Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 052056 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 356 PM EST Mon Dec 5 2016 .SYNOPSIS... Surface high pressure was centered over the region this afternoon allowing for a few hints of sunshine. The high will quickly move off to the northeast tonight and Tuesday as low pressure moves into the Ohio Valley. A cold front will follow on the heels of the low Tuesday night, bringing drier and cooler weather behind it for mid week. Much colder weather is expected by the end of the week as another cold front pushes across the region. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Surface high pressure will pull east of the area this evening into Tuesday morning as an upper level low over south Texas gets picked up in the main flow and ejects northeast. Currently over the area there are some breaks in the low clouds with the sun making a rare appearance. Already cirrus blow off just to the south is starting to encroach on the area. Both NAM and GFS forecast soundings show this trend of low clouds thinning only to be replaced by cirrus. This evening high clouds will slowly lower to mid clouds with soundings full saturating in northern Kentucky around 8z. High res models are in pretty good agreement across the board showing precipitation starting across the southern zones between 2 and 4 am Tuesday morning and then spreading north across the CWA by 8 am. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... Looking at GFS/ NAM omega fields reveals a broad swath of low level moisture and lift moving across the area Tuesday morning. Upper level support also remains favorable as speed divergence moves over the ILN forecast area. PWATs on both the NAM and GFS also rise to around 1.10" (~ 1 to 2 SD above normal for this time of year). The surface low with this feature will track across our far southeastern zones bringing a swath of gulf moisture with it. Tuesday afternoon rain looks to continue across the area with global models indicating a potential band of higher rainfall totals across the center of the CWA (esp. on the GFS) thanks to strong low level convergence. This band of higher precip is also shown on the NSSL- WRF and WRFDART. Overall event totals of 0.5" to 1.00" are likely with some isolated totals above 1" possible (6 hr FFG is above 2.00" in most places). The surface low will then pull northeast of the area with rain coming to an end across the CWA by 7pm Tuesday evening. Also Tuesday evening an upper level low near northern Minnesota will pull east and push a surface cold front through the area. The cold front looks to be near I-71 around 1 AM Wednesday morning. During the day Wednesday colder air will start to filter into the region with 850 mb temperatures falling to around 3 degrees below zero. Looking at forecast soundings from the GFS and NAM there looks to be some partial clearing Wednesday but will be transient. && .LONG TERM /THURSDAY THROUGH MONDAY/... Thursday will start with a surface ridge building south of the area from the west and an upper level trough passing through the region. West to northwest flow at the surface will combine with northwest flow aloft to bring in significantly cooler air to the region with highs on Friday only reaching the mid to upper 20s, sandwiched with teens in the overnight hours on both Thursday and Friday night. Friday night lows may be a bit cooler with lighter winds and less cloud cover as the high pressure center settles in eastern Kentucky. The westerly flow over the region during this time will likely preclude any snow from occurring in the region, though a passing flurry is possible along and north of the I-70 corridor Friday afternoon. With the upcoming weekend, a warm front will cross northeast through the Ohio Valley and increase the threat for rain on Sunday, possibly a rain/snow mix as the warm air overspreads the cooler air in place. Models continue to disagree in how this system evolves with the ECMWF notably drier and further west than the more progressive and much wetter GFS. Modelers from WPC also seem to have split the difference here noting the warm frontal passage similar to the GFS solution on Sunday, then bows to the ECMWF on Monday morning with the surface low east of Lake Superior. GFS occludes the front off of the east coast on Monday morning and pushes in drier air. Meanwhile the ECMWF continues to keep a strong baroclinic zone in the midwest with continued threat for precipitation over the Ohio Valley during this same time frame. Tried to trend lower on the threat for precipitation on day 6 and 7 and culminated the pops on the high end category Sunday afternoon, in line with the GFS. Against better judgment and nodding towards ECMWF the pops have been lingered into Monday and Monday night to account for lower confidence and natural variability of the models on day 7. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... With surface high pressure centered along the Ohio River, MVFR ceilings trapped under a subsidence inversion are eroding from south to north. All sites may attain VFR within a couple of hours of issuance, but observations and satellite will be monitored closely in this low confidence scenario. Tranquil conditions will persist this evening as the high travels to Pennsylvania. Weather will change quickly later tonight as low pressure moves to Kentucky from the southwest. -RA will overspread TAF sites from south to north early Tuesday. IFR ceilings are expected to form, once the boundary layer saturates. Winds will generally be out of the east, with speeds rising to near 10 knots with -RA. Only slight improvement is forecast at CVG after 18z, with ceilings increasing to MVFR, while lingering RA ends and wind direction shifts to west. OUTLOOK...MVFR ceilings will persist into Wednesday morning. MVFR ceilings are possible again on Friday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines NEAR TERM...Haines SHORT TERM...Haines LONG TERM...Franks AVIATION...Coniglio

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