Area Forecast Discussion
Issued by NWS Wilmington, OH

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043 FXUS61 KILN 191943 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 343 PM EDT Tue Sep 19 2017 .SYNOPSIS... A weak upper level disturbance will move through the area, offering a chance of showers and thunderstorms this afternoon into Wednesday. Drier conditions are expected for the end of the week into the weekend as upper level ridging builds into the Ohio Valley. Above normal temperatures will continue into the upcoming weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Showers continue to weaken across the forecast area today as LLJ convergence weakens and PVA pulls east. Overall am expecting showers to continue to weaken with only a slight chance of showers overnight. High res guidance in general supports this with the 19.00z WRF DART indicating some potential redevelopment Wednesday morning. The 12z NSSL WRF and latest runs of the HRRR and RAP don`t show much. Given the placement of the shortwave (across our southwestern zones) have left PoPs in for our southeastern zones. The other concern for Wednesday morning will be the chance of fog. High res guidance has been fairly consistent in showing widespread fog development Wednesday morning as the pressure gradient remains weak allowing winds to decouple. Dewpoint depressions also approach zero across all parts of the CWA on the NAM, SREF, GFS, and ECMWF. The main concern against fog formation will be the possible development of a low ceiling deck instead. For now have more confidence in actual fog formation. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... During the day Wednesday have left a slight chance of showers with isolated thunder across the eastern zones, but taking a look at the position of the upper level shortwave it appears that most of the precip will be confined to our far eastern zones. It should be noted coverage should be sparse across our area though as the Ohio valley remains in the weak subsidence zone on the back size of the shortwave. Also on the backside of the shortwave dry mid and upper level air begins to move in from the east. During the day Wednesday 850 mb temperatures also rise to around 17 degrees C and with partly sunny skies highs will likely reach the mid 80s. Have gone ahead and raised high temperatures a bit. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Tricky forecast at the beginning of the extended. Leftover moisture associated with decaying frontal boundary is found over the region. Even though an upper ridge is trying to dominate the region, there appears that there will be enough sfc convergence that pop-up convection can`t be ruled out. Added 20 PoPs for Thursday, but it might need to be increased to chance PoPs as we get a little closer. The H5 ridge then builds in and becomes the dominant feature through the weekend and into early next week. High temperatures will be about 10 degrees above normal through the period as they push into the mid and upper 80s. Morning lows will start out 60-65 degrees, then cool a few degrees to around 60 for the latter part of the period. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... Mid level shortwave continues to slowly push east across the TAF sites this afternoon and can clearly be seen on water vapor. As the shortwave has slowly weakened this afternoon and lapse rates remain pitiful lightning has quickly decreased in coverage. Therefore have gone ahead and pulled thunder from the TAF sites even though an isolated strike can`t be ruled out. This evening the shortwave will slowly exit east with showers coming to an end from west to east. Overnight into Wednesday morning winds will quickly decouple thanks to the weak pressure gradient and with dewpoint depressions close to zero degrees fog looks likely. The main catch remains how much leftover cloud debris will be across the area. Overall have trended TAFs downward with visibilities and also brought in some cigs as well. Latest HRRR and NAM is also hinting at some MVFR/ IFR ceilings forming overnight which could delay fog formation as well. For now confidence is higher in fog formation compared to MVFR/ IFR ceiling formation. During the day Wednesday some weak shower and thunderstorm formation will be possible, but given that the TAF sites are on the back side of the shortwave have kept mention of precipitation out. OUTLOOK...No significant weather is expected at this time. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines NEAR TERM...Haines SHORT TERM...Haines LONG TERM...Sites AVIATION...Haines

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