Area Forecast Discussion
Issued by NWS Indianapolis, IN

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395 FXUS63 KIND 011031 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 631 AM EDT FRI JUL 1 2016 .UPDATE... The AVIATION Section has been updated below. && .SYNOPSIS... Issued at 355 AM EDT Fri Jul 1 2016 A cold front will move quickly through the area this morning and may bring a few showers and storms. High pressure will then return with dry pleasant weather into Saturday. A much more unsettled and active pattern sets up beginning Sunday through the early part of next week as the front returns back into the region and becomes nearly stationary. Warmer weather will arrive later next week along with the potential for more storms as central Indiana resides on the edge of an expanding upper ridge. && .NEAR TERM /Today/... Issued at 355 AM EDT Fri Jul 1 2016 Plenty of clouds present over central Indiana early this morning as a cold front moves into the region from the northwest. Scattered convection has gradually increased in coverage over the last few hours in the vicinity of the boundary over northwest Indiana back into central Illinois. 07Z temps ranged from the mid 60s to the lower 70s. Primary focus for today is on precip chances during the morning as the front sweeps across the forecast area. Weak lift along and immediately ahead of the front and subtle instability will be the main drivers of showers and storms through the next several hours but with limited moisture and little forcing aloft...hard to justify more than chance pops through the morning hours. Hi-res guidance has this thinking captured well...led by the WRF with the HRRR playing catchup. Any rain will be gone by midday as the upper wave and surface front quickly move off to the southeast and are replaced by a renewed surge of drier air and deep subsidence. Water vapor imagery showing a slug of very dry air currently present across the mid Mississippi Valley. Expect this to advect into the area by late morning with sunshine increasing as the day progresses. Mainly clear skies are expected by late afternoon as high pressure builds into the area. Temps...expect temps to warm nicely this afternoon in the drier airmass. Trended towards warmer METMOS which was supported by forecast low level thermals. Should see highs ranging from he mid 70s into the lower 80s most locales. && .SHORT TERM /Tonight through Sunday Night/... Issued at 355 AM EDT Fri Jul 1 2016 Forecast challenges focus on increasing threats for locally heavy rainfall by late weekend as the front returns north into the region and becomes quasi-stationary. Initially...high pressure will maintain dry pleasant weather through most of Saturday as it drifts slowly through the Ohio Valley. Model soundings and RH progs show the deeper layer of subsidence remaining over the region into Saturday...aided by low level flow veering from northerly to E/NE. Chances for rain will slowly increase from the southwest Saturday afternoon and night as moisture and isentropic lift arrive into the region. The drier airmass will be slow to saturate however with more widespread rain holding off for many until near or after daybreak Sunday. Upper energy currently over the Four Corners region will eject out into the central Plains on Saturday then shift east into the Ohio Valley by Sunday. Additional upper waves will follow as an easterly flow aloft aligns between a flat but strong ridge across the far southern part of the country and deeper upper lows along the western and eastern Canadian coasts. This will draw moisture with a Pacific origin east into the central Plains...mid Mississippi Valley and Ohio Valley. At the same time...southwest low level flow will develop around the back side of the Bermuda high and transport rich tropical Gulf moisture into these same regions for the second half of the weekend into early next week. The remnant frontal boundary will be drawn back north in response to the waves aloft kicking out to the east...and will serve as a focusing mechanism for repeated rounds of locally heavy rainfall beginning in the central Plains Saturday and shifting east into the Ohio Valley for Sunday and Monday. To the chagrin of many...confidence continues to grow in negative impacts for those with outdoor plans both Sunday and Monday as the frontal boundary will likely set up somewhere across the southern portions of Illinois and Indiana. The exact location of where the boundary ends up will be a big factor in where the heavy rain axis aligns. With that being said...numerous factors are strongly suggestive of a period of moderate to locally heavy rainfall focused from late Sunday afternoon into Sunday night and for some...likely persisting into Independence Day. The dual moisture surges coming from both the Pacific and Gulf will produce an impressive axis of high precip water values at 2 to 3 standard deviations above normal for July...in excess of 2 inches across much of central Indiana. Precip efficiency is maximized along and south of the I-70 corridor as deep convergence up to 700mb organizes at the nose of a 40-45kt low level jet Sunday afternoon and night. Strong frontogenetical forcing and diffluence aloft are also present along the boundary and should further enhance rainfall coverage and intensity Sunday night. Feel comfortable raising pops for the entire area and focusing the highest pops at this time along and south of the I-70 corridor for Sunday and Sunday night. There are still likely to be some fluctuations in the heaviest rainfall and where the frontal boundary aligns but as discussed above...numerous signals supporting the mention of heavy rainfall for the southern 2/3 of the forecast area late Sunday into Sunday night. The severe threat south of the front should largely remain just south of the forecast area...but again any northward bump to the boundary would bring that possibility into play for Sunday and Sunday night. Lots still to work out in the coming 24-48 hours ahead of the rain. Temps...felt a model blend generally handled highs and lows well through the period. With the rain/storms and clouds on Sunday... there exists a real possibility that highs have a difficult time even making it to 70 in some locations. The record for coolest high for July 3 is 70 at Indy from 1924 and that could be in jeopardy. && .LONG TERM /Monday through next Thursday/... Issued at 236 AM EDT Fri Jul 1 2016 Ensembles suggest system that is expected to affect the area during the tail end of the short term will will in the process of passing off to the east early next week. Will keep PoPs going in the forecast for Monday into Tuesday to cover this system. By the middle of next week, ensembles agree on shifting heat ridge eastward more towards the Plains and Midwest, but there are differences in how aggressive this ridge builds into the local area. Some ensembles suggest ridge will build over the Ohio Valley, effectively capping off convective threat by the middle of next week, while others keep the center of the ridge more over the southern Plains. This would allow for the potential for periodic convective clusters along the edge of the heat ridge to affect the area. For now, will keep some small chance PoPs in the forecast for next Wednesday and Thursday to cover this possibility. && .AVIATION /Discussion for the 011200Z TAFS/... Issued at 630 AM EDT Fri Jul 1 2016 Convective activity that had impacted KLAF earlier has moved off to the east, while the rest of the activity upstream is diminishing in intensity. Lightning potential in the vicinity of the terminals doesn`t look too impressive this morning, however threat for scattered showers will linger into the mid to late morning hours as a cold front drops through. Could be a period of MVFR ceilings 015-025 in the wake of frontal passage through midday, but with quite a bit of dry air upstream, ceilings should scatter out this afternoon. Surface winds expected to veer around to 320-350 degrees by mid to late morning as front passes by, with speeds 9-12 kts. && .IND Watches/Warnings/Advisories... NONE. && $$ SYNOPSIS...RYAN NEAR TERM...RYAN SHORT TERM...RYAN LONG TERM....JAS AVIATION...JAS

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