Area Forecast Discussion
Issued by NWS Wilmington, OH

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839 FXUS61 KILN 241048 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 648 AM EDT Tue Apr 24 2018 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 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. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... 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. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... 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. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/...
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VFR conditions continue across the TAF sites this morning with precipitation moving in from the south. Upper level low pressure will slowly progress east-northeast this morning with the upper level jet strengthening over eastern Ohio. This has allowed for precipitation across our area to quickly start to fill in. The forecast remains largely unchanged this morning as high res models continue to show precipitation near KCMH/ KLCK expanding (due to the strengthening upper level jet and low level convergence) with precipitation across our southwest weakening this afternoon (due to dry air entrainment). This means that there will likely be a decrease in coverage around KCVG/ KLUK this afternoon while showers continue everywhere else. As the precipitation expands this morning ceilings will slowly fall into MVFR. This evening the mid level low will progress east with a deformation band pulling east across the TAF sites as well. The extent spatially and temporally of this band is uncertain as the mid level low looks to open up. This will trend towards the deformation band starting to weaken as it heads east. Given the latest trends on the high res models though the general thought is that the deformation band will likely hold together through the TAF sites (this matches the GFS and ECMWF keeping the low closed further east). Borderline IFR/ MVFR ceilings will then be possible overnight. High res guidance continues to highlight KDAY/ KCVG/ and KILN going to possible IFR with KCMH/ KLCK being to far east. Wednesday morning as winds turn from the north precipitation will quickly come to an end with the ceilings recovering. OUTLOOK...MVFR ceilings possible Friday night.
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&& .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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