358 
FXUS63 KIND 121429
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
929 AM EST Thu Jan 12 2023

.Forecast Update...
Issued at 928 AM EST Thu Jan 12 2023

Light rain continues to move across central Indiana across a narrow 
axis of mid level lift as the bulk of the precipitation pushes east 
across Kentucky and southern Ohio.  Made adjustments to the hourly 
POPs through the morning to try and fine tune precipitation timing 
and extent.  With the elevated instability gone, also pulled the 
thunder mention through the rest of the day.

In the aftermath of the heavier precipitation, the dense fog has 
cleared out with lowered visibilities of 3-6 miles continuing across 
the area.  These lowered visibilities will continue for the next few 
hours with the lingering moisture, but increasing wind speeds will 
help further improve conditions.  Latest ACARs soundings show that 
the near surface inversion has lifted to around 1000ft which is 
allowing for winds up to 30 mph to mix down and expect that 
inversion to slowly continue to lift and allow for more frequent 
gusts to 30 mph.

Temperatures will slowly fall through the day today with the 
northerly component now to the wind with temperatures in the mid to 
upper 30s for much of the area by later this evening.  No major 
changes needed other than fine-tuning POPs and Wx.

&&

.Short Term...(Today and tonight)
Issued at 612 AM EST Thu Jan 12 2023

Today...

* DENSE FOG ADVISORY FOR NORTHEAST HALF OF CENTRAL IN THROUGH 9AM EST

* Widespread rain arrives by 10-11z

* Light scattered snow showers possible overnight 

Widespread dense fog is ongoing across much of central Indiana. 
ACARS soundings show a well mixed dry layer remains in the mid-
levels with light surface winds. This combined with a highly 
saturated surface will keep dense fog around over the next few hours.

Moisture advection ahead of an approaching low will saturate the 
aforementioned dry layer with widespread precipitation expected by 
11z as the surface low moves across the Ohio River Valley. Look for
visibilities to improve as rain, which could be heavy at times, 
moves in. Model soundings show weak elevated instability with the 
potential for some embedded thunderstorms within the strongest 
showers. A few CG lightning strikes will be possible, but most 
lightning should stay at cloud level. The heaviest precipitation is 
likely to be focused across the southern half of central Indiana 
where stronger forcing and PWATs near the 90th percentile will 
align. Look for QPF amounts between 0.50 to 1 inch over this area 
with lesser amounts further north. The surface low will continue 
deepening as it moves eastward with a tightening pressure gradient 
expected over central Indiana. Due to this, 30-35 mph gusts will be 
possible late this afternoon through midnight. 

Tonight...

Rain will transition to a rain/snow mix and eventually all snow 
overnight as cold air advection filters in on the backside of the 
surface low. Precipitation will be light as this transition occurs 
due to drier pushing in aloft. However, a northerly wind will lead to
a long fetch off of Lake Michigan late overnight and begin to 
increase low-level moisture. This combined with steepening lapse 
rates from CAA aloft should allow scattered lake enhanced snow 
showers to develop. Only light accumulations are expected on grassy 
surfaces. Cannot rule out slightly higher accumulations in some 
spots if banding sets up.

&&

.Long Term...(Friday through Wednesday)
Issued at 258 AM EST Thu Jan 12 2023

* Scattered snow showers and flurries Friday
* Multiple chances for rain next week

Highly amplified and chaotic upper flow pattern will continue 
through the extended period...as dry weather over the weekend will 
be bookended by snow showers and breezy conditions Friday as the 
system for late week pulls away to the northeast...followed by a 
pair of strengthening surface lows poised to track into the region 
next week that will flip the Ohio Valley back into an active 
weather regime.

Cold air will have established over central Indiana by daybreak 
Friday as an upper trough amplifies to our east with precipitation 
lingering across the forecast area in the form of light snow. A 
trailing wave aloft on the back side of the parent trough will pivot 
across the region during the day Friday and will interact with 
lingering low level moisture to generate scattered snow showers and 
flurries. Model soundings show steep lapse rates through 850mb with 
the dendritic growth zone occasionally dipping into the top of the 
low level moist layer. This will be more than sufficient with ample 
forcing aloft courtesy of the upper wave to generate scattered snow 
showers. 

With N/NW flow through the low levels...potential is there for a 
lake effect component to the snow showers as well with some of the 
hi-res guidance hinting at narrow bands of snow showers tracking 
across the northeast half of the forecast area in particular. Expect 
to see light accumulations but they will be isolated and wherever 
heavier snow showers fall. While some locations may see little to no 
accumulation...other spots may see a dusting up to an inch. Will 
continue to fine tune the details over the next 24 hours.

High pressure will swing across the eastern half of the country over 
the weekend with quiet weather and abundant sunshine for the Ohio 
Valley. As the surface high shifts east and return flow develops in 
tandem with ridging aloft...temperatures will warm from the 30s on 
Saturday to the 40s on Sunday. 

Low pressure will eject out of the central Rockies Sunday night... 
tracking northeast into the Great Lakes by Tuesday. Deep Gulf 
moisture will advect into the Ohio Valley ahead of the surface wave 
with widespread rain developing Monday into early Tuesday as the 
surface wave passes by to the northwest. There is potential for at 
least an isolated threat for thunder Monday afternoon and evening 
considering the dynamic nature of the system...but not enough 
confidence at this point to introduce a mention into the forecast.
 
Weak high pressure will bring a brief reprieve from the unsettled 
weather Tuesday but chances for rain will once again increase by 
late Tuesday night and Wednesday as another strong low pressure 
system tracks across the eastern Midwest. Extended model guidance 
has yet to focus in on a consensus with the track of the system but 
at this point...it again would appear that the system is most likely 
to track to the northwest of the forecast area with rain and warmer 
temperatures for central Indiana for the middle of next week. 
Looking out beyond the 7 day period...there are hints of yet another 
storm system impacting the region for next weekend.

&&

.Aviation...(12Z TAF Issuance)
Issued at 556 AM EST Thu Jan 12 2023

Impacts:

* Visibilities slowly improving through midday but generally 
  remaining 2-3SM and lower

* Widespread rain with embedded thunder this morning

* Ceilings rising to MVFR by this evening

* Light rain showers transitioning to snow showers overnight

Discussion: 

Poor flying conditions will continue through much of the forecast 
period. A large area of rain with embedded thunder is overspreading 
the region early this morning and as it does...the dense fog that 
has blanketed the area since late Wednesday is lifting with 
visibilities rising to 1-2SM. This will continue through midday but 
expect visibilities will largely remain at or below 3SM before 
improving further this afternoon. 

Rain will become more scattered this afternoon with wind direction 
shifting to N/NW at all terminals as a cold front moves away from 
the region. Winds will be gusty at times and that will persist 
through tonight as well. 

As temperatures fall through the low levels tonight...rain will mix 
with then changeover to snow. Expect scattered snow showers late 
tonight and Friday with periodic visibility restrictions. MVFR 
stratus will continue overnight into Friday.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Update...White
Short Term...Melo
Long Term...Ryan
Aviation...Ryan