123 
FXUS63 KIND 101116
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
616 AM EST Thu Mar 10 2022

...Updated Aviation Discussion...

.Short Term...(Today through Friday)
Issued at 250 AM EST Thu Mar 10 2022

Today and Tonight... 

High pressure to the SE and an advancing trough to the NW will 
position central Indiana in predominate mid to upper level SW 
flow, helping keep temperatures above normal throughout the day. 
Moisture return will be much more significant today as this SW 
flow taps into an elevated region of gulf moisture. Clouds will 
likely increase slightly within the moisture return and developing
upper level jet streak, but overall skies should remain party 
cloudy. Current forecast is for highs near 50 this afternoon. 

Winter Event (Friday and Friday Night)...

Thursday night, a deep positively tilted upper trough will approach 
from the northwest, along with a strong zonal upstream jet streak. 
To the south, the sub-tropical jet will strengthen over the Gulf 
States. This will position the Northern Mississippi and Ohio Vallies 
in strong upper level diffluence; coupled jet left exit and right 
entrance regions. In return, a surface pressure trough will develop 
leading to a quasi-stationary boundary over the region. This will be 
the initial source of lift for precipitation during the day on 
Friday. As the pressure trough continues to deepen during the day, 
surface confluence will promote a strengthening temperature gradient 
and steeper low level upglide for precip formation. Without any 
significant low level flow however, lift should be rather modest. 

As the base of the upper level trough aligns with the sub-tropical 
jet, stronger DCVA and WAA will promote surface cyclogenesis over 
MS/TN during the day Friday. As this low develops, more intense NW 
flow should both increase frontogenesis, but also progresses the 
boundary to the SE. Strongest forcings for central Indiana look to 
arrive Friday evening, as the surface cyclone nears from the SE. 
During this period, steeper isentropic ascent along with a more 
defined deformation zone should provide much stronger lift and 
heavier snow rates within snow bands. The forecast problem remains 
however, if this concentrated lift assembles prior to frontal 
passage friday evening. 

The SW flow from the days prior will promote gradual moisture 
return, so by the time vertical motion is present, there should be 
adequate moisture for precip development. This level of moisture 
will not promote higher precip rates however, and the intensifying 
surface cyclone to the south will only inhibit early moisture return 
on Friday. Low level dew points will increase on the leading edge of 
the advancing low, but that is unlikely to reach central Indiana. 
Another limiting factor within the cold sector is increasing surface 
pressure beneath strong CAA. This added subsidence will promote dry 
air intrusion and could erode the stratus layer Friday night. 

All in all, this winter event should remain low impact for central 
Indiana Friday through Friday night. Temperatures initially on friday 
will be above freezing leading to warm road surfaces and with 
limited vertical motion and moisture along the quasi-stationary 
boundary, snow rates should be low. With most of the PBL near or 
slightly above freezing, liquid to snow ratios also should be low, 
further limiting snow totals. The one factor promoting higher totals 
is the dprog/dt, with snow expected over multiple hours Friday 
afternoon into Friday evening. Higher snow totals are possible in 
far S/SE central Indiana, and therefor the range of uncertainty is 
much broader for this area. Current thoughts are for 1-2 inch for 
most of central IN, with 1-4 inches possible further SE. 

Friday Temps...

Went significantly below NBM temps as evaporative cooling along the 
advancing front along with ample cloud cover should limit 
temperature gains throughout the day. Current expectation is for 
most location to top off in the mid to low 30s, except for far SE 
central Indiana where extended dry conditions during the day will 
allow for temps to reach the low 40s.

&&

.Long Term...(Friday night through Wednesday)
Issued at 250 AM EST Thu Mar 10 2022

* Arctic blast on Saturday
* Trending much warmer for much of next week

The Arctic air will have arrived by Saturday morning across central 
Indiana, with an upper trough axis still moving through. Main 
forcing and moisture will have moved east with the main surface 
system. 

However, there will be steep low level lapse rates and some 
lingering low level moisture. Feel that there could be a few snow 
showers around thanks to these. Thus, will introduce some small PoPs 
for now across mainly the northeast third or so of the area to 
account for these as well as the possibility of some lake enhanced 
snow showers reaching the area.

Highs on Saturday will struggle and only get into the middle 20s 
most areas. Gusty northwest winds will keep wind chills in the 
single digits through the morning.

Temperatures will drop of some Saturday evening, then warm advection 
will allow some rise in temperatures overnight.

Strong warm advection will kick in on Sunday as a surface warm front 
moves through early. The front will have no significant moisture to 
work with so only expect some clouds. Some of the stronger winds 
aloft may mix down and provide gusts over 30 mph.

An upper trough will move into the area Monday night, while a closed 
upper low moves through the southern USA. Most of the forcing and 
moisture will be confined to the southern system. Nevertheless, 
can't rule out some patchy light rain as the trough moves past. Will 
go with slight chance PoPs.

Otherwise the remainder of the long term will be dry. Cold air will 
be bottled up to the north of the area, and an average of southerly 
winds will bring warm air into central Indiana. Highs will be above 
normal as early as Monday with highs in the 60s possible for 
Wednesday and Thursday.

&&

.Aviation...(12Z TAF Issuance)
Issued at 613 AM EST Thu Mar 10 2022

IMPACTS:

- VFR flying conditions expected through most of the TAF period.

- MVFR with light snow possible towards the end of the period at all 
sites but KBMG

- Winds shifting from 020-340 degrees 8 knots or less.


DISCUSSION:

VFR conditions are expected through the period as surface high 
pressure gradually builds in from the northwest and provides 
subsidence. Meanwhile mid and high clouds will be moving in 
overnight and today in southwest flow aloft. Lower clouds and light 
snow will reach KLAF by tonight, with the same features reaching 
KIND buy late tomorrow morning.  

NNE to NNW winds less than 10 knots through the TAF period.

&&

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

$$

Short Term...Updike
Long Term...50
Aviation...Updike