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Area forecast discussion 
National Weather Service Indianapolis in
605 PM EST Monday Feb 8 2016

the aviation section has been updated below


issued at 305 PM EST Monday Feb 8 2016

An upper low will spin slowly over the lower Great Lakes through
midweek...producing snow showers along with windy and progressively
colder weather through Wednesday. High pressure will return for late
week with dry and cold conditions. A quick moving clipper system may
bring snow Friday...followed by a potential larger storm system
for late weekend into early next week.


Near term /tonight/...
issued at 305 PM EST Monday Feb 8 2016

Secondary cold front bisecting the forecast area as of middle
afternoon. Scattered squalls continue directly ahead of the front
and predominantly south of I-70...but near surface temperatures in the middle
to even upper 30s are mitigating impacts. Have had a few reports of
quick snow bursts to the tune of a half inch to inch but as soon
snow rates diminish...surface melting commences immediately with
pavement temperatures in the middle 30s. In addition...sleet and graupel
have occasionally mixed in with these heavier squalls.

Behind the front...temperatures have quickly fallen back into the upper 20s
with snow showers continuing. Intensity of the snow showers however
is weaker and travel impacts continue to remain minimal even with
subfreezing temperatures developing. Additional area of snow showers
and occasional squalls currently over central Illinois in
association within another spoke of energy aloft will settle into
the region within the next few hours. With surface temperatures below
freezing...loss of any radiational effects from daylight and wind
gusts peaking at 25 to 30 miles per hour...expect these snow showers will have
more of an impact into the early evening. Any snow accums should
remain less than an inch in most places through the evening.

In the wake of this area of snow showers...anticipate a decrease in
coverage into the early overnight with snow showers once again
increasing in coverage and intensity in the predawn hours as the
850mb trowal swings across the area and low level flow begins to
catch more of a Lake Michigan fetch. Will bring higher probability of precipitation back
into the northern counties late as a result. Will continue with the
Special Weather Statement to highlight occasional travel impacts tonight and early Tuesday.

Temperatures...took a model blend for lows overnight as temperatures are expected
to bottom out generally in the lower 20s.


Short term /Tuesday through Thursday/...
issued at 305 PM EST Monday Feb 8 2016

High impact/low accumulation snow showers and squalls will continue
through the first half of the short term...gradually focusing more
over the northeast half of the forecast area on Wednesday before
high pressure finally builds in for Wednesday night and Thursday.

Tuesday is likely to be the day that carries the most potential
impact to travelers...and especially during the afternoon and
evening as thermodynamic profiles once again become more favorable
for heavier snow showers and squalls with steeper lapse rates and
another surge of forcing aloft as the upper low moves across the
area. The presence of a deeper snow growth zone within the colder
airmass...the potential for higher ratios and the continued
favorable lake fetch supports the best potential for light
accumulations. Continued gusty northwest winds will cause blowing
snow and drastically reduced visibilities in heavier snow showers.
With surface temperatures remaining in the 20s...icy roads will be an issue
too. The Special Weather Statement covers this well...with future shifts tonight and early
Tuesday determining if an impact-based advisory would be more
beneficial as conditions evolve.

Snow showers will continue Tuesday night...gradually focusing over
the eastern half of the forecast area into Wednesday. Remain a bit
skeptical at how quickly model guidance is trying to shut down snow
showers Wednesday with back side energy behind the departing upper
wave working in tandem with a much colder airmass. Even though
forcing aloft is weaker...still expect moisture to be squeezed out
with how cold the airmass will be. Continued chance probability of precipitation mainly east
of I-65 with potential for an additional few tenths of an inch of
snow before it ends by late day. Dry and cold conditions are then
expected for Wednesday night and Thursday as high pressure builds in
with northwest flow aloft.

For total snowfall this afternoon through Wednesday...a general 1 to
3 remains a solid call...with higher amounts focused over the
northeast half of the forecast area. Do anticipate there will be
locally higher amounts where heavier squalls occur...again most
likely focused over the northeast half of the forecast area.

Temperatures...went at or just below guidance through much of the period.
Highs will stay in the 20s Tuesday...and likely remain in the teens
Wednesday. Subzero wind chills are expected Tuesday night through
early Thursday as well.


Long term /Thursday night through Monday/...
issued at 207 PM EST Monday Feb 8 2016

A decent amount of variability showing up in ensembles and
operational solutions for the long term. Accepted initialization
with few changes as the blended consensus should provide the most
middle of the Road solution. Current 12z European model (ecmwf) is hitting clipper
system on Friday pretty hard while GFS keeps best forcing north of
the area and essentially leaves central Indiana dry. Both
models show some lake effect potential for Friday night and
Saturday but this would only impact the northeast counties if it
even reaches that far. Finally the last storm system to address
is Sunday night into Monday and possibly beyond as an upper wave
moves through. Variability regarding strength and timing is still
high and thus a slight chance for snow Sunday night with low
chances on Monday look good at this time.

Northwesterly flow will keep below normal temperatures in
place through at least Sunday.


Aviation /discussion for the 09/0000z taf issuance/...
issued at 605 PM EST Monday Feb 8 2016

Widespread MVFR with pockets of IFR with heavier snow bands
will be the rule. Could be a little improvement by late evening
and will indicate this in tafs with some deterioration very late

We will remain under a cyclonic flow as low pressure over the
Great Lakes moves slowly eastward. Winds will be west to
northwest 10 to 13 knots with gusts up to 22 knots through the period.


Ind watches/warnings/advisories...none.



near term...Ryan
short term...Ryan
long term....cp

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