Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000 FXUS63 KIND 291818 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 220 PM EDT Thu Sep 29 2016 .UPDATE... LONG TERM Section has been updated below. && .SYNOPSIS... Issued at 129 PM EDT Thu Sep 29 2016 A low pressure system will stay close to Indiana through the weekend, resulting in a damp, cool, spell. From Monday through Thursday our weather should be dominated by high pressure from the deep south to New England, causing drier and warmer conditions. && .NEAR TERM (Tonight)... Issued at 129 PM EDT Thu Sep 29 2016 The models all agree low pressure through a deep level and nearly saturated air will remain over Indiana. They also agree synoptic scale forcing, as shown by strong Q vector convergence, will develop over most of the area from 03Z-09Z. The result is going to be widespread rain. Categorical POPs will be forecast most areas. Likely will be used in the northwest, which should have more of a glancing blow from the forcing. There is a chance of thunder given the cold air aloft, but most rain should be stratiform considering forcing is going to cover a lot of saturated air simultaneously. Last night a consensus forecast worked well for temperatures. The same should work tonight given most guidance is again in agreement and the basic situation hasn`t changed. && .SHORT TERM (Thursday through Sunday)... Issued at 129 PM EDT Thu Sep 29 2016 POPS are the forecast problem. The model deterministic fields all have a vertically stacked low pressure nearly over the area until Sunday, when it leaves to the northeast. The result will be plenty of clouds and showers, and possibly thunder. Exactly when rain occurs will be controlled by weak impulses embedded within the larger low pressure. At times there are relatively large differences in the model POPs, suggesting different handling of these impulses. Using a consensus will minimize errors, but POPs with this forecast may change by 10-20 percent. There is excellent agreement on temperature predictions. This indicates a consensus will work well, as it has recently. Based on the range of what different methods forecast,the consensus should have errors of 2 degrees or less. && .LONG TERM /Sunday Night through Thursday/... Issued at 220 PM EDT Thu Sep 29 2016 Sunday night through Wednesday will be dry as the upper low which will be over the eastern great lakes Sunday evening moves on to the east and a ridge of high pressure builds in across our region. The dry weather may end by Thursday as an upper trough moves into the northern and central Plains. Some models indicate a cold front may make it as far east as Illinois by the end of day 7. Will mention a slight chance of showers over western sections late Wednesday night and low chances of showers and a few thunderstorms all but far east Thursday. Temperatures will become a little warmer by the middle of next week as an upper ridge of high pressure builds into the Ohio valley. Stayed close to super blend temperatures in most cases. && .AVIATION /Discussion for the 29/18Z TAF Issuance/... Issued at 1258 PM EDT Thu Sep 29 2016 Generally VFR Ceilings through early evening followed by IFR Ceilings with rain showers late tonight and Friday morning. Then improving again toward midday Friday. An upper low pressure system will continue across Indiana through the period. Radar indicates scattered light showers were occurring across the region and ceilings generally ranged from 3 to 5 thousand feet. With daytime heating expect slightly higher ceilings as the afternoon wears on. Could see an isolated thundershower as well. Model indicate showers will become more numerous late tonight and model soundings indicate ceilings and visibilities will become IFR as well late tonight and Friday morning. Should see some improvement again by midday Friday with ceilings improving to 2 to 4 thousand feet. Winds through the period will be northerly at 5 to 10 kts. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...JK NEAR TERM...JK SHORT TERM...JK LONG TERM....JH AVIATION...JH

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