Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Green Bay WI
557 am CDT Monday may 25 2015

Updated aviation portion for 12z taf issuance

Short Tuesday
issued at 309 am CDT Monday may 25 2015

Low pressure over the Iowa/Minnesota border will lift northeast
through northern Wisconsin early this afternoon...continuing
northeast just south of James Bay late tonight. As the low lifts
north a warm front will lift north...placing northeast Wisconsin
in the warm sector of this system. In addition a pronounced dry
slot...evident on water vapor imagery...will lift northeast with
the low over the eastern portion of the County Warning Area this afternoon. The
dry slot should allow some filtered sunshine across the eastern
County Warning Area this afternoon...allowing highs to soar to around 80 degrees.
A tight pressure gradient and strong 40 knot low level jet will
cause wind gusts to increase this afternoon as the aforementioned
filtered sunshine in the warm sector allows some of these winds to
mix down to the surface...with wind gusts as high as 40 miles per hour
possible at times.

Severe potential this afternoon and early this evening will be
highly dependent on the amount of instability that can build from
incoming solar radiation as well as the depth of the instability.
While model soundings show close to 1000 j/kg of cape across the
eastern County Warning Area this afternoon...there is a layer of warm air around
650 mb which could inhibit vertical growth of cumulonimbus clouds.
That being said there are fairly high winds with the
aforementioned low level jet so getting damaging winds to the
surface may not be that difficult of a task. Given all of the
what ifs during this period a marginal risk across the southern
County Warning Area continues to be reasonable per the Storm Prediction Center day 1 outlook.

As the low lifts north into Canada the cold front associated with
this system will stall out over the western Great Lakes. Without
much in the way of middle level support rain chances will drop off
later tonight. By Tuesday the middle level trough...currently shown
on water vapor over northern Colorado...will track northeast along
the frontal boundary draped across the Midwest and bring another
round of showers to northeast Wisconsin. Despite the current
strength of this is expected to weaken as it ejects
out of the plains and heads northeast towards the western Great
Lakes. The weakening system...when combined with fairly modest
instability values...means thunder chances are a bit tenuous for
Tuesday despite daytime highs soaring into the 70s. Given the
modest instability and dynamics will not completely remove
thunder...but will back off a bit from the previous forecast and
only include a chance during the afternoon hours.

Long term...Tuesday night through Sunday
issued at 309 am CDT Monday may 25 2015

Models continued to keep southwest upper level flow across the
area until a trough axis passes through Wisconsin on Wednesday.
Short waves in the southwest flow will bring chances for showers
and thunderstorms to the area Tuesday night into Wednesday. A
surface ridge and low amplitude upper ridge should keep the area
dry for Wednesday night and Thursday. Chances for showers and
storms return ahead of an approaching surface cold front and the
next upper trough. The front should push through the area on
Friday/Friday night. Do not expect thunderstorms once the front
has passed...but there is still a chance for showers on
Saturday...mainly in central and east central Wisconsin. After looks like only a slight chance for showers at most.

Temperatures for the remainder of the work week should be well
above normal at most locations...but colder air behind the
departing cold front will bring below normal highs back for the

Aviation...for 12z taf issuance
issued at 557 am CDT Monday may 25 2015

Another area of showers will lift through the taf sites this
morning...bringing conditions down to IFR at times. Overall
conditions will vary widely between the showers...with VFR
possible at times but not for an extended period of time this
morning. A dry slot is expected to bring an end to the showers
over the southeast half of the forecast area in the afternoon. Conditions
should improve to MVFR/local VFR within the dry slot...and SW
winds will gust to around 30 kts at the grb/atw/mtw taf sites. Scattered
thunderstorms may develop near a cold front in central WI by late
afternoon or early evg...and may track into ec WI during the
evg...but confidence is too low to mention at the southern taf
sites right now. Another break in the action is expected later
tonight as the low lifts north. Conditions are expected to crash
across the western taf sites due to light winds and high levels of
low level moisture.

Grb watches/warnings/advisories...


Short term.....Kurimski

National Weather Service Glossary of Abbreviations