Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 190240
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
940 PM EST Mon Feb 18 2019

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

&&

.SYNOPSIS...
Issued at 940 PM EST Mon Feb 18 2019

High pressure was in place from the northern Plains to the Ohio
valley. This high pressure system will bring dry and cool weather to
Central Indiana through early Tuesday Evening.

A strong warm front will push toward Central Indiana late Tuesday
Night and pass across the state on Wednesday as Low pressure
passes northwest of our state. This will result in a wintry mix of
precipitation late Tuesday night and early wednesday
morning. All of the precipitation is expected to change to rain by
Wednesday afternoon.

High pressure and dry weather is expected to return for
Thursday...along with warmer temperatures that should melt any
lingering snow from the previous system.

More rain chances will return next weekend along with above
normal temperatures as another storm system pushes through the
plains toward the Great Lakes.

&&

.NEAR TERM /Tonight/...
Issued at 940 PM EST Mon Feb 18 2019

Kept flurries in for the rest of the evening per radar and ob trends.

Previous discussion follows...

Issued at 625 PM EST Mon Feb 18 2019

Had to add slight chances snow showers through 01z per radar and obs.

Previous discussion follows...

Issued at 309 PM EST Mon Feb 18 2019

Surface analysis early this afternoon shows high pressure
stretching from the northern plains to Missouri. Cool NW surface
flow was in place ahead of the High across Indiana. A stream of
tropical moisture was shown aloft across the deep south. Radar
continues to show a some very light snow showers/flurries on
radar.

Models continue to show a deterioration of the low level moisture
desk this evening as the high pressure system build across the
Great Lakes and Indiana. Subsidence also continues to strengthen
through the night as dry air appears in place aloft. Looking at
visible satelitte pictures...clear skies were found upstream
across Wisconsin and NRN Illinois. Thus will trend toward a
decreasing cloudiness type forecast tonight as the high pressure
and dry air build across Indiana. Given the mostly clear skies
expected along with the light winds...will trend temps at or below
the forecast builder blends.


&&

.SHORT TERM /Tuesday through Thursday/...

Issued at 309 PM EST Mon Feb 18 2019

Dry weather is expected to persist on Tuesday and Tuesday evening
before a storm system arrives in the region for Late Tuesday night
and Wednesday.

On Tuesday...The GFS and NAM show a ridge axis in place across
KS...NB and SW SD...allowing for some lee side subsidence across
the upper midwest...spilling into the Ohio Valley. Forecast
soundings show a dry column through the day as ridging builds
aloft. Thus will trend toward a dry forecast.

On Tuesday night the GFS and NAM suggest a deep trough over the
western plains as a strong storm wave is ejected out of the trough
into the Ohio Valley. This results in development of a strong
surface low over the plains with a strong warm front surging
northward toward Indiana. By 09Z Wed...forecast soundings show
deep saturation arriving with most of the column below freezing.
Thus initial onset of precip on Tuesday Night should be snow.
However as the morning progresses...warm air advection is
expected to continues and warming surges into the mid levels that
should result in a a period of FZRA near 12-14Z. Warm air is
suggested to surge into the area through the day and by
afternoon...the entire saturated column is well above freezing.
Thus an overall trend toward rain through the day....although a
few hours during the morning should result in brief slick
conditions and warming and rain through the day should alleviate
the situation. Other favorable dynamic in play fore precip at this
time include very favorable isentropic lift on Wednesday morning
as seen on the GFS 295K surface along with a moisture rich air
mass with specific humidities near 5 g/kg. Thus will trend pops
on Tuesday night and a Wednesday near 100 as confidence is high.
Given the expected precip will trend lows warmer than the forecast
blends and highs cooler.

On Wednesday night and Thursday dry air and subsidence arrives
within the column as weak ridging builds across the plains. Some
trapped lower level moisture appears present on Wednesday night
that could result in a few clouds or lingering sprinkles of
drizzle...however the best forcing will be lost at that point.
High pressure looks to settle across the area on Thursday as
forecast soundings dry out and dry weather will be expected. Will
stick close to the forecast builder blends here.

&&

.LONG TERM /Thursday Night through Monday/...
Issued at 306 PM EST Mon Feb 18 2019

High pressure early in the long term period will keep things dry
and somewhat cooler, but a northward return of the frontal zone,
along with development of a strong low pressure system over the
weekend in response to an upper level low pushing eastward out of
the desert southwest, will bring widespread precipitation to the
area as early as late Friday night into Saturday, continuing into
late Saturday night into Sunday. Temperatures should be warm
enough for the vast majority of this precipitation to fall as
rain.

Cannot entirely rule out thunder, although often during this time
of year, the northern extent of a potential area of weak
destabilization, which the area would be in, ends up being sapped
by widespread cloud cover, precipitation, and stronger activity
to the south. Will keep thunder mentions out for now and monitor
as the week wears on.

Raised blend temperatures a bit Friday into Saturday night with
strong warm advection ongoing, and lowered blend temps Sunday as
model 850 temps suggest frontal passage would be early in the day
and prevent much of a rise over Saturday night lows.

&&

.AVIATION /Discussion for the 18/03Z IND TAF Update/...
Issued at 930 PM EST Mon Feb 18 2019

No changes needed to the TAF.

Previous discussion follows...

Issued at 625 PM EST Mon Feb 18 2019

MVFR and worse conditions at IND through 01z per radar and obs.
Otherwise, moderate to good confidence conditions will become VFR
with decreasing clouds.

Winds will start of northwest 6 knots or less and shift to east
after 20z Tuesday.

&&

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

$$

SYNOPSIS...Puma
NEAR TERM...Puma/MK
SHORT TERM...Puma
LONG TERM...50
AVIATION...MK


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