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Area forecast discussion 
National Weather Service northern Indiana
655 am EST Thursday Nov 27 2014

issued at 319 am EST Thursday Nov 27 2014

A fast moving system will bring a reinforcing shot of cold air to
the region this morning. Lake effect snow showers are expected to
develop quickly in the wake of this system across southwest lower
Michigan and across northern Indiana. Thanksgiving day highs will
range from the upper 20s west to the middle 30s east.


Short term...(today and tonight)
issued at 319 am EST Thursday Nov 27 2014

Difficult near term period to contend west/early on as lg scale upper wave and
attendant surface trough sweep eastward across the Great Lakes later this morning.
Already convoluted mesovort riddled lake band in progress just
offshore west/upstream burgeoning seeder feeder taking place through
eastern/southern WI. Per highres consensus of ll follow backing to approx 320
degrees and addn of synoptic moisture associated west/upper wave expect a period of
vigorous lake enhancement will develop middle to lt morning and continue into
middle afternoon before diminishing to pure lake effect shsn.

Inland extent questionable as indicated in considerably spread near
term highres guidance. However in light of sig inversion height reach along
west/decent saturation through sufficiently deep dgz have expanded
inland reach of Cat probability of precipitation in expectation of a 2-3 hour burst of
accumulating snow. Further refinement likely in later updates especially if
dominant southwestern flank convergent band seen in some solutions develop
which would take even more robust accumulating snow southward across northern in.
As it stands feel comfortable in revised gridded data utilizing a
multi-highres model blend which brings a general 2 to 3 inch
accumulation through 00z Friday to Lake Belt counties.

Continued backing to ll follow and resultant rapid weakening of ll thermal
trough will lead to a quick decay of lake effect this evening and will
mark a sig warmup to start the long term.


Long term...(friday through wednesday)
issued at 319 am EST Thursday Nov 27 2014

Transition to a flatter/quasi zonal flow regime will result in a
roller coaster temperature pattern and no real storm threats (low precipitation
chances) Friday through early next week.

Period begins cold Friday with low chances for light snow maintained
Friday afternoon/evening north of Route 30 as sheared vorticity/jet energy
ripples southeast toward the Great Lakes and induces a respectable middle level
fgen response. Bulk of guidance continues to suggest better light
snow chances along this elevated warm front north-northeast of the iwx County Warning Area...but
still enough uncertainty to hold onto probability of precipitation.

10-13c 925 mb temperature rise in warm advection regime Friday night into
Saturday may allow temperatures to make a run at 50f Saturday...and even
warmer by Sunday before a round of upper Midwest/northern lakes height
falls forces a cold front southeast through the local area later
Sunday/early Monday per latest consensus. Nwp guidance is continuing
to generate some very light quantitative precipitation forecast (patchy rain/drizzle) Saturday into
early Sunday. Not all that excited about model blend low chance probability of precipitation
during this time but can't completely rule out (especially se) given
modest low level Theta-E advection and potential for additional low
amplitude shortwave energy to translate through in flat flow. Better
chances for measurable rain will come around late Sunday/Sunday
night with the frontal passage...then turning sharply colder with
high pressure likely building in later Monday-Tuesday.


Aviation...(for the 12z tafs through 12z Friday morning)
issued at 651 am EST Thursday Nov 27 2014

General MVFR ceilings expected to continue this period in vicinity of of ksbn yet improve
inland to low end VFR at kfwa. Near term remains complicated west/approach
of upper trough and lake band offshore moving onshore over SW Michigan. Expect the
later will breakup inland through 15z. However following upstream
seeder feeder shld provide for a rapid uptick of shsn by lt morning
and continuing into middle afternoon if not later coincident west/multiple banded
lake development. Near term solution space remains favorable for a period of at least
IFR if not LIFR visibility/ceiling reduction this afternoon in vicinity of ksbn.


Iwx watches/warnings/advisories...
Lm...Small Craft Advisory until 4 am EST Friday for lmz043-046.



short term...T
long term...steinwedel

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