550 FXUS64 KHUN 100837 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 337 AM CDT Wed Oct 10 2018 .NEAR TERM...(Today and Tonight) Issued at 336 AM CDT Wed Oct 10 2018 Hurricane Michael has strengthened to a Category 4 hurricane this morning as it nears the FL Panhandle. To the NE of this system a ridge remains situated just off the VA coast. To the west of our area a trough and surface low were ejecting N/NE out of the central plains towards the northern Great Lakes region. A cold front associated with this system is situated along the MS River Valley extending from ArkLaMiss north to the Quad Cities region. A mixture of showers and embedded thunderstorms exists along this front, which will continue to gradually push east today. The wind flow between all of these features has created a broad area of convergence from central AL all the way to eastern SC. Showers have developed as a result with a few locations across the TN Valley reporting some light rain. Adjusted pops early this morning to reflect current radar trends. By sunrise though with Hurricane Michael nearing the FL coast this axis of convergence weakens slightly and is pushed to the north of the area. At that point we'll be in a region of weak subsidence which should help to limit precip this morning. By this afternoon, as the trough and front continue to shift east, Hurricane Michael will start to be influenced by the upper winds associated with the trough and it will begin to turn NE towards inland FL/southern GA. The overall forcing with the front weakens as it starts to move across the TN Valley today but a combination of convergence and a weak deformation axis aloft should allow for an uptick in pops this afternoon. CAPE values are forecast to remain on the lower side (around 500 J/kg) due to increased cloud cover. But that will likely be enough for isolated storms to form along the front as it moves east. Latest CAM guidance is probably underdoing pops a bit and think we'll end up with a little greater coverage than advertised. So have maintained high pops this afternoon through the late evening hours. Any storms that will form would be capable of pretty heavy downpours with PWATs near climatological maximums. As we head into the overnight hours Hurricane Michael is forecast to be across southern GA and winds through the column shift to the north. This will begin to advect in cooler/drier air into the area. But with the cooler air limited to a shallow region near the surface think there will be enough lingering moisture to support continued light rain overnight. The true drier air won't arrive until closer to sunrise Thursday and have tried to show an end in pops from west to east overnight. Highs despite the clouds should be in the lower 80s today. For lows we may end up with a gradient in values with lower 60s across NW AL and closer to 70 degrees for the eastern half of the area. .SHORT TERM...(Tonight through Friday) Issued at 336 AM CDT Wed Oct 10 2018 The front mentioned above will be exiting the area to the east during the morning hours Thursday. Kept some light rain in the forecast across NE AL and southern middle TN to start Thursday but these chances will end by the noon hour. Hurricane Michael should be moving across NC/SC during the day Thursday. The pressure gradient strengthens over the area and we should end up with a breezy Thursday with gusts upwards of 20 to 25 mph possible. Going to have to watch temps/cloud cover for Thursday as think models are possibly a bit quick to scour out clouds in the wake of the front. We may end up with mostly cloudy conditions and have at least tried to show a slower clearing of clouds for Thursday. Temps may need to get bumped down a few degrees if we do end up cloudy for Thursday but we'll wait to see how the front progresses across the area before making any major changes. The strong CAA doesn't arrive until Thursday evening with temps forecast to drop between 20 to 30 degrees from Thursday morning to Friday morning. It'll be a crisp fall morning Friday with values in the mid 40s for the entire TN Valley. Fun climate fact: you've got to look back all the way to April 30th of this year for the last time we had lows in the 40s. Highs on Friday should remain below the 70 degree mark for much of the area as good CAA continues. Another climate fact: last time we had highs below 70 degrees, April 26th this year. .LONG TERM...(Friday night through Tuesday) Issued at 336 AM CDT Wed Oct 10 2018 Models differ slightly on the weekend forecast as they have a quick moving shortwave crossing the OH Valley Friday night into Saturday. The ECMWF and to some extent the NAM have precip moving across central/northern TN early Saturday morning. Even with the ample forcing associated with the system, think this is a bit overdone due to the extent of dry air across the area. So, other than some slight increase in cloud cover we should remain rain free through Saturday. Temps Friday night may end up a few degrees warmer in the mid to upper 40s. By Saturday this trough will be off to the east and winds will have shifted to the E/SE in response to another system developing over the southern Plains. Highs will be a little warmer for Saturday with values in to the lower 70s. More significant models differences exist as a trough digs S/SE into the plains and the system starts to kick east. These differences are tied to how the models handle the speed of the remnants of Hurricane Sergio in the eastern Pacific. The GFS is the fastest solution and has the system and front completely through the area by sunrise Monday. The ECMWF is much slower and phases the remnants with the trough digging into the plains. This would result in a more robust system with stronger shear and higher rain chances as a cold front moves across the area. The GFS version is so quick that the two can never phase and we end with weaker forcing along front and lower rain chances. Given these uncertainties will go with a blend of solutions with a lean more towards the ECMWF. Expect another cool down behind this system with lows back down into the 40s and highs in the 60s. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1220 AM CDT Wed Oct 10 2018 An MVFR deck between 1,500-2,500ft is pushing N/NW towards the TN Valley from central GA. Light rain and an even lower IFR deck exists over central GA and could make it into the area around sunrise. But confidence is low is the IFR cigs making into HSV/MSL terminals. Winds could be gusty at times out of the E/SE with gusts up to 20kts possible through the early morning hours. Winds relax a bit during the day with speeds holding around 10kts. Should see some improvement in cigs after sunrise as well to MVFR/VFR. SHRA and a return of MVFR to possibly IFR cigs are then possible towards the end of the current TAF period. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...Stumpf SHORT TERM...Stumpf LONG TERM...Stumpf AVIATION...Stumpf For more information please visit our website at weather.gov/huntsville.