Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 220807

Area Forecast Discussion
National Weather Service Indianapolis IN
407 AM EDT Thu Mar 22 2018

The SYNOPSIS...NEAR TERM and SHORT TERM Sections have been updated below.


Issued at 400 AM EDT Thu Mar 22 2018

Below normal temperatures continue across central Indiana today, but a
brief respite from precipitation is in store until Friday
afternoon. At that point, a low pressure system will exit the
plains and bring in initially chances for rain in the southwest,
and then a wintry precipitation mix and some heavy snow potential
across central and northern parts of the area with rain remaining
across the south. This system will exit Saturday night. Another
system will approach Monday, but this will bring in temperatures
near to possibly above normal to get into next week.


.NEAR TERM /Today/...

Issued at 400 AM EDT Thu Mar 22 2018

Quiet weather is expected today with sunny skies under the
influence of high pressure. High temperatures will climb into the
low 40s east to the upper 40s to around 50 in the western
counties, but still remain below normal.


.SHORT TERM /Tonight through Saturday Night/...

Issued at 400 AM EDT Thu Mar 22 2018

Spring has sprung...or maybe not. Mother Nature continues to play
her cruel joke on central Indiana with another winter storm
arriving for the weekend. While tonight will be dry (only a slight
chance for any precip in the southwesternmost counties), lows
will be in the mid 20s to mid 30s. Friday will bring highs in the
mid 40s to around 50 with chances for rain arriving in the
southwest in the afternoon. By Friday night, though, the rug is
pulled out from us once again as winter returns on a low pressure
system moving out of the plains.

Strong frontogenesis along with upper forcing and some conditional
instability (showing up as negative EPV) are showing up in model
time heights in some spots at times from 6z through 18z Saturday.
This indicates the potential for some heavy snow. A low level jet
will be bring some moisture up into the area to continue to feed
the storm. There appears to be some potential in the forecast
sounding profiles for a zone of sleet/freezing rain somewhere in
the area dividing the rain area from the snow, and this will cut
into total amounts wherever it sets up. Doesn`t look like a lot in
the way of ice accumulation from this however, and right now
looking at less than a tenth of an inch in a narrow band. North of
that band, with the aforementioned strong forcing and some
instability could see a snow band with amounts approaching 6 to 8
inches. The cutoff between snow and rain looks to be very sharp
north to south with this system, and could see counties with
nothing on one end and several inches on the other. With models
coming into better agreement with this system and the potential
for heavy snow, have decided to issue winter storm watch at this
time for areas approximately along and north of Interstate 74. Any
change in the track of this potent little system will change the
location of heaviest amounts, and a greater intrusion of warm air
would cut total snowfall but possibly bring more icing potential,
so these will be things to watch in upcoming forecasts.

Potential for snow and mixed precipitation will continue through
the day on Saturday and even into Saturday night. Think the worst
should be over by 0z Sunday if not before, so let the watch end
then. Across southwestern Indiana Saturday, enough instability is
moving in to add a slight chance for thunderstorms to the forecast
to go along with the rain there, and this is another indication of
the strength of this system.

The system should move out of the area late Saturday night and
allow dry conditions to return.


.LONG TERM /Sunday through Wednesday/...
Issued at 323 PM EDT Thu Mar 22 2018

Will focus on PoPs and temperature trends for the long term.

Models agree that upper waves will lift northeast across the Ohio
Valley in southwest flow ahead of a southwestern upper low and
trough. High confidence, these features combined with a northern
stream trough and a moist flow off of the Gulf of Mexico, ahead of a
surface system, will result in widespread showers by Tuesday. Prior
to that, highly confident high pressure will provide dry weather
Sunday and Sunday night.

High confidence the southerly low level flow will also result in
moderating temperatures back to normal and beyond. Blend highs in
the 50s and lower 60s by next Tuesday per the blend look reasonable.


.AVIATION /Discussion for the 22/06Z TAFs/...
Issued at 1138 PM EDT Wed Mar 21 2018

VFR through the period.

Surface high pressure will be in control through the period.
Expect only a few mid and high clouds and no obstructions to
visibility. Winds will generally be northwesterly with speeds 10KT
or less.


Winter Storm Watch from late Friday night through Saturday
evening for INZ021-028>031-035>042-046>049-056-057-065.



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