Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/21/20

Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
541 PM MDT Thu Aug 20 2020 .AVIATION... 00Z TAF CYCLE Upper high circulation will persist over northeast/east central Arizona. Isold to sct showers and tstms along the central mt chain and Contdvd will continue to drift to the south. Gusty erratic outflow winds will be associated with many of the cells with brief MVFR cigs/vsbys and mt obscurations in the stronger cells. Convection may push swd over the northeast and east central plains aft 03Z while diminishing over wrn NM. HZ due to wildfire smoke circulating around the upper high will continue over western and central NM but in general VFR conditions will prevail. && .PREV DISCUSSION...301 PM MDT Thu Aug 20 2020... .SYNOPSIS... Hot and mainly dry condtions will continue Friday through the weekend with strong high pressure remaining anchored over Arizona. Best chances for a brief afternoon or evening shower or thunderstorm will be in the mountains. High temperatures will continue to be well above averages for late August but start to trend down a degree or two each day starting next week. && .DISCUSSION... .SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)... We have seen convection initiate over the Tunas Mountains as well as the Sangre de Cristos Mountains but this activity has yet to move south or southeast off the mountains. We are also seeing convection form on the AZ/NM border west of Gallup and towards Grants. Otherwise convection is pretty quiet and having issues getting going. Part of this is due to the upper level ridge situated over Arizona with 593-593dm 500mb heights. Precipitable water is also below normal with 0.7" on the ABQ sounding. The GOES PWAT imager shows similar values over much of central/western NM. Moisture is a little higher to the east and this is where we find a marginal risk for severe storms. The potential for an isolate severe storm is there but there is some doubt as to how much instability will be available given lower moisture. Drier air in the boundary layer will support downburst winds but that is if there is enough overall moisture and instability for a storm to develop. If a cluster of storms can form off the mountains then we might see a more organized threat with strong outflows driving more convection. Latest HRRR model trends suggest the possibility so we will continue to monitor but also leery of limited instability. Going into Friday, it looks like overall moisture will be more of a concern. Based off model consensus, 700-500mb flow from the NNW/N will allow for drier air to move into New Mexico and drop PWAT down below 0.7 inches and closer to 0.5 inches. Moisture is not much better in the higher terrain so even having convection in the Sangre de Cristo Mtns will be tough. Same can be said farther SW towards Gila National Forest. As such, we have decreased chances of storms for most areas tomorrow. That`s not to say there won`t be storms, but that any storms will be very isolated in nature. LONG TERM...(SATURDAY THROUGH WEDNESDAY)... Crazy stagnate upper-level pattern continues through the weekend and into early next week. Big bubble has nowhere to go through early next week thanks to a low- latitude trough stuck over the deep south. Hot and relatively dry continues Friday through the weekend with the best shot at showers and thunderstorms over and due south of most mountain ranges in the state. Eventually the southern upper-level trough lifts out to the northeast and the Four Corners` high starts to shift northeastward over CO early next week. This shift results in a more favorable surface pattern to get low-level Gulf moisture in from the southeast. GFS and ECMWF agree on this change with most activity focused on western NM Monday and Tuesday. Despite the low-level moisture in eastern and central areas of the state, dry air aloft from the Southern Plains moves into eastern and central portions of the state early next week, shutting down shower and thunderstorm chances. By mid-week, models agree that a weak easterly wave gets into the mix, generating deformation over northern NM and helping to get storms going over the northern mountains during the afternoon. These storms then slide westward over the northwest third during the evening. 39/33 && .FIRE WEATHER... The main change from today to Friday is that drier air works in from the northwest. This means isolated afternoon showers and storms will be confined to areas from the east slopes of the central mountain chain east to the central and northeast highlands. Over the weekend and into next week, it does not look like much improvement with precip chances so dry conditions will continue. Granted it`s still possible to get the typical shower/thunderstorm activity in higher terrain but since the upper level ridge does not move much from the Four Corners region, there will be little steering flow so most storms will be pulse storms. Smoke is becoming or has become more of a problem for New Mexico as fires in Colorado continue to burn. The Medio fire north of Santa Fe continues to burn but not producing the amount of smoke the fires in Colorado are. Smoke will be a problem going into the weekend since the upper level flow does not change but a lot of the smoke has remained in upper parts of the atmosphere, not settling into valleys. Still possible for that to happen especially each night but for now most smoke projections keep the smoke lofted. This will be a day to day situation to monitor. 39 && .ABQ WATCHES/WARNINGS/ADVISORIES... None. && $$
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
149 PM AKDT Thu Aug 20 2020 .SYNOPSIS... Above normal temperatures continue across Northern Alaska beneath a ridge of high pressure. A few showers and isolated thunderstorms are possible from Fairbanks east and in the Eastern Brooks Range today, and from Tanana east tomorrow. Stratus remains on the North Slope and on the West Coast with onshore flow. This beautiful stretch of weather will come to an end this weekend as a weather front will bring rain to the West Coast by Saturday morning, eventually spreading east to Fairbanks and the Eastern Interior by early Sunday morning. && .DISCUSSION... An upper level closed low that was located south of Yakutat yesterday has moved to SW of Ketchikan. An upper level low associated with this feature is centered south of Northway, with the associated surface low near Glennallen. This feature continues to advect moisture into the Interior from Fairbanks east, providing clouds and scattered showers. From Fairbanks west, ridging is dominant with mostly clear skies for all areas inland of the coast. Onshore flow from the dome of high pressure over the Bering Sea is allowing stratus and clouds to linger along the coast. Between the ridges extending from the Bering Sea NE and from Ketchikan NW lies a weak thermal trough over the Eastern Brooks Range. This area may see isolated thunderstorms this afternoon as a shortwave trough passes to the north along the Arctic Coast. The next notable weather system will arrive to the West Coast on Saturday, bringing rain. Thunderstorms can be expected on the leading edge of this front as it moves into the Western Interior on Saturday afternoon, and again in the Eastern Interior on Sunday afternoon as it progresses eastward. Behind this front, Northern Alaska enters a troughing pattern with cooler temperatures and more showers expected into next week across the forecast area. Models... The GFS and the NAM currently show better timing regarding the weather front and associated shortwave moving west to east across the North Slope, with the ECMWF and HRRR solutions being too slow. Looking ahead into Sunday, the NAM is much sharper with the shortwave at the leading edge of the longwave trough moving into the West Coast and then into the Interior. As a result, forecast rainfall totals are much higher than in the GFS and ECMWF model runs that reached that time frame yesterday. The GFS has also increased its rainfall totals for Saturday night and Sunday in the Western Interior, with both models putting the highest amounts on the west slopes of the Alaska Range. Thunderstorms can be expected on the leading edge of the front where it passes during the afternoon hours. At this time it appears that this will be in the Western Interior on Saturday and east of Fairbanks on Sunday, with stratiform rain beginning in Fairbanks early Sunday morning. The timing of the forecast reflects the timing of the GFS and ECMWF, while the NAM solution is a bit slower. North Slope and Brooks Range... Isolated thunderstorms are expected in the eastern Brooks Range this afternoon as a shortwave trough passes just to the north of the weak thermal trough in place. Otherwise expect mostly clear skies and warm temperatures to continue through Saturday in the Central and Eastern Brooks Range, with stratus lingering along the coast. At this time, expect that the bulk of the precipitation from the weather front moving in from the west will fall south of the Brooks Range. West Coast and Western Interior... Fog and stratus remains over much of the West Coast, Lower Yukon, and Yukon Delta from Kotzebue south. The Western Interior remains clear. Expect these conditions to persist until Saturday when the weather front arrives, spreading precipitation from west to east. Isolated thunderstorms will occur ahead of the front in the Western Interior on Saturday afternoon before the bulk of the rainfall arrives. Expect showers and cooler temperatures behind the front. Central and Eastern Interior... A few isolated showers and thunderstorms are expected from Fairbanks east today, but otherwise expect mostly sunny skies and warm temperatures to continue through Saturday. A weather front will arrive on Saturday night and spread rain from west to east with cooler temperatures and more showers behind it. Coastal Hazard Potential Days 3 and 4... Exposed south facing capes and shores in the Bering Sea including Nome may see water levels 1-2 feet above the normal high tide line on Saturday and Sunday with S and SE winds along and behind a weather front. Flooding is not expected at this time. && .FIRE WEATHER... Above normal temperatures will continue into Saturday for most of Northern Alaska. Minimum RHs will dip into the 30 and 40 percent range over much of the Interior during the day, but overnight recovery will be excellent. Isolated thunderstorms are expected east of Fairbanks and in the Eastern Brooks Range this evening, east of Fairbanks tomorrow, and in the Western Interior on Saturday. && .HYDROLOGY... The Chisana River at Northway has been reported to be high after ~0.5" of rain fell in its basin overnight. The river is expected to crest this afternoon and slowly fall afterwards. Flooding is not expected. For the latest river forecasts and conditons, visit && .AFG WATCHES/WARNINGS/ADVISORIES... None. && $$ CHRIEST AUG 20
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
253 PM AKDT Thu Aug 20 2020 .SHORT TERM.../Thursday evening through Saturday night/ The short term features a complex set us as a stacked area of low pressure meanders around the southeast gulf with multiple waves rotating into the Panhandle from British Columbia. As with many easterly wave scenarios, guidance has a poor handle regarding the timing of each wave impacting the area. Tried to incorporate hi-res models into the precipitation forecast as they may be able to resolve the smaller features better than the courser lower resolutions models. No matter which model chosen to make the forecast, the overall message stays relatively the same over the weekend with waves of showers moving into the Panhandle from the south and east and peaks of sun likely in between waves. For Thursday evening, a wave of energy moving into the Panhandle from the SE will increase the chance of showers and thunderstorms this evening. Hi-res model soundings indicate a marginally unstable atmosphere across the far southern Panhandle with CAPE values above 500 j/kg, LI around -1, and dew points in the upper 50s to near 60. The HRRR has convection moving into Misty Fjords this evening and heading northward towards Petersburg/Wrangell. With a 50 kt mid level jet streak over the south and effective bulk shear 25 to 30 kt, the possibility is there for convection to hold together through the evening and make its way north and west towards the Central Panhandle. Thunderstorms will transition to plain showers overnight and head up into the northern Panhandle. The main threats with any shower or thunderstorm will be brief periods of heavy rain, gusty winds, and lightning. Waves continue to rotate into the Panhandle Friday and Saturday. Current thinking is that the Northern Panhandle, along the Coast Mountains, and the far SE Panhandle have the best chance of receiving rainfall from these waves. Lower PoPs potentially along the outer coast further away from the main energy. Kept a slight chance for thunder in the forecast for Petersburg, Wrangell, and Misty Fjords for Friday afternoon as the atmosphere may have a chance to destabilize. In between waves, breaks in the clouds are certainly possible allowing temperatures to spike in the afternoon. Expect warmest temperatures to be Thursday afternoon/evening with highs a few degrees cooler each day as 850 mb temps begin to cool and easterly downsloping flow weakens. With such a convective/showery pattern, it`s very difficult to pin point each individual shower that forms so temperatures may vary greatly over short distances. Areas that receive more breaks in the clouds could make a run for 70F while showers will keep other areas cooler. Impactful winds ongoing at the beginning of the short term are expected to subside Thursday evening. A strong low offshore of POW Island combined with a 50 kt jet streak at 850 mb and an unstable atmosphere is producing Gales in the coastal waters from Cape Edgecumbe down towards the Dixon Entrance. Gusty winds to 30 kt are being observed around POW and the Ketchikan area while gusts to 35 kt are in Clarence Strait. Winds are expected to diminish this evening as the low pulls away to the SW. Lighter winds expected Friday into Saturday across the Panhandle. Confidence in the forecast is below average for this time of year as guidance does not have a good handle on the timing of each wave passing through. Used Hi-res models to try to add detail to the precipitation forecast. No major changes made to winds today. .LONG TERM.../Saturday through Thursday/ The forecast for the weekend has come into somewhat better consensus, featuring more rain for the panhandle. While parts of the northern and central panhandle may experience a brief period of lower chances of rain early on Saturday, another easterly wave will likely take aim at the panhandle during the afternoon hours, lasting through much of Sunday. Just how much of the area the wave will cover is not yet entirely certain, but currently have it progged to focus on the central and southern panhandle. This second wave will bring with it some degree of moisture, and so expect there to be some QPF accumulation from it, helping to nudge the already impressive summer totals which parts of SE Alaska have seen even higher. The rain will continue until a ridge succeeds in displacing the by this point weakening low. Still some model disagreement on how long it will take the low to dissipate, but think that it will meander into the Haida Gwaii area, and have largely faded away by daybreak on Monday. As this low leaves, still some indications that Monday may offer a few breaks in the clouds, particularly for the southern and central panhandle, as the ridge moves into SE Alaska. Given that this ridge is centered largely over the Gulf and the panhandle as opposed to the Yukon, am not expecting much in the way of a substantial boost in temperatures from it, though temperatures may climb into the low to mid 60s in fortunate parts of the area. This break may prove to be fleeting in nature as guidance has been hinting at the emergence of another system which could impact the panhandle late Monday and through the middle of the week, though model disagreement by this point is substantial, making it hard to give specifics this far out. && .AJK Watches/Warnings/Advisories... PUBLIC...Strong Wind until 7 PM AKDT this evening for AKZ027. Strong Wind until 6 PM AKDT this evening for AKZ028. MARINE...Gale Warning for PKZ041-042. Small Craft Advisory for PKZ022-036-043-051. && $$ CM/GFS Visit us at
Area Forecast Discussion
National Weather Service Charleston SC
1047 PM EDT Thu Aug 20 2020 .SYNOPSIS... A stationary front over the area will gradually weaken late this week. High pressure is then expected to prevail early next week as Tropical Depression 13 moves northwest, possibly into the eastern Gulf of Mexico as a tropical storm or hurricane. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As of 1045 PM: The Coastal Flood Advisory has been cancelled. The forecast products will be updated to remove product headline. Otherwise, the forecast appears on track. As of 930 PM: KCLX indicates an isolated thunderstorm over Tattnall County, with isolated showers across portions of SE GA. Latest HRRR indicates very little coverage through the rest of the evening into the late night hours. The update will generally feature changes to hourly temps to align with observations. As of 745 PM: Deep convection and associated outflow boundaries have advanced well inland this evening. Lingering instability may support isolated convection through the rest of this evening. Near-term guidance indicates that a mid-level short wave will lift from south to north on the east side of a closed H5 low. This feature should produce another round of showers and thunderstorms around dawn. I will update the forecast to adjust PoPs and rain-cooled temperatures. Previous Discussion: This evening and tonight: A few of the thunderstorms are now starting to show a little more vertical development with higher reflectivity reaching closer to the -20 C level. Overall, still not much change to the forecast thinking and the severe weather potential. Effective wind shear of 20-25 knots is available, with MLCAPE values peaking around 2,000 J/kg. DCAPE values are quite modest, in the 600-700 J/kg range. Still, we could see a couple of clusters become organized and produce strong wind gusts. Diurnal convection should dissipate as usual later this evening. Then through the overnight, models depict shortwave energy streaming through in the southwest flow which should help to drive nocturnal convection. The bulk of the activity should be over the coastal waters, but could again impact land areas with isolated to scattered showers and thunderstorms. Patchy, mainly shallow, ground fog will be possible but isn`t expected to be widespread enough to explicitly mention in the forecast. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Moderate confidence this period. The area will remain between troughing to the west and ridging to the east which will keep abundant moisture and periodic upper-level forcing in place. Combine these factors with mesoscale boundaries from the sea breeze and convective outflows and the result will be higher than normal rain chances, with most of the rain likely each afternoon/evening. In general areas near the coast will see the highest rain chances early in the day with inland areas seeing the best chances later in the day as the sea breeze pushes inland. Deep layer shear looks to be a bit stronger the next few days which would support a greater risk for severe storms but instability appears like it will remain limited so not expecting widespread severe weather at this time. Temperatures should remain near to slightly above normal. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... The upper-level trough stretching from the OH Valley to the Lower Mississippi Valley will begin to weaken and lift Sunday night. Meanwhile, high pressure in the Atlantic will gradually shift towards the Southeast U.S. and approach the coast early next week. Additionally, high pressure is expected to develop over the Mid- Appalachians early next week. Sea breeze convection will be possible each afternoon and evening. Though, coverage should be near or just below normal. The convection is forecasted to dissipate each night. Temperatures will be near normal. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Deep convection and associated outflow boundaries have advanced well inland this evening. Lingering instability may support isolated convection through the rest of this evening. Near-term guidance indicates that a mid-level short wave will lift from south to north on the east side of a closed H5 low. This feature should produce another round of showers and thunderstorms around dawn, highlighted at KCHS with VCSH from 9-15Z. In the wake of the shortwave, convection placement and timing is more uncertain. Extended Aviation Outlook: Main concern is for periodic flight restrictions from showers and thunderstorms, especially each afternoon and evening. && .MARINE... Tonight: Enhanced flow along the land/sea interface will dissipate late this evening. Winds will then generally top out around 10 knots through the rest of the night. Seas will average 2-3 feet, peaking around 4 feet in the outer Georgia waters. We will likely again see shower and thunderstorm activity increase across the waters late. Friday through Tuesday: Moderate to high confidence through Sunday night with no significant concerns. However, confidence is low thereafter as the forecast becomes a bit more uncertain starting Monday as much will depend on the evolution of TD #13. Mariners should be alert for the potential for waterspouts along the land breeze each morning through at least the weekend. Rip Currents: Moderate Risk of rip currents for all beaches Friday. Increasing swells could lead to an enhanced risk along the entire coast starting Monday. && .TIDES/COASTAL FLOODING... Astronomical contributions from the new moon and perigee will result in elevated tides (the Perigean Spring Tides) through Friday. Another Coastal Flood Advisory could be needed with the Friday night high tide for the southeast South Carolina coast. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...NED SHORT TERM...RJB LONG TERM...MS AVIATION...NED/RJB MARINE...BSH/RJB TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Des Moines IA
714 PM CDT Thu Aug 20 2020 ...Updated for 00Z Aviation... .DISCUSSION.../Tonight through Thursday/ Issued at 226 PM CDT Thu Aug 20 2020 Summary... Overall, not much to write home about weather wise. Temperatures will continue to slowly march back into the low to mid 90s for highs, but oppressive dew points should remain at bay. Generally low- end precipitation chances will periodically move thorugh the state over the next few days, then remain dry for much of the new work week. Today through Tomorrow Morning... Weak convection in SE South Dakota should generally continue to wane/struggle, leaving majority of the area dry as we move into the evening hours. A few more scattered showers and storms continue to appear possible overnight as an arm of the 850mb LLJ works into W/NW Iowa. Earlier runs of the HRRR were a bit more robust with showers/storms tonight, though sub-severe, while more recent runs have backed off but still depict a few showers. Overall, of little to no consequence. Have introduced low end POPs over much of NW Iowa and portions of W and C Iowa overnight. Tomorrow Afternoon through Sunday... As shortwaves continue to crest the western CONUS ridge and work into the Plains, they will predominantly split around the state. With weak flow overhead, the shortwaves will slide southward along/west of the Missouri River and/or southeastward across the Dakotas and Minnesota. As a result, northern Iowa will see the best chances for any showers/storms as a potent shortwave works into and through central and southern Minnesota Friday night into Saturday. Much more than occasional lightning will be hard to come by with relatively weak CAPE and support for any organization. As broad surface high pressure works in behind the shortwave, a weak boundary will work into and across the state late Saturday through Sunday. NBM has been slow to pick up on scattered showers/storms along the boundary as it moves through, so have introduced POPs 06-12z Sunday, and may need to be extended into the 12z-18z time frame. Once again, nothing more than nuisance storms with support for organization lacking. Monday through Thursday... An overall flattening of the upper level pattern to weak riding will prevail during the week, pushing any chances for showers/storms away through at least the middle of the week. Additionally, temperatures will continue to warm, peaking into the low to mid 90s. With oppressive dew points remaining at bay, heat index values will generally be at or within a degree or two of the air temperature. Toward the end of the week, flagship ECMWF/GFS models depict a stronger upper wave and surface low moving across Canada, eventually dragging a cold front and shower/storm chances into the region. && .AVIATION.../For the 00Z TAFS through 00Z Friday evening/ Issued at 706 PM CDT Thu Aug 20 2020 VFR conditions with light south/southwesterly winds will continue through the TAF period. Slight chances remain for KFOD (and a lesser extent KMCW) to see a scattered shower or two during the overnight hours as the LLJ picks up, but have left mention of rain out of the TAF due to low confidence and any precipitation that does occur would likely be isolated. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Curtis AVIATION...KCM
Area Forecast Discussion
National Weather Service Grand Junction CO
917 PM MDT Thu Aug 20 2020 .UPDATE... Issued at 906 PM MDT Thu Aug 20 2020 Still some outflow boundaries causing some gusty winds across the area but these should die down over the next hour or two. Convection has ended, and with it, the chance for any new storms so the Red Flag Warnings for dry lightning has been allowed to expire. Smoke will continue to plague areas south of both the Pine Gulch and Grizzly Creek fires overnight. Not much relief in sight as far as the smoke is concerned as the latest HRRR smoke guidance is suggesting smoke from the California fires will be pulled into our region tomorrow evening reaching the northern valleys just after sunset. We shall see. && .SHORT TERM...(Tonight through Friday night) Issued at 330 PM MDT Thu Aug 20 2020 Morning accas across the north along with a shortwave passing through has acted on mid level moisture and instability to produce isolated to scattered thunderstorms as expected. Most of this convection has been over the high terrain with a few cells already tracking over the Pine Gulch and Grizzly Creek Fire areas. The morning sounding indicated the sub-cloud layer is very dry below 450 mb, so not expecting much in the way of significant wetting rain with these cells. Reports have indicated that some small hail has fallen in a few of these cells with brief light rain reaching the ground. Rain is enough to wet the pavement in some of the higher country but very brief in duration. The fire areas will continue to be closely monitored but with so much dry air entrainment in the low levels, don`t anticipate much is reaching the ground. The NAM Nest is continuing to indicate some more robust outflow winds arriving early this evening as these storms collapse and the flow shifts from west to northwest and then north overnight. Outflow winds could gust upwards of 45 mph, so this will need to be watched as it can lead to extreme and erratic fire behavior over existing fires. This wind shift may also end up bringing smoke back into areas to the south of these fires and along I-70 as the drainage winds kick in and transport the smoke down valley. So, we could be waking up to another round of ash fall and smoke if the outflow winds and wind shift comes to fruition. Dry thunderstorm threat should end late this evening around or after sunset for most areas. A couple areas to watch for are the Pine Gulch and Grizzly Creek Fires though as any outflow boundaries interacting with the heat of the fire could result in nocturnal convection as seen a few nights ago. Red Flag Warning continues until 9 pm this evening, but evening shift will have to monitor conditions if it looks like the threat will continue into the evening. High pressure shifts southwest of the area and builds allowing for drier northerly flow to take hold on Friday. The chance for thunderstorms appears much less than today, so only anticipate very isolated storms over the high terrain. For the majority of areas, it will be another hot and dry day with perhaps a bit more hazy to smoky conditions due to the northerly wind shift. .LONG TERM...(Saturday through Thursday) Issued at 330 PM MDT Thu Aug 20 2020 Hot and mostly dry period looks to remain in place this weekend as the ridge of high pressure builds back to the southwest Saturday and shifts overhead by Sunday. Some recycled moisture may result in isolated storms over the higher terrain but otherwise, expecting mostly dry and hot conditions to prevail as no discernible forcing is moving through the CWA during this period and ensemble guidance is indicating a fairly strong ridge dominating overhead. Triple digit heat and near record high temperatures appear to be the norm for many lower valleys of eastern Utah and west-central Colorado this weekend into early next week. Some hope for moisture appears to be on the horizon heading into next week. Remnants from currently named Tropical Storm Genevieve off the southern tip of the Baja in the eastern Pacific looks to track northward along the western California coast late Sunday and gets absorbed a bit in the flow as a Pacific Northwest low pulls it northeast into the Intermountain West by Monday. Another shortwave trough will approach the west coast as this happens, allowing the high pressure ridge to shift eastward enough to allow sub-tropical moisture to increase from the southwest early next week. The initial onset of moisture looks weak late Sunday into Monday with the ECMWF quite a bit drier. However, ensemble model guidance is showing signs of the ridge breaking down by Tuesday and Wednesday, which presents our best chance of seeing decent moisture in the form of wetting rains. Precipitable water values by Tuesday look to reach the 0.75 to 1.0 plus range for much of the area. While this moisture is much needed due to the persistent heat, drought and ongoing wildfires and smoke impacts, this also poses an elevated concern for potential flash flooding on any burn scars, especially for areas recently burned and still burning like the Pine Gulch and Grizzly Creek fires. It would only take a couple tenths of an inch of rain in a short period of time to cause impacts on these hydrophobic soils, so not much. Time will tell though as models looking this far out have had a tendency to be more aggressive with the moisture. Models also don`t appear to be resolving the significantly drier low levels due to the persistent heat and severe drought, so while the mid levels may be sufficiently saturated, this has more often than not resulted in more gusty outflow wind potential and lightning than wetting rain. It usually takes a few days for the lower atmosphere to completely saturate after the initial onset of moisture, in order to produce significant wetting rains. This potential is something to be aware of though as we head into the early to mid week timeframe. However, a more conservative approach is the best forecast at this time until details come into greater focus and if models remain consistent as we head closer to this timeframe. If this pans out, increased clouds and showers will provide some relief from the triple digit heat with highs in the 80s for the higher valleys and 90s for many lower valleys. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 539 PM MDT Thu Aug 20 2020 Plenty of outflow boundaries are bringing variable and gusty winds to many TAF sites this evening. Wind speeds vary from 20 to 30kts with a few spots reaching near 40kts. As the sun sets, convection will also weaken which will cause the winds to subside. A few showers and storms have formed and may affect KEGE, KASE, and KHDN but by 03Z, most convection will end. Skies will lift and clear out overnight though smoke may reduce visibility for KEGE, KRIL, and KGJT. && .FIRE WEATHER... Issued at 330 PM MDT Thu Aug 20 2020 The Red Flag Warning remains in effect for dry thunderstorms across much of the forecast area. Mid-level moisture is generating isolated to scattered thunderstorms over higher terrain this afternoon and they are expected to continue into the evening. Given the lack of moisture in the near surface layer, many of these storms will produce little to no rain. Fuels are extremely dry so there is a high likelihood of new fire starts with today`s storm activity. In addition, strong outflow winds to 45 mph will spread fires already burning in unpredictable directions potentially resulting in extreme fire behavior. Thunderstorm chances are much lower Friday into the weekend, but hot and dry conditions will remain. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ UPDATE...TGR SHORT TERM...MDA LONG TERM...MDA AVIATION...TGR FIRE WEATHER...TGJT
Area Forecast Discussion
National Weather Service Goodland KS
947 PM MDT Thu Aug 20 2020 .UPDATE... Issued at 941 PM MDT Thu Aug 20 2020 A broken line of storms have begun to form ahead of the outflow approaching from the west. This line is roughly along Highway 27. Once the outflow moves underneath the storms, am doubtful they will last much longer. At this time am not sure if there continue to be a line of storms ahead of this outflow boundary or not as it moves east across the forecast area. The best upper level support for storms will be along the Highway 27 corridor. Severe wind gusts are still a threat. However, storms have formed in much better effective shear, so this may make them more suitable to produce larger hail. Mid level lapse rates are still around 7.5, which is not ideal. In addition, storms won`t have much time to strengthen before the outflow moving east cuts them off. Therefore confidence of large hail occurring is still on the low side. UPDATE Issued at 829 PM MDT Thu Aug 20 2020 Updated forecast to reflect latest trends in radar and near term data. Storms that have been moving south in Nebraska have been fading over the last hour or so. RAP sounding for McCook has begun to show the potential for an elevated thunderstorm around midnight. However other near term data has not been supporting that, so confidence is low this will occur. Meanwhile am thinking the storm activity over East Central CO will continue to move south of the forecast area. There is an outflow boundary moving east from the storm, so will be curious if it triggers any storm development when it runs into the LLJ near the stateline. There may be isolated storms which move in from the northwest late tonight. However the current storms to the northwest seem to be fading. Just incase these do manage to survive, have left a mention of isolated chances in for East Central CO. Continue to think the main threat with the strongest storms will be wind gusts of 60 MPH. && .SHORT TERM...(This evening through Friday) Issued at 145 PM MDT Thu Aug 20 2020 Next shortwave trough rounding the western ridge will arrive this evening accompanied by widely scattered showers and thunderstorms. Environment will be similar to yesterday, with a slight uptick in MLCAPE, while DCAPE and effective shear are more or less the same. Expecting wind to be the primary hazard with gusts up to 65 mph possible with stronger storms. Despite a gradual decline in coverage through the evening, isolated showers/storms may persist through the overnight before ending by 12z Saturday. Low temperatures will be in the 60s. Upper ridge nudges into the area on Friday with rising heights. A few of the CAMs suggest isolated thunderstorms developing at peak heating along a surface trough from northeast Colorado into central Nebraska, moving east and weakening Friday evening. Weak instability remains a limiting factor, but cannot rule out an isolated severe wind gust with any storm that develops. Temperatures will warm into the middle to upper 90s and lows Friday night in the 60s again. .LONG TERM...(Saturday through Wednesday) Issued at 131 PM MDT Thu Aug 20 2020 The long term period will see the continuation of the warm and dry pattern we have seen this past week. On Saturday the upper level high will be centered over Arizona with the ridge over majority of the western CONUS. The cut-off low is expected to slowly move east towards the Tennessee Valley setting up northerly flow across the Central Great Plains. The ridge will continue to move east into next week centering over the High Plains region by Tuesday. As the high moves into the Four Corners region early next week, the ridge will extend into central Canada. Wednesday, a shortwave trough will move east along the northern extent of the ridge in Canada sending a cold front south. Looking at current guidance, it doesn`t seem like the cold front will make it`s way into the Tri-State area. High temperatures will be in the 90s each day. Low temperatures are expected to be in the 60s. Dry conditions are expected through the period. There is some concern for fire weather during the long term period. Relative humidity values are expected to drop down into middle to lower 20s each day in eastern Colorado. Sunday through Tuesday the concern is little higher as the low humidity levels will be co-located with southerly wind gusts approaching 25 mph. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 514 PM MDT Thu Aug 20 2020 VFR conditions forecast for the 0z TAFs. Confidence of storms moving near a TAF site for the evening is low enough to not put in the TAFs. If one of the sites were to have storms move nearby, am thinking it would be KMCK during 3-4z. Otherwise winds will be on the light side through the period. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...JTL SHORT TERM...024 LONG TERM...KMK AVIATION...JTL
Area Forecast Discussion
National Weather Service Midland/Odessa TX
620 PM CDT Thu Aug 20 2020 .DISCUSSION... See 00z aviation discussion below. && .AVIATION... VFR conditions are expected for the next 24 hours. Winds will mostly be out of the southeast for HOB, INK, MAF, and FST. Winds will be somewhat variable for CNM and PEQ. && .PREV DISCUSSION... /issued 245 PM CDT Thu Aug 20 2020/ DISCUSSION... Not much change to the current forecast. WV imagery shows the ridge centered over ern AZ this afternoon, maintaining meridional flow over West Texas and Southeast New Mexico. The latest HRRR repeats last night`s scenario in a shortwave developing convection in NE NM late this afternoon, and drifting down into SE NM overnight. Friday, convection looks confined to the higher terrain during the day. Friday night, models are in pretty good agreement in bringing a shortwave through the ern CWA, especially the SREF, which may combine w/convection out west in the mtns to provide the best chance of convection this forecast. That said, chances won`t be anything to write home about. Over the weekend, the ridge will meander NE, settling over the Four Corners by 00Z Mon, and leaving West Texas and Southeast New Mexico high and dry into the extended. Regarding temperatures, Fri still looks to be the hottest day, w/probably a few Heat Advisories needed for the higher elevations. Thicknesses drop off over the weekend as the ridge moves to the Four Corners, w/most locations seeing highs below the century mark by Mon afternoon. Temps should remain above-normal, but cooler than they have been lately, into the extended. && .PRELIMINARY POINT TEMPS/POPS... Big Spring 73 101 73 99 / 0 10 20 10 Carlsbad 72 101 73 101 / 10 10 20 0 Dryden 75 104 75 100 / 0 0 20 20 Fort Stockton 75 102 73 100 / 0 10 10 10 Guadalupe Pass 72 95 70 93 / 10 20 30 0 Hobbs 70 98 69 98 / 0 10 10 0 Marfa 64 98 65 94 / 0 20 30 10 Midland Intl Airport 74 100 74 99 / 0 10 10 10 Odessa 75 101 74 100 / 0 10 10 10 Wink 74 104 74 102 / 0 10 10 0 && .MAF WATCHES/WARNINGS/ADVISORIES... NM...None. TX...None. && $$ 99/99/99
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Area Forecast Discussion
National Weather Service Tucson AZ
800 PM MST Thu Aug 20 2020 .SYNOPSIS... Expect storm coverage and chances to increase into the weekend. High temperatures will moderate through the weekend, but will still be 2-5 degrees above normal. Next week storm chances decrease and temperatures climb back up to near record levels. && .DISCUSSION... An active monsoon pattern brought several thunderstorms across the forecast area this afternoon and evening. A few of these thunderstorms were severe, with a few reports of wind damage in Drexel Heights and Rio Rico. There were also multiple reports of visibility reductions related to dust in Tucson...before the complex transitioned to more of a hydrologic concern. As of this writing, flood advisories and warnings have been posted across much of Tucson with slow-moving thunderstorms moving across the city. Showers and thunderstorms could continue into early morning before dissipating. && .AVIATION... FEW-SCT clouds 10k-15k ft MSL increasing in coverage through this afternoon as SCT TSRA/SHRA develops. This activity continues into the evening hours, dissipating overnight. Surface wind gusts to 40 kts with strongest TSRA along with MVFR CIGS/VSBYS and mountain obscurations. Otherwise, winds WLY-NWLY this afternoon 10-15 kts with gusts to 25 kts, becoming light and variable later in the evening. Similar wind regime returns tomorrow afternoon with another round of SCT TSRA/SHRA. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... && .PREV DISCUSSION... /issued 245 PM MST Thu Aug 20 2020/ .SYNOPSIS...Expect storm coverage and chances to increase today into the weekend. High temperatures will moderate through the weekend, but will still be 2-5 degrees above normal. Next week storm chances decrease and temperatures climb back up to near record levels. && .DISCUSSION...Gulf surge continues this afternoon, thanks to Tropical storm Genevieve, with Yuma Vad wind profile showing southerly winds up to 5k deep with dewpoints in the 60s to lower 70s across Yuma county. Closer to home dewpoints were in the 40s to lower 60s. PW values ranges from 0.90" near the AZ/NM border to 1.5" over far western Pima county. Interesting CAM solutions with the 20/12z UofA WRFNAM the most active with line of thunderstorms, some severe, producing areas of blowing dust, moving propagating W-SW across the area this evening and continuing into the overnight hours out west while the WRFGFS was the least active. The most recent runs of the HRRR was in between, still active but not like the WRFNAM. SPC has most of the area under marginal risk of severe storms for strong gusty winds. Localized heavy rain also a threat. Friday: Tropical Storm Genevieve will be weakening as it moving west of the Baja Spur. For southern Arizona, enough moisture will be around for isolated to scattered showers and thunderstorms under easterly flow aloft with upper high near the 4 corners. Weekend: Isolated to scattered showers and thunderstorms in the afternoon and evening. What will be noticeable will be the cooler daytime temperatures, especially Saturday, versus what has been occurring this month. Enjoy it for it won`t last long. There is chance, around 33%, that the Tucson airport could record the first sub-triple digit high of the month. Fingers crossed. Next week: We heat up again with record or near record highs with heat risk issues raising its ugly head once again. Likely will need another round of Excessive Heat Warnings for most of the week. Thunderstorm activity each day will be isolated at best. && .AVIATION...Valid through 22/00Z. FEW-SCT clouds 10k-15k ft MSL increasing in coverage through this afternoon as SCT TSRA/SHRA develops. This activity continues into the evening hours, dissipating overnight. Surface wind gusts to 40 kts with strongest TSRA along with MVFR CIGS/VSBYS and mountain obscurations. Otherwise, winds WLY-NWLY this afternoon 10-15 kts with gusts to 25 kts, becoming light and variable later in the evening. Similar wind regime returns tomorrow afternoon with another round of SCT TSRA/SHRA. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Due to a surge of moisture, expect broader coverage of afternoon/evening showers and thunderstorms starting today into early next week. The best chance for widespread precipitation occurs this weekend. 20-foot winds generally remain less than 15 mph outside of any thunderstorm gusts which could reach upwards of 40 mph. Minimum relative humidities increase to 25-30 percent across the valleys Friday through Sunday along with good overnight recoveries. && && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ Public...Dang Aviation...Dang Fire Weather....Zell Visit us on Facebook...Twitter...YouTube...and at