Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 192313
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
613 PM EST Thu Jan 19 2017

.UPDATE...

The Aviation section has been updated below.

&&

.SYNOPSIS...
Issued at 246 PM EST Thu Jan 19 2017

Mild and unsettled weather will continue across the Ohio Valley
through early next week with multiple chances for rain and embedded
thunderstorms. After a brief break from the wet weather...another
storm system will track through the region the middle of next week
with cooler air finally arriving in its wake.

&&

.NEAR TERM /Tonight/...
Issued at 246 PM EST Thu Jan 19 2017

The peaks of sun that were enjoyed by some locations across central
Indiana this morning is already a distant memory as thick cloud
cover now covers the entire forecast area. Moisture continues to
increase as a nice plume of tropical moisture lifts into the lower
Ohio Valley. The axis of showers has been steadily approaching the
region all day so far and as of 18Z was currently grazing the lower
Wabash Valley. Temperatures were generally in the 40s this afternoon.

Yet another round of soaking rain is on the docket for central
Indiana this evening into the overnight as a warm front and
associated surface wave lift through the region later tonight. Deep
moisture will continue to be drawn north this afternoon and evening
ahead of the surface wave with the lower levels slowly saturating
over the area. Any precipitation should be relatively light and
scattered through sunset with the only exception across the lower
Wabash Valley as soundings showing lowest 10kft are currently dry.
The arrival of a stronger surge of isentropic lift this evening at
the nose of a low level jet shifting east through the lower Ohio
Valley will aid in rainfall becoming widespread over all of central
Indiana.

A thin axis of elevated instability also will track across the
southern half of the forecast area and the overall dynamics aloft
are supportive of a continued isolated thunder mention overnight.
With an increasingly negatively tilted upper wave approaching from
the west...excellent diffluence exists in the mid and upper levels
overnight which should only further enhance rainfall rates and
coverage. Precipitable water values will peak from 1.00 to 1.25
inches between 00Z and 06Z...at 300-400% of the climatological
normal for mid January and right near the max observed value for
this time of year. While some localized flooding is certainly a good
possibility considering available moisture content and potential for
convection...the progressive nature of the system overnight should
keep flooding issues from becoming more widespread. Rain will
gradually become more scattered towards daybreak Friday from south
to north as the surface wave lifts through. Much of the forecast
area will likely see around an inch through daybreak Friday with
locally higher amounts.

Temps...temperatures are not expected to move much overnight with
the warm front lifting across central Indiana. Expect temps to
remain in the 40s all night with perhaps a slow rise towards
daybreak. Overall felt available guidance was too cool and raised
above MOS by a few degrees.

&&

.SHORT TERM /Friday through Sunday/...
Issued at 246 PM EST Thu Jan 19 2017

Forecast challenges focus on precip chances and temperatures
throughout the short term as an active...unsettled and mild weather
regime continues.

A deep upper low sitting off the Pacific Northwest coast with a
strong subtropical jet undercutting the wave will maintain an active
weather pattern across much of the country through the weekend as
pieces of energy aloft continue to eject out into the central Plains
east into the Ohio and Tennessee Valleys and the Deep South. Upper
level flow over the region will largely persist in a moist southwest
regime through Saturday night.

Scattered showers will gradually lift north of the region through
the day Friday as deeper moisture moves into the Great Lakes and the
warm front aligns over northern Indiana. Model soundings show
moisture remaining trapped within a shallow near surface
layer...with both areas of fog and low ceilings persisting for most
of the day into Friday evening over much of the region. Patchy
drizzle is a possibility as well.

The first piece of energy ejecting out of the Pacific upper low is
likely to lift well to our west into the upper Mississippi Valley
Friday night and early Saturday and at least initially will not have
a direct impact across central Indiana. As Saturday wears on
though...a plume of moist and unstable Gulf air will once again be
drawn north into the Ohio Valley with scattered showers and a few
thunderstorms developing and expanding north across the region
Saturday afternoon and night. Precip water values will rise up to
0.80 to 1 inch...250-300% of climatological normal. While higher
precip amounts should be much more localized than tonight...
additional flooding concerns could extend out through the weekend.

A second and more robust piece of energy will kick out into the
southern Plains Saturday night and shift east into the mid south
Sunday. The NAM allows for more phasing with the northern stream
energy and the result is a deep low pressure system over central
Kentucky by Sunday afternoon. The NAM however has no support from
the rest of the model suite and is well outside its comfort zone
near the end of its run...and have essentially thrown out its
solution. With the consensus southern track to the system favored...
will maintain chance pops over the region Sunday. The irony with the
development of a wrapped up low pressure to our southeast via the
NAM run would typically place much of our forecast area in an ideal
spot for heavy snow. But the pattern we reside in currently is not
typical for mid January by any means. And even if this solution
would come to pass...there is just no cold air present over the
region to support snow.

Temps...if you like mild temps in the middle of winter...this
forecast is for you.  While it will be well above normal...MOS
guidance appears to be a bit overzealous with afternoon highs
through the period. Taking a model blend and leaning closer to raw
model temps...highs should rise into the 50s Friday...lower 60s
Saturday and mid/upper 50s Sunday. Lows will be in the mid and upper
40s through the period.

&&

.LONG TERM /Sunday night through Thursday/...
Issued at 146 PM EST Thu Jan 19 2017

An upper low will move across the southeast U.S. and then slowly
move up the east coast through the extended. NAM is a distinct
outlier in its treatment of the low early in the extended so
disregarded it. GFS/ECMWF in pretty good agreement and generally
used the Superblend without much deviation.

Temperatures will generally remain above normal through the period,
although not quite as far above as this weekend. This effectively
means all precipitation chances through the extended, with the
exception of the very end, are for rain. The pattern shows little
in the way of strong forcing until Tuesday night when an upper
wave and cold front move through. Otherwise small chances for rain
off and on through the end of the period with little shortwaves
moving through the flow.

Included some rain/snow mix late Wednesday night/early Thursday

&&

.AVIATION /Discussion for the 20/00Z TAFs/...
Issued at 613 PM EST Thu Jan 19 2017

Flying conditions will deteriorate this evening to MVFR and then to
IFR or worse as the night wears on.

Ample low level moisture wil remain in place as low pressure passes
through the area tonight into Friday. Ceilings and visibilities will
likely deteriorate in rain showers and fog...although fluctuations
are likely to occur.

Winds through the period will be less than 10KT...initially out of
the east much of the night, becoming southerly after warm frontal
passage late tonight into Friday morning.

Poor conditions appear likely to persist much of the period as a
strong low level inversion remains in place.

While isolated thunder cannot be ruled out, this probability is too
low for inclusion in the TAF.

&&

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

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN
SHORT TERM...RYAN
LONG TERM...CP
AVIATION...NIELD



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