Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/31/20

National Weather Service Kansas City/Pleasant Hill MO
620 PM CDT Sun Aug 30 2020 .Discussion... Issued at 236 PM CDT SUN AUG 30 2020 Key message: Next chance of rain late tonight into Monday morning. Outside of a stray shower potentially developing over central Missouri this afternoon, the weather will remain quiet for the remainder of the afternoon and evening hours. The return of southeast winds has brought back dewpoints in the mid 60s to near 70, and this moisture plume is well-depicted by the low-level cumulus field over the southwest half of the CWA. Low-level stratus is expected to develop tonight, with lows only falling into the middle to upper 60s. Main focus late tonight into Monday morning remains the approaching cold front associated with the shortwave trough moving through the Dakotas. General consensus is for a cluster of showers and thunderstorms to develop overnight from western Iowa into northern Kansas. There is considerable uncertainty to the coverage of precipitation once the activity enters the forecast area. There has been a persistent theme for convection to trend towards the instability axis over eastern Kansas, keeping much of the thunderstorms west of the state line. While light precipitation amounts are anticipated over the area, the heaviest rainfall along with the potential for strong storms should reside to the west of the area. The cold front will enter the CWA and become stationary Monday afternoon as the upper wave quickly lifts into Canada. Another wave is then projected to slide into the Southern Plains Tue/Wed, and this will continue rain chances Tuesday. Rain chances have trended down for Wednesday, as the track of the next wave has evolved slightly further south, keeping most areas dry with the exception of EC KS into C MO. Surface high pressure builds back into the region, returning tranquil weather through much of the remainder of the week. && .Aviation...(For the 00Z TAFS through 00Z Monday Evening) Issued at 620 PM CDT SUN AUG 30 2020 VFR conds will prevail at the onset of the TAF pd however, models are suggesting IFR cigs will move into the TAF sites btn 07Z-09Z. A cold front is expected to move through the terminal btn 12Z-14Z bring the chance for thunderstorms. However, there is still some uncertainly as far as storm location as the HRRR wants to keep pcpn west of the TAF sites however, the NAM suggests storms will impact the TAF sites. Have opted to keep the -tsra in the TAF for this issuance and then make adjustment based on 00Z model guidance. With any storms expect MVFR cigs btn 1-2kft as well as vsbys reduced to 4SM-5SM. Storms are expected to mov S of the TAF sites by 18Z however some showers may remain in the area with cigs lifting back to VFR btn 3-4kft. Winds will be out of the SSE btn 5-10kts ahead of the front but will veer to the north behind the front and remain around 10kts. && .EAX WATCHES/WARNINGS/ADVISORIES... KS...NONE. MO...NONE. && $$ Discussion...Blair Aviation...73
National Weather Service Eureka CA
214 PM PDT Sun Aug 30 2020 .SYNOPSIS...Very warm, dry, and smoky conditions will continue across much of interior Northwest California through the upcoming week, though northerly winds will help bring clearer skies to most of Humboldt and Del Norte counties through tomorrow. Coastal clouds and fog will persist south of Cape Mendocino, while sunshine will prevail to the north of the Cape through Tuesday. && .DISCUSSION...An upper-level trough will continue to drop into the Northwestern U.S., while high pressure over the Northeast Pacific builds today. Interior Northwest California will be placed in dry north to northeast flow as a result. The thermal trough along the coast should continue to shift inland this afternoon, allowing for onshore flow along the coast this afternoon. Winds will be breezy along the Del Norte Coast, with some gusts exceeding 30 mph. Interior highs this afternoon will greatly depend on the coverage of smoke. In areas of moderate to dense smoke, highs will struggle to really get quite warm, but where skies are clear, highs will climb into the 90s. Sunny, albeit a bit hazy, skies will prevail along the coast north of Cape Mendocino through this evening, with some patches of stratus developing overnight. Cloud cover along the Mendocino Coast will linger throughout the day today, but some clearing will still be possible. North to northeast winds will pick up starting this evening over interior Del Norte and northeast Humboldt counties. A Red Flag Warning is in place for these gusty winds and low humidities. In addition, some locally gusty winds will be possible overnight along the higher elevations of eastern Lake County. For additional information, please see the Fire Weather Discussion. Monday`s weather will be similar to that of today. Sunny skies with some haze will continue along the Redwood Coast, with the Mendocino Coast continuing to observe some stratus. Another round of breezy winds along the Del Norte Coast will be possible Monday afternoon. Smoke from the ongoing active wildfires will likely prevail across portions Lake, Trinity, and Mendocino counties. Interior temperatures will be a few degrees warmer as high pressure builds in aloft, but again this will be highly dependent on the coverage of smoke. High pressure will continue to move in aloft, with the thermal trough expected to shift offshore on Tuesday. As a result, offshore flow will commence. Afternoon highs on Tuesday along the Redwood Coast will likely climb into the 70s as a result, with lingering stratus likely keeping the Mendocino Coast cooler. Smoke may drift back to the west and into Humboldt and Del Norte counties overnight on Monday and into Tuesday given the offshore flow. Guidance indicates a southerly surge of stratus will be possible on Tuesday and the current thinking is that stratus will round Cape Mendocino sometime on Tuesday afternoon. This will need to be monitored because if it`s earlier, Tuesday`s forecasted afternoon highs along the Redwood Coast may be too warm. At this time, the latter part of next week looks to be quite cloudy for coastal Northwest California with coastal areas expected to be socked in by stratus. High temperatures for the latter part of the work week across the interior will again be dependent on smoke coverage, but afternoon highs are expected to be in upper 90s, topping out around 100 in some of the warmer, smoke free areas. && .AVIATION...Haze lingers over much of northwestern CA today, with impacted visibilities in Mendocino and Lake counties from smoke. Similar to the last few days, HRRR smoke guidance is suggesting visibilities in these areas will improve late this afternoon as onshores push the smoke off toward the east, with vfr conditions expected once again overnight tonight. Farther north in Del Norte and Humboldt counties, gusty northerlies continue this afternoon, whipping up haze from sea spray. These are expected to weaken and shift NNE tonight along the north coast, with a stronger offshore component aloft supporting LLWS overnight. && .MARINE...ASCAT satellite wind data from a pass late this morning shows gale force winds across the northern outer waters and the northwestern corner of the southern outers, and most of the recent high resolution model guidance (NAMNEST, ARW, NMMB, HRRR, etc.) continues to depict sustained wind speeds of 30 to 40 kts with gusts nearing 50 kts continuing tonight and persisting through early Monday morning before subtly weakening. Wind speeds are then expected to receive a last pulse of strength tomorrow afternoon before significantly weakening overnight Monday night. These winds will generate seas of 14 to 18 ft across the outer waters, largest during this afternoon. GALE FORCE winds will likely reach close to the headlands of Point St George and Cape Mendocino as well, but otherwise model guidance indicates a sharp wind gradient toward the coast with significantly weaker winds nearshore, with HIRES guidance indicating possible overnight southerly wind reversals along the coast in Mendocino county. Steep northerly seas continue to propagate into all zones today, and hazard products remain unchanged with the afternoon forecast package. Conditions look to significantly improve heading into next week as the high currently building over the NEPAC slips overhead and the pressure gradient relaxes, possibly bringing a period of widespread light-and-variable-mixed-with-rounds-of-southerly winds around mid- week. && .FIRE WEATHER...A Red Flag Warning is in effect for Fire Weather Zones 203 and 204 through Monday morning. Exposed upper slopes and ridges above 1,500 feet will have poor RH recoveries tonight following humidity dropping into the teens this afternoon, with northeast winds becoming gusty at times and lingering into Monday. A shot of northerly winds will come down the northern Sacramento Valley tonight, and enhance dry northeast winds across the ridges of eastern Lake County tonight into Monday morning as well. Will headline Zone 264 for that reason, but the winds look like the will be rather localized and not enough to justify a Red Flag Warning. Still, this will be a big concern for the August Complex and LNU Complex fires. Easterly flow will pick up again across our interior ridges Monday night as well, but will tend to be lighter for most locations. Beyond that, the forecast continues to look locally hot and dry through next weekend, but at least there does not appear to be any additional strong winds or thunderstorm events on the horizon. && .EKA WATCHES/WARNINGS/ADVISORIES... CA...Red Flag Warning until 11 AM PDT Monday for CAZ203-204. NORTHWEST CALIFORNIA COASTAL WATERS...Hazardous Seas Warning until 3 AM PDT Monday for PZZ450. Gale Warning until 3 AM PDT Tuesday for PZZ470. Small Craft Advisory until 10 AM PDT Monday for PZZ455. Hazardous Seas Warning until 10 PM PDT Monday for PZZ475. && $$ Visit us at Follow us on Facebook and Twitter at: For forecast zone information see the forecast zone map online:
Area Forecast Discussion
National Weather Service Grand Forks ND
944 PM CDT Sun Aug 30 2020 .UPDATE... Issued at 944 PM CDT Sun Aug 30 2020 Latest SPC meso page has even MU CAPE pretty much gone over our area, with most of the precip becoming more stratiform with a few embedded thunderstorms. As expected, severe threat ended with the sun going down so cancelled the watch early. Made a few adjustments to POPs to better match current radar trends, and lowered coverage of thunder a bit. Precip should clear out from west to east as the front pushes through later tonight. UPDATE Issued at 633 PM CDT Sun Aug 30 2020 Satellite loop shows quite a bit of explosive thunderstorm growth just to our south over SD, while most of the convection over ND has been less impressive. There is some instability in the far southern counties for the next few hours, and some of the line developing over SD could make it into that area. Otherwise the window for severe development seems to be closing. There has been a decent amount of rain with even the non-severe cells, along with some training along the cold front. Don`t think there will be widespread heavy rain but should be enough to get up to the QPF values we were expecting. && .SHORT TERM...(This evening through Monday night) Issued at 243 PM CDT Sun Aug 30 2020 Several items in the immediate short term have the biggest impact for this portion of the forecast. The first is any strong to severe thunderstorms in the late afternoon into early evening, and the second is actual rainfall amounts. Starting with the strong to severe storm potential, there looks to be a fairly short window for any. Agree with prior shift, that the threat should end by around 7 pm or so. The wind shift line is along a Cavalier to just west of Jamestown ND line. Temperatures have risen into the upper 70s ahead of this boundary, with dew points in the lower 60s. Surface based CAPE values are around 1500 J/kg, with ML values a tad lower. 700mb temperatures have been warm across this area, but more so down into South Dakota. As mentioned before, the best 0-6km shear values lag well behind the surface boundary. Precipitable water values have increased to around 1.3 to 1.4 inches, which was progged yesterday. The HRRR continues to show activity increasing along this boundary in the 4 to 5 pm time frame. However, based on how fast the surface front is moving, this activity looks to be post-frontal. So will be watching to see if anything can grow in the next 1-2 hours. As far as rainfall amounts, the system moving through today into tonight is disjointed. Generally, that means that it is not coming through as one continuous area of precipitation. There is the high based/low qpf activity that is moving into areas east of the Red River Valley now, then there is a break behind it (of 1-2 hours). Then more activity should get going in the late afternoon/early evening. This should be the steadier rain, and it should favor the southern half of the FA more than areas north of highway 200. Amounts are going to depend on whether strong storms can form in the southeast FA or not. The activity should shift east of the FA by Monday morning, with Monday afternoon looking breezy to windy again. These winds should die down Monday evening, with clearing skies. Therefore Monday night should be fairly cool. .LONG TERM...(Tuesday through Sunday) Issued at 243 PM CDT Sun Aug 30 2020 Early in the period, zonal flow aloft will keep precipitation and impactful weather to a minimum. Models are beginning to get a better handle on the trough Wednesday Night into Thursday Morning, although some surface features still are unclear. Positioning of the surface low appears like it will stay in Manitoba, but monitoring over the next few days will be necessary for precipitation impacts. At this time, precipitation impacts are expected to be primarily in the far northern parts of the CWA. The primary impact from this wave will be a cold front that will provide for more fall-like temperatures midweek. As high pressure settles in over the area and the surface low amplifies to our east, expect wind speeds to increase on Thursday. Forecast soundings indicate a dry and deep mixed layer, providing the chance for some stronger gusty winds on Thursday. High pressure and ridging behind the front will also bring dry conditions and warming through the end of the period. Sunday, there appears to be a chance for another wave that may provide another cold frontal response at the surface. Details at this time are limited, especially regarding precipitation and surface features, but it appears another temperature drop off is possible. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 633 PM CDT Sun Aug 30 2020 Thunderstorms along and ahead of a cold front extending from just east of KGFK into southeastern ND, so all but KDVL will see some convection through the next few hours. Some rain has been heavy enough to lower visibility into the 3-5SM range, but will be fairly short lived. Mostly showers behind the front, with a bit of MVFR ceilings along with it. The front will move from west to east this evening and overnight, with precip and winds shifting to the northwest. The precip will taper off and MVFR ceilings will lift just a few hours after the front passes, leaving VFR conditions. Winds will pick up from the west with some gusts over 20 kts later in the period. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...JR SHORT TERM...Godon LONG TERM...Perroux AVIATION...JR
National Weather Service Sioux Falls SD
631 PM CDT Sun Aug 30 2020 .SHORT TERM...(This Evening through Monday) Issued at 247 PM CDT Sun Aug 30 2020 Main focus is on tonight`s severe weather risk. Most CAMs and recent HRRR runs support clustered multicell and supercell (some strong to severe) storms developing in central SD early this evening. This occurs just ahead of the approaching cold front moving into central and eastern SD early this evening. An elevated mixed layer evident on water vapor imagery across central and eastern SD has prompted development of very steep mid and low level lapse rates, MLCAPE of 2500-3500 J/kg, and DCAPE of 1000-1600 J/kg over central SD. Surface observations show low level moisture pooling ahead of the front with dew points in the mid 60s and temperatures in the 80s, combined with mainly southeast surface winds. Nice low level curvature is evident on model hodographs near KHON, aided by low level jet influence. These combined ingredients favor a threat for large hail exceeding golf ball size, damaging wind gusts of up to 70 mph, and a tornado or two being possible with the strongest storms tonight. Model soundings and cumulus field development suggest storm initiation as the cap breaks somewhere in the 4-7 pm window roughly along axis from Aberdeen to Chamberlain. 0-6km bulk shear of 30-40 kts should allow for organized storms to persist, with modest mid level winds prompting a tendency for storms to cluster together. Most model guidance supports the main severe weather threat remaining north of I-90 through around 10 pm tonight and storms mostly being east of I-29 by midnight. Isolated showers and storms are still possible along and south of I-90, but are favored to have lesser coverage. Along with and behind the front, expect winds to turn northerly and become gusty. Additional showers and isolated storms are possible behind the front as well, although severe weather threat is negated with this activity. Did keep rain chances in overnight for much of the region for this potential. Much drier and cooler air moves in immediately behind the front as an upper longwave trough digs into the region. Expect lows to fall into the 50s tonight, coolest in central SD further west where skies begin to clear and the driest air moves in soonest. Dry surface high pressure moves in for Monday, bringing cooler high temperatures in the 70s to near 80 degrees and light and variable winds. .LONG TERM...(Monday Night through Sunday) Issued at 247 PM CDT Sun Aug 30 2020 Unfortunately little to no relief is ahead for those wanting rain in the upcoming work week. For Monday night through early Wednesday, several rain-making disturbances are poised to track south of the immediate region. With an upper trough axis in the vicinity and drier northwest flow aloft, drier weather with near seasonal temperatures prevails during this period. On Wednesday, a disturbance to our north should bring a period of warm air advection and warmer weather again with highs approaching 90 degrees. While this disturbance looks to bring a front through the region by Thursday, Gulf moisture is mostly blocked by a system to the south yielding mainly dry weather. The bigger impact mid week, other than a period of hotter summery weather, looks to be periods of breezy winds from a tighter surface pressure gradient. Late week, there is little change to the weather pattern with drier weather and generally seasonal temperatures persisting, but there is some low confidence chance of more widespread rain with a late weekend system. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 631 PM CDT Sun Aug 30 2020 Scattered thunderstorms will move east across the forecast area through the first 1/2 of this TAF period. Have attempted to pinpoint some favored time frames for impacts of convective activity at TAF locations, though timing comes with increased uncertainty as we approach the I-29 corridor late evening into the overnight hours. Cold front and associated upper wave triggering the storms will be followed by gusty north-northwest winds for several hours during the pre-dawn to mid-morning hours, with gusts occasionally topping 25kt. Winds gradually subside through the remainder of the day. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...BP LONG TERM...BP AVIATION...JH
Area Forecast Discussion
National Weather Service North Platte NE
931 PM CDT Sun Aug 30 2020 .UPDATE... Issued at 931 PM CDT Sun Aug 30 2020 Updated to remove severe thunderstorm watch 476 from portions of north central Nebraska. Kept remaining counties in the watch until 05Z. Latest mesoscale model indicate elevated thunderstorm developing near and southeast of Callaway through Ewing between 10 and 11 pm CDT. Any storms which redevelop could become strong to severe and contain hail and strong wind gusts. && .SHORT TERM...(This evening through Monday night) Issued at 159 PM CDT Sun Aug 30 2020 A potent area of upper level low pressure is located across northern Alberta this afternoon with a shortwave trough extending southward from this feature into the northern High Plains. A cold front will continue to surge southeast across northwest Nebraska...reaching to near Bassett to Broken Bow by early this evening. Decent low-level moisture advection continues ahead of the front with dew points rising through the mid 60s. A plume of steep mid-level lapse rates (greater than 8C/km) have spread across the area, and with good surface heating, SFC based CAPE values have reached near 3000 J/KG ahead of the frontal boundary. HRRR and other hi-res short term models develop a couple of discrete storms late this afternoon near the cold front. Shear would support supercells and the potential for large hail given the very steep mid-level lapse rates. Further more elevated development is expected early this evening near the H85 front that will extend from Holt county southwest to Custer county. NAM has some impressive mid-level CAPE along this boundary and these storms too could produce large hail. The cold front then accelerates southeast through the entire area by midnight. Significant pressure rises and H85 winds increase to around 40-50 kt behind the front. SFC wind gusts of 25-35 kt likely from late evening though about 4am CDT and have increased gusts some overnight. Surface high pressure quickly builds into western and north central Nebraska Monday. Expect a very pleasant day with low dew points and highs int the 70s. North winds will quickly diminish Monday with return southeast low-level flow developing by afternoon across western Nebraska as the surface high moves east. Monday night, a shortwave will drop quickly from western Montana into the Great Basin. Favorable jet dynamics will overspread the area to the east of this feature. Large scale lift and increasing mid- level moisture should lead to scattered showers. Some thunder is possible across far southwest Nebraska where some elevated CAPE will be present. Overall best chances for precipitation tomorrow night will be across southwest Nebraska. Overall, amounts look to be on the light side. .LONG TERM...(Tuesday through Sunday) Issued at 159 PM CDT Sun Aug 30 2020 Upper level ridging moves east from the eastern Pacific and will be centered across the Great Basin by Friday. Dry conditions are expected across our region all week as there is very little moisture within the northwest flow aloft on the eastern periphery of the upper high. Temperatures will warm from the upper 70s to lower 80s Tuesday to the upper 80s to lower 90s Wednesday. This warm day will be just ahead of a cold front that will sweep southeast in the wake of a shortwave moving across southern Canada. Cooler Thursday behind the front. Then it warms again Friday and Saturday ahead of a deep trough that will develop from western Canada toward the Great Lakes the second half of Labor Day weekend. Expect a strong cold front to cross the area sometime during this period. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 648 PM CDT Sun Aug 30 2020 A strong cold front will continue to move southeast through western Nebraska this evening. Northerly winds will gust up to 30KT at times this evening, gradually diminishing overnight. A line of thunderstorms will also move southeast along the front for areas east of ANW to TIF. Other showers and thunderstorms to develop behind the surface front and may affect KVTN after 04Z. Light winds and mainly sunny skies Monday at the KLBF and KVTN terminals. && .FIRE WEATHER... Issued at 159 PM CDT Sun Aug 30 2020 Fire weather concerns remain elevated through early Sunday evening as humidity values drop into the teens across the eastern Panhandle and portions of southwest Nebraska. 20z observations across the Panhandle indicate many locations already seeing < 20% humidity with little improvement expected as daytime mixing continues for the next few hours. Surface front moving into far northwest Nebraska will dive south through the late afternoon and evening, with wind gusts behind the boundary expected to climb to 30 to 35 mph out of the north. This abrupt wind shift combined with the antecedent low humidity and breezy conditions warrant continuation of the Red Flag Warnings in place. Pressure rises of AOA 6 hPa/hour will facilitate elevated winds overnight but as surface high pressure moves in Monday, winds will begin to diminish by sunrise. Areas along a Halsey to Imperial line will struggle to see humidity climb above 70% overnight with some locations remaining closer to 60%. Temperatures will fall into the 40s and 50s tonight with highs only reaching the 70s tomorrow but given the dry air moving in, humidity values will once again fall into the 20s for most if not all locations. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Roberg SHORT TERM...Taylor LONG TERM...Taylor AVIATION...Roberg FIRE WEATHER...Jurgensen
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
1043 PM CDT Sun Aug 30 2020 .UPDATE... Issued at 1042 PM CDT Sun Aug 30 2020 Showers have moved out of the area late this evening, though there will continue to be a slight chance of showers over southeast Missouri through tonight. There will be the potential for some fog, possibly dense over southeast Missouri late tonight into early Monday. Have upped PoPs over parts of central and southeast Missouri during the late morning hours into afternoon as recent runs of the HRRR is showing convection moving through these areas. Going lows still look good and made little changes to the rest of the forecast. Britt && .SHORT TERM... (Through Late Monday Night) Issued at 231 PM CDT Sun Aug 30 2020 Impacts will likely be limited through the short term period with showers dotting the map over portions of southeast Missouri into southern Illinois. Regional satellite shows the thickest cloud cover running along the stalled frontal boundary to the south. This is co-located with a weak shortwave that will be exiting east through southern Illinois. The best potential for rain will likely be through southern Missouri and southern Illinois with passage of the shortwave. Thereafter, precipitation is limited to just a few lingering showers overnight. Ample low level moisture and light winds could result in patchy fog again tonight with much of it across the Ozarks, valleys, riverbeds. Surface high pressure funnels dry easterly flow in at the surface from early Monday morning through the afternoon. A cold front begins to drift into northeast Missouri by late afternoon. Held onto only slight chances during peak diurnal heating. The boundary begins to slow with little convergence and limited moisture with easterly flow ahead of the front. Continued to keep things mainly dry through Monday evening. Attention then turns to the west as an upper level shortwave approaches late Monday night. Guidance is hinting at convective development centered around a surface low, which runs along the cold front over eastern Kansas. CAMs favor southeast movement with the complex, which may keep most of the precipitation consolidated around the surface low. Areas further east may be limited to scattered showers and a couple of thunderstorms after midnight and into early Tuesday. Maples .LONG TERM... (Tuesday through Next Sunday) Issued at 231 PM CDT Sun Aug 30 2020 Potential impacts through the long term period will result from shower and thunderstorm potential Tuesday through Thursday. A cold front is expected to bring another bout of cooler and dryer air Friday into next weekend. A stalled boundary basically washed out south of the area Tuesday morning with zonal flow aloft over the Upper Mississippi Valley. Another cold front will extend from the Great Lakes into the central plains, while a pronounced upper level trough will be digging southeast through the Rockies. Through the course of the week, the front to the northwest just makes it into the area, before its southward progress stalls. The first good potential for rainfall arrives Tuesday morning as an upper level shortwave passes over the region. Deterministic guidance brings our attention to eastern Kansas with what looks to be a convective complex. Trends have continued to develop this late Monday night tracking it into southwest Missouri Tuesday morning. Heavier precipitation stays over southwest Missouri with the eastern periphery of the rain reaching near central Missouri. This gives rise some uncertainty in the overall spread in precipitation further east near the Mississippi River into Illinois. I`m leaning more in favor of scattered showers and a few thunderstorms, as the earlier convection spread clouds across the area and limits instability. Beyond Tuesday, confidence decreases in time with regard to precipitation potential and temperatures. The frontal boundary stall through southern sections of the CWA with several fragments of weaker vorticity pushing along the front. Diurnal instability will likely be much better south of the CWA, where thunderstorm potential will be greater. Further north, it`s likely isolated to scattered showers will be favored with the limited instability. Ensemble spread do a good service in showing the uncertainty as member continue to diverge in time. Mean temperatures still look to cool, however, with highs most likely ranging from the mid-70s to the mid-80s throughout the period. The main upper wave that lags well to the west finally approaches by Thursday afternoon. Latest trends have pushes this a bit further south, suggesting that rain potential is trending down with the southward lean of the frontal boundary and better lift centered around the Missouri/Arkansas border. Surface high pressure then builds in behind the front with better certainty in drier and cooler weather heading into next weekend. Maples && .AVIATION... (For the 00z TAFs through 00z Monday Evening) Issued at 607 PM CDT Sun Aug 30 2020 Dry and VFR conditions are expected through 06Z. Then low clouds with low MVFR ceilings are expected to move into the terminals late tonight. There is some possibility for ceilings below 1000FT AGL between 10-13Z. There will also be the potential for fog with MVFR/possible IFR visibilities at KSUS and KCPS between 07-13Z. Then ceilings will improve to VFR by late morning with mainly dry and VFR conditions expected after 18Z. Winds will remain light through the period. SPECIFICS FOR KSTL: Dry and VFR conditions are expected through late tonight before low clouds with low MVFR ceilings move into the terminal from the south. These ceilings will improve to VFR by late morning with mainly dry and VFR conditions expected the rest of the period. Winds will remain light through the period. Britt && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
...Updated for 00Z Aviation Forecast Discussion...

.DISCUSSION... Issued at 240 PM CDT Sun Aug 30 2020 .Summary: A few strong to severe storms remain possible in northeast NE this evening. Cooler on Monday and Tuesday with some chance for precipitation in the south. Dry conditions from mid week into next weekend with near to slightly above-normal temperatures. .Tonight: Early afternoon mesoanalysis revealed a surface low over central SD with an associated pre-frontal trough/quasi-dryline extending south through north-central NE into northwest KS. Meanwhile, a cold front was advancing southeast through the western Dakotas. Plan-view WSR-88D VWP data indicate the presence of a 30 kt low- level jet ahead of the pre-frontal trough, which is aiding in the poleward flux of higher theta-e air in a narrow axis through central NE into south-central SD. Continued daytime heating coupled with boundary-layer dewpoints in the lower to mid 60s will yield an axis of moderate to strong instability and a weakening cap by mid to late afternoon ahead of the surface trough. By late afternoon, the cold front is expected to overtake the pre-frontal trough, supporting storm initiation over north- central NE. The last several HRRR runs depict a discrete storm mode, and given the juxtaposition of moderate to strong instability with sufficient vertical shear, supercell structures are likely. The primary question is whether any of the storms will eventually move into our area this evening. Current indications are that our far northwest counties could be affected with the primary hazard being hail up to the size of ping-pong or golf-ball size. The cold front will continue through the area overnight with a chance of thunderstorms along it. The redevelopment of showers and perhaps a few thunderstorms will be possible within the post- frontal environment over northeast NE late tonight as that area is glanced by height falls/forcing for ascent attendant to a vigorous shortwave trough moving through the northern Plains. .Monday and Tuesday: A few showers could linger into mid morning on Monday over portions of far southeast NE and southwest IA with dry conditions expected thereafter. Low-level cold advection should decrease by about midday with afternoon highs in the mid to upper 70s. On Monday night into Tuesday morning, the glancing influence of a subtle perturbation passing to our south will support a chance of showers and storms across our southern counties. Clouds should begin to decrease on Tuesday afternoon with highs in the mid to upper 70s. .Wednesday and Thursday: On Wednesday night into Thursday, another vigorous polar-branch disturbance is forecast to translate from the northern Plains into the Great Lakes. An associated cold front will concurrently advance from the northern Plains through the mid MO Valley late Wednesday night and Thursday morning. No precipitation is currently expected with the frontal passage. Southwesterly low- level flow ahead of the front will advect a warmer air mass into the region on Wednesday with highs in the mid to upper 80s. High temperatures on Thursday will fall back into the 70s to lower 80s. .Friday and Saturday: Midlevel heights are forecast to rise over the central Plains in association with the eastward expansion of an upper high centered over the Great Basin. As such, it appears that temperatures could warm well into 80s by next weekend with negligible precipitation chances. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 600 PM CDT Sun Aug 30 2020 Winds will shift from south to northwest and become gusty tonight as a cold front pushes through the area. TSRA could affect KOFK this evening with MVFR conditions or possibly lower. TSRA chances are lower at KOMA and KLNK, but could at least be some spotty SHRA along and behind the front with areas of MVFR conditions. Winds will remain gusty at least into Monday morning from the north, then slowly decrease with VFR conditions. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Mead AVIATION...Miller
National Weather Service Raleigh NC
1020 PM EDT Sun Aug 30 2020 .SYNOPSIS... A series of upper level disturbances moving through the region will interact with very moist air and a pair of nearly stationary fronts extending across the Carolinas Monday through Tuesday night. && .NEAR TERM /TONIGHT THROUGH MONDAY NIGHT/... As of 1020 PM Sunday... Update: No significant updates overnight. Increased QPF slightly Monday afternoon. 00Z surface analysis shows the stationary frontal zone extending from an area of low pressure off the Grand Strand (see NHC Tropical Weather Outlook) west across SC and GA, with weak high pressure over the Mid-Atlantic state south through NC. To the west a notable shortwave in water vapor was approaching western TN, with areas of convection downstream toward the TN Valley. The RAP suggests a possible MCV embedded within the convection that will drift ENE across NW NC and SW VA late tonight, coincident with the return of higher low-level theta e and weak destablization across western NC. The low level flow response is relatively weak, on the order of 20kt at 925mb with the core of the LLJ passing to the north across SW VA, but as showers lock in a more stable airmass over the NW Piedmont and Blue Ridge, convection may increasingly show signs of some rotation. If an isolated storm or two can get going late tonight, parameters could be just enough to have some rotation by sunrise, though confidence is low. A greater threat may develop Monday afternoon with the passing primary shortwave, albeit also low amplitude and to our NW. Hires guidance indicates 1-1.5" of QPF in the Triad area Monday afternoon and evening, and WPC has extended the Slight Risk of excessive rainfall into that area. While it has been a few days since any notable rainfall, most area streams continue to run near or slightly above normal, so quick stream responses may aid in isolated flash flooding potential. -bls Previous discussion: Remnant MCVs from the ongoing mesoscale convective systems currently moving into the Lower MS and TN Valley will eject NEWD across the southern and central Appalachians overnight and then into the mid-Atlantic on Monday. At the surface, a complex pattern will likely evolve over the region over the next 12 to 18 hours, featuring a pair of quasi-stationary fronts across the SE US. The first surface boundary is the cold front the pushed south through central NC earlier this morning. Models indicate that this front will remain nearly stationary, extending through the Savanna River Valley to a developing offshore surface low, potential future tropical depression off the SE US coast. The second boundary of interest, which has yet to develop, will be a wedge/CAD front that should begin to take shape over the Carolina and Virginia Piedmont during the day on Monday. In response to the upper disturbances moving through the region, strong low-level warm moist air advection atop the pair of frontal zones will fuel widespread convection initially across the western Piedmont during the early Monday hours, with the convective rain chances spreading east throughout the afternoon and evening. Maximized across the NC Piedmont sections, within the zone of strongest H8 WAA, a corridor of moderate instability and 25-35 kts of deep-layer shear should be sufficient for a wind damage threat during the mid to late afternoon. Additionally, locally enhanced helicity/shear and low LCL heights INVOF the wedge front boundary draped across the NC Piedmont could support a conditional, low-end threat of an isolated tornado as well. Nocturnal stabilization and convective overturning/ should lead to a decrease in convective intensity and coverage during the evening and overnight hours. Given the anomalously high PWATS of 2 2.25"(1 to 2 S.D. above normal) and with the wedge boundary in place, widespread rainfall amounts of a half to one inch can be expected along and west of the Triangle, with some isolated higher amounts of 1.5 to 2.0" possible in the stronger convective cells training over the Piedmont counties. Localized flooding, especially in urban/poor drainage areas, will be possible across the western Piedmont. East of the Triangle, rainfall amounts will decrease considerably, with as little as a tenth across the far eastern coastal plain counties. Temperatures: Lows tonight are expected to be in the mid 60s NE to upper 60s to lower 70s everywhere else. Highs Monday will feature a classic CAD gradient over the western Piedmont. Highs ranging from upper mid/upper 70s NW Piedmont to mid to upper 80s across central and eastern NC. Lows Monday night in the lower 70s. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... As of 405 PM Sunday... The shortwave trough will move east of NC on Tuesday, resulting in less shower and storm coverage compared to Monday. However, a frontal boundary will continue to linger near or over the area. In addition, an area of low pressure is likely to develop into a tropical depression by Tuesday or Wednesday as it moves northeast parallel to and then away from the Southeast US coastline. While no direct impacts from the system are expected in central NC, the easterly flow around the deepening surface low will result in decent instability and plenty of moisture across the area, especially in the Coastal Plain where PW values should be over 2 inches. Thus have high chance POPs in the east for Tuesday afternoon and evening, with low chance elsewhere. With weak flow aloft, the severe storm threat appears minimal at this time. The easterly flow will also result in one last day of near-to-below-normal temperatures, with forecast highs in the lower-80s north to upper-80s south. However, temperatures at any one location will depend on the exact placement of the frontal boundary, which is still uncertain at this time, as the GFS keeps the front much farther south (and thus has cooler temperatures) compared to the ECMWF. Lows Tuesday night will be in the lower-to-mid 70s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 405 PM Sunday... The frontal boundary should lift well north of the area on Wednesday, with an upper ridge building over the Southeast US and a lee surface trough over central NC. This will result in a return to a more typical summertime diurnal convection pattern, with shower and storm chances (about 30-40%) in the afternoon and early evening, diminishing quickly after dark. Temperatures will also be on the increase, with highs in the upper-80s the mid 60s NE to upper 60s to lower 70s everywhere else. Highs Monday will feature a classic CAD gradient over the western Piedmont. Highs ranging from upper mid/upper 70s NW Piedmont to mid to upper 80s across central and eastern NC. Lows Monday night in the lower 70s. to lower-90s on Wednesday, increasing further to lower-to-mid 90s on Thursday and Friday. With dew points in the mid-to-upper 70s, heat indices of 100- 105 are possible everywhere outside of the far northern and western Piedmont on these days, especially by Thursday and Friday. Lows will remain in the lower-to-mid 70s. A cold front looks to move through our area late Friday or early Saturday before possibly stalling near our SE zones. This will result in a lingering chance of showers and storms on both Saturday and Sunday, highest in southeastern zones. With Canadian high pressure building into the northern US, a taste of autumn with lower dew points (mid-to-upper 60s) and below-normal temperatures (upper- 70s to lower-80s) is possible by next weekend, especially in the northern Piedmont. However, this will depend on how far south the front is able to get, which is uncertain this far out. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... As of 745 PM Sunday... VFR through 06Z. Increasing moisture and lift across western NC will lead to IFR and perhaps LIFR ceilings at GSO/INT by 09Z, as well as scattered showers and isolated storms by 12z, as a frontal zone across SC lifts north into the NC Piedmont. Additional showers and storms may redevelop after 18Z and maintain the threat of adverse aviation conditions through the TAF the mid 60s NE to upper 60s to lower 70s everywhere else. Highs Monday will feature a classic CAD gradient over the western Piedmont. Highs ranging from upper mid/upper 70s NW Piedmont to mid to upper 80s across central and eastern NC. Lows Monday night in the lower 70s.period, with models suggesting that ENE winds will persist through the at GSO/INT and ceilings may remain at MVFR or lower. The pattern also favor LLWS potential by 09-12Z, but low-level winds may be quite strong enough to meet criteria. To the east toward RDU/FAY, ceilings may briefly become IFR by 12Z but should then scatter to VFR, with isolated showers and storms during the afternoon. VFR is more likely to continue at RWI, with less chance of showers and storms in the afternoon. Outlook: Very moist air in place will support widespread sub-VFR flight restrictions in stratus Monday night/Tuesday morning. Scattered to numerous showers and storms are expected Tuesday, followed by mainly diurnal rain chances Wednesday through Thursday. A cold front moving into the area from the NW will bring widespread rain chances to the area on Friday. Additionally, the risk for sub- VFR restrictions in fog/stratus will be possible each morning. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...CBL/bls SHORT TERM...Danco LONG TERM...Danco AVIATION...BLS/CBL
Area Forecast Discussion
National Weather Service Reno NV
130 PM PDT Sun Aug 30 2020 .SYNOPSIS... A dry cold front will bring temperatures to near normal the next few days along with breezy north winds. Winds then turn easterly late Monday into Tuesday, helping to finally ease smoke impacts across the region for a couple days. An unusually warm air mass takes hold the end of the week and through the weekend with temperatures likely to near record highs. Overall, the forecast remains dry, but there are low end chances for isolated thunderstorms over the High Sierra next weekend. && .DISCUSSION... A few "cooler" days in store with breezy north winds tonight into Monday turning easterly by Tuesday. Heat returns the middle and especially end of the week with upper 90s to even around 100 possible for lower valleys. Smoke to continue with some improvement likely Monday into Tuesday. * SMOKE: The latest high resolution smoke model (HRRRx) would indicate some improvement today for most areas as mixing improves. Unfortunately for those locations immediately downwind of ongoing fires such as Quincy, Portola, Susanville, parts of the Sierra Valley,and Coleville it will remain rather smokey. Smoke is forecast to return overnight, but this may begin to improve by daybreak Monday due to north winds associated with a dry cold frontal passage. The big question is how much smoke will be trapped under the inversion and when this will mix out. Marked improvement should be noticeable by mid- morning at the latest, including the Greater Reno/Carson City areas. By Monday night into Tuesday, winds shift to the east northeast behind a dry cold front, which will transport smoke away from the region, finally improving air quality for at least a couple days. * WIND: The backdoor front will bring breezy north winds late today through Monday, with some gusty northeast to east winds possible along Sierra ridgelines Monday night into Tuesday. This along with a drier air mass behind the front will bring near critical fire conditions for some locations. Please see the fire weather section below for additional details. * UNUSUAL HEAT: We`ll be near normal temps for a couple of days thanks to the frontal passage, but that`s short-lived as a strong area of high pressure builds into the area. We`re already seeing high probabilities (80-95%) of potentially record- setting heat by the end of the week and into the weekend. In fact, the current forecast high of 100 degrees on 9/6 at KRNO would be the latest 100 degree day on record (previous record 9/4 in 2017). Luckily, we`ll see decent cooling at night, which will help limit the overall heat impacts. We know many likely have outdoor plans for Labor Day Weekend, so be prepared for hot temps. * BIG DRY SIGNAL, BUT MAYBE A FEW THUNDERSTORMS: Overall, the pattern is dry with little chance for storms to form. However, once we get into the weekend, the extreme heat may cause a few isolated thunderstorms to develop, especially over favored terrain in Alpine and Mono Counties. The NBM is giving some credence to this as well with a 10% chance showing up in these locations in the thunderstorm probs. Outside of this, the chance of having any rainfall based on ensemble probs is only about a 1 in 15 chance. In other words, the very dry weather is likely to continue into the second week of September. -Dawn && .AVIATION... Smoke and haze remains the topic du jour for aviation weather, however a dry cold front will change things up a bit late tonight and Monday. Latest HRRR Smoke model shows widespread VFR-MVFR haze today with terrain obscuration persisting. Areas of thicker smoke expected near and south/east of fires by Quincy and Topaz Lake as W/NW winds kick in. Mainly MVFR but some IFR possible. Could see some periods of lower visibility at RTS/RNO after 02z as Quincy plume moves this way. Winds switch to more N/NE late tonight into Monday which looks to shift a lot of the appreciable smoke/haze southward or bank it up in the Sierra. The model has this cool looking smoke front feature right along the wind shift eastward all the way into Utah. So overall we do anticipate improving visibility for spots like RNO, CXP, MEV, NFL around or shortly after daybreak tomorrow. However areas like TRK, TVL, MMH may actually see more restrictions as smoke/haze banks up into the mountains plus inputs from the fire near Topaz Lake. -Chris && .FIRE WEATHER... Gusty N/NE winds and fairly dry air move into the region tonight through Monday and Monday night. Could see some localized near- critical wind (gusts 25-30mph) and low humidity (5-8%) Monday afternoon across zones 423, 429, 458 in West Central and Northwest Nevada. However not widespread nor long enough duration to warrant Red Flags. Pretty abysmal humidity recoveries tonight for much of the region especially on mid-slopes and ridges. Might see some spots in W Nevada and far NE California only recover to the teens. That along with continued NE breezes above valley floors could be a concern for ongoing fires tonight, and possibly again Monday night but humidity does look a little better then. Looking further out our next concern for fire weather is heat related this coming Labor Day weekend. Some really impressive anomalies showing up in ECMWF EPS guidance Friday through Monday with highs near 100 possible in W Nevada cities. In fact we could set a new record latest-100 for RNO, currently September 4th. Fortunately no big winds expected other than typical zephyr afternoon breezes, but the heat magnitude will promote unstable/dry conditions. NBM guidance indicating widespread Haines 6 this coming weekend. This is a concern for any new fire that starts quickly becoming large plume dominated. -Chris && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Springfield MO
949 PM CDT Sun Aug 30 2020 ...UPDATE... Issued at 933 PM CDT Sun Aug 30 2020 Low level stratus clouds were continuing across the eastern half or so of the area late this evening with ceilings less than 500 feet now becoming common in the eastern ozarks. Light if not calm winds, RH near 100% and stratus build down may lend itself to fog development overnight, mainly east of Springfield. Short term models have been insistent that areas near UNO will experience visibilities less than one mile overnight into early Monday morning. It is possible that a Dense Fog Advisory will be needed at some point overnight if the trend continues. 850mb warm air advection will become stronger towards Monday morning as a low level jet across Oklahoma veers towards the area. The RAP does show some isolated elevated convection possibly developing near Sunrise across the area and have some low pops to account for this potential. The other item we are watching is what happens to our northwest tomorrow as a front moves towards the area. 00z guidance coming in (HRRR, ARW, NAMNest, RAP) is in general agreement that showers and storms will move in from the northwest as early as late morning and plow through the area during mid day and into through the early afternoon. There is still some uncertainty on the exact timing as a few models do hold off until late afternoon however several models are trending earlier with arrival.We have increased PoPs around mid day to account for the recent model trends. Some severe thunderstorms will be possible given the progged instability, especially the southern CWA as this area will have more time to destabilize. Damaging winds and large hail are the main threats. Not as concerned about flooding at this time given the progressive nature of the storms and antecedent conditions. Temperatures will be a challenge tomorrow as storms move through during the day. && .SHORT TERM...(This evening through Monday) Issued at 200 PM CDT Sun Aug 30 2020 Cloud have persisted over the area north of nearly stationary west-east oriented sfc front over northern AR. A few light showers are also occurring with weak, ill defined disturbance(s) embedded in westerlies aloft. Hard to see these overall features changing much through early Monday and will go with a persistence forecast (mostly cloudy, light rain/showers at times) Can`t rule out some fog/stratus build down tonight as well. A shortwave moving from the northern Plains into the upper Midwest will push a sfc cold front into eastern KS Monday morning. Weak moisture advection ahead of the front along with some possible convection moving off the front, will increase rain chances late tonight and Monday morning. Hard to pinpoint details, but do have increased pops/rain chances for this time favoring the western cwfa. .LONG TERM...(Monday Night through Sunday) Issued at 200 PM CDT Sun Aug 30 2020 Monday night-Tuesday-Wednesday: The sfc front will stall/weaken over the area during this time. Clusters of convection will be possible as upper level disturbances interact with weak low level moisture advection. Vertical shear could support some semi- organized convection where stronger instability can exist. Moisture (PWATS near/just over two inches) could result in some pockets of higher rainfall rates and will need to monitor for possible flooding. The frontal boundary weakens/loses definition by Wednesday but without a change in air mass will continue to see chances for showers/tstms. Thursday-Sunday+: A stronger sfc cold front continues to be progged to move southeast through the region Thursday with sfc high pressure building into the region Friday-Saturday with cooler/drier air. The sfc high will shift off to the east later Saturday-Sunday with another fairly strong shortwave supporting another sfc cold front moving into the region early next week (Sunday night?). Overall medium range guidance indicates a cool, almost early Fall like pattern with upper level mid latitude westerlies dipping fairly far to the south by early next week opening the door for Canadian air to move into the area. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 601 PM CDT Sun Aug 30 2020 Confidence is not high on ceilings/vis overnight. Ceilings may bounce around between MVFR and VFR at times at the sites, especially BBG and SGF where some stratus may try to develop overnight and build down. Patchy fog is possible at SGF and BBG by sunrise. Dense fog looks to stay east of the sites however will need to monitor for any westward expansion. Winds will stay light and southerly overnight, becoming more southwesterly Monday morning. Showers and thunderstorms may move into the sites Monday morning or afternoon. && .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ UPDATE...Burchfield SHORT TERM...DSA LONG TERM...DSA AVIATION...Burchfield
Area Forecast Discussion
National Weather Service San Diego CA
903 PM PDT Sun Aug 30 2020 .SYNOPSIS... The cooler weather will continue tomorrow before a gradual warming trend begins Tuesday, and continues through the weekend as the heat cranks up again. A few thunderstorms are possible Monday afternoon, primarily for the mountains and the lower deserts. Dry midweek, but monsoon activity may return as early as Friday. Periods of low clouds near the coast can be expected most nights and mornings. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Skies were mostly clear over the CWA again this evening, but monsoon thunderstorms were occurring over western AZ. to the west, marine clouds were slowly forming over the coastal waters and over coastal areas. There was still a weak onshore trend to the high deserts with some westerly wind gusts of 30+ MPH near the desert passes. The 00Z Miramar sounding had a 7.5C inversion based near 1850 FT, which was spot on with yesterday. The mid-level winds had weakened and veered more southwesterly. The dewpoint trace showed some life in the mid- levels, but the sounding was still very dry. The main forecast issue for the next 24 hours is the potential for mountain/desert convection on Monday. The models have latched onto some residual moisture being drawn northward from the remnants of T.S. Iselle. The HRRR has been sputtering a bit with regard to that convection over SoCal, but the latest available run still looks active. The 00Z NAM12 on the other hand now keeps convection south of the International Border. It still shows a mid-level moisture surge though, and moderate instability, so the threat continues. No forecast updates planned. From previous discussion... .Highlights... * Mountain thunderstorms likely Monday; Possible in lower deserts * Warming trend starting Tuesday; Heat building for weekend * Drying out midweek; Monsoon may return by next weekend The marine layer will be back tonight, bringing low clouds to the coast and inland valleys along with locally patchy fog away from the beaches. Monday will be similarly "cool", with temperatures perhaps even a couple of degrees lower than today for some. However, our eyes will be fixed on potential monsoon activity tomorrow afternoon. A noteworthy surge of moisture from the south should contribute to an increase in PWAT, with forecast soundings and hi-res guidance such as HREF suggesting values between 1.3 and 1.7" across much of the area, and even nearing 2" in the Coachella Valley. Instability will favor convection along the eastern edge of our CWA with MUCAPE readily exceeding 1,000 J/Kg, as will the enhanced surface convergence near the mountain ridges. The steering flow looks to be weak out of the west, highlighting the potential for mountain thunderstorms to drift east into the lower deserts, and combined with moderate DCAPE indicated in forecast soundings, hints at some potential for damaging downdrafts as storms drift east off the elevated terrain. Localized flash flooding will be possible. PoPs in these areas have been raised for tomorrow afternoon to reflect the favorable monsoon setup, in line with output from hi-res models including HRRR and our local WRF. Monsoon chances will evaporate as we dry out considerably Tuesday through Thursday. High pressure building off the PacNW coast will gradually expand southeastward through the week, forcing a steady but continuous climb in temperatures through late week and into the weekend, and likely restricting marine layer clouds somewhat to mainly coastal zones. Regarding the late week heat...ensemble spread in temperatures has actually increased relative to yesterday, especially for next weekend. Although confidence is high that we`ll see a notable upward trend in temperatures through at least Saturday or Sunday, there`s still significant uncertainty when it comes to just how hot it may get. A potential increase in moisture further adds to the uncertainty, whilst also hinting at a possible return of monsoon convection perhaps as early as Friday. Plenty of details still to hatch out as we wait for guidance to converge on a "most likely" scenario. && .AVIATION... 310300Z...Coast/Valleys...Stratus is slowly forming along some of the San Diego County beaches and will spread inland this evening. These clouds will be reaching coastal airports in SD County in the next couple of hours and closer to 06Z in Orange County. These clouds have bases around 1500-2000 ft MSL and will extend up to 30 mi inland with higher terrain obscured. Like last night, VCTY KONT may see some brief cigs 12-16Z Monday. Local vis 1-3 miles will occur in the valleys 08Z-16Z Mon. Clearing will occur for all areas from inland locales to the coast 16Z-19Z. Mountains/Deserts...Mostly clear skies with unrestricted vis will prevail through Mon morning. We continue to monitor the chance of TSRA Monday afternoon after 18Z, with highest chances being for the mountains and desert slopes of San Diego and Riverside Counties. && .MARINE... No hazardous marine weather is expected through Friday. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...10/Rodriguez AVIATION/MARINE...APR
Area Forecast Discussion
National Weather Service Shreveport LA
958 PM CDT Sun Aug 30 2020 .SHORT TERM.../Tonight/ The evening sfc analysis indicates that the stationary outflow bndry over portions of Deep E TX into Ncntrl LA from the early morning convection has washed out, with mid 70s dewpoints again having advected back N across the region with the return Srly bndry lyr flow. Mostly quiet conditions are expected through much of the overnight hours, although the short term progs continue to suggest weak shortwave perturbations that will shift E along the Red River Valley of N TX/Srn OK late. A 30-40kt SWrly LLJ will develop over the Srn Plains tonight, with large scale forcing adequate enough for the development of isolated to sct convection that may develop late and possibly affecting areas NW of the I-30 corridor of NE TX/SE OK/SW AR late. While there was some agreement amongst the hi-res ensembles with development over these areas prior to daybreak Monday, the latest HRRR suggests that any development will be delayed until by or shortly after 12Z. Given the brief window still possible, have largely maintained low chance pops as is late for the far NW zones, with slight chance pops closer to the I-30 corridor. Still expecting low stratus development late tonight over Deep E TX/Ncntrl LA, which will quickly spread N across much of the region through daybreak, thus ending the temp fall and provide little relief to those relief efforts across N LA/SCntrl AR. Did make a few minor tweaks to min temps tonight to reflect the latest trends, with hotter/more humid conditions expected Monday as max temps climb to the mid/upper 90s, and heat indices likely exceed 105 degrees over much of E TX/N LA. However, some relief to the heat will be possible across Deep E TX/Ncntrl LA with a weak afternoon seabreeze convection, as well as additional sct convection possible across portions of extreme NE TX/SE OK/SW AR. Zone update already out...grids will be available shortly. 15 && .PREV DISCUSSION... /issued 658 PM CDT Sun Aug 30 2020/ AVIATION... VFR conditions will continue this evening through at least a portion of the overnight hours, with areas of AC cigs developing/shifting E across the region. Low MVFR cigs are expected to develop by/after 09Z Monday across portions of Deep E TX/Ncntrl LA, and will spread NE across the remainder of E TX/N LA/SW AR by/after 12Z, before slowly lifting by mid to late morning. These cigs may briefly become IFR at LFK/MLU/ELD, before VFR cigs return by late morning/midday. Some sct convection may develop late tonight across SE OK/Nrn sections of SW AR, but should remain N of the TXK/ELD terminals. An extensive cu field is expected at least through mid-afternoon before they begin to scatter out, although isolated to scattered convection should develop Monday afternoon across portions of Deep E TX/Ncntrl LA with a Nwd advancing seabreeze, with additional sct convection again possibly affecting portions of extreme NE TX/SE OK/SW AR. However, confidence remains too low to mention in the 00Z TAFs attm, although amendments may be needed in future TAF issuances. S winds 4-8kts tonight will become SSW 7-11kts after 15Z. /15/ && PREV DISCUSSION... /issued 252 PM CDT Sun Aug 30 2020/ SHORT TERM.../Tonight through Monday Night/ Vis Satellite telling the tale currently with a strong afternoon cu field across our southern and eastern third along and ahead of an outflow boundary that pushed through our region earlier this morning. We are seeing some convection along and ahead of this boundary late this afternoon across our extreme southeast zones but this convection should dissipate with the loss of daytime heating. Upstream, remnant MCV`s can be seen spinning just south of the I-20 Corridor in NE TX and another one across the Middle Red River Valley of NE TX/SE OK and SW AR. The outflow boundary helped to scour out much of the low level moisture this afternoon and the remnant cloud cover has held ambient temperatures and dewpoint temperatures in check today, thus limiting instability. High res models are in good agreement suggesting we will see little if any convection overnight, except for the possibility of isolated convection along our extreme northern zones where higher thetae ridging exists at the 850mb level. Descent boundary layer moisture return is forecast for overnight which should help to get the stratus back northward and likely encompassing much, if not all of our region by sunrise Monday Morning. This will help to bring dewpoints back up overnight and keep them up through the day Monday which means the heat returns for Monday as well even through much of our region saw a break from the heat today. Concerning the heat advisory, extended it through Monday at 7 pm for all but our far northern zones as this area may see a little more in the way of cloud cover which should help to hold temps in check more so than across the I-20 Corridor and points south. Cu field should scatter out by late morning through the afternoon but not before we see isolated to scattered convection areawide Monday Afternoon. There will be no boundary around to scour out the dewpoints on Monday and with only marginal mixing expected during the afternoon, should see a return to afternoon heat indices reaching 105 to 110 degrees. Monday Night, upper flow begins to take on a slight southwestward tilt and there is descent model consensus between the HREF, GFS and CMC to suggest disturbances in this flow will set off scattered to numerous showers and thunderstorms once again across the Middle Red River Valley of NE TX, SE OK and SW AR overnight. Some of this could be strong to severe with locally heavy rainfall once again a threat. 13 && LONG TERM.../Tuesday through Saturday night/ Model consensus is now good on a potentially troubling heavy rain scenario setting up across our northwestern Arklatex zones from the start of the long term through at least Wednesday morning (but perhaps even through Thursday morning). A cold front looks to move into these regions and stall while "cut-off" upper level energy well to our west sets up perturbed southwest flow over the top of the boundary. The combination of moisture, lift, and instability over a long period of time in these areas should allow for multiple rounds of showers and storms over locations which have already received more than their fair share of rain over the past few weeks. This scenario will keep these northwestern locations a little cooler than average, but expect the heat and humidity to persist over much of the rest of the region where chances of rain will be much less. In fact, our latest official forecast numbers suggest some areas of the CWA south of I-20 may have to have the heat advisory through Monday eventually extended through Wednesday. Model solutions continue to instill far less confidence that the hot and muggy conditions of August will break down any time this week. The aforementioned front moving in and stalling for early the period should eventually lift back to the north while other frontal passages headed this way from the north likely run out of steam before they arrive. The overall upper level CONUS flow pattern does show signs of changing up within the next 6 to 8 days with the resulting flow regime giving confidence a cold front will eventually arrive, although confidence of arrival time is less than great (i.e., it could push toward the middle of next week). Ergo, expect the latter half of this week to feature at least some rain chances in all areas with an outside potential for heat advisory conditions to persist in many locations. /50/ && .PRELIMINARY POINT TEMPS/POPS... SHV 78 95 77 94 / 0 20 20 30 MLU 77 94 76 94 / 0 40 20 30 DEQ 74 90 75 86 / 30 40 60 80 TXK 76 91 75 88 / 20 40 50 50 ELD 75 92 75 90 / 10 40 20 40 TYR 79 97 77 95 / 10 20 20 50 GGG 77 97 77 95 / 0 20 20 40 LFK 78 98 77 97 / 0 30 20 20 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...Heat Advisory until 7 PM CDT Monday for LAZ001>006-010>014- 017>022. OK...None. TX...Heat Advisory until 7 PM CDT Monday for TXZ096-097-108>112- 124>126-136>138-149>153-165>167. && $$ 15
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Monday) Issued at 350 PM CDT Sun Aug 30 2020 Another round of showers and storms is possible Monday morning, which may linger into the afternoon. The early afternoon atmospheric setup features a rather amplified northern stream longwave pattern along the U.S./Canadian border with a notable trough digging southeastward over Montana. At the surface, a corresponding Pacific front stretches from the Red River Valley of the North southwestward to near Goodland as of 20Z. This boundary will be the focus for thunderstorm development later this afternoon and evening, with the best threat along a narrow axis of 65 F dewpoints located over central Nebraska to southeastern South Dakota. Across eastern Kansas, low stratocumulus (later pure daytime cumulus) clouds persisted for longer than expected and helped temper high temperatures slightly. The western edge of a +20 to 25C H850 EML is advancing rapidly eastward into central Kansas early this afternoon, its leading edge denoted by a rapid erosion of the western cloud shield. For the rest of the afternoon, subsidence associated with the EML overspreads the forecast area and should result in a steady decrease in cloud cover. Uncertainty in convective trends increases beyond late this afternoon. CAM solutions vary on how far south convection initiates along the frontal boundary and the degree of H800-850 moisture recovery ahead of the front. The HRRR in particular has presented a very dry solution for most of its runs today while the NAMNest/RAP/NMM/ARW are further south and develop a cold pool that could serve as the focus for redevelopment throughout the night. The overall trend has been to delay the onset of precipitation until after 06Z in the NW forecast area, possibly not reaching the Topeka area until close to sunrise. Did not want to cut back PoPs too far in case a more established cold pool is able to accelerate faster than the frontal motion. However, it may be difficult for convection to sustain itself outside of the narrow pre-frontal theta-e axis given the strength of the warm sector EML, so felt confident tightening the PoP gradient to some degree. Whatever convection does develop should be progressive in nature with the frontal motion of 15 kts through the nighttime hours. The forward motion of the front may slow during the day on Monday as the upper trough pivots and begins to lift northeastward, with the attendant height falls likewise shifting away from the region. Convection will be elevated in nature with MUCAPE values of 1500 to 2000 J/kg. Deep shear will be somewhat lacking with storm- relative H500 flow of less than 10 kts. Flow in the upper half of the troposphere increases to around 30 kts with the region on the edge of the northern stream jet streak, thus cannot rule out some degree of organized storm structures capable of producing hail or wind. Monday`s weather hinges heavily on how tonight`s convective trends evolve. There is a signal in the HRRR that if convection fails to materialize overnight, development along the near surface to H850 front could take place during the day on Monday, mainly southeast of a Minneapolis to Marysville line. An unmodified environment would be capable of supporting robust updrafts with NAM/HRRR hodographs conceivably supporting shallow elevated mesocyclones and a resultant hail threat. The current forecast is really an amalgamation of two forecasts, one in which we either see overnight/early morning convection and little in the way of redevelopment in the afternoon, or a dry overnight and development late Monday morning/early afternoon. Outside of the storm threat, did add some patchy fog in the eastern river valleys for a short period tonight. Light southerly winds and increasing lower tropospheric moisture advection may result in some shallow fog in low-lying areas, but anvil cirrostratus spreading southeastward from the convection in Nebraska should curtail the fog threat around 09Z. Highs for Monday look to top out in the mid-70s in north central Kansas, reaching into the low 80s in east-central Kansas prior to the frontal passage. .LONG TERM...(Monday night through Sunday) Issued at 350 PM CDT Sun Aug 30 2020 A seasonably cool forecast is on tap for the rest of the week with conditions drying out after Tuesday. Renewed convective growth is expected along the surface front now located over central Oklahoma into southeast Kansas Monday evening. As the lower-tropospheric baroclinic zone lifts northward Monday night into Tuesday morning in response to the next upstream upper level shortwave and interacts with the exit region of the subtropical jet, some of this precipitation should overspread the forecast area. Model solutions vary on the degree of instability available for any convection, but impacts associated with this northward theta-e push should be on the low side. Periodic showers and storms are possible southeast of I-35 Tuesday and Wednesday within the belt of unsettled southwesterly flow, but should remain mostly south of the region with surface high pressure building eastward. A second surge of Canadian air spills southward on Thursday, with the frontal passage possibly being a source for convective development. High pressure dominates the weather pattern for Thursday night through Friday, with a third wedge of cooler air descending equatorward next weekend. Details on the timing of next weekend`s front, and any associated convective hazards, remain scarce at this point owing to a modest 24-hr spread in the medium range guidance. Temperatures for the forecast period look to remain at or below average with highs in the low to mid 80s. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 625 PM CDT Sun Aug 30 2020 The potential for a line of thunderstorms impacting the terminals has increased. Short term guidance continues to highlight the 10-14Z timeframe for storms impacting all terminals. Gusty northwest winds and reduced VSBY from heavy rainfall will be the primary concerns. MVFR CIGS will likely persist through midday before VFR conditions return. Additional storms are possible during the afternoon but confidence is too low to mention at this time. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Skow LONG TERM...Skow AVIATION...Baerg