Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 190832
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
232 AM CST Sun Feb 19 2017
.TODAY and TONIGHT - Forecast Confidence...High
Forecast soundings again show very dry boundary layer air with
only the surface temperatures cooling to the dewpoint. Patchy fog
until just after sunrise, then quick warming. Record highs again
in danger, especially inland. However east winds will develop over
southeast Wisconsin and lake breeze will cool inland areas much
more then previous days.
With the upper ridge and increasing upper divergence later today
and tonight, high clouds will be on the increase.
With south flow and increasing moisture fog will be more of a
concern late tonight.
.MONDAY AND TUESDAY...Forecast confidence is high.
There is good model agreement in lifting a shortwave trough
across the upper Midwest and western Great Lakes on Monday and
Tuesday. Surface low pressure will accompany the upper wave as it
tracks from the Dakotas into Manitoba. The associated warm front
will lift northeast through the area on Monday, with a surge of
warm moist advection in the low levels. Precipitable water values
climb to an anomalously high 1.2 inches, which is around 400
percent of normal, and is above the record high daily max for both
GRB and DVN. This provides support for increasing average
rainfall amounts to around 0.5 inches for southern Wisconsin with
this system. Didn`t feel comfortable going higher than this, given
only modest frontogenetic forcing producing weak to moderate
ascent as the cold front pushes through. Some timing differences
exist among the deterministic guidance, with the GFS quicker to
bring the precipitation through Monday afternoon into early Monday
night. The ECMWF is a bit slower with the upper features, owing
to more interaction with a closed low crossing the southern U.S.
This model`s solution brings the precip in Monday evening before
ending it Tuesday morning. The NAM and Global Canadian solutions
appear more in line with the ECMWF, so am favoring a slower
evolution for the precipitation. There could be a rumble of
thunder or two given the few hundred Joules of elevated CAPE
present on area forecast soundings. Model RH progs suggest
clearing skies by mid afternoon on Tuesday as the front departs.
Temperatures will remain unseasonably mild, with near record to
record highs. The Lakeshore areas will be a bit cooler with
onshore flow on Monday.
.WEDNESDAY AND THURSDAY...Forecast confidence is medium.
Look for zonal flow aloft on Wednesday, with a compact shortwave
sliding east along the International Border. This wave will escort
a weak surface low, whose cold front pushes through Wednesday
afternoon or evening. The Global Canadian tries to generate some
light QPF with the frontal passage, but other models are dry. Mild
temperatures are expected during the day, with cooling overnight
behind the front.
The upper flow pattern transitions to southwesterly on Thursday
in response to broad troughing over the Intermountain West and
Four Corners regions. Strong cyclogeneis will occur along the
Front Range, with the surface low quickly deepening to around 985
to 990 mb over KS/NE by evening. While mid to upper moisture will
increase Thursday afternoon and evening, the latest forecast
models delay the low-level moisture surge as the warm front
remains stalled to our south over northern or central Illinois.
Have trended a bit cooler for temperatures on Thursday, although
we`ll remain well above seasonal averages. The GFS tries to
generate some light rain showers or sprinkles over our area during
the afternoon and evening, but other model solutions are dry.
.THURSDAY NIGHT THROUGH SATURDAY...Forecast confidence is low.
There is good general agreement in ejecting the broad western
trough the central Great Plains/mid Mississippi valley on Friday
and into the central Great Lakes on Saturday. The ECMWF and
Canadian models hold steady with the idea of carving out a closed
low and bringing it through our area on Friday, while the GFS is
coming in weaker with an open-wave trough. This leads to some
differences in where the low-level baroclinic zone sets up which
will be traversed by the strong surface low. The current consensus
track would bring the low from the central Great Plains to
somewhere in the vicinity of southern Wisconsin/northern Illinois
on Friday. This track introduces more uncertainty in whether
southern Wisconsin is solidly in the warm sector with this system.
Will lean towards the more consistent ECMWF solution which brings
enough warm air for mostly rain on Friday, with a transition to
light snow Friday night or Saturday morning before the
precipitation ends. There is lower than usual confidence in
precipitation types on Friday and Saturday due to model
variability. Cold air wrapping in behind the low will bring our
temperatures closer to seasonal averages for Saturday.
A few areas of ifr vsbys in fog through just after sunrise in low
areas and river valleys. otherwise VFR conditions are expected.
High clouds will be on the increase today and especially tonight.
With south flow and increasing moisture ifr fog will be more of a
concern late tonight.
Winds and waves are expected to remain below Small Craft Advisory
levels through tonight. More of an east flow developing later
this morning and afternoon. Southeast winds increasing a little
Southeast winds and waves may reach Small Craft Advisory levels
Monday into Monday night, and become southwest, as a tight
pressure gradient develops ahead of a trough moving through the
Record highs for Milwaukee and Madison are as follows...
LOCATION SUN/19TH MON/20TH TUE/21ST WED/22ND
Milwaukee 59 (1981) 60 (1930) 58 (1930) 62 (1984)
Madison 60 (1981) 57 (1930) 57 (1984) 60 (1984)
The average highs during this period are 34 at Milwaukee, and 33
TODAY/TONIGHT AND AVIATION/MARINE...Hentz
Monday THROUGH Saturday AND CLIMATE...SPM