Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service northern Indiana
849 PM EST Monday Feb 8 2016

issued at 349 PM EST Monday Feb 8 2016

Accumulating snowfall is expected across much of the Great Lakes
beginning late tonight and lasting into early Thursday. Amounts
during any one period will be generally light but the long
duration of the event may allow areas near Lake Michigan to see
between 6 and 12 inches of snow by the time Thursday morning rolls
around. Arctic air will impact the region later this week
dropping highs into the teens to low 20s and lows in the single
digits above zero. Lows tonight will range from the upper teens in
southwestern Indiana to the middle 20s in northwestern Ohio.


issued at 838 PM EST Monday Feb 8 2016

Several vorticity lobes rotating through Ohio Valley upper trough will
result in only very slow eastward translation of upper level low.
An elongated vorticity maximum across the western Great Lakes will move
very little but become increasingly sheared in nature as it
appears to try and phase with vorticity maximum dropping across southern
Indiana this evening. Low level cold advection is being slowed
somewhat by low level thetae ridging extending back northwestward
across Southern Lower Michigan. Nevertheless...snow showers have
expanded in coverage over the past few hours...largely in response
to this aforementioned synoptic forcing and some convective
contribution/steep low level lapse rates/lake enhancement. Weak
low level trough to drop southward across far Southern Lake
Michigan overnight should allow snow showers to continue although
better organization will be limited by modest shear in cloud
bearing layer. Snow ratios also do not appear to be optimal
overnight given potential of some riming to lessen ratios. 1 to 3
inch accumulations appear to be possible downwind of Lake Michigan
tonight and not many changes made to going grids. Special Weather Statement issued
earlier to highlight slick roads that have been reported across
portions of the area due to some re-freezing of earlier melted
precipitation and New Light snow accumulations.


Short term...(this evening through tuesday)
issued at 349 PM EST Monday Feb 8 2016

500 mb low center over Central Lake Michigan this afternoon will round southeastward
into Western Lake er by Tuesday afternoon. However eastern extent of incoming ll cold air advection Wing
is delayed until lt period coincident west/eventual upstream back of ll
follow. Thus overall lake response tonight expected to be tepid until after 06z
when most vigorous moisture flux/vertical ascent develops across northwest County Warning Area.
Regardless inherent snow band development lt tonight looks to remain
transitory which shld limit potential accumulations in any one
locale outside perhaps NE LaPorte/western St Joe. At any rate will forego
short durations headline need lt tonight/Erly Tuesday am to evening shift.

Otrws upstream middle level moisture plume holds west on Tuesday while ll thermal
trough steadily grows. This is likely to keep light shsn going
through the day far northwest however inland reach much in doubt given degree
of middle level subsidence within middle level dryslot and will temper prior
gridded probability of precipitation considerably east half. As such will again continue to hold
off on any potential highlights this period as more compelling period
lies beyond Tuesday night and Wednesday.


Long term...(tuesday night through monday)
issued at 349 PM EST Monday Feb 8 2016

For Tuesday night through next Monday...Lake effect snow will
be ongoing Tuesday night and should be increasing as an upper
level trough moves into the area. Many favorable factors will come
together for accumulating lake effect snow Tuesday night including
a long fetch over open waters including preconditioning from Lake
Superior which was only 4 percent ice covered. This long fetch
combined with synoptic lift/upper support and very large Delta T
values from 20c to 25c in the dendritic growth zone favor heavy
lake effect snow from northern LaPorte County and northern St
Joseph into lower Michigan including Berrien and Cass counties. A
winter headline will likely be needed at some point for this snow.
The lake effect snow will persist into Thursday with additional
accumulations. Inversion heights fall briefly with backing winds
Thursday night ahead of a second strong cold front... allowing
only a short break in the Snow.

Lake effect snow will likely develop and increase again Friday
night...with significant accumulations possible as a second system
moves into the area. Have trended temperatures colder Friday through
Sunday. It looks like lows Saturday night will be around zero or
just above zero.


Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 701 PM EST Monday Feb 8 2016

Several short waves continue to rotate through negative upper
height anomaly across the Ohio Valley this evening. Elongated vorticity
maximum extending north of this upper low across the northern Great
Lakes will provide continued focus for synoptic forcing through
the early portions of the overnight. While greater lake induced
instability will have a tough time building into the region
tonight given low level thermal ridging wrapping back
northwestward across lower Michigan...Lake enhancement and steep
low level lapse rates/some convective contribution will allow for
numerous snow showers to continue overnight with periodic IFR
visibilities at ksbn. After early-middle morning Tuesday...confidence in
impacts from snow showers diminishes some with weaker forcing and
still marginal lake effect parameters. Greater impacts are
expected toward the end of this period as low level front/trough
drop across the southern Great Lakes bringing greater potential of
more significant snow showers Tuesday night.


Iwx watches/warnings/advisories...
Lm...Small Craft Advisory from 1 am Tuesday to 10 am EST Thursday for



short term...T
long term...skipper

Visit US at www.Weather.Gov/iwx (all lower case)

Follow US on facebook...twitter...and youtube at:

National Weather Service Glossary of Abbreviations