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Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI
920 PM CDT Friday Jul 25 2014

Update...temperatures have slipped into the middle 60s in some
eastern locations...so tweeked a few locations downward overnight.
Expect clouds to hang on through the night due to weak low level
warm air advection and upstream weak short wave over southern Minnesota
heading this way. Removed low probability of precipitation from this evening earlier. Not
impossible a stray -shra may develop as short wave/trough passes
late tonight or early Saturday...but not enough confidence to add
probability of precipitation at this point.

&&

Aviation/06z tafs/...MVFR ceilings making slow progress eastward in weak
low level flow. Expect stratus to hang on into Saturday morning
before thinning as drier air behind passing weak trough settles
into southern WI.

&&

Previous discussion... /issued 233 PM CDT Friday Jul 25 2014/

Short term...

Tonight and Saturday...forecast confidence...medium

An area of light rain is currently pushing offshore...with latest
mesoscale models suggesting mainly dry weather after that. Low level
jet and best warm advection will be focused farther south
tonight...so have lowered probability of precipitation quite a bit. Lingered some low probability of precipitation
into the evening...going dry across southern Wisconsin after
midnight.

Models showing a good amount of instability tomorrow...but soundings
look pretty capped through most of the day. Trough axis will be
exiting in the morning...with not much of a trigger through the rest
of the day. Given all this...decided to keep probability of precipitation dry...though a
stray shower or storm not out of the question.

925 mb temperatures Saturday will be in the 22-24c range...so kept middle 80s
going most places...with a few spots getting into the upper 80s
given enough sun. Dewpoints will be back up into the middle 60s to
around 70...so it will be a sticky day.

Saturday night and Sunday...forecast confidence...high

The zonal flow begins to break down as a middle/upper level
shortwave begins to drop southeast toward Lake Superior Saturday
night...and into lower Michigan Sunday afternoon. The upper
divergence and 700 mb upward motion increases Saturday night and
Sunday morning until the 250 mb trough axis moves across Lake
Michigan Sunday afternoon.

Nsharp hail parameters still indicate a marginal severe potential
Saturday night as the cap weakens with elevated cape around 2500
joules/km with 700-500 mb lapse rates around 7.5 celsius/km.
However soundings are fairly dry below 12 thousand feet until sunrise
when moisture increases above a low level inversion around 900 mb.

NAM increases precipitation during the day Sunday...with the 00z
European model (ecmwf) producing around 0.50 inch amounts during the afternoon. By
afternoon the NAM decreases cape...and surface dewpoints.

Sunday night and Monday...forecast confidence...high

The middle/upper level trough continues to dig across the eastern
Great Lakes. 500 mb temperatures cool to around -15 celsius and
around 7 celsius at 850 mb. Lapse rates are rather steep below a
750 mb inversion. This inversion should keep any shower potential
very low.

Brisk north winds continue near Lake Michigan as high pressure
becomes centered over the eastern plains.

Long term...

Tuesday and Wednesday...forecast confidence...high

Good agreement in the GFS/European model (ecmwf) and dgex. The middle/upper trough continues
to dig across the eastern U.S. Tuesday and Wednesday.

High pressure becomes centered over the eastern plains and upper
Mississippi Valley although the cool air aloft could bring
diurnal showers...Tuesday and Wednesday.

Thursday and Friday...forecast confidence...high

The eastern U.S. Trough becomes more broad and retrogrades a
little toward the west.

This brings more diurnal precipitation chances and continues the
rather cool Summer temperatures.

Aviation/00z tafs/...

An area of light rain is currently pushing offshore...with latest
mesoscale models suggesting mainly dry weather after that. Lingered
some low probability of precipitation into the evening...going dry across southern Wisconsin
after midnight.

Kept the forecast dry for Saturday...though a stray shower or storm
not out of the question.

MVFR ceilings across the western half of the forecast area should
generally improve by evening...with mainly VFR conditions then
expected through Saturday.

Marine...

Could see Small Craft Advisory conditions develop later Sunday into
Monday as northerly winds increase.

&&

Mkx watches/warnings/advisories...
WI...none.
Lm...none.
&&

$$

Update...mbk

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