Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 220520
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1216 AM EST Sun Jan 22 2017

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

&&

.SYNOPSIS...
Issued at 242 PM EST Sat Jan 21 2017

Mild and unsettled weather will continue across the Ohio Valley
through the early part of the week with potential for rain and a few
thunderstorms. After a brief break from the wet weather...another
storm system will track through the region the middle of next week
with progressively colder weather more typical of late January
arriving for late week into next weekend.

&&

.NEAR TERM /Overnight/...
Issued at 1216 AM EST Sun Jan 22 2017

Added slight chance pops overnight to much of the forecast area as a
few echoes recently developed south of the main area, across Hancock
and Henry counties.

Previous discussion follows...
Issued at 1005 PM EST Sat Jan 21 2017

Radar indicated a few tiny echoes just west of Crawfordsville. Not
sure if any of this is reaching the ground.  Otherwise...do not
expect much of anything overnight until low pressure system over the
southern plains gets closer.  Will keep 20% rain chances across our
west and south late tonight and will go dry elsewhere.  Also dropped
mention of Thunder overnight as airmass will become a little more
stable overnight and area of low pressure is too far away to have
much affect.

Another concern is possible dense fog across our far north from
Kokomo to Lafayette late tonight.  Visibilities have dropped
over portions of northern Indiana and dewpoints in our north were
close to zero. Satellite indicated a fair amount of high clouds
which may lessen fog threat.  Will continue mention of areas of
fog north...but with no fog headlines at this time.

Only other change was to lower overnight low temperatures a degree
or two across our north.  Otherwise...rest of the near term is on
track.
New NAM is trending a little farther south with the southern plains
low and is a little slower into spreading rain showers our way.

&&

.SHORT TERM /Sunday through Tuesday/...
Issued at 242 PM EST Sat Jan 21 2017

Forecast challenges focus on precip chances Sunday and Monday.

Aforementioned upper low and the strong surface wave accompanying it
will continue an E/NE trek across the Tennessee Valley on Sunday
with a secondary low developing over the southeast states and
becoming the primary wave by early Monday over the Carolinas. The
NAM as it has done the last several runs since Thursday continues to
pull the initial surface wave further to the northwest than most
other model guidance and linger it over the lower Ohio Valley
longer...all the way into Monday morning. While it remains somewhat
apart along with its 3/4km solutions...hard to discount as it
remains consistent with its earlier runs.

Expect heavier rainfall potential spreading north into the southern
half of the forecast area on Sunday as an axis of deformation in the
mid levels rotates north and interacts with deeper low level
convergence and precip water values approaching 1 inch. Elevated
instability will lift into areas south of I-70 with any thunder
mention likely being confined to southern counties on Sunday. Will
be carrying higher pops for Sunday and Sunday night as the system
moves by to the south of the region slowly. Still feel NAM models
may be a bit overzealous with precip totals through early Monday but
the idea...but potential for an additional 0.50 to 1 inch over the
southern half of central Indiana by Monday seems quite reasonable
with locally higher amounts under any convection. This could
exacerbate existing flooding on area streams and rivers and bring a
renewed period of lowland and field flooding as the ground is
saturated. Will highlight in the HWO.

Scattered showers will gradually diminish in coverage from west to
east Monday afternoon and night as central Indiana remains within a
cyclonic flow on the back side of the departing storm system.
Conditions will finally improve for Tuesday as ridging aloft quickly
replaces the upper level cyclonic flow within the continued
amplified upper pattern across the country.

Temps...Mild conditions are expected again Sunday but presence of
clouds and rain along with easterly flow will keep it cooler than
today in the 50s to around 60. Cooler weather for Monday as low
level flow shifts to northerly with highs in the mid and upper 40s.
Remains in the 40s on Tuesday. Overall ended up near MAVMOS for
highs through much of the period.

&&

.LONG TERM /Tuesday night through Saturday/...
Issued at 207 PM EST Sat Jan 21 2017

An upper trough will move into the area from the west during the
long term. This will keep small chances for precipitation in the
forecast off and on as upper waves eject out of the trough and
provide lift, mainly across northern parts of the forecast area.
Tuesday night an initial cold front will move through, followed by
a secondary cold front Wednesday night, and this second front will
usher in a return to normal temperatures for this time of year.
Small chances for snow or a mix of rain and snow will move in with
the passage of the cold front and remain through the rest of the
extended. Fairly good model agreement on the main upper pattern, so
confidence on temperature trends is high, while confidence on timing
of precip chances is low.

&&

.AVIATION /Discussion for 220600Z TAF Issuance/...
Issued at 1155 PM EST Sat Jan 21 2017

Flying conditions will lower to MVFR overnight and Sunday morning
with some improvement Sunday afternoon over north and central
sections and then IFR Sunday night.

Area of showers and a few storms over the northern portions of
central Indiana will move on to the northeast.  hen expect
only isolated light showers rest of tonight and Sunday morning.

Areas of fog will develop overnight especially north with IFR
visibilities at KLAF and mostly MVFR conditions elsewhere.

Low pressure over the southern plains will move to the
middle Mississippi valley by morning and across Kentucky Sunday
evening.
Showers will spread into central Indiana with isolated storms
south.  Showers will end Sunday evening...but low stratus and fog
will be the rule.

Winds will be light overnight becoming northeast 5 to 8 knots
Sunday and up to 10 knots late Sunday.  Winds Sunday evening will
be north to northwest 10 to 15 knots.

&&

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

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN/JH/MK
SHORT TERM...RYAN
LONG TERM....CP
AVIATION...JH


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