814 FXUS64 KLUB 111244 AAA AFDLUB Area Forecast Discussion...UPDATED National Weather Service Lubbock TX 744 AM CDT Mon Mar 11 2019 .UPDATE... We have issued a Dense Fog Advisory (DFA) for much of the Caprock this morning...ending at 1 pm. Regional observations and webcams confirm areas of dense fog across much of the central and southern South Plains. Short term NWP suggest this fog will expand across the northern South Plains and southwest Texas Panhandle through mid-morning before gradually thinning late morning and early afternoon. Given this, we have decided issue a DFA for most of our counties on the Caprock through 1 pm. No other adjustments were made to the forecast at this time. && .PREV DISCUSSION... /issued 636 AM CDT Mon Mar 11 2019/ AVIATION... Confidence has improve somewhat on how conditions will evolve through the day. VLIFR conditions have set in at KLBB, KPVW is IFR, and KCDS is down to MVFR. Expect all sites to fall to IFR to LIFR conditions later this morning and remain at or below IFR through the day at all TAF sites. May see brief periods of MVFR at the terminals once rain begins later this afternoon. Precipitation will be intermittent through this afternoon before going prevailing before sunset local time. Precipitation and IFR to VLIFR conditions will then persist through the overnight hours into Tuesday morning. Jordan PREV DISCUSSION... /issued 230 AM CDT Mon Mar 11 2019/ DISCUSSION... TODAY THROUGH TUESDAY: Elevated, unstable ascent was underway at 2 AM along an axis from Snyder to Aspermont to Seymour complete with a band of showers and thunderstorms. This line coincided well with a stationary baroclinic zone from 850-700 mb which will continue to focus isentropic lift on and off through today, although how much of this translates into additional measurable rain is more uncertain as many of the latest high resolution models have trended drier. Some of this may be due to an embedded impulse aloft that is suggested by a recent veering of 850-700 mb winds from SE-SSW per regional VWP data. While this doesn't seem significant, the reduced orthogonal flow to the SE-NE baroclinic zone implies less ascent and hence a probable lull in precip. As such, rain chances were lowered after 7 AM area wide before resuming an uptick this afternoon as the 850 mb flow backs more southeasterly and resumes favorable ascent relative to the elevated front. Some upright instability could breed small hail with a few storms (as we've already seen from radar with this morning's storms), but this threat looks considerably better after midnight tonight through Tuesday morning as isentropic ascent amplifies markedly due in large part to a healthy SSE low level jet. This jet should drive the elevated warm front north overnight accompanied by an uptick in storms, mainly over the South Plains with additional development advancing northward through daybreak. Sufficient elevated CAPE and even effective bulk shear could foster some organized severe storms with hail the primary threat. Given decent support from CAMs and favorable vertical profiles from the deterministic model, we've inserted mention of hail in the forecast. It appears another lull in precip would follow Tuesday morning's round with the afternoon hours serving as the quiet before the real storm Tuesday night. How well the surface warm front carries north tomorrow is not clear as the NAM is the lone wolf in keeping the shallow cool dome locked in place over all but our SW zones. Our forecast blends more toward the remaining guidance, but still keeps high temps below climo given abundant stratus even in the warm sector. TUESDAY NIGHT AND BEYOND: Incredible 500 mb height falls of nearly 200 meters in 6 hours will overspread the region Tuesday night with the arrival of a negatively tilted trough. With PWATs over 1/2 inch area wide, strong upper divergence, a stout Pacific front, and favorable lapse rates aloft, the writing is on the wall for a widespread rain event. In fact, lift is so stout that even with modest MLCAPE we will likely see some severe storms in the form of a squall line with downbursts racing east across the region Tuesday night. As long time forecasters here have noted from past events like this, the severe hail threat with these Pacific front squall line events is usually confined to early in the event. Although potentially brief given fast storm motions (50+ mph), the heavy rain threat may still hit hard enough to cause minor flooding. Once precip wanes from W-E before daybreak Wednesday, the concern shifts to a regional high wind event as the upper cyclone undergoes drastic deepening and slowing from the NW Texas Panhandle into SW Kansas. This pattern alone places the South Plains in a long duration wind event with westerly winds sustained around 40 mph with gusts over 60 mph. The blowing dust threat could in fact be made worse following Tue night's heavy rain as sand and fine dirt granules are typically more vulnerable to blowing around from the impact of large rain drops. A Canadian front arriving Wed night will lower temps through the rest of the week, with potentially some additional precip chances developing on Sat as a trough closes off over the Desert Southwest and wanders across West TX. Weakly cyclonic NW flow should follow this decaying upper low by Sun into early next week with perhaps modest reinforcements of modified Canadian air at various times. && .LUB WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 1 PM CDT this afternoon for TXZ021>023- 027>030-033>036-039>042. && $$ 23/14