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Area forecast discussion 
National Weather Service Green Bay WI
245 am CDT Tuesday Jun 30 2015

Forecast discussion for routine morning forecast issuance

Synopsis...
issued at 241 am CDT Tuesday Jun 30 2015

Seasonably cool the next couple days...then temperatures warming
back close to normal for the Independence day weekend.

Northwesterly upper flow will continue throughout the forecast period...but with
some fluctuations in amplitude/strength of the flow. A fresh surge
of Canadian air into the forecast area will drop temperatures to
seasonably cool levels the next couple days...then readings should
warm back to near normal for the rest of the period. Once any
lingering rain showers/thunderstorms and rain in the east end today...the next sig chance for precipitation
will probably not occur until late in the weekend or early next
week. So precipitation amnts for the next 7 days will probably come down to
what occurs with that event.
&&

Short term...today...tonight...and Wednesday
issued at 241 am CDT Tuesday Jun 30 2015

Main band of rain showers/thunderstorms and rain with frontal system crossing the region were
slow to exit the east this morning. Precipitation has also had a tendency to
backbuild. Instability is limited...but given the remaining
forcing and low-level convergence...will need to keep probability of precipitation in the
far east at least through the morning. Final probability of precipitation will be an issuance
time decision. Some fog will also develop...but with pressure
gradient tightening from NW-se...will likely be able to handle it
without a dense fog advisory. Guidance temperatures for today/S highs were
cooler than previous forecast. Trended forecast in that direction...though was
not comfortable going quite as cool as guidance indicated.

High pressure will gradually settle into the region tonight and Wednesday.
With light winds...there could be enough lingering moisture for some
fog again tonight. That was already in the forecast...so stuck with it. The
NAM/S low-level relative humidity looked too high on Wednesday...so trended toward
sunnier conditions. Edged mins tonight down toward a blend of the top
performing guidance products...then stuck close to the blend for
Wednesday/S highs.

Long term...Wednesday night through Monday
issued at 241 am CDT Tuesday Jun 30 2015

Prevailing amplified flow consisting of the western Continental U.S. Upper ridge/
east-central Continental U.S. Upper trough will continue through the end of the work week
before changes begin to occur this weekend. Models continue to show an
impressive closed upper low (for summer) to move across southern Canada
and flatten the upper ridge in the process. This pattern shift will turn
the flow closer to zonal over the northern tier of states and allow
temperatures to warm to or slightly above normal from the weekend into
early next week. Precipitation chances to be tied to the passage of a
shortwave trough around Friday and a cold front around Monday.

Hi pressure is forecast to be parked over the western Great Lakes Wednesday night and
will bring mostly clear skies...light winds and cool conditions to
NE WI. Near ideal radiational cooling will send min temperatures down into
the lower to middle 40s north...upper 40s to lower 50s south. If enough dry
air can advect into the area...would not be shocked to see a
couple of upper 30s for temperatures in the far north. This surface hi will
stretch across the entire Great Lakes region on Thursday...so
anticipate plenty of sunshine with comfortable humidity levels
considering we are in early July. Despite the cool start to the
day...the dry air mass overhead will allow maximum temperatures to reach near
70 degrees near Lake Michigan...generally in the middle 70s elsewhere.

Models show a pretty strong shortwave diving southeast through the Midwest
Thursday night...however with the surface hi anchored over the Great Lakes...
do not see how any precipitation can make a push in our direction. Have
removed the slight chance pop from central WI and keep sky conditions
either mostly clear or partly cloudy. The air mass over WI to have
modified a bit by Thursday night...thus temperatures will not be nearly as cool as
Wednesday night. Instead...look for min temperatures to range from the lower 50s
north...to the middle 50s south. Questions then arise for Friday as the
models are in dispute with regards to the strength of a shortwave
trough prognosticated to move into the Great Lakes. The trend has been for
this trough to weaken...the aforementioned shortwave to pass to our
south and the stubborn surface hi to hang around the Great Lakes for
one more day. The consensus solution may try to produce a slight chance
pop...but the precipitation chances seem to be dwindling the closer to Friday we
get. Maximum temperatures will range from the lower 70s near Lake Michigan...to the upper
70s over central/E-cntrl WI.

By the start of the weekend...the western Continental U.S. Upper ridge to be in the
process of being flattened by the upper low moving across southern
Canada. This will gradually allow for warmer...more moist air mass
to spread east with time. Another area of hi pressure is expected to
move into the Great Lakes on Sat and bring a dry forecast for the 4th
of July festivities. Maximum temperatures will be near normal which translates
to the lower to middle 70s Lakeside...middle to upper 70s north and near 80
degrees south.

A more pronounced southerly wind is forecast for the latter half of
the weekend as the Canadian upper low (and surface low) reach Manitoba
and a cold front to stretch S-SW toward the central hi plains. Once
again...the consensus model solution may attempt to throw a slight
chance pop into the forecast due to increasing instability. However...do
not see any trigger (fronts...mid-level disturbances...jet
streaks...etc.) To set precipitation off. Thus...NE WI could very well have
a completely dry Holiday weekend. Maximum temperatures should climb a degree or
two above normal with plenty of upper 70s to lower 80s expected (away
from the lake).

Sunday night into Monday appears to be the time period for our next
best chance of seeing shower/thunderstorm activity as the cold front drives east
into the Great Lakes. Timing of the fnt still uncertain at this
time (sunday night or mon)...so will carry medium chance probability of precipitation for both
periods for now. Temperatures should remain near normal until the frontal passage
occurs.
&&

Aviation...for 12z taf issuance
issued at 241 am CDT Tuesday Jun 30 2015

There will be enough lingering low-level moisture for MVFR ceilings this
morning...and possibly some IFR/LIFR conditions with the patchy
fog early. Anticipate ceilings rising into VFR category this afternoon
as lower dewpoints begin to advect into the area.
&&

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

$$

Synopsis.......skowronski
short term.....Skowronski
long term......kallas
aviation.......skowronski

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