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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
1122 am CST sun Feb 14 2016

..aviation update...

Synopsis...
issued at 308 am CST sun Feb 14 2016

Warm air advection Wing not as impressive as earlier expected and
has only produced 1 to 2 inches of snow in a somewhat narrow
band...from roughly Fairfield to Burlington to Macomb over the
past several hours. At 3 am the band of snow extended from Louisa
County to Knox County and was moving generally eastward. To the
north of this band of snow drier air has prevented complete
saturation of the column and only flurries or very light snow has
developed in northeast Iowa. In northwest Illinois the dry air was winning the
game so far and was causing forecaster headaches.

Current temperatures ranged from 10 to 19 across the County Warning Area.

&&

Short term...(today and tonight)
issued at 308 am CST sun Feb 14 2016

Headlines...no changes to the Winter Weather Advisory at this time.

Today...warm air advection Wing will move out of the County Warning Area early
this morning followed by strong dynamics and a more widespread
steady snow this morning into the afternoon. Water vapor movie loops
indicate the main energy approaching northwest Iowa and earlier in the
evening this was associated with lightning in western South Dakota. Forecast
soundings show saturation and lift in the dendritic growth zone
for several hours with the potential for moderate snowfall or
close to it. Later in the afternoon the main dynamics shift to
our east leaving only light snow or flurries into the evening. We
are still looking at a general 2 to 4 inch snowfall across much of
the County Warning Area. However...locations in our southern County Warning Area that also had
accumulation from the warm air advection Wing early this morning
should see total amounts around 5 inches.

The tighter gradient is occurring on the front side of this system
so southeast winds will gust to around 25 miles per hour this morning. As a
result some drifting is possible. Highs will range from the lower
20s along Highway 20 to near 30 in northeast MO.

Tonight...lingering light snow or flurries will diminish or end
from west to east before midnight with little additional accumulation
(1/2 inch or less). Lingering upper level trough and southerly
winds will keep cloudy skies across the County Warning Area...preventing much of a
temperature drop. Minimum temperatures will range from the upper
teens to middle 20s.

Long term...(monday through saturday)
issued at 308 am CST sun Feb 14 2016

The clipper Happy pattern will continue through Tuesday before a
more zonal flow pattern shifts the colder air out of the Midwest.
In the transition to this mild pattern...we will experience yet
another low confidence storm system Monday night into Tuesday.
This low may produce significant snow...but also could easily miss
our County Warning Area to the southwest within the guidance spread of models.
Unfortunately...the model depiction of a tightly wound storm is
probably correct...and like tonight the affected area of the storm
may be quite small. Thus...any change in track from model to model
will drastically change what type of day is expected Tuesday. In
short...we dont know yet where it will track as the wave ripples
southeast through the baroclinic zone over the upper Midwest into
the Ohio Valley. Our forecast...is based on a model blend...which
keeps our probability of precipitation in the chance category for this event...and I am
comfortable with that. This is lower than the previous
issuance...and reflects the potential for a non event. That
said...a narrow axis of significant snow is possible and we will
need to watch and see if that impacts our County Warning Area.

After a brief cool down to the lower 30s for highs Wednesday...the
mild air will spread rapidly over the Midwest as a strong low
pressure develops in the plains. This low is expected to pass to the
north of Iowa...resulting in a high confidence placement of the warm
sector over our entire County Warning Area. There may well be a delay on the warmest
air as we melt off snow...but based on our current forecast...any
new snow should have a core temperature in the lower 30s before this
warm up. That should set the stage for a rapid melt...and Thursday
and fridays highs in the 40s to 50s...even a few lower 60s are
possible in this regime.

The mild air should last through the weekend with temperature in the
lower to upper 40s for highs...and middle 20s to lower 30s for lows.
This will undoubtedly feel rather Spring-like in the days ahead as a
weak pressure gradient is forecast in the Midwest...nearly assuring
winds will be a non issue.

&&

Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1117 am CST sun Feb 14 2016

General MVFR to IFR flying conditions to dominate the next 24 hours.
Areas of light snow to briefly moderate snow will end between 14/18z
and 15/00z at all the terminals. Trapped low level moisture will result
in low clouds with ceilings of at or below 1k above ground level to periods of 2-3k above ground level. Visibilities
will be 1-3 miles in snow...improving to at or above 5 miles most or all of
the time in light fog after 15/00z. Southeast winds will continue through
the period mostly in the 5 to 15 knots range.

&&

Dvn watches/warnings/advisories...
Iowa...Winter Weather Advisory until 6 PM CST this evening for Benton-
Buchanan-Cedar-Clinton-Delaware-Des Moines-Dubuque-Henry Iowa-
Iowa-Jackson-Jefferson-Johnson-Jones-Keokuk-Lee-Linn-Louisa-
Muscatine-Scott-Van Buren-Washington.

Illinois...Winter Weather Advisory until 6 PM CST this evening for Bureau-
Carroll-Hancock-Henderson-Henry Illinois-Jo Daviess-McDonough-
Mercer-Putnam-Rock Island-Stephenson-Warren-Whiteside.

MO...Winter Weather Advisory until 6 PM CST this evening for Clark-
Scotland.

&&

$$

Synopsis...haase
short term...haase
long term...Ervin
aviation...Nichols

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