Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 310214 AAA
Area Forecast Discussion...UPDATED
National Weather Service Milwaukee/Sullivan WI
914 PM CDT MON MAY 30 2016
Watching thunderstorms that developed over northern and northeast
Iowa in region of 850 mb convergence and moisture transport and
just to the moist side of a fairly strong surface dew point
gradient, and a resulting CAPE gradient. Dew points in southwest
and south central Wisconsin mixed out into the upper 40s and are
still below 50F while dew points jump from the lower 50s to around
60 over a short distance in ne Iowa.
Storms are pulsing as effective shear is under 20 knots making it
difficult to sustain an updraft for an appreciable length of time.
However there have been reports of small hail, and bursts of
stronger winds based on deep inverted V soundings on RAP forecast
soundings, with these storms. However do not feel these storms
will make it too far into the forecast area, if at all, as they
move into the more stable air in place over the area.
HRRR currently has a decent handle on the storms, that may brush
the far western counties between 12 midnight and 2 AM. Hi-
resolution/rapid update models may be too quick in surface
moisture return, accounting for the rapid outbreak of showers and
storms after 2 AM over central and northeast portions of the
forecast area. Pulled back a bit on the PoPS late this evening in
the far west based on current trends but will leave the lower
chance/slight chance PoPs for overnight as is for now.
Expecting VFR conditions through the TAF period except for brief
periods when scattered showers ands storms may affect the
airports. Will continue with vicinity thunder mention within the
most likely time periods when showers/storms could affect any of
the TAF sites until better timing/higher probability of occurrence
can be determined.
Light winds and low wave heights are expected to continue into
mid-week. There will be a slight chance of showers and
thunderstorms overnight tonight through Tuesday, with increasing
chances Tuesday night and Wednesday with passage of a cold front.
.PREV DISCUSSION... /Issued 233 PM CDT MON MAY 30 2016/
TONIGHT AND TUESDAY...Forecast Confidence...Medium
There will be a chance for showers and storms tonight as a wing of
warm air advection aloft lifts through. The best chance will likely
come after midnight. Though winds will be light this evening and
dewpoints fairly low after mixing out this afternoon, increasing
clouds will likely keep temps from getting as low as they might
It looks like there might be a brief break in precip chances from
mid-morning tomorrow into early afternoon. The low level jet will be
increasing overhead in the afternoon though, with some lingering
warm advection aiding in the development of showers and storms. It
looks like the best chance for convection will be across the western
half of the forecast area from mid to late afternoon.
With the cold front remaining well to the west of the forecast area,
temperatures will be warm again Tuesday. Winds will be onshore all
day, so it will be cooler near Lake Michigan. Water temps continue
to warm up though, with mid 50s to around 60 most places per latest
analysis. This will help keep temps from tanking too much near the
TUESDAY NIGHT THROUGH WEDNESDAY...Forecast confidence is high.
No real change here. A decent mid level wave and it`s associated
surface low and cold front will gradually approach the area.
Things have slowed down a bit. A leading piece of energy will
swing north through the area Tuesday night, possibly enhancing
precip chances west of Madison. As the main trough moves in, those
higher precip chances will spread east by Wednesday morning. SPC
has us in a marginal risk for severe and that seems reasonable for
now. The timing of the main forcing/features isn`t lined up with
the best diurnal trends. Therefore the CAPE isn`t optimal. Deep
layer shear is on the order of 30kts. So, can`t rule out some
strong or possibly severe storms, but will likely stay on the
Look for the rain to end in the west by Wednesday afternoon and
that diminishing trend will continue with only a lingering small
chance across the southeast Wednesday evening.
THURSDAY AND FRIDAY...Forecast confidence is high.
High pressure still looks to like it will keep this period dry
with highs in the 70s. The only caveat is that a fast approaching
mid level trough will be diving in from the northwest. The leading
warm advection and could bring a chance of thunderstorms to areas
north of Milwaukee and Madison during the mid or late afternoon.
Saturday through Monday...Forecast confidence is medium.
A rather notable pattern shift occurs during this period. That
mid level wave moving in late Friday will settle over the Great
Lakes and turn into a large and possibly closed off upper low
that takes its time over the region. This would mean a cooler,
cloudier and more showery pattern for the weekend into early next
week. Both the GFS and the ECMWF show this evolution.
VFR conditions will prevail for much of the time through Tuesday.
There will be a chance for showers and storms overnight and again
tomorrow, which may bring some lower visibilities in heavier
Winds will generally remain on the light side into mid week. A
chance for showers/storms will return for later tonight through
TONIGHT/Tuesday AND AVIATION/MARINE...DDV
Tuesday NIGHT THROUGH Monday...Davis