810 FXUS64 KLUB 241755 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 1255 PM CDT Mon May 24 2021 .AVIATION... Skies have cleared from I-27/US-87 westward, with KPVW and KLBB now within VFR thresholds. KCDS will hold on to MVFR through the early/mid afternoon before also rising to VFR conditions. This afternoon, VFR conditions are expected at all terminals. Thunderstorms are expected to form along the TX/NM border around 22z and will move eastward through this evening and tonight. A TEMPO has been introduced at all terminals to account for expected restrictions to ceilings and visibilities due to thunderstorms. && .PREV DISCUSSION... /issued 1004 AM CDT Mon May 24 2021/ UPDATE... Forecast appears on track today as the mesoscale setup continues to appear favorable for convection later this evening into tonight. Surface flow remains generally southerly as of mid- morning, but is expected to back slightly this afternoon. A very moist airmass remains in place, and ample instability with CAPE in excess of 2000 J/kg will establish throughout the day with minimal inhibition. Despite this, deep layer shear remains weak, and with surface convergence limited to the dryline, widespread convection is not expected during the day today. Tonight, confidence remains high that convection will affect the CWA as a cluster of storms moves eastward out of NM. CAMs have been consistent with this evolution for several runs, and given the unstable and very moist airmass in place, a forward propagating, cold-pool driven QLCS appears plausible late tonight, with all severe hazards possible including hail, damaging wind gusts, and heavy rain. PREV DISCUSSION... /issued 622 AM CDT Mon May 24 2021/ AVIATION... Current MVFR CIGS are expected to persist for the rest of the morning hours at KLBB and KPVW and into the early afternoon at KCDS along with continued breezy southeasterly winds. Confidence is fairly high in a complex of thunderstorms to move through the KLBB and KPVW terminals this evening. Therefore, a TEMPO was placed in these TAFs due to the high probability. Confidence is lower in any thunderstorms reaching KCDS so mention was left out of that TAF at the moment. PREV DISCUSSION... /issued 245 AM CDT Mon May 24 2021/ SHORT TERM... Conditions look better today for eastern New Mexico convection to reach West Texas. Upper level flow will not be quite as veered as previously thought for today. Atmospheric flow will continue to be close to meridional especially higher up in the atmosphere. A very subtle short wave at 500mb was rotating around the larger upper level low centered in the Intermountain West. The short wave looks to be better defined closer to the 250mb level. A weak speed max will be associated with this short wave as it approaches the area this afternoon and evening. Although this short wave is fairly difficult to pick out on water vapor imagery, there is a notable area of positive vorticity advection in the upper levels of the atmosphere over the southwestern US that models are picking up on. This area of PVA is forecast to approach the area late this afternoon into the evening hours which will provide more large scale lift to the region. Mid level lapse rates will steepen ahead of convective initiation late this afternoon. Model progs show values increasing to around 8 C/km by late afternoon. This will lead to strong instability across the entire FA. Low level mixed layer CAPES will be on the order of 2000 J/kg with minimal capping in eastern New Mexico. Strong capping on the caprock will likely remain so convective development will be limited to the dryline. Deep layer shear will slightly increase through the day today but still still be very weak for late May standards. Deep layer shear vectors are only on the order of about 20kt. We would expect initial convection around 21-22Z and then congealing into a cold pool MCS progressing eastward through the evening. Very unstable air in advance of the convection will likely keep convection sustained for a prolonged period of time this evening. Initially, cloud bases in eastern New Mexico and near the Texas/New Mexico state line will be relatively high but should lower as storms move east. Lastly, precipitable water values from the 00Z AMA/MAF raobs showed values greater than the 90th percentile or around 150% of normal which will undoubtedly lead to localized flooding with storms later today. LONG TERM... The upper-level flow will become southwesterly Tuesday and should remain southwesterly through the latter part of this week before becoming more zonal. At the surface, winds will remain southerly to southeasterly, helping to advect moisture into the area. The the southwesterly flow aloft will allow for weak shortwaves to round the trough to our west and eject into the region, bringing at least a low chance of precipitation each day through the end of the week. A dryline will mix to around or just east of the I-27 corridor Tuesday, helping to limit thunderstorm activity to the southeastern Texas Panhandle and the Rolling Plains. With large instability still in place and bulk shear ~30 kt, any storm that does develop has the potential to become severe. However, overturning of the atmosphere from the MCS that is expected to move through the FA Monday night into Tuesday could help to limit the intensity of thunderstorms Tuesday evening. With strong south to southeasterly surface flow, low-level moisture will continue to increase over the FA. This will help to increase the chances of thunderstorms on Thursday and Friday. The forecast is a bit uncertain for the weekend as the GFS has an upper ridge building into the area a day or so sooner than the ECMWF. If the GFS is correct, we can expect a dry and warmer than normal weekend. However, if the ECMWF is correct, there will be the potential for precipitation and below normal temperatures for the FA. As of now, we will keep the NBM values, which are closer to ECMWF guidance. GKendrick && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ 30/30/01/10