NWS Wilmington, OH Office (ILN)

Area Forecast Discussion/SKEW-T

          FXUS61 KILN 161038
          National Weather Service Wilmington OH
          638 AM EDT Mon May 16 2022
          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.
          Radar imagery shows a fairly robust line of showers moving
          through the central portion of our CWA at 4 AM this morning.
          NLDN and GLD lightning plots do show some embedded thunder
          within these showers. Most of the convection continues to remain
          elevated, which will limit severe potential the remainder of
          this morning. However, several ASOS/AWOS sites have observed
          wind gusts in excess of 30 mph with the gust front and embedded
          within these showers as they move through.
          Majority of pcpn will have moved east of our fa by mid-morning
          as the cold front will have worked its way through.
          Northwesterly flow aloft will allow for cooler and drier air to
          filter in. Clouds will break apart more by the afternoon, but
          some instability will build back in with the cold air aloft and
          will help with some cu development. While forcing may be
          limited, the presence of some instability and steepening low
          lapse rates may allow for a stay shower/storm to develop.
          Locations in central and west-central OH will have the best
          chance of this occurring, so kept a low-end PoP in those
          locations. Otherwise, a cooler and generally pleasant day will
          take shape as we progress into the afternoon. Dewpoints will
          begin to fall into the 40s, and daytime highs are expected to
          remain in the low to mid-70s.
          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.
          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
          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
          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.
          NEAR TERM...Clark
          SHORT TERM...Clark
          LONG TERM...KC

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