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
183 FXUS64 KHGX 250343 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1043 PM CDT Wed Mar 24 2021 .UPDATE... The strong east wind observed earlier today in the Galveston Bay area has become more moderate this evening. However, this lull is expected to fairly brief, and by morning, strong onshore flow is anticipated to redevelop in advance of a cold front on its way to Southeast Texas. At the coast, there are a batch of hazards to be aware of, including strong rip currents, high water levels resulting in minor coastal flooding, and a small craft advisory for Gulf waters. Further inland, we are still looking for the potential of some showers and thunderstorms on or ahead of the front. Multiple severe thunderstorms are occurring along a line from North Texas down into West Central Texas. While this line will continue to make its way towards the area through the night, I anticipate that their intensity will wane deeper as the front arrives. HREF probabilities show only modest potential for exceeding 500 J/Kg of SBCAPE and virtually no potential for reaching 1000 J/Kg. Additionally, the timing of the front means the front will be arriving in Southeast Texas when the diurnal/nocturnal cycle will enhance capping the most. As a result, the line should diminish to be dominated by showers, with some isolated thunderstorms embedded in the line as well. However, should mesoscale factors help bolster existing severe storms against the less conducive environment, there is some low-end severe potential in our far north/northwest, for locations such as Caldwell, Bryan, and Madisonville. Beyond that, as the front moves across the area this morning, we`ll see height falls aloft as an upper trough swings in, as well as at least some modest surface warming, both of which will work to diminish capping. All guidance is pretty unanimous that the most significant threat for severe weather (and it is significant) is far to our east. However, just as things may linger a bit longer than expected tonight, quick destabilization could allow for things to get started a bit on the early side, giving us another low-end threat for a severe storm or two east of I-45, and likely east of the Houston metro entirely. && .PREV DISCUSSION /Issued 401 PM CDT Wed Mar 24 2021/... .SHORT TERM...(Through Thursday Night) A strong east wind on the north side of a weak surface low and warm front has brought elevated water levels and strong rip currents to parts of the coast today. Will maintain the Coastal Flood Advisory through 03z and will extend the Rip Current Statement through 03z. Water levels should begin to decrease as we approach low tide by mid evening. Weak warm air advection has also fostered the development of weak showers and patchy drizzle. The warm air advection will persist into the evening and periods of very light rain/drizzle should continue. Warm air will flow over cooler waters near the coast and Galveston Bay and there is some potential for sea fog tonight. The water temperature is up to 67 degrees so dew points will need to climb a few more degrees for saturation to kick in. Cloud cover and mixing from winds will keep MinT values on the warm side and lows will probably stay in the mid 60`s areawide. A short wave trough over New Mexico this afternoon will move toward the Texas panhandle tonight. This feature coupled with favorable jet dynamics and a surface cold front will trigger a line of showers and thunderstorms to develop over Central Texas. The line is expected to weaken late tonight as the cold front nears the area. The jet dynamics will lag behind the surface front and capping over SE TX will hinder the development of strong to severe storms. That said, if a cold pool can propagate into the region, perhaps a few strong to severe storms will be possible between 06-12z. SPC has outlooked areas northwest of a Brenham to Livingston line in a Slight to Marginal Risk for severe storms for tonight and a Marginal Risk east of a line from Crockett to Galveston for Thursday morning. Skies will clear quickly in the wake of the front and clear skies areawide are expected by 19z. The warm start to the day coupled with a NW wind should allow MaxT values to be on the warm side. Most areas will approach 80 degrees with full sunshine expected in the afternoon. Clear skies and cooler temperatures are expected Thursday night as the dry air will allow for strong radiational cooling. 43 .LONG TERM [Friday Through Wednesday]... Surface high pressure behind the departing cold front will continue to drift to the east throughout the day on Friday, eventually allowing for a return to onshore flow heading into the weekend. The relatively pleasant daytime dewpoints in the 50s will quickly rise into the mid to upper 60s overnight, while increasing cloud cover and thereby limited radiative cooling will help keep lows in the mid to upper 60s at most locations during the evening hours. Meanwhile, a longwave upper trough will begin to push into the southwestern CONUS during this time, eventually digging into the Four Corners region by Saturday. This feature will induce cyclogenesis along the leeside of the Rocky Mountains, and a cold front extending from it will slowly move into the Southern Plains on Saturday. With southerly flow remaining on the cards into Saturday, another warm and humid day can be expected with inland highs approaching the low to mid-80s and lows remaining in the mid to upper 60s. By Saturday afternoon, total PWs surge to over 1.5in across the region, which will prove favorable for shower/storm activity ahead of the approaching front on Saturday evening. Our next period of significant precipitation looks to begin on Sunday as the surface front pushes into SE TX during the morning/afternoon hours, with showers and storms developing along/ahead of the advancing boundary. Both the GFS/EC solutions continue to depict this boundary stalling near the coast on Sunday evening and precipitation continuing as a result, though the GFS continues to trend a bit further southward compared to the EC. With the boundary remaining stalled and the aforementioned upper trough ejecting into the Central Plains by Monday, global models continue to indicate the development of a weak coastal low over the Western Gulf. GFS remains the most aggressive in its depiction of the resultant QPF, showing a prolonged and widespread rainfall event across the northern half of our area through early Tuesday. The EC, given its more northward positioning of the stalled boundary, keeps the bulk of the activity north of the area. I have deviated from the NBM`s bearish PoPs and increased values to 30-40% in some locations as a result of this recent trend in global deterministic solutions. That being said...this potential event is still 5-6 days out and there`s still plenty of time for the picture to change. With the upper trough pushing further eastward by late Monday/early Tuesday, precipitation chances will dwindle ahead of the potential approach of a strong cold front around Wednesday. While a lot of uncertainty remains regarding the timing and intensity of this feature, our next period of cooler and drier weather looks to possibly arrive by mid-to-late next week. Cady .MARINE... A challenging marine forecast today as sustained east winds were considerably higher than forecast. East winds at 20 gust 30 knots have increased water levels on the Bolivar with some minor coastal flooding reported. Water levels at 3 PM reached 3.5 feet and it will probably increase a bit more before stabilizing and then dropping as low tide approaches mid evening. The east winds have also produced dangerous rip currents. These should begin to weaken later tonight as winds decrease ahead of the next front. Despite lower winds over the southern Gulf waters, seas are elevated and will maintain a SCEC for those areas. A cold front will cross the coastal waters Thursday morning. An offshore flow will develop but the pressure gradient does not look tight so a light to moderate offshore flow is expected. Surface high pressure will move toward the Arklatex Thursday night and then push east on Friday. An east wind will develop on Friday in the wake of the departing sfc high. Onshore winds will develop on Saturday and remain onshore through the weekend. A weak coastal trough could develop on Sunday and sfc winds will briefly back to the east before veering to the SE on Monday as low pressure develops over the western plains. 43 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 59 76 53 81 63 / 40 20 0 0 10 Houston (IAH) 64 79 53 81 67 / 40 50 0 0 10 Galveston (GLS) 65 78 62 75 67 / 40 40 0 0 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk until 10 AM CDT Thursday for the following zones: Brazoria Islands...Galveston Island and Bolivar Peninsula...Matagorda Islands. Coastal Flood Advisory until 10 AM CDT Thursday for the following zones: Galveston Island and Bolivar Peninsula. GM...Dense Fog Advisory until 10 AM CDT Thursday for the following zones: Coastal waters from Freeport to Matagorda Ship Channel TX out 20 NM...Coastal waters from High Island to Freeport TX out 20 NM...Matagorda Bay. SMALL CRAFT SHOULD EXERCISE CAUTION through Thursday afternoon for the following zones: Galveston Bay...Matagorda Bay. Small Craft Advisory until 4 PM CDT Thursday for the following zones: Coastal waters from Freeport to Matagorda Ship Channel TX out 20 NM...Coastal waters from High Island to Freeport TX out 20 NM...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. && $$ UPDATE...Luchs SHORT TERM...43 LONG TERM...Cady AVIATION...KBL MARINE...43
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