Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 200523 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 123 AM EDT WED JUL 20 2016 .SYNOPSIS... Surface high pressure will allow for dry conditions through Thursday night. Thunderstorm chances return to the forecast for Friday with an unstable airmass. Heat and humidity will build through the week with the warmest temperatures expected from Friday through the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Surface high pressure centered over the Great Lakes will continue drifting east across the forecast area overnight, resulting in calm or very light veering winds. An MCS currently over central Illinois will likely stay west of our area overnight, with current trajectories taking it south/southeast towards the Paducah/Evansville area. However, the 19.18Z and 20.00Z NAM runs have it brushing the far western edge of our forecast area just after daybreak Wednesday. Recent HRRR runs also show some convective activity breaking off the eastern edge of the main MCS along a boundary of some sort, then weakening as it marches eastward, reaching eastern Indiana around 14-15Z Wednesday. Not sold on this scenario and have kept the forecast dry, but it is within the realm of possibility. If this would happen to occur, activity would be weakening and would just expect some showers affecting our Indiana counties. Otherwise have bumped up dewpoints a tad overnight as well as cloud cover across our southwest owing to cirrus blowoff from the MCS. Low will range from around 60 east of Columbus to upper 60s in our southwest. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/... Surface high pressure across the area on Wednesday will push to the east on Thursday. There is northwest flow aloft, however any disturbances are weak and generally east or west of the area. With no clear preciptiation signal, decided to go with a dry forecast at this time. Wednesday will be the cooler of the two days. As the high shifts to the east southerly flow will increase on Thursday and warmer air will move into the area. Heat index values will approach 100 across southwest portions of the forecast area on Thursday, however have values just under the 100 degree mark (heat advisory criteria). && .LONG TERM /FRIDAY THROUGH TUESDAY/... With an upper ridge established across the CONUS, a hot and mainly dry period is expected. For Friday, a few afternoon thunderstorms may be triggered in an unstable airmass by a short wave rounding the crest of the upper ridge. Isolated thunderstorms may still occur Saturday under weaker forcing but persistent instability. On Sunday, greater short wave energy entering the northern plains is forecast to develop a surface low that will drag cold front toward the ILN area. A better chance for thunderstorms will exist in increasing moisture and forcing ahead of the front. The chance for convection will continue Monday as the front makes its way across the area. Look for drier conditions Tuesday under weak high pressure behind the front. Temperatures will be hot. Highs in the 90s are forecast Friday through Sunday, with heat indices reaching heat headline criteria over 100. Somewhat cooler readings in the mid and upper 80s are expected Monday and Tuesday due to modest cold advection. && .AVIATION /05Z WEDNESDAY THROUGH SUNDAY/...
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Surface high pressure centered over the eastern Great Lakes this morning will continue to extended southwest into the mid and upper Ohio Valley through tonight. Some cirrus can be expected from time to time in the northwest flow aloft along with some scattered diurnal cumulus clouds. Winds will be calm or light easterly this morning, light and variable this afternoon, then back to a light east or southeast wind tonight. OUTLOOK...Thunderstorms possible Sunday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Novak NEAR TERM...Kurz SHORT TERM...Novak LONG TERM...Coniglio AVIATION...Hickman

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