Area Forecast Discussion
Issued by NWS Indianapolis, IN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KIND 241712

Area Forecast Discussion
National Weather Service Indianapolis IN
1212 PM EST Fri Feb 24 2017

The AVIATION Section has been updated below.


Issued at 259 AM EST Fri Feb 24 2017

A rather potent system and its associated cold front will sweep
across Central Indiana today and this evening. As a result, the
threat for severe thunderstorms continues this afternoon and
evening across the majority of the forecast area. With this system
will also come an end to the warm temperatures as cooler air
filters in behind it. As a result, snow showers will filter into
the region tonight and tomorrow on the back side of the
aforementioned system. After that, dry conditions will return from
Saturday night through Sunday, followed by a wetter pattern early
in the week.


.NEAR TERM /Rest of Today/...
Issued at 1011 AM EST Fri Feb 24 2017

Isolated elevated convection currently over the far west central
and northwest zones along the tail end of an upper wave moving
through the Great Lakes. Short term models suggests this feature
will drift east through the area during the course of the
afternoon, reaching the eastern zones towards evening. Surface
cold front is also expected to move into the western zones after
about 242100Z. May see a gradual increase in convection through
the early afternoon along the leading feature, with more in the
way of surface based convective development towards peak heating
based on convective temperatures. Additional development expected
along the cold front. This morning`s upper air still indicates
environment favorable for severe convection, given steep mid
level lapse rates and deep layer shear. Best threat appears to be
from the mid afternoon hours on, in conjunction with the more
surface based development.

Will also raise the highs today a category, especially over the
eastern zones, based on this morning`s upper air.

Previous discussion follows.

The main focus of the near term period will be severe threat with
potent system.

Latest Day 1 SPC convective outlook continues to have the eastern
two-thirds of central Indiana under an enhanced risk for severe
weather with a slight risk over the remaining third.

Currently, the surface low is situated over northern Missouri with
some convective development along its associated warm front
stretching across the lower Midwest. Any further convective
development is expected to be minimal this morning, but winds will
start out gusty across central Indiana as a 50 plus low level jet
accompanies the warm sector. Expect south winds to be sustained at
10 to 15 mph with gusts to around 35 mph. As a result, trended
above guidance for today`s highs, topping them off in the low to
mid 70s.

With temps in the low to mid 70s and dewpoints in the 50s, there
will be decent instability for the associated cold front to work
with when it moves through this afternoon and evening. Best
forcing with the front should be during the Fri 21Z-Sat 02Z time
frame, which is a high confidence forecasted time frame. Main
threats are expected to be damaging winds and isolated tornadoes.
Confidence waivers a bit though on tornadic development because
storms could take on a more linear form.

As mentioned above the severe threat will quickly diminish by Sat
02Z as much cooler air filters in on the back side. At that point,
there will be a transition to some snow showers late in the night.
But, no accumulations are expected.


.SHORT TERM /Saturday through Sunday Night/...

Issued at 259 AM EST Fri Feb 24 2017

Snow showers will initially impact the northern counties early in
the period on the back side of aforementioned system. However, no
accumulations are expected, and it will quickly taper off by the
afternoon hours. After that, dry conditions will prevail from
Saturday night through Sunday before the next round of
precipitation enters on Sunday night. Much cooler temperatures by
then could result in some snow showers across the northern
portions of the area on Sunday night, and rain showers across the
southern counties.

Highs will take a dip on Saturday and Sunday with readings in the
30s and 40s, respectively. Meanwhile, overnight lows will be in
the 20s and 30s on Saturday night and Sunday night, respectively.


.LONG TERM /Monday through Thursday/...
Issued at 222 AM EST Fri Feb 24 2017

Models in general agreement that a frontal system will be moving
over the area Tuesday night into Wednesday. Good return flow ahead
of this system supports the widespread superblend pops Monday night
into Wednesday morning. Model instability progs warrant thunder
mention Tuesday afternoon and evening.

Prior to that, an upper wave could generate a few showers Monday.
Partial thicknesses and model soundings suggest some snow could mix
in during the morning, mainly north.

Temperatures will return to above normal ahead of the midweek
frontal system, but then fall back to seasonable by Thursday in its
wake. Superblend handles this well. Will not make any changes.


.AVIATION /Discussion for 241800Z TAF Issuance/...
Issued at 1212 PM EST Fri Feb 24 2017

Brief restrictions likely within convection later this afternoon
and evening...then MVFR ceilings developing Saturday morning.

Powerful cold front moving across Illinois early this afternoon
with convection beginning to fire out in front of it into the
Wabash Valley. Expect this trend to continue with expanding and
intensifying storms impacting the terminals from mid afternoon
into the evening. Will highlight with VCTS and prevailing showers
at the terminals for now. As convection evolves this afternoon...
will likely introduce tempos for more specific impacts to the
sites as confidence grows. Very likely to see higher wind gusts in
excess of 45 to 50kts for a brief period accompanying the storms
and perhaps hail as well.

The cold front and storms will sweep east of the terminals by mid
evening with much colder air spreading in behind the front. May
see a brief period with clearing skies overnight before lower MVFR
ceilings arrive approaching daybreak Saturday with the wraparound
moisture. Scattered snow showers will also arrive and may impact
the terminals during the morning.

Gradient winds will be a major factor in airport operations
throughout the forecast period with a tight pressure gradient
present around the strong low pressure moving through the Great
Lakes. Expect periodic gusts outside of storms this afternoon and
evening up to 30-35kts from the southwest. Once the front passes...
winds will veer to westerly with gusts at or in excess of 25kts
continuing into Saturday.





AVIATION...Ryan is the U.S. government's official web portal to all federal, state and local government web resources and services.