Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Indianapolis in
326 PM EST Monday Jan 26 2015
the aviation section has been updated below.
issued at 152 PM EST Monday Jan 26 2015
A quick moving weather disturbance will push across Illinois and
Indiana this evening...bringing chances for some light snow this
evening to western parts of central Indiana.
Cold high pressure is expected to arrive on Tuesday and continue
to remain in the area through Wednesday night. This will result in
dry weather with below normal temperatures. Another quick moving
area of low pressure is expected to arrive and pass across central
Indiana on early Thursday morning...once again resulting in chances
Another weak low pressure system is expected to push across the
region this weekend...once again resulting in chances for
Near term /tonight/...
Issued at 152 PM EST Monday Jan 26 2015
Surface analysis early this afternoon shows a weak ridge of high
pressure over the Mississippi River valley...extending north
across Northwest Indiana into lower Michigan. Radar shows am area of snow
showers over central Illinois...diving south-southeast. Precipitation
appeared to be very light.
Main forecast challenge today will be precipitation this evening. GFS and
and suggest the upper wave responsible for the ongoing snow over
Illinois will continue to dive south-southeast amid the quick flow aloft.
Hrrr show precipitation mainly contained to the western parts of the
forecast area. Time heights this evening show best saturation in
the western and southern parts of the forecast area...with less
moisture available across the northeast. Isentropic surface shows
little to no help as this system passes. Forecast soundings across
western Indiana continue to show good low and middle level saturation
through the night.
Thus will raise probability of precipitation...particularly across the western parts of
the forecast area...trending toward a flurry or dry forecast across
the far northeast. As for temperatures...clouds are expected through much
of the night as the upper wave passes and temperature advection is
neutral. Thus will stick close to a blend on temperatures.
Short term /Tuesday through Thursday/...
Issued at 152 PM EST Monday Jan 26 2015
Main forecast challenge during this period will be temperatures initally
followed by precipitation chances on Thursday.
Dry and cold weather is expected through Wednesday due to the
Surface high pressure building out of Canada will build across and
pass over central Indiana through Wednesday night. Time height
sections through Wednesday night continue to show a dry column
amid subsidence. Forecast soundings agree...only showing some
saturation near 12z Thursday. Meanwhile aloft...a deep trough over
eastern 1/2 of the United States will continue to provide a very
cold and northwest flow to central Indiana. This will help in resulting
in below normal temperatures. Thus with only a few quick passing
high clouds expected...will trend toward partly cloudy on Tuesday
through Wednesday evening...along with a blend on temperatures.
On late Wednesday night the GFS indicates a well organized short
wave aloft pushing into Indiana from the west. Once
again...forecast soundings hint at lower level saturation ahead of
this system. Soundings also show warm air advection in the lowest
levels that will allow any precipitation on Thursday morning to fall as
rain. 300k GFS isentropic surface shows good upglide along with a
surge of specific humidities of 2 g/kg. Thus round of light precipitation
is expected. By Thursday afternoon the upper short wave looks to
be well east of Indiana and cold air advection will once again be
in play. Forecast soundings show the saturated lower parts of the
column falling below freezing...thus a change over to snow during
the afternoon for any lingering precipitation looks reasonable. However
with a lack of deep moisture and teh best forcing off to the
east...any snow amounts will be quite light.
Long term /Thursday night through Monday/...
issued at 250 PM EST Monday Jan 26 2015
One system will be exiting our region Thursday evening...thus will
continue a slight chance of snow east and central Thursday evening.
High pressure behind this system will move across our region Friday
night and it now looks like dry weather will be the rule through
Another system will bring US a chance of snow Saturday night into
Sunday as the models have trended slower with this system.
Finally colder and dry weather will be the rule rest of the long
term as a long wave trough amplifies over the eastern U.S. The
models have trended a little colder during this period. But all and
all went close to a MOS blend on temperatures.
Aviation /discussion for the 262100z ind taf update/...
issued at 326 am EST Monday Jan 26 2015
No changes needed to the taf.
Previous discussion follows...
VFR at kind and klaf this afternoon. Otherwise...MVFR conditions
will be the rule through early Tuesday.
Area of low pressure over eastern Minnesota will track south across
Illinois tonight and on to the southeast Tuesday as high pressure
builds into the upper Midwest and western Great Lakes. This low low
pressure system will produce scattered snow showers across western
Indiana towards evening and continuing overnight and then exiting
our region after daybreak Tuesday.
MVFR ceilings currently across western Indiana will continue...while
drier air farther east may produce VFR conditions at kind and klaf.
Low pressure system will cause MVFR conditions to expand over the
entire area tonight. After this low pressure system GOES...by drier
air will spread in from the north by the end of the forecast period.
West winds 5 to 8 knots will become light late this afternoon and
tonight and northeast up to 8 knots Tuesday.
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