426 FXUS61 KRLX 091752 AFDRLX AREA FORECAST DISCUSSION National Weather Service Charleston WV 152 PM EDT Wed Jun 9 2021 .SYNOPSIS... Summer-like tropical airmass remains in place through Friday. Approaching weak upper low yields better coverage of precipitation today than the previous few days. && .NEAR TERM /THROUGH TONIGHT/... As of 1027 AM Wednesday... Mainly light showers with some embedded moderate pockets of rain continue to slowly pivot through the area this morning on the nose of a modest LLJ. With overcast conditions still locked in across the region, how much destabilization materializes later today is still in question but if some partial clearing can occur, rainfall rates will need to be closely monitored for anything that develops in this very moist air mass. Based on latest radar trends, made some minor tweaks to PoPs with the update this morning but the remainder of the forecast remains on track at this time. As of 600 AM Wednesday... Made some minor edits to PoPs based on latest guidance/radar trends. Based on the 06Z will continue to forgo a flash flood watch with surface based destabilization suppressed for a large portion of the area with temperatures struggling to get of the 70s. Will need to monitor sky/temp trends through this afternoon. As of 300 AM Wednesday... A 20-30KT low level jet associated with the weak upper low parked over the Lower Ohio Valley will be the main focus for sustained showers and thunderstorms beginning this morning, persisting through much of the day, and lingering overnight tonight. As with the last few days, the environment is characterized by tropical-like profiles with precipitable water values 1.7 to near 2.0 inches, warm cloud depths in excess of 12kft, CAPE generally below the 0C isotherm, and sfc to H400 mean wind under 15KT supporting highly efficient rainfall production as well as slow storm movement. Unlike the last few days, destabilization via surface heating may be a bit harder to come by with precipitation processes initially driven by low level mass convergence creating a pretty good cloud canopy limiting insolation this afternoon. Despite only modest instability, should still see some healthy rainfall rates out of much of the activity today and tonight with the previously mentioned factors, with likely greater basin coverage than has been seen with the last few days of mainly scattered convection. While precipitation coverage will be much greater, thunderstorm coverage will likely be be about the same or even less with limited instability above 0C. With mass convergence at H850 and proximity of the low being the main drivers for ascent, shower and thunderstorm activity will likely continue well after sunset tonight and into Thursday morning. As with previous days, the main concern with this activity will be localized flash flooding of especially vulnerable areas (built up areas, areas of poor drainage, exits to hollows with substantial coverage of decent rainfall rates in the watershed). Would generally expect lesser rainfall rates than have been seen with convection over the last couple days with more muted instability, although as previously mentioned, coverage of drainage basins will likely be more complete. Did strongly consider hoisting a flash flood watch, especially for a few spots that have been run over pretty hard with slow moving convection the last couple days, but just don't quite have the confidence that rates will be high enough to cause any more widespread issues. This will be revisited with the 06Z suite and again by day shift if we elect to hold off. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 335 AM Wednesday... An upper level wave deepens to become more trough-like on Thursday as it moves through the area. The models show this feature as the southern stream of a general troughing pattern over the eastern US and potentially phase the northern and southern streams into Friday as the trough continues to move toward the east/southeast, then break the two apart again as the southern half lingers along the Atlantic through the weekend. This feature will continue to provide forcing to the area for shower and thunderstorm development. At the lower levels, a frontal boundary approaches reaching the area sometime on Friday providing additional forcing for the area as it passes through. The shower and storm activity both Thursday and Friday are expected to be relatively widespread throughout the area. By Friday night, precipitation coverage should begin to decrease as the front passes through and out of the area. Currently not expecting any severe weather with any thunderstorms, however flooding issues will continue to be of concern. The entire area is under a slight risk for excessive rainfall on Thursday and conditions will continue to monitored with the additional rainfall received today to assess whether any Watches will be issued or not. Areas that have received a lot of rainfall so far this week as well as vulnerable areas that are prone to flooding may have high water issues as the week progresses. For Friday, most of the area is in a marginal risk for excessive rainfall and the very western portion of the area is in a slight risk. Temperatures for Thursday and Friday will generally be around normal. With dewpoints up in the upper 60s to 70s for the lowlands and low to mid 60s along the higher elevations, humid conditions will continue through the end of the work week. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 350 AM Wednesday... Shower and thunderstorm activity is expected to begin to settle down by the weekend as the aforementioned upper level trough continues to move off to the east/southeast and ridging builds in to the west. However, isolated to scattered storms will remain possible for the weekend. Models indicate a cold front potentially moving through the area on Monday. They also generally agree with showing an upper trough gradually pushing down into the area Monday into Tuesday with diurnal showers and thunderstorms continuing to be possible into the next work week. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 153 PM Wednesday... Widespread light to moderate rain continues to slowly pivot through the area today ahead of an upper level low in the Ohio Valley. Instability has been limited due to the overcast skies preventing any appreciable heating, so have not included any mention of VCTS within TAFs at any terminals for the remainder of the day. However, poor aviation conditions are generally still expected through the remainder of the day as the area remains blanketed in low stratus and the widespread precipitation will continue to result in visibility restrictions. Thus, expecting MVFR/IFR conditions across mainly western terminals through this evening, but for terminals such as KCKB/KEKN/KBKW, conditions may remain VFR through the evening as the coverage of precipitation should remain less and ceilings should generally be higher. Regardless, flight conditions are expected to deteriorate areawide during the overnight hours as low stratus and/or valley fog develops, particularly in areas that received the heaviest rain today. Thus, a prolonged period of IFR conditions or worse will be possible overnight across the area. Unsettled weather will generally remain in control on Thursday as the aforementioned upper low continues to slowly approach the area so scattered to numerous showers and thunderstorms will be a possibility on Thursday for all terminals. Outside of any convection on Thursday, ceilings should gradually rise to around MVFR or low end VFR by the afternoon hours. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z THURSDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Ceilings and visibilities vary in rain through tonight. Coverage and density of fog/stratus tonight may vary from forecast. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. UTC 1HRLY 17 18 19 20 21 22 23 00 01 02 03 04 EDT 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY H H H H H H H H H L H H HTS CONSISTENCY H H H M M M H H H H H M BKW CONSISTENCY M L H H H H H M M M H H EKN CONSISTENCY H H M H L L L M M M H H PKB CONSISTENCY H H H H H H H H H H H L CKB CONSISTENCY M M M M L L H H L M H L AFTER 18Z THURSDAY... Chances for scattered to numerous thunderstorms remain in the forecast through Saturday with possible IFR reductions. Patchy fog possible each morning through Saturday, especially where rain falls the preceding day. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...JP/CG NEAR TERM...JP/RG SHORT TERM...CG LONG TERM...CG AVIATION...RG