Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 222259
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
600 PM EST Sun Jan 22 2017

.UPDATE...
The SYNOPSIS...NEAR TERM and SHORT TERM Sections have been updated
below.

&&

.SYNOPSIS...
Issued at 314 PM EST Sun Jan 22 2017

The passage of a strong low pressure from the deep South this
afternoon up the East Coast Monday will keep cloudy skies across the
region and bring a few showers for tonight and Monday. Weak high
pressure will build in with drier weather for Tuesday. The passage
of low pressure on Wednesday will finally usher a return to more
typical late January weather for late week and into next weekend
with much colder temperatures and a few chances for light snow.

&&

.NEAR TERM /Tonight/...
Issued at 314 PM EST Sun Jan 22 2017

Mostly cloudy skies across the region this afternoon as the Ohio
Valley resides on the northwest side of the intensifying storm
system impacting the southeast U S with their ongoing severe weather
event. Deeper moisture and forcing have been confined further to the
south so far with most of the forecast area enjoying dry weather so
far today. Another mild afternoon progress despite the flow shifting
to northerly. 20Z temps ranged from the 50s to lower 60s most areas.

As has been the trend all day...threats for additional rainfall have
grown smaller and smaller as the widespread convection over the
southeast U S has robbed much of the better moisture transport north
into the area. Furthermore...the surface low track has been
suppressed further south than previously thought with the low likely
now to take a path from north central Alabama this afternoon into
the western Carolinas by morning.

Spoke of rain showers rotating around the back side of the southeast
storm has been shifting steadily north through Kentucky today and
now resides near the Ohio River as of mid afternoon. Potential
certainly exists for this to lift further north into southern
counties this evening...but confidence is low considering the
continued presence of a drier airmass through the lowest 10kft. Hi-
res guidance captures this idea well with the showers grazing
southeast counties later this evening into the overnight as the
lighter precip shield eventually encompasses eastern Kentucky and
most of Ohio with the surface low lifting into the southern
Appalachians. Really hard to justify much higher than low chance
pops this evening and overnight with the best chances existing over
the southeast portions of the forecast area.

Patchy fog will again be a potential issue tonight...especially over
the northern Wabash Valley as shallow moisture becomes trapped
beneath an inversion. With that being said...the tightening of the
pressure gradient around the intensifying low pressure to our
southeast will serve to increase northerly winds as the night
progresses with gusts developing late as well. This should keep fog
from getting out of control in terms of areal coverage.

Temps...the northerly flow will help advect colder air into central
Indiana overnight with lows dropping into the lower and middle 40s.
MAVMOS guidance looks quite reasonable.

&&

.SHORT TERM /Monday through Wednesday/...
Issued at 314 PM EST Sun Jan 22 2017

Forecast challenges focus on precip chances Monday and again
Wednesday.

The intense low pressure over the western Carolinas will spiral
northeast through the short term...tracking into the Mid-Atlantic
region...then up the coast into New England and the Canadian
Maritimes as a Nor`easter. This system will still be close enough to
the region on Monday to have a direct impact on weather before
departing off to the east Monday night to be replaced by weak high
pressure.

Deeper moisture will be pulled west around the back side of the low
pressure and into the eastern Great Lakes and eastern portions of
the Ohio and Tennessee Valleys...with a continued chance for light
rain showers and/or drizzle focused over the eastern half of the
forecast area on Monday. Further west over central Indiana...skies
will remain cloudy with a lingering stout inversion around 2kft.
Conditions will improve Monday evening as the light precip departs
off to the east. RH progs and model soundings though show scattered
of clouds will be more difficult to occur as the inversion gives way
only slowly into Tuesday morning despite the arrival of weak ridging
at the surface and aloft. Suspect more pronounced scattering of the
cloud deck will not come until Tuesday afternoon as low level flow
veers to southerly and strengthens ahead of low pressure moving
through the Plains.

That surface low to the west will track into the Great Lakes on
Wednesday and swing a cold front through the Ohio Valley. Moisture
is limited and the deeper forcing will largely remain to the north
of the forecast area. Will carry low chance pops and focus them over
the northern half of the forecast area closer to the track of the
surface low. The main impact from the passage of the low and cold
front will be the begin the process of transitioning back to a more
typical late January pattern with colder air spilling into the
region for late week.

Temps...low level thermals largely supported an overall model blend
as highs through the period should range generally from the mid 40s
to lower 50s. Lows will slide back into the 30s through the period
as well.

&&

.LONG TERM /Wednesday night through Sunday/...
Issued at 216 PM EST Sun Jan 22 2017

A broad upper trough will move from the central U.S. to the
eastern U.S. during the long term and stalling as it does so. With
the upper trough settling in over the eastern U.S., expect to see
temperatures back down to normal with access to Canadian air.
Cyclonic flow across the area combined with weak upper impulses
will bring small chances for on and off precipitation through the
period, but lack of any stronger forcing mechanism means
significant dry times are likely. Precip, should it occur, would
be in the form of rain early Wednesday night before changing over
to a rain snow mix, and then snow from Thursday night on, but
again, chances are low.

&&

.AVIATION /Discussion for 230000Z TAF Issuance/...
Issued at 600 PM EST Sun Jan 22 2017

VFR lowering to IFR overnight and continued IFR Monday.

Mid and high clouds were across central Indiana while northern
Indiana and eastern Illinois was mostly IFR with low stratus and
a few areas of fog.  Low pressure over southeast Tennessee will
move east to the North Carolina coast.  As the flow across Indiana
becomes more northerly IFR stratus will spread south across Indiana
overnight.  Could see some light fog too...but increasing winds
should preclude any dense fog.  Ceilings are expected to drop to
4 to 8 hundred feet overnight and with slight improvement by late
Monday.  Could be a few light showers too...but chances are too low
to mention in TAFs.

Northwest wind around 10 knots will become north 10 to 15 knots with
gusts to 20 knots by midnight and northwest 10 to 20 knots Monday.

&&

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

&&

$$

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



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