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
000 FXUS64 KHGX 092353 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 653 PM CDT Sun May 9 2021 .AVIATION [00Z TAF ISSUANCE]... ...A Severe Thunderstorm Watch for Madison, Houston, Trinity and Polk counties through 10 PM CDT tonight... Mix of VFR to MVFR expected this evening with MVFR to possible IFR cigs developing tonight into Monday morning. Cigs over areas south of I-10 will have a chance to scatter out to VFR in the morning, but portions north of it may still see MVFR cigs lingering well into the late afternoon hours. Moderate winds currently at most TAF sites, but are expected to relax tonight and remain at 10 KTS or less on Monday. GLS/LBX may still see some winds of 10-15 KTS on occasion. Weather will be tricky throughout the forecast period. A cold front will slowly make its way into the northern portion of the CWA tonight and stall near the central area. Activity will likely continue to focus mostly along the NE quadrant of the CWA with showers and thunderstorms moving in and out throughout the night and could at times affect UTS/CXO. There is also a chance for CLL/IAH to see some isolated activity later tonight. The cold front will meander over SE Texas Monday, and could bring about a few more rounds of showers and thunderstorms throughout the day. Hazards associated with this activity include heavy rainfall, strong gusty winds and hail. 24 && .PREV DISCUSSION... /ISSUED 332 PM CDT Sun May 9 2021/ SHORT TERM [Tonight through Monday Afternoon]... - Severe thunderstorm watch issued for Houston and Madison counties at 3 pm. - Gusty southerly flow continues as storms developing quickly in the vicinity of the cold front. Scattered showers and thunderstorms also developing over Madison/Houston counties this afternoon though have not gotten well organized yet. CAPE in excess of 2800 to near 3200 j/kg in place over the northern counties this afternoon/early evening. Expecting very rapid intensification of the storms and the watch may need expanding in areal coverage. 85-90 degrees inland at 3 pm and heat indices of range. Already in the mid 80s across the area with heat indices of 91-99! Although the temperatures will be coming down with the lowering of the sun the instability will be slower to diminish and the threat for severe could extend a little past midnight over the northern counties. S/W driving this should be departing the areas to the east by around midnight. The main threat from these storms should be hail and possibly large hail. A strong cap remains over the south and has gotten stronger and is increased to around 11.2C at IAH per AMDAR. The storms that develop to the north and move off the boundary should move east and southeast but as they move south expect capping to hamper development. A few spotty fast moving light showers were and will be dotting the area beneath the cap tonight. The front does keep moving very slowly south tonight and will probably reach the northern counties before stalling. Outflow from the storms mainly in the northeast will likely create a confused wind field over the CWA by early morning. The front continues wobble around over the northern CWA Monday but with some s/w ridging could see a break in the storms in the morning and then with afternoon heating some redevelopment but not likely as intense as what could occur tonight. 45 LONG TERM [Monday Night Through Sunday] The stalled boundary will be draped the northern third of the area Monday night, which is where it will stay for most of Tuesday. There is still some uncertainty on exactly where the front will end up. Guidance has it setting up anywhere between I-10 to north of the area. Most CAM guidance keeps it around Burleson through Polk, which is what is indicated in the forecast. Conditions are looking favorable for showers and thunderstorms on Tuesday: - Stalled boundary across the area - A shortwave moves through the area helping to develop storms along the stalled surface boundary - East/southeast Texas will be in the right entrance quadrant of a jetstreak providing sufficient upper level divergence to support storm development -PWATs climbing to near 2 inches region wide meaning any storms that do develop will be able to produce locally heavy rainfall. Exactly where the locally heavy rain falls will be driven by the location of the front, so hopefully that comes into better view in the coming day. Again as of now, the northern third of the area looks to be where the front ends up stalling through Tuesday afternoon. The front finally begins a slow crawl to the coast late Tuesday into Wednesday morning. Another shortwave will be moving through the area early Wednesday morning reinvigorating showers and thunderstorms along the boundary. However, instead of the precipitation occuring mainly across the northern portion of the area, it`ll be concentrated down near the coast. The cold front finally ejects east of the area late Wednesday bringing an end to the wet weather we have been seeing - for at least a day or two. High pressure builds in behind the exiting front providing the region with mostly sunny skies and drier conditions through Friday morning. However, there is some uncertainty in how strong this high pressure will be. The GFS has a stronger high pressure building in over North Texas on Wednesday helping to dry us out fairly quickly Wednesday evening. The EC develops a weaker high pressure system which keeps the more humid airmass in place over SE Texas through the rest of the workweek. Either way, this high pressure will be fairly progressive in its movement eastward with southeasterly flow picking back up late Friday that will continue through the weekend. Precipitation chances return on Saturday as a shortwave moves through the area. Guidance is still differ on the coverage of these showers, but have continued the slight chance to chance of showers Saturday afternoon through Sunday. Temperatures through midweek will generally be on the cooler side during the day thanks to rain cooled air and cloud cover, while overnight lows will be on the milder side as that same cloud cover keeps radiational cooling to a minimum. Temperatures do climb back to near seasonal by the end of the week with the southeasterly flow redeveloping across SE Texas. Fowler MARINE... The remaining small craft advisories for the 20 to 60nm waters will drop off this afternoon, but seas of 4 to 6ft will persist through the evening requiring small craft to continue to exercise caution. The onshore flow will persist through midweek causing continued high risk of rip currents along Gulf facing beaches. A weak, slow moving cold front will move into the coastal waters late Tuesday and into Wednesday bringing scattered showers and thunderstorms. Light to moderate northeasterly flow develops late Wednesday behind the frontal passage which continues through Friday afternoon. Onshore flow redevelops late Friday that will persist through the weekend with increased chance of precipitation. Fowler && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 72 81 66 78 63 / 60 30 40 80 70 Houston (IAH) 76 86 73 82 68 / 20 20 30 70 80 Galveston (GLS) 76 83 76 80 73 / 20 10 20 40 60 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through Monday evening for the following zones: Bolivar Peninsula...Brazoria Islands...Galveston Island...Matagorda Islands. GM...NONE. && $$ Aviation...24
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