Houston, TX, during the early morning.
Northwest Houston, TX, during the early morning.
Houston, TX radar, during the early afternoon.
Northwest Houston, TX, during the late evening.
West Houston, TX, during the late evening.
Houston, TX radar, during the early evening.
Houston, TX radar, during the early night.
Houston, TX radar, during the early night.
West Houston, TX, during the early night.
Locations: Northwest and west Houston, TX.
Thoughts: The predicted rain had not yet arrived yet, except for maybe in some locations in the Houston, TX area. The day was warm, dry, and cloudy.
Issued by NWS Houston/Galveston, TX
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000 FXUS64 KHGX 210301 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 901 PM CST Tue Feb 20 2018 .DISCUSSION... At 7 PM, a cold front extended from about Paris to Gateville to Fort Stockton. Scattered showers continue to develop just ahead and behind the front. Earlier tonight, some moderately heavy rain fell across Walker, Madison and Houston counties with Wyser Bluff in Walker county receiving 1.58 between Noon and 7 PM. FWIW, the radar is underestimating precip and the gages are showing 25-35% higher totals. At 850 MB, a 45-50 kt low level jet is located over East TX/West LA with a ribbon of higher moisture across central LA into central TX. At 300 mb, upper level winds show a broad split over N-NE Texas. Water vapor imagery shows a well defined disturbance over northern Mexico. Storms were developing in advance of this feature and will continue to do so. Both the GFS/ECMWF show this speed max and this feature will approach the middle coast placing SE TX in a LFQ. Feel convection will fill in toward the middle coast tonight and move into SE TX prior to sunrise. The 00z CRP sounding showed a PW value of 1.81 inches which is one of the highest values I`ve ever seen in February. The unseasonably high moisture coupled with the approaching speed max and a slow moving cold front should set the stage for widespread showers and thunderstorms early Wednesday. Some of the rain will be locally heavy. Widespread rainfall of 1 to 3 inches looks likely over most of the region with some isolated areas receiving between 3 and 5 inches. Since the 00z models are not all in yet, will hold off on a Flash Flood Watch but one might be required for Wednesday morning. Temps are tricky as well and will fall significantly in the wake of the cold front. Have raised PoPs for 09-12z and bumped up QPF grids. Rest of the forecast is in good shape. 43 && .PREV DISCUSSION... /ISSUED 546 PM CST Tue Feb 20 2018/ AVIATION [00Z TAF Issuance]... Pretty messy weather expected for the upcoming TAF period. Ceilings have improved in most areas this afternoon but will likely fall back down to IFR later this evening and overnight tonight. The models are suggesting the front and associated showers and storms may be arriving a little quicker than previously indicated. Either way, the front will push through CLL and UTS first with showers and thunderstorms before drifting into the Houston Metro (IAH, HOU, SGR, CXO) early tomorrow morning and sticking around for most of the day. Expect rounds of showers and thunderstorms throughout the day tomorrow, potentially tapering off to SHRA towards the tail end of the taf period. Ceilings may improve to MVFR or even VFR briefly before the front arrives, but should fall back down to IFR in the wake of the front. 11 PREV DISCUSSION... /ISSUED 344 PM CST Tue Feb 20 2018/ NEAR TERM [Through Tonight]... Radar this afternoon has become more active from Columbus up to Brenham/College Station to Madisonville. Based on SPC mesoanalysis data, this activity seems to be rooted within the main moisture axis of 1.6-1.8 inches of precipitable water. This is also where the LLJ is the strongest with 850mb wind around 40-50 knots and 850mb dewpoints around 13-14C. This appears to be a more favored area for convection and training of cells given the deep upper level flow from the SW. Upper air analysis shows a deep trough over the western U.S. with a strong ridge in the western Atlantic. Sandwiched in between is the Plains where the pattern is supportive of the cold front in north Texas stalling over the area. However since there are 30-40 degree temperature drops behind the front and the shallow nature of the front, this front will continue to push south and likely reach the northern third of the forecast area around 12Z Wed. Latest HRRR and WRF ARW/NMM all support this idea along with the NAM. Synoptic models are slower to catch onto this trend. With this shift in the forecast, temperatures will be falling behind the front and this means the boundary will be more of a focus for rainfall. Trends in the NAM and then the last couple of HRRR/RAP13 runs raise some eyebrows with their QPF output. If there is a WRF model runs that lends support to these trends it might be the 12Z WRF- ARW from Texas Tech while the NCEP WRF- ARW/NMM show less precipitation through 12Z Wednesday. Overpeck SHORT TERM [Wednesday Through Thursday Night]... Bottom line: it`s going to rain Wednesday and then begin to taper off Thursday. From a pattern recognition standpoint, this forecast for the next couple of days is not that hard. Upper levels - we have a trough out west with SW jet stream flow and an approaching jet streak. In fact the beginnings of the divergence from this jet streak approaches S Texas and SE Texas Wednesday morning. Deep moisture is in place with high dewpoint air through the boundary layer. Precipitable water values peak around 1.6 to 1.8 inches which is right at the 30 year climo max for this time of year. In fact, the 12z CRP sounding from today had a record of 1.61 inches of PW. Now let`s throw in a 30-40 knot LLJ from the south that lines up normal to an approaching cold front. And that`s the last ingredient: the cold front is now expected to push off the coast and stall so there will be lift over the front with all the deep moisture over the region. So overall, models are in decent agreement with this pattern going forward. The devil will be in the details of the mesoscale. That is where the recent 12Z/18Z NAM trends along with the HRRR/RAP may be onto something that the other models are not resolving. Mesoscale interactions will be critical as areas of training of storms and favored areas of convection could shift and likely shift southward from the original threat area for heavy rainfall. The NAM in particular shows a meso-low feature forming on the front tied to the divergence in the jet streak. This meso-low supports heavy rainfall farther south and a trend to monitor overnight. Of course the NAM has a history of not performing well in convective situations, but still a trend to watch. Heavy rain threat still looks to be for the northern third of the forecast area from Brenham to Huntsville northward where 2-4 inches of rain look likely through 12Z Friday or a 2 day total for Wednesday and Thursday. Farther south looks like 1 to 3 inches are more likely with 1 inch along the coast. This is a little higher than yesterday`s forecast and on track from the forecast package from the overnight shift. However there very well could be a shift southward in the threat area. This means that the isolated areas of 3 inches could become more common but for now this will serve as an alternate scenario. Overall confidence remains in the higher rainfall amounts occurring over the northern portions of the forecast area. The main impacts will be still street flooding in urban areas and the usual low lying areas/underpasses. This includes rural roads in valleys or near creeks. For more impacts see the hydrology section below. Thursday the cold front that stalled along or just off the coast will push back north as a warm front. This will keep rain chances going in the forecast with mainly elevated convection. PW values still range from 1.6 to 1.8 inches but should be decreasing Thursday night into Friday. Upper level forcing also moves off to the NE which may limit the extent of convection later on Thursday. There may still be some brief periods of heavy rainfall but not as many convective clusters moving over the region. Rainfall amounts look to be more in the tenth to a half inch amounts on Thursday so the majority of the heavy rainfall threat will be on Wednesday. Overpeck LONG TERM [Friday Through Tuesday]... The warm front that will push through SE TX Thursday, will move move well north of the region into the NE TX on Friday. Winds will remain onshore behind this feature, allowing moisture to continue funneling into the region. Precipitable water (PW)values will rise back up to 1.3-1.4 inches. Therefore, showers and thunderstorms will again be possible Friday and Saturday, with the best coverage north of I-10 Friday into Saturday. Precip coverage will then shift east by Saturday afternoon, with the best chance for showers and thunderstorms east of I-45 and south of I-10. Saturday night into Sunday morning an area of low pressure associated with a frontal boundary tracks eastward across the midwest. A Pacific airmass fills in behind this feature, as the front pushes southward into the region reaching our northern zones as early as Saturday afternoon. There is some discrepancy between the global guidance regarding the timing of this front. The GFS brings the cold front into the region faster than the ECMWF. GFS also shows cooler temperatures behind the front in comparison to the ECMWF, as drier air filters into the region. Forecast soundings show a quick drop in PW values behind the front, potentially falling as low as 0.4-0.6 inches according to both the GFS and ECMWF. High temperatures behind the front will range between the mid 60s-70s, with low temperatures in the low 50s- 60s. Surface high pressure attempts to build back into the region Monday into Tuesday, and a warming trend will commence. Temperatures should rise back above normal climatological values by the beginning of next week. Onshore flow will also return, as winds turn out of the southeast. Hathaway MARINE... South to southeast flow will continue through Wednesday afternoon. This will keep the moisture flowing into and across the coastal waters leading to areas of fog with some dense fog possible. Have reissued the marine dense fog advisory for the 0-20 nm waters through Noon Wednesday. Improvement will be slow Wednesday morning. The persistent flow will maintain seas of 5-8 feet well offshore so will extend the SCA through 12z Wednesday. Winds relaxing as the front stalls which should allow seas to slowly subside though as the front begins to retreat back northward from the coastal areas the threat of fog returns Thursday. The warm moist flow Thursday through Saturday will likely lead to continued fog issues. Guidance in general shows a front pushing off the coast early Sunday morning probably ending the fog threat but with showers and thunderstorms. Tides will continue to run well above normal though with the lower amplitude tidal cycle don`t anticipate coastal flooding issues. 45 HYDROLOGY... In anticipation of heavy rainfall and resulting rises in rivers, tributaries and bayous, here are some items to consider when looking at hydrographs and forecasts from the WGRFC. River forecasts include 24 hours of QPF. Based on the river forecast output, no basins are expected to reach action stage. WGRFC did run contingency forecasts with 48 hours of QPF which resulted in some rises to action and minor flood stages for the Trinity, Brazos and San Jacinto Rivers. These forecasts hinge on how much rain ultimately falls upstream and is routed through the river system so there is still time to monitor conditions and forecasts for changes. Harris County bayous would need 4 inches of rainfall or more to generate flooding but this is also dependent upon rain fall rates and how quickly the rain falls. Bottom line: we will be monitoring conditions for rises on rivers and bayous but biggest impact still to be street flooding/flooding of low lying areas and poor drainage areas. KLG/SO && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 78 54 56 43 59 / 70 90 90 70 60 Houston (IAH) 79 69 74 55 75 / 50 50 90 70 60 Galveston (GLS) 75 65 72 62 73 / 20 30 70 70 50 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...Dense Fog Advisory until noon CST Wednesday for the following zones: Coastal waters from Freeport to the Matagorda Ship Channel out 20 NM...Coastal waters from High Island to Freeport out 20 NM. SMALL CRAFT SHOULD EXERCISE CAUTION until 6 AM CST Wednesday for the following zones: Matagorda Bay. Small Craft Advisory until 6 AM CST Wednesday for the following zones: Waters from Freeport to the Matagorda Ship Channel from 20 to 60 NM...Waters from High Island to Freeport from 20 to 60 NM. && $$ Discussion...43
Hazardous Weather Outlook
Hazardous Weather Outlook National Weather Service Houston/Galveston TX 549 PM CST Tue Feb 20 2018 TXZ163-164-176>179-195>200-210>213-226-227-235-220000- Austin-Brazos-Burleson-Colorado-Fort Bend-Grimes-Harris-Houston- Jackson-Liberty-Madison-Montgomery-Polk-San Jacinto-Trinity- Walker-Waller-Washington-Wharton- 549 PM CST Tue Feb 20 2018 This hazardous weather outlook is for portions of Southeast Texas.. .DAY ONE...Tonight Scattered to numerous showers and thunderstorms will possible tonight. Some of the storms will produce locally heavy rain especially north of a Columbus to Conroe to Livingston line. Minor flooding in low lying and other flood prone areas will be possible. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Scattered showers and thunderstorms will persist for much of the day. Rainfall could again be locally heavy, especially in the morning. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. $$
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