Scientific Forecaster Discussion
Area forecast discussion
National Weather Service northern Indiana
810 PM EST Tuesday Jan 27 2015
issued at 754 PM EST Tuesday Jan 27 2015
Mostly clear skies will bring temperatures down into the single
digits and low teens. Cloud cover will increase throughout the day
on Wednesday as the next low pressure system approaches the area.
Highs will be in the upper 20s and low to middle 30s. Expect a wintry
mix of precipitation Wednesday night into Thursday...with minor
ice and snow accumulations possible.
Short term...(this evening through wednesday)
issued at 326 PM EST Tuesday Jan 27 2015
Deep layered qg subsidence in wake of an exiting East Coast trough
will continue to promote quiet/mainly clear conditions into
tonight/tomorrow. Associated surface high settling south over the area
in tandem with mainly clear skies/light winds will produce optimal
radiational cooling tonight. As a result continued to favor cooler
guidance for overnight lows. Return southwest flow by Wednesday
afternoon and just a gradual increase in middle-high clouds should
allow Wednesday highs to run a few degrees warmer than today.
Long term...(wednesday night through tuesday)
issued at 326 PM EST Tuesday Jan 27 2015
Initial focus will be on 2 waves that will attempt to phase somewhat
across the Great Lakes into Thursday. First wave will be scooting
out of the plains at the onset with weak clipper moving rapidly southeast
out of Canada. Plains system will have a large warm tongue that will
accompany it and move into the area Wednesday night. Moisture will
initially be limited but rapid saturation through 800 mb will take
place towards Thursday morning. Wedge of warm air will move in
between 800 and 900 mb and complicate precipitation type. Warmest air will
be in place at the onset with cooling effects of saturation as well
as approach of Canadian wave all leading towards an eventual
transition to colder profiles and change over to more sleet/snow.
Now with all that being said...the best lift and dynamics will pass
across the far northern parts of the area with main impacts across
lower Michigan where peak isentropic lift and favorable low/middle level low
track occurs. Grids reflect a rather messy setup with thermal
profiles still highly suspect causing a low confidence forecast in
terms of impacts and duration. Surface temperatures will hover near or just
below freezing most of the night before beginning to fall off during
the afternoon hours of Thursday. Any precipitation by this time should
transition to all snow with maybe a dusting in some spots.
Touch of lake effect snow showers will occur Thursday night as
strong northwest flow sets up. However...despite increasing Delta t's moisture
will be on the decrease which should limit any impacts and keep
accumulations on the very light side.
Focus shifts to northern and southern stream system and impacts over
the weekend with models still having no clue as to what may evolve.
GFS/European model (ecmwf) still suggest decent cyclogenesis taking place more east
of the forecast area as trough takes on a negative tilt. Chances for
some snowfall look to be increasing especially into portions of Ohio
closer to the suggested track. Given track record of extended models
thus far this many days out...low confidence on what will
unfold...resulting in a lowering of blend of model guidance to middle
to high chance probability of precipitation for now. System does have the potential to bring
several inches of snow to parts of the region Sunday into Monday so
will need to monitor trends and hope models can come to some
agreement with time. Much colder air will filter in behind the
system with highs in the single digits and teens above and lows at
or below zero.
Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1235 PM EST Tuesday Jan 27 2015
VFR with light winds expected through the taf cycle. May see a
scattered cumulus deck near 3 kft materialize for a brief time this afternoon
as moisture streams off of Lake Huron under a strengthening
subsidence inversion. Otherwise anticipate some middle-high level
cloudiness...especially by tomorrow as warm air advection ensues.
Visit US at www.Weather.Gov/iwx (all lower case)
Follow US on facebook...twitter...and youtube at: