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
000 FXUS64 KHGX 152348 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 648 PM CDT Thu Apr 15 2021 .AVIATION [00Z TAF Issuance]... Thunderstorms moving across the northern flying areas this evening producing around pea size hail. As of 2340z, radar indicate the northern portion of the line of cells weakening as it approaches UTS/CXO area. Further to the south, a strong storm is moving towards the IAH flying area and is expected around 0030z. This storm has produced pea size hail and winds around 30kts. By around 01z, the storms will be out of the flying areas with some scatted showers left behind through the night. Tomorrow morning, IFR to LIFR conditions are expected to return with lower ceilings at most TAF sites. 35 && .PREV DISCUSSION /Issued 345 PM CDT Thu Apr 15 2021/... .SHORT TERM [Today Through Friday Night]... Upper disturbance and associated shra and elevated tstms moving across ncntl Tx. Guidance is a mixed bag in regards to precip coverage and intensity across se Tx in the next 6-9 hours. Previous 24 hours worth of CAMs showed a fair bit of consistency with a cluster of strong elevated tstms developing and moving into the Brazos Valley and sinking to the southeast toward the I-10 corridor before weakening. Some of the recent runs aren`t quite as bullish, though some of the global models are still holding out hope for fairly decent coverage across parts of the area (mainly north of I- 10). Developing cluster north of Marble falls (340pm) may be the one earlier guidance was pinging on. Overall forecast confidence isn`t particularly very high. Will taper POPs very slightly, but mainly ride with the ongoing fcst into the evening and monitor trends. Recent aircraft soundings in the area show a saturated warm nose between H95-H7 so confidence is fairly high that any convective activity sagging into the CWA will remain mostly elevated with large hail being the primary threat into the mid-evening hours. Coverage/intensity diminishes a few hours after sunset. Otherwise, llvl flow will gradually veer to the se/s going into Friday as high pressure edges ewd. A very messy zonal pattern continues and the expectation is that another disturbance will move into the region during the day and generate some shra and possibly a few tstms. Better rain chances situated north of I-10. This impulse is fcst to move east of the area before a cold front moves into northern parts of the area Fri evening and off the coast before sunrise Sat. Though there will be some decent llvl convergence associated along the boundary, the deeper moisture axis will likely have moved out of the area w/ the passing disturbance. Suspect we`ll just see a narrow band of shra right along the front as it passes through. 47 .LONG TERM [Saturday Through Thursday]... Cold air advection and lingering cloud cover will keep temperatures over the weekend below normal with highs in the mid-to-upper 60s for Saturday and Sunday. Rain chances persist along the coast through Saturday night due to lingering moisture (PW values around 1") along with favorable jet mechanics (right entrance region) that will provide the upper-level support. With virtually no instability in place and dry air encompassing the atmospheric profile from the surface up to 700mb, expecting only isolated to widely scattered rain showers for Saturday. If anything, may have been too generous on the PoPs, but the highest probabilities will remain over the Gulf waters. Back to the CAA, overnight lows for Saturday and Sunday will feature temperatures that are 7-10 degrees below normal. Lows will dip down into the upper 40s/low 50s on each of these nights. CAA comes to an early Monday morning as surface high pressure slides off to the east and places the region in onshore flow by Tuesday. Resultingly, highs will be back in the upper 70s for Tuesday. Want to briefly mention that a shortwave trough will swing through the region on Monday night, but forecast soundings indicate a profile that is too dry aloft to support notable precipitation reaching the surface. GFS/ECMWF are in agreement on a surface cold front briefly pushing into the region on Tuesday night, which will help bring overnight lows back into the upper 40s/low 50s. Models agree that there will not be much moisture in place ahead of this front, but there is a bit of disagreement on if upper-level support will be present that could try to squeeze out some rain showers along the boundary. For now, leaned towards keeping PoPs out for this FROPA. Speaking of model disagreements, there isn`t a clear answer as to how long the CAA with this front will last but it will definitely be shorter than Friday night`s front. ECMWF/Canadian keep CAA lingering through Wednesday evening, while the GFS ends the CAA on early Wednesday afternoon. This makes Wednesday`s high temperature forecast tricky since one model shows afternoon WAA while others show persisting CAA. Surface high pressure pushes off to the east by Thursday and with strong onshore flow likely, moisture increases quickly with PW values reaching 1.3"-1.7" by Thursday night. A shortwave trough swinging down into the Southern Plains along with a developing surface low pressure in north TX will combine to develop showers and thunderstorms in the area going into Thursday afternoon. Batiste .MARINE... Moderate northeasterly to easterly winds will prevail for the Gulf waters through the evening hours. Onshore flow returns on Friday morning ahead of our next cold front that will push through the coastal waters on early Saturday morning. Anticipating moderate to strong northeasterly winds in the wake of this front that will prevail through the weekend. Resultingly, offshore seas will elevate to 6-7 feet by Saturday afternoon and persisting through Sunday. Rain showers will linger along the coast and Gulf waters through Sunday morning with dry conditions following going into early next week. Winds will gradually transition back to easterly on Monday and southeasterly on Tuesday as surface high pressure slides off to the east. Batiste && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 63 76 53 65 49 / 80 80 40 10 10 Houston (IAH) 65 75 59 68 53 / 60 60 50 20 10 Galveston (GLS) 69 77 64 70 60 / 50 30 50 30 20 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...Small Craft Advisory until 7 PM CDT this evening 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. && $$
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