Area Forecast Discussion
Issued by NWS Indianapolis, IN

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236
FXUS63 KIND 220716
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
315 AM EDT Sun Apr 22 2018

.UPDATE...
The LONG TERM section has been updated below.

&&

.SYNOPSIS...
Issued at 350 PM EDT Sat Apr 21 2018

High pressure will keep quiet weather across the area into early
Sunday. A closed low pressure system will drift slowly eastward
and northward out of the central Plains and lower Mississippi
Valley tomorrow into mid week, providing opportunities for showers
at times from late tomorrow into Wednesday. A quick moving upper
trough and cold front late in the week will bring additional
shower chances to the area as well.

&&

.NEAR TERM /Tonight/...
Issued at 903 PM EDT Sat Apr 21 2018

Current forecast in good shape. No updates planned at this time.
Previous discussion follows.

Expect quiet weather through tonight as high pressure over the
central Great Lakes slowly drifts eastward. Mid and high cloud has
overspread much of the area this afternoon and this will only
continue through the night.

Dropped min temps from the blend slightly as, while increasing
cloud cover will keep temps from bottoming out, dewpoints will
remain quite low overnight although they will be slowly rising.
Should easily see the low to mid 40s most areas, and perhaps the
upper 30s north.

&&

.SHORT TERM /Sunday through Tuesday/...
Issued at 350 PM EDT Sat Apr 21 2018

Vertically stacked low pressure system will be in the lower
Mississippi Valley by midday Sunday and showers may nudge into the
far southwestern portions of the area Sunday afternoon. Chances
for showers will slowly overspread the area Sunday night into
Monday, with chances remaining through the short term period as
the low drifts northward through the Tennessee Valley into the
Ohio Valley through mid week before finally beginning to be
reabsorbed into the prevailing westerlies.

Profiles through the period are relatively moist throughout the
depth of the troposphere but lapse rates are mostly near moist
adiabatic and little to no upright instability is present, so will
include no thunder mentions. SREF calibrated thunder probabilities
support this.

With minor tweaks, consensus temperatures were generally in the
ballpark. Bumped highs up slightly Sunday as we have warmed well
even under the cloud cover this afternoon, and most areas will
remain dry tomorrow. This is well supported by upstream
temperatures as well.

&&

.LONG TERM /Wednesday through Saturday/...
Issued at 315 AM EDT Sun Apr 22 2018

The main focus for the long term will be on timing of showers over
the area as a pair of waves move through the area in a mean eastern
trough regime.

Issues with model timing of various upper waves or lows over the
Great Lakes and Ohio in mean eastern trough lend low confidence in
model QPF timing and consequently in timing and coverage of PoPs
throughout the long term.

Models were showing a Great Lakes trough dropping southeast over the
area Wednesday. The 12z ECMWF and 00z CMC were faster than the 00z
GFS with this feature and would support low or no PoPs. The 00z GFS
would support higher PoPs. The new  ECMWF just came in closer to the
GFS, but still faster. With confidence low in a winner, low blend
PoPs will be accepted.

Then, a surface and upper ridge should allow for dry weather
Wednesday night and at least Thursday morning. After that, the 00z
GFS was much faster and further north with an upper system compared
to the slower 12z ECMWF and the slower and much further southern 00z
CMC. The 00z GFS brings QPF back across northwestern parts of the
forecast area Thursday afternoon, while the other models do not
bring any in until Thursday night /CMC/ or Friday /ECMWF/. The Blend
was closer to the GFS, with low PoPs northwest Thursday afternoon
and chance PoPs all areas by Thursday night. With it being the long
term and confidence not high in any one model, will accept the
Blend. Kept chance PoPs in through Friday night per the Blend. Then,
dry weather is expected the remainder of next weekend as an upper
ridge approaches.

With mean upper troughing, high confidence in below to slightly
below normal temperatures per the Blend.

&&

.AVIATION /Discussion for the 220600Z TAFS/...
Issued at 1136 PM EDT Sat Apr 21 2018

Ceilings above 050 and unrestricted visibility expected at the
terminals through midday Sunday. Surface winds 070-100 degrees at
5-9 kts overnight will increase to 9-13 kts by midday Sunday.

&&

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

$$

SYNOPSIS...Nield
NEAR TERM...Nield/JAS
SHORT TERM...Nield
LONG TERM...MK
AVIATION...JAS



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