Area Forecast Discussion
Issued by NWS Indianapolis, IN

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KIND 232313

Area Forecast Discussion
National Weather Service Indianapolis IN
713 PM EDT Fri Mar 23 2018

The AVIATION section has been updated below.


Issued at 407 PM EDT Fri Mar 23 2018

An area of low pressure will bring accumulating snow to central
Indiana Saturday with rain elsewhere. Another frontal system will
bring rain chances to the area for much of next week. Well below
normal temperatures Saturday will give way to near normal readings
early next week.


.NEAR TERM.../Rest of This Afternoon, Tonight, and Saturday/
Issued at 407 PM EDT Fri Mar 23 2018

The remainder of the afternoon will be quiet with just increasing
mid and high clouds across the area.

Precipitation will develop across the far southwest forecast area
this evening then overspread the remainder of the southwest half of
the forecast area tonight. Precipitation will then overspread the
remainder of the area during the day Saturday.

A good low level flow will bring in moisture, while an upper wave,
surface low, and upper jet bring forcing. Frontogenetical forcing
and deformation will bring the possibility of banded heavier
precipitation. Thus by Saturday will have categorical PoPs most
areas, with likely PoPs far north.

That`s the bigger picture, but the devil is of course in the
details. NAM, SREF, HREF mean all keep an axis of heavier snow
across the northern forecast area. However, GFS, ECMWF, and Canadian
continue their southern trend. This leads to higher uncertainty
forecast than would be liked at this stage.

Thermal profiles remain marginal with large isothermal areas around
32 degrees. This means that even a small change in temperatures
could bring big changes to precipitation type and snow amounts. Why
not add more uncertainty by adding an initially very dry lower
atmosphere and a persistent drier easterly flow at the surface as
well as the aforementioned banding potential which would also
influence precipitation type?

Given the relatively large uncertainties involved, decided to
continue with gradual trends rather than latching onto any one
solution. Thus allowed axis of heavier snow to sink a little farther
south and continued lowering the snow amounts a bit.  This puts the
axis of heavier snow to near/south of I-74 and higher amounts
generally in the 3 to 5 inch range.

Ground temperatures will remain relatively warm thanks to today`s
sun. Air temperatures will not be that cold with lows only in the
upper 20s northeast to around freezing near I-74. Highs on Saturday
will be in the mid 30s. Thus (main) roads may not be that bad for
the most part (unless under a heavy band), and snow will compact

Given all the above decided with a Winter Weather Advisory for the
heavier snow area. While the far northeast may still get snow, it
now appears that amounts will be low enough to have no advisory.

With the uncertainty and the low changes needed in the atmosphere to
make a big impact, changes to the forecast at any one location are
likely as trends become clearer.


.SHORT TERM.../Saturday night through Monday/
Issued at 407 PM EDT Fri Mar 23 2018

Models are close enough that the model blend initialization
was accepted for most items.

Precipitation will end Saturday night with little additional
accumulation as the system exits. Sunday and Sunday night will be
dry with high pressure in control.

Rain chances will return Monday afternoon as another upper trough
approaches the area. With the rain will come temperatures closer to
average, with highs mainly in the 50s.


.LONG TERM /Monday Night Through Friday/...
Issued at 247 PM EDT Fri Mar 23 2018

Ensembles indicate a slowly progressive nature to the long wave
features during this period. Mean upper trough initially over the
Rockies will gradually shift into the Midwest by the later parts of
next week.

Unsettled weather is expected for most of the long range period, as
occasional disturbances eject out of approaching mean trough. Will
continue to broadbrush PoPs from Monday night through Thursday
night. It appears by next Friday the main moisture plume will get
shunted off to the southeast, so will go dry by then. Progged
precipitable water into the midweek period continue to look very
high for this time of year, so heavy rain may become an issue.


.AVIATION (Discussion for the 240000Z TAF Issuance)...
Issued at 713 PM EDT Fri Mar 23 2018

Conditions expected to deteriorate to IFR most sites by 14Z in snow
and rain. Wind gusts near 30kt are likely during the daytime

Mid and high clouds will thicken and lower this evening.
Precipitation will begin around 06Z west and spread slowly north and
east through 12Z or so, with widespread precipitation continuing on
Saturday. IFR conditions will develop by 14Z as lower atmosphere
saturates and precipitation continues.

Precipitation should be mainly snow with rain mixing in at the
northern sites and a general mix of rain and snow at the southern
sites. Cannot rule out brief period of sleet but odds are too low to

Winds will become gusty on Saturday with 30kt gusts possible.


Winter Weather Advisory from 5 AM to 8 PM EDT Saturday for



AVIATION...50 is the U.S. government's official web portal to all federal, state and local government web resources and services.