Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 191033 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 633 AM EDT Mon Mar 19 2018 .SYNOPSIS... Today will start off dry, before an area of low pressure brings rain to the area Monday evening into Tuesday. Tuesday night into Wednesday surface low pressure will form over West Virgina bringing accumulating snow to the region. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Most of today will be dry across Ohio as the region remains in between two systems. The system that brought beautiful weather Sunday to the area will be located off the east coast with a potent mid level low centered over the Kansas/ Oklahoma border. Weak low level WAA will commence this afternoon, but clouds will remain thick across the region. Due to this think high temperatures will be very similar today as they were yesterday. By late this afternoon the mid level low will be located across southeastern Missouri with surface low pressure located over western Kentucky. Looking at GFS and NAM forecast soundings there will still be plenty of low level dry air in place with light returns probably confined to northern Kentucky and eastern Indiana. This means some of the light returns will probably start out as virga. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... This evening precipitation will begin to overspread the region as the low levels finally moisten up and condensation pressure deficits approach 0 MB. The mid level low will also begin to open up over Indiana late this evening allowing PV to wash over the region. In the upper levels the feature will try to take on a negative title with upper level diffluence occurring across Kentucky and far southern Ohio. The surface low itself will track across central Kentucky with the ILN forecast area remaining on the northern cold side. As the surface low tracks northeast towards Charleston, WV the deformation band will begin to pivot over the area. Early Tuesday morning the deformation band will be setup west/east across southern Ohio and northern Kentucky and will begin to orient southwest/ northeast into the afternoon. The northern edge of the deformation axis will likely have a sharp cutoff with drier air just north. This means our southern counties will likely see rain Tuesday morning with Dayton possibly having to wait until late morning before observing precipitation. As the precipitation heads north Tuesday morning the NAM is indicating a small window where freezing rain might occur on the northern fringe (such as Dayton). As of now the NAM appears to be the outlier. Overall thinking is that by the time the northern edge of the precipitation makes it north surface temperatures will be above freezing. Temperatures Tuesday afternoon will likely remain in the upper 30s to around 40 with the widespread cold rain. Late Tuesday afternoon into early evening a reinforcing shot of cold air will begin to push southeast out of Canada in the form of another shortwave. As this happens rain will start to mix with snow northwest of Dayton. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... A broad upper level trough will shift slowly east across the region Tuesday night through Wednesday night. As it does a weak 850 mb low/wave will move east across the upper Ohio Valley with an inverted surface trough nosing northwest into our area. The models have been fairly consistent with the broader features with this system over the last several runs, but the 00Z deterministic models continue to shift around quite a bit with their exact location and amounts of heavier QPF Tuesday night into Wednesday. Complicating matters is that given the time of year, the thermal profiles will be somewhat difficult to forecast, particularly during the daytime hours and ground temperatures will likely start off relatively warm. Widespread precipitation is expected across our area Tuesday night and likely lingering into at least Wednesday morning before beginning to taper off from the northwest through Wednesday afternoon. Expect the precipitation to start off as mainly rain early Tuesday evening, but then change over to snow fairly quickly as we begin to cool off and lose some of the diurnal enhancement. Expect precipitation then to remain mainly snow through the remainder of the event, even into Wednesday as boundary level temperatures should remain cool enough to support mainly snow. The 00Z NAM remains the wettest and snowiest, with a decent axis of heavier snow forecast to set up across northern portions of our area while the 00Z ECMWF has also trended quite a bit wetter/cooler and is also indicating the possibility for some decent snowfall with warning criteria type totals across parts of our area. However, the 00Z GFS and CMC are less impressive, but still suggesting possibly some higher end advisory type totals across parts of the area. The GEFS mean across our area is somewhat lower, generally in the 3 to 4 inch range with similar numbers from the 00Z EPS mean. Considered possibly going with a watch for at least part of our central forecast area where we have the lower 4 inch criteria, but confidence is just not high enough at this time given all of the uncertainties. As a result have opted go with snow amounts generally in the 2 to 4 inch range with amounts closer to 4 inches across parts of our north. High pressure and a drier air mass will build across the area Wednesday night into Thursday. We will remain well below normal though with highs on Thursday only ranging from the upper 30s in the north to the mid 40s across the south. Mid level ridging across the area on Friday will quickly break down as short wave energy pushes in from the northwest. This will allow for a surface low to move east across the Ohio Valley Friday night through Saturday night. This will result in an increasing chance of precipitation Friday night into Saturday before tapering off through Saturday night. Ptype will again be an issue with this system with at least a rain/snow mix possible across northern portions of our area and mainly rain across our south. Highs through the weekend will be in the 40s with overnight lows mainly in the 30s. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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All TAF sites are currently VFR this morning with some cirrus and low end VFR clouds across the south. This afternoon surface low pressure will move into Missouri with the pressure gradient increasing. This means wind gusts will be possible with GFS and NAM forecast soundings indicating 15 to 20 kts (via momentum transfer techniques). Tonight cloud bases will continue to slowly lower as surface low pressure moves in from the west. Widespread upglide will mean a band of precipitation oriented from west to east will slowly move north and reach Cincinnati between 2 and 6z. There is a lot of dry air in atmosphere as of current so virga will likely be observed initially. Tuesday morning into afternoon the band of precipitation will begin to pivot and take on a southwest to northeast orientation and overtake all of the TAF sites. As this happens ceilings will lower to MVFR and then IFR. Wind gusts will also approach 25 kts with surface low pressure just off to our southeast. OUTLOOK...MVFR/IFR ceilings and visibilities are possible Tuesday through Wednesday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines NEAR TERM...Haines SHORT TERM...Haines LONG TERM...JGL AVIATION...Haines is the U.S. government's official web portal to all federal, state and local government web resources and services.