Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 101107
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
507 AM CST Tue Jan 10 2017
.TODAY AND TONIGHT...Forecast Confidence High
Issued a Winter Weather Advisory until 10 am given current mixed
precipitation which includes freezing rain. Surface temperatures are
already above freezing from Madison to Milwaukee and south but
pavement temperatures are in the upper 20s at this time. The surge
of warm advection will boost surface temps to 35-40 degrees by 10 am
with road temps likely above freezing by then. The coverage of
precipitation will increase through the morning as warm, moist
advection increases ahead of strong cyclogenesis. The deepening low
will track from the Middle MO river Valley to sw WI by 18z to ern
Upper MI by 00z. The low will deepen to 983 mb by 00z with pressure
rises of 16-20 mb/6 hours late today into the evening. In addition,
steepening lapse rates with the strong cold advection will support
wind gusts from 45-55 mph. Thus a Wind Advisory has been issued for
3 pm today until midnight. The rain will change to light snow mainly
north and west of the Milwaukee area this afternoon but snow
accumulations will remain under one inch.
.WEDNESDAY AND THURSDAY...Forecast confidence is medium.
Upper level jet axis shifts from central Wisconsin towards southern
Ontario on Wednesday in response to amplifying troughing upstream
over the upper Missouri valley. This trough will dig equatorward
while progressing into the upper Mississippi valley on Thursday.
Southern stream energy will be drawn northeastward from the Great
Plains into the eastern Great Lakes, but does not appear to fully
phase with the larger scale trough until beyond this period. The
surface reflection of the upper level features will be the
northeastward progression of inverted troughing from the central
Great Plains on Wednesday into the lower Great Lakes on Thursday.
Light snow could clip northern portions of our area by Wednesday
afternoon with warm advection and modest frontogenesis response
preceding the arrival of the weak surface low/inverted trough. Any
accumulations during this time should be on the light side, on the
order of one half inch or less.
Things get a bit more complicated with respect to precipitation
types Wednesday evening and night, with subfreezing surface
temperatures and warm air nosing into our southeast around 850 mb.
This places southern Wisconsin in the transition zone, with snow
most likely in our northwest, transitioning to a mix and snow across
central areas, and potentially to light freezing rain in our south
and east. What`s different from last night`s model runs is an
apparent decrease in the warm layer depth among some of the
guidance. This could bring less freezing rain to our southeast with
a bit more sleet or snow if this trend holds. GFS forecast soundings
are suggestive of this on Wednesday night, while NAM soundings hold
steady with a freezing rain profile. This, in addition to a slight
decrease in QPF, introduces some uncertainty with regards to icing
amounts and impacts, but will hold steady for now with the idea of
some light accretion in the south and east of up to 0.10 inches.
Storm total snow amounts of around one inch are expected in our
north, tapering off to a trace along the Illinois border. Any
lingering precipitation should come to an end by late Thursday
.THURSDAY NIGHT THROUGH MONDAY...Forecast confidence is medium.
No significant changes to the forecast for this period. Still
expecting cold temperatures under arctic high pressure on Thursday
night into Friday with warming temperatures for the weekend. Low
pressure will bring precipitation chances for the weekend into early
next week, but low confidence on timing and potential snow amounts
until models come into better agreement.
Mixed precipitation this morning will give way
to all rain by 10 am. Cigs will fall below 1 kft for the day with
vsbys mostly ranging from 2-5SM. The rain will change back to light
snow briefly north and west of Milwaukee later this afternoon. A
strong cold front will then bring a wind shift to the west by the
middle to late afternoon. Wind gusts of 45-55 mph is forecast from
late afternoon into the early evening. VFR conditions will develop
by early evening as the strong cold advection dries out the low
layers and ends the precipitation.
A Small Craft Advisory is in effect until 3 pm for breezy sly winds
and high waves in ice free areas. A strong cold front will then pass
with wly gales developing by middle to late afternoon. Wind gusts up
to 45 knots are forecast into the evening. A Gale Warning is in
effect from 3 pm today until 3 am Wed.
WI...WINTER WEATHER ADVISORY until 10 AM CST this morning for WIZ046-
WIND ADVISORY from 3 PM this afternoon to midnight CST tonight
LM...SMALL CRAFT ADVISORY until 3 PM CST this afternoon for
GALE WARNING from 3 PM this afternoon to midnight CST tonight
GALE WARNING from 3 PM this afternoon to 3 AM CST Wednesday for
TODAY/TONIGHT AND AVIATION/MARINE...Gehring
Wednesday THROUGH Monday...SPM