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Area forecast discussion 
National Weather Service Green Bay WI
643 am CDT Friday Aug 1 2014

Updated aviation portion for 12z taf issuance

Short term...today...tonight...and Saturday
issued at 401 am CDT Friday Aug 1 2014

Precipitation trends...fog trends...the threat of strong to severe thunderstorms
this afternoon and evening...and temperatures...are the main forecast
concerns.

Isolated rain showers/thunderstorms and rain continued through the overnight hours in central
WI. This convection was occurring along a weak boundary...where a
narrow band of instability/moisture was situated. Expect a gradual
weakening trend to continue toward daybreak. Areas of fog...locally
dense...were also reported across the region...especially over NC
WI. At this time...it doesn't appear that the dense fog will be
widespread enough to issue an advisory...so will probably handle
with an Special Weather Statement and the severe weather potential statement. WV imagery showed a short wave trough dropping
south through western Ontario. This feature will likely have an
impact on our weather this afternoon and early evg.

Daytime heating and the short wave trough approaching from Ontario will
combine to trigger scattered/numerous thunderstorms this afternoon and early evg.
Instability will increase across the County Warning Area today...with cape ranging
from 500-1000 j/kg over the far north to 2000+ j/kg in parts of
c/ec WI. Shear will be marginal...but is expected to increase to
15 to 25 kts later in the day...which should be sufficient to
support scattered strong to severe multicell storms. Wet bulb zero
heights of 9500-10000 feet are favorable for large hail...and windex
values of 50-60 kts show some potential for damaging winds. There
have been a few reports of severe weather around the western Great Lakes
region for the past three days...but with increased instability
expected today...we could see a bit more activity. Scattered thunderstorms will
linger into the evg hours...then taper off as the short wave trough shifts
east and instability wanes. Clearing skies...light winds and
moisture from the afternoon/evening rains...should lead to another
round of fog late tonight.

Expect less convection on Saturday...as weak upper level ridging
occurs. Have kept some small probability of precipitation over our western and southern
counties during the afternoon...where some marginal instability
is expected to develop.

Used a blend of the top-performing guidance sets for maximum/min
temperatures. Expect highs to be in the upper 70s and lower 80s at
most locations...with low temperatures in the upper 40s to middle 50s.

Long term...Saturday night through Thursday
issued at 401 am CDT Friday Aug 1 2014

From Saturday night through early next week...the forecast area
will remain in the northwest flow aloft. A frontal system is
prognosticated to drop southeastward over the western Great Lakes region
Saturday night through Sunday before stalling over the southwest
half of Wisconsin. This frontal system will be aided with a short
wave trough on Sunday

After Monday...the front is prognosticated to be nearly stationary as
the flow becomes more zonal. Meanwhile high pressure will build
into the northern Great Lakes region. As a result probability of precipitation for much of
next week will likely be tapered from little or no precipitation over far
north central and northeast Wisconsin to higher probability of precipitation southward. The
forecast area will be caught between these systems. The h850
boundary also intensifies my middle week next week with a surface or
h850 low pressure region moving along this boundary...which could
set up an area of heavy rain. Precipitable waters climb to 1.50 to 1.75 inches
by Tuesday over the southwest half or two thirds of the state. For
forecast comparison...the 00z GFS indicates the boundary is mainly
south of the area along with the heavy rain. The 12z European model (ecmwf) was a
bit further north with more rain into central Wisconsin but the
later 00z run has also trended southward.
&&

Aviation...for 12z taf issuance
issued at 634 am CDT Friday Aug 1 2014

Areas of fog and associated IFR/LIFR/vlifr conditions will improve
over NC WI by 14z. Patchy fog over NE/c/ec WI should mix out a
bit quicker. An approaching upper level disturbance will combine
with increasing instability to produce scattered-numerous rain showers/thunderstorms and rain this
afternoon and early evg. A few of the storms will become strong
to severe...with hail and gusty winds. Have attempted to highlight
the most likely four-hour period for storms at each taf site.
Expect thunderstorms to wane after sunset...with clearing skies and light
winds leading to another round of fog during the late evening and
overnight. Based on the trends of the past couple nights...decided
to put prevailing vlifr conditions in the rhi taf late tonight.
&&

Grb watches/warnings/advisories...
none.
&&

$$

Short term.....Kieckbusch
long term......tdh
aviation.......kieckbusch

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