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


Update... 
the aviation section has been updated below 


&& 


Synopsis... 
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 09/0300z kind taf update/... 
issued at 927 PM EST Monday Feb 8 2016 


Minor tweaks made to kind taf to better match current conditions. 
No other changes are needed at this time. 


Previous aviation discussion follows... 
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 
tonight. 


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. 


&& 


$$ 


Synopsis...Ryan 
near term...Ryan 
short term...Ryan 
long term....cp 
aviation...jh 






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