Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 221828
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
128 PM EST Wed Feb 22 2017

.UPDATE...
The LONG TERM Section has been updated below.

&&

.SYNOPSIS...
Issued at 312 AM EST Wed Feb 22 2017

Warm conditions will continue through Friday, when a brief return to
normal temperatures for the weekend. Warmer air looks to make a
comeback next week. A series of frontal systems will keep periodic
chances for precipitation the next week. One of them will be a
strong cold front on Friday, which could bring strong to severe
thunderstorms.

&&

.NEAR TERM /Rest of Today/...
Issued at 1002 AM EST Wed Feb 22 2017

Widespread dense fog continues over about the western half of the
forecast area. This morning`s upper air suggest the moisture layer
is quite shallow, so should see conditions improve over the next
couple of hours. Will extend the Dense Fog Advisory in time until
221700Z, and also add Tipton and Howard counties based on current
observations.

Will keep the forecast highs as is for now, as upper air
observations generally support them. If low clouds and fog linger
longer than expected, highs will probably be too warm.

Previous discussion follows.

Patchy fog continues to develop across the area this morning, but so
far the cloud cover is keeping most visibilities in check. Will
likely need to mention fog early in the period.

The area will remain in between systems today, so the forecast will
be dry. However, there looks to be a good amount of cloud cover
today. Time-height sections show plenty of low level moisture, and
forecast soundings show an inversion as well.

Thus will keep skies mostly cloudy this morning, with some partial
decrease in the afternoon.

By going with more clouds today, will stick with a blend of
temperatures, which keeps highs in the mid to upper 60s. If more
sunshine appears, the temperatures will warm quickly and could reach
the lower 70s. However, would rather be pessimistic about
temperatures and have reality exceed them than forecast record
temperatures and not get there. (Indy`s record high today is 70).

&&

.SHORT TERM.../Tonight through Friday night/
Issued at 312 AM EST Wed Feb 22 2017

Models are close enough that the SuperBlend initialization
was accepted for most items.

A cold front will move into northwest Indiana late tonight. Most
forcing with it will be well to the north closer to a northern
stream upper wave. Thus will keep the forecast dry tonight.

The front will sink farther into the forecast area Thursday morning,
but again forcing is weak. During the afternoon, flow aloft
increases from the south. This will create lift and allow for some
low PoPs Thursday afternoon.

As the flow continues to increase Thursday night, forcing will
increase and allow for higher PoPs, but still no higher than the
chance category. Highest PoPs will be across northern sections,
along and north of the now warm front as it moves north.

On Friday, a surface low will deepen well to our northwest, and a
cold front will move through the area. Moisture will be decent
thanks to a good southerly flow (850mb near 50kt). Looks like there
will be enough shear and instability for some strong to severe
storms, especially if sunshine can break through the clouds. The
initialization`s likely PoPs look good.

PoPs will be high Friday night as the upper trough moves through.
Highest PoPs will be in the evening. Much colder air will flow in as
well, with lows in the 30s by Saturday morning.

&&

.LONG TERM /Saturday Night through Wednesday/...

Issued at 125 PM EST Wed Feb 22 2017

Models vary a bit on system paths and timing this period; blended
solution accepted.

Colder weather will start this period as a high pressure ridge
moves from the Plains to the Appalachians. A weak short wave
embedded in the flow aloft coupled with slight low level warm
advection will produce a period of light snow Sunday night mixing
with and changing to rain Monday midday before departing. GFS
suggests potential for brief heavy snow Monday morning with this
wave but that appears to be an outlier for now.

Weak high pressure will slide quickly across the area Monday
night as as a more substantial system begins taking shape in the
southern Plains. This system will bring a return of warmer air,
rain, and possibly thunderstorms again, Tuesday into Wednesday.

Temperatures will begin the period near normal but trend back
above normal by Tuesday as that next system strengthens warm
southerly flow. Blend of model temperature forecasts was used.

&&

.AVIATION /Discussion for 221800z TAFs/...

Issued at 1202 PM EST Wed Feb 22 2017

Widespread LIFR and IFR stratus has been slow to lift, thin and
break. Expect with continued sunshine from above and mixing below
from surface winds now near 10kts that wholes in cloud deck will
expand as it slowly rises with surface heating reaching broken VFR
by around 2100z. Given that low level moisture remains prevalent,
and approaching surface front tonight aids in convergence,
anticipate redevelopment of an IFR cloud deck before daybreak
Thursday, or 231000z. Since winds are expected to remain above 5
knots overnight, do not expect re-occurrence of dense fog like
this morning.


&&

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

$$

SYNOPSIS...50
NEAR TERM...50/JAS
SHORT TERM...50
LONG TERM....Tucek
AVIATION...Tucek



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