Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 240740 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 340 AM EDT Tue Apr 24 2018 .SYNOPSIS...
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An upper level low pressure system will push slowly east across Tennessee and Kentucky today, bringing rain showers to the region. High pressure and drier conditions will return for mid week. Cooler than normal high temperatures will persist through the end of the week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Upper level low pressure can easily be seen rotating over southwestern Kentucky this morning on water vapor. Through the day today temperatures will stay mostly in the 50s as widespread cloud cover and rain helps to keep the diurnal range suppressed. The main story for today will be the precipitation. Most of the day will be wet as PWATs stay around 1.00" (or near the 90th percentile for this time of year). Lift will come from the upper level low as it meanders east. An upper level jet streak on the east side of the low will modulate today and quickly strengthen as the upper level low starts to get absorbed back into the main flow. This strengthening jet will place the ILN forecast area in a LFQ. This will allow for ongoing precipitation currently in Kentucky to slowly progress northeast and grow in coverage as the jet streak strengthens. The jet streak (as well as coupled low level convergence) will slowly push northeast allowing the primary band of precipitation to progress northeast. As the jet streak pivots northeast and the primary band moves over CMH, holes in the precip shield will likely start to occur somewhere across our southwest.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
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This evening as the upper level jet streak pushes east a deformation band over Indiana will slowly progress east as well. Models struggle here on how quickly the deformation band looses cohesion. The reason for this is how the mid level low begins to open up. The latest runs of the ECMWF and GFS actually hold the low together until it moves over the east coast and gets absorbed back into the main flow. This would in general imply the deformation band holding together longer. For now, have trended the TAFs this direction. Behind the deformation band, precipitation will come to a quick wind. During the day Wednesday an upper level disturbance will be swinging east across northern Michigan allowing a cold front to wash through the area Wednesday afternoon. The frontal passage will be precipitation free as mid and upper level dry air plunges south. High temperatures Wednesday will remain below normal for this time of year or around 60 degrees.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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A mid level short wave will move across the Tennessee Valley Wednesday night into Thursday. The better forcing associated with this will remain to our south while a weak surface ridge will be in place across our area. This will provide for dry but continued cooler than normal conditions on Thursday with highs mainly in the lower 60s. A sheared out trough axis will then push quickly east across the region on Friday, resulting in a chance of showers. Highs on Friday will be in the low to mid 60s. High pressure will then build into the region at the surface and aloft through the weekend with dry conditions expected into early next week. Highs on Saturday will again be in the low to mid 60s. Temperatures will then start to moderate in a developing WAA pattern. Highs on Sunday will be in the mid to upper 60s, warming to highs in the low to mid 70s by Monday.
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&& .AVIATION /07Z TUESDAY THROUGH SATURDAY/... All TAF sites are currently VFR this morning as the upper level low continues to rotate over southwest Kentucky. The upper level low will slowly progress west-northwest this morning with the upper level jet strengthening over eastern Ohio. The general idea is for the current band of precipitation over Kentucky/ Tennessee to slowly progress north during the morning hours. Later this morning into early afternoon as the jet streak strengthens just to our east the primary band of precipitation will re- orient from the CVG/ LUK/ DAY area towards CMH/ LCK. In the primary band of precipitation visibilities will likely be restricted down to MVFR. Ceilings will also slowly drop through the day today from VFR to MVFR and then IFR. Latest batch of guidance has delayed the onset of IFR ceilings by a couple of hours, so have trended the TAFs this direction. Winds today will start from the east as the surface low will be off to our south. This evening into Wednesday morning winds will back to the north as the surface low heads northeast. Occasionally gusty winds will be possible this afternoon with GFS and NAM momentum transfer showing isolated gusts of 20 kts, but given the weakening pressure gradient have just increased the sustained winds in the TAFs and not mentioned gusts. Wednesday morning as winds turn from the north precipitation will quickly come to an end with the IFR/MVFR ceilings remaining (thanks to low level moisture being trapped underneath a weak inversion). OUTLOOK...IFR ceilings and MVFR visibilities will likely continue into Wednesday morning. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines/Sites NEAR TERM...Haines SHORT TERM...Haines/Sites LONG TERM...JGL AVIATION...Haines

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