Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 161320 AFDILN AREA FORECAST DISCUSSION National Weather Service Wilmington OH 920 AM EDT Mon May 16 2022 .SYNOPSIS... Showers with some embedded thunder continue to move through early Monday morning before pushing eastward. High pressure builds in late Monday, offering dry and pleasant conditions through Tuesday. The pattern quickly becomes more active by Wednesday, with periods of showers and storms expected through the end of the work week and into the start of the next weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Sharp mid level trof over the area to shift east with northwest flow developing. Widespread showers and thunderstorms have shifted off to the east with the trof, leaving just a few residual post frontal showers over the far northeast. Northwesterly flow aloft will allow for cooler and drier air to filter in. Latest visible satellite imagery shows lingering clouds, which will break apart from the west as we head into the afternoon. Colder air aloft will result in steep low level lapse rates which will allow for some cu development. Forcing is limited but with this low level instby there may be a few stray showers over the far north. Therefore, have kept a slight chance mention in the far north. Highs are expected to be in the low to mid-70s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Weak surface high pressure builds in from the west as the Ohio Valley becomes positioned downstream of an H5 ridge. As drier air advects in, clouds will dissolve Monday evening and leave us with mostly clear skies overnight. Combined with weakening westerly surface winds, lows will be able to bottom out in the low to mid-50s. Tuesday will be very pleasant as we remain downstream of an H5 ridge. Limited moisture availability will allow skies to remain mostly sunny throughout the day. Additionally, dewpoints in the mid 40s to near 50 will keep outdoor humidity levels in the comfortable range. Tuesday night continues to remain quiet, but we will begin to observe a breakdown in the H5 ridge, with flow aloft becoming more quasi-zonal. Cloud coverage will begin to increase from west to east overnight, but the forecast remains dry during this period as of now. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... An active weather pattern is expected for the start of the long term period as several quickly-moving S/Ws track E across the OH Vly within the quasi-zonal/NW flow atop a quasi-stationary WNW-ESE oriented LL frontal boundary. The first of several midlevel disturbances will track E through the OH Vly late Tuesday night into the day on Wednesday. This will promote the development of some convection toward daybreak Wednesday and beyond, which will be primarily elevated in nature until better LL destabilization can occur later into the day on Wednesday from the SW. This initial batch of SHRA, with perhaps a rumble of thunder or two, is likely to move quickly through the ILN FA through the first half of the day Wednesday. It will leave in its wake a trailing WNW- ESE oriented baroclinic zone draped across the southern OH Vly, potentially very close to the OH Rvr. As the initial S/W pulls E, better sfc theta-e advection will become established by late Wednesday afternoon through the evening hours, with LL destabilization efforts underway, initially for SW parts of the local area during this time frame. There remain quite a few of uncertainties in the fcst at these time ranges, but the setup for active weather locally does seem to carry with it some degree of concern for episodic SHRA/TSRA from Wednesday evening through even the day on Thursday. Not only would this portend the potential for one or more episodes of storms, but also the risk for repeated convectively-driven heavy rain leading to hydro concerns as well. The better shear profiles are likely to evolve Wednesday evening into early Thursday morning as LL destabilization continues to increase from SW to NE during this time frame. The primary source for lift on Wednesday evening/night will be the convergent axis stretching from WNW to ESE across southern IN/OH and N KY. Although the best H8 LLJ will be pulling E toward later Wednesday evening/night, there will still be some subtle convergence along the LL boundary amidst an environment of increasing LL moisture advection/convergence. And as the initial S/W energy pulls E, a better northward surge of deeper moisture will commence for the second half of the day Wednesday, especially across far S/SW parts of the OH Vly. One of the main questions that remains for Wednesday evening/night is just how much forcing/lift will evolve, which will ultimately dictate the degree to which convection can reinitiate or be sustained along the aforementioned boundary. One thing that does appear to be a concern is the potential for renewed/repeated convection Wednesday evening/night near the boundary with a steering-layer flow that will largely overlap the LL boundary and source lift while sfc inflow into the boundary will remain normal to it. This creates a scenario where training of convection may be favored, potentially in the form of one or more convective complexes, suggesting a hydro concern may very well come into play. Of course, the details of where this would be favored are far from certain at this point. There does remain some latitudinal variability in the guidance regarding where this boundary will set up, but it would appear that locales near/south of the OH Rvr would be more in-line for this potential at this juncture. The signal is certainly there for one or more convective complexes Wednesday evening/night across the southern OH Vly, with the hydro threats more of a concern locally than the severe threat with the best LL thermodynamic environment staying in the far south, or potentially just south, of the ILN FA. With the potential for numerous SHRA/TSRA within a narrow WNW-ESE corridor in the southern third or quarter of the ILN FA Wednesday evening/night, the setup for the daytime Thursday becomes even more uncertain, especially with questions regarding presence of a source of lift and whether the cap can hold. One thing that does appear to be likely is the continued theta-e advection N further into the ILN FA, with high, to potentially extreme, instby developing during the daytime period. The intricacies of how this will all unfold are far from clear at this juncture. But... there appears to be enough overlap in the shear/instby parameter spaces to yield more than just a little concern for one or more rounds of strong to severe storms, if the nosing of the LLJ by midday can promote enough lift to generate some convective initiation. The overall pattern/setup is more than favorable for a severe weather episode during this time frame, but the degree to which this evolves, especially regarding coverage of storms, will take some time to reveal itself. Very bluntly, there is some guidance that shows a window for sufficient overlap of high instby amidst sufficient deep-layer speed and directional shear to suggest that all severe hazards, including flooding, may come into play at one time or another Thursday, particularly for locales south of the I-70 corridor. The caveat is whether the environment becomes uncapped or there is sufficient lift to overcome it. It could end up being a scenario where we progress into the morning on Thursday and are still not certain whether the cap will be overcome. Nevertheless, the signal is strong enough that felt it is prudent to start mention in the HWO, at least in a broad sense to begin with. By later Thursday evening into the night, midlevel height rises will commence locally as the trof across the upper Midwest digs into the central plains. This amplifying midlevel ridge axis will position itself across the heart of the ILN FA Friday, favoring drier, but certainly plenty warm and humid, conditions for the final workweek of the week. Friday looks to be the warmest and most uncomfortable day of the week, with temps likely reaching into the upper 80s with DPs in the mid/upper 60s. Guidance still differs quite a bit of variation regarding the timing of the front through the ILN FA sometime in the Friday night through Saturday time frame. Either way, the FROPA will offer renewed chances for SHRA/TSRA pretty much everywhere before drier and cooler conditions filter in late on Saturday in the post frontal environment. While there certainly could be a strong to severe storm potential with the FROPA, the more concerning and pressing signal for Wednesday night (mainly hydro/low end severe) and Thursday (hydro/severe) takes precedence at this juncture. Will hold off on further discussions regarding the FROPA Friday night/Saturday for now until the details come into better focus. && .AVIATION /13Z MONDAY THROUGH FRIDAY/... A few lingering showers may be observed at KCMH/KLCK this morning before pushing eastward. Dry conditions are favored for the remainder of the day, although an isolated shower/storm cannot be completely ruled out this afternoon. Due to low confidence and probability of occurring, did not include in the tafs. Low level moisture behind the cold front will keep some MVFR/IFR CIGs over the terminals through the mid morning hours. Drier air in the upper levels moves in and breaks apart those lower CIGs, allowing MVFR CIGs to return by the late morning hours. Wind gusts out of the west-northwest of around 20-25 kts will be possible by the afternoon. Winds will subside by the evening and decrease below 10 kts for Monday night. OUTLOOK...Thunderstorms possible at times Wednesday into Thursday. MVFR conditions possible Friday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Clark NEAR TERM...AR SHORT TERM...Clark LONG TERM...KC AVIATION...Clark

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