Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 231646 AAA
Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
1146 AM CDT SUN OCT 23 2016
Low pressure will slide east southeast across central and south
central Wisconsin this afternoon, with a cold front sliding
southeast through the area. Potent 500 mb vorticity maximum over
far northwest Wisconsin will slide southeast through northern and
east central Wisconsin this afternoon. Differential cyclonic
vorticity advection pushing southeast and clipping the
northeastern portions of the area should help bring clouds into
those areas by later this afternoon.
Forecast soundings are showing a little more depth to the
moisture in the low levels. However, the mesoscale models are
keeping most precipitation northeast of the area. Synoptic models
have backed off on QPF in the northeast counties compared to
their runs from yesterday. Will keep dry forecast going in the
The clouds should reach about the northeast half of the area by
early evening, lingering until moving off to the east later
tonight. Tightening pressure gradient south and west of the low
will bring gusty winds to southern and western portions of the
area by middle afternoon, becoming northwest to north and gusty
everywhere by early evening, as the low moves away. These winds
will weaken with a weakening pressure gradient by later tonight.
High pressure building into the region from the northwest later
tonight into Monday should bring quiet weather, with mostly clear
skies and light winds. Mild temperatures well into the 60s today
are expected, with cold air advection tonight into Monday bringing
Low pressure and a cold front will pass east southeast through the
area this afternoon. VFR category clouds will slide southeast into
TAF sites by late this afternoon, lingering into this evening
before moving off to the east. Any shower activity should remain
northeast of the area later this afternoon and early this evening.
Mostly clear skies are expected later tonight into Monday.
Gusty southwest to west winds will develop across TAF sites by
middle afternoon, veering northwest to north by early this
evening. Gusts of 20 to 25 knots are possible during this period.
Winds will weaken later this evening and overnight, as high
pressure moves into the region. Light winds are expected on
A Small Craft Advisory has been issued, from North Point
Lighthouse to Winthrop Harbor Illinois, from 4 pm CDT today until
6 am CDT Monday. Breezy wly winds will develop ahead of an
approaching cold front late this afternoon. The winds will then
veer northerly with the passage of the cold front and remain
gusty into the evening hours.
It is possible the Small Craft Advisory may need to be expanded
north, as winds there may gust high enough later this afternoon
into tonight. High waves will build mainly south of North Point
.PREV DISCUSSION... /Issued 336 AM CDT SUN OCT 23 2016/
TODAY...Forecast Confidence Is Medium.
Short wave trough and compact 500 mb vorticity maximum over North
Dakota will move southeast across northern Wisconsin this morning
and afternoon, reaching west-central lower Michigan by 00Z Monday.
The associated surface low will track farther south, moving
southeast from near MSP at 12Z across the state this morning and
afternoon to western Lake Erie by 00Z Monday, with a trailing cold
front reaching the IL/WI border area around 00Z.
Matching current area radar returns with SPC mesoanalysis fields
indicates showers in northern MN are tied closely to compact and
strong area of 700-400mb differential cyclonic vorticity advection
along with deeper column moisture reflected in higher mid-level RH,
which given the expected track of the vort max would keep showers
north of the CWA. ECMWF and NAm are clipping the far ne corner of
the CWA with light showers between 18Z and 00Z, but lack of deep
moisture would indicate no more than a few sprinkles and confidence
too low to mention at this time. Pre-frontal sun and warmth will
raise high temperatures into the mid-upper 60s by early this
TONIGHT...Forecast Confidence Is High.
Clearing skies and cold advection, with 925 mb temperatures dipping
to between 2C and 4C will produce low temperatures in the mid to
upper 30s, with enough surface wind to produce enough mixing to
prevent temps from going lower.
MONDAY - Confidence...High
A large surface high will dominate. The 500 millibar regime shows
building heights in an increasing anticyclonic northwest flow.
Coolest 850/925 temps are proggd to be in the northeast cwa with a
slow erosion of the low level thermal trough.
MONDAY NIGHT - Confidence...Medium
Lingering influence of surface ridge axis combined with clear skies
should allow for temps to drop off into the early/mid evening
before mid/high clouds increase per 300-500 rh progs. So went with
a non- diurnal temp trend. If window of time increases between
evening drop and when clouds arrive confidence will be boosted for
inclusion of frost into the grids.
TUESDAY - Confidence...Medium
LLJ axis remains to our west with lingering dry low levels likely to
be a bit stubborn to erode especially given the better moisture
influx to our west. Have kept some higher POPS in our west in the
afternoon to account for the GFS scenario. However the 00z ECMWF
keeps the qpf largely out of the cwa. If the ECMWF trends hold we
will be able to scale back the POPS in the east from what Superblend
currently has going. It does look like the GFS is developing too
much precip too far east into the lingering ridging especially
given the late day position of LLJ well to the west.
TUESDAY NIGHT AND WEDNESDAY - Confidence...Medium to High
Best combo of synoptic forcing and moisture influx overlap as 500
millibar shortwave arrives and 850 llj translates towards eastern
WI. This will aid in moisture transport into our area. Seeing some
influence from right rear quadrant of departing upper jet max
through the eastern Lakes region. Still some differences on the
track of surface low with the ECMWF bringing the low into srn WI and
while the GFS has it across central IL. So the ECMWF has a more
northward placement of the qpf max. So POPS continue on the high
side and some heavy rain totals (highest in western CWA) still look
reasonable so have retained this mention in the HWO.
THURSDAY - Confidence...Medium
The GFS has trended away from last nights cutoff scenario and
has trended more in line with the progressive ECMWF solution. However
the ECMWF is slower to completely shift the mid level trough axis
east of WI relative to the GFS. So some lingering shra chances are
still in place across mainly eastern WI.
FRIDAY - Confidence...Medium
Surface high gradually builds in though lingering surface
trough and perhaps some upper support may generate some light shra.
POPS pretty low at this time.
SATURDAY - Confidence...Low
Fairly large differences between GFS and ECMWF with the GFS showing
the high dominating though a band of qpf developing and merging with
precip to our south associated with next low/baroclinic zone.
However the ECMWF shows a more pronounced 500 millibar trough
arriving with a more northward positioning of more organized shra
into WI versus the GFS focus more to the south of WI. For now will
go with the blended guidance.
AVIATION/12Z TAFS/...Patchy fog will dissipate by mid morning with
clear to sct sky cover and VFR conditions until a VFR cloud deck
overspreads the area with approach and passage of low pressure
late this morning and afternoon. South to southwest winds will
shift northwest and increase to 10 to 20 knots behind a trailing
cold front that reaches the WI/IL border around 00Z Monday. Winds
will ease tonight with VFR conditions through the remainder of the
MARINE...A tightening surface pressure gradient around approaching
low pressure will not affect the nearshore zones with higher winds,
and thus higher waves, until the low passes by and a cold front
drops through the area late this afternoon/evening. Winds and waves
are marginal for a Small Craft Advisory so will add a cautionary
statement for small craft in this NSH issuance and let next shift
assess need for a headline.
LM...SMALL CRAFT ADVISORY from 4 PM this afternoon to 6 AM CDT Monday
TODAY/TONIGHT AND AVIATION/MARINE...REM
Monday THROUGH Saturday...Collar