019 FXUS61 KILN 161952 AFDILN AREA FORECAST DISCUSSION National Weather Service Wilmington OH 352 PM EDT Thu May 16 2024 .SYNOPSIS... Southwest flow in the Ohio Valley will increase moisture ahead of a surface low that will remain west of the region. Upper level shortwave energy in a mean southwest flow will interact with the moisture, producing an area of showers with some thunderstorms that enters from the west late tonight. A more pronounced shortwave is expected to continue this wet pattern through the day Friday, possibly lingering overnight in some spots. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... The overall message of overspreading showers is pretty uniform for tonight, continued differences in model solutions bring an element of uncertainty to the table. This is more concerning the timing of the leading edge but to a lesser extent coverage and placement. Looking at forecast soundings, the pre-storm environment shows steep low level lapse rates. These rates are found in the yet unmixed layer below the LFC and quickly become less favorable as the moisture becomes deeper with the mixing found on the leading edge of this activity. Likewise, most unstable CAPE values under 400 J/kg are only briefly found at the onset of precip. This is indicative of an atmosphere that does not have a forcing mechanism in the lower levels such as tonight. Mid level vorticity appears to be the driving force for upward motion. The smaller areal nature and wider range of placement of the shortwave, as well as location and timing of associated vorticity maxima necessitate a broad brush in rain and thunderstorm chances tonight. Given the lack of indicies supporting discrete thunderstorms, expect this to be more of a showers with some thunder flavoring for the overnight hours. Used pops >40% to include a slight chance of thunder and pops >50% for a chance of thunderstorms. Increased low level moisture and incoming clouds from the west will limit low temperatures to the lower 60s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Showers and some thunderstorms will continue across the CWA Friday, potentially lingering overnight for some locations, moreso in the southeast. While particularly strong storms are not expected through the period, some sw-ne training may occur and increase the flood potential. Highs in the mid 70s may be on the warm side if a cooling rain process is noted to linger in the afternoon for some locations. Overnight will keep a slight southerly flow in a moist airmass once again. Lows will drop to around 60. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Southern stream mid level low to track east thru the Ohio Valley Saturday. Moist sounding profile and slow storm motion could lead to a threat for some localized heavy rain and flooding with the focus looking to be across ILN/s southern counties. Model solution spread continues regarding the speed of this system. Have followed a slightly more progressive solution, only keeping a slight chance in the far east by Sunday. A narrow mid level ridge will build across the area late Sunday into Monday, providing a brief period of dry weather. This dry period will be short lived, as the flow backs westerly turning more progressive. Moisture increase with a gradual increase in instability but due to lack of forcing have limited pops to low chance category on Tuesday. Moisture and instability increases ahead of a stronger trof with a surface cold front moving thru the area Wednesday. Given potential moderate instability and the passage of stronger front - will have to watch this period for the potential for strong storms. Warm temperatures to continue with highs likely reaching the 80s by Sunday and then in the lower and middle 80s on both Monday and Tuesday. Highs remain above normal but pull back into the mid and upper 70s Wednesday and Thursday. && .AVIATION /19Z THURSDAY THROUGH TUESDAY/... Weakening/disorganized showers will approach from the west after 06z, possibly including some embedded thunder without organization of cells, clusters, or line segments. Have held any prevailing -shra/-ra until just before daybreak, and only restrict vsbys during the morning in a tempo group. While thunder could be present, several uncertainties described in the near term forecast remain in play. Best forecast right now is to include thunder when it can be reliably indicated as moving in from upstream, which should not happen until later tonight. Expect a lot of the -ra/-shra to be VFR and fall from a mid level deck 8-10kft. There will be stronger elements in a scattered nature on Friday that would be expected to drop vsbys into MVFR. Cigs may briefly appear in MVFR category but all indications attm are for lower cloud cover to be the outlier. Light/variable wind will become ssw late tonight and then wsw during the day, increasing to 7-10kt. OUTLOOK...MVFR CIGs/VSBYs are possible with showers and possible thunderstorms on Friday into Friday night. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Franks NEAR TERM...Franks SHORT TERM...Franks LONG TERM...AR AVIATION...Franks