Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 191633
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1133 AM EST Sun Feb 19 2017

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

&&

.SYNOPSIS...
Issued at 300 AM EST Sun Feb 19 2017

Warm weather will continue through much of the week, but a return to
normal will occur next weekend. A cold front will bring rain chances
Monday night into Tuesday, with another frontal system bringing more
chances for rain Thursday into Friday.

&&

.NEAR TERM.../Today/
Issued at 958 AM EST Sun Feb 19 2017

Widespread low clouds currently across the area. This morning`s upper
air indicates this moisture layer is very shallow, so expecting these
low clouds to start mixing out towards midday and on into the early
afternoon hours.

Will lower the highs today about 3-5 degrees as a starting point due
to the delayed clearing, but if low cloud hangs on longer than
expected, adjusted highs will still probably be too warm. Will
monitor clearing trends over the next few hours.

Previous discussion follows.

An area of stratus continues to overspread central Indiana early
this morning. This trend should continue, with all areas becoming
cloudy. So far, dense fog has remained across Illinois and Kentucky,
with generally only patchy light fog across central Indiana.

Will have to watch the development of fog closely, with some hi-res
guidance showing dense fog developing. For now plan to continue
mention of areas of fog, but will update as needed if dense fog
forms.

Stratus should hang around this morning as forecast soundings show a
shallow but decent inversion. The lower clouds should mix out early
this afternoon, allowing skies to become partly cloudy. However,
precise timing of this mix out remains uncertain as inversion hangs
out for a good part of the day.

With the uncertainty on when the stratus will break up, high
temperatures are also uncertain. If the sun comes out late
morning/early in the afternoon, temperatures could rebound into mid
to upper 60s. However, if clouds hang around, some areas may not see
60. (Latest RAP model surface temperature shows this potential, with
some areas only in the mid 50s at 20Z while others are in the mid
60s).

With this in mind will stick with the model blend of highs in the
low to mid 60s.

&&

.SHORT TERM.../Tonight through Tuesday night/
Issued at 300 AM EST Sun Feb 19 2017

Models are close enough that the SuperBlend initialization
was accepted for most items.

Some fog will develop again tonight with high pressure in control
and an upper ridge aloft. Went a little cooler than the blend some
areas for low temperatures with the potential fog development.

Fog will burn off Monday morning, but again questions remain on how
fast. This would have an impact on temperatures. If fog burns off
quickly, readings should exceed guidance and get to around 70 or the
lower 70s. A slower burnoff would lead to cooler temperatures. Thus,
rather than raise the initialization`s temperatures, will stick with
it for now. Would rather err on the cooler side.

A cold front will bring the chance for showers Monday night into
Tuesday evening. Models are diverging on timing of this system, with
the GFS the fastest and the NAM the slowest. With no clear favorite
yet, stuck with the initialization`s mainly chance category PoPs.

&&

.LONG TERM.../Wednesday Through Saturday/
Issued at 300 AM EST Sun Feb 19 2017

Models are close enough that the SuperBlend initialization
was accepted for most items.

After a dry and warm Wednesday, a frontal system will bring more
rain chances Wednesday night through Friday night.

On Friday afternoon, a potent cold front will move through with a
sub 1000mb low off to our northwest. 850mb winds could be around
50kt. This setup could allow for some thunderstorms with the front.

Seasonable air will then move in behind the cold front for next
weekend. Although it will be seasonable, it will feel colder thanks
to all of the warm weather preceding it.

&&

.AVIATION /Discussion for the 191800Z TAFS/...
Issued at 1133 AM EST Sun Feb 19 2017

Visible satellite loop indicates thin spots developing within the
low cloud deck, so expecting lingering IFR/patchy LIFR conditions
to lift and scatter out over the next couple of hours.

May see redevelopment of IFR ceilings/visibilities after 200300Z
tonight given limited mixing and residual moisture trapped under a
shallow low level inversion.

Surface winds generally at or below 6 kts through this evening.

&&

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

$$

SYNOPSIS...50
NEAR TERM...50/JAS
SHORT TERM...50
LONG TERM....50
AVIATION...JAS



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