Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 140810
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
310 AM EST Tue Nov 14 2017

.UPDATE...
The LONG TERM Section has been updated below.

&&

.SYNOPSIS...
Issued at 313 PM EST Mon Nov 13 2017

Dry weather will stay in place over central Indiana until early
Wednesday morning when a low pressure system approaches from the
west, bringing rain to the area through the day on Wednesday.
After a dry Thursday, a stronger system will arrive on Friday
bringing rain and chances for thunderstorms, some of which could
be strong, to the area through Friday night, with rain moving out
slowly on Saturday.

&&

.NEAR TERM /Rest of Tonight/...

Issued at 930 PM EST Mon Nov 13 2017

Update...
Clouds will linger into the night across the eastern half of the
forecast area, but the western counties will experience clearing.
Overnight lows are still progged to bottom out in the low 30s, so
no changes needed. Updated grids have been sent.

Previous Discussion...
High confidence in dry conditions overnight. Forecast focus then
is on whether or not cloud cover will scatter and clear out or
hang around through the night. Low confidence forecast due to
uncertainty with models not in good agreement, and also their
tendency to move stratus out too quickly. High pressure is
building in from the west, but low level moisture is still in
place and is evident in time heights through the night. Think
western counties could see clearing that may not fill back in
since they`ve seen more sun through the day and are closer to the
high center, but elsewhere think anything that scatters over the
next couple of hours will fill back in later. Thus will go with
cloudy to mostly cloudy skies over much of the area through the
night, except perhaps the far western counties. Lows should run
around 32 to 34 given the cloud cover.

&&

.SHORT TERM /Tuesday through Thursday/...

Issued at 313 PM EST Mon Nov 13 2017

High pressure crossing the area Tuesday should finally allow
clouds to scatter and skies to clear. Even so temperatures will
only warm to the upper 40s to lower 50s. Tuesday night warm
advection will start to ramp up and bring in chances for rain into
the western counties late. A cold front will move through the area
during the day on Wednesday and rain will be in place ahead of the
front, as well as some scattered showers in the wake of the
frontal passage. Considered addition of thunder for Wednesday, but
only NAM shows any instability (even elevated) over the area, and
highs barely make it into the 50s, so decided to leave out any
thunder mention at this time.

By Wednesday night, dry conditions will be filling in behind the
front, and temperatures should drop into the low 30s. Thursday
should see some sunshine but with cold advection highs will remain
in the upper 40s.

&&

.LONG TERM /Friday through Tuesday/...

Issued at 257 AM EST Tue Nov 14 2017

The pattern remains progressive and cool. Some potential for
severe weather late Friday into early Saturday.

Models agree on a strengthening weather system affecting the
Great Lakes and Ohio Valley Friday and Saturday. Still large
differences on timing and degree of system intensification thus
confidence remains a bit low regarding start and end of
precipitation, and severe potential. Currently leaning toward a
solution midway between fastest, GFS, and slowest, ECM.

Scattered showers should initially overspread our NW counties by
midday Friday as warmer and more humid air advects into the region.
A few peeks at the sun early, with the warm and moist advection,
should result in enough destabilization to warrant a low threat
for thunder Friday.

Friday night, more widespread showers and isolated storms will
affect all of central Indiana Friday night within the warm sector.
With further destabilization, thunder a slightly greater threat
Friday night than daytime Friday. Downdrafts within showers or
storms could reach severe potential given 50kt winds as low as
3000 ft.

Cold frontal passage Saturday should bring an end to the
precipitation in the afternoon from west to east as winds swing
to west northwest and gust to near 30 mph.

Saturday night, building high pressure will spread clearing skies
across most of the area. For our northeast counties, wrap-around
showers will likely continue the evening as the upper low
strengthens over the Great Lakes and wind fetch off Lake Michigan
occurs. As temperatures fall, a change to light snow showers
should occur before ending with no snow accumulation expected.

Sunday into early Tuesday will be a cold but tranquil period as
high pressure traverses the area.

The next weather system moving ashore in the Pacific Northwest
Friday will approach our region by Tuesday returning a chance
for precipitation. Right now it looks like we will warm enough
that precipitation will be rain.

Temperatures in the extended are a blend from model solutions
and will start near normal Friday and Saturday then transition
to well below normal again by Sunday with slow moderation into Tuesday.

&&

.AVIATION /Discussion for the 04/06Z TAF Issuance/...

Issued at 1155 PM EST Mon Nov 13 2017

The main challenge for the TAF period will be the threat for fog
formation. Clearing has already commenced at the western TAF
sites, and MVFR fog is currently impacting KLAF and KIND but not
KHUF. Elsewhere, clouds have been slow to move out of KBMG, and
MVFR ceilings are still lingering. For now, will hold off on fog
mention at KHUF and KBMG, but these may need to be updated.
Elsewhere, will stick with MVFR fog at KHUF and KIND for now, too,
but that is a low confidence forecast. Would not be surprised if
there was a sudden drop to IFR or worse late in the night. After
the threat for any fog subsides, VFR will be the prevailing flight
category through the end of the TAF period. Meanwhile, winds will
be light and variable and conducive to fog formation.


&&

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

$$

SYNOPSIS...CP
NEAR TERM...CP/TDUD
SHORT TERM...CP
LONG TERM....Tucek
AVIATION...TDUD



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