Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service northern Indiana
1250 PM EST Friday Jan 30 2015

issued at 1245 PM EST Friday Jan 30 2015

Lake effect clouds and flurries will continue to diminish this
afternoon as high pressure builds across the region. Afternoon
highs will be in the 20s with warmest readings under any cloud
cover. Low temperatures tonight will drop back into the teens. A
winter storm will take shape and impact the region starting
Saturday night. Winter storm watches are in effect.


Short term...(today and tonight)
issued at 455 am EST Friday Jan 30 2015

A vigorous upper level trough dropping across the southern Great
Lakes region provided some synoptic enhancement to precipitation...but
stronger forcing with this vorticity maximum is progressing east of the area
early this morning. This will result in a continued transition to
more of pure lake effect snow shower scenario for this
morning...although setup looks to be on the marginal side.
Reinforcing low level cold air advection push with secondary surface trough passage
overnight will keep shallow based instability in place for continued
lake effect snow showers this morning...with inversion heights
lowering through middle morning as stronger synoptic scale subsidence
is established in the wake of departing upper level trough. Any
accumulations should generally be less than an inch and mainly
through middle to late morning.

Otherwise for today main forecast challenge will be resolving sky
cover trends. Upper inflection zone/low level anticyclone to
overspread the region today with early morning gusty winds
diminishing. Middle level synoptic subsidence to continue this morning
and already seeing some decent erosion of low cloud deck across
portions of the area. Concern is that sharpening low level inversion
under the influence of this subsidence may allow stratocu to persist
through the day...particularly downwind of Lake Michigan. Retreating
low level thermal trough will result in southwest to northeast
gradient for maximum temperatures today ranging from middle 20s southwest to
around 20 far northeast. Backing low level winds in association with
the ridge of high pressure should take any residual lake effect
cloudiness northeastward across far northern portions of the area
tonight...with overall trend to partly cloudy/mostly clear skies and
light winds allowing for mins to drop back into the teens early
Saturday morning.


Long term...(saturday through thursday)
issued at 455 am EST Friday Jan 30 2015

The main challenges this period include the timing and track of a
shortwave trough well upstream over Alaska that will race southeast
into the western Great Lakes region. NCEP models and others have
recently been trending north with this system. The Garcia/mixing raw
ratio snowfall favors snowfall amounts between 8 and 10 inches.
However...issues including saturation time...low level dry air
entrainment and convection along and south of the warm front may cut
deeply into snowfall amounts. Current thinking is event snowfall
totals of 4 to 9 inches...with the lower amounts north over lower
Michigan and the higher amounts over northern Indiana and Northwest
Ohio. Cips top 15 analogs paint a solid 4 to 6 inches of snow
across the area. After coordination with neighboring offices...
have elected to hold off issuing a watch due to uncertain model
handing of this system amid lingering uncertainties. Will highlight
concerns in a Special Weather Statement for now. Otherwise...much
colder air will be over the area for the upcoming work week.


Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1245 PM EST Friday Jan 30 2015

Marginal MVFR ceilings will persist at ksbn through the afternoon with
eventual trend to clearing skies tonight. Radar returns and surface
reports showing little more than flurries here and there so no
visibility impacts expected.

After 00z Sat little in the way of sensible weather concerns as
high pressure dominates.


Iwx watches/warnings/advisories...
in...Winter Storm Watch from Saturday evening through Sunday evening
for inz003>009-012>018-020-022>027-032>034.

Michigan...Winter Storm Watch from Saturday evening through Sunday evening
for miz077>081.

Ohio...Winter Storm Watch from Saturday evening through Sunday evening
for ohz001-002-004-005-015-016-024-025.



short term...marsili
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