Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
093 FXUS63 KIND 122257 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 657 PM EDT Fri Jul 12 2024 .KEY MESSAGES... - Fog possible again tonight, with locally dense fog - Periodic shower and thunderstorm chances through Wednesday, some uncertain potential for strong to severe storms - Hot and humid from Sunday through Tuesday, possibly nearing Advisory criteria && .SHORT TERM (This evening through Saturday)... Issued at 304 PM EDT Fri Jul 12 2024 Scattered convection so far today has been confined to far eastern portions of the forecast area near the apex of a weak upper wave passing through. ACARS sounding from KIND shows less moisture in the low levels versus Thursday afternoon and with weaker forcing aloft, convective coverage has been much lower this afternoon. 18Z temperatures were in the mid and upper 80s most areas within a muggy airmass. The upper level transition is beginning from the progressive flow of weak waves to more of a stronger influence from ridging aloft with mid level heights set to rise for Saturday. While the presence of instability and low level moisture supports at least isolated mainly afternoon and early evening convection, the focus through Saturday will shift to warmer and mainly dry conditions as the upper ridge builds in. Isolated to scattered convection will remain focused especially across eastern counties through the afternoon with a gradual eastward shift into Ohio as the upper wave moves away from the region. Convective mode will again be disorganized, pulse intensity multicellular storms with locally heavy rainfall and lightning as the main hazards with gusty winds possible within any collapsing downdraft. Expect any storms to wrap up by early evening leaving a muggy evening and overnight. Mid and high level clouds will drift across the region through daybreak. Similar to this morning, suspect fog development will commence once again with locally dense a possibility as well with light winds and a shallow layer of moisture in the near surface layer lingering. Focus for best chances of fog will be across the northern half of the forecast area which saw some of the highest rainfall totals over the last 3-4 days. Fog will diminish by mid morning Saturday as mixing gets going within the boundary layer and just based on model soundings, the fog may diminish more quickly than it did this morning. Expect diurnal cu formation again by Saturday afternoon but coverage should be less than what we have seen over the last few afternoon with the increased mid level heights and a greater amount of dry air and subsidence present above the boundary layer. Once again, an unstable airmass will be conducive for isolated convection favored during the afternoon and early evening, but a decrease in low level moisture and little to no forcing aloft under the expanding ridge will limit overall development. Localized downpours will be most common with slow moving. and disorganized storms but most will remain dry throughout the day Saturday. Temps - lows tonight will remain in the mid and upper 60s throughout the forecast area. Low level thermals are supportive of highs a few degrees warmer than today in most locations, with upper 80s to around 90 expected. && .LONG TERM (Saturday night through Friday)... Issued at 304 PM EDT Fri Jul 12 2024 A fairly typical midsummer pattern is expected over the weekend into early next week, characterized by broad, strong upper level ridging centered over the Four Corners region, and a strong subtropical ridge over the western Atlantic nudging back into the southeastern CONUS. This will leave the region under quasizonal or weakly northwesterly flow aloft, with prolonged southerly or southwesterly flow at the surface setting the stage for maintenance of a hot and steamy airmass, and possibly multiple rounds of convection, primarily late days into the overnights with (still fairly low) chances highest to the north as possible storms developing and traversing the periphery of the ridge may get into the area. As the week wears on, the upper level pattern will amplify as shifts in location and intensity of the mean ridges allows for an anomalous upper level trough to swing into the Great Lakes and drive a surface boundary southward into the area. This will allow for some heat relief, but also may produce higher chances for thunderstorms on multiple days as the tail end of the frontal zone sags through the region. Gradual height reduction aloft and the approach of this aforementioned frontal zone by mid week, along with the ridge riding convection early in the week, may offer one or more opportunities for strong to severe storms, though predictability is fairly low at this time given the dependence of convection in such patterns on preceding rounds of thunderstorms. There is some signal in experimental machine learning guidance for this, which will bear watching. The primary concern with these storms would be damaging winds, along with heavy downpours and localized flooding given recent significant rainfall and seasonably high wet bulb zero heights promoting highly efficient warm rain processes. Temperatures early in the week will again be quite warm, with high humidity promoting a possible heat threat, primarily Sunday through Tuesday, though convective potential will increase uncertainty in this regard. Significant relief from the heat appears likely late in the week as the front passes. && .AVIATION (00Z TAF Issuance)... Issued at 657 PM EDT Fri Jul 12 2024 Impacts: - MVFR/areas of IFR conditions redeveloping overnight tonight into daybreak Saturday. Discussion: Isolated showers should remain east of KIND very early in the period. Otherwise, cumulus will dissipate into the evening hours. With light winds and lingering low level moisture, fog is likely to develop again. Questions remain on how low visibility will get, given some drying that occurred this afternoon. For now will go with IFR or worse at KLAF with MVFR and BCFG elsewhere. Visibility will likely change rapidly at times. Fog will mix out early then scattered cumulus will pop up again. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Ryan LONG TERM...Nield AVIATION...50