695 FXUS64 KJAN 071146 AFDJAN Area Forecast Discussion National Weather Service Jackson MS 646 AM CDT Fri Oct 7 2022 ...New AVIATION... .DISCUSSION... Issued at 352 AM CDT Fri Oct 7 2022 Today & tonight... Today: Shortwave ridging is situated over central-W TX with more stout upper low cutoff over the Desert SW & Baja Peninsula. Troughing is digging through the Great Lakes/Upper MS Valley, which will aid in a more significant frontal passage. Nearly 1040mb sfc high is situated over N Plains & the pressure gradient in the wake of the front today will help increase gradient winds across the region. Persistence fcst for highs is expected, with highs above climo in the mid-upper 80s. Isentropic ascent ahead of the cutoff low will keep some mid-high clouds around, which may inhibit some warmth. However, clouds should be thin enough to provide sufficient insolation to heat up. Main concerns will be the fire danger potential. With increased gradient winds & sufficient mixing/warmth, aftn humidity levels could bottom out near critical levels below 30%. With gradient winds up to 10-15mph possible, increased fire danger is expected. High KDBI & dry fuels coupled with gradient winds have prompted an increase to an "Elevated" for fire danger in HWO from along & NW of a line from Grenada-Yazoo City-Vicksburg, MS to Winnsboro, LA. This area has continually overachieved on mixing/low humidity & more recently on the winds. "Limited" area remains mostly the same but a small expansion in the SW along the MS River. This threat will continue into the weekend. Tonight: As trough swings into the Ohio Valley-NE, strong +1030mb sfc high pressure ridge will build into the central Plains to Mid MS Valley. Nearly 4 mb gradient will support winds remaining up overnight. This will keep lows only falling near climo in the low 50s in the Hwy 82 corridor to mid-upper 50s to the S. Broad isentropic ascent will keep some mid-high level cloudiness around overnight. /DC/ Saturday through next week... An upper shortwave responsible for pushing a dry cold front south through the area Friday night into Saturday morning will be moving east into the Mid-Atlantic with zonal upper flow and a much drier surface airmass left in its wake. We will notice much drier air through the day Saturday with highs in the lower 80s F south of I-20 and mid/upper 70s F north. This will allow relative humidity to fall into the 25-35% range in the north and west with gusty winds. For this reason, an elevated risk for fire weather was introduced into the Hazardous Weather Outlook (HWO) for Saturday, a continuation of the short term upward adjustment in risk outlook from today. Winds diminish into early Sunday morning with effective radiational cooling within the dry airmass under mostly clear skies. Overnight lows likely fall to near 50 along I-20 and 40s F to the north. Temperatures in the lower 50s are expected for the southern half of the area. Sunday afternoon will remain very dry under full sun and highs will climb into the mid/upper 70s east of I-20. Near and west of the Mississippi River, temperatures likely rise to near near 80 F. Regarding fire weather concerns, Sunday remains very dry and despite the somewhat lower winds, the additional drying will require the continuation of the elevated risk for fire weather in the Hazardous Weather Outlook (HWO) on Sunday as well for northern and western areas. Beyond Sunday, high pressure will remain in control with highs in the 80s F and lows mostly in the 50s F expected until midweek. Winds will begin to shift to southerly Wednesday into Thursday and this will allow some moisture recovery to be more apparent. Rain chances return Wednesday evening and especially Thursday as a stout upper shortwave trough rounds the base of a high amplitude long wave and pushes a well-defined cold front through our area. Without substantial surface cyclogenesis nearby, most of the upper dynamics to our north, and a narrow window for boundary layer recovery with southerly flow, strong to severe storms look unlikely as does flooding. Current guidance continues to suggest that what rain we do receive (and it doesn't appear to be drought busting amounts by any means with the most aggressive guidance suggesting amounts around 1 inch...) would be beneficial. With the stout front and cooler temps arriving aloft, some thunder may be possible though not explicitly defined in the gridded forecast. Timing, possible accumulations totals and additional event details will be refined over the next several days. /86/ && .AVIATION... (12Z TAFS) Issued at 646 AM CDT Fri Oct 7 2022 VFR flight cats with northerly winds, generally less than 15mph with brief higher gusts up to 15-20mph, are anticipated through the period. Dry front is expected to move through today, keeping northerly winds somewhat gusty into the aftn & lingering into the overnight hours. Winds will pick up similar again on Sat. Some few- sct cigs around 7-8kft are psbl, but most will be high cirrus. /DC/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 85 58 78 51 / 0 0 0 0 Meridian 85 56 77 48 / 0 0 0 0 Vicksburg 88 58 79 50 / 0 0 0 0 Hattiesburg 88 59 82 50 / 0 0 0 0 Natchez 87 60 80 53 / 0 0 0 0 Greenville 87 55 76 47 / 0 0 0 0 Greenwood 86 53 76 46 / 0 0 0 0 && .JAN WATCHES/WARNINGS/ADVISORIES... None. && $$ DC/LP/DC