Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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660 FXUS63 KIND 081003 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 603 AM EDT Mon Jul 8 2024 .KEY MESSAGES... - Partly Cloudy Today; Chances for afternoon showers/storms in the Wabash valley; Warm - Increasing clouds overnight with shower/storm chances over mainly Western Central Indiana. - Remnants of Beryl may bring isolated tornadoes and flooding Tuesday evening through Wednesday morning - Tornado threat highest south of I-69, flood threat greatest to the north && .SHORT TERM (Today and tonight)... Issued at 241 AM EDT Mon Jul 8 2024 Surface analysis early this morning shows a strong and large area of high pressure centered over NY. A ridge axis extended SW from this high to southern Indiana and Western KY. Winds across Central Indiana were light and variable to calm. Water vapor imagery showed a deepening trough axis over the northern plains states, stretching southwest to NB and eastern CO. This was resulting in a SW flow of moisture aloft, streaming from the southern plains toward Central Indiana. An upper low was found over eastern MN. GOES16 shows mostly clear skies over Indiana, however mid and high cloud were found over MO and IL streaming northeast toward Indiana. Today... The upper trough axis over the plains states is expected to deepen and begin to push east toward the Mississippi Valley. This will keep a warm and humid SW flow in place across Central Indiana. Meanwhile Beryl is expected to make landfall and quickly begin to turn north and northeast within the flow ahead of this trough and begin to push toward Central Indiana. That, however, is more of the story for Tuesday. Meanwhile at the surface the strong surface ridging from the high to the northeast is expected to remain in place, providing relatively calm but warm summer weather today. Forecast soundings show a dry column today, with a weak mid level inversion that appears to weaken as the day progresses. HRRR suggests that as the upper trough nudges eastward, convection over IL late in the afternoon may reach the Wabash Valley after 21Z. Thus will keep a dry forecast for most of the area today. However by late afternoon introduce some low chance pops in far western Central Indiana for this possible convection. Given the little change in the overall air mass, will trend highs at or above persistence, in the upper 80s. Tonight... A change in our weather is expected to begin tonight. The protective surface high pressure is expected to push father east, while the trough axis to the west aloft will continue nudging toward Central Indiana. Through the night, moist SW flow aloft is seen trending forecast soundings toward a more saturated column. A fully saturated column is not reached until Tuesday, but weak disturbances within the SW flow aloft along with a warm and humid air mass results in convection upstream drifting toward Central Indiana overnight. HRRR suggests areal coverage of these showers and storms to be rather limited, but still enough elements will be present to necessitate showers and storm chances, particularly across the western parts of the forecast area. Given the expected clouds and warm air mass, lows near 70 or the lower 70s will be expected. && .LONG TERM (Tuesday through Sunday)... Issued at 241 AM EDT Mon Jul 8 2024 Tuesday and Wednesday. The main focus and hazardous weather in the long term period will be focused Tuesday evening through Wednesday morning as tropical moisture from the remnants of Beryl impact Indiana. There remains quite good model agreement in the track and timing of the remnants with the latest set of model guidance with the final details likely to come into alignment after landfall towards daybreak today. This system`s hazards will be two-fold. The first and primary threat will be the potential for tornadoes and damaging winds within the warm sector of the final track which currently looks to set up along and south of the I-69 corridor Tuesday evening into the early overnight hours ahead of the surface low. Model soundings show good turning in the lowest 3km with 0-1 SRH in excess of 300 m^2/s^2 through 06Z Wednesday which would be more than enough to allow for brief lower end tornadoes. With the tropical nature, lapse rates will be moist adiabatic which will limit the instability and higher end threat, but with the robust low level shear, the threat is definitely there for brief, low-end tornadoes. The second threat will be pockets of flooding. The combination of warm temperatures aloft which will make this a primarily warm rain process and PWATs near climatological records will allow for a very efficient rain process with brief periods with rain rates of 1-2 inches per hour likely. The heaviest rain is expected just to the northwest of the surface low which currently looks to impact mostly Illinois and far northwestern Indiana with the swath of 3-5 inches of rain currently forecasted to the northwest of the forecast area along the narrow frontogenetical band, but the peripheries near Lafayette certainly have the potential to see 2-3 inches. Areas to the southeast are more likely to see amounts closer to 1-2 inches which will certainly help the ongoing drought but shouldn`t be as impactful. A Flood Watch may end up being needed but with a combination of recent dryness, MMEFS showing little river reponse on even the higher end QPF scenarios, and the longer duration of the event, will hold off for now and highlight via an ESF. The majority of the impacts from both threats are expected to be seen from Tuesday evening through daybreak Wednesday with lingering showers and clouds expected for much of the daytime hours Wednesday. The impacts from both of the main hazards may shift in the coming days so be sure to closely follow the forecast as the exact track details become more clear. Thursday Through Sunday. The pattern in the aftermath of the remnants looks fairly benign with a weaker secondary low pressure behind the main low expected to pass through during the daytime hours on Thursday which should bring some light rain and help to keep temperatures cooler ahead of a warm- up going into the weekend as the ridge tries to build back in. Outside of the low threat for diurnally driven convection, precipitation chances look like Friday through Sunday with highs expected to climb back into the upper 80s to near 90 with dewpoints climbing to back near 70 by Sunday. && .AVIATION (12Z TAF Issuance)... Issued at 603 AM EDT Mon Jul 8 2024 Impacts: - VFR Conditions are expected this period. - Thunderstorms will be possible at LAF and HUF 21Z-02Z. - More showers/storms will be possible across all TAF sites aft 09Z Discussion: Strong and large high pressure east of Indiana will continue to control the weather across the TAF sites through mid afternoon. Once again diurnal CU will be expected this afternoon as convective temperatures are reached. Due to the developing SW flow aloft, and mid and upper moisture across the southern plains, some high cloud cigs will be pushed across the TAF site through the day. As the upper trough edges eastward, some isolated convection will be possible within the Wabash Valley late in the afternoon. HRRR continues to show isolated convection breaking out along the IL/IN state line, pushing northeast within the flow aloft. Confidence is low for specific timing, thus have used a VCTS window for now. Overnight, more showers and possibly isolated thunderstorms will be possible as the initial surges of moisture from remnants of Beryl arrive in Indiana. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Puma LONG TERM...White AVIATION...Puma