Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kgrb 300832 

Area forecast discussion
National Weather Service Green Bay WI
332 am CDT Tue may 30 2017

Forecast discussion for routine morning forecast issuance

issued at 329 am CDT Tue may 30 2017

Cool with scattered showers again today, then warmer and drier for
a couple days before cooler and wetter weather returns for the

The upper flow across North America is dominated by a fairly
Sharp Ridge over the intermountain west and a deep trough centered
over Ontario. Those features will maintain their intensity for a
couple days and then weaken some late in the week. Of more
importance is likely to be the development of a modest branch of
westerlies forecast to undercut the western ridge and feed
increasing amounts of Pacific energy eastward across the central
and northern Continental U.S..

The period will begin cool and showery due to the influence of the
Ontario upper trough. A couple days of drier and warmer weather
will follow as the trough shifts/elongates eastward allowing
upper heights across the forecast area to rise. Precipitation
chances will return as an emerging branch of the upper flow
undercuts the western ridge late in the week or during the
upcoming weekend. Precipitation totals for the week will be highly
dependent on how much falls with that, and as such are difficult
to gauge.

Short Wednesday
issued at 329 am CDT Tue may 30 2017

Today will be similar to yesterday only cooler and probably with
the showers having slightly lower coverage. Satellite indicated a
well-defined vort across northeast Minnesota early this morning,
and it should slide across the forecast area during the mid-day
hours. Instability is not expected to be quite as great as
yesterday as mid-level lapse rates will be a little lower.
Confined the mention of thunder to the afternoon, and to the
southern portion of the area where models generated the greatest
CAPES. That fit well with the general thunder area in the Storm Prediction Center
swody1 outlook.

Showers are likely to linger into tonight, especially across the
north where another weak shortwave is likely to track this
evening. By Wednesday, rising upper heights and warming aloft will
result in more stable conditions. Would not be surprised if a few
showers lingered in the northeast early in the day, but stuck
with a dry forecast for now.

Edged temperatures toward a blend of the top-performing guidance
products, which was not really a big chance from the previous

Long term...Wednesday night through Monday
issued at 329 am CDT Tue may 30 2017

The forecast period will start out quiet Wednesday night and then
become more active Thursday night into the weekend as a few
systems moves across the region. For Wednesday night, latest
numerical guidance has come in cooler with low temperatures for
this period. With clear skies and light winds, trended close to
the latest guidance. This would mean that our typically colder
spots across the north could see some patchy frost. Added this
scenario to the hazardous weather outlook (hwo). Mild conditions
will prevail on Thursday with low afternoon relative humidity
readings. Readings could be down to 30 to 35 percent across the

On Thursday night, a warm front will approach from the southwest.
Some differences in the models if convection would make into
central and east-central Wisconsin. Per coordination with offices
to the west, have raised chances of rain in this region. Steep
mid level lapse would still support the chance of thunderstorms.
Chances of showers and storms continue into Friday and Friday
night. Latest indications are that a convective complex south of
the area would push the front south late Friday night and Saturday
morning. This could lead to a lull or end of precipitation for a
period of time until the main low pressure system approaches from
the west Saturday afternoon. Leaned toward the European model (ecmwf)/Canadian
solution for now as the GFS appears to be an outlier with
precipitation well south and west of Wisconsin. The European model (ecmwf)/Canadian
bring the low south of the forecast area Saturday night and then
into the eastern Great Lakes Sunday. This system would bring
another round of steadier rains and increasing northerly winds.
Any lingering rain would end Sunday during the day for most
locations. Some afternoon instability showers are still possible
on Monday across northern Wisconsin.

Mild temperatures expected Thursday and Friday, then temperature
should run at or slightly below normal for the weekend into much
of next week.

Aviation...for 12z taf issuance
issued at 329 am CDT Tue may 30 2017

VFR conditions prevailed across the area early this morning,
though there were some lower ceilings (mvfr) back in Minnesota.
Anticipate primarily VFR ceilings during the period, though a
brief period of MVFR ceilings is possible in central and north-
central Wisconsin this morning when convective clouds first form.
MVFR ceilings are possible across the north again tonight, though
confidence in that aspect of the forecast is rather low.

Grb watches/warnings/advisories...


National Weather Service Glossary of Abbreviations