Areal Flood Warning 33, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
1227 AM EST Wed Dec 29 2021

.Forecast Update...
Issued at 1227 AM EST Wed Dec 29 2021

Visibilities on the whole have improved across much of the advisory
area. However, visibilties are still unstable with bouncing noted at
numerous sites based on observations. Thus, will not yet cancel the
Dense Fog Advisory.

&&

.Short Term...(This evening through Wednesday night)
Issued at 309 PM EST Tue Dec 28 2021

Some near term changes to the grids included adding mixed snow
across northern counties following several photos and reports from
the public of flakes of various sizes from West Lafayette to the I-
69 corridor...and more importantly a report of patchy, thin slush on
roads north of Frankfort in Clinton County.  Despite the approaching
surface lows' more southerly trend towards the Ohio Valley, and
corresponding easterly winds therefore backing to the ENE so far
today...confidence remains high that WAA aloft will maintain a
primary rain event, with antecedent ground warmth allowing
essentially no impacts.  Snow may remain the primary precipitation
type for much of Carroll and Howard counties through this afternoon,
yet any light accumulations here would be confined to rooftops and
other elevated surfaces.

Otherwise, today's generally light to moderate rain event had
brought 0.40-0.75 inches of rain to many locations across the CWA
through early this afternoon.  The earlier warm advective rain was
departing northeastern zones, while the second period of rainfall
had already entered most western zones...while mainly dry conditions
had at least briefly entered south-central counties.  Therefore more
light-moderate rain will cross the region over the next several
hours, before ending from west to east this evening as forcing
departs to the northeast and decent mid-level subsidence arrives
rather quickly from the west.  Additional rainfall of 0.10-0.50 is
expected with greater amounts to the north...and overall totals 0.50-
1.00 for most locations.  Low cloud will linger into the overnight,
perhaps only briefly scattering out across southwestern zones.

After a short dry period late tonight and Wednesday morning...the
active zonal west-southwesterly rain machine will bring yet another
wave across the Mid-West, albeit much weaker.  Chances of rain will
spread over central Indiana from south to north through the late day
and early evening.  The brief period of scattered showers will taper
off from west to east late Wednesday night as the disturbance
crosses southern Indiana.  As was the case today, marginally cold
soundings may promote wet snow mixing in with whatever light showers
cross far northwestern and north-central counties in the evening.
Expect little or no impacts per antecedent warm ground, and air
temperatures progged to stay in the mid-30s during any hydrometeors.
A greater impact for much of the short term will be the threat of at
least patchy fog, generally over central and northern counties
following today's rain and diminishing winds this evening.

Temperatures will hold in the 30s along and north of I-70 tonight
while readings drop into the 40-45 range across the southern
zones. Readings will rebound modestly Wednesday amid considerable
cloudiness and light northerly flow with highs ranging from the
low 40s far north to the low 50s for Bloomington and south.
Wednesday night will drop to the mid 30s to low 40s across the
region.

&&

.Long Term...(Thursday through Tuesday)
Issued at 300 PM EST Tue Dec 28 2021

Thursday Through Thursday Night.

Rain will come to an end across central Indiana late Wednesday night
as the forcing associated with an 850 to 700mb jet exits the area.
Dry weather then briefly returns for Thursday but with the polar air
locked well into Canada, temperatures look to remain well above
average.  Model soundings still show moderate saturation at the mid
levels, so expect at least partly cloudy skies to continue through
the overnight hours before the thicker clouds arrive Friday.

Friday Through Tuesday.

The next rain producing system will move out of the Southern Rockies
and track to the northeast Thursday into early Friday with
precipitation for central Indiana beginning Friday afternoon.
Confidence in the track of the low has increased but there remains
many of the mesoscale features that remain uncertain that will
impact the axis of heaviest rain or the threat for thunderstorms.
Current thoughts are the axis of heaviest precipitation will be
south of the Ohio River with northerly surface flow across much of
the area. This will keep central Indiana out of the warm sector and
keep thunder or strong storm threats to near zero.

If the track inches northward a bit, the southern counties could see
a few thunderstorms. A weak TROWAL may allow for some snow to mix
into the northern counties Saturday into early Sunday after the
initial round of rain, but confidence in both the strength of the
TROWAL and how could the airmass is are both low at this time. High
pressure and seasonable weather then arrives Monday into Tuesday as
high pressure builds across the area.

&&

.Aviation...(06Z TAF Issuance)
Issued at 1008 PM EST Tue Dec 28 2021

IMPACTS:

-- At least temporarily dense fog (one quarter mile or less) tonight.

-- LIFR or lower ceilings possible.

-- Light and variable winds should trend northwesterly and
eventually northeasterly.

Discussion:

Northwest of the band of rain that is departing, where the ground is
wet and low-levels are very moist, even modest cooling has resulted
in fog tonight. This is not a classic radiative or advective
scenario since both drivers are relatively modest. Thus, some
variability in visibility may be experienced through the night.
Although the lowest visibility is occurring near IND westward
along/near the I-70 corridor late this evening, further expansion
eastward and southeastward is likely. Improving conditions are
expected during the morning. Until then, expect some amendments
based on observational trends due to uncertainty on ceiling heights
and visibilities.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 7 AM EST this morning for INZ036-037-
039-040-045>049-052>057.

&&

Update...50
Short Term...AGM
Long Term...White
Aviation...BRB

Hazardous Weather Outlook
National Weather Service Indianapolis IN
1128 PM EST Tue Dec 28 2021

INZ021-028>031-035>049-051>057-060>065-067>072-300430-
Carroll-Warren-Tippecanoe-Clinton-Howard-Fountain-Montgomery-Boone-
Tipton-Hamilton-Madison-Delaware-Randolph-Vermillion-Parke-Putnam-
Hendricks-Marion-Hancock-Henry-Vigo-Clay-Owen-Morgan-Johnson-Shelby-
Rush-Sullivan-Greene-Monroe-Brown-Bartholomew-Decatur-Knox-Daviess-
Martin-Lawrence-Jackson-Jennings-
Including the cities of Delphi, Flora, Williamsport, West Lebanon,
Lafayette, West Lafayette, Frankfort, Kokomo, Attica, Covington,
Veedersburg, Crawfordsville, Lebanon, Zionsville, Tipton, Fishers,
Carmel, Noblesville, Anderson, Muncie, Winchester, Union City,
Farmland, Parker City, Clinton, Fairview Park, Rockville, Montezuma,
Rosedale, Greencastle, Plainfield, Brownsburg, Danville,
Indianapolis, Greenfield, New Castle, Terre Haute, Brazil, Spencer,
Gosport, Martinsville, Mooresville, Greenwood, Franklin,
Shelbyville, Rushville, Sullivan, Carlisle, Shelburn, Farmersburg,
Linton, Bloomfield, Jasonville, Worthington, Bloomington, Nashville,
Columbus, Greensburg, Vincennes, Washington, Loogootee, Shoals,
Bedford, Mitchell, Seymour, and North Vernon
1128 PM EST Tue Dec 28 2021

This hazardous weather outlook is for central Indiana.

.DAY ONE...Tonight.

Areas of fog will continue through the night. Fog may be dense in
spots, with visibility of a quarter of a mile or less. Visibility may
vary greatly over short distances.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

&&

More information, along with other weather, hydrological and climate
information can be found at http://weather.gov/ind

Special Weather Statement
National Weather Service Indianapolis IN
945 PM EST Tue Dec 28 2021

INZ036-037-039-043>048-051>056-060>063-290900-
Montgomery-Boone-Hamilton-Vermillion-Parke-Putnam-Hendricks-
Marion-Hancock-Vigo-Clay-Owen-Morgan-Johnson-Shelby-Sullivan-
Greene-Monroe-Brown-
Including the cities of Crawfordsville, Lebanon, Zionsville,
Fishers, Carmel, Noblesville, Clinton, Fairview Park, Rockville,
Montezuma, Rosedale, Greencastle, Plainfield, Brownsburg,
Danville, Indianapolis, Greenfield, Terre Haute, Brazil, Spencer,
Gosport, Martinsville, Mooresville, Greenwood, Franklin,
Shelbyville, Sullivan, Carlisle, Shelburn, Farmersburg, Linton,
Bloomfield, Jasonville, Worthington, Bloomington, and Nashville
945 PM EST Tue Dec 28 2021

...AREAS OF FOG EXPECTED TONIGHT...

Fog is expected across portions of central Indiana through the
night. Visibility may fall to under one half mile in some
locations causing hazardous driving conditions. Drivers may
experience rapid visibility changes. Improving conditions are
expected by early Wednesday morning.