Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
341 am CDT Thursday Oct 27 2016
Today and tonight...forecast confidence is high.
A weak surface high pressure ridge will drift across the area
today into this evening. Soundings show lots of trapped low level
moisture today, so look for the clouds to hang in pretty tough.
Any clearing tonight will be difficult as well. We do see the
gradient flow kick in as low pressure pushes in from the west, but
most of that wind will likely stay above the low level inversion,
and that inversion will be strengthened by warm air advection
Additionally, that warm air advection should generate a decent amount of mid and
high level cloudiness. In short, mostly cloudy through tonight.
Clouds today will keep highs in the upper 40s. Lows tonight will
hover around 40.
Friday through Saturday night...forecast confidence is medium.
Models are in good agreement with showing warm air advection
continuing across the area Friday. A tight pressure gradient
develops, with allows for gusty south winds to occur over the
area. These winds veer southwesterly Friday evening, then weaken
later in the night as a cold front approaches from the northwest.
Partly sunny skies and the breezy south winds should allow for a
mild Friday. Highs in the lower to middle 60s are expected,
highest in the southern and western counties.
Temperatures should remain rather mild Friday night, as the feed
of mild air from the southwest continues. Lows only in the middle
to upper 50s are forecast at this time. Clouds will increase
Friday night, as the front approaches the area. Moisture on area
forecast soundings is rather shallow in the low levels. NAM is
only model bringing light quantitative precipitation forecast into the area Friday night. Thus,
will leave the forecast dry for now Friday night.
The front slides south of the area Saturday, lingering there
Saturday night until secondary low pressure system slides east
through the region. Main 500 mb vorticity maximum with some
differential cyclonic vorticity advection will slide east Saturday
night. An area of decent low level frontogenesis response also
pushes through or close to the area. There is modestly better
moisture in the low levels up to around the 700 mb level. Kept
pops going for Saturday afternoon into Saturday night.
Did not mention thunder at this time, as GFS forecast soundings
are showing little elevated cape, versus the nam's more aggressive
elevated cape values. Mild temperatures should continue, with
clouds in the area. Highs should reach the lower to middle 60s
Saturday, with middle 40s Saturday night.
Sunday through Wednesday...forecast confidence is medium.
European model (ecmwf)/GFS show high pressure moving east through the region
Sunday, then to the east Sunday night. Thus, quiet weather should
occur, with highs remaining mild.
Low pressure is then forecast to move into the northern plains
Sunday night, then to west central Minnesota Monday, to north of
Lake Superior Monday night. Another strong pressure gradient
develops over the area for Monday, ahead of the low and cold
front. Gusty south winds should bring warm temperatures into the
area once again. Forecast middle to upper 60s for highs Monday,
but may end up warmer given good low level mixing and some
Main 500 mb shortwave trough slides east northeast from the
northern plains into the Lake Superior area Monday night. A cold
front slides east through the area as well, exiting to the east by
Tuesday morning. There is not a lot of air column moisture to
work with during this period. Kept blended pops for Monday
afternoon and evening, though could see this period end up dry.
Models then show differing solutions for Tuesday night into
Wednesday. For now, will leave blended pops and temperatures as
There may be some lingering IFR ceilings around at the start of the
tafs at 12z this morning, but in general, ceilings will be MVFR
through mid to late afternoon today. Eventually, enough dry air
works in on northerly winds to lift ceilings to VFR levels by evening.
Skies are expected to remain overcast through most of the taf
period. Weak high pressure moves over the area today, drifting off
to the east by tonight. Look for strengthening winds later
tonight, especially above the boundary layer, with rather breezy
southerly winds expected on Friday.
The Small Craft Advisory will continue through 10 am this
morning, as waves are slower to diminish in the wake of the strong
winds into last evening. Northerly winds today should be low
enough to keep the waves below Small Craft Advisory levels.
Southerly winds increase quickly on Friday, as low pressure
approaches the area from the west. That low will pass by to the
north with the pressure gradient tightening up quite a bit. A few
gale force gusts are possible Friday evening, before winds
diminish quickly by sunrise on Saturday. A Small Craft Advisory
will likely be needed for Friday and Friday night, possibly a
short duration Gale Warning Friday evening.
Another low pressure system approaching on Monday will bring
breezy southerly winds Monday and Monday night, with another
Small Craft Advisory likely.
Lm...Small Craft Advisory until 10 am CDT this morning for lmz643>646.
Today/tonight and aviation/marine...Davis
Friday through Wednesday...wood