Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
FXUS63 KMKX 231448
Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
948 AM CDT Thu Mar 23 2017
With high pressure departing to our east and low pressure
developing over the western plains, we remain firmly within a
region of WAA. There is mid-level moisture in place, as evidenced
by the widespread cloud deck and weak echoes showing up on radar.
However, the low levels remain quite dry, and we`re only getting
isolated reports of light precip reaching the ground via mPing.
In fact, we`re even seeing some breaks in the clouds in the SW
CWA in between departing mid level moisture and some incoming
lower level moisture.
Model RH fields seem to have a reasonable handle on the situation
in the lower levels, and match up well with both visible satellite
trends and the low level WV imagery from GOES 16. Good agreement
that the lower levels will gradually fill in from the west later
this morning and afternoon, but the lowest levels will not
saturate until late this afternoon or this evening, so may have to
further trim back PoPs today.
Winds have already ramped up to 24 knots at Kenosha, so decided to
push the SCA up an hour in the south. Still on track to reach
20-25 knots across all near shore areas within the next few hours,
so the SCA remains unchanged otherwise. Winds will begin to
gradually weaken this evening as the pressure gradient slackens.
As low pressure approaches the region tomorrow, the pressure
gradient will tighten back up, ramping the winds back up to the
15-20 knot range, perhaps exceeding the 20 knot mark in the
south. An additional SCA does not seem likey at this point, but it
remains a possibility.
.PREV DISCUSSION... (Issued 616 AM CDT Thu Mar 23 2017)
AVIATION(12Z TAFS)...Mid level clouds will gradually lower to
3-5 kft Cigs for tonight. Small chances for showers and isolated
tstorms late this afternoon and tonight. LLWS is likely
tonight given a swly LLJ of 60 kts.
PREV DISCUSSION... (Issued 326 AM CDT Thu Mar 23 2017)
Today and Tonight...Forecast confidence medium.
Ssely flow and warm advection will continue for this period. The
warm, moist advection in the middle levels will result in only
clouds for this morning. Better 850 mb moisture will arrive late
this afternoon into the evening when a strong LLJ arrives. Some
elevated CAPE noted on forecast soundings but best focus for lift
via frontogenesis is across nrn and central WI. Also some dry areas
remaining on the soundings. As the LLJ veers, drier low level air
attempts to advect into the area. Thus, only chances of rain for
late today and tonight along with slight chances of tstorms.
FRIDAY - Confidence...Medium
Large 500 millibar low in the Central Plains will plod ENE. 850/925
baroclinic zone will be laid out to our north with the better
frontogenetical forcing with precipitation tied to this boundary.
The surface front is proggd to shift south during the afternoon and
shift winds to the northeast. A northwest to southeast gradient in
POPS looks reasonable. The bigger question will be the temps. If the
warm sector plays out like the NAM where 925/850 RH is drier looking
than the temps could get even warmer than the Superblend suggests.
In fact the Superblend is already warmer than the MOS and this looks
reasonable at this point. However if surface front accelerates
that would cut off any warming quicker, especially near the lake,
so inland and further south areas in the CWA appear to have the
better shot at the warmest temps. May make some additional upward
adjustments in these locales.
FRIDAY NIGHT THROUGH SUNDAY - Confidence...Medium
A wet and unsettled period as upper trough approaches from the
Plains. This feature passes to our south. Surface and 850
circulations also pass to our south. The models show widespread QPF
on the northern periphery. So will have high POPS. Precipitation
likely to become more scattered on Sunday as system further
occludes. No big dropoff in 850 temps with no big push of colder air
as weakening system maintains mild 850 temps with southeast flow
around weak low. 925 millibar progs suggest some potential cooling
into the north and northwest cwa but by and large system not tapping
into much in the way of cold air.
MONDAY - Confidence...Medium
A shortwave drops in from the northern stream though precip is
focused more to our north with this feature. Meanwhile another
shortwave shifts from the Plains into the mid Miss Vly with precip
to our south with this. So we may be able to dry out a bit though at
the surface there is an inverted trough axis but any organized lift
looks lacking at this point. Going with Superblend guidance.
TUESDAY AND WEDNESDAY - Confidence...Medium
Surface ridging slides in with some differences between the GFS and
ECMWF on degree of cooling. The GFS shows a much cooler thermal
pattern at 925 than the ECMWF. Looks like precip from next system
will remain to our west with the stable influence of high pressure
AVIATION(06Z TAFS)...VFR conditions expected to persist through
Thursday as a ridge of high pressure drifts east through the
Great Lakes. Winds will be gusty out of the south through the day
on into the evening before a stationary front sets up across
central Wisconsin. Conditions mainly look to be dry through
Thursday evening as well.
MARINE...A Small Craft Advisory is in effect from late this morning
into tonight for brisk ssely winds and high waves. The highest waves
will occur north of Port Washington. The winds and waves will
gradually subside through the night.
Brisk enely may then develop for Fri nt-Sat nt as a cold front moves
south through the region. A Small Craft Advisory may be needed.
LM...Small Craft Advisory until 7 PM CDT this evening for LMZ645-646.
Small Craft Advisory until 1 AM CDT Friday for LMZ643-644.
Today/Tonight and Aviation/Marine...Gehring
Friday THROUGH Wednesday...Collar