Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Green Bay WI
1057 PM CDT sun Aug 30 2015

Updated aviation portion for 06z taf issuance

Short term...tonight and Monday
issued at 229 PM CDT sun Aug 30 2015

Much like last night...the main forecast problem centers on amount/depth
of stratus or fog development tonight/Monday morning as only subtle
synoptic changes have occurred over the past 24 hours. The impact
of the clouds/fog will also impact temperatures...especially Max's on Monday.

The 19z msas surface analysis indicated an area of hi pressure extended
from the Central Plains northeastward through southern sections of the Great Lakes.
An area of low pressure was located over ND/southern Manitoba. The pressure
gradient was tightening over the plains/upper Midwest where gusts
were over 20 miles per hour. Vsbl satellite imagery showed a band of low clouds
from the southern half of WI southward...which had impacted temperatures this

One change synoptically to be the location of the surface hi which will
have shifted farther east and allowed for a bit more boundary
layer wind to occur over WI tonight. Variable clouds are expected
this evening...but with surface winds becoming light once again and
dew points holding in the upper 50s to lower 60s..fully anticipate
another round of low clouds and fog to develop later this evening
through the overnight hours. Do not believe the fog will be as thick as
last night due to higher winds aloft...but still think some visibilities
could drop below one mile in some locations. Marine fog remains a
concern with the moist air moving over the cool waters of the
lake (from Sturgeon Bay south). May need to issue another
headline later tonight. Min temperatures to range from the middle to upper 50s
north...upper 50s to lower 60s south.

Even though the surface hi to be well to our east on upper ridge
axis to stretch from the Southern Plains NE to the Great Lakes and help
to keep dry conditions across NE WI. Main questions again for Monday
will be how long the low clouds/fog to hang around and impact on
temperatures...especially with very warm temperatures aloft (8h temperatures up to
almost +20c). Based on what vsbl satellite imagery is showing over
Minnesota this afternoon (much quicker clearing)...will try for the
optimistic approach and go for mostly sunny skies by late Monday
morning through the rest of the day. This would allow for maximum temperatures
to soar into the middle to upper 70s near Lake Michigan...lower to middle 80s for
the rest of the forecast area.

Long term...Monday night through Sunday
issued at 229 PM CDT sun Aug 30 2015

A return to warm and humid minor precipitation for the
middle to late part of the week...are the main forecast concerns.

A very persistent pattern will be in place...with a strong upper
level ridge over the Great Lakes...high pressure to our east...and
a steady south return flow into Wisconsin. Overall...this pattern
strongly supports above to much above normal temperatures...muggy
conditions and periods of marine fog on Lake Michigan. Precipitation will
be spotty at best due to the presence of the upper ridge...but
with dew points well into the 60s...precipitable water values near
1.5 inches and diurnal is tough to rule out
rain showers/thunderstorms and rain with any weak front or short wave trough that moves through.
Models still show a weakening front moving into northern WI Tuesday
afternoon...and also generally agree that a short wave trough will top the
ridge and move through north WI sometime in the Wednesday-Thursday period. The
best chance of precipitation would appear to be late in the weekend as a
more significant frontal boundary edges into the western Great

Aviation...for 06z taf issuance
issued at 1056 PM CDT sun Aug 30 2015

Clear skies and a light southwest wind will lead to the formation
of areas of IFR ceilings and visibilities due to fog overnight...which will
linger into Monday morning. Some patches of LIFR visibilities deu to
dense fog also expected. Increasing southwest winds Monday
morning and resultant mixing will improve conditions to VFR levels
by Monday late morning or afternoon.


Grb watches/warnings/advisories...


Short term.....AK
long term......kieckbusch

National Weather Service Glossary of Abbreviations