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Area forecast discussion 
National Weather Service Green Bay WI
1027 PM CDT Sat Apr 19 2014

Updated aviation portion for 06z taf issuance

Short term...tonight and Sunday
issued at 252 PM CDT Sat Apr 19 2014

Rain chances and timing are the main concerns in the short term.

Dry air across the forecast area will need to be displaced before
anything more than sprinkles can get started. 12z grb sounding was
dry below 700mb and surface dew point depressions were around 20f
degrees in most locations.

A closed 500mb cyclone is expected to move from Manitoba at 00z
Sunday to James Bay by 00z Monday. Flow at 500mb looks Pretty Flat
across Wisconsin. Upper divergence associated with a 300mb jet and
40 plus knot 850mb jet into north central Wisconsin are expected
to bring rain chances there for late afternoon/early evening.
Convergence with an approaching cold front will provide the focus
for rain across the rest of forecast area tonight into Sunday.
Models showed a band of higher relative humidity moving through the state tonight
and Sunday while the 12z NAM 700mb qvectors showed an band of
strong convergence passing through the area.

There was some surface based cape around 500j/kg in northern
Wisconsin evident on the 12z NAM and middle level lapse rates looked
pretty marginal for thunder so have not added it to the
forecast...though it may need to be added tonight or on the
midnight shift if conditions appear more favorable. Kept areas of
fog in north central Wisconsin tonight with higher relative humidity air passing
across the deep snow pack there.

Kept pretty close to the previous forecast...combining it with a
blend of some of the best performing guidance...for lows tonight
and highs on Sunday.

Long term...Sunday night through Saturday
issued at 252 PM CDT Sat Apr 19 2014

Little change in the going forecast at this time. Two main
periods of precipitation to focus on. Sunday night into Monday
evening and again later in the week starting Wednesday afternoon
or evening.

Focus of any precipitation starting out Sunday evening will be
along or near a west to east boundary prognosticated to stretch over
central Wisconsin. Besides weak surface convergence and limited
moisture...appears little support at the onset. Later at
night another short wave trough works into the state to provide
lift. Rrq of an upper jet slides over Monday to continue to support
showers before the frontal passage shifts east Monday night.

High pressure to dominate over the region Tuesday through most of
Wednesday before the next frontal system is prognosticated to approach
the region from the central and northern plains.

At this time models in general agreement with lifting a warm front
northward over the western Great Lakes region Wednesday night followed
with a cold front passage Thursday afternoon into Thursday night.
Will focus any thunderstorm mention with the fronts at this
time...particularly the cold front with total totals approaching
the lower 50s late Thursday afternoon. Todays runs are also suggesting
a dry slot working over the state later Thursday night before wrap
around precipitation works back over the state on Friday.
&&

Aviation...for 06z taf issuance
issued at 1025 PM CDT Sat Apr 19 2014

Showers slowly sagging southward across the area. Ceilings and visibilities have held
up well thus far...but as low-levels get closer to saturation will
probably have some lower ceilings and fog develop. Will continue to attempt
to highlight the most likely period for precipitation in the tafs...though
it/S tough to totally rule it out tomorrow.
&&

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

$$

Short term.....Mg
long term......tdh
aviation.......skowronski