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Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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442 FXUS63 KJKL 291915 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 315 PM EDT Sat Jun 29 2024 .KEY MESSAGES... - Hot and humid weather is expected today, with afternoon highs around 90 degrees and heat indices peaking around 100 to 105 degrees in some places. - Thunderstorms are possible through Sunday as a cold front approaches and moves through. A few storms this afternoon through the early overnight could produce strong wind gusts and heavy rain. - A short-lived break from the heat and humidity is forecast on Monday behind the cold front, quickly followed by a return of sultry conditions. - An active period of showers and thunderstorms may impact the Fourth of July holiday period from Wednesday through Friday. Best chances for showers and thunderstorms as of now are expected Thursday July 4th during the afternoon and evening. Heat indices will return to near 100 degrees for many locations as well during this time period. && .SHORT TERM...(This evening through Sunday night) Issued at 253 PM EDT SAT JUN 29 2024 A series of shortwaves will maintain a broader upper level trough moving east across the Midwest, northeast CONUS, Ontario, and Quebec this weekend. We are on the southern edge of the prevailing westerlies aloft associated with the trough. The trough will support a surface cold front which will approach tonight and then pass through from northwest to southeast on Sunday. Low level southwest flow ahead of the front has transported warm and humid air across the region, with highs in the upper 80s to lower 90s and dew points in the mid 70s, with heat indices in the upper 90s to lower 100s this afternoon. Forecast soundings indicate capping in the middle atmosphere this afternoon as mid-level heights continue to rise, which has seemingly thus far prevented anything more than spotty shower activity. However, by mid-evening height falls occur as a strong shortwave moves across the Great Lakes region, and all models indicate the atmosphere becomes uncapped, with CAMS depicting one of more thunderstorm clusters moving across the forecast area from northwest to southeast, likely emanating from upstream development. As for the severe threat, the 20 to 30 kts of shear with moderate instability supports a Marginal Risk especially as any potential MCS moves southeast into the forecast area primarily this evening. With expected shower and thunderstorm activity occurring mainly this evening into the overnight, any rain followed by partial clearing toward dawn will support fog development. Regardless, expect warm and "soupy" conditions through the overnight with even the valleys remaining at 70 degrees or higher. The cold front will move southeast through the forecast area on Sunday with a similar atmospheric set-up ahead of the front. Southeast KY won`t have fropa until late Sunday and stands the best shot at seeing more thunderstorms, while the far northwest part of the forecast area is likely to have fropa before sufficient heating to support development. A much cooler and drier air mass moves into the region behind the front, with temperatures falling into the mid 50s to lower 60s, with warmer conditions in the valleys, especially if mixing from cool air advection continues through the night. .LONG TERM...(Monday through Saturday) Issued at 315 PM EDT SAT JUN 29 2024 The various guidance including the ensembles are showing that a cold front will push south of eastern Kentucky by early Monday. Then high pressure builds into the Ohio Valley ushering in northeast flow at the surface. This will aid in ushering in a much cooler and drier airmass into the region. The airmass will be anomalous for the first day of July, with PWATs running around 2 standard deviations below normal and even some indication in ensembles we could see near record min PWAT values for this time of year. The afternoon highs will be running in the mid to upper 70s for most locations and that around 5 to 10 degrees below climate normals. These cool temperatures and decent afternoon mixing will set the stage for a cool readings Monday night into Tuesday morning. That said, lows in the low to mid 50s in the valleys and mid to upper 50s on the ridges under clear skies and good agreement on building mid-level ridge for Monday night into Tuesday morning. By Tuesday, there is good agreement on mid-level heights continue to rise and high pressure pushes east allowing for some moisture return. The cold front also pushes northward as a warm front Tuesday afternoon. Even so, while warming into the upper 80s to lower 90s we will see most locations see heat indices remain in the lower 90s. This as moisture will lag behind some. However, ensembles and deterministic guidance continue to build heights and moisture into mid and late week timeframe. This will lead to warming, with highs in the low to mid 90s by Wednesday and near 100 heat indices possible at some locations. While most of Wednesday will be dry, we could see some weakening in the ridging leading to the potential for some shower and thunderstorm activity in the afternoon (around a 15-30 percent chance of rain). The various suites of guidance show this ridging breaks down further and we become quasi-zonal mid-level flow across the Ohio Valley opening up the potential for ridge riding mid-level waves. The NBM ramps up chances of showers and thunderstorms to around the 60-70 percent range peaking Thursday afternoon. This seems reasonable and some of these could be efficient precipitation producers given the PWATs come back up closer to 2 inches or higher. By the end of the week, there is some uncertainty on the evolution of the waves mentioned before. However, given the ample moisture and upstream cold front will stick with the NBM chances of rain in the 60 percent range Friday. After this the models really struggle with the passage of the previously mentioned cold front and therefore keep Saturday chances of rain in the 30 to 50 percent range for now. However, could see this fluctuating before that timeframe with some guidance suggesting it would be dry most locations Saturday. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 132 PM EDT SAT JUN 29 2024 Showers and thunderstorms will impact the TAF sites at times through the period. Main window of concern is between 00z and 12z with one or more thunderstorm clusters depicted by high-resolution mesoscale models. With a clear trend in these models, decided to be a little more on the aggressive side with timing TSRA activity this evening into the overnight. Meanwhile, until around 00z expect more isolated to widely scattered showers and thunderstorms. The spotty nature of this activity precludes anything other than a mention of VCTS at this time. A few storms could be strong to severe and produce gusty winds. If rain/thunderstorms impact TAF sites and there is any partial clearing by dawn, fog will likely impact those TAF sites. Aside from fog and precipitation, VFR conditions are expected. Light but occasionally gusty southwest winds will gradually diminish into the overnight, then become northwesterly late in the TAF period at KSYM as a cold front bringing much cooler and drier air begins to move across the area from northwest to southeast during the day Sunday, mostly after 18z. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...CMC LONG TERM...DJ AVIATION...CMC