Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 261830 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 230 PM EDT Sun Mar 26 2017 .SYNOPSIS... Showers and thunderstorms will develop today into tonight as low pressure moves to Lake Michigan. After a brief visit by high pressure and drier air early Monday, another low will bring more showers and thunderstorms Monday night and Tuesday. Dry weather can be expected Wednesday under high pressure. && .NEAR TERM /THROUGH TONIGHT/... Upper level low pressure is currently moving into western Illinois this morning with the first band of precipitation getting ready to exit the CWA. The second wave of precipitation has already formed near KCVG and is in association with another band of PV rotating around the upper level low. This afternoon forecast soundings will continue to slowly destabilize as low level cooling commences due to the approaching low along with weak surface heating. ML CAPE values on both the NAM and GFS are between 200 and 400 J/kg with MU CAPE values of 500 to 1000 J/kg. Forecast soundings show this CAPE being weak and skinny with 500 to 800mb winds between 35 to 40kts. This second round of precipitation is then forecasted to intensify this afternoon across our far eastern zones. High res models then have a third round of showers and thunderstorms forming across central Indiana this afternoon and pushing east across the area late afternoon into evening. There will be a potential for isolated hail and gusty winds in any stronger storms due to the instability mentioned above. Lapse rates in the hail growth zone do become less favorable during the afternoon into evening which would tend to limit the large hail potential. Given enough instability, moisture, lift, and flow SPC has us in a marginal risk. Prev Discussion-> Low pressure centered over Illinois will travel to Southern Lake Michigan by this evening. Moisture transport from the Gulf of Mexico ahead of this slow moving, vertically stacked system is evident on satellite. Radar shows that showers have developed and are affecting western counties. This band of showers will push across the area through today, so kept categorical pops that have been in the forecast for a few days. Instability will increase with diurnal heating. Models continue to depict marginal instability, with CAPE values reaching about 500 J/KG, enough to produce thunderstorms this afternoon. Potent mid level wind flow will aid in organization of thunderstorms, and some thunderstorms cells could approach severe limits, especially in eastern counties where better forcing and instability may be more in phase. High temperatures in the mid and upper 60s will be about 10 degrees above normal. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... Thunderstorms are forecast to linger this evening, mainly over eastern locations. Showers will be diminishing in strength and coverage later tonight as the low pressure system moves farther northeast into an upper ridge and weakens. For early Monday, a ridge of high pressure will provide a brief respite from precip chances. Showers and thunderstorms may return by Monday evening ahead of the next area of low pressure that will be moving toward the area from the west. Above normal temperature trend will continue, with highs in the mid 60s north to low 70s south. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Weakening upper level shortwave and associated surface low to track through the Ohio Valley Monday night. This feature will provide widespread showers and thunderstorms. As this progressive system shifts east pcpn will come to an end Tuesday. Temperatures will remain above normal, with Tuesday`s highs ranging from near 60 northwest to the upper 60s southeast. Surface high pressure to build across the Great Lakes at mid week. This will provide dry weather Wednesday into Thursday. Temperatures will be closer to normal, with highs on Wednesday ranging from the mid 50s northwest to the mid 60s southeast. Model solutions diverge on handling late week weather system. GFS continues to be outlier and takes the southern plains upper low into the Ohio Valley and therefore is quicker with return pcpn. The more consistent ECMWF and Canadian solutions have the closed low lifting northeast into the upper MS VLY Friday. Will continue to trend the forecast toward the ECMWF/Canadian. Will bring chance pops into the west Thursday and increase these pops to likely Thursday night into Friday, as moisture and instability increase across the region. Will mention chance pops for thunder Friday afternoon into Friday evening. Temperatures to continue a little above normal with highs from the mid/upper 50s north to lower/mid 60s south for Thursday and Friday. As this system exits the region pcpn will end Saturday. High pressure to offer dry weather through the remainder of next weekend. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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Low pressure system is currently rotating over central Illinois and slowly pushing northeast. Second band of precipitation is currently moving through ILN/ DAY with restrictions down to IFR visibilities/ MVFR ceilings possible. As this second round of precipitation passes the TAF sites ceilings and visibilities will recover to VFR. A third band of showers has formed in central Indiana this afternoon and is forecasted to push east through the TAF sites later this afternoon into evening hours. As this band pushes east forecast soundings continue to show the area destabilizing. As this occurs the amount of lightning strikes will also increase. Due to this have added a tempo group for thunder into all the TAF sites. Went ahead and used current radar trends to help with timing of tempo groups. As the line passes through the TAF sites some gusty winds and restrictions in visbilities and ceilings will be possible. As the line passes the TAF sites a brief recovery to VFR will occur with a return of MVFR ceilings possible Monday morning. The NAM is the most aggressive with the return of the MVFR Monday morning while the GFS is more optimistic. The SREF probabilities are more in between the two and have decided to trend TAFs this direction. During the day Monday any MVFR ceilings will quickly recover to VFR with another upper level low moving east across the central United States. By middle of Monday afternoon PVA and upper level divergence will be overhead meaning a return of showers and thunderstorms. For now have left mention out of TAFs as this remains near the end of the period, but future TAF packages will likely have to incorporate this. OUTLOOK...MVFR ceilings and visibilities will be possible late Monday into Tuesday morning.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines NEAR TERM...Haines SHORT TERM...Haines LONG TERM...AR AVIATION...Haines

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