####018009108#### FXUS62 KFFC 171322 AAA AFDFFC Area Forecast Discussion...UPDATED National Weather Service Peachtree City GA 922 AM EDT Sat May 17 2025 ...Morning Update... .UPDATE... Issued at 905 AM EDT Sat May 17 2025 A line of thunderstorms has pushed through north Georgia this morning, with a few embedded strong storms producing straight- line winds, small hail, and frequent lightning. At the time of this writing, the line has largely weakened with the exception of a bowing segment south of I-20 that is surging due east over the I-75 corridor. The larger scale line of storms is slowly sinking southeastward. An overcast sky and a capping inversion should -- for the most part -- keep deep convection at bay through the morning hours. Still, gusty winds (up to around 40 mph) and occasional CG lightning will be possible as the line marches into central Georgia. Martin && .SHORT TERM... (Today through Sunday) Issued at 322 AM EDT Sat May 17 2025 Key Messages: - A line of thunderstorms will advance through far north Georgia during the early morning hours ahead of a cold front. A few storms within this line could become severe. - Scattered thunderstorms are expected this afternoon and evening in portions of central Georgia in a warm/humid environment and along the stalled frontal boundary. - Showers and thunderstorms return on Sunday, with isolated strong to severe storms possible. The possibility of an MCS entering the area will need to be monitored. As the morning begins, a line of thunderstorms is advancing southward through middle Tennessee ahead of a cold front. The progression of the line has slowed a little bit compared to the previous forecast, though a few isolated storms have begun to enter the far northwestern corner of the forecast area. By the time storm arrive in the far northern tier by around 4 AM EDT, SBCAPE and MUCAPE values around 1000-1500 J/kg will still be present. Furthermore, 0-1 km shear ahead of the cold front will range from 30- 35 kts and 0-1 km storm relative helicity values will range from 150 to as high as 250 m2/s2. Considering these factors, isolated storms ahead of the line may become supercellular, capable of producing a brief tornado and strong wind gusts. It will also be likely to see a few stronger storms embedded within the greater line, with bowing segments capable of producing damaging wind gusts and brief tornadoes, as well. By sunrise, the line is anticipated to be roughly parallel to the north ATL metro. At this point, the cold front will become more elongated from west to east, at which point it will begin to stall and storms will steadily weaken. Showers and thunderstorms will work their way southward through the metro area during the early and mid morning hours. By the early afternoon, the front is expected to stall in an area between the metro area and a line from Columbus to Macon. The passage of the cold front will only have a minor impact on high temperatures this afternoon. Highs in north Georgia are forecast to rise into the mid to upper 80s in all but the far northeastern mountains (which will be slightly cooler). To the south of the front, highs in central Georgia will rise into the low to mid 90s once again today. These highs will range from about 5-9 degrees above daily averages. The frontal boundary is expected to provide a focus for convective development during the afternoon and evening hours. While may hi-res solutions keep convective development sparse in the vicinity of the front, this very well may be underdone given strong destabilization to the south of the front. SBCAPE values between 2000-3000 J/kg will still allow for the development of isolated to scattered thunderstorms in the afternoon hours. With deep layer bulk shear of 45-55 kts, some of the storms that develop will have the potential to become supercellular and produce damaging wind gusts and hail. Because of this, the SPC has maintained a Day 1 Marginal Risk (level 1 of 5) for severe weather. Precipitation is expected to gradually come to an end in the hours following sunset with the loss of diurnal heating. The frontal boundary will still be in place across central Georgia on Sunday morning. At this time, a 500 mb ridge will advance across the Great Plains. A quickly moving shortwave will move across the Southeast on the eastern side of the ridge pattern, where it will then overrun the front on Sunday morning into the afternoon. Chances for showers and thunderstorms will increase accordingly, with scattered showers and a few isolated thunderstorms during the morning and more numerous showers and thunderstorms in the afternoon. The greatest chances for showers and thunderstorms are forecast to be in the far west/northwest portions of the forecast area where isentropic lift will be most aligned with the stalled surface boundary. Forcing along the front will be weak at this point, but SBCAPE values ranging from around 1000 J/kg in far north Georgia to 2000 J/kg in south-central Georgia and a moderately sheared environment will allow for isolated thunderstorms to become strong to severe in the afternoon and capable of producing strong wind gusts. Another variable that will warrant monitoring as we get closer in time is the formation and evolution of any MCSs that develop upstream overnight into Sunday morning. An MCS entering central Georgia during the afternoon could find itself in a highly favorable environment for downstream growth and propagation, which would lead to a more widespread wind threat. Ample uncertainty remains in this scenario at this time. King && .LONG TERM... (Sunday night through Friday) Issued at 322 AM EDT Sat May 17 2025 Key Messages: - Warm to hot. Highs in the upper 80s and low 90s, with a potential cool down around mid-week. - Small chance of severe weather Sunday afternoon. Main hazard is damaging winds. There is a marginal (level 1 of 5) risk of severe. Risk tappers off into the evening. Thunderstorms may continue into the evening hours on Sunday with whatever instability may remain through central Georgia. Entering the overnight hours, the subtropical ridge rebounds northward as the upper level shortwave moves out of the area. Thunderstorm activity should shift northward through this timeframe, though overall activity will be significantly reduced. With the terminus of the subtropical thermal ridge across north Georgia, diurnal thunderstorms activity can be expected each afternoon Mon and Tuesday ahead of our next system. As we get into the Wednesday timeframe, a more robust upper level trough will descend into the area bringing a cold front and more widespread showers and thunderstorms. Currently limited to no severe weather is anticipated with this due to the strength of the thermal ridge, however will definitely keep an eye on it as we get into the near term. Temperatures behind the front will be cool for this time of year with highs in the 70s and (hopefully) drier conditions. SM && .AVIATION... (12Z TAFS) Issued at 707 AM EDT Sat May 17 2025 A line of SHRA/TSRA is advancing southeastward through north Georgia and approaching the northern metro area. Prevailing -SHRA, along with a TEMPO for TSRA, is being carried at ATL from 12-15Z this morning. MVFR ceilings are also expected in the vicinity of the line of precip through 17Z at ATL. Ceilings will then improve to VFR and scatter out during the late afternoon. As the frontal boundary stalls in central Georgia, scattered TSRA will be possible near CSG/MCN this afternoon, warranting a TEMPO from 18-22Z. Winds through the daytime will be SW to W, at 8-12 kts and occasional gusts up to 18-22 kts. Winds will diminish after sunset. MVFR level clouds will be possible once again in the early morning on Sunday, most likely in west-central Georgia. //ATL Confidence...12Z Update... Medium confidence on ceiling trends. High confidence on all other elements. King && .PRELIMINARY POINT TEMPS/POPS... Athens 86 66 85 65 / 50 0 30 10 Atlanta 87 68 85 68 / 70 10 50 10 Blairsville 81 59 79 59 / 60 10 30 20 Cartersville 87 64 85 65 / 70 10 50 20 Columbus 89 69 90 68 / 40 10 40 0 Gainesville 85 66 84 66 / 70 0 40 10 Macon 90 68 90 68 / 50 10 40 0 Rome 88 64 85 65 / 60 10 50 20 Peachtree City 87 66 87 66 / 60 10 50 10 Vidalia 92 72 91 70 / 30 20 30 10 && .FFC WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...King LONG TERM....SM AVIATION...King ####018006125#### FXUS63 KAPX 171322 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 922 AM EDT Sat May 17 2025 .KEY MESSAGES... - Much cooler with more showers today into tonight. - Quiet and dry weather through the first half of the week with fire weather concerns this Monday. Otherwise precip chances return later Wednesday, Thursday, and Friday. && .UPDATE... Issued at 922 AM EDT Sat May 17 2025 Inherited forecast remains on track. Mammoth upper level low pressure has finally made it into the area, and the warm, summer- like temperatures and thunderstorms are now just a distant memory for folks up here in APX land. Cold air advection well underway with temperatures likely rising minimally from their current standings, into the 50s, with some areas near Lake Huron in northeast lower making a run at 60. Lack of pinched pressure gradient due to the center of the low being right over our heads will lead to lesser wind potential than those to the south and west... though we will still contend with some breezy cyclonic W to SW flow, with some gusts as high as 25 mph, which will add an element of chill to the air. Well defined moisture pool wrapped around the system will keep us in generally mostly cloudy to overcast skies given our position in the immediate vicinity of the surface low. Some breaks in the clouds evident across NE Wisconsin will make a run at the southern CWA, which could lead to some peeks of sun later this morning into the afternoon in those locales. Closer to home, synoptic precip shield will continue to slowly pinwheel across the region this morning, with activity becoming a bit more scattered in the afternoon. With moist adiabatic lapse rates / well saturated airmass in place, minimal diurnal heating will be required to force some shallow convective showers later today. No thunder is expected at this juncture. && .SHORT TERM /THROUGH TONIGHT/... Issued at 306 AM EDT Sat May 17 2025 Pattern Synopsis/Forecast: All attention early this morning directed at deep and vertically stacked low pressure working east across northern Wisconsin/western upper Michigan. System attendant cold front in the process of sweeping across the Northwoods, drumming up some shower with embedded thunderstorms in the process. Some gusty winds and small hail earlier with some of this activity, but nothing too noteworthy. Upstream low pressure will continue to work steadily east directly across our area today, reaching vicinity New England Sunday morning. This will bring much cooler and occassionally damp weather to the Great Lakes through tonight. Primary Forecast Concerns: Temperature trends and addressing shower evolution through tonight. Details: Big story today will be the arrival of much cooler temperatures as cold air advection intensifies on backside of passing low. Will definitely feel more like April then the middle of May (especially after the recent very warm temperatures), with highs today mostly ranging from the middle 50s to lower 60s. Southwest to west winds will steadily increase as well today, adding a bit more chill to the air. Pockets of enhanced moisture and forcing wrapping around parent low...along with some weak diurnal support...will result in scattered mostly light showers at times today. Vertical moisture profiles begin to thin with time tonight as system departs to our east. May see some lingering light showers/areas of drizzle within a still relatively moisture rich low level environment and upslope enhancement via gusty northwest winds. Cooling trend continues, with lows tonight down into the lower and middle 40s. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 306 AM EDT Sat May 17 2025 Pattern Synopsis/Forecast: Midlevel pattern begins to shift at the start of the long term from active weather to a more dry pattern through the first half of the week. Surface high pressure will build this Sunday and Monday. Pressure graident force winds from the departing/downstream low will pull a chilly dry air mass from the north. Temperatures this Sunday remain much cooler than normal for mid May with highs remaining in the 50s for most locations across the CWA. Monday remains pretty much the same except subsidence aloft will begin to really dry out conditions and resulting in very low RHs. Fire weather remains a concern as efficient mixing in the low levels could keep RHs well below critical thresholds. Luckily; winds remain calm and only gusting up to 15-20mph which keeps us out of headlines for now, but elevated fire weather conditions are still expected even with these early spring-like temps. Closed mid-level low pressure currently over the Pacific Northwest will begin to advect across the country and stalling out over the Upper Great Lakes this Wednesday through the rest of the week. This disheveled set up will remain disorganized but with enough energy and moisture to deliver rounds of scattered showers. Not a lot of QPF this system with most showers only having enough water to wet pavement, but deary and cool conditions will finish off the week making the second half of May feeling more like April for Northern Michigan. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 532 AM EDT Sat May 17 2025 Widespread MVFR to IFR producing low clouds, mist, and showers expected across all taf locations today. Some slow improvement tonight as showers dissipate. West to southwest winds become gusty today, with winds veering northwest and remaining gusty tonight. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for LHZ349. Small Craft Advisory until 2 AM EDT Sunday for LMZ323-341-342- 344>346. && $$ UPDATE...HAD SHORT TERM...MSB LONG TERM...SJC AVIATION...MSB