FXUS64 KJAN 040623 AFDJAN Area Forecast Discussion National Weather Service Jackson MS 1223 AM CST Wed Dec 4 2024 ...New AVIATION... .MESOSCALE UPDATE... Issued at 946 PM CST Tue Dec 3 2024 Dry air associated with cold surface high pressure system remains in place over the Southeastern U.S. tonight. Core of the 1035mb surface high is centered over the Southern Appalachians this evening and continuing to push eastward. Flow aloft will gradually turn out of the east and south heading into tomorrow as the high departs and as a surface low spins up along the TX Gulf Coast. Our region will be positioned favorably beneath the right entrance region of an upper-level jet streak through the day, aiding in warm moist advection east of the surface low and over the colder surface air mass. Isentropic ascent will progressively saturate upper-levels and mid-levels with light to moderate precip becoming more likely by the evening hours tomorrow. Where precip begins, wetbulbing should limit temps to the mid and upper 40s. Otherwise, temps should warm into the mid and upper 50s most locations before precip arrives. The Pine Belt in southeast MS has the best chances to break the 60 degree mark tomorrow afternoon. /NF/ && .DISCUSSION... Issued at 223 PM CST Tue Dec 3 2024 Through Wednesday... The short term period (through Wednesday morning) will start fairly benign as high pressure continues to be the driving regime for the Jackson CWA. Cold air advection maintains behind the front that migrated through the area late last night. As such, the main point of interest will be our overnight lows tonight which will bottom out below 30F for most forecast zones, with few counties/parishes to the far southwest breaking just above freezing. Wednesday daytime highs will briefly rebound into the upper 50s and low 60s across the CWA, with southerly flow returning; due to the high that is currently located over northwestern Arkansas shifting off to our west by mid morning tomorrow. Through Wednesday Night... The overall synoptic pattern at all levels will be dominated by high heights/ridging, that being said there is a low expected to pivot around the ridging and break into the area Wednesday night. This surface based low is set to develop somewhere near Brownsville today spinning off of an inverted trough over the southern Gulf. This low, while not dynamically supported will pinwheel around the overall anticyclonic pattern transiting along the Gulf Coast. Wednesday night the low will begin to push into the area from the west which will provide a moderate amount of vertical ascent; coinciding with overrunning conditions that will be occurring independent of this cyclone. These two primary lifting factors together will make way for precipitation chances to steadily increase Wednesday night building in from the west, and progressing over the entire CWA. Precipitation will not clear out of the area until yet another cold front passes through the area Thursday./OAJ/ Wednesday night through mid next week... Rain Wednesday night into early Thursday is swept out Thursday afternoon as yet another reinforcing arctic front pushes across the area Thursday. The Canadian high in its wake will reestablish cold, dry, polar air over the region. Temperatures will fall to the 20s pretty much areawide Thursday night. Highs on Friday struggle to exceed 50 degrees for much of the area, about 15 degrees below seasonal norms. Beyond this point, there is some timing differences in the guidance regarding the synoptic evolution, with the GFS being the faster solution. With this, GFS seems to be an outlier in introducing rain chances as early as Saturday. That said, all guidance has a solid signal for the Sunday to Monday timeframe, with the lead shortwave progged to eject around Monday. Given the preceding dry airmass, it is questionable how quickly we can recover moisture. Instability is quite weak with this first wave, but there could be enough to support some elevated thunderstorms. Of greater focus is potential for some sort of flood threat, with focused moisture transport with PWAT around 1.5 inches amid boundary parallel flow supporting heavy rain. Guidance consistently shows 2 to 3 inches of rain, potentially higher with several waves next week. Convective potential is uncertain with lack of instability and if rain falls over time, flood threat is diminished. Considering the uncertainties, expect forecast adjustments as necessary./SAS/ && .AVIATION... (06Z TAFS) Issued at 1217 AM CST Wed Dec 4 2024 VFR conditions with initially light and variable winds to start the TAF period at all sites. Winds will turn out of the south by 12Z-15Z today. Increasing cloud cover and rain chances from west to east will eventually impact all sites by this evening with IFR/MVFR category ceilings/vsby becoming widespread. /NF/EC/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 49 55 27 49 / 100 20 0 0 Meridian 48 54 25 48 / 90 20 0 0 Vicksburg 47 54 25 48 / 100 10 0 0 Hattiesburg 53 60 30 50 / 90 60 0 0 Natchez 51 56 29 49 / 100 20 0 0 Greenville 40 47 24 43 / 80 0 0 0 Greenwood 41 49 24 47 / 90 0 0 0 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ NF/OAJ/EC