Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000 FXUS63 KIND 201930 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 230 PM EST Fri Jan 20 2017 .UPDATE...
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The SYNOPSIS...NEAR TERM and SHORT TERM Sections have been updated below.
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&& .SYNOPSIS...
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Issued at 230 PM EST Fri Jan 20 2017 Mild and unsettled weather will continue across the Ohio Valley this weekend with opportunities for scattered showers and a few thunderstorms. After a brief break from the wet weather...another storm system will track through the region the middle of next week with colder temperatures more typical of late January and possibly chances for light snow arriving by late week.
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&& .NEAR TERM /Tonight/...
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Issued at 230 PM EST Fri Jan 20 2017 Damp gray afternoon continues across central Indiana as the region remains under a shroud of thick clouds and patches of drizzle. A few breaks in the stratus noted especially closer to the Ohio River... but trend has been for those to disappear over the last hour or two. A mild January day in progress as 19Z temps were primarily in the 50s. First in a series of waves of energy aloft kicking out from the deep upper low off the Pacific Northwest coast will rotate into the northern Plains behind the wave from last night. While this feature will not have a direct impact initially on central Indiana...it will aid in bringing a combination of weak isentropic lift and warm advection expanding northeast with a warm front into the region tonight. This will bring another round of showers...albeit they will be more scattered and much much lighter compared to Thursday night. Focus for the best threats for light showers and/or drizzle will be across the northwest half of the forecast area where the isentropic lift will be a bit more pronounced. Precip amounts will be a couple hundredths at best and will not have any impact regarding ongoing flooding concerns. In addition...areas of fog will continue overnight as well and possibly worsen after dark with the well defined inversion persisting over the region. Should begin to see improvements develop from the south predawn Saturday as low level mixing increases south of the warm front and with the aid of a strengthening low level jet. Temps...another night with very little movement regarding temperatures. Lows will be well above normal as the southerly flow and warm advection keeps the region largely in the lower and middle 50s. Trended much closer to the warmer MET guidance.
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&& .SHORT TERM /Saturday through Monday/...
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Issued at 230 PM EST Fri Jan 20 2017 Forecast challenges focus on precip chances and temperatures throughout the short term as the active...unsettled and mild weather regime continues. A moist southwest aloft will continue over the region into Sunday as a dominant subtropical jet undercuts the upper low off the Pacific Northwest and kicks out upper level waves downstream across the eastern half of the country. Much of Saturday now appears relatively quiet for central Indiana as the warm front lifts away to the north and subtle ridging aloft develops between the aforementioned upper wave tracking into the upper Midwest and a developing upper low strengthening over the Southern Plains. Shallow isentropic lift will continue on Saturday but limited forcing aloft at best should maintain dry conditions across the forecast area until late day at the earliest. Model soundings show the inversion persisting between 1000-2000ft for much of the day Saturday an combined with the isentropic lift present below 900mb...suspect the stratus will remain through midday in abundance with perhaps some breaks during the afternoon as low level flow increases and aids in enhanced mixing of the boundary layer. A deep upper low sitting off the Pacific Northwest coast with a strong subtropical jet undercutting the wave will maintain an active weather pattern across much of the country through the weekend as pieces of energy aloft continue to eject out into the central Plains east into the Ohio and Tennessee Valleys and the Deep South. Upper level flow over the region will largely persist in a moist southwest regime through Saturday night. Deeper moisture will be drawn north beginning late Saturday and especially Saturday night as the southern Plains upper low tracks east and an intensifying surface wave organizes over the mid South. Increasing low level convergence and the development of diffluent flow aloft supports scattered convection increasing across the entire area Saturday night. Elevated instability maximizes with progged MLCAPE values up to 500 J/KG and will continue with a thunder mention as a result. Precip water values will rise up to 0.80 to 1 inch Saturday night...250-300% of climatological normal. While higher precip amounts should be much more localized than recent events...additional flooding concerns could extend out through the weekend after the heavy rains experienced Thursday night. Rain chances will continue Sunday and Sunday night as the upper low tracks across the Southeast and into North Carolina by Monday morning...amplifying as it does so. The surface low will continue to intensify as well...residing northwest of the upper low over the central Appalachians by early Monday. The close proximity of the surface low will maintain periods of generally lighter rain across the region within a cyclonic flow. Should begin to see chances for rain shift east of the area through the day Monday as the surface low tracks slowly northeast into the mid Atlantic region and deeper moisture gradually moves out of the forecast area. Temps...warm weather will continue Saturday and Sunday as low level thermals are supportive of highs ranging from the upper 50s to the mid 60s north to south. While this is unusually warm...record highs for both days at Indy look safe by several degrees. Noticeably cooler weather with highs in the 40s are expected Monday as colder air is drawn into the region behind the east coast storm system.Lows will be generally in the 40s through the period.
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&& .LONG TERM /Monday night through Friday/... Issued at 205 PM EST Fri Jan 20 2017 The long term will begin with above normal temperatures and small rain chances moving out of the area as an upper ridge builds in and moves across central Indiana. Tuesday night a low pressure system will approach from the plains and bring small chances for rain with it. By Thursday though a broad upper trough across the western and central U.S. will start to slowly move east, and this will bring cold more seasonable air back to the area. Temperatures will drop back to near normal for this time of year. Little upper waves ejecting out of the upper trough could bring some precipitation chances to the area for the remainder of the extended, but right now there isn`t a major forcing mechanism to focus on so just used the small off and on chance pops from the initialization. Because of the arrival of the colder air, could see some snow or a rain/snow mix for anything that falls Wednesday night on. && .AVIATION /Discussion for 201800Z TAF Issuance/... Issued at 1138 AM EST Fri Jan 20 2017 Poor flying conditions will continue for the rest of the day into tonight with some improvements for Saturday. Areas of fog and pockets of drizzle continue to impact the terminals late this morning as moisture remains trapped beneath a strong inversion. As progressively drier air advects into the region...should see the drizzle diminish early this afternoon but the lower ceilings will continue under the inversion. Expect ceilings generally persisting at a sub-IFR level into the overnight with visibilities likely holding in the 3 to 5SM range. Light SW flow this afternoon will back to southerly and increase tonight as a warm front lifts north. The passage of the frontal boundary will enable a relaxing of the inversion to some degree on Saturday and increased low level mixing will enable improvements in ceilings into the MVFR category through the course of the day. S/SW winds will continue with the potential for gusts in some areas during the afternoon. It now appears that rain and scattered convection now is likely to hold off on causing more significant impacts at the terminals until after 00Z Saturday evening. && .IND WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS...RYAN NEAR TERM...RYAN SHORT TERM...RYAN LONG TERM....CP AVIATION...RYAN

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