Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 222014
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
314 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 222100Z TAF Update/...
Issued at 314 PM EST Sun Jan 22 2017

Minor tweaks to ceilings based on current observations. Also
pulled VCSH wording out of the terminals until mid to late evening
at the earliest.

18Z discussion follows.

VFR conditions expected into this evening with MVFR to IFR
ceilings developing overnight into Monday.

Predominantly mid and high level clouds over the region late this
morning...although clearing has developed across northern
portions of central Indiana. This has enabled a quick bump in near
surface warming and have seen isolated convection develop near
KLAF since 16Z in combination of a subtle convergence zone
present.

Likely to see additional isolated showers develop through the
course of the afternoon but the more widespread rainfall is
likely to remain south of all terminals through sunset. With the
possible exception of KLAF where sub-IFR conditions and fog are
hovering only about 15-20 miles NW of the terminal...expect VFR
conditions through the duration of the afternoon.

Model soundings do indicate the development of a stronger
inversion in the near surface layer tonight as northerly flow
increases over the region on the back side of the deep low
pressure over the southeast U S. Do anticipate ceilings falling to
around 1000ft or slightly lower overnight and into Monday morning
with isolated showers present. The northerly winds will increase
with gusts to 20-25kts developing predawn Monday and continuing
for most of the day.

&&

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

&&

$$

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



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