IND issues Area Forecast Discussion (AFD) at Dec 5, 6:26 PM EST628
FXUS63 KIND 052326
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
626 PM EST Thu Dec 5 2024
.KEY MESSAGES...
- Another cold night with substantially lighter winds; single digit
wind chills around daybreak Friday
- Rain returns late Sunday night into Monday with heaviest rain
across southern Indiana
&&
.SHORT TERM (This evening through Friday)...
Issued at 146 PM EST Thu Dec 5 2024
Arctic high pressure over the mid-Missouri Valley will continue to
drop south/southeastward into the lower Mississippi and Tennessee
Valleys tonight into Friday. The repositioning of the high will
allow low level flow to back somewhat, becoming more westerly and
southwesterly late tonight into Friday. This will lead to a slight
modification of temperatures to begin tomorrow after one more quite
cold night, though more substantial warming will definitely wait
until the weekend.
A compact shortwave trough will drop through the northwest flow
aloft on the backside of the primary longwave trough late tonight
into early Friday, but the only impact of this should be a modest
increase in mid and high cloud either side of daybreak Friday,
though a substantially dry column will likely limit this to shallow
scattered cloud above 8-10kft at the lowest. A bit more cloud may
impinge upon the northeastern portions of the area off the lake, but
the aforementioned extremely dry air should prevent flurries from
making it all the way into central Indiana, and will exclude any
mention tonight.
The high center will remain well to our west and southwest
overnight, so while winds will be substantially lower tonight,
leading to better radiational cooling conditions, there will still
be at least light winds overnight, perhaps keeping lows from
completely bottoming out. Still, lows are likely to drop again into
the low teens and perhaps even upper single digits in favored spots.
Onset of modest warm advection tomorrow will help temperatures
recover a bit more substantially tomorrow, with highs pushing the 30
degree mark across the area.
&&
.LONG TERM (Friday night through Thursday)...
Issued at 146 PM EST Thu Dec 5 2024
Friday Night Through Monday.
Upper level flow will remain northwesterly Friday night going into
the weekend but surface ridging over the Southern Appalachians will
help to pivot the surface flow to a more southerly direction by late
Friday night. This will allow for gradual warming this going into
the weekend with highs approaching 50 by Sunday.
Focus then shifts to a low pressure system exiting the southern Four
Corners Region and tracking rain chances as it moves to the
northeast. There isn't very strong surface cyclogenesis with this
system, but there will be a rapidly strengthening LLJ that will
advect large amounts of Gulf Moisture and bring PWATs well into the
90th-95th percentile of climatology by late Sunday night.
There has been a slight southern shift to the axis of heavier
precipitation as a stronger trough across southern Canada is causing
the northerly component of the initial trough passage to be less
pronounced and would keep the heaviest rain south of the Ohio River.
This southerly shift will also limit the already low chances for
thunderstorms that were initially possible.
There then is a potential for a secondary to to develop on the
backend which could keep precipitation around into Monday, but
confidence is low as ensembles show that solution remains to be the
outlier vs most likely outcome.
Tuesday Through Thursday.
Cooler weather then is expected Tuesday into Wednesday but overall
confidence in the forecast is low beyond that. There a signal in
precipitation chances late Monday night through Wednesday ahead of a
stronger upper level system that will impact the East Coast, but the
better chances for precipitation again look to be south of the Ohio
River where the northern extent of Gulf moisture is expected to
reach while Indiana remains north of a nearly stationary front.
Looking mid-week and beyond the upper level flow will again become
cyclonic which introduces at least the potential for weak waves and
brief low QPF snow events.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 625 PM EST Thu Dec 5 2024
Impacts:
- Winds at KIND/KLAF from 280-290 degrees around 7KT through 03Z
Discussion:
Broad, cold Canadian high pressure currently centered over Missouri
will steadily glide to the Tennessee Valley by the end of the TAF
period. Gradient over this ridge's northeastern quadrant has waned,
which will promote surface flow under 7KT 3Z tonight through 14Z
Friday...while winds back slowly across westerly directions.
Only aviation concern tonight will be KLAF/KIND possibly catching
the western edge of lake-effect clouds, which would be no more than
FEW/ SCT...with no visibility concerns.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
SHORT TERM...Nield
LONG TERM...White
AVIATION...AGM
Source:
IND issues Area Forecast Discussion (AFD) at Dec 5, 6:26 PM EST---------------
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