600 FXUS64 KLUB 230020 AAA AFDLUB Area Forecast Discussion...UPDATED National Weather Service Lubbock TX 720 PM CDT Thu Apr 22 2021 .UPDATE... Minor update, primarily to tweak temperatures downward off the Caprock the next few hours (given current observations). We did also start the patchy fog mention a couple of hours earlier, after 04Z, for locations along and just west of the edge of the Caprock. A more widespread risk of patchy fog, potentially dense, will cover much of the South Plains region late tonight into early Friday morning. Somewhat elevated surface winds and veering flow will tend to mitigate the coverage/duration of the fog, but given the risk for at least brief pockets of dense fog, we did add a mention to the HWO. No other adjustments were made to the forecast at this time. && .PREV DISCUSSION... /issued 651 PM CDT Thu Apr 22 2021/ AVIATION... Stratus remains in place at KCDS, and in fact it has been dropping through MVFR levels the past few hours. This trend will continue, with IFR expected from late tonight into Friday morning. KPVW and KLBB are currently VFR, but shallow moisture will surge across the terminals this evening, leading to a period of IFR to LIFR cigs and/or fog late this evening into early Friday. Conditions will quickly improve at KLBB and KPVW as winds veer around mid- morning, with VFR expected through the afternoon as westerly winds increase to breezy levels. KCDS will be slower to improve, but should return to VFR around early afternoon. KCDS will also have an outside chance of experiencing high-based convection late Friday. Regardless, a cold front will sweep through the terminals Friday evening/night with a northerly wind shift and a risk of another bout of lower clouds. PREV DISCUSSION... /issued 234 PM CDT Thu Apr 22 2021/ SHORT TERM... Clearing from west to east has begun to increase early this afternoon after a slower than expected start. With the clearing now in progress, temperatures have begun to climb. Was tempted to lower max temperatures for this afternoon after clearing was slow to materialize, but current trends seem to imply current values on the Caprock are reachable by later this afternoon with more sun. South/southeasterly surface flow overnight will advect enough moisture on the Caprock to expect some patchy fog to develop after midnight and linger for a couple of hours after sunrise. By early afternoon tomorrow, a progressive and sharpening H50 trough will scour and sweep boundary layer moisture east as moderate to strong surface westerly winds spread east out of New Mexico. With very dry conditions already persisting, a Fire Weather Watch has been issued for most locations on the Caprock from noon through 8pm CDT. A cold front pushing south out of the Texas Panhandle should reach our northern most counties around sunset tomorrow evening. LONG TERM... A shortwave trough will be traversing the CWA late Friday afternoon with low amplitude ridging moving in on Saturday. The amplitude become progressively more muted, in time, as the flow regime by late in the afternoon will become quasi-zonal. By Sunday evening, southwesterly flow aloft will develop as a new system comes ashore the Pacific Northwest. We've seen some differences in evolutionary morphology betwixt the GFS/ECM for early next week with less coherency noted today than the past few. Timing differences also complicate matters. What concerns me about the GFS is that there isn't much phasing (between the desert southwest trough and disturbances across southern Canada) to really drive the more progressive outlook in the GFS. A slower progression, as hinted by the ECM, would tend to be favored next month (with increased thunder chances) though it's still too early to call which will get it right. Might be a mix of the two by the time Tuesday rolls around. In addition to the thunder chances, the track of the system's "core" will have an effect on winds/fire weather potential. Surface low/triple point should be situated near the NERN corner of the CWFA on Friday evening. Most of the deep convection should remain east of the area. That said, we continue to see a thin layer of moisture up around H6 and a few joules of CAPE tapering as the evening progresses. A cold front will surge through the region Friday evening and some sprinkles are possible in the post-frontal environment. Thanks to the quasi-zonal flow aloft, the northerly surface flow at the start of Saturday will quickly become southerly as lee troughing develops to our west. Compared to earlier this week, it will seem hot on Sunday and Monday with winds ramping up each day as well. The wind speed trend in MOS has been increasing for Tuesday. With the continuing drought especially out west, this leads to many questions that will be answered over the next few days as guidance becomes more coherent. Either way we cut it, fire weather will be of concern early next week....and possibly a risk of storms at some point...which looks to be Tuesday night at present. FIRE WEATHER... Fire weather concerns will approach critical levels Friday with 15- 25 MPH sustained winds for most locations on the Caprock, increasing ERC levels and RH values in the single digits to lower teens. A Fire Weather Watch has been issued from noon until 8PM tomorrow evening. && .LUB WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Friday afternoon through Friday evening for TXZ021-022-027>029-033>036-039>043. && $$ 23/26