Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 240045 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 845 PM EDT Sun Jul 23 2017 .SYNOPSIS... A cold front will approach the region tonight and will then move southeast across the Great Lakes and Ohio Valley on Monday. High pressure will build into the area for Monday night and Tuesday. Drier weather and cooler temperatures will ensue behind the front. As the high moves east of the region on Wednesday, more humid air will return as another frontal system is expected to affect the region by late in the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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Right entrance region of upper jet streak over the eastern Great Lakes has the WFO ILN forecast area firmly in the right entrance region with enhanced background ascent ahead of a primary shortwave trough axis in western MI. This kinematic forcing amidst a seasonably moist boundary layer had allowed for uptick in convection centered on peak heating, mainly in the northern half of the forecast area. The 24.00Z KILN sounding exhibited modest instability /MLCAPE to 900 j/kg/ but appreciably weak/moist mid level lapse rates /5 C/km in 700-500 mb layer/. Further still, effective shear of ~25kts was keeping storm organization at bay, yielding a number of mostly non-severe multicell bands of convection which are now shifting east out of the area. Expect by 10 PM the vast majority of the rain will be gone, and skies will be partly cloudy most of the night. Still looks like some patchy fog is likely given remaining very high boundary layer dewpoints /70s/. Forecast low temps were nudged up just a bit, and other trends of the forecast improved in comparison with radar/satellite.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... A cold front is expected to move southeast across the region on Monday. Morning fog and/or stratus will be replaced by diurnally driven cumuliform clouds by afternoon. The front should be making its way across our far eastern and southern zones by afternoon. Thus, there is a chance of showers and thunderstorms developing along and ahead of this boundary before it clears our area by Monday evening. Highs on Monday will range from near 80 north to the mid 80s south. By Monday night, as the front moves south away from our area, surface high pressure will begin to build southward into the Great Lakes. This will bring drier air as well as seasonably warm July temperatures by Tuesday. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Building surface high pressure will bring a respite to the Ohio Valley with significantly lower dewpoints in the upper 50s to low 60s. Return flow will set up later in the day Wednesday, with a return to middle and upper 60s dewpoints ahead of the next frontal system. Moisture will pool on southwest winds through Thursday, when lower 70s dewpoints are found ahead of the next cold front. Later in the day Thursday and overnight is when the best chances for the next round of thunderstorms occur with the frontal passage and associated upper level trough. A secondary and stronger upper trough will cross late Friday and early Saturday, but the atmosphere behind the earlier frontal passage will not be receptive to the development of storms and rain chances during this time remains at a relative minima. Temperatures Wednesday will warm to the upper 80s to around 90 in the sunny and dry airmass. Cloud cover should hamper high temperatures on Thursday by a few degrees from Wednesdays highs, with the remainder of the week and Tuesday coming in right around seasonal normals. Overnight lows will be near seasonal normals in the lower 60s as well, with a maxima on Wednesday night in the upper 60s to around 70. Building surface high pressure will bring a respite to the Ohio Valley with significantly lower dewpoints in the upper 50s to low 60s. Return flow will set up later in the day Wednesday, with a return to middle and upper 60s dewpoints ahead of the next frontal system. Moisture will pool on southwest winds through Thursday, when lower 70s dewpoints are found ahead of the next cold front. Later in the day Thursday and overnight is when the best chances for the next round of thunderstorms occur with the frontal passage and associated upper level trough. A secondary and stronger upper trough will cross late Friday and early Saturday, but the atmosphere behind the earlier frontal passage will not be receptive to the development of storms and rain chances during this time remains at a relative minima. Temperatures Wednesday will warm to the upper 80s to around 90 in the sunny and dry airmass. Cloud cover should hamper high temperatures on Thursday by a few degrees from Wednesdays highs, with the remainder of the week and Tuesday coming in right around seasonal normals. Overnight lows will be near seasonal normals in the lower 60s as well, with a maxima on Wednesday night in the upper 60s to around 70. High pressure will build behind the next frontal system at the end of the week for another stretch of days with seasonal temperatures in a comfortable airmass.High pressure will build behind the next frontal system at the end of the week for another stretch of days with seasonal temperatures in a comfortable airmass. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... Pretty widespread showers and thunderstorms across the central Ohio terminals (LCK and CMH) and more scattered to the west/southwest (ILN and DAY) through early evening as shortwave trough and low level trough axis shift into the area. Have TEMPO groups to account for this MVFR/IFR activity. After 02Z things should quiet down and VFR conditions expected until about 06Z to 09Z when weak surface convergence and still a very humid airmass should come together with light winds/some clearing to produce some MVFR visibilities at most sites. Have continued to hit lower visibilities at a few sites as well in the hours before sunrise. On Monday, should see scattered cumulus as the primary cold front shifts through the area. Do expect some storms to fire along this feature but right now it looks like this will be southeast of the terminals. Light west/southwest flow tonight and Monday morning turns northwest in the wake of the cold front Monday afternoon. OUTLOOK...Thunderstorms will be possible Monday and Thursday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hickman NEAR TERM...Binau SHORT TERM...Hickman LONG TERM...Franks AVIATION...Binau

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