Area Forecast Discussion
Issued by NWS Indianapolis, IN

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378
FXUS63 KIND 122037
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
337 PM EST Tue Dec 12 2017

.UPDATE...
The SYNOPSIS...NEAR TERM...SHORT TERM
and LONG TERM Sections have been updated below.

&&

.SYNOPSIS...
Issued at 332 PM EST Tue Dec 12 2017

Clipper systems will bring chances for precipitation Wednesday and
again Friday and reinforce below normal temperatures. After that
a warmup will arrive for the weekend, followed by more precip
chances to end the weekend and start next week.

&&

.NEAR TERM /Tonight/...

Issued at 332 PM EST Tue Dec 12 2017

Snow showers/flurries associated with a lake enhanced band on the
back side of a low pressure system should continue to weaken and
move east over the next couple of hours, making for a dry night
tonight across the forecast area. Wind gusts currently across the
area of 20 to 30 mph should drop off after sunset. Loss of heating
should allow for clouds over the northeast counties to scatter and
dissipate and this should make for good radiational cooling
conditions overnight. Expect to see lows in the teens. There is a
chance the lake effect band could remain over the northeastern
counties and keep at least some clouds there during the night.
Will monitor tonight if this happens will have to increase low
temperatures in that area, but low confidence in this outcome.

&&

.SHORT TERM /Wednesday through Friday/...

Issued at 332 PM EST Tue Dec 12 2017

Forecast focus is on precipitation chances for Wednesday/Wednesday
night with a clipper system again moving through the Great Lakes.
Models are in fairly good agreement on the upper wave not
bringing any chances for precipitation into the forecast area
until at least late morning if not the afternoon. Warm advection
will take place during the morning across most of the area ahead
of the clipper, and this should allow the column to warm with
temperatures reaching into the 40s for the southwestern half or so
of the area, and mid to upper 30s over the remainder. Thus as
forcing from the clipper arrives, some of the area will likely
seeing rain or a mix of rain and snow. Also, the column looks
fairly dry to start the day, and it could take some time to reach
saturation for precip to make it to the surface. Expect to see
some cooling with precip onset for this reason as well. Thus even
spots that see rain initially could change over to a mix rather
quickly, especially in the northern half or so of the area. With
warmer temperatures to start though and some warming of the ground
amounts will be light. The highest snowfall totals will be in the
northeast where precip will likely remain snow the entire time.
Looking at around an inch to perhaps an inch an a half in isolated
parts of the northeastern counties. Northeast of Indy could see a
couple tenths to half an inch, with accumulation unlikely west
and south of I-74. Snow will continue over the far northeast
counties til midnight or so and this could have some lake
enhancement.

By Thursday morning dry weather will again be the rule until
Friday, when another system could bring some small chances for
snow back to the area. At this time accumulations look very
minimal. Temperatures will run below normal through the short
term.

&&

.LONG TERM /Friday night through Tuesday/...

Issued at 332 PM EST Tue Dec 12 2017

Friday night will begin the weekend a little cold with snow on its
way away from the area and only a slight chance for snow over the
eastern counties early. After that models are in agreement on the
upper pattern turning warmer and dry for most of the weekend with
upper ridging building over the area. Highs in the 40s and lows in
the upper 20s to low 30s can be expected. Starting Sunday
afternoon another upper trough begins to approach the area and
this will bring increasing chances for precipitation for parts of
the area. Models are showing more of a spread with the timing of
this next troughs approach and passage though, so low confidence
on timing of precipitation, and lower than normal confidence for
Monday through Tuesday temperatures. Prior to that, high
confidence in temperatures for the weekend and dry conditions
going into Sunday.

&&

.AVIATION /Discussion for 12/21Z TAF Issuance/...

Issued at 330 PM EST Tue Dec 12 2017

Updated current conditions only. Previous discussion follows...

VFR Conditions expected through TAF period.

Scattered snow showers should stay northeast of any of the TAF
sites this afternoon. Primary hazard to aviation today will be
gusty winds approaching 25 kts at times this afternoon. Winds will
weaken after sunset and will shift to the south by sunrise
tomorrow. Clouds at or around 3000 ft will dissipate by mid
afternoon today leaving scattered clouds above 15000 ft.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...CP
NEAR TERM...CP
SHORT TERM...CP
LONG TERM....CP
AVIATION...White/JN/CP



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