127 FXUS64 KMEG 052356 AFDMEG Area Forecast Discussion National Weather Service Memphis TN 556 PM CST Tue Feb 5 2019 .UPDATE... Updated to include 00Z aviation discussion below. && .PREV DISCUSSION... /issued 253 PM CST Tue Feb 5 2019/ DISCUSSION... The flow aloft continues to back more southwesterly with time as a trough digs over the western CONUS. Weak impulses will rotate around this trough, ejecting across the the region over the next 36 hours, enhancing rain chances during the midweek period. At the surface, a quasi-stationary front remains draped across the northwest portion of the CWA this afternoon, resulting in widespread dense fog and patchy drizzle to its north. A Dense Fog Advisory has been in effect all day north of this front and may need to be extended through the evening hours as it has been making only very slow progress to the north. This boundary has been poorly handled by guidance and I don't see any reason why that will change over the next several hours. South of the front, there has been just enough instability to support a few thunderstorms, mainly over MS. Temperatures will remain in the 60s for most areas overnight, maintaining the warm, moist environment across the region. Ascent will be primarily forced by warm advection with scattered showers anticipated overnight. Again, a few thunderstorms will be possible as well. The surface front should be north of the CWA by tomorrow morning, but large scale ascent will continue downstream of the deep trough over the west. The upper-level jet will nose into the Ohio Valley, which should help deepen a surface low to our north. South winds will respond by increasing to 10-15 mph, pumping addition moisture into the region. Precipitable water is progged to increase to ~1.5" which would be on the order of 3 standard deviations above climatology. With a strengthening low-level jet within the warm sector of the approaching cyclone, heavy rainfall remains the primary threat. The greatest potential for heavy rain will be in the vicinity of the retreating frontal boundary over the Ohio Valley. However, several inches of rain will be possible across the Mid-South, mainly focused north of I-40. The heavy rain threat will exist primarily between 12z Wednesday and 18z Thursday. Right now we expect widespread 1-3 inches across west TN, the MO Bootheel, and northeast AR with localized higher amounts. As the trough swings across the region on Thursday, the attendant surface cold front will sweep across the Mid-South. This will bring much colder air to the CWA with high temperatures Friday some 30-35 degrees colder than the previous day. Temperatures are expected to fall behind the front with highs early in the day across the northwest counties. Showers and thunderstorms along and ahead of the front will move into the Mid-South late Wednesday night and early Thursday. As stated yesterday, the main risk for strong/severe storms will be to our west, but there is just enough shear and instability to support a low-end threat across the Mid-South. Thunderstorms are expected to end from west to east Thursday afternoon with lingering light rain ending during the overnight period. Outside of north MS, temperatures on Friday will struggle to reach 40F. The cold air mass will persist through the overnight period with lows in the 20s. Fortunately, we look to remain dry during the Friday/Saturday period. However, unsettled weather looks to return to the area Saturday night into Sunday as the next trough takes shape to our west. The medium range models are in fair agreement with the synoptic pattern, depicting a strong, closed low over the Pacific Northwest with a fast-moving, lead shortwave trough lifting northeast across the Plains by Sunday morning. This trough will trigger a warming trend with temperatures warming back above 50F area wide by Sunday. Rain chances will increase Sunday into Monday as the trough deepens over the western CONUS and taps into a source of abundant mid/low- level moisture. Johnson && .AVIATION... 00Z TAF Set A mix of conditions to begin the period...but the general trend will be for IFR conds to develop over the next couple hours and persist through at least tomorrow afternoon. A frontal boundary remains stalled just south of JBR. This had led to dense fog and LIFR CIGs for much of the day. Expect LIFR conds to continue through about midnight, with improving conds to IFR as the front lifts north of JBR. As for sites MEM...MKL...and TUP, IFR and possibly LIFR developing this evening and through the overnight. Scattered showers will continue, so carried a VCSH at all sites through much of the period. Most precipitation will be focused along the front and northern sites tomorrow. Carried a VCTS at JBR late tomorrow morning as some convection may fire along the front. AC3 && .MEG WATCHES/WARNINGS/ADVISORIES... AR...Dense Fog Advisory until 6 PM CST this evening for Clay- Craighead-Cross-Greene-Mississippi-Poinsett. MO...Dense Fog Advisory until 6 PM CST this evening for Dunklin- Pemiscot. MS...None. TN...Dense Fog Advisory until 6 PM CST this evening for Dyer-Lake- Lauderdale-Obion. && $$