975 FXUS64 KBMX 251740 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 1140 AM CST Mon Nov 25 2019 .UPDATE... For 18Z Aviation. && .SHORT TERM... /Updated at 0358 AM CST Mon Nov 25 2019/ Through Tonight. High pressure will be in control of the area today, with plenty of sun. Look for highs to be in the 60s. Tonight the high pressure will slide to our east and a southerly flow will increase overnight. Moisture will quickly work into the area and we will see an increase in clouds after 3 am. Look for temperatures in the west to hold steady after this or even rise a degree or two. Look for lows to be in the 30s east to 40s west. At this point it appears any rain will hold off until after sunrise Tuesday. More on that in the extended. 16 .LONG TERM... /Updated at 0358 AM CST Mon Nov 25 2019/ Tuesday through Wednesday: An upper low within a low-amplitude trough will eject out of mean troughing over the western CONUS, lifting from Colorado Tuesday morning to the Great Lakes by midday Wednesday. It will be a very dynamic system with a 988mb surface low, 180+ kt upper- level jet streak, 130+ kt mid-level jet streak, and 55-60kt LLJ. An effective 850mb warm front will push northeastward across the area Tuesday morning. The associated isentropic lift/low-level moisture surge will result in the potential for isolated to scattered light showers/drizzle patches to lift northeastward as early as Tuesday morning. Through the afternoon hours weak embedded shortwaves in the strengthening/moistening southwest flow aloft will result in continued light rain chances especially in the northwest counties where 1000-500mb mean RH values will approach 90%. The warming trend will continue but will be muted across the north due to the increased cloud cover, while highs in the south should reach the low 70s with a few more breaks in the clouds. The instability axis/axis of higher dew point axis should remain over the ArkLaMiss through the daytime hours. Another wave in the southwest flow aloft should focus continued higher rain chances across the northwest counties Tuesday evening. Weak elevated instability may develop as early as Tuesday evening in the northwest counties as mid-level lapse rates begin to steepen so isolated thunder may be possible. The cold front approaches the northwest counties very late Tuesday night/early Wednesday morning with an associated area of showers/isolated thunderstorms. Severe storms are still not expected at this time due to a lack of appreciable surface-based instability and height rises associated with a strengthening subtropical ridge centered near Cuba. But a stronger storm can't be ruled out given the strong shear and some weak elevated MUCAPE. Minor flooding of poor drainage areas may be possible with PWATs of 1.8-1.9 inches, but lack of instability/forcing should prevent a threat of flash flooding. The area of showers will begin to weaken and dissipate during the afternoon hours across the southern counties as ridging continues to strengthen and low-level flow continues to veer. Thursday through Sunday: A very amplified pattern sets up for Thanksgiving and the day after as an anomalous subtropical ridge over the Gulf strengthens to around 594 decameters, with a ridge axis extending northward over the eastern CONUS. Meanwhile a deep longwave trough will be present over the western CONUS. The front will stall out at the surface near the Gulf Coast, before beginning to lift northward on Friday. The remnants of the cutoff low currently well west of Baja will eject across the central CONUS Thursday and Friday, causing the front in the 925-700mb layer to lift northward. Associated mid-level moist isentropic lift could cause some light rain to graze our northern counties during this time, but the bulk of the rain will remain northwest of the area. A strong speed max rounding the base of the western CONUS trough will result in the formation of an upper low in the vicinity of western Nebraska by Saturday, with the overall trough evolving to a somewhat lesser amplitude trough as it pushes eastward. Models appear to be coming into better agreement on the timing of the cold front associated with this system moving through Saturday night. It appears that there will be a bit more moisture return/instability with this system than previous systems, along with some steeper mid-level lapse rates, though as of tonight CAPE values are forecast to remain less than 750 J/kg which is a downward trend from previous runs. Will need to keep an eye on severe weather potential for this system given the strong shear, but confidence is too low to mention in the HWO this far out given a lack of run to run consistency on timing and instability, and uncertainty regarding how quickly the low-level flow will veer out as the system will be occluding. A cooler pattern looks to return for the beginning of next week. 32/Davis && .AVIATION... 18Z TAF Discussion. VFR conditions through this afternoon and evening, with only a few high clouds moving across the area. Winds could be variable at times as we remain under the influence of surface high pressure this afternoon. Otherwise, a general southerly direction to the winds with speeds below 6kts. Tonight, moisture and lift will increase from the south, and low cigs are expected to spread northward. There is some uncertainty on extent of low cigs, whether a MVFR deck remains scattered or quickly fills in across the area from south to north. Will show a trend of lower cigs spreading across the area late tonight through Tuesday morning for now. Winds will back slightly to the SSE to SE early tomorrow morning, with speeds at 6-7kts. 14 && .FIRE WEATHER... Dry conditions will continue today, with a warming trend for through Tuesday. A cold front will bring another round of widespread rain chances late Tuesday afternoon through Wednesday. Critical fire weather conditions are not expected. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 62 35 66 55 66 / 0 0 20 80 60 Anniston 63 38 68 56 68 / 0 0 10 70 70 Birmingham 63 41 68 59 66 / 0 0 30 80 60 Tuscaloosa 65 43 69 61 67 / 0 0 40 80 60 Calera 64 41 69 59 68 / 0 0 20 80 70 Auburn 62 39 67 56 69 / 0 0 0 20 60 Montgomery 66 42 74 60 74 / 0 0 10 20 70 Troy 65 43 73 58 75 / 0 0 0 10 60 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$