Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service northern Indiana
356 PM EST sun Feb 1 2015

issued at 355 PM EST sun Jan 31 2015

Low pressure will move northeast through southern Indiana today
and intensify. The low will push into central Pennsylvania by
Monday morning. As this major winter storm continues...expect
moderate to heavy snow to continue into the evening. Then
increasing winds will create blowing and drifting snow for much of
the region through tonight. Travel will become difficult to
impossible across most of the region through tonight. Snow will
diminish then end from west to east by late tonight as the system
pulls off to the east. Some lingering light lake effect snow
showers are possible across southwest lower Michigan and Northwest
Indiana on Monday. Another system may bring additional...but
lesser snow accumulations to portions of the southern Great Lakes
region Tuesday night into early Wednesday.


Short term...(this evening through monday)
issued at 351 PM EST sun Feb 1 2015

Leaving ongoing west-southwest and remaining amounts/sensible weather largely in
tact. Tremendous /upwards of 250 percent of normal precipitable water tap
poignantly depicted by ruc14 i290k surface with 50-60 knots ascending
jetlet into far southern in at this time. Mesobanding today has been quite
modulated and transitory in while a few spots in
heaviest band may exceed 15 inches...dont anticipate a large
number of outliers. Contrast to Grant/Blackford and Jay
counties...especially their southern halves...lesser amounts owing to
warm profiles/earlier mixed precipitation to likely yield at/just below
final accums.

Both presence of trowal this evening and increased static
stability per RUC/NAM profiles should also preclude moderate-extreme
convective elements. Still moderate/occasional heavy snow associated with storm
relative isentropic lift through early tonight...then quickly
becoming parallel to sfcs from west to east in 06-12 UTC Monday period.
By and large northern Illinois to eastern Iowa primary middle level deformation axis
within 700-600mb layer to congeal with another rapidly northeastward moving
maxima emanating from cntl into northestern Illinois/northwestern in to track
through southwestern lower Michigan. Primary axis through early tonight then
aligns within middle level col from klan to kbmi by 04 UTC then southern
tail deformation band quickly sweeps County Warning Area providing last potnl for
accumulate snowfall...though with thinning/descending dgz approaching
surface...the depletion of middle level moisture with passage of dry
slot...and the relaxing uvm profiles...suggests overall rates
anticipated to be increasingly muted in west-east fashion across County Warning Area in
03-08 UTC timeframe. Final short/near term issue deals with blsn
that should increase across entire County Warning Area as slr increase to near 15
to 1 in latter part of event. Ramping/backing from northeast to
east as surface low continues to deepen at approx rate of
1mb/2hrs...tracking along i70 corridor then to wcntl PA by
daybreak. Quasi-steady maintenance of 10-12mb/3hr cross
isallobaric differences to bring wind gusts to 20-30 miles per hour...and
while sub blizzard conds expected...certainly blsn to supplant
+sn as the most significant hazard/impact through the night. Most
concern with east-west open area/rural/County roads to be impacted as
surface winds progressively back.


Long term...(monday night through sunday)
issued at 351 PM EST sun Feb 1 2015

As one system is departing the next will be quickly moving in
from the northwest to bring another chance for light snow to
mainly northern portions of the forecast area (along and north of
Route 30). Few changes have been made as overall timing and track
seem to be reasonable with a swath of an inch or 2 of snow
expected north of 30 and dusting to at most an inch south. Colder
air will move back in again behind the system...but only be a
glancing blow with highs dropping from the 20s Tuesday/Wednesday into the
teens on Thursday before heading back into the 20s. Lake response
expected behind this system with more of a multi band setup.
Could be some local accumulations but shouldn't be anything

A weak trough will move from the West Coast on Friday night into Sat
and move rapidly towards the area by Sunday. A cold front will
drop south which may bring additional chances for light snow. Chance
probability of precipitation warranted at this point over the weekend. Below normal
temperatures expected through the latter half of the week into
the weekend.


Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1248 PM EST sun Feb 1 2015

Heaviest snowfall rates combined with br/fzfg to support
primarily LIFR conds at least through late afternoon/early
evening. Gradually vertical motion and thermal profiles will lend
to lessened rates with improved conditions...with transition to
blsn as primary visibility reducing element. Finally conds above
fueling/alternate criteria by daybreak as surface low begins to
accelerate eastward...with surface low into cntl PA by 12 UTC.


Iwx watches/warnings/advisories...
in...Winter Storm Warning until 4 am EST /3 am CST/ Monday for

Michigan...Winter Storm Warning until 7 am EST Monday for miz081.

Winter Storm Warning until 4 am EST Monday for miz077>080.

Ohio...Winter Storm Warning until 7 am EST Monday for ohz001-002-004-



short term...Murphy
long term...Fisher

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

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

National Weather Service Glossary of Abbreviations