Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 140244
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
944 PM EST Tue Feb 13 2018

.UPDATE...
The NEAR TERM and AVIATION sections have been updated below.

&&

.SYNOPSIS...
Issued at 400 PM EST Tue Feb 13 2018

High pressure will continue to depart to the east tonight as
developing southerly flow begins to bring more moisture into the
area. A frontal zone will begin to develop late Wednesday into
Wednesday night as the temperature gradient tightens over the
region. Rain will be in the forecast from late tonight into Friday
morning, with the highest chances Thursday into Thursday night as
this frontal zone pushes slowly southward through the area. The
frontal zone will return northward early next week with multiple
disturbances developing along it, which will bring several chances
for rainfall and perhaps the threat of significant rainfall and
flooding.

&&

.NEAR TERM /Rest of Tonight/...
Issued at 944 PM EST Tue Feb 13 2018

Forecast is in good shape, so only tweaked hourly forecasts as
needed. Sprinkles have moved out of the area, and rain doesn`t look
to move into the far southwest until late tonight.

Temperatures look good as well with variable cloudiness expected
most areas tonight.

Previous discussion follows...

Models suggest that most of the area will remain dry throughout the
night. Across the far southern portion of the area, isentropic lift
develops late and forecast soundings show good low and midlevel
saturation, suggesting some drizzle or rain will make it into those
areas after about 09Z.

Consensus temperatures appeared reasonable per upstream numbers
and required only minor tweaks.

&&

.SHORT TERM /Wednesday through Friday/...
Issued at 400 PM EST Tue Feb 13 2018

Precipitation chances will be in the forecast throughout the short
term, save for late Friday as high pressure pushes into the area
in the wake of the departing frontal zone and forecast profiles
become quite dry.

Chances tomorrow will be highest across the south and southeast
with the best isentropic lift. Lower chances will be necessary
Wednesday night into early Thursday as the frontal zone begins to
develop to our northwest. Will carry high chances Thursday
afternoon into early Friday as the front sags through the area and
multiple upper level waves move through the broader southwest flow
aloft.

Thermal profiles suggest precip may briefly change over to a mix
or all snow late Thursday night into Friday morning as the front
departs, but this is unlikely to be of significant impact.

Consensus temperatures were generally acceptable, and required
only minor adjustment. Highs will likely be reached early in the
day on Friday as the front pushes south of the area, with steady
or falling temperatures throughout the day.

&&

.LONG TERM /Friday Night through Tuesday/...
Issued at 229 PM EST Tue Feb 13 2018

After a break for much of the weekend...the moist southwest flow
aloft regime will resume...with growing confidence in an extended
potential for heavy rain with heightened flooding concerns
developing next week.

The cold front impacting central Indiana Thursday and Thursday
night will be well south of the region over the Tennessee Valley
by Friday night as strong high pressure builds into the eastern
Midwest. RH progs are exceptionally dry through Saturday with
mostly clear skies expected. The high will quickly move east of
the region by late day Saturday with return flow enabling
modification of the ambient airmass. A quick moving system passing
through the Great Lakes on Sunday may produce a small threat for
rain...but more expansive moisture return will be difficult with
the Gulf of Mexico cutoff.

That will change rather dramatically for the latter part of the
extended as an amplifying upper trough develops over the Rockies
by the end of the weekend. This will promote downstream ridging
over the eastern U S and a resumption of moist southwest flow
aloft. As Gulf moisture is drawn north ahead of an approaching
frontal boundary...the stage will be set potentially for an
extended period with rain...and heavy rain at that...impacting the
Ohio Valley as the front becomes quasi-stationary and surface
waves track along the boundary. With good model agreement on a
blocking upper ridge centered off the southeast coast...the
frontal boundary may not be able to shift away from the region
until late next week. Of particular concern is the depth and
intensity of the moisture plume with precip water values running
up to around 1.5 inches from Monday night on. For mid-late
February...these values would be in excess of 300% of normal
value.

Could see snowflakes briefly mix in with the rain Monday night
over the northern Wabash Valley...but not expecting any winter-
related impacts in this potential setup.

Plenty of time to monitor this threat...but there are already
several classic signals towards a more widespread flooding concern
somewhere across the Ohio and Tennessee Valleys present...
1) southwest flow aloft
2) phased upper jet with a strong subtropical component
3) blocking ridge off the southeast coast
4) deep and climatologically anomalous moisture fetch

Near normal temps on Saturday will rise into above normal levels
for the remainder of the period. Could see 50s to low 60s in parts
of the area Monday and Tuesday.

&&


.AVIATION (Discussion for the 140300Z TAF Update)...
Issued at 944 PM EST Tue Feb 13 2018

Based on latest data have pushed back the start time of MVFR at KIND
by a bit. Also upped wind speed based on latest obs.

Previous discussion follows...

Conditions are expected to deteriorate to IFR for the second half of
the TAF period. Southern sites may see some rain late tonight into
Wednesday.

Area of MVFR clouds across southwest Indiana does not appear to be
growing or moving northeast, so delayed MVFR arrival at KIND until
after 06Z.

Otherwise expect conditions to slowly deteriorate overnight,
reaching IFR at southeastern sites by 12-13Z or so and northwestern
sites by 18Z. The steadier rain will remain at KBMG and south late
tonight, but will include VCSH mention at KIND & KBMG.

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SYNOPSIS...Nield
NEAR TERM...Nield/50
SHORT TERM...Nield
LONG TERM...Ryan
AVIATION...50



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