Scientific Forecaster Discussion
fxus63 kmkx 200910
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
310 am CST Wed Nov 20 2019
Today...forecast confidence is moderate.
Not seeing much in the way of dense fog over the advisory area
early this morning, per observations and web cameras. Think
that low stratus field is helping prevent visibility values from
dropping more into the 1/2 to 1/4 mile range. There have been a
few sites, mainly south and west of Madison, that are/were
showing some dense fog.
After collaboration with neighboring offices, will continue the
dense fog advisory until 15z this morning. There may be some more
dense fog that develops around sunrise. If things do not
materialize by then or soon after, may end up canceling the
The low stratus should linger this morning, before ceilings mix
upward this afternoon. Skies should remain cloudy today. Some warm
air advection develops over the area today as well. Highs are
expected to reach the middle 40s across the area, which is near
seasonal normals for highs.
Tonight and Thursday...forecast confidence is high.
Models are in decent agreement with low pressure moving northeast
from the Central Plains to north Central/Northeast Iowa tonight.
The low then shifts across southwest to east central Wisconsin
Thursday morning, into Northern Lake Huron Thursday afternoon.
Southwesterly low level jet will bring plenty of deep column
moisture into the area by later tonight into Thursday morning,
with warm air advection continuing in the warm sector over the
area. Thus, look for a non-diurnal temperature trend for tonight
into Thursday morning, with temperatures rising from the upper
30s to the middle 40s tonight, and into the lower 50s Thursday
morning and midday.
The cold front will push through the area mainly in the
afternoon, with decent low level frontogenesis response. A decent
500 mb vorticity maximum will push through the area as well, with
differential cva helping with upward vertical motion. Could see a
few claps of thunder with the cold frontal passage Thursday
afternoon, with very weak elevated cape on forecast soundings.
Continued with high pops for mainly later tonight into Thursday
morning. Thermal profiles will support all liquid precipitation
across the area.
Model certainty shows precipitation amounts in forecast are on the
high end of the model guidance, around the 90th percentile. Wpc
quantitative precipitation forecast is close to this as well. Given the strength of this system
and the feed of moisture moving into the area, feel these rainfall
amounts are reasonable. May see rises in some area river stages
to near flood stage in the coming days from this round of rain.
Friday through Monday...forecast confidence is high.
This will be a beneficial stretch of dry weather to drain off the
rain from tonight and Thursday. In addition, it's the start of the
big Deer Hunt across the state. The mid levels look somewhat
noisy with short waves moving through, but the atmosphere is dry
and should prevent any organized precip development. We should get
into a little sunshine on Friday, but it looks like a mix of
clouds and sun over the weekend. High temps will start out in the
mid 30s on Friday, modifying a few degrees each day into early
next week. Winds will also remain on the light side for this time
Tuesday and Wednesday...forecast confidence very low.
The long range guidance continues to suggest an amplified and
impactful storm system moving into the region by late Tuesday into
Wednesday. This guidance had been in reasonable agreement...until
now. The 00z operational run of the European model (ecmwf) completely flipped and
looks 180 degrees out of phase with the GFS. The GFS shows a 985mb
low moving through Wisconsin Wednesday morning, while the European model (ecmwf)
shows ridging. Looking at the individual ensemble members of the
GFS and the European model (ecmwf) shows a huge spectrum of possible solutions. The
mean of the GFS ensemble has the low tracking south of Wisconsin.
Thus, confidence is low on any solution at this point.
Aviation(09z taf updates)...
Visibility values should generally be in the 1 to 3 mile range
over most of the area into the middle morning hours, with values
of 5 miles or greater near Lake Michigan. Some dense fog with 1/4
to 1/2 mile visibility values may occur at times south and west of
Madison until after sunrise. VFR visibility values will return by
midday over the area.
Low stratus clouds down to 500 feet or so should linger into the
middle morning hours across most of the area, with MVFR/VFR
ceilings possibly lingering near Lake Michigan. Ceilings should
gradually rise to MVFR then VFR during the late morning and early
afternoon. Light winds will become southeast by afternoon.
Low pressure moving northeast into the region will bring a round
of rain into the area, mainly later tonight into Thursday.
Ceilings and visibility values will drop into the IFR/LIFR range
during this period.
Gusty south winds will develop later tonight into Thursday,
becoming west/northwest behind the cold front by later Thursday
afternoon. Some low level wind shear is possible later tonight
into Thursday morning, with 2000 foot level winds southwest at 40
to 50 knots.
Light winds this morning will become moderate southerly winds
toward evening as a strong low pressure system organizes over the
Central Plains. South to southeast winds will increase rapidly
this evening with a Small Craft Advisory going into effect at 9 PM
for the nearshore waters. The strong low will track across central
Wisconsin on Thursday. A gale watch has been posted for the open
waters of Lake Michigan beginning at 6 am Thursday and it will run
through 3 am Friday morning. There will be a brief lull in the
winds as the associated low pressure trough moves through the
area. However, the northwest winds on the back side of the
trough/low will likely increase to gale force levels by early
Thursday evening. The low exiting quickly to the northeast will
bring diminishing winds by sunrise Friday morning. High pressure
settling across the area will result in light winds across Lake
Michigan by Friday afternoon. West to southwest winds of light to
only moderate intensity will then persist into early next week.
WI...dense fog advisory until 9 am CST this morning for wiz046-047-
Lm...gale watch from Thursday morning through late Thursday night for
Small Craft Advisory from 9 PM this evening to 6 am CST Friday