####018006090#### FXUS66 KPDT 101000 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 300 AM PDT Fri May 10 2024 .SHORT TERM...Today through Sunday night … A ridge of high pressure continues to dominate over the region and will continue through the majority of the weekend. A weak shortwave will make its way across the upper level ridge breaking it down slightly bringing more seasonable temperatures back to the forecast area. Dry conditions will dominate even under the influence of shortwave makes its way across the WA Sunday evening. Models are in firm agreement with the upper level ridge over the forecast area with an upper level low still over the Four Corners remaining in tact through Sunday evening. This synoptic pattern has caused and will continue to cause the ridge to strengthen into what is called a Rex blocking pattern. This will bring dry and warming conditions through Saturday with temperatures reaching 15-20 degrees above normal by Saturday. High confidence in the forecast for temperatures cresting 90s with raw ensembles showing a 80% probabilities for the Columbia Basin and adjacent valleys, 60-70% for the lower Columbia Basin and the foothills of the Blues and the Gorge seeing temperatures in the mid to upper 80s. Sunday evening the models begin to show a weak shortwave making its way across the upper level ridge. This will cause a slight breakdown shifting the upper level flow to a more westerly component and increasing the winds, cooling the temperatures slightly and bringing a less 20% probabilities of rain to the far northern portion of WA Cascades. Otherwise, the remaining portions of the region will remain under dry and warm conditions with over 90% of raw ensembles showing the temperatures to be in the mid to upper 80s across the majority of the CWA with the higher elevations in the mid 60s to 70s. Winds are expected to increase as the cross Cascade gradient increases with the shift of the upper level flow. Ensembles show a greater than 60% probability of the lower Columbia Basin seeing sustained winds of 25 mph, 75-85% for the Simcoe Highlands and the Gorge, and over 90% for the Kittitas and Yakima Valleys. With the rise in temperatures, guidance has begun to pick up on a slight heat risk for Saturday through portions of the Columbia Basin. If you are outside on Saturday enjoying the warmth, please be mindful and wear sunscreen, drink plenty of fluids and remember that the rivers will be fast flowing and still dangerously cold. Bennese/90 .LONG TERM...Monday through Friday...Model agreement looks good through the first of the week with a weak shortwave passage Monday followed by the rebuilding of the ridge in the wake of its departure. However, from midweek onward uncertainty increases in both the ensemble and deterministic models as to whether the ridge will persist or a westerly flow develops and allows another trough passage late in the week. 00Z deterministic models highlight this uncertainty by having flipped in the past 24 hours. The GFS now builds a ridge over the western USA while the EMCWF has a trough passage occurring on Thursday which is the exact opposite from yesterday. Ensemble models also showing the differing solutions but to a lesser degree in the amplitude of the trough on Thursday. Overall this is causing the NBM to play middle of the road forecasting. Example, Thursday high temperatures probabilities range from mid 60s to mid 80s with actual forecasted highs in the mid 70s. Same for the chance of precipitation as it could either be dry or chance of precipitation, the NBM splits the difference with a slight chance of precipitation. So, current extended forecast will see cooler temperatures on Monday by 5 to 10 degrees as the trough passage ushers in some cold air advection. This produces some breezy to windy conditions which could reach wind advisory levels across portions of the Lower Columbia Basin. Could also see a few showers along the crest of the Cascades. Tuesday will see a reduction of the winds to just breezy and overall dry conditions as the trough departs and ridging begins to rebuild over the region. Beyond this point the high degree of uncertainly brings forecast confidence level to low. Will hold onto the NBM's middle of the road temperature forecast but have under cut the NBM POPs restricting it to just a slight chance of showers along the Cascade crest late Wednesday through Friday. && .AVIATION...06z TAFS...Little to no aviation impacts through the TAF period. Latest satellite imagery shows a few swaths of high clouds drifting from the northeast over eastern OR and a few isolated areas of lingering stratocu. High confidence (>80%) in limited sky cover over the basin and lowlands through the TAF period. Elsewhere, diurnal mountain cu development is expected tomorrow afternoon with good agreement seen in HREF and hi-res guidance. Current thinking is areas with the best chance for this will include the higher terrain of central OR, Ochocos, John Day Highlands, and eastern mountains with bases >6 kft and higher. Otherwise, an upper-level ridge aloft with a weak surface pressure pattern will prevail prompting light winds and breezes through the period. && .PRELIMINARY POINT TEMPS/POPS... PDT 79 51 84 55 / 0 0 0 0 ALW 82 55 87 60 / 0 0 0 0 PSC 85 55 91 57 / 0 0 0 0 YKM 85 52 90 52 / 0 0 0 0 HRI 85 53 90 58 / 0 0 0 0 ELN 84 53 87 54 / 0 0 0 0 RDM 78 46 82 47 / 0 0 0 0 LGD 76 49 80 50 / 0 0 0 0 GCD 77 48 81 49 / 0 0 0 0 DLS 86 57 90 57 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...90 LONG TERM....91 AVIATION...80 ####018005719#### FXUS66 KLOX 101004 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 304 AM PDT Fri May 10 2024 .SYNOPSIS...09/214 PM. A quiet weather pattern is expected through early next week with near normal temperatures and no rain. Increasing night and morning low clouds are expected across coast and valleys as onshore flow increases. Mostly minor day to day changes in temperatures are expected through Sunday, then cooling possible Monday and Tuesday. && .SHORT TERM (TDY-SUN)...10/302 AM. Not much in the way of weather excitement on tap as we enter peak marine layer season. A retrograding upper low will move to the SW and will be over Las Vegas by this afternoon. It will stay in this location through Saturday morning before heading east. Onshore flow and a weak eddy brought plenty of low clouds to the csts/vlys south of Pt Conception, but there was not enough of a N push to get the clouds around the point and up into the Central Coast. Decent onshore flow to the north and east will prevent an early burn off, but skies should be clear by noon at the latest. Max temps today will fall 3 to 5 degrees across the coasts but mtns and interior will see 2 to 4 degrees of warming. The cyclonic flow from the low will combine good differential heating to the mtns and will destabilize the atmosphere over the mtns. The flow into the mtns, however, will be from the NE and will be very dry (PWATs ~.2") and this will greatly limit the convective threat. Still a non zero but less than 10 percent chc of convection tomorrow but see the far more likely scenario being some afternoon CU development. The low clouds will make it to the Central Coast tonight as well as the rest of the csts/vlys south of Pt Conception. Saturday will be similar today with similar clearing times and temperatures. A little ridge slides into the area on Sunday. The ensembles show that this will reduce the low cloud coverage in the morning but with the onshore flow still increasing this forecast may turn out to be a little optimistic. Rising hgts will lead to rising temps and most areas will end up 1 to 3 degrees warmer compared to Saturday. While the coasts and vlys will have near normal temps the mtns and the interior will be 5 to 10 degrees above normal. .LONG TERM (MON-THU)...10/1234 AM. A weak upper low will move over the area from the west during the xtnd period. It will usher in a prolonged period of May Grey. At the sfc there will be strong (7-9 mb) onshore flow to the east and moderate onshore flow (5-6 mb) to the north. The lowering hgts and cyclonic turning will combine with onshore flow to bring extensive night through morning low clouds and fog to the csts and most of the vlys. The strong onshore flow will result in slower clearing and may bring no clearing to a few beaches. The cyclonic turning aloft may also provide just enough lift to create some morning drizzle esp along the foothills. The strong onshore push to the east will result in breezy conditionsacross the mtns and interior with low end advisory level gusts possible in the afternoon. Max temps will cool both Mon and Tue and then change little on Wed and Thu. Max temps will be 2 to 4 degrees blo normal across the csts/vlys but will be 3 to 6 degrees above normal across the mtns and the interior. && .AVIATION...10/1004Z. At 0800Z at KLAX, the marine layer was 2100 feet deep. The top of the inversion was at 3200 feet with a max temperature of 19 C. Overall, moderate to high confidence in 12Z TAF package. Timing of dissipation of CIGs this morning for coastal/valley sites could be +/- 2 hours of current forecast. For tonight, high confidence in return of CIG/VSBY restrictions for sites south of Point Conception and moderate confidence for KSMX. However, only moderate confidence in timing of return. KLAX...Moderate confidence in 12Z TAF. Timing of dissipation of MVFR CIGs could be +/- 2 hours of current 20Z forecast. For tonight, high confidence in return of MVFR CIGS, but only moderate confidence in timing (could be +/- 2 hours of current 02Z forecast). No significant easterly wind component is expected. KBUR...Moderate confidence in 12Z TAF. Timing of dissipation of MVFR CIGs could be +/- 2 hours of current 17Z forecast. For tonight, high confidence in return of MVFR CIGS, but only moderate confidence in timing (could be +/- 2 hours of current 06Z forecast). && .MARINE...10/304 AM. For the Outer Waters, moderate to high confidence in current forecast. Today through Saturday night, high confidence in winds and seas remaining below Small Craft Advisory (SCA) levels. For Sunday through Tuesday, there is a 40-60% chance of SCA level winds. For the Inner Waters north of Point Sal, high confidence in current forecast as winds and seas are expected to remain below SCA levels through Tuesday. For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Today through Tuesday, winds and seas will remain below SCA levels for most areas. The only exception will be the western half of the Santa Barbara Channel where there is a 30-40% chance of SCA level winds Sunday night and Monday. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...Rorke AVIATION...RAT MARINE...RAT SYNOPSIS...MW weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox ####018005676#### FXUS63 KDDC 101004 AFDDDC Area Forecast Discussion National Weather Service Dodge City KS 504 AM CDT Fri May 10 2024 .KEY MESSAGES... - A dry and mild end to the workweek across southwest Kansas. - Forecast trend is becoming more favorable for a wet weather pattern this weekend and next week. - Probabilities of 0.5 inch of rain or more from late Saturday through mid Monday are increasing. && .SHORT TERM /THROUGH SATURDAY/... Issued at 200 AM CDT Fri May 10 2024 06Z surface observations and RAP upper air analysis has a large upper low centered in Utah with west to southwest winds aloft moving through the central plains. An area of PVA and 700 mb shortwave has led to some light rain showers mainly in eastern New Mexico and southeast Colorado. As the rain moves east with lesser moisture at the surface we are just seeing a band of mid level clouds moving into far western Kansas. Boundary layer winds continue out of the north to northeast as a surface high in central Wyoming and the clockwise flow around it is keeping the winds northerly. For today the surface high will slide into eastern Colorado and this will lead to generally light north winds. Periods of mid to high level clouds will move across southwest Kansas as we should see some weak PVA and 700 mb lift across eastern Colorado and southwest Kansas. Highs will reach into the 70s. Tonight we shouldn't see much movement with the upper low as it will still be around the Utah-Arizona border. However southwest winds at 500-700 mb and winds turning east to southeast in west Texas will increase the moisture and upslope flow that we should start to see a band of light rain develop in these regions. Overall Kansas should stay dry as the winds will stay northerly and the bulk of the higher surface moisture will stay to the south. Clouds will be on the increase during the overnight hours and we should see overcast skies in far southwest Kansas by morning. Saturday should start out dry and the latest trends in the short and medium time framed models have the 700 mb low and increasing moisture reaching far southwest Kansas after the noon hour. POPs should increase after 18Z and by 21Z we will have 40-50% POPs for areas from Liberal to Syracuse on west. Low amounts of CAPE will negate any severe threat but there will be enough energy for a few embedded thunderstorms. We could see rainfall totals approaching 0.10 inch in the far southwest by sunset as Euro and GEFS ensembles have 40-70% probabilities of 0.10 inch at Elkhart by 00Z. More details on the widespread rain event for southwest Kansas will be detailed in the long term. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Issued at 219 AM CDT Fri May 10 2024 Medium time frame models show widespread light rain overspreading southwest Kansas during the evening and early overnight hours from Saturday night into Sunday as the main 700 mb lift goes from southwest to northeast. Rainfall amounts should be around 0.10 of inch with the initial first round of rain as probabilities of 0.10 are pretty high west of highway 83 at 50-80% and lesser as you go east at 30-50%. This particular system will bring waves of rain as the initial forcing will weaken after midnight and we should see a break in the rain. Sunday morning we should see another round of rain develop as the 700 mb low moves into eastern Colorado and stronger PVA will lead to a deepening low. With greater forcing and ample moisture (forecast dewpoints in the mid 50s) we will see rain increase in coverage and intensity during the day and by mid to late afternoon 6 hour forecast rainfall totals of 0.10-0.50 inch become quite common across southwest Kansas. EPS has near 100% probability of 0.10 inch during the day and 0.50 inch is 50-70% from late afternoon Sunday through Sunday night. This lines up with the closed low slowly moving into Kansas by early Monday morning and the upper level winds are still trending lighter on the south side of the low which would suggest the eastward propagation of the low will be slow. This would be good news for extending amounts of gentle rain across southwest Kansas as the forcing and moisture should keep rain around southwest Kansas at least through noon Monday and perhaps into the afternoon with some rain developing on the backside of the low from Liberal to Hays on east. Total QPF at this point is approaching widespread 0.75-1 inch of rain for southwest Kansas. Severe weather threat will be low however there will be enough energy for a few embedded thunderstorms. Tuesday will be a dry day and then mid week chances of rain increase again (30-40% POPs) on Wednesday. An upper level trough and 700 mb closed low will come out of the northwest and similar to the first system the upper level winds won't be very strong so a slower propagation to the east is the trend at this point. This will keep rain chances into Thursday. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 504 AM CDT Fri May 10 2024 Near 100% probability of VFR flight category for all terminals during the time period. A band of mid level clouds will lower ceilings to around 15 kft through the overnight and mid morning hours. Winds in general will be 5-12 kts sustained with a few gusts as high as 15 kts in the afternoon. && .DDC WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Tatro LONG TERM...Tatro AVIATION...Tatro