Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 091735
AFDMKX

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
1135 AM CST Sun Dec 9 2018

.UPDATE...

Starting to see some slight scattering out of the stratus, though
progress is slow. Still think we will some some sun peak through
by late afternoon, and similar to last night, have some clearing
during the evening hours before clouds redevelop. Overall
confidence is quite low, however.

With most sites still in the low 20s, have adjusted highs to top
out in the upper 20s.

&&

.AVIATION(18Z TAFS)...

IFR stratus is expected to scatter out briefly late this
afternoon, but redevelop tonight into Monday morning. Along with
IFR ceilings, light fog/freezing fog will be possible late tonight
and early Monday, similar to what was seen today. IFR will then
persist into Monday morning before a slow improving toward MVFR by
mid day. Overall confidence in trends, especially with respect to
ceilings, is quite low.

Winds through the period will range from light from the west to
light and variable.

&&

.PREV DISCUSSION... (Issued 919 AM CST Sun Dec 9 2018)

UPDATE...

Another day, another challenging batch of cloud cover. This
morning`s low stratus looks to be very thin, and forecast
soundings suggest that we should see some scattering out by
afternoon. We`re already seeing a few holes form, and this may be
the beginning of this process. However, suspect that we`ll see the
clouds reform to some degree later tonight. Made some adjustments
to sky cover to account, but overall confidence remains low.

Will also need to watch highs for today, as the clouds may knock a
few degrees off of expected max Ts. Initial forecast was for low
30s, but upper 20s may be more common.

MARINE...

The strong high that has been over the area for the last few days
will push into the northeastern US today. Surface high pressure
will still be in place over the southern Great Lakes through mid
week, but will be an overall weaker area of high pressure.

Low pressure over James Bay will push east today as well, with
weak troughing remaining over much over central Ontario into
Quebec the next few days. In combination with the aforementioned
area of high pressure, this will keep steady west to northwest
winds across much of the lake.

A more active weather pattern looks to affect the Great Lakes by
mid week, but there is considerable uncertainty with how things
will play out. Higher winds and waves will be possible during this
time, however.

AVIATION(12Z TAFS)...MVFR stratus deck expanding more south and
east into the cwa. RAP soundings/925 RH progs show that some of
this may mix out during the afternoon. High pressure dominates
into Monday with an overall quiet wx regime.

PC

PREV DISCUSSION... (Issued 330 AM CST SUN DEC 9 2018)

SHORT TERM...

Today and Tonight - Confidence...Medium to High.

High pressure continues to be the dominating influence. Swirl of
clouds in SD reflective of mid level circulation that progs drop
south and leave mid level anticyclonic flow in place our area
this period. Based on satellite trends the main stratus area will
likely affect the northern two tiers of counties this morning with
some further southward expansion not out of the question. Another
area earlier brushed the Lake MI shoreline, but this has trended
much further offshore. So expecting a good deal of sunshine today
especially in the southern cwa. The main stratus area looks like a
morning issue in the north with more sunshine there this afternoon.
MOS temps look pretty good though leaned a smidge towards the warmer
numbers of the GFS MOS given expected sunshine. Quiet tonight with
the high in place and temps should drop off into the teens for
most.

MONDAY THROUGH TUESDAY NIGHT...Forecast Confidence - Medium to
High.

Quiet conditions to continue this forecast period.  Northwest
steering winds across the region will carry a potent short wave
across the northern Great Lakes Monday night and early Tuesday.
However any synoptic lift with this feature will remain
well north of southern WI.  Northwest steering winds back to the
west for Tuesday as low level temperatures warm slightly.  The low
to mid-levels look to remain dry, however stratus that may develop
upstream over the IA/MN area closer to the deeper snowfield and
better low level convergence, may get pulled east into southern WI
at times.  This is the main forecast concern, but for now, remaining
more optimistic with clear to partly cloudy conditions forecasted
for much of the period.  Increasing clouds look most likely Tuesday
night ahead of approaching low pressure trof and increasing
baroclinicity.  Went with daytime temps warming into the 30s both
days, with the warmest temps on Tue, provided limited opaque cloud
cover.  Kept northwest CWA slightly cooler due to lingering snow
field.

LONG TERM...

WEDNESDAY THROUGH SATURDAY NIGHT...Forecast Confidence - Low to
Medium.

Significant variability taking place in the Medium Range Guidance
for sensible weather across southern WI through this period, so
confidence remains lower.  Solutions show considerable variability
regarding short wave trof moving through the western CONUS through
Tuesday, with upstream kicker mid-level wave close on it heels.
Would think this would result in more progressive scenario, however
last several ECMWF runs trending toward rapidly strengthening
central plains mid-level low pressure Tuesday night into Wednesday.
GFS and GEM remain more with an open wave, and that appears to be
the trend WPC blended guidance is going, however with below average
confidence as well.  WPC relying more on ECMWF ensembles and GEM.
Never the less, will continue chance Pops for Wednesday at this
time, with mostly light snow developing in the morning,
transitioning to a mix in southern areas for now. Can not rule
out light accumulations, especially in northern areas on
Wednesday into the evening.

Low confidence continues for later periods as well.  Above mentioned
second short wave looks to amplify as it progresses as it moves into
the central CONUS on Thursday.  However ECMWF showing split flow
developing with northern stream remaining more progressive
across the region, while low pressure deepens over the southern
Plains Thu night into Friday.  GFS shows less split flow, and takes
this system farther north and eventually into the TN Valley
Friday night/Saturday, which potentially could graze southeast WI
with a period of light precipitation.  GEM trending toward GFS
and more northern solution.  WPC discounting more aggressive GFS and
again using a ECMWF ensemble/GEM blend with low confidence.  Will
need to carry chance pops for Thu/Fri as the track and strength of
this system is far from certain.  One consolation is that the trend
toward a more zonal to WSW steering flow and near to perhaps above
normal temps continues for at least the first part of the week of
16th. So no bitter cold on the horizon for now.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...None.
LM...None.
&&

$$

Update...Boxell
Today/Tonight and Aviation/Marine...Boxell
Monday THROUGH Saturday...99


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