053 FXUS64 KBMX 240014 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 714 PM CDT Fri Oct 23 2020 .UPDATE... For 00Z Aviation. && .SHORT TERM... /Updated at 1151 AM CDT Fri Oct 23 2020/ The slow moving frontal boundary will finally get the push forward through the overnight hours bringing likely rain chances to much of Central Alabama. However, the rain totals look meager at best with qpf values around a quarter-inch or so. Showers should linger through the day tomorrow, mainly east where they will be slow to exit into Georgia. 17/KLAWS .LONG TERM... /Updated at 120 PM CDT Fri Oct 23 2020/ Saturday Night through Thursday. Features. In the long term forecast period, the upper level flow looks to be overall zonal with relatively low amplitude features progressing eastward with time. The Polar Jet will sink southward Sunday into Monday across the Intermountain West while the Subtropical Jet persists in a southwest to northeast orientation. Most global modeling depicts the jets trying to phase late Monday into Tuesday over the Four Corners States as the Polar Jet amplifies further to the south. A closed low looks to develop aloft and move into the Central Plains by Thursday before gradually opening up into a trough that moves over the Mid South toward the Ohio River Valley region on Thursday into Friday. Zonal flow in the mid levels will persist from Sunday through Monday with a gradual transition to a more southwesterly flow over the area. Mid-level ridging is progged to amplify over the Florida Peninsula while a sharp positively-tilted longwave trough develops from the High Plains southwest into the Desert Southwest. Increasing uncertainty in the ridge position, whether it be to our southeast or further east over the Southwest Atlantic Basin, will affect the amplitude of the closed low as it cuts off from the main flow and moves over Western Texas by Wednesday. Global modeling differences only increase with time regarding the position and phase of the closed low as it moves across the Mid South and into the Tennessee Valley region from the Friday through Saturday time frame. Forecast. The cold front that moves through much of the area Saturday will be slow to push out of the area late Saturday night and into Sunday and carried low-end PoPs across our east and southeast counties for this time frame. Expect dry conditions to prevail late Sunday followed by more clouds with low-end PoPs north and northwest Monday with isolated PoPs all but east on Tuesday. Expect a gradual increase in moisture in the low levels late Tuesday into Wednesday. Model families differ in moisture advection with some tapping tropical moisture in the Caribbean Sea as a potential source. Differences in the moisture gradient from Wednesday into Thursday further reduce confidence in timing/extent of shower and thunderstorm potential. Generally, period of greatest moisture availability over the area appears to be in the late Wednesday through Thursday time frame followed by drier air overspreading the area late Thursday into Friday. Examining shear profiles in the lower levels, there is disagreement on timing, placement and intensity but overall, a Low-Level Jet is depicted in the late Wednesday into Thursday time frame with much of the forecast area potentially experiencing this fast flow off the surface. The lower-level low track generally is depicted to be near or just north of the Interstate 40 corridor. Looking at the layer column precipitable water, the highest values over our area just exceed 2 inches in the late Wednesday through late Thursday time frame. Forecast instability values increase during the day Wednesday generally across the southern half of the area, decreasing overnight and re-emerging across the southeastern and eastern counties during the day on Thursday, followed by decreasing values late Thursday into early on Friday. Will cap PoPs below 50 percent from the Wednesday through Friday time frame given the persistent uncertainties with timing and position of features. An important question is the potential of tropical moisture over the Western Caribbean Sea advecting north and being absorbed into the approaching trough in the late week time frame. The amount of moisture along with cloud and precipitation patterns that result will affect instability distribution and this will be crucial for assessing thunderstorm potential. At this time with fairly marginal instability and decent low-level shear a few stronger storms can not be ruled out with this next storm system. The resolution of further details will depend upon decreased spread and improved run-to-run continuity on feature placement and depiction. 05 && .AVIATION... 00Z TAF Discussion. We currently do not have any convection near any of the TAF sites at this time. There is an area to the south of TOI drifting northward. Will monitor to see if its progress warrants adding to the TAF. Otherwise, activity will move into C AL overnight from the northwest ahead of a front. MVFR cigs will initially move in as convection increases in the wee hours before dawn. After daybreak, some IFR will be in the mix as well. No strong winds are expected overall with this front as it should weaken and stall across S AL. However, some reduced vsbys are possible with the showers. TS probability is not zero, but low and will not mention in TAFs at this time. Note: Please disregard TAFs with the time stamp of 232322z. A glitch occurred causing old TAFs to be transmitted. The correct TAFs have a timestamp of 232349z after correct ones could be transmitted. 08 && .FIRE WEATHER... Moisture continues to increase ahead of a cold front that will advance eastward toward the area tonight and Saturday with scattered showers and a few thunderstorms. Dry weather returns from northwest to southeast across the area from late Saturday through Sunday with fairly dry conditions across much of the forecast area through Tuesday. 05 && .PRELIMINARY POINT TEMPS/POPS... Gadsden 63 77 59 78 60 / 60 60 30 10 0 Anniston 64 78 62 79 62 / 50 60 30 10 0 Birmingham 65 77 60 79 62 / 60 40 20 10 0 Tuscaloosa 65 77 60 80 62 / 70 40 10 10 0 Calera 65 77 61 79 62 / 60 50 20 10 0 Auburn 65 78 63 79 63 / 30 60 40 10 0 Montgomery 67 82 64 83 64 / 50 60 30 10 0 Troy 67 81 64 82 64 / 40 60 30 10 0 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$