Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 200330

Area Forecast Discussion
National Weather Service Indianapolis IN
1130 PM EDT Sat May 19 2018

The AVIATION section has been updated below.


Issued at 350 PM EDT Sat May 19 2018

Scattered storms will move east this evening but return Sunday and
the active pattern of continued chances for showers and storms will
keep on until Tuesday evening. At this point the front and surface
system will finally lift away from the area. After a few dry days,
chances for rain and a few storms could return going into the
weekend. Temperatures will continue to run above normal.


.NEAR TERM /Overnight/...
Issued at 1014 PM EDT Sat May 19 2018

Skies have become mostly clear this evening in the wake of the
afternoon convection with just cirrus leftover. 02Z temperatures
ranged from the upper 60s to the mid 70s.

Bit of a convoluted forecast overnight from a convective
standpoint with no clear signal at any substantial impacts from
storms through daybreak Sunday. The convective cluster over
Missouri has been poorly sampled by CAMs all guidance
has consistently had the storm complex too far north and more
intense than reality has shown. Suspect the ongoing activity to
the southwest of KSTL will ride the instability gradient into the
lower Ohio Valley over the next several hours and recent satellite
loops indicate that turn to the SE has likely already occurred.

The northern extent of the convection is in the St Louis vicinity
currently and it is plausible that this might clip the lower
Wabash Valley around or shortly after 06Z. But overall confidence
is low in any significant convection making into into the
forecast area later tonight. Only weak instability remains at this
time with a fair amount of inhibition present. With the remnant
frontal boundary lingering across the area...will maintain a low
pop for any isolated convection. Otherwise...expect most remain
dry through the night.

Zone and grid updates out.


.SHORT TERM /Sunday through Tuesday/...

Issued at 350 PM EDT Sat May 19 2018

Chances for storms will ramp up through the day on Sunday with a
surface wave moving overhead and through the area on a stalled
frontal boundary. Shear will be maximized near the boundary...but
isn`t all that impressive elsewhere. Instability should ramp up, but
this is somewhat dependent on the amount of cloud debris left from
any overnight convection. Thus there is potential for some severe
storm development Sunday afternoon into the evening, but confidence
is still pretty low given the uncertainty.

Sunday night the upper wave will move through and kept pops in the
high chance category during that time. On Monday the surface wave
and front will continue to provide a focusing mechanism for
development, and thus keeping chances for showers and storms in the
forecast over at least the eastern half of the area. Again a warm
moist unstable air mass, so marginal risk for severe seems a good

On Tuesday the front and surface wave finally lift northeast away
from the area, allowing pops to drop off for all but the eastern

Temperatures during this period will be highly dependent on where
exactly the boundary sets up and the effect this has on cloud cover.
Thus stuck with the consensus blend but think there could be a much
tighter gradient somewhere in the forecast area than what the
consensus shows.


.LONG TERM /Tuesday night Through Saturday/...
Issued at 235 PM EDT Sat May 19 2018

Models are in good agreement on the overall synoptic pattern which
lends good confidence in the forecast trends.

Models agree that an upper low will develop over southern California
early next week within west coast troughing in advance of an
Aleutians vortex. The upper low will be over the Great Basin at the
start of the long term and then open up as an upper trough and then
arc around an expansive central U.S. upper ridge. The trough is
expected to reach the western Great Lakes by Saturday. This would
suggest a warm and dry pattern through Thursday with increasing
chances of weekend thunderstorms. Blend handles this well.


.AVIATION /Discussion for 200600Z TAF Issuance/...
Issued at 1130 PM EDT Sat May 19 2018

VFR conditions expected throughout much of the forecast period.
Low confidence in convective impacts and timing.

Predominantly dry weather is expected through Sunday morning as the
region resides under weak ridging aloft. Most of the hi-res guidance
has backed off on convection moving into the region for the rest of
the night with storms over eastern Missouri moving southeast towards
the lower Ohio Valley. Cannot rule out isolated convection through
the morning with the frontal boundary lingering over the
region...but this is not enough for inclusion into the forecasts at
this point.

High uncertainty exists on how and if a convective complex will
develop over the region Sunday afternoon and evening. Depending on
how much cloud debris lingers over central Indiana in the morning
will ultimately determine how much heating and instability develops
later in the day. The arrival of an upper level wave late afternoon
into the evening may serve as a spark to greater convective coverage
and considering the presence of an unstable airmass and the remnant
frontal boundary...will maintain a VCTS mention at all terminals
from mid afternoon into the evening.

Wind direction is likely to be variable throughout the forecast
period at less than 10kts.





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