Area Forecast Discussion
Issued by NWS Wilmington, OH

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479 FXUS61 KILN 060557 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 1257 AM EST Tue Dec 6 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 THIS MORNING/... Southern stream upper low over eastern TX to open up and lift northeast into the lower MS VLY by morning and further deamplify as it tracks into the Ohio valley Tuesday. Associated surface wave to track northeast into the region ahead of the upper s/w. Rain over the TN valley ahead of this system to spread north to near or just north of the Ohio river by 09z and then overspread ILN/s FA, early on Tuesday. Have slowed down precipitation based on observation and model trends. Temperatures to have non-diurnal trace, falling off and then steadying out or slowly rising late. Previous Discussion... 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 THIS 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 /06Z TUESDAY THROUGH SATURDAY/...
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TAFs are currently VFR as mid and high clouds stream n ahead of low pressure in the deep south. The low will track ne up the wrn side of the Appalachians today. Mesoscale models continue to delay the onset of the rain ahead of the system, now showing a 09Z-10Z time frame for it to reach the srn tafs. The low is forecast to reach srn KY by 12Z, then it will fill as it moves farther n. Despite this, there is plenty of convergence at H9 and H8 across the region, so the the rain is expected to overspread TAF sites from south to north quickly after 12Z. Ceilings are forecast to drop to IFR as the boundary layer saturates due to the steady rain. As the low tracks off to the east after 18Z, a cold front will sweep through the TAF sites. Rain will end late around 20-21Z for the wrn tafs and a few hours later for the ern tafs. Behind the cdfnt, winds will turn to the w and will increase, with gusts of 20 kts possible. Cigs will try to lift to MVFR in the w behind the front, but the should linger in the IFR range further e. Some drizzle will be possible during the late afternoon and evening hours of Tuesday as the forecast soundings are showing drier air aloft coming in over the trapped low level moisture. OUTLOOK...MVFR ceilings will persist into Wednesday morning. MVFR ceilings are possible again on Friday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines NEAR TERM...Haines/AR SHORT TERM...Haines LONG TERM...Franks AVIATION...Sites is the U.S. government's official web portal to all federal, state and local government web resources and services.