Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 211927

Area Forecast Discussion
National Weather Service Indianapolis IN
227 PM EST Thu Nov 21 2019

The LONG TERM Section has been updated below.


Issued at 415 AM EST Thu Nov 21 2019

A cold front will move into west central Indiana late this
afternoon and move across the state tonight. Rain showers will
spread across much of the area today but should remain light and
diminish later today. Showers are expected tonight along the front
over south central Indiana. Dry weather moves in on Friday but
another system will approach for Saturday with rain and snow
likely. Yet another strong storm system is expected to impact the
Midwest prior to Thanksgiving. This storm could impact travel
across the country so continue to monitor weather forecasts for
next week if you have travel plans.


.NEAR TERM /This afternoon/...

Issued at 1045 AM EST Thu Nov 21 2019

Radar shows an area of rain showers over the Wabash pushing east
across the forecast area quickly this morning. This is associated
with a a short wave and low pressure system over Wisconsin quickly
moving northeast through the region. Surface analysis reveals a
strong pressure gradient across the area...and strong southerly
flow was in place across the forecast area. A cold front was
found across western Illinois...Central Missouri and Oklahoma.
GOES16 shows extensive cloud cover across the region.

The upper wave and associated rain will quickly sweep across
Central Indiana through early to mid us a few
hours within the dry sector late this afternoon. Thus have trended
toward 100 pops for the next few hours as the wave of precip
passes. Given the expected cloud cover and limited
heating...trended highs slightly cooler than the previous
forecast...particularly with the rain cooled air in place this
morning and early this afternoon.


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

Issued at 414 AM EST Thu Nov 21 2019

An active and more winter like pattern later in the short term
period. Cold front to push through southeast areas this evening. A
secondary weak wave and moisture surge may reinvigorate showers
along boundary this evening in the south to increased pops once
again. Drier air and Canadian high slide in for Friday. Stayed
optimistic with cloud cover and clearing given very dry air per
soundings. However, expect a rather strong subsidence inversion on
Friday and some potential for trapped stratus once again. Will
rely on strong subsidence and strength of high and lean toward the
clearing skies.

Dry weather will be short lived as upper low over southwest CONUS
today ejects northeast and approaches for Saturday. Uncertainty
remains high in details as models have a lot of differences with
timing and thermal fields. Pcpn type will be an issue with this
system as cold air deepens during the day and strong dynamics lead
to a changeover to snow. Some freezing pcpn remains possible at
onset but this depends on how fast moisture spreads north late
Friday night. Surface temps expected to fall into upper 20s with
slow eroding near surface cold wedge trapped by high pressure to the
north. GFS much faster bringing pcpn into central Indiana while NAM
much slower. Warm nose aloft spreading over cold sfc wedge would
likely result in some light freezing rain central and north for a
few hours Saturday morning with faster solutions. Not ready to buy
into this quite yet as models, especially GFS, tend to be too fast
with eastward ejection of closed upper lows. Will lean toward slower
arrival and frozen pcpn for now. A period of rain or rain snow
possible Saturday morning before cooling aloft and forcing lead to
changeover to a wet snow. Ratios will be rather low so this should
limit any accums to under an inch and primarily grassy surfaces as
it looks now. Expect details to change next few model iterations as
better agreement develops.


.LONG TERM /Monday Night through Thursday/...

Issued at 227 PM EST Thu Nov 21 2019

Mainly dry weather bookends this period with a strong chance for
rain mid week.

THE ECMWF suggests quick flow in place aloft on Monday and night
through Tuesday with little in the way of forcing dynamics aloft.
Meanwhile at the surface southerly surface flow remains in place
ahead of an approaching trough over the plains.

On Tuesday night through Wednesday a strong upper trough and
associated surface flow are expected to arrive and push across
Central Indiana. Plenty of moisture remains available.
Temperatures looks to remain warm enough for the bulk of
precipitation to remain as rain...however as cold air arrives in
the wake of the cold front on Wednesday with wrap-around type
precipitation. Thus will trend toward higher pops on Tuesday
through Wednesday Night.

Strong ridging looks to build across the area for
Thanksgiving...which should give us a return to dry and pleasant
weather with seasonal temps.


.AVIATION /Discussion for the 211800Z Taf/...

Issued at 114 PM EST Thu Nov 21 2019

MVFR conditions are expected to deteriorate to IFR to LIFR
conditions during this Taf period.

Short wave currently exiting Central Indiana as seen of radar as
the back edge of precipitation exits the area. Strong cyclonic
flow remains in place across Indiana associated with a strong area
of low pressure in place over Wisconsin...and an approaching cold
front over Central Illinois. GOES16 shows extensive cloud cover
including many areas of MVFR to IFR conditions poised to arrive
across Central Indiana late this afternoon and into the evening.

Models continue to indicate plenty of lower level moisture
available through at least 12Z Friday. Thus will trend to keeping
the IFR conditions in play for much of the night.

Some improvement toward VFR will arrive by late morning on Friday
as high pressure arrives from the Plains states.




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