Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Green Bay WI
411 am CDT Sat Apr 18 2015
New information added to update section
issued at 407 am CDT Sat Apr 18 2015
After further coordination with arx and the dnr...will issue a red
flag warning for Wood County. The combo of humidities falling near
20 percent this afternoon...maximum temperatures in the 60s...wind speeds of 10
to 20 miles per hour...and dry fuels will lead to a critical fire weather day
there. This red flag warning will target the Pine country of
Additionally...the cold front has just passed over Green Bay.
Winds have shifted to the north and are gusting to 22 knots at the
grb Airport. Some gusts up to 25 knots over the Bay are also occurring.
Short term...today...tonight...and Sunday
issued at 330 am CDT Sat Apr 18 2015
The latest rap analysis and satellite/radar imagery show a fairly
potent cold front dropping south over far north-c Wisconsin and the
Central Upper Peninsula. North winds behind the front combined with
impressive pressure rises are contributing to wind gusts over 30 kts
over Lake Superior. As the front moves across northern Wisconsin
early this morning...expect north winds to strengthen and become
gusty for period. Elsewhere...upper level low pressure continues to
spin over the central rockies and produce showers and thunderstorms
across the central Great Plains. Forecast concerns include fire
weather parameters today...and precipitation chances on Sunday.
Today...the dry cold front will drop south across the rest of
northern Wisconsin early this morning and central Wisconsin by
mid-morning. Behind the front...the models are still depicting very
dry air to move into north-central to east-central Wisconsin today.
Though northeast winds off Lake Michigan will help moderate the dry
air over eastern Wisconsin...modest wind speeds should be able to tap into
this very dry air just above the inversion...around 900mb. So was
aggressive in dropping humidities today...which should fall into the
teens over north-c Wisconsin and to around 25 percent over central
Wisconsin. East winds will also be approaching critically sustained
speeds over central Wisconsin this afternoon. Still waiting for a
final decision from the dnr concerning a red flag warning...which should
have by 5 am. Otherwise...will see a sunny and cooler day. Highs
in the low to middle 60s away from Lake Michigan.
Tonight...clouds will be on the increase as the central rockies
upper low moves across the Central Plains...while a northern stream
wave digs over the northern plains. As clouds thicken and
lower...winds below 900mb will remain out of the southeast and
continue to advect very dry air over the region. This dry air will
have to be overcome...and this may not occur until late in the night
over the west. Will modify precipitation chances slightly to reflect this.
Lows ranging from the middle 30s north to the middle 40s southwest.
Sunday...mid-level height falls will continue to advance into the
western Great Lakes. One area of low pressure will move into
western Wisconsin during the afternoon...while a southern stream low
swings NE towards the southern tip of Lake Michigan. Forcing will
improve through the day ahead of these features...though the lead band of
light rain may decay during the morning as a result of the dry low
level flow. Then a second round of precipitation may try to move into the
area with the approaching low pressure systems. Temperatures are difficult
because of the precipitation potential...ample cloud cover...and east
winds. Have dropped temperatures some since temperatures do not typically rise
well when there is cloud cover and east winds. Precipitation will also
likely hold temperatures back over central and north-central Wisconsin. So
went with highs ranging from the middle 50s north to low 60s south.
Long term...Sunday night through Friday
issued at 330 am CDT Sat Apr 18 2015
500mb trough will evolve into a closed upper low over the western
Great Lakes region early next week...then meander across eastern
Canada and the Great Lakes region through the end of next week.
This will lead to cool and unsettled conditions...along with a
chance of snow late at night and early morning hours.
Rainfall totals still problematic Sunday night as two separate
systems will bring rain to the area. Northern stream system will
bring rain to the western half of the state...meanwhile a fairly
potent low pressure system will move northeast into the Great
Lakes region Sunday night. Still a lot of questions on track of
system due to closing upper low northwest of the state. Model quantitative precipitation forecast
would suggest that much needed rain would fall across the region.
Main question is where axis of heavier rain would fall. Model
run to run continuity has not been consistent...thus low confidence
in the rainfall amount forecast. Monday is not much clearer as some
of the models bring dry slot across the area with a significant downward
trend in rainfall amounts. The European model (ecmwf)/Canadian do not share this trend
with the WRF/GFS...thus will keep scattered depiction/wording in
As upper low closes Monday night through Wednesday...cool cyclonic flow
and weak disturbances moving through the mean flow will bring
chances of rain and snow showers depending on location and timing
of the day. At some point...there could be a minor accumulation of
snow across the north. Some moderation in temperatures is expected by
the end of the week as the upper low gradually shifts east of the area.
Aviation...for 06z taf issuance
issued at 1100 PM CDT Friday Apr 17 2015
VFR conditions expected through the taf period. A dry cold front
will arrive later tonight. Winds will shift to the northeast behind
the front...and become gusty for a few hours today...especially in
eastern Wisconsin. Winds will die down again Saturday evening with
thickening middle clouds.
red flag warning from 11 am this morning to 7 PM CDT this
evening for wiz035.