Area Forecast Discussion
Issued by NWS Indianapolis, IN

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988
FXUS63 KIND 211930
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
230 PM EST Sun Jan 21 2018

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

&&

.SYNOPSIS...
Issued at 325 AM EST Sun Jan 21 2018

Low pressure developing over the central plains will move to the
great lakes by Monday night and up the St. Lawrence valley Tuesday
and Wednesday.  A trailing cold front will push east across our area
late Monday.

Temperatures will continue to warm today into early Tuesday and then
become cooler by Tuesday.

An area of high pressure will move east across the Ohio valley by
Thursday.  Another area of low pressure will bring rain showers and
mild temperatures our way by Saturday.

&&

.NEAR TERM /This afternoon/...

Issued at 955 AM EST Sun Jan 21 2018

Surface analysis late this morning shows low pressure over Kansas
with a warm front extending northeast all the way to northern
central Indiana...laid across LAF and OKK. Visibilities and Fog
remained very low along and north of the warm front. GOES16 shows
extensive cloud cover across Central Indiana...much of which was
within the warm sector. However it should be noted that
visibilities were better on the south of the front.

Models suggest warm air advection to continue through the day and
lower level moisture remains predominate within the Time heights
and forecast soundings....with dry air aloft and weak lift in
place. This is the classic recipe for fog and drizzle. Thus will
continue to keep the fog and drizzle aspect to the forecast
through the afternoon. Some daytime mixing and an expected
northern lift of the warm front may allow the dense fog advisory
to be ended at noon...but we will wait a couple of hours before
crossing that bridge.

&&

.SHORT TERM /Tomorrow through Tuesday Night/...
Issued at 325 AM EST Sun Jan 21 2018

Strong low pressure will move across the upper midwest into the
Great lakes Monday.   A trailing cold front will push east across
Indiana Monday.  Models indicate number showers will occur and there
may be just enough instability to mention isolated thunder over
western sections Monday morning.

The low pressure system will move east across the great lakes
Monday night and a cold front extending south across Indiana will
move east.  An upper low over northern Illinois will produce numerous
light showers over northern sections and scattered showers in the
south.   Model soundings and BUFKIT indicate a change over to snow
showers by daybreak Tuesday.

Tuesday...will be much cooler with scattered light snow showers.
The ground should be fairly warm which should limit accumulations.
However far northern sections could see up to a half inch Tuesday.

Cut daytime temperatures slightly Tuesday with strong cold advection.

Only other change was to increase wind speeds Monday into Tuesday
as models indicate a fairly strong pressure gradient. In most cases
used CONSALL winds instead of Superblend.

&&

.LONG TERM /Wednesday Night through Sunday/...

Issued at 230 PM EST Sun Jan 21 2018

ECMWF shows an upper trough will be exiting the area on Wednesday
night as surface high pressure builds across the area. This will
keep dry weather across the area along with mild temperatures
through late Friday Night as strong ridging builds aloft and
passes gradually passes east of Indiana.

By early Saturday morning the ridge is well east of Indiana and a
warmer SW flow of air will be in place across the Ohio Valley.
ECMWF shows another deep trough entering the plains states along
with another cold front poised to sweep through the Ohio Valley
on Saturday and Sunday. With excellent gulf flow ahead of the
front and good forcing in place...pops suggested by superblend
appear reasonable.

&&

.AVIATION /Discussion for the 211800Z Tafs/...

Issued at 1237 PM EST Sun Jan 21 2018

LIFR conditions are expected at LAF...IFR conditions will be found
elsewhere.

A warm front in place across LAF...Oik to North of MIE
will continue to be the focus for dense fog over the next several
hours. Warm air advection over snow pack will continue to result
in dense fog through the afternoon.

Conditions may improve to IFR at all locations later today as the
warm front is expected to gradually lift northward as low
pressure and cold front approaches front the west. Rain showers
and IFR/MVFR conditions are expected on Monday morning as the
cold front approaches. Time heights and forecast soundings show
excellent lower level moisture and ample lift.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 4 PM EST this afternoon for INZ021-
028>031-035>041-043-044.

&&

$$

SYNOPSIS...JH
NEAR TERM...Puma
SHORT TERM...JH
LONG TERM....Puma
AVIATION...JP



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