Area Forecast Discussion
Issued by NWS Houston/Galveston, TXVersions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
790 FXUS64 KHGX 100209 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 909 PM CDT Fri Apr 9 2021 .UPDATE... Burleson, Brazos, Grimes, and Washington counties have been dropped off the Severe Thunderstorm Watch that was issued for the northern third of the area earlier this evening. Storms were just not able to break the cap earlier today, and now with the loss of daytime heating, just don`t think the severe weather threat is high enough to warrant a Watch in those counties. The Watch does continue for the more northern counties (Madison, Walker, Houston, Trinity, San Jacinto, and Polk) as the thunderstorms located in Navarro and Anderson counties (as of 9pm) may be able to reach our Watched area by 11pm. These storms have had a history of producing large hail. Fowler && .PREV DISCUSSION /Issued 710 PM CDT Fri Apr 9 2021/... .SHORT TERM [Through Saturday Night] The main weather concern is the potential for strong to severe thunderstorms this afternoon and tonight; however, the main limiting factor continues to be a strong cap. This limiting factor continues to keep our confidence levels low to moderate for any convection initiation across the region. Southerly flow continues to increase this afternoon with gusts from 20 to 30 mph across most of the region. This pattern will continue to draw higher sfc dew points, ahead of an approaching surface low and associated sfc boundary. The low is currently moving across northwest TX/southwest OK while a dryline is bisecting TX from north to south, just west of the Brazos Valley. Early this afternoon, a broad region of thunderstorms began to develop across the ARLATEX region, with a few showers/lightning strikes developing over Houston county. This activity is aided by decent southerly LLJ and steep lapse rates. Will continue to monitor the evolution of these storms and the potential for some clearing across southeast TX over the next few hours as any break in clouds may help spark any convection activity. The environment still looks conducive for strong to severe thunderstorms. 18Z soundings still suggest MUCAPE 2,500-3,500 J/kg this afternoon and evening with effective shear (EBWD) around 30-40 kts under very steep low to mid- level lapse rates. However, with cloud cover and 850:700 mb temperatures in the 12-16 C range any potential convective updraft will have to overcome the strong capping inversion. If storms develop this afternoon and evening, discrete storms will be the primary storm mode through this evening as 0-6km shear remains quasi- normal to the boundary. The greatest threat will be along and north of I-10 with large hail and damaging winds as the main risks. An isolated tornado cannot be ruled out given strong favorable conditions. As we progress into the evening hours, the main focus for showers and thunderstorms will be along the convergence zone as the cool front moves southeast into the region. The front will move across our northwestern counties around midnight, then moving southeast into the coast by daybreak. Will continue to monitor the passage of this front, as strong to severe storms will be possible along the boundary. The main areas of concern will be across our northwest and northern counties with damaging winds as the primary severe weather risk. The severe weather threat gradually diminishes as the front moves into the Houston metro area and into the coastal zones by early Saturday morning. Another concern early Saturday morning will be the potential for fog, some locally dense, ahead of the front. The greatest risks look possible along the coast as soundings suggest a well- saturated low- mid layer under a persistent southerly flow. North to northeast winds are expected on Saturday; however, afternoon temperatures will once again climb into the mid 70s to low 80s. Surface ridging anchored over northeast TX will result in relatively dry conditions and light northeast to east winds through the end of the short-term period. 05 .LONG TERM [Sunday Through Friday]... E/SE winds are expected to be in place across SE TX by Sun with low- level moisture holding off its return until Mon. These increased PWs (from 1.3 to 1.8 inches) are forecast to persist as a large east-to- west swath across the northern Gulf/and adjacent states for most of next week. The moisture is expected to help fuel the development of scattered SHRAs (and isolated TSRAs) each day given the nearly cons- tant approach/passage of weak upper level disturbances (embedded in the generally zonal flow aloft), as well as weak surface convergence along/near the various frontal boundaries lingering over the region. Timing of said disturbances should be one of the main problems with this pattern and the upcoming forecast and just kept with the broad brushing of mostly 20-30% POPs each day next week. And with regards to temperatures (even with the persistent rain chances/clouds), the overall trend(s) should lean more toward the warmer side of normals next week. There will likely be a day or two here and there that`ll be cooler per the various frontal boundaries (for northern counties in particular), did keep with mostly lower to mid 80s for highs and mid to upper 60s for lows through Mon-Weds. Perhaps slightly cooler Thur/Fri. 41 .AVIATION [00Z TAF Issuance]... MVFR to VFR conditions will continue through the next few hours with ceilings around 1500 to 2500ft and breezy southerly flow. CIGs will drops to 700-1500ft across the area tonight as the sun sets and a front approaches from the northwest. VCTS will be possible around 3-4z at CLL and UTS, but the thunderstorms will be isolated and may miss the terminals all together. The boundary will be pushing through CLL around midnight, IAH around 4-5am, and then off the coast by 8-9am ushering in a northerly wind shift. Patchy fog will be possible starting late this evening, but then the fog threat dissipates after the boundary pushes through. A thin line of showers will be possible with the FROPA. Skies will be clearing out behind the front leading into a VFR day across the area tomorrow with breezy northerly winds. Fowler .MARINE... The tightened gradient ahead of the next cold front will help keep SCEC conditions in place over the offshore waters through the rest of the afternoon and early evening. For the overnight hours, there is still a chance of some patchy sea fog over the bays/intracoast- al waterways as the onshore flow remains in place. But we should be seeing improved conditions by sunrise with the passage of the cold front into our marine waters. Isolated showers/thunderstorms could accompany this line as it moves southward into the Gulf. Otherwise, look for generally moderate N winds to develop by Sat afternoon... then decreasing to a light NE flow for Sat night. Mostly light E/SE winds starting on Sun are forecast to prevail through much of next week. However, there are also indications of increasingly unsettl- ed weather next week as a series of weak upper level disturbances/ deepening moisture help produce scattered showers/isolated thunder storms each day. 41 .FIRE WEATHER... The oft-neglected side of cold fronts shoving dry lines much further eastward than mixing alone allows shows up in our forecast for this weekend. Yes, we will get a taste of some unseasonably dry air. Right now, relative humidity is forecast to fall below 30 percent, and to around 25 percent in isolated spots both Saturday and Sunday. At the same time, we`ll be expecting moderate to occasionally gusty northeast winds. The strongest winds should be Saturday morning before humidity gets particularly low. On Sunday, winds should be lighter still, and begin to veer more easterly to southeasterly as the day goes on. With winds becoming more onshore, humidity will be higher as the work week begins. This misalignment of the strongest winds and lowest humidity make it pretty likely that we will not realize any critical fire weather conditions this weekend. But, we are starting to reach that time of year when air this dry is becoming less common, and when paired with moderate winds, this weekend could be more conducive for fire growth than typical for early April - for better or for worse. This would be particularly true in contiguous, grassy fuel beds, which will be most responsive to the low humidity. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 58 78 51 85 60 / 20 0 0 0 0 Houston (IAH) 65 81 56 84 63 / 30 10 0 0 0 Galveston (GLS) 69 79 65 81 68 / 20 10 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 10 PM CDT this evening for the following zones: Waters from Freeport to Matagorda Ship Channel TX from 20 to 60 NM...Waters from High Island to Freeport TX from 20 to 60 NM. && $$
No comments:
Post a Comment