Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 231013
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
613 AM EDT Sat Mar 23 2024

.KEY MESSAGES...

- Mostly Cloudy this morning; Becoming partly cloudy this afternoon;
Cool.
- Partly Cloudy tonight with a freeze.
- A gusty to windy Monday will bring one other day in the 60s
- Moderate to heavy rainfall expected Monday Night-Tuesday Night

&&

.SHORT TERM (Today and tonight)...
Issued at 258 AM EDT Sat Mar 23 2024

Synopsis:

Surface analysis early this morning showed strong high pressure in
place over the northern plains, building eastward. Low pressure was
found over the southeastern states. This was resulting in a cool
northerly flow to Central Indiana. GOES16 this morning shows stratus
in the wake of a cold front stretching from lower MI across NW
Indiana to IL and MO. Radar shows a thin area of showers along this
front quickly pushing east and diminishing in intensity and
coverage.  Aloft, water vapor imagery showed ridging in place over
the Rockies, and a broad, shallow trough stretching from the
northern plains, across the Great Lakes to Maine.

Today...

Models show cold air advection in place today as northerly surface
flow will continue through the course of the day. The stratus deck
as seen on GOES is expected to sag across Central Indiana as the day
begins in the wake of the passed cold front and due to the ongoing
cold air advection. Forecast soundings this morning show a saturated
lower level indicative of this deck, but as heating and subsidence
builds across the area today, this deck washes out by late morning.
Due to an inversion aloft, convective temperatures will not be
reached and skies will gradually become just partly cloudy this
afternoon.  Synoptically, the main weather feature for Indiana will
be the strong Canadian high pressure system over the northern
plains, drifting east through the Great Lakes  and continuing to
provide the cool and dry northerly flow.

850Mb temps are expected to fall to -8C, leading to highs only
reaching the mid 40s.

Tonight...

The quick moving ridge aloft is expected to drift east of
Indiana overnight, and the ongoing cold air advection is expected to
switch to warm air advection overnight as the ridge axis passes
east.  Models suggest the mid level flow becoming southwesterly, and
amid this warm air advection some mid and high cloud coverage is
expected to develop over IL and WI before drifting into Indiana
overnight. Time heights and forecast sounding show the arrival of
mid level saturation. Thus skies will become partly cloudy
overnight.

The expected warm air advection will not arrive in time to prevent
temperatures from falling below freezing. The dry air mass in place
across Indiana, with dew points in the 20s will allow for a quick
cool down this evening, as much of the night is spent with
temperatures in the lower 30s to upper 20s. Thus with freezing
temperatures once again expected, an SPS will be issued to address
any agricultural concerns.

&&

.LONG TERM (Sunday through Friday)...
Issued at 258 AM EDT Sat Mar 23 2024

Sunday through Tuesday...

Broad, slowly-progressing upper troughiness over much of central and
western North America early next week...will lift while passing the
Midwest through the midweek, bringing first widespread rain and then
a couple chances for frosty overnights.

Sunday will be a day of transition as surface high pressure departs
the eastern Great Lakes and a High Plains cyclone plummets 12 mb in
12 hours before starting to eject eastward into Kansas.  Central
Indiana will be caught amid the corresponding developing gradient
and under a building H500 zonal ridge.  Easterly flow will veer
slightly and gust up to 20 mph offering modest warm advection back
to seasonable levels.  Weak disorganized forcing coupled with the
eastern extents of the deepening systems warm frontal zone will
promote variable cloudiness, especially across western zones.

Monday will feature gusty to perhaps windy conditions as the
arriving gradient brings south-southeasterly gusts to at least 35-40
mph.  This WAA will overcome mostly cloudy skies thickening from
west to east to boost temperatures into the mid-60s over most
locations.  Confidence is increasing in Monday staying mainly dry
with latest guidance suggesting any first rounds of organized
precipitation crossing Illinois will likely be absorbed by very dry
lower levels before reaching Indiana.

Monday night should be the main focus for rainfall, especially any
heavier banding that may cross the region...as a solid ribbon of
Gulf moisture, flowing northward through eastern sectors of the
upper troughs broad flow, is expected to shift eastward across the
CWA.  Latest trends in precipitable water are up, with 1.10-1.20
inch values possible, at least briefly, over all zones... however
upper vorts may simultaneously phase which would push this deep
moisture and opportunity for steadier rain through the region
faster, possibly lowering rainfall expectation to more moderate
amounts.  The complex to perhaps disorganized nature of the phasing
vorts so far lowers confidence in the location of the regions
greatest rainfall.  The tandem of stronger convection likely
developing near Mississippi...and the lack thereof over central
Indiana per warmed mid-levels should combine to dampen potential for
widespread heavy rainfall.  Will keep an eye on any chances for
thunder over local realms, but appears no instability will be
available to realize the potential of the strongly sheared profile.

Less confidence in expanse and amount of rain for the Tuesday to
Tuesday night timeframe across guidance members.  The broad and
northward-advancing cyclone will drag its frontal boundary east
through the CWA, although location, timing and therefore involvement
of the southern-most piece of upper energy is uncertain.  Likely at
least additional widespread light rainfall, although another 0.50+
inches would certainly be possible should the vort cross Indiana
instead of passing to our south/east.

A marginal fire danger will exist through the afternoons of Sunday
and probably also Monday...led by lower relative humidity values
amid more moderated gusts Sunday...and led by windy conditions amid
the arrival of slightly higher relative humidity on Monday.

Wednesday through Friday...

Dry and generally seasonable conditions will prevail through the
remainder of the work week as the weakening and now more
distinctively split broad upper trough slides through Indiana...
with correspondingly broad, yet low-gradient surface high pressure
expanding from the Midwest to the Lower Mississippi Valley.  So far
no expectations for any precipitation amid northwest flow around the
Wednesday timeframe, with supporting energy lifting northward while
the once potent surface low fills towards Hudson Bay.  Moderation
should be the rule to end the week as a seasonably strong upper
ridge crosses the central CONUS.  Can not rule out a stray shower
amid warm frontal cloudiness during this transition, yet low
confidence in any organized precipitation with broad surface ridge
still to our south blocking most Gulf moisture.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 611 AM EDT Sat Mar 23 2024

Impacts:

- MVFR Cigs exiting this morning
- VFR conditions return by early afternoon, after 17Z.

Discussion:

GOES16 imagery shows some breaks within the stratus shield descending
upon the TAF sites. The back edge of MVFR Cigs appears to be pushing
south of LAF, with a mix of MVFR and VFR Cigs found upstream over
far northern Indiana and southern MI. Given the northerly flow and
the return of heating, this mixture of MVFR and VFR cigs is expected
to push across the TAF sites during the first few hours of the TAF
period.

Otherwise, little overall change to the ongoing forecast.
Improvement to VFR is expected by late this morning and early this
afternoon as a ridge axis builds across the region. Diurnal heating
combined with the arrival of a mid level ridge axis through the
afternoon should allow for the deterioration of cloud cover this
afternoon, leading to VFR conditions. Again, forecast soundings are
on board with this, showing a dry column by mid afternoon.

VFR conditions will then persist through the evening and overnight
hours as ridging builds across the region.

&&

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

$$

SHORT TERM...Puma
LONG TERM...AGM
AVIATION...Puma


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