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
579 FXUS64 KHGX 160440 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1140 PM CDT Mon Mar 15 2021 .AVIATION... A mix of MVFR/IFR and LIFR ceilings are developing across SE TX. The KHGX VWP shows winds of 20 knots at 1000 feet and the additional bit of mixing should favor more of a low stratus deck overnight and have leaned toward the ECMWF and LAV guidance that favors the stratus over fog. Ceilings should begin to mix out by 16z with a SW wind in the 1000-850 mb layer. Ceilings near the coast may never fully mix and MVFR/VFR ceilings will likely persist for much of the day. Low stratus will redevelop tomorrow night with a mix of mVFR/IFR ceilings developing between 00-03z. Sea fog has developed and moved into KGLS. Visibility will likely fall below a 1/2 mile at times and will likely persist all night. Should get a break on Tuesday but sea fog looks again possible tomorrow night with a mix of IFR/LIFR ceilings. 43 && PREV DISCUSSION... /ISSUED 351 PM CDT Mon Mar 15 2021/ SHORT TERM [Tonight through Tuesday Afternoon]... Clear skies north and cloudy/mostly cloudy south start off the forecast early this evening. Warm front on the coast will edge northward tonight and light onshore flow will bring with it the expansion of a low cloud deck across the region with fog becoming more widespread again. Dense fog advisories will probably be needed first near the coast then expanding inland through the late evening hours and after midnight. Also in the short term as the warm front meanders inland some spotty showers and even an isolated brief thunderstorm or two will be possible mainly along and south of a Columbus to Conroe to Liberty line through early evening. Tuesday will be dealing with strengthening WAA and a strong cap. Spotty showers will be possible throughout the day initially south then shifting north in the afternoon. Fog should dissipate a little quicker with the expected mixing so by 9 or 10 at the latest inland. Another warm day in the prefrontal environment and expect temperature to pop up into the 80-85 degree range. 45 LONG TERM [Tuesday Night Through Monday]... By late Tuesday, an upper trough/closed low will be centered over the Four Corners region, with global models indicating its associated surface cyclone deepening to below 1000mb. Across SE TX, low level moisture will continue to be on the rise behind the departure of today`s surface warm front, with PW values eventually surging to 1.25 to 1.5 in by early Wednesday. While scattered to isolated showers will continue to develop under this onshore flow regime, the main weather event in the extended period continues to be the approach of a stronger surface cold frontal boundary which will traverse the region on Wednesday as the aforementioned surface low pushes towards the Ozark Plateau. Global models continue to agree in regards to the timing of this fropa, with the boundary reaching the Brazos Valley around daybreak on Wednesday, pushing through the metro area by early afternoon, and advancing offshore by late afternoon. As the front moves through the region, more widespread showers and storms are expected to accompany its passage. The pre-fropa environment looks fairly conducive for thunderstorm activity, with GFS/NAM soundings indicating around 1500 J/kg of SBCAPE and 40 to 50kt EBWD showing on latest NAM/GFS model soundings. That being said, soundings also indicate a fairly robust capping inversion (-100 to -200 CINH) around 06 to 09Z on Wednesday, which may prove difficult to erode with the front pushing through prior to peak diurnal heating. SPC continues to include areas generally west of I-45 in a marginal risk area for severe storms during this time. In any discrete cells that form along/ahead of the advancing front, strong winds and hail may be a risk. Those commuting or with outdoor plans on Wednesday morning and afternoon should keep a close eye on their conditions and be prepared to respond to a warning if issued. Showers and storms will diminish by late Wednesday afternoon as the boundary pushes offshore. Moderate north to northwest winds in its wake will allow for cooler and drier air to filter into the region, with high temperatures returning to more seasonable values (high 60s/low 70s into the weekend). Dominant surface high pressure will allow for generally clear skies and pleasant conditions during this time, with the weekend shaping up to be more favorable for outdoor activities. By Sunday afternoon, high pressure will push eastward and allow for a return to onshore flow. A warming and moistening trend can be expected ahead of the next potential frontal passage early next week. Cady AVIATION [18Z TAF Issuance]... Stationary front off the coast south of PSX and stalled around GLS...(may have just briefly pushed southeast of GLS 12-16z) but back near Bolivar/GLS now. Temperatures on the rise and fog dissipating so for the CXO area southward to GLS still mix of LIFR south-improving to MVFR at CXO then SKC. The northern edge should continue to erode southward expecting IAH/HOU/SGR to go VFR this afternoon and persist through early evening then as warm front intrudes inland lowering ceilings. IFR lowering into widespread VLIFR for most terminal sites by 09z sooner closer to the coast. Slow improvement Tuesday morning with winds becoming southerly and by late morning/early afternoon expect gusty south winds to take hold at 5-15 knots over the southwestern areas and may reach into HOU/IAH after 18z Tuesday. Spotty showers will be possible over the southern terminals through 00z and should probably shift northward through 03z though rapidly decreasing in coverage and intensity. 45 MARINE... Moist southerly flow will continue overnight and expect sea fog to return to the nearshore waters/bays tonight...probably after 9 pm and latest by 2 am. Just a few showers this afternoon and early evening then rain chances should diminish. Winds gradually increasing Tuesday as LLJ develops and extends from near the Coastal Bend arcing up into SETX so the western waters will no doubt get a little gustier than the eastern waters. Shower and thunderstorm chances increase as a cold front moves across SETX Wednesday and into the coastal waters late Wednesday afternoon...the tail of the front will likely fight against the cap and lose and so coverage of storms looks better over the Galveston Bay area than Matagorda Bay. Winds in the wake of the front strengthen to 15-20 knots a few hours after FROPA. Thursday morning NNW flow gradually veers to the NE Thursday night/Friday and continues into Saturday. SCEC conditions likely with seas of 5-7 feet/winds 15-20 knots with a brief period of SCA as seas potentially reach 7 feet. Moderate to strong persistent easterly flow Saturday night veers to the southeast Sunday and will look for elevated tide level impacts/rip currents/SCA conditions Sunday into Tuesday. 45 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 61 84 63 76 47 / 10 30 60 50 0 Houston (IAH) 65 82 67 78 50 / 40 30 60 80 0 Galveston (GLS) 65 76 67 73 56 / 20 20 50 80 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Dense Fog Advisory until 11 AM CDT Tuesday for the following zones: Galveston Island and Bolivar Peninsula. GM...Dense Fog Advisory until noon CDT Tuesday 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...Galveston Bay...Matagorda Bay. && $$ Discussion...99 Aviation/Marine...99
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