Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 241642
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1242 PM EDT Sun Mar 24 2024

.KEY MESSAGES...

- Partly Sunny Today and Warmer
- Elevated Fire Danger this Afternoon
- Partly Cloudy Tonight
- Gusty to windy conditions Monday-Tuesday
- Moderate rainfall, few non-severe storms Monday Night-Tuesday

&&

.FORECAST UPDATE...
Issued at 1242 PM EDT Sun Mar 24 2024

Temperatures are on their way to approaching normal late March highs
in the 50s. As is often the case, mixing has brought down lower dew
points and higher wind gusts than a model blend solution. Thus,
updated the grids to the lower HRRR dew points and also bumped up
winds and gusts a few knots for the afternoon as plenty of solar
radiation has resulted in good mixing below a 3K foot inversion. The
combo of the gusty winds, low RH potential around peak heating and
marginal fuel moisture supports elevated fire danger which is
mentioned in the Hazardous Weather Outlook.

&&

.SHORT TERM (Today and tonight)...
Issued at 301 AM EDT Sun Mar 24 2024

Synopsis:

Surface analysis early this morning showed strong high pressure in
place over Ontario, with an inverted ridge axis sagging south across
western OH to Central KY and western TN. This feature was providing
dry and cool easterly flow to Central Indiana. Aloft an upper trough
was found over the western United States, which was spilling out
into mainly zonal flow across the plains to the Ohio valley. A weak
disturbance within this flow was found over the western plains,
generating some high clouds that were streaming toward Central
Indiana.  GOES16 shows mid and high cloud upstream of Central
Indiana, over IL, MO and IA. Dew point temps remained very dry
across Central Indiana amid the easterly flow, in the teens and
lower 20s.

Today...

Models today show the upper trough over the west coast pushing east
toward the Central Plains. This result in southwesterly flow
gradually developing aloft across Central Indiana.  This will begin
to set the stage for rainfall on Monday Night, but it will take a
bit of time to get to rainfall. Dry air and subsidence is shown to
persist through the day across Central Indiana today within the
lower levels. Overall the strong high to the north will still remain
in control of our weather. Dew points through the day remain very
dry within the lower 20s. Forecast soundings show dry lower and mid
levels with unreachable convective temperatures. Thus only some high
passing clouds will be expected within the flow aloft. Hence, partly
cloudy.

Moderate warm air advection is in play today as southerly flow
develops. 850MB temps rise toward 8C by the end of the day. Thus
highs around 50 to the lower 50s will be expected.

Tonight...

Little overall change is expected. The lower levels are
suggested to remain dry amid continued southerly flow. Forecast
soundings continue to suggest high clouds passing aloft amid the
southwest flow ahead of the approaching upper trough. This will
continue to just result in partly to mostly cloudy skies due to high
passing clouds. Of note, a moderate LLJ near 40-50 knts ahead of the
approaching trough is expected to nudge eastward toward Indiana.
This will result in a stronger lower level gradient building across
Central Indiana overnight. Thus winds around 10-20 mph will be
possible. Given the high clouds, good mixing expected and ongoing
warm air advection, lows in the lower to middle 40s will be expected
for a warmer night than the past few nights.

&&

.LONG TERM (Monday through Saturday)...
Issued at 301 AM EDT Sun Mar 24 2024

Monday through Tuesday night...

The workweek will start with a broad and deep upper trough`s expanse
over all of the western and central CONUS...and a potent, yet slowly
filling 988 mb surface low drifting over the central Plains.  Monday
will be a gusty to windy day amid the gradient between this feature
and amplified surface high pressure along the eastern seaboard.
Widespread southerly gusts to 25-35 mph appear likely for midday to
afternoon hours Monday...with strongest gusts along the Illinois
border. This impressive flow will fetch a solid early spring ribbon
of deep moisture off of the western Gulf and extend it up the
Mississippi Valley Monday. Early stagnation of the surface low and
dry antecedent lower levels should delay the arrival of any
corresponding organized rain until Monday evening.

Guidance is continuing to show Monday night as the main slug of
steady to perhaps briefly heavy rain across the region as the moist
conveyor of precipitable water values in the 1.10-1.25 inch range
cross Indiana, with a residence time over any single location for
about 3-6 hours.  Energy aloft, arriving from the SSW should promote
embedded moderate to heavy rainfall rates...although confidence is
increasing in nocturnal convection near Mississippi absorbing much
of the moist flow off of the Gulf...with perhaps only widespread
moderate rainfall leaning towards 0.50 inch values most likely for
the majority of the local region.  Can not rule out isolated thunder
amid the highly-sheared profile, especially south of I-70 where what
little near-zero instability may be briefly reached from an elevated
source, although certainly no strong/severe storms are expected.
Widespread SSE/S gusts around 40 mph are expected as the strong
gradient crosses the region, as the surface low lifts towards the
Twin Cities.

Additional light rain and a few thunderstorms should be the rule for
Tuesday as the main slug of moisture slides east before the system`s
cold front approaches and slowly crosses the CWA.  Latest guidance
is indicating a subtle split in upper forcing should promote the
H700 RH dry conveyor pushing across Indiana Tuesday...so do not
expect any appreciable rains, with final showers tapering off by
late day/early evening over eastern zones.  Gusty conditions ahead
of the boundary should diminish to more reasonable CAA breezes into
Tuesday night.  Temperatures should drop at least 30 degrees from
60s Tuesday to low 30s Tuesday night.

Wednesday through Saturday...

The once broad upper trough should quietly morph into more of a
placid yet cooler early spring zonal flow...with the pattern`s
energy splitting between northern wave twisting into the Great
Lakes/ Ontario...and another broad southern vort plowing east along
the Gulf coast.  Surface high pressure occupying a decent swath of
the CONUS will slowly advance from central to eastern states...which
will encourage moderation from below to at least slightly above
normal.

The next upstream surface low, expected to be positioned over the
central Plains by around early Friday, and with a more modest
intensity.  Therefore late-week highs in the 60s appear more likely
than the record-type warmth seen earlier this month. Proximity of
the low to our west should favor some cloudiness with associated
warm-frontal zone extended eastward to near Indiana.  Next shot at
rain would likely be brief chances near the start of the weekend as
the small low ejects ESE-ward around the flow of the remnant upper
trough still over southeastern Canada.  So far decent model
agreement suggests any organized rainfall would be more likely over
northern and eastern portions of the Midwest. The normal max/min at
Indianapolis through the long term is 57/37.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 1141 AM EDT Sun Mar 24 2024

Impacts:

- Non-convective low level wind shear around 2K feet 04z-14z
  Monday

- Winds 120-160 degrees with gusts to 20 knots through 14z
  Monday

- Winds 150-180 degrees to near 20 knots and gusts to around
  30 knots after 14z Monday

Discussion:

Eastern Great Lakes low pressure and a dry lower and middle column
per Hi-Res soundings lend high confidence to VFR flying conditions
tonight and Monday morning. Should only see some cirrus increasing
in southwest flow aloft. Mid and high end lower clouds are possible
Monday afternoon as low pressure moves into the Ozarks.

Breezy SSE winds will continue through the TAF period.


&&

.FIRE WEATHER...
Mixing will likely bring dew points as low as the middle and upper
teens this afternoon. This would result in brief late afternoon RH
values near 25 percent. In addition, late day fuel moistures fell to
7% late yesterday afternoon. The combo of the gusty winds, low RH
and marginal fuel moisture will pose a brief window of elevated fire
danger late this afternoon. Will add this to the Hazardous Weather
Outlook.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...MK
SHORT TERM...Puma
LONG TERM...AGM
AVIATION...MK
FIRE WEATHER...MK


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