Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 090422
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1122 PM EST Mon Mar 8 2021

...Updated Aviation Discussion...

.Forecast Update...
Issued at 944 PM EST Mon Mar 8 2021

Latest satellite imagery shows plenty of cirrus clouds upstream of
the area and across central Indiana as well. Thus have upped sky
cover through the night, but still in the partly cloudy category.

Temperatures continue to vary from the mid 40s to the upper 50s this
evening, with the variation in part from the clouds and the dry
lower levels. Adjusted hourly temperatures to account for these
ranges, but the low temperature forecast still looks on target given
these trends and the expected cloud cover.

&&

.Short Term...(This evening through Tuesday night)
Issued at 318 PM EST Mon Mar 8 2021

Spectacular afternoon in progress across central Indiana as strong
southwest flow has advected much warmer air into the region. The
warmest afternoon of the year so far is currently ongoing...with mid
and upper 60s widespread across the forecast area at 1930Z.

The dry weather enjoyed over the last several days will continue
through Tuesday night but now with the added benefit of the warmest
air of the year so far as well. Ridging aloft and at the surface
with high pressure situated over the southeast states will continue
to transport warm...dry air into the Ohio Valley with a persistent
southwesterly flow. Strong subsidence noted in RH progs and model
soundings support little cloud cover through Tuesday with cirrus
impinging on the area periodically. As moisture slowly advects into
the region late Tuesday into Tuesday night...will see an increase in
mid and high level clouds.

Primary issue through Tuesday will be the gusty winds consequently
elevating the fire danger across the region...focused particularly
for the rest of this afternoon and again on Tuesday afternoon.
Southwest winds will gust in excess of 25 mph both afternoons and
combined with lower dewpoints and RH values...will enhance fire
weather concerns. More on this in the fire weather section below.

Temps...considering the setup is similar Tuesday...have gone 3-4
degrees above guidance in most areas. Expect highs on par with temps
this afternoon. Once again...a few spots will luck out and hit the
initial 70 degree reading of 2021. With the dry airmass present...
temperatures will drop efficiently at night and held close to a
model blend. Expect upper 30s and lower 40s tonight and mid 40s to
near 50 Tuesday night.

.Long Term...(Wednesday through Monday)
Issued at 318 PM EST Mon Mar 8 2021

Long term period looks to be a bit of an early transition season
roller coaster with warm conditions dropping back towards more
normal temperatures as the period progresses, and plenty of chances
for rain, particularly late in the work week as a frontal zone moves
into the region and one or more low pressure systems develop and
travel along it. Guidance is in agreement on broad generalities,
particularly early on, but disagreement on details amplifies
significantly as the period wears on.

Broad south/southwest flow at the surface and aloft looks to
establish itself by mid week as high pressure shuffles eastward and
a large longwave trough enters the western CONUS. Despite the
potential for a not quite fully open Gulf, continued poleward flow
of warm and increasingly moist air will shift into the area as a
baroclinic zone develops and intensifies in response to this upper
level trough and a 130-150+KT strengthening upper level jet.

Expect widespread rainfall to develop near and along this boundary,
particularly late Wednesday night into early Friday when the
boundary looks to be in closest proximity and progged precipitable
water values approach climatological maximum for the time of year.
Given recent lowland flooding and fairly moist ground from recent
snowmelt even in drier areas, a return to at least minor flooding
looks to be a significant threat. GEFS and NAEFS ensemble river
forecasts show at least a chance of moderate flooding along portions
of the mainstem rivers, but this will obviously depend significantly
on the position and speed of the front, which varies depending on
guidance source.

As the front drops south of the area over the weekend, guidance
differs in the handling/possible phasing of upper level energy and
the developmental position of any surface cyclone, and thus the
resultant rapidity with which the frontal zone pushes back
northward. Will need low rain chances to handle this uncertainty
through the weekend and the end of the period as the blended
initialization indicates, but significant rainfall appears less
likely during the latter portion of the long term.

Added thunder per convective indices and forecast soundings Thursday
afternoon and evening. Strong deep layer shear appears likely, but
as is often the case this time of year, degree of destabilization is
highly uncertain, and a persistent midlevel inversion depicted in
model soundings further complicates matters. There may be a period
during this time frame when a deeply saturated/moist adiabatic
profile allows for upstream development and maintenance of one or
more clusters or complexes of thunderstorms with an attendant hail
and damaging wind threat, and will have to monitor this closely.

Outside of thunderstorms, synoptic winds look to be fairly strong
through FROPA as well, and gusts may approach 30-35 MPH at times
Wednesday and 30-40 MPH at times Thursday.

Temperatures continue to overperform guidance and given low level
thickness progs see no reason why this will not continue at least
until frontal passage. Have adjusted max temps upward Wednesday
through Friday.

&&

.AVIATION...(Discussion for the 090600Z TAF Issuance)

Issued at 1122 PM EST Mon Mar 8 2021

IMPACTS: VFR conditions are expected through the period.
         Gusty winds are expected again Tuesday afternoon.
         Low level wind shear develops Tuesday evening.

DISCUSSION: Quiet conditions will continue with mainly high clouds.
Gusty winds will return by Tuesday afternoon. Direction will be S to
SW. As surface gusts diminish Tuesday evening, low level wind shear
will develop with strengthening winds aloft.

&&

.Fire Weather...
Issued at 318 PM EST Mon Mar 8 2021

Elevated fire danger will continue for the rest of the afternoon
with a reasonably well mixed boundary layer...RH values dropping to
25-30% and gusty southwest winds. Expect similar conditions on
Tuesday afternoon. Fuel moisture values in the 7 to 8 percent range
will be the only criteria met on a widespread basis...but 20 foot
winds will approach or exceed 15 MPH at times again on Tuesday
afternoon in some areas. While dewpoints will be on the increase...
quality mixing will be working against this rise. Minimum RH values
will likely drop to a minimum around 30% Tuesday afternoon.

True Red Flag conditions are unlikely the rest of this afternoon and
on Tuesday afternoon...however will message this situation to
relevant partners in the fire weather products.

&&

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

$$

Update...50
Short Term...Ryan
Long Term...Nield
Aviation...50
Fire Weather...Ryan


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