Scientific Forecaster Discussion
fxus63 kind 120400
Area forecast discussion
National Weather Service Indianapolis in
1100 PM EST Mon Dec 11 2017
the aviation section has been updated below.
issued at 238 PM EST Mon Dec 11 2017
There will be a few disturbances to focus on throughout the
forecast period. The first will be tonight when a cold front
passes through central Indiana. Snow showers will accompany this
front along with much colder air. In addition, some freezing
drizzle cannot be ruled out across the southern counties early
tomorrow morning. The winter precipitation will quickly taper off
by tomorrow afternoon though except for some lingering lake
enhanced flurries over the northeast quadrant, and dry conditions
will then prevail into Wednesday. At that point, another upper
wave will bring snow showers Wednesday night with light
accumulations across the northern counties. Further out,
additional light snow showers will be possible over the northern
counties once again on Friday with yet another upper wave.
Near term /tonight/...
issued at 719 PM EST Mon Dec 11 2017
Raised wind speeds to 10 to 20 knots tonight and tomorrow in line
with trends and tight surface pressure gradient.
Previous discussion follows...
issued at 238 PM EST Mon Dec 11 2017
The main focus of the near term period will be winter
precipitation chances tonight with a cold front.
Central Indiana is currently in a bit of a weak warm sector with a
surface trough to the west. As mid levels become more saturated,
and forcing strengthens with the associated cold front between Tue
03-06z, precipitation will start reaching the ground. Initially
there could be a little rain mixed in with the snow across the
southern and central counties, eventually transitioning to a
freezing drizzle/snow mix late in the night. However, the northern
counties will primarily see all snow with some light
accumulations up to a half inch over the northeasternmost
counties where additional forcing will be provided from the upper
Meanwhile, temperatures will hover around the mid to upper 30s
into the night with a faster drop off late in the night as
northwest winds gust to 30 mph. Overnight lows will plummet into
the low 20s (n) to upper 20s (s) by daybreak.
Short term /tomorrow through Thursday/...
Issued at 404 PM EST Mon Dec 11 2017
Much colder air will settle across central Indiana tomorrow in the
wake of the cold front. Brisk northwest winds will gust to 30 mph,
and daytime highs will only top off in the 20s. However, the snow
showers will quickly taper off by tomorrow afternoon with the
best chances confined to the northeast counties where lake
enhanced snow showers will linger longer.
As skies clear out, the temperatures will plummet into the teens
tomorrow night and strong northwest winds will continue to
gust to 30 mph. Nonetheless, temperatures will recover a bit by
Wednesday with highs climbing back into the 30s and even low 40s
The dry pattern will quickly come to an end by Wednesday night as
another upper low rotates through Indiana. Once again, light snow
accumulations can be expected across the northern counties.
Long term /Thursday night through Monday/...
issued at 148 PM EST Mon Dec 11 2017
Models are close enough with the big picture that the model blend
initialization was accepted for most items.
A couple of upper troughs will move through the area during the long
term. Impulses within these troughs will have the potential to bring
some precipitation to the area, but again the models differ on the
details of timing and extent of precipitation. Also, as usual that
far out, there isn't a clear preference on which model is better.
Therefore, will keep the initialization intact with low confidence,
which leads to low precipitation chances around Friday and again
Even with the upper troughs moving through, the colder air remains
bottled up to the north of the area for much of the period. After a
cool day Friday, the weekend into early next week looks to have
above normal temperatures.
Aviation /discussion for the 12/06z taf issuance/...
issued at 1100 PM EST Mon Dec 11 2017
A cold front will be near an Indianapolis to Terre Haute line at
06z. Good confidence conditions behind the front will be MVFR for
several per the sref and GFS lamp. Could see snow showers or
especially at ind and bmg and possibly even freezing drizzle at bmg.
By 09z-12z, conditions should improve to VFR once again. However,
confidence in exact timing is low.
The gusty northwest winds will continue. Wind speeds will be up to
20 knots with gusts to near 30 knots at times. The winds will then
diminish after 23z or 24z.