152 FXUS63 KIND 301821 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 221 PM EDT Fri Aug 30 2019 .UPDATE... The LONG TERM Section has been updated below. && .SYNOPSIS... Issued at 353 AM EDT Fri Aug 30 2019 A weak frontal boundary will meander across the region into the weekend as disturbance aloft traverse the Ohio Valley. These features will provide periodic chances for a few showers or thunderstorms through Sunday. After a warm and dry start to next week...low pressure will track into Quebec and pull a front across the region late Tuesday into Wednesday with the potential for rain and storms. Cooler weather is expected for the second half of next week. && .NEAR TERM /Today/... Issued at 929 AM EDT Fri Aug 30 2019 Cold front currently progressing through the northwest sections of the forecast area. Latest short term model guidance continues to suggest scattered convection possible over the southern half of the area by the early to mid afternoon hours along the front. Current forecast handles this well. This morning's upper air suggests today's high may be a little on the cool side. Considering the amount of high cloud, will leave the highs alone for now, and reevaluate temperatures later. No updates planned at this time. Previous discussion follows. Eastern edge of the cirrus canopy associated with a convective complex over the central Plains continues to drift across the region early this morning. Pockets of stratocu were present as well...especially over northern counties as a weak frontal boundary approached from the north. 07Z temperatures ranged from the mid 60s to the lower 70s. The frontal boundary will slide south into central Indiana today and eventually become quasi-stationary across southern counties by this afternoon as it runs into a high pressure ridge extending from the Tennessee Valley east into the Carolinas. A stronger wave aloft contributing to the storms over the central Plains and Missouri Valley early this morning will kick east into the region by late day. While a few isolated showers cannot be ruled out this morning as the front drops south...the combination of the wave aloft and the boundary should both provide enough forcing to generate scattered convection this afternoon focused mainly south of Interstate 70. CAMs show an axis of modest instability pooling in the vicinity of the boundary by mid to late afternoon with MLCAPEs peaking near 2000 j/kg. Couple limiting factors in play however that would support keeping more numerous storm coverage from developing. Deep moisture is lacking and there appears to be just a short 2-4 hour window where a subtle cap in the 5-10kft range weakens enough to reach the instability levels mentioned above. Lapse rates also appear a bit problematic for more robust convective coverage with steeper values being confined to the lower 3-4kft. Will carry chance pops south of I-70 for the afternoon with highest threat extending along an axis south of a Sullivan-Bloomington- Greensburg line. Not entirely out of the question that any stronger storm may carry a wind threat as cores collapse but overall expect convection to remain below severe levels today. Temps...low level thermals generally support low to mid 80s for highs across the forecast area with warmest readings near and south of where the boundary eventually stalls in our southern counties. An overall model blend should work nicely. Will be a fairly modest spread on humidity levels from north to south across the forecast area by afternoon. Drier air will advect into the region from the north behind the front with dewpoints in the upper 50s in the northern Wabash Valley and near 70 over south central Indiana. && .SHORT TERM /Tonight through Sunday Night/... Issued at 353 AM EDT Fri Aug 30 2019 Forecast challenges focus on a middling but persistent convective threat that will likely run into Sunday as the Ohio Valley remains within a northwest flow regime aloft on the edge of the expanding upper ridge. Any convection near the front this evening will diminish with the loss of instability and heating shortly after sunset. Presence of the front beginning to lift back north slowly across the region however will warrant a low chance for an isolated shower or storm the remainder of the night into Saturday morning. Diurnal heating will again bring a subtle increase in convective coverage Saturday afternoon and evening focused near the expected location of the front across the northern Wabash Valley. Instability will likely be lower on Saturday but low level lapse rates are steeper. The best chance for greater convective coverage still appears to come late Saturday night into Sunday as yet another wave aloft tracks across the lower Great Lakes and interacts with the front over northern portions of Illinois and Indiana. While focus of the more widespread coverage should be north of the forecast area... model soundings are more supportive of scattered showers and storms into Sunday afternoon...especially over the northern half of the forecast area. Once the wave aloft passes...dry weather will return for Sunday night with upper level heights rising across the region in response to the expansion of the western ridge and weak surface high pressure building back in for Labor Day. Temps...should see little variation in high temperatures through Sunday with essentially the same airmass remaining over the area. Low to mid 80s are expected from north to south Saturday and Sunday. After a slightly cooler night tonight...lows will be in the 60s over the weekend. As the front shifts north...dewpoints will creep back up into the middle and upper 60s over the entire forecast area. && .LONG TERM /Monday Night through Friday/... Issued at 220 PM EDT Fri Aug 30 2019 Ensembles suggest northwesterly upper flow will continue across the local area during this period, as upper ridging holds over the southern Rockies. Main feature during this period will be a short wave trough, that is expected to move across the Great Lakes around the middle of next week. Precipitation potential looks better with this trough that it did yesterday. At this point, it appears the best threat will be Tuesday night, although some of the ensembles suggest the threat may linger into Wednesday. For now, will keep the PoPs restricted to mainly Tuesday night, and continue to monitor trends. && .AVIATION /Discussion for the 301800Z TAFS/... Issued at 1245 PM EDT Fri Aug 30 2019 Diffuse cold front currently drifting south across the area. Appears it is close to the KIND/KHUF terminals at this time. Short term model data suggest scattered convection is possible, mainly in the vicinity of the KBMG terminal, through the early evening hours in association with this front. Brief IFR visibility restrictions in the heavier cells. CB bases around 035. Otherwise, some diurnal cloud, along with some layered cloud, near the 035-050 layer, expected through the early evening hours. Surface winds expected to become 340-010 degrees at 6-9 kts by late this afternoon in the post frontal zone, with winds gradually veering to 030-050 degrees by late evening. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...Ryan NEAR TERM...Ryan/JAS SHORT TERM...Ryan LONG TERM....JAS AVIATION...JAS