Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/25/24


Area Forecast Discussion
National Weather Service Denver/Boulder CO
753 PM MDT Wed Apr 24 2024 .KEY MESSAGES... - Slight Risk of severe thunderstorms Thursday, east of a line from Sterling to Akron, including large hail, damaging winds and isolated tornadoes. A marginal risk south and west of this area. - Cool and unsettled Friday into the weekend, with accumulating moderate snowfall in the mountains, widespread rain showers over the plains && .UPDATE... Issued at 742 PM MDT Wed Apr 24 2024 One thunderstorm is still doing its best to persevere in a generally hostile environment along the CO/NE border this evening, with just a couple of weak, high-based showers noted elsewhere. Not expecting much overnight tonight with just some chance PoPs in the far northeast corner overnight. As better moisture streams into the area overnight, there should be some development of stratus/mist in the eastern plains, along with some patchy fog. Have also added a little bit of fog into the grids across southern Weld county into the DIA area where guidance the HRRR has hinted at this the past few cycles. Otherwise, only some minor adjustments were made to the forecast grids this evening. The previous forecast was largely in good shape. && .SHORT TERM /Through Thursday/... Issued at 324 PM MDT Wed Apr 24 2024 Northern border shower activity is running a couple hours ahead of schedule. The edge of the drier air is lifting northward and there does appear to be more stable air upstream west of the Front Range, so the end of this over the mountains may also be faster, in the early evening or sooner. On the plains the showers will be encountering the south winds that could keep them going longer, although there`s not really more moisture out there yet. Further south, there`s just a slight chance of very light showers, we`ll probably just have virga. A surface low will develop early Thursday on the broad shear zone on the edge of the southerlies on the plains, probably starting near Denver but then drifting eastward. Moisture will be increasing in the southerlies tonight. There is a stratus deck from western Kansas into Texas that will advect into the northeast Corner of Colorado tonight, and it will likely develop westward late tonight. The increase in moisture is gradual at first, but richer air will arrive by Thursday morning. Between the wind speeds and the existing stratus deck, it looks like this will probably be off the ground instead of producing fog. Thursday`s severe potential is complicated by this cloud deck and the fact that the moist air is considerably cooler and should be capped, at least for most of the day and possible into Thursday evening. So the question becomes where there will be both enough moisture and heat, or enough convergence to break the cap. If we can get convection rooted in that moisture, it`s a pretty favorable supercell environment with mainly a large hail threat. I see two severe scenarios, both of which are questionable, and both of which could happen together. One is on the west edge of the better moisture, extending on the north side of the surface low, probably across northeast Weld, or possibly Logan or Morgan counties. This area could be the sweet spot which has increased moisture but still gets warm enough. While CAPEs in this area won`t be as high as further east, it`s still a supercell environment and this area might have the best potential for tornadoes early in the life of the storm with a more backed low level wind field. This would most likely be for a couple hours during the late afternoon. The second scenario would be that the dryline convergence is enough to overcome a weak cap. Most of the convective allowing models we`ve seen like this idea, and insist on it happening in the late afternoon. This seems like it might be too fast given the model soundings we`ve seen which are mostly still pretty cool in the moist air in the late afternoon. It may take increasing convergence along with peak heating/moistening into the evening if that`s going to happen. This would be more likely on the east side of the low, east or northeast of Akron, and a few hours later. In this case also, the severe threat is probably just a couple of hours and then we`re dealing with elevated convection over the cooler moist air. Behind the low during the afternoon, we`ll have a relatively dry environment, though still probably enough moisture/instability for some higher based weaker storms. The bulk of that may wait for evening as well with some cooling aloft and moisture advection from the north/northeast behind the low. For now, minimal changes have been made as this was the general forecast scenario we`ve had going. The main question remains the heating of the moist air late Thursday. && .LONG TERM /Thursday night through Wednesday/... Issued at 324 PM MDT Wed Apr 24 2024 As the backside of the cyclone brings northwest flow to the northeastern plains, the threat of severe storms could continue through midnight. Counties such as Logan, Sedgwick, and Phillips have the greatest chance of additional severe storms while elsewhere instability decreases overnight. Although a nocturnal threat of severe weather isn`t new, those areas listed above should remain weather aware Thursday evening until midnight. Light snow prevails throughout elevations above 9k ft overnight into Friday morning. With increasing snow and mid-level cloud cover across the region Friday, this forecast package includes an adjustment to afternoon highs as well Friday night lows. The next trough axis approaches Utah quickly but Friday afternoon may become a break in additional precipitation before the next shortwave trough enters western Colorado. Therefore, kept a chance of scattered PoPs (40-50%) along the urban corridor Friday afternoon. WPC Super Ensemble QPF fields display at least 0.50-0.75 inches over majority of the CWA Friday night into Saturday morning. It is likely areas across the mountains could receive periods of light to moderate snowfall. If traveling to mountain passes, prepare for winter travel conditions. Snowfall rates could approach 1-2 inch/hr above 10k ft especially by Saturday afternoon. Heavy rainfall will likely occur across the lower elevations Saturday as precipitable water values 0.7-1 inches. Numerous showers continue through Sunday morning. It is possible these showers will remain less convective as daytime heating will be limited. Our region will transition into zonal flow by Monday and weak lingering mid-level moisture could lead to isolated showers throughout Jackson and Grand counties. By Tuesday, dry conditions continue across the region. && .AVIATION /00Z TAFS through 00Z Thursday/... Issued at 524 PM MDT Wed Apr 24 2024 VFR conditions should prevail through the TAF period. A broad Denver cyclone has been observed again this afternoon with the main boundary/wind shift located between BJC and DEN. Current expectation is for this to remain fairly steady-state through the next couple of hours, and then gradually weaken later this evening as drainage flow establishes. Next forecast challenge comes early Thursday as models hint at some potential for a brief period of fog or very low stratus tomorrow at DEN. BUFKIT profiles would favor fog, but the majority of guidance keeps this just north/northeast of the field in southern Weld county. Finally, there`s still some uncertainty in the winds and overall convective/shower potential Thursday afternoon, with DEN reasonably close to the dryline. Will need to re-evaluate with tonight/tomorrow AM hi-res guidance to get a better feel, but a broad period of VCTS/VCSH is likely. Eventually may see some lower cigs develop after 00z as well. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Hiris SHORT TERM...Gimmestad LONG TERM...AD AVIATION...Hiris
Area Forecast Discussion
National Weather Service Dodge City KS
704 PM CDT Wed Apr 24 2024 .KEY MESSAGES... - Severe weather risk on Thursday for areas along and east of highway 83. - Fire weather risk on Thursday for areas along and west of highway 83. - Potential fire and severe weather risk for Saturday as well. && .SHORT TERM /THROUGH THURSDAY NIGHT/... Issued at 103 PM CDT Wed Apr 24 2024 18z obs and RAP upper air analysis shows a widespread cloud deck across southwest Kansas with the last areas of morning convection well to the south and east. 500 mb winds have a ridge across the Rockies with an embedded shortwave developing in the front range and a large closed low still well off the Pacific coast of California. For tonight the position of the longwave trough/upper low should quickly move into the Colorado river basin in the desert southwest which will push the upper level ridge eastward into the central plains. With this we will also see a layer of warmer air in the mid levels with many models showing around 8-10 (C) 700 mb temperatures which will be important to monitor as it will affect our storm chances on Thursday. Ahead of the warm front we should have a 700 mb shortwave coming out of the front range from eastern Colorado through central Kansas and with good moisture advection along the front and wave we should see an area of thunderstorms develop mainly after midnight for areas along and east of highway 83. These storms should move quickly to the east into central Kansas by morning and with low CAPE values forecast this rain and storm should stay below severe limits. Thursday the SPC has put an enhanced risk of severe weather for areas along and east of highway 83. Three things we have been noticing so far that could mitigate the risk is how much thunderstorm outflow/clouds/colder air hangs around from what we get tonight in our eastern zones. Also the warm mid layers at 700 mb will produce a strong cap all across southwest Kansas with the 25th percentile temperatures at 8 (C) and 90th at 9-10 (C) suggesting a >90 % chance of a strong cap. With temperatures in the mid levels that warm we would need the areas with moisture to get to near 90 degrees to break the cap which is not looking promising at this point. Also models are lagging the forcing at 500 mb until well after 00Z to also help break the CAP. Some CAMs have been showing no convection at all however if a storm can break the CAPE the bulk shear and CAPE values would support supercells capable of hail greater than 2 inches and damaging winds. If supercells can stay discrete through 7 pm the low level jet will increase and introduce a tornado threat and we can`t rule out a strong tornado potential. This is what would be call a classic conditional severe weather risk. Fire weather threat west of highway 83 will be the result of a dryline moving in from the west and reaching to the Scott City- Liberal line and southwest winds will be 20-30 mph with relative humidity values falling to below 15%. Thursday night any convection that develops will race to the north and east as the 991 mb surface low moves into southwest Nebraska and the dryline/cool front moves to the east. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 208 PM CDT Wed Apr 24 2024 Friday the low from the surface to 500 mb will move into central Nebraska and will sweep drier air through southwest Kansas. Winds will increase through the day especially for areas along and north of K-96 with wind speeds at 20-30 mph with higher gusts. Saturday will have both severe and fire weather potential in southwest Kansas. Medium range ensemble models have an upper low moving from the four corners region Saturday morning to southeast Colorado by late afternoon. Moisture profiles have the highest levels in central Kansas with the drier air for much of southwest Kansas along and west of highway 283. Elevated to critical fire weather potential is high (>80%) as winds will be out of the southwest at 20-30 mph with higher gusts. Severe weather at this point looks to be mainly along and east of highway 281 with the greater potential more into central Kansas. After Saturday ensemble upper air forecasts go more zonal and we will go dry and warmer for the middle parts of next week. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 700 PM CDT Wed Apr 24 2024 Aviation weather conditions will deteriorate this evening with widespread IFR/LIFR conditions developing particularly in the 09-15Z time frame...later up north toward HYS and earlier down south toward LBL terminal as the warm front lifts north. The forecast at HYS terminal is particularly challenging in that a large cluster of thunderstorms will develop overnight near or just east of HYS, which will likely spread an outflow boundary south across HYS some time in the 09-13Z time frame. This thunderstorm outflow boundary will likely result in an easterly wind (if not slightly northeasterly) and may reach as far as DDC mid-morning, however we will keep winds at DDC out of the south-southeast Thursday morning. HYS will likely remain in the low stratus and IFR/LIFR flight category much of the day Thursday. && .DDC WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from 1 PM CDT /noon MDT/ to 9 PM CDT /8 PM MDT/ Thursday for KSZ061-062-074-075-084-085. && $$ SHORT TERM...Tatro LONG TERM...Tatro AVIATION...Umscheid
Area Forecast Discussion
National Weather Service Goodland KS
813 PM MDT Wed Apr 24 2024 .KEY MESSAGES... - Significant severe weather is possible Thursday for most of the area with the main threats being tornadoes and very large hail. The threat is conditional as a cap could prevent storms from forming. - A Fire Weather Watch and Red Flag Warning is in effect Thursday south of I-70 and west of Highway 25 for low humidity and strong winds. - Blowing dust is also possible Thursday afternoon for near and south of the I-70 corridor. && .UPDATE... Issued at 722 PM MDT Wed Apr 24 2024 Confidence is increasing in overnight convection affecting portions of the east and northeast counties. RAP soundings indicate an increasing environment for strong to marginally severe hail occurring with MUCAPE around 1400 j/kg, effective shear of 40-45 knots, EBWD shear in excess of 40 knots and lapse rates of around 8 C/km which should bring about the potential for hail around quarter size. PWATS are also in excess of 1 inch which would support a very heavy rain threat as well. Would be surprised if flooding becomes a concern due to the antecedent dry conditions along with fast storm motion. However if backbuilding does become an issue than may need to watch this more closely. Confidence also does continue to increase in the potential for a significant severe weather event Thursday afternoon. Virtual all CAMS are now convecting along the dry line during the afternoon hours which is quite the change vs what was seen last night where everything was capped. It appears that the reasoning for this is due to the low stratus being favored a bit further north and east. A slight concern I do have is regarding upper level cirrus potential as RH values in the 400-200mb level do show around 30% RH values during the afternoon hours and signals of cirrus is also seen in RAP soundings. If this is the case this may be one of the many factors that may limit convective initation or sustained of any updrafts. Others are if the CAP is to strong and any potential impact that any outflow from overnight/morning convection may have; especially regarding the tornado potential. Despite all the continued uncertainties that do continue to shadow this event, the potential is there for a few intense supercells with very large hail and perhaps a significant tornado threat as 0-3 SRH values are around 200-225 and 0-1 SRH around 100 and does steadily increase into the later afternoon and early evening hours. Regarding location for tomorrow; have been noticing a slight westward trend with where guidance wants to place the dry line. Similar signs were seen with last week`s severe event where the NAM was the relatively most accurate with the location of the dry line and other guidance were playing catchup. I feel the same thing is again applying in this scenario as well. Reasoning for this may be due to the undoing of soil moisture across the area; yes we have been dry lately but the area is coming off of a wetter past year; SPORT soil moisture also does support this theory as soil moisture has slightly improved over the past week. Overall current expectations is that the dry line does end up developing a bit further west perhaps around the Highway 27 corridor, creating a slightly larger warm sector. && .SHORT TERM /THROUGH FRIDAY/... Issued at 248 PM MDT Wed Apr 24 2024 Tonight, the 850 mb LLJ will strengthen and shove more moisture into the CWA. At the surface, easterly winds will cause upslope flow, leading to stratus and patchy to locally dense fog. This fog may begin around 10Z and potentially last until 18Z. The stratus will linger around longer than the fog and potentially cap the severe environment tomorrow afternoon/evening. Also tonight, a shortwave looks to fire off a few showers and storms around 7Z. Small hail and some gusty winds are possible (5% chance), but confidence for severe weather is less than 2%. These showers and storms are expected to form near the eastern Colorado border and move east. The precipitation will exit the CWA in the late morning. If these showers and storms linger and are fairly strong, this precipitation could deplete the environment of ingredients for the later storms. After 18Z, southerly winds will pick up with gusts up to 35 kts in the southerly portions of the CWA. Depending on where the dryline sets up, locales to the west will be much more dry. RH values to the west of the dryline will drop into the lower teens. This will create critical fire weather conditions for locations south of I-70 and west of Highway 25. Most locations will only briefly see the critical conditions, but there is high (80%) confidence that Greeley county will see prolonged critical conditions. If the dryline stalls out farther to the east and north, surrounding counties will have a good shot at hitting Red Flag Warning criteria, hence why the Fire Weather Watch has been left in place. Blowing dust will also be possible (~20-50% chance) in locations along and south of Highway 36. Along the Kansas Colorado border will see the best conditions for blowing dust. Visibility reductions down to 2-3 miles are possible in plumes of blowing dust. Brown-out conditions cannot be ruled out. The dryline will be the trigger for the severe weather in the eventing. SPC has added an Enhanced risk to the southeastern CWA for Thursday afternoon-night. This is based on a hatched/significant hazard for 30% chance of hail and 10% chance of tornado. For this event, the environment will be highly primed for tornado and hail hazards, but there will likely (60%) be a hefty inversion that will work to cap the updraft potential. If the cap does break, isolated discrete to clusters of severe storms will form and all hazards will be possible, with a focus on tornadoes and hail. The entire Tri- State area will have potential to see severe weather, but chances increase farther to the southeast. Storms are expected to start firing around 18-21Z with the highlight of the severe storms being 21Z-06Z. The prime location for the severe storms will be in the southeastern CWA and the storms will move to the northeast. After 06Z, the severe weather threat will lower over the following 6 hours. During this time, we will begin to get the wrap-around precipitation from the northwest. These are expected to just be showers with a few weak thunderstorms embedded within. Less than 0.5 inches of QPF is expected with this system with most of that falling north of highway 36. As the low pressure system leaves the area on Friday, strong northwesterly winds are expected to follow. Gusts up to 40 kts are already expected due to the pressure rises. Temperatures overnight tonight and tomorrow night will cool to around 50. High temperatures tomorrow will be highly dependent on the dryline location and extent of the stratus. Under the stratus, highs will only reach the upper 60s to lower 70s. In the southwest, behind the dryline, low to mid 80s are forecast. Friday will be a bit more uniform with the northwestern CWA only warming into the mid 60s and the southern CWA reaching into the mid to upper 70s. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Issued at 254 PM MDT Wed Apr 24 2024 A low pressure system will lift to the northeast across north central Kansas and south central Nebraska Friday evening. Overnight, there will be a 20-50% chance of showers and a few thunderstorms across areas mainly along and east of Highway 26. Another low pressure system will lift to the northeast, out of the Four Corners region Saturday, bringing additional chances of precipitation to the area. Chances (40-80%) for showers and thunderstorms will increase west to east through the day as the system moves across the CWA. Saturday night into Sunday, shower and thunderstorm chances continue as wrap around moisture impacts the region. Winds are also expected to increase on the back of the system. Zonal flow sets up over the region on Monday and Tuesday. Expect a drying out period during this time and a warm up. Monday highs will be mainly in the low to mid-70s. Afternoon highs on Tuesday will be in the 70s and 80s. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 511 PM MDT Wed Apr 24 2024 Breezy conditions will continue into the evening hours. The main concern, especially for the first portion of this TAF period will be stratus and patchy fog as moisture advects into the area. Currently, thinking stratus will be the main aviation concern as fog may be patchy in coverage as wind may lead into the "dissolving" of fog so will utilize VCFG for this. IFR to LIFR appears to be likely at each terminal. Some nocturnal convection may impact KMCK tonight around 06Z so will use VCTS until confidence increases in terminal being affected. Thursday afternoon may see some storms, perhaps severe during the afternoon hours with all hazards on the table. Exact timing due to initation issues exists currently so remain aware for updates. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...Fire Weather Watch from Thursday afternoon through Thursday evening for KSZ013-027-028-042. Red Flag Warning from noon to 8 PM MDT Thursday for KSZ041. CO...Fire Weather Watch from Thursday afternoon through Thursday evening for COZ253-254. NE...None. && $$ UPDATE...Trigg SHORT TERM...CA LONG TERM...Wekesser AVIATION...Trigg
Area Forecast Discussion
National Weather Service Gray ME
1050 PM EDT Wed Apr 24 2024 .SYNOPSIS... Dry high pressure then moves into and across the region tonight through Saturday. A warming trend can be expected over the weekend with chance of showers Saturday night or Sunday. Warmer weather is then expected early next week for most areas except possibly the coastal plain. && .NEAR TERM /OVERNIGHT/... 1050 PM Update...Another round of very minor tweaks using latest 00Z hires guidance. At this time, the only clouds remaining over the area are a few stubborn patches of cumulus near the Whites, but these are fast eroding right on schedule. Did go a bit more deterministic and lowered sky coverage further to denote the strong clearing trend. Winds are just starting to become less gusty, and more of a steady breeze... with this trend continuing over the next few hours. 702 PM Update...Just a few minor tweaks to T/Td/sky trends overnight with latest hires guidance coming in. Overall very little change of consequence. At this time, the cold front is slipping offshore with gusty northwest winds 25-35 and a clearing trend. over the area. Previously... A cold front will pass through the area through the evening, kicking up some winds as well as dropping temperatures overnight. After midday clearing, scattered showers have again developed over the area. This is associated with lift from the passing cold front, and should taper into the early evening. Some light snow is also expected through early evening along the US/CAD border. Mixing taps into some low level winds through late evening, creating gusts up to 35 mph. Winds should lose gust factor around midnight, with breeze continuing. Temps fall due to this CAA, with widespread values around freezing or off into the 20s across the mountains. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... Wave that enhanced winds Wed evening will have moved out for Thursday, with just a few gusts early. As mixing kicks in amid a very dry airmass, will likely see RH values fall into the 20s and teens through the afternoon. Limited moisture through the column should prove for a nearly full sun day. Temperatures will be cooler however, and struggle to warm outside of direct sun insolation. HRRR is depicting a seabreeze beginning early afternoon, and this should bring a wind shift to coastal communities around 2pm along with a bit more humidity as temps fall off a couple degrees. && .LONG TERM /FRIDAY THROUGH TUESDAY/... We`ll start off the long term period 12z on Friday with a 1030+ millibar high pressure center overhead. A cool crisp morning will give way to a sunny afternoon but with below normal temperatures. Deep layer ridging builds Friday night allowing for the fair weather to continue. Radiational cooling is likely Friday night and therefore sided with MOS guidance for lows. Deep layer ridging slowly moves eastward on Saturday but still should provide for a fair weather day with temperatures returning to the 60s. A warm front approaches from the west Saturday night with the chance of showers late. However, the ridge aloft will hold firm so capped the PoPs some as it`s entirely possible that any period of showers Saturday night and Sunday could be brief. It still should remain cloudy Sunday with low level onshore flow in place, but larger scale subsidence should keep chances of rain low. The same general setup looks to be in the cards for Monday but there is more uncertainty in temperatures as onshore flow may penetrate deeper into Maine and portions of NH. The best chance of 70+ degree readings will be over southwestern NH while lower temperatures are expected as one moves eastward. There is also a chance that some showers will spill over the ridge axis. The best chance of measurable rainfall will come Tuesday and/or Wednesday as the ridge finally breaks down and allows a trough to approach from the west. Showers and perhaps a few thunderstorms will be possible then. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Short Term...VFR with gusty NW winds through mid evening. MVFR ceilings through late this afternoon for HIE. Some gusts may approach 30 kt accompanying showers. Some LLWS is possible as surface winds settle before winds aloft. Winds slowly slacken overnight. Lighter winds Thursday, with primarily SKC conditions. Can`t rule out some valley fog developing Thursday night. Long Term...VFR prevails Friday through Saturday with high pressure overhead. Scattered -SHRA arrives Saturday night through part of Sunday with possible lower ceilings although the any rainfall would likely be brief at one location. The same is expected for Monday although chances of rain will be lower. && .MARINE... Short Term...NW winds increase this evening as a cold front crosses the waters. Some gusts to 35 kt are possible, but bulk of these winds should be 30kt or less. These winds slacken below SCA criteria Thursday morning, with seas slowly lowered to 3 to 4 ft through the day. A seabreeze may form during the afternoon, turning winds onshore for the bays/harbors. Long Term...Winds and seas to remain below thresholds hazardous to small crafts as high pressure builds over the waters Fri-Mon. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 8 AM EDT Thursday for ANZ150-152- 154. Small Craft Advisory until 4 AM EDT Thursday for ANZ151-153. && $$ UPDATE...Casey NEAR/SHORT TERM...Cornwell LONG TERM...Ekster
Area Forecast Discussion
National Weather Service Reno NV
329 PM PDT Wed Apr 24 2024 .SYNOPSIS... Cooler weather along with periods of showers and thunderstorms will persist through early Saturday. Potential thunderstorm risks include gusty outflow winds, dangerous lightning, and localized heavy rain and/or small hail. Please be aware of rapidly changing conditions if recreating outdoors. Drier weather and a slow warming trend are expected to return on Sunday and persist into Tuesday. && .DISCUSSION... According to the latest RAP analysis, an upper air low is currently residing to the west of the southern CA and the northern Baja Peninsula causing a southerly to southwesterly flow over the CWA this afternoon. The latest radar imagery along with surface observations show some isolated to scattered showers and storms along and east of a line from Sonora Pass, CA to Lovelock, NV as well as in northern Washoe County that are moving generally north- northeast. Going through tonight, models depict the upper air low passing eastward through southern CA and south of the CWA until it reaches the southern tip of NV by tomorrow morning. At the surface, models show showers and thunderstorms continuing in eastern and southern portions of the region through the rest of the day and into the night with a frontal boundary moving through the area. The most impressive looking storms in NV currently look to be east of the REV CWA and in LKN`s CWA at this time which is where the highest 0-6km bulk shear of around 30 kts is present. Models are showing pockets of around 500 J/kg of SBCAPE later this afternoon and evening in Mono and Mineral Counties, so best chances for thunderstorms look to be in this portion of the region. Storms are not anticipated to be severe, but they may contain some brief downpours, small hail, and gusty winds. Portions of Mineral and Lyon counties may see up to almost an inch of QPF by tomorrow morning with these showers and storms with southern Mono County and eastern Churchill counties coming in with about 0.50 inches of QPF. Other counties that see precipitation such as Pershing and Washoe may see a few tenths of an inch at most. Will monitor conditions, but not anticipating any hydro issues with this rainfall. On Thursday, models show the CWA having a divergent flow aloft in the morning that becomes west-northwesterly by the evening hours as a Pacific Northwest upper air trough moves over to control the upper air flow in the northwestern CONUS. Forecast guidance then has the axis of the trough passing over the CWA on Friday morning allowing for the CWA to take a northwesterly flow by the afternoon and evening hour. By Friday night into Saturday morning, forecast models have the base of the trough digging down over AZ/southern CA causing a north-northwesterly upper air flow over the CWA being underneath the rear portion of the trough. At the surface, temperatures look to take a cooling trend on Thursday and Friday due to cloud cover inhibiting daytime heating. Guidance also is still showing a 50-90% chance for widespread showers beginning in the latter half of Thursday and going through Friday night with a 15-30% chance of thunderstorms and/or ice pellet showers. Portions of the Sierra above 6500-7000 feet may see some accumulating snow with the colder temperatures. The latest NBM probabilities of 4 inches or more have come down a bit as they are around 10%. What also came down a bit is Thursday`s daytime winds though they still look to be on the breezy side gusting up to around 35-40 mph in northwestern NV. The latest NBM probabilities of 45+ mph wind gusts look to be around 20-40% with higher elevations having the best potential. QPF values for late Thursday and going into Friday night are forecast to range from around a few hundredths to around 0.5 inches in eastern Pershing county. Severe weather is not anticipated on Thursday or Friday though we will monitor conditions in case this changes as small hail and gusty winds cannot be ruled out with storms particularly on Friday. By Saturday morning, precipitation chances look to begin to taper off within the region. Going through the rest of the weekend, ensemble guidance shows a weak ridge moving over the CWA by late Saturday and continue into Sunday. A generally zonal flow is then seen on Monday over the CWA with another trough starting to develop off the coast of southern BC during the evening hours. Models then start to differ in their upper air solutions going forward starting on Tuesday as the GFS has the trough moving southward and turning the CWA`s flow aloft to southwesterly by late afternoon and evening hours of Tuesday. The latest run of the ECMWF as an alternative solution delays this progression of the trough until Wednesday. Will have to wait for models to come into better agreement in future runs for this far out to have a better handle on the upper air pattern in the middle of the week. But at the surface, a warming trend looks to begin on Saturday and continue into next week at least through Tuesday and potentially Wednesday. Drier conditions are also expected going into the midweek after the Saturday morning`s precipitation chances depart the region. As for winds, some models show winds to potentially gust up to around 35-45 mph on next Wednesday along the CA/NV border with a relatively tight surface pressure gradient in the forecast. Will continue to monitor this going forward as more forecast details become clearer. -078 && .AVIATION... VFR conditions are expected through the remainder of the today and going into tomorrow for most of the REV TAF sites. Exceptions include KTRK which expects some fog to develop between 09-16Z which will cause IFR visibilities. Also: will be monitoring conditions at KMMH with showers and thunderstorms expected to continue within Douglas, Mineral, and Mono counties through most of today though not expecting precipitation seen at the site to lower visibilities at this time. More widespread showers will migrate into the Sierra and western Nevada by Thursday into the start of the weekend with a bigger trough. Ahead of the main trough, FL100 winds increase resulting in enhanced westerly surface winds (25-35 kts) on Thursday afternoon. -078 && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$
Area Forecast Discussion
National Weather Service San Diego CA
900 PM PDT Wed Apr 24 2024 .SYNOPSIS... A deep marine layer; gusty winds in the mountains and deserts; and cooler conditions will prevail through Friday. Patchy drizzle or light rain is expected each night and morning west of the mountains. Gusty southwest to west winds will peak each afternoon and evening in the mountains and deserts through Friday. Winds will weaken through the weekend. Drier and warmer with a shallower marine layer expected early next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .Evening Update... High clouds are streaming in over the high desert as low clouds fill in much of the coastal basin this evening. Latest HRRR model guidance indicates drizzle and light showers will develop mainly after midnight, lasting until the mid morning hours. Winds have been gusty this evening as the trough axis moves over Southern California. Peak wind gusts have been mainly near 30-40 MPH across mountains and deserts, with highest gusts near 60 MPH in the San Gorgonio Pass and near In-Ko-Pah in San Diego County. Graypril will continue for much of the day on Thursday for those west of the mountains, especially away from the coast per latest HREF model guidance. The deep marine layer will maintain itself into Friday, so the chance for drizzle and light showers will once again occur Thursday night into Friday morning. Winds will also continue to be gusty across the mountains into the deserts on Thursday and Friday as well. Friday will see the strongest winds with these areas seeing peak wind gusts 40-55 MPH. Not all is lost, as a brighter and warmer weekend is in store! .Previous Discussion (133 PM PDT Wednesday)... Low clouds are expected to fill in the coastal basin again tonight into Thursday morning. Deep marine layer moisture combined with lift from a low pressure system passing through Southern California and Northern Baja will generate areas of drizzle and light rain this evening and overnight. The greatest coverage is expected to be in the coast and valleys in San Diego County and along the coastal mountain slopes. Any accumulations for the coast and valleys will be light, with 0.10 inches or less expected. On the coastal mountain slopes, around 0.25 inch is expected. Marine layer low clouds may become patchier Thursday night into Friday morning, but areas of drizzle or light rain are still possible. Dry conditions expected for the weekend into early next week. Gusty southwest to west winds are expected in the mountains and deserts through Friday. Peak winds gusts will be 50 to 65 mph. Gusts could locally reach up to 75 mph through the San Gorgonio Pass. Winds will peak each afternoon and evening. Winds will gradually decrease in the the weekend, with weaker winds expected early next week. Cooler conditions expected for inland areas Thursday, with a few degrees of warming on Friday for the coast. High temperatures will be as much as 10 to 15 degrees below average on Thursday for the mountains and valleys. A warming trend is expected for Saturday through Monday with not much change on Tuesday. Weak high pressure aloft is expected to prevail but there are some model differences for early in the week which would impact the strength of the onshore flow and the depth of the marine layer. This uncertainty creates greater spread of the high temperature forecasts for locations in the coast and valleys. If the warming develops, high temperatures would be near average for most locations on Sunday with high temperatures on Monday and Tuesday 3 to 7 degrees above average. && .AVIATION... 250400Z...Coast/Valleys...Widespread BKN/OVC stratus will prevail through 18Z Thu with bases 2000-4000 ft MSL and tops to 6500 ft MSL and with higher terrain obscured. Local VIS 3-5 miles will occur below the clouds in -DZ/-SHRA, mainly 09Z-18Z Thu. SCT/BKN stratus will prevail with bases 2500-5000 ft MSL 18Z Thu-03Z Fri, with increasing stratus again after 03Z Fri. Mountains/Deserts...Areas of terrain obscurations will continue at times along the coastal mountain slopes through Thu evening with cloud tops to 7500 ft MSL and (09Z-18Z Thu) areas of -DZ/-SHRA. Areas of west winds with surface gusts 30-50 kt will occur from the mountain crests east through the mountain slopes and into the deserts through Thu evening. VIS will be unrestricted on the desert slopes/deserts. && .MARINE... No hazardous marine conditions are expected through Thursday night. Stronger winds and choppy seas arrive Friday morning and continue into Saturday morning, likely generating hazardous conditions, especially in the outer waters. There is a period Friday night (mainly mid-evening to a little after midnight) when there is around a 25 percent chance of gale force winds near San Clemente Basin Buoy. There is a gale watch in effect from 5 PM Friday through 3 AM Saturday for this possibility, though there is high confidence of winds reaching Small Craft Advisory strength. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory until 11 PM PDT Friday for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass Near Banning. PZ...Gale Watch from Friday afternoon through late Friday night for Waters from San Mateo Point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island. && $$ PUBLIC...APR AVIATION/MARINE...Maxwell