Area Forecast Discussion
Issued by NWS Indianapolis, IN

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491
FXUS63 KIND 190800
AFDIND

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

.UPDATE...
The SYNOPSIS, NEAR TERM, SHORT TERM, and LONG TERM sections have 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 300 AM EST Sun Feb 19 2017

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 190600Z TAF Issuance/...
Issued at 1201 AM EST Sun Feb 19 2017

Deteriorating flying conditions are expected overnight continuing
through mid morning in fog and low stratus before returning to
VFR conditions this afternoon.

Stratus with ceilings near or just below 1000ft have been steadily
expanding northeast all evening from southern Illinois with
pockets of visibility restrictions. Model soundings and RH progs
with most short range guidance continue to show the stratus
overspreading much of the area over the next few hours as a shallow
but sharp inversion develops. Confidence is growing in sub-IFR
ceilings impacting the terminals pre dawn hours through midday
with potential for locally dense fog.

The inversion will slowly weaken through midday with a return to
VFR conditions for this afternoon and evening along with light
winds and just scattered mid level clouds as high pressure passes
to the south. May see another round of low stratus and fog
impacting the terminals early Monday morning as the upper ridge
axis remains just west of the region.

&&

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

&&

$$

SYNOPSIS...50
NEAR TERM...50
SHORT TERM...50
LONG TERM....50
AVIATION...Ryan



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