Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 162016
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
416 PM EDT Sat Sep 16 2017

.UPDATE...The AVIATION section has been updated below.

&&

.SYNOPSIS...
Issued at 256 PM EDT Sat Sep 16 2017

High pressure will keep it dry through Sunday morning. Then, a weak
cold front will approach from the northwest and stall out over
northwestern Indiana before dissipating early next week. In
addition, several upper waves will lift northeast over the area.
These features will interact with a warm, moist and unstable
atmosphere and result in thunderstorm chances Sunday afternoon
through Wednesday. The rest of next week will be mostly dry, under
the influence of high pressure.

Temperatures will be above normal with highs in the 80s and lows in
the 60s.

&&

.NEAR TERM /Tonight/...
Issued at 256 PM EDT Sat Sep 16 2017

Main focus tonight will be on temperatures and fog potential. Models
in good agreement that light southerly flow will continue over
central Indiana tonight on the back side of a broad area of surface
high pressure over the Appalachians and beneath an upper ridge.
Subsidence under the ridge and loss of sunset will result in
decreasing evening cu.

GFS LAMP suggests there could be some patchy overnight fog once
again as there was earlier this morning. However, not expecting it
to warrant more than patchy fog mention from 09z-13z.

Would not completely rule out a brief late afternoon weak shower or
two per earlier radar loop, but chances too low to mention.

Blend lows in the lower and mid 60s look good with afternoon dew
points in the lower and mid 60s and good radiational cooling
potential.

&&

.SHORT TERM /Sunday through Tuesday/...
Issued at 256 PM EDT Sat Sep 16 2017

Main focus for the short term will be on timing and coverage of
convection. Models in good agreement that a weak cold front will
stall over northwestern Indiana Sunday and Sunday before
dissipating. Also, numerous weak upper waves will lift northeast
across central Indiana as the upper ridge moves south and east of
the area. Additionally, the low level warm and moist southerly low
level flow will continue on the back side of Appalachians high
pressure. The front and upper waves will interact with the warm,
moist and unstable air mass which should result in thunderstorm
chances starting Sunday afternoon, when the deeper moisture and lift
move in. Best coverage will start off across our northwestern
counties and gradually shift southeast. The best chances look to be
Monday overnight and Tuesday as the strongest wave moves in.
Otherwise, would expect higher pops during and shortly after peak
heating. Confidence in timing and coverage is only moderate at best
though due to difficulty in models handing weaker upper waves.

With southerly low level flow continuing, good confidence in above
normal temperatures with blend highs in the 80s looking good.
Southwestern counties could even see upper 80s Sunday.

&&

.LONG TERM /Tuesday night Through Saturday/...
Issued at 256 PM EDT Thu Sep 14 2017

Ensembles in good agreement in developing a highly amplified pattern
during this period, with upper ridging over the Midwest and deep
troughing over the western states.

Ensembles suggest a fairly strong disturbance will eject out of the
western long wave trough into the northern Plains towards the middle
of next week. Will keep some chance PoPs in the forecast for Tuesday
night though Thursday as this disturbance brushes by the area. In
the wake of this wave, heights look to rise a little more as upper
ridge becomes better established. As a result, precipitation threat
should diminish by Friday. Will go dry on Friday and next Saturday.

&&

.AVIATION /Discussion for the 162100Z TAF Update/...
Issued at 416 PM EDT Sat Sep 16 2017

Minor adjustments at KIND based on current observations.
Otherwise...no changes needed.

18Z discussion follows.

Some diurnal clouds based around 030 this afternoon expected to
dissipate with sunset. No visibility restrictions are expected
through the evening hours, however areas of visibility restrictions
due to fog may develop after 170600Z.

Surface winds 150-180 degrees at 5-8 kts this afternoon will
become light after dark.

&&

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

&&

$$

SYNOPSIS...MK
NEAR TERM...MK
SHORT TERM...MK
LONG TERM...JAS
AVIATION...JAS/Ryan



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