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 210000 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 600 PM CST Wed Jan 20 2021 .AVIATION [00Z TAF Issuance]... Aviation forecast remains on track with poor visibility and ceilings conditions through most of the TAF period. A mix of MVFR to LIFR conditions prevail with areas of dense fog and -DZ/VCSH thanks to a quasi-stationary boundary roughly extending along and north of a line from KVCT to KIAH to KLCH. KGLS and KLBX sites will likely remain in IFR/LIFR conditions throughout the entire TAF period. In fact, areas of dense fog will gradually expand inland into KHOU/KSGR sites (possibly further north) overnight into Thursday morning. The frontal boundary will lift north by Thursday morning, bringing scattered light rain mainly across our inland terminals. As of now, have VCSH after 16Z due to low confidence in timing and coverage of showers.05 && .PREV DISCUSSION /Issued 400 PM CST Wed Jan 20 2021/... .SHORT TERM [Today through Thursday Night]... Sea fog moved into most of the coastal areas overnight and has lasted into the afternoon hours as warm air (dew points in the 60s) continues to be advected over the cool Gulf waters. The Dense Fog Advisory for the coastal counties and near shore waters continues into Thursday morning. A weak warm front is currently moving slowly through the area and as of right now is right over downtown Houston. Winds south of the front are easterly/southeasterly and winds north of the front are northerly. Moisture is being trapped by an inversion around 850 mb, so the low overcast cloud cover will remain throughout the day. Coastal areas will have fog rolling in and out throughout the day as evident by local webcams in Galveston. Due to the cloud cover, temperatures not expected to rise too much with highs mainly in the mid 60s. Let`s backtrack to the warm front again. A few things will occur as a result of its passage. Overnight temperatures tonight will be mild (upper 50s up north/low 60s down south) and the sea fog will extend further inland, which will warrant more counties being added to the Dense Fog Advisories going into Thursday morning. A couple of inversions at 850 mb and 700 mb with slightly drier air aloft is keeping the moisture profile shallow, so not expecting anything more than mist for today/tonight. This changes going into Thursday morning as the southerly winds will increase PWATs up to 1.6"-1.8". Forecast soundings indicate that the two inversions will be mixed out and the profiles will be saturated up to 500 mb. With the increasing moisture and upper-level divergence setting up, more moderate rain showers become likely closer to the main moisture axis which will be just north of the CWA initially on Thursday morning but moving south throughout the day. Rain showers will fill in for the rest of us in the late morning/afternoon hours on Thursday, but as previously mentioned rainfall will be heavier the further north you go. Cloud cover expected to remain overcast for Thursday as well, but with the southerly winds the afternoon temperatures will be a bit higher in the upper 60s/low 70s. This is all courtesy of an area of low pressure that will be moving across Texas tomorrow along with favorable jet mechanics providing divergence aloft. The low will have a weak cold front associated with it that will be just northwest of the CWA on Thursday night. As for temperatures on Thursday night, expect them to be mild once again with lows in the upper 50s up north and in the low-to-mid 60s down south. Sea fog will move inland once again on Thursday night, so expect another round of reduced visibilites and ceilings for at least the southern half of the CWA. 26 .LONG TERM [Friday through Wednesday]... With the weak cold front making its way through SE TX on Fri, POPs will be on the decrease as a slightly drier air mass works its way into the region Fri night. Warm high temperatures on Fri (lower to mid 70s) are forecast to fall into the 50s br Fri night. This weak- er CAA is likely due to the strong surface high building down more to the east of the Mississippi River Valley. Another result should be this weak boundary stalling/lingering just off the TX coast Fri night...then moving back inland Sat afternoon/night. Kept with the previous forecast of scattered POPs across the CWA for the weekend. Sea fog could also remain an issue for our coastal counties/marine areas through the weekend as the warm onshore flow persists. The next upper trof is progged to move across Rockies late Sun and then into the Southern Plains by Mon. This system should help draw a strong cold front into/across the state on Mon. This timing does seem a bit faster than previous ones (with both ECMWF and Canadian about 6hrs ahead of the GFS). So, it will be interesting to see if later runs keep with this trend. Otherwise, the return to more sea- sonable temperatures are expected next Tues/Weds behind this front. 41 .MARINE... Low visibilities via sea fog will remain the primary issue for the bays/nearshore waters the next day or so. The Marine Dense Fog Ad- visory has been extended and expanded to include our entire marine FA until tomorrow afternoon. This may need to be extended into to- morrow night/Fri morning as the next cold front is not expected to reach the coast until perhaps Fri afternoon or evening. This break from the sea fog may be short-lived as the main push of the colder and drier air will be more east of the region. This along with the boundary stalling just off the coast Fri night. S/SE winds are set to return Sat and strengthen Sat night. This should bring a return of sea fog/rain chances...and perhaps some elevated seas into Sun. The next cold front should move off the coast Mon. 41 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 55 66 57 71 54 / 40 80 60 10 0 Houston (IAH) 61 72 63 73 57 / 20 60 60 30 10 Galveston (GLS) 59 66 62 68 58 / 10 20 40 40 20 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Dense Fog Advisory until 9 AM CST Thursday for the following zones: Brazoria Islands...Chambers...Coastal Brazoria...Coastal Galveston...Coastal Matagorda...Galveston Island and Bolivar Peninsula...Matagorda Islands. GM...Dense Fog Advisory until 9 AM CST Thursday for the following zones: Coastal waters from High Island to Freeport TX out 20 NM...Galveston Bay. && $$
Dense Fog Advisory
URGENT - WEATHER MESSAGE National Weather Service Houston/Galveston TX 855 PM CST Wed Jan 20 2021 TXZ213-227-237-238-313-211500- /O.EXA.KHGX.FG.Y.0004.000000T0000Z-210121T1500Z/ Inland Harris-Fort Bend-Inland Brazoria-Inland Galveston- Coastal Harris- Including the cities of Houston, Missouri City, Mission Bend, Sugar Land, Rosenberg, First Colony, Pecan Grove, Pearland, Alvin, Angleton, League City, Friendswood, Pasadena, and Baytown 855 PM CST Wed Jan 20 2021 ...DENSE FOG ADVISORY IN EFFECT UNTIL 9 AM CST THURSDAY... * WHAT...Visibility falling to one quarter mile or less in dense fog. * WHERE...Inland Harris, Fort Bend, Inland Brazoria, Inland Galveston and Coastal Harris Counties. * WHEN...Until 9 AM CST Thursday. * IMPACTS...Hazardous driving conditions due to low visibility. PRECAUTIONARY/PREPAREDNESS ACTIONS... If driving, slow down, use your headlights, and leave plenty of distance ahead of you. && $$
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