259 FXUS64 KHUN 101157 AAA AFDHUN Area Forecast Discussion...UPDATED National Weather Service Huntsville AL 557 AM CST Sun Feb 10 2019 .UPDATE... For 12Z TAFS. && .NEAR TERM...(Today) Issued at 320 AM CST Sun Feb 10 2019 Light showers continue to overspread the region early this morning as a weak front lifts north across the region. This boundary will slowly move through the Tennessee Valley this morning, serving as a focus for these scattered showers. A glance at soundings and obs suggests that dry air will likely erode/evaporate some of the precipitation initially. Easterly flow has dry air near the surface, and thus dewpoint depressions of 20+ degrees in areas west of I-65. However, a gradual moistening of the boundary layer will occur between 09-12z (especially west of I-65) to support some light rainfall accumulations. The main window for accumulating precipitation will be this morning as the boundary should lift into Tennessee by early this afternoon. Thus, we'll see a potentially significant decrease in coverage between 15-18z as this boundary moves north, and a mainly dry afternoon. PoPs will need to be watched today, as the latest trends (supported by the CAMs) indicate this afternoon will be fairly dry -- with more isolated to perhaps widely scattered activity in the north being the best representation of the conditions at hand. Winds will veer to a more southerly direction, however, and we'll begin to see some deeper moisture from the Gulf of Mexico start to filter into the area. Heating will be quite limited despite this southerly flow, thanks to a prevailing broken to overcast cloud deck. Should we see a few breaks in the clouds, it won't take much to jump temperatures into the low to potentially mid 50s for highs. Further east along the terrain Cumberland Plateau, upper 40s to around 50 degrees are a safer bet. .SHORT TERM...(Tonight through Tuesday) Issued at 320 AM CST Sun Feb 10 2019 With the aforementioned boundary displaced to the north and west across Tennessee and Arkansas, there will be very limited forcing to generate precipitation tonight. SSE to southerly winds will maintain a strong fetch of the Gulf of Mexico, and dewpoints will respond by rising into the mid to upper 40s. Thus, boundary layer moisture will recover quickly, so any passing ripple in the mean flow will likely generate an isolated to widely scattered rain shower, albeit light. As one would expect, the best chances for precipitation will be across the northern zones (far northwest Alabama and Southern Middle Tennessee) closest the boundary, and have oriented PoPs and QPF accordingly. The main story tonight will be the mild temperatures as cloud cover and the breezy, moist southerly flow will prevent temperatures from dropping more than a few degrees from daytime highs. Thus, a fairly steady temperature in the upper 40s is expected in most areas. Attention quickly turns to the strong storm system develop across the Plains that will eventually shift into the Mississippi Valley and the Deep South, bringing us a much more meaningful shot of rainfall early this week. With the boundary still stalled to the north of the region, Monday morning will be fairly dry. Soundings indicate an inversion will be present and we'll likely be capped through the early to mid afternoon. However, the increasing wind sheer and strong southerly flow will promote good warming in the boundary layer. Combined with some breaks in the clouds that should form in the afternoon, temperatures will likely surge into the low to perhaps mid 60s (if we can remain dry). With dewpoints in the mid 50s, it will feel fairly humid outside. Thanks to the heating taking place, we'll likely generate some very modest elevated instability by late Monday afternoon into the evening hours. As the upper-trough shifts from the Rockies onto the Southern Plains Monday afternoon, a surface cold front will then move into the mid/lower Mississippi Valley. Ahead of this boundary, a 50-60 kt LLJ will develop across the Mississippi/Alabama Gulf Coast, and lift into North Alabama by Monday evening. This feature will likely trigger some scattered to numerous rain showers, and perhaps a isolated rumble of thunder. This wave of convection will likely move across the region during a 00-06z timeframe, just of ahead of the main cold front that will be moving into West Tennessee and North Mississippi. The latest model guidance has slowed down this feature ever so slightly, but feel confident that we'll likely see a line of showers and isolated thunderstorms moving into far Northwest Alabama between 09-12z early Tuesday morning along this front. Wind shear profiles are quite strong, so do expect this activity to have some organized structure to it. However, instability (per sounding profiles) continue to indicate very meager CAPE values, so the potential for any strong storms seems quite low at this time. Still, given the strong shear this activity will need to be watched. Latest timing of the front will bring a bulk of the heaviest precipitation through the area during a 09-15z timeframe, and tapering off from west to east after 15-18z. With the deep moisture in place, moderate to heavy downpours will be the main impact, and most areas will likely pick up 1 to 1.5 inches of rainfall. As one would expect with a February frontal system, cold air advection will occur in wake of the cold front and temperatures will likely fall from the 60s early in the morning into the 50s throughout the afternoon. Would also expect to see a mostly sunny sky late in the day as dry air will quickly scour out any lingering post frontal cloud cover. The strong pressure gradient will help to create some breezy west to northwest winds behind this boundary, reinforcing a cooler, drier air mass heading into Tuesday night. .LONG TERM...(Tuesday night through Saturday) Issued at 320 AM CST Sun Feb 10 2019 Tuesday night kicks off the extended with the cold front out of the forecast area and cooler, drier air filtering in behind it. Cloud cover becoming mostly clear will help temps dip into the lower 30s. A sfc high will build in overnight and center across the region on Wednesday keeping conditions dry and allowing for plentiful sunshine with daytime highs reaching the mid 50s. As the sfc high shifts eastward overnight, southerly winds will return and cloud cover will filter back in. Unsettled conditions will return through the end of the week as another system aims for the region. There is still a fair amount of uncertainty with this system due to model differences between the upper low track and strength which provides different solutions for the sfc low tracks and arrival timing of the cold front. A trough will swing into the Plains by Thursday night, developing a sfc low in the Southern Plains. From here on out is where models start to part ways, so stayed close to guidance through the forecast package. The GFS has a deeper upper level low that is now suggested to become more closed off like the ECMWF but does not phase with the northern stream like the ECMWF. The GFS and Canadian still favor for upper level and sfc low lifting into the Great Lakes compared to the ECMWF that wants to keep things sliding into the OH Valley. Showers ahead of the cold front will start to move in Thursday afternoon, increasing in coverage overnight with a few thunderstorms possible Friday morning into early afternoon. Only included a slight chance of thunderstorms at this time as models do suggest a good amount of shear with some instability, but the GFS holds onto a cap ~850-700mb longer Friday morning. Precip will quickly taper off with the passage of the cold front with dry conditions by Friday evening. Timing may have to be adjusted with additional forecast packages as the Canadian and ECMWF are slower solutions that keep precip in a little bit longer than the GFS. Daytime highs will be around 60 degrees on Thursday and Friday with cooler temps felt by Friday night as temps fall into the lower 30s. Saturday will be dry with more seasonable temps with highs around 50 degrees and lows reaching the 30s. && .AVIATION...(For the 12Z TAFS through 12Z Monday morning) Issued at 557 AM CST Sun Feb 10 2019 VFR conditions are prevailing at both terminals early this morning. Light rain has overspread the region as a front lifts into the TN Valley, but with ceilings around 10 kft, most of this precipitation is evaporating before it reaches the ground. The front will lift north of the area by 15-18z, and the ceilings will fall quickly to low-end VFR to MVFR levels through the remainder of the day. Later tonight, localized IFR conditions will be possible, with ceilings of 1-2 kft (and at times below 1 kft). Winds will remain quite breezy and out of the SE between 10-15 kts for most of the period. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...AMP.24 SHORT TERM...AMP.24 LONG TERM...JMS AVIATION...AMP.24 For more information please visit our website at weather.gov/huntsville.