany the front with
precipitation moving across central and north-central Wisconsin during the
morning and into eastern Wisconsin during the afternoon. Various
models move the precipitation through the region at different times (due to
different handling of the splitting of middle-level energy)...so there
is some uncertainty in regards to timing. Regardless...as the rain
moves into more stable air...intensity and coverage should gradually
wane through the day. Will have the highest chances during the
morning consequently. Temperatures will warm the most in eastern
Wisconsin before the rain arrives and adjusted temperatures a bit.
Long term...Thursday night through Tuesday
issued at 330 am CDT Wednesday Oct 22 2014
Showers will exit the area Thursday night as an upper trough
and associated surface front move into Michigan. The NAM
forecasts additional showers Friday night as a short wave trough
moves across northern Wisconsin. The GFS and European model (ecmwf) are much weaker
with the system and are dry. Left out any precipitation for Friday
night. Dry northwest upper flow expected Saturday through Sunday.
Rising heights should result in surface temperatures climbing
above seasonal averages.
Split flow forecast by models Sunday night through Tuesday with
some jet energy moving by to the north Sunday night and Monday
providing upper support for possible elevated showers and
thunderstorms north of a warm front. Jet energy lifting out of the
Central Plains is forecast to produce a synoptic scale system
lifting out of the Southern Plains towards the Great Lakes Monday
afternoon through Tuesday. There are big differences in track and
intensity between the European model (ecmwf) and GFS related to the amount of
phasing with northern stream jet energy.
After that it looks like dry northwest flow returns for the middle
and end of next week with slightly cooler temperatures. Overall it
looks like a seasonable weather pattern through early November
with moderate amplitude progressive upper flow.
Aviation...for 12z taf issuance
issued at 610 am CDT Wednesday Oct 22 2014
Good flying weather will be present today across the region thanks
to Canadian high pressure. Clouds will be on the increase tonight
from west to east. Conditions will remain VFR...but anticipate ceilings
will be falling between 5000-8000 feet after midnight. Light rain may
be pushing into central and north-central Wisconsin around the end
of the taf period.