Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 272022
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
320 PM CDT MON MAR 27 2017
.TONIGHT AND TUESDAY - Forecast Confidence...High.
Clouds will remain over southern Wisconsin through Tuesday morning.
A few drops of drizzle are possible during the late afternoon/
evening hours as low pressure tracks to our southeast.
Drier air working its way southward Tuesday afternoon will help to
break up the clouds. It is still questionable about how much
sunshine we will see before sunset. Low temperatures will be in the
mid to upper 30s tonight. Highs Tuesday will be in the 40s near Lake
Michigan and lower 50s inland.
.TUESDAY NIGHT THROUGH THURSDAY - Forecast Confidence...Medium
Differences persist with this mid-week system and have now
encroached into the short term guidance. The GFS is now showing
quite a bit of run to run consistency with this next in a series of
upstream long wave trofs that gets ejected into the central/southern
Plains on Wednesday. At 00Z Thursday, sfc low wl be over the nrn
TX/OK border area while upper level circulation will be around TX
panhandle. By 12Z Thursday, sfc low has progressed northeast into
southern MO/northern AR area while mid-level circulation has moved
into central KS. GFS has adjusted slightly slower and farther south
with mid-level circulation, but still showing good consistency.
Lingering mid-level ridging and drier ely flow has kept bulk of
precipitation over Nrn IL Wed night as low levels remain mostly dry
thru 12Z. In all, GFS carries through Thursday more ely and slower
progression with axis of heavier QPF across nrn IL. This would
result in less rain/snow mix for srn WI both Wed ngt and Thu. This
period on edge of NAM cycle and showing lack of continuity at 12z
Thu from last two runs, so minor contribution from NAM at this
Meanwhile, 12Z ECMWF showing slightly slower northward progression
and trending farther south during the day Thursday. However ECMWF
still shows strong push of low level warm air advection grazing
southern WI later Wed night resulting in more widespread heavier QPF
across srn WI. Also, ECMWF starting to show a stronger split flow
across the Great Lakes with a greater contribution from weaker mid-
level short wave passing through the western Great Lakes on
Thursday. In addition, ECMWF trending downward with QPF. Hence
ECMWF and GFS continue to adjust hopefully toward a general united
solution which will be clearer tomorrow. Thermal structure still
favors a rain/snow mix developing with a period of -sn across the
north later Wed night into Thu mrng.
THURSDAY NIGHT THROUGH MONDAY - Forecast Confidence...Low trending
Uncertainties remain with respect to low pressure system tracking
from the mid-MS Valley region northeast toward the eastern Great
Lakes by Friday night and Saturday. 12Z ECMWF has adjusted slightly
to be more in line with GFS with sfc low taking more southern track
across central IL into wrn OH Thu night while GFS slower and remains
farther south. NH Canadian now outlier and farther north, so will be
discounted for now. Upstream amplifying long-wave trof digging into
the western CONUS should result in this system becoming more
progressive Thu night and Friday. WPC blended guidance leaning
toward slower solution which would have the precipitation threat
continuing into Friday, with a chance for the rain to transition
back to a mix Thursday night into Friday morning. Prefer blend as
well as difficult to pick out preferences for one solution vs
another but ECMWF and GFS converging on similar scenario. GFS
ensembles show fairly good agreement through 18z before diverging on
speed and track of system.
Uncertainties continue over the weekend as to strength of zonal flow
and whether weak mid-level short waves passing across southern
Canada will affect the western Great lakes over the weekend into
early next week, or whether next in a series of ejecting short waves
from the southwest may result in precipitation spreading in from the
southwest by Monday.
.AVIATION (21Z TAF update)...
Ceilings are in the 1000-2000 ft range this afternoon. Areas near
Madison and west should drop back down to IFR for a while tonight.
Light fog will be possible mainly west of Madison overnight.
Dry air will work its way into southern WI from the north Tuesday
afternoon. Expect a trend to VFR cigs and eventual clearing Tue
Extended the marine dense fog advisory once again for areas south of
the North Point Light until late evening when increasing northeast
winds should help to diminish the fog.
Northeast winds and waves will approach small craft advisory levels
late tonight into Tuesday, but expect them to remain just under
criteria so no headline.
LM...Dense Fog Advisory until 10 pm CDT for LMZ645-646.
TONIGHT AND TUESDAY/AVIATION/MARINE...MRC
TUESDAY NIGHT THROUGH MONDAY...MBK