Greenfield, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

880
FXUS63 KIND 150534
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1234 AM EST Fri Nov 15 2024

.KEY MESSAGES...

- Cloudy through early Saturday then partial clearing.

- Rain chances return Tuesday followed by a trend toward cooler
  temperatures by the end of the week.

&&

.FORECAST UPDATE...
Issued at 836 PM EST Thu Nov 14 2024

Would not rule out patchy drizzle over eastern sections the rest of
the evening but for the most part, the drizzle looks to be very
spotty and should end soon as the upper ridge builds in from the
east. Hi-Res soundings are showing a saturated column from 3K feet
to the surface through the overnight under a very strong inversion.
Thus, the low stratus will hang around and despite WNW winds,
upstream temperatures and dew points are about the same as over
central Indiana. So, will keep temperatures from falling much more
with overnight lows in the middle and upper 40s looking good.

&&

.SHORT TERM (This evening through Friday)...
Issued at 220 PM EST Thu Nov 14 2024

In the wake of departing trough, advection is generally neutral. Low-
level moisture is still present as is evident in satellite imagery
with broad area of low stratus. Lower tropospheric moisture depth
and steepening low-level lapse rates may be enough for shallow
convective showers into the evening. These often have small drops
and are more like drizzle, though they can be heavier and more
intermittent. Coverage/intensity should decrease this evening, but
stratus will persist through tomorrow. We have lowered temperatures
slightly tomorrow as we expect similar condition to today with
persistent stratus limiting surface heating.

&&

.LONG TERM (Friday night through Thursday)...
Issued at 220 PM EST Thu Nov 14 2024

Fog initially seemed at least possible Friday night into Saturday
morning, but stratus looks to persist into this period. Low level
moisture trapped beneath a strong subsidence inversion this time of
year often results in prolonged stratus. On the western edge of the
stratus, fog is more likely, but this now appears to be in Illinois
or Missouri. With PBL moisture becoming less and mixing on Saturday,
stratus is likely to break around midday. By then, mid-high clouds
from the upstream system and Pacific moisture plume, in addition to
increasingly MSLP gradient should limit potential fog Sunday
morning.

We will be on the windward side of the mean ridge axis Sunday, so
temperatures will be about 10 degrees above mid-November climo.
We still have low probabilities of rain for portions of the area
Sunday night into early Monday, but trends in almost all of the
ensemble models have been for less coverage and further north.
This is tied to a trend toward a less amplified northern stream
shortwave trough. There is still modest moisture return indicated
in the models and ascent with a midlevel thermal gradient, so will
leave slight chance in.

Still warm Monday and Tuesday as ridging resurges preceding the next
system. There is limited ensemble spread on lead shortwave trough
passing to our northwest Tuesday. Its associated warm conveyer
belt/moisture surge should bring a band of rain Monday night and
early Tuesday, but cold advection will be minimal as this trough
weakens and moves east at the same time digging trough evolves over
the Plains.

Wednesday onward we will enter a period of low-mid range
precipitation probabilities and colder temperatures. The synoptic-
scale pattern is still somewhat uncertain as EPS-weighted clusters
hold the Plains trough west longer, while GFS is deeper and more
progressive. This may primarily impact temperatures Wednesday as the
former camp offers an opportunity to warm prior to the onset of
stronger cold advection, compared to the latter camp. Details with
regards to periods of enhanced forcing/ascent with rotating
vorticity maxima are unclear. Also, cold advection magnitude appears
to be modulated by substantial high-latitude ridging in this
blocking pattern, so whether or not temperatures are cold enough for
snow late next week is not totally clear. Temperatures will be
marginal. Steep lapse rates beneath the cold core low would support
a more showery regime.

Day 8-14 will start off with troughing, and there appears to be some
signal for this to persist. Near to below normal temperatures
and near normal precipitation would result.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1233 AM EST Fri Nov 15 2024

Impacts:

- MVFR/IFR cigs and vis slowly improve after 15z this morning


Discussion:

MVFR to IFR cigs and vis will continue through the early morning
hours at all TAF sites in Central Indiana. Latest ACARS soundings
and satellite imagery show low level moisture and clouds trapped
within the lowest 1km agl with the back edge of the cloud deck still
along the Mississippi River. Cyclonic flow around a departing area
of low pressure near Detroit will keep winds out of the NW around 10
kts overnight with the chance for drizzle in such a saturated
environment. Patchy areas of fog mixed in with the low stratus may
reduce visibility at times through the late morning hours.

Lower confidence exists with how fast conditions improve during the
day. Potential exists for MVFR cigs to stick around much of the
afternoon, which is certainly possible due to the lower sun angle
this time of year. The current TAF calls for cigs to raise to VFR
levels by late afternoon/early evening; however will have to keep a
close eye on satellite trends later today and adjust TAFs
accordingly.

&&

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

$$

UPDATE...MK
SHORT TERM...BRB
LONG TERM...BRB
AVIATION...CM