Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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982 FXUS63 KIND 181348 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 948 AM EDT Wed Sep 18 2024 .KEY MESSAGES... - Mostly sunny and hot today - RH values dropping to around 20-30% this afternoon, mainly over W/NW portions of the area - More Hot and dry weather through Saturday. - Rain Chances return Sunday - Tuesday && .FORECAST UPDATE... Issued at 947 AM EDT Wed Sep 18 2024 No major changes needed to the forecast with conditions generally evolving as expected. The main focus for today will be tracking the drop-off in afternoon dewpoints as mixing begins. There may be a few spots across western Indiana where RH values drop as low as 20 percent with the worst case scenario HRRR/WRF-ARW models showing as low as 15 percent. Without stronger winds at the top of the boundary layer, don`t think there will be mixing to that extent but did drop dew points a bit from the overnight forecast. With some high clouds across the east and moisture associated with the system that impacted the Carolinas earlier this week, dew points will remain higher across the east and southeast which will limit the fire weather concerns. && .SHORT TERM (Today and tonight)... Issued at 250 AM EDT Wed Sep 18 2024 Quiet weather conditions are expected through the period as upper ridging and surface high pressure remain centered over the region. Good radiational cooling conditions this morning has allowed many areas to quickly fall into the 50s. Look for temperatures to continue cooling through daybreak with rural locations reaching the low 50s. Efficient daytime heating promoted by a dry airmass and little cloud cover should warm temperatures well into the 80s once again today. Low RH values are likely again in the afternoon due to deep mixing. However, latest guidance shows the focus for 20-30% RH values will be over west/northwest portions of the area where lower 850mb dewpoints are expected. Subtle moisture advection from the east is expected to keep RH values from reaching critical levels over some far east/southeastern counties. Regardless, light winds will generally limit fire weather concerns. There are still county burn bans in effect for parts of central Indiana so please exercise caution if burning today. Expect another quiet cool night ahead. Good radiational cooling conditions will allow for temperatures to efficiently cool after sunset. Look for lows to bottom out near dewpoints in the mid 50s to low 60s. && .LONG TERM (Thursday through Tuesday)... Issued at 250 AM EDT Wed Sep 18 2024 Thursday through Saturday - Little overall change will be expected in the weather through Saturday. Models continue to suggest strong ridging in place over Indiana. The ridge axis is shown to stretch from TX through the western Great Lakes on Thursday and slowly shift eastward, crossing Indiana through Saturday. Through this period, strong surface high pressure is expected to remain in place, stretching from Quebec and Ontario, across Indiana to the deep south and Texas. This will keep a very warm and dry air mass across Indiana, with continued subsidence. Forecast soundings through the period show a dry column through this period. A slightly warmer air mass will settle across Indiana on Thursday and Friday. This will allow for highs in the upper 80s and low 90s through Saturday. One caveat to watch for Saturday, forecast soundings here show CAPE over 1600 J/KG with attainable convective temps. This has some potential for afternoon convection, but confidence in that remains low until we get a little closer. Otherwise, look for mostly sunny days and mostly clear nights. Sunday through Tuesday - Our persistent weather pattern finally begins to show signs of change on Sunday as the blocking upper ridge finally begins to move east. Models suggest stronger troughing aloft developing over the plains states, ejecting forcing dynamics across the middle Mississippi Valley and eventually reaching Central Indiana. Lesser chances will persist on Sunday as the ridging slowly departs, but some upper forcing arriving in the area may necessitate smaller pops for the afternoon. Confidence is lower here. Best chances for rain look to be on Monday and Tuesday as the trough axis begins to arrive in our vicinity and is accompanied by an associated area of surface low pressure pushing across Central Indiana. Forecast soundings on Monday and Tuesday trend toward saturation with pwats around 1.5 inches. Thus for now confidence is growing for a rain event on Monday and Tuesday as these features arrive in the area. The arrival of clouds and rain will allow high temperatures on Sunday through Tuesday to return to values closer to normals, in the mid and upper 70s. && .AVIATION (12Z TAF Issuance)... Issued at 625 AM EDT Wed Sep 18 2024 Impacts: - None. Discussion: VFR conditions are expected through the period. Winds will be light and variable at most sites for the next few hours before returning to east-northeast at less than 10 kts today. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...White SHORT TERM...Melo LONG TERM...Puma AVIATION...Melo