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Area Forecast Discussion
National Weather Service Indianapolis IN
1250 PM EST Sat Dec 3 2016

.UPDATE...
The AVIATION Section has been updated below.

&&

.SYNOPSIS...
Issued at 315 AM EST Sat Dec 3 2016 

An upper level system will bring some precipitation to the area late
tonight into Sunday. Another system will bring rain early next
week. Much colder air will move in mid week and could bring some
snow with it. Below normal temperatures will then continue into next
weekend.

&&

.NEAR TERM /This Afternoon/...

Issued at 959 AM EST Sat Dec 3 2016

Surface analysis late this morning shows weak high pressure in
place across Illinois and Indiana. Water vapor shows a surge of
tropical moisture pushing northeast across Texas and toward the
Ohio valley. Visible Imagery shows some clearing across the
western parts of the Indiana...however as mid and high cloud
arrive in the area within the moist flow aloft...any sunshine
should not last.

Forecast soundings and Time heights show saturation aloft through
the afternoon...with a progression of saturation building toward
the ground as the day progresses. The 850mb surface does shows
cold air leaving the area today...but little in the way of
sunshine will result in minimal heating. Thus will keep skies
mostly cloudy today...with temps cooler than the MAV. 

&&

.SHORT TERM.../Tonight through Monday night/
Issued at 315 AM EST Sat Dec 3 2016 

Models are close enough that the SuperBlend initialization 
was accepted, unless noted below.

This evening should remain dry with little or no forcing
around. Isentropic lift then increases overnight.  

It should take a while for the atmosphere to moisten up
enough for precipitation to get to the ground. Went slight 
chance to low chance category PoPs by late tonight across the
southwest forecast area. 

Forcing increases during the day Sunday as the upper trough moves
in. An inverted surface trough will be to our south with another
surface trough off to the northwest. An upper jet will be overhead.

Feel that there will be enough forcing and moisture to at measure
at least some light QPF across much of the area on Sunday, so went
likely PoPs many areas by Sunday afternoon. This is a little higher
than the initialization, but the outlier drier NAM is bringing the
initialization down.

Forcing will quickly exit the area, so only went slight chance PoPs
far east Sunday evening. Monday will then be dry across all but the
far south, then precipitation chances increase south to north Monday
night with the approach of the next system. 

As for precipitation type, temperatures will be cold enough for snow
late tonight, then readings will warm enough for mainly a mix of
rain and snow Sunday morning. Sunday afternoon should see rain all
areas, but it may be borderline across the far northwest based on
forecast soundings. For Monday into Monday night, temperatures will
be warm enough for just rain for most of the period (a brief mix of
rain and snow is possible north early).

Any snow accumulation late tonight into Sunday morning will be less
than an inch, and mainly confined to the far west and northwest.

&&

.LONG TERM /Tuesday through Saturday/...
Issued at 331 AM EST Sat Dec 3 2016

Rainmaker will be moving through the Ohio Valley early in the long
term period, with conditions turning sharply cooler later in the
week as a slug of cold air drops into the region. Models continue to
differ in their handling of Wednesday night system but are coming a
bit closer together on timing. Euro produces are more robust surface
reflection in contrast to the GFS near complete lack of identifiable
surface features. This impacts the blended initialization, and may
be biasing precipitation amounts low if the Euro verifies - in which
case a light but potentially low end advisory level snowfall may be
possible - particularly considering the relative lack of wintry
precipitation thus far this season. Made adjustments to blended
initialization Wednesday night to better capture this potential.

&&

.AVIATION /Discussion for the 03/1800Z TAF Issuance/...

Issued at 1222 PM EST Sat Dec 3 2016

Conditions will continue to fluctuate around the MVFR/VFR mark
through this afternoon as low clouds linger. Expect conditions to
predominantly become VFR category by this evening and persist into
tomorrow. Focus then turns to an upper level disturbance progged
for tomorrow morning. Precipitation will initially start out in
the form of a rain/snow mix, but chances are still too low to
mention in TAFs at this time. The rain/snow mix will eventually
transition to all rain by tomorrow afternoon, which is conveyed
in the KIND TAF. Conditions will quickly deteriorate to MVFR or
worse late tomorrow afternoon though when the bulk of the
precipitation moves through. Winds will initially be
northwesterly, becoming southeasterly by tomorrow morning.
Sustained speeds will range between 5 to 10 kts.

&&

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

&&

$$

SYNOPSIS...50 
NEAR TERM...PUMA
SHORT TERM...50 
LONG TERM...NIELD
AVIATION...TDUD

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