Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/01/21

Area Forecast Discussion
National Weather Service Denver/Boulder CO
806 PM MDT Wed Jun 30 2021 .UPDATE... Issued at 752 PM MDT Wed Jun 30 2021 N/S oriented boundary moving west of US 85 toward I-25, with a surface cyclonic circulation just west of DIA. Boundary along with surface based CAPE 500-1000 j/kg along the I-25 corridor & along the Palmer divide this evening supporting widely scattered convection. Persistent slow moving cluster of thunderstorms in northwest Weld county, and raised pops in that area for a few more hours. Other showers in the vicinity of KDEN popping up and dissipating, not even making thunder. Lowered pops through midnight northeast plains where nothing is going on yet. HRRR remains bullish on bringing showers out of the foothills and along Palmer Divide, and left chances down there overnight spreading onto the eastern plains after midnight. Tweaked the POPs with this update, blended in current temperatures, and left the overnight lows alone. && .SHORT TERM...(This evening through Thursday) Issued at 240 PM MDT Wed Jun 30 2021 Scattered showers and thunderstorms have begun to form across the higher mountains and east slopes early this afternoon. So far, instability is marginal with CAPE VALUES 400-800J/KG while storm motions around 10kt. There has been just enough motion to keeping storms moving to prevent any major flooding across higher terrain. Across lower elevations, outflow boundaries may spark storms later this afternoon and evening which most models are picking on best focus for storms east and south of Denver and across Palmer Divide. Confidence is low on how far east the convection develops this evening, but certainly coverage more isolated out on the plains. The 50kt jet streak across southeast Colorado does slowly sag further south and east but still may have some interaction in shower development overnight and will keep in some low pops. The southeast low level flow also appears to drag in additional moisture from Kansas. Will also have chances of showers across the plains in the morning as well. The main concern for Thursday is a higher threat of flash flooding across the burn scars and adjacent areas in the mountains and adjacent plains. The weak upper trof remains across Utah with a continued light southwest flow aloft over Colorado. There is a definite upswing of moisture across the area with precipitable water values up over an inch across all the plains. The model forecast instability increases with SFC based CAPES increasing upwards of 1500j/kg. However with increased cloud cover, wondering if will come up a bit short and actual CAPES remaining under 1000j/kg. It also appears storm motions may end up being similar to today with 10kt storm motion from the west and southwest. The latest HRRR reflectivity of storms has actually surprisingly decent storm motions which would reduce the flash flood threat. Regardless, the threat will be higher on Thursday afternoon then today, but confidence not high enough to issue a flash flood watch. Temperatures will be a bit cooler with more cloud cover than today. Will still go with likely pops in most areas Thursday afternoon given the moisture uptick, so overall not many changes in forecast. .LONG TERM...(Thursday night through Wednesday) Issued at 240 PM MDT Wed Jun 30 2021 Isolated areas of heavy rainfall will likely continue into the early overnight hours Thursday night. Activity should decrease fairly quickly after sunset surface stability increases, with just a few overnight showers after midnight. Friday`s pattern is largely the same as Thursday, with a few subtle differences. Temperatures are likely to be just a little warmer, with surface dew points a couple degrees drier. GFS/ECM both suggest that CAPE across the area will be almost identical to Thursday. Forecast soundings show mean-cloud layer flow of about 10kt during the afternoon, with a fairly shallow warm cloud layer. Still, the current thought is that heavy rainfall will continue to be a concern over most of the high country. PWATs will still be near an inch across the Foothills and near 3/4 of an inch west of the divide. Guidance does try to keep the convective focus across our higher terrain unlike Thursday, and the primary concern for the day will be for burn area flash flooding. The pattern does slowly get warmer and drier this weekend, with chances for afternoon thunderstorms both Saturday and Sunday. The flow aloft does strengthen a touch both days, which should lead to slightly faster storm motions, but there will likely be some flash flooding concerns again over our burn areas. Highs across the plains will reach the upper 80s to low 90s. Monday will perhaps be the driest day of the week, with scattered storms for the mountains and an isolated storm or two along I-25. A shortwave should bring a push of slightly cooler air and increased thunderstorm coverage, with more uncertainty Wednesday and beyond. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 543 PM MDT Wed Jun 30 2021 VFR, with scattered showers and maybe a rumble of thunder this evening. We left VCTS in for Denver through 02z in lingering instability and colliding outflow boundaries, then VCSH for a few more hours. Hi resolution models showing a band of convection moving out of the foothills and through the TAF sites 03-05z so left VCSH through then. Boundary/Denver Convergence Zone has set up NNE/SSW oriented, just west of KDEN and KAPA and just east of KBJC. Forecast it to remain stationary through the evening. Toward morning a Denver Cyclone will set up again, but details on where are elusive. For the TAF went with HRRR model solution, with SSW wind becoming east in the afternoon, then Thursday afternoon convection after 20z. && .HYDROLOGY... Issued at 240 PM MDT Wed Jun 30 2021 Thunderstorms so far have been on the weaker side in the mountains this afternoon given the marginal instability while storm motions are moving storms enough to limit the threat for flooding. There will be an increasing threat of flash flooding over the burn scars on Thursday afternoon with higher moisture levels. However storm motions again maybe quick enough to prevent any major flooding. For now confidence too low to issue a flash flood watch. Elevated flash flooding threat will continue on Friday with slow moving thunderstorms likely again across the burn areas. There is some uncertainty regarding the amount of moisture and instability available Friday afternoon, but conditions will generally be similar to Thursday. The flash flooding threat should decrease through the weekend as the pattern gradually turns warmer and drier, but heavy rainfall will still be possible each day with scattered thunderstorms likely. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Hanson SHORT TERM...Entrekin LONG TERM...Hiris AVIATION...Hanson HYDROLOGY...Entrekin/Hiris
Area Forecast Discussion
National Weather Service Louisville KY
844 PM EDT Wed Jun 30 2021 .Forecast Update... Issued at 840 PM EDT Wed Jun 30 2021 Radar continues to show isolated convection across our CWA this evening. Brief heavy downpours and wind gust of near 25 mph seem to be the main impacts from these cells. Expect more of the same as we go through the rest of the evening and into the first half of the overnight. Few clusters of rain/storms have been trying to work out of far southwestern Indiana into our CWA but have weakened as they move eastward, and with the loss of daytime heating expect more weakening to occur. Hi-res models haven`t initialized well with much of the ongoing convection this evening but continue to advertised a brief lull in activity until about 06z to 07z. Have adjusted our PoP grids to reflect this lull and isolated nature of convection. As the upper level trough pushes southward overnight, expect possible redevelopment of shower and possible storms between 06z-12z in southern Indiana and northern Kentucky. Forecast soundings continues to maintain SBCAPE values around 2000 J/kg as well as a nice saturated column, so some thunder is possible with any activity. Heavy rain will also be an issues as PWAT values remain near 2.00" and dew points in the low/mid 70s. Localized flooding would be the main concern from any early morning showers and storms, especially for the morning commute along the I-64 corridor. No other changes have been made to the forecast grids. && .Short Term...(This evening through Thursday) Issued at 315 PM EDT Wed Jun 30 2021 KLVX began showing pop up showers initiate along the I-64 corridor around 18z. SPC Mesoanalysis reveals MLCAPE of 1500-2000 J/kg and steep low level lapse rates of 7.5C/km in a very moist airmass with PWATs greater than 1.9". Sfc temperatures have remained in the mid 80s under an increased mix of clouds. Despite temps staying below 90F, dewpoints have remained in the low 70s, making for quite a muggy day across the region. Expect to see showers and storms continue this afternoon and evening, primarily across southern IN and north central KY as the sfc cold front currently stretching across northern IL/IN continues to sag southward tonight and interacts with our moist airmass. Upper level shortwave will be digging southward overnight helping to push the slow moving sfc boundary further south and provide additional lift to our region. Hi-res guidance suggests a brief lull in precip activity this evening, but renewed development looks to take place late tonight or during the overnight hours, focused over southern IN and expected to spread southward through the region as the front approaches. RAP soundings suggest we`ll hold on to sfc based instability tonight and a saturated column, so expect to have at least some thunder mixed in with numerous showers. Weak flow aloft will help limit any recognizable shear, so no severe wx is expected. By tomorrow morning, widespread showers and storms are expected across the region within a continued moist environment. CAPE values will be meager with overcast skies, so continue to think storms will remain sub-severe for tomorrow. Precip chances continue into the afternoon hours. Main hazards will be intense rainfall rates and slow storm motions, leading to localized flooding concerns. OHRFC 1 hour FFG is around 2 inches, and 3 and 6 hour FFG is roughly 3-4 inches. Think we`ll have a chance of meeting or exceeding the 1 or 3 hour FFG with a slow moving storm that puts down impressive rainfall rates. Temperatures for tomorrow will remain in the upper 70s to near 80F, but should be another muggy day with dewpoints once again around 70. .Long Term...(Thursday night through Wednesday) Issued at 230 PM EDT Wed Jun 30 2021 As we head into Thursday night, expect showers and storms to taper off from northwest to southeast as the surface cold front finally pushes through the area. With the upper trough and cold front exiting off to the east by Friday, we will transition to a drier and somewhat cooler pattern as surface high pressure along with ridging aloft begin to build over the area. Under northerly flow behind the front, low temperatures Thursday night into Friday morning will generally be in the lower to mid 60s. Low temperatures will then trend even cooler as we head into the weekend, with overnight lows in the mid 50s to lower 60s. High temperatures are also expected to remain below climatological normals Friday and Saturday, topping out in the upper 70s to lower 80s. By the start of next week, the upper pattern will begin to flatten out a bit while southerly flow starts to take hold in the lower levels as high pressure drifts to the east. This will result in temperatures warming near/slightly above normals once again with highs in the upper 80s to lower 90s through the end of the period and overnight lows in the upper 60s to lower 70s. May begin to see some diurnally driven precip chances in the afternoon and evening hours next week; however, will maintain just slight chance PoPs at this time with lower confidence in any finer details. && .Aviation...(00Z TAF Issuance) Issued at 715 PM EDT Wed Jun 30 2021 Main concern this evening is impact of convection. Best coverage is currently around HNB, but enough dying CBs near SDF and LEX that all are worth initializing VCTS. Will also include a TEMPO for IFR vis in heavy rain at HNB, and perhaps later this evening at SDF. The latter will be a last-minute call at issuance time. Much of the overnight will be dry with light winds and a mid-level ceiling. Precip coverage increases again just before daybreak with the slow approach of the front. Look for low-end MVFR cig and vis for a good chunk of the day under widespread showers. Best chances for embedded thunder will be farther south and east in BWG and LEX, so we`ll include VCTS there. Lowest ceilings expected at HNB and LEX where we could go IFR at times. Will see breaks at times in the rain, but not expecting improvement in ceilings until the last few hrs of the TAF in HNB and SDF, and beyond that in BWG and LEX. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...BTN Short Term...CJP Long Term...JML Aviation...RAS
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
951 PM CDT Wed Jun 30 2021 .UPDATE... Showers and thunderstorms dissipated over the Midsouth with the loss of surface heating, and the extent of stabilizing outflow from afternoon convection. At midevening, GOES IR imagery showed showers and thunderstorms extending from the Ozarks into the Ohio River valley. As midlevel heights slowly fall, some of this activity will affect portions of the Midsouth, from northeast AR through northwest TN. Overnight rain chances will be more limited, but not out of the question, prior to 7 AM. PWB && .PREV DISCUSSION... /issued 709 PM CDT Wed Jun 30 2021/ UPDATE... See the 00Z aviation discussion below. PREV DISCUSSION... /issued 252 PM CDT Wed Jun 30 2021/ DISCUSSION... Convection continues to develop across the Mid-South this afternoon along the many outflow boundaries that are located across the area. The latest run of the HRRR is still struggling to initialize with what is occurring. Expect the numerous showers and thunderstorms to continue into the early evening, but should gradually dwindle near sunset due to the loss of daytime heating. Locally heavy rainfall will be the main threat from the storms as the storms are not moving much. Chances for convection will continue especially across Northeast Arkansas, the Missouri Bootheel, and Northwest Tennessee for the remainder of the night as convection that is occurring across Missouri near the vicinity of the approaching cold front begins to sink south into the Mid-South. The cold front will sink south into the Mid-South Thursday into Thursday Night. Expect a repeat of today with numerous showers and thunderstorms occurring across the area. Storms could become strong during peak heating. Gusty winds and locally heavy rainfall will be the main threats. Drier air will begin to filter into the region on Friday behind the front. Although, chances for showers and thunderstorms will still occur across North Mississippi on Friday. By Friday Night, SFC high pressure will begin to build into the region. The high pressure will provide a beautiful Independence Day weekend across the region. Expect low humidity with highs in the 80s. Humidity levels will begin to creep back up by Tuesday next week as an upper ridge builds over the region. A weak disturbance may get caught underneath the ridge which will bring rain chances back to the Mid-South Tuesday into Wednesday. KRM && .AVIATION... 00Z TAFs All showers and storms have died out in the past hour. Storms currently over southeast Missouri may move into JBR around midnight and weaken, while all other sites will remain dry overnight. A cold front will approach from the northwest tomorrow afternoon. SHRAs and TSRAs will begin scattered in the afternoon hours and increase in coverage by early evening along a frontal boundary. Lower CIGs and VSBYs will accompany the front as well as prevailing SHRAs and TSRAs. AC3 && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion
National Weather Service Phoenix AZ
441 PM MST Wed Jun 30 2021 .UPDATE...Updated Aviation Discussion. && .SYNOPSIS... Scattered showers and thunderstorms will be common over the higher terrain and more isolated on the lower elevations the rest of the week. Strong windS, localized blowing dust, and localized heavy rain/flooding will be the main impacts. A slow decline in storm activity begins by early next week. Temperatures will be near, to slightly below, normal the rest of this week before increasing a bit early next week. && .DISCUSSION... Strong convection developed early today, before 18Z, over the northern AZ high terrain, with the strongest activity in the Prescott area. An MCV also developed in southern San Bernadino county CA and moved east through La Paz county this morning with some embedded strong storms and moderate rain. The MCV is still pushing east into portions of Maricopa county early this afternoon, with an outflow pushing out ahead of it, but the convection with it has mostly dissipated. Going forward through the rest of the afternoon, the atmospheric flow pattern, dynamics, and outflows may play a significant role in how convection evolves. Water vapor satellite shows a prominent upper level circulation over the Great Basin and weak anticyclonic circulation over northern Baja California. An enhanced gradient between the two features may have aided the MCV this morning. A general divergent flow pattern is seen over the central and eastern AZ with very week steering flow. 850-300mb mean flow from RAP mesoanalysis is around 5-10 kts out of the west to southwest. With the week steering flow, storm motion will be slow and likely driven mostly by outflows. With slow storm motions and non-existent shear, ordinary storm modes are expected. With SBCAPE values upwards of 1000-1500 J/kg and PWATS around 1.2-1.5" analyzed over central AZ, intense saturated updrafts are expected. As has already been seen along the Rim and in Yavapai county. Strong storms may be brief, suffering from waterloading, but still could produce significant impacts. DCAPE is high, around 1000-1300 J/kg, over south-central, so strong outflows will be a threat through the afternoon. 12Z HREF probability of >35 mph is around 50-60% with max wind gusts around 45-55 mph, which seems a little low, but could be attributed more to the moist environment. With the elevated moisture, slow storm motions, and high instability, localized flooding impacts may be the biggest concern this afternoon, especially with any storms that become anchored to mountain peaks and ridgelines and/or develop over burn scars. Rain rates may be a little tricky at lower elevations, with HREF showing upwards of 0.5-1.0"/hr. A gage near Crown King in Yavapai county measured ~1.0" in 10 minutes. So there is evidence of the potential for higher rain rates. A special 19Z sounding was launched out of Phoenix and shows a virtually uncapped surface environment, with ~1000 J/kg SBCAPE, ~1.4" PWATS, and 10.6 g/kg mixing ratio. Forcing is the only thing missing at this point. Storms so far have been limited to higher terrain, but given the sounding, a strong outflow may be enough to fire off storms over the lower deserts. Activity, in general is not expected to last long past sunset this evening, dissipating with the loss of heating. .PREVIOUS DISCUSSION... For Thursday, some sort of inverted trough may finally move deeper into AZ - possibly aided by the sheared out mid/upper level remnants of Enrique (weakens to a Depression today over southern Gulf of California) and the westward advance of high pressure centered to our east. The track, or even presence, of any such perturbations remains quite uncertain. But, there may also be a little bit more moisture to work with (associated with Enrique`s influence). Ensemble data suggests a little bit more moistening yet on Friday. As the moisture availability increases, the potential for storms to produce heavy rain also increases. That being said, the best precipitable water values look to be over southwest AZ as opposed to south-central AZ. The threat would tend to be pretty localized as well. Look for temperatures to be near average. A slow downtrend in moisture (PWAT) begins as early as Saturday or as late as Monday. Meanwhile, the upper high centered over Texas is advertised to become centered over Arizona over the weekend. With weak steering flow and decreased instability, that would tend to hinder storm development on the lower elevations. But, if enough moisture lingers and steering flow isn`t too weak, there could be a period of relatively better chances for the the south-central AZ deserts. But, the high isn`t anticipated to be super strong so we`re not anticipating an excessive heat event through Tuesday. && .AVIATION...Updated at 2345Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: An outflow boundary from the north has moved through most of the TAF sites within the past hour or so, producing 15-25 kt northerly (340-020) gusts. These gusts will likely continue for the next hour or so before speeds begin to subside through the evening as directions become northeasterly, and then easterly for the overnight hours. A few showers have tried developing behind the boundary but storm development continues to struggle over the Valley, casting doubt for storms over any particular terminal. Chances for storms in the terminal area and/or at any site is low, between 10-20% now through 02Z, before negligible later tonight. Storms will continue to be more active north and east of the Valley, potentially affecting arrival/departure gates, as well as creating new outflows. For tomorrow, conditions will likely remain in place for a "rinse and repeat" pattern with Thursday unfolding similar to today. Southeast California/Southwest Arizona including KIPL and KBLH: There are no major aviation weather concerns through this TAF period. At KIPL, southeasterly winds will predominate through much of the period, at speeds of 8-13 kts, and occasionally stronger gusts. Westerly afternoon winds may develop Thursday. At KBLH, southerly winds will prevail with speeds frequently reaching 12-18 kts. Thunderstorm chances for either site are low, at around 10%, with storms likely to remain well south of the US/MX border and over the Kofa range in western AZ. These storms could send outflows towards either site late tonight but confidence for that occurrence is too low to mention in the current TAFs. && .FIRE WEATHER... Saturday through Wednesday: High pressure is expected to become centered over Arizona over the weekend. A slow decline in atmospheric moisture is also anticipated to begin by early next week. Thus, the best potential for storms with locally heavy rain looks to be this weekend. Otherwise, a familiar Monsoon season pattern will be in place with storms primarily focused over the higher terrain producing outflows that spread to the lower deserts and in turn generate isolated new storms. Temperatures will start off this period at, or slightly below, normal followed by a a little bit of warming. Min RH values will generally be in the 20-30% range through Sunday before decreasing to 15-25% on Tuesday. Max RH values will follow a similar trend but with decreases starting sooner. For instance, Max RH values will be 40-60% most places (less eastern Riverside County) through Monday morning before decreasing to 30-50% most places by Tuesday morning. Apart from thunderstorms, wind patterns will follow familiar diurnal patterns. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Benedict PREVIOUS DISCUSSION...AJ AVIATION...AD FIRE WEATHER...AJ/Benedict
Area Forecast Discussion
National Weather Service Pueblo CO
317 PM MDT Wed Jun 30 2021 .SHORT TERM...(This evening through Thursday) Issued at 316 PM MDT Wed Jun 30 2021 ...Heavy rains and marginal severe storms possible next 24 hours... Currently... Low level moisture has noticeably increased over the region during the last 24 hours as dwpts over the region were in the mid 50s to mid 60s across the plains, with 40s in the valleys. Scattered storms were noted at 2 pm, mainly over the higher terrain, while showers were noted over the plains extending SW-NE from KTAD to KLAA. Ambient temps were in the 70s most locations in the valleys and plains. Rest of Today into Tonight... Main concern is a wx disturbance moving northeast across the SW mtns and heading towards the Pikes Peak region this evening. This disturbance has initiated convection over the SW mtns and is expected to cause areas of heavier rain over the Pikes Peak region late this afternoon and especially this evening. Latest runs of HRRR and NAM NEST guidance show up to 1 to 2 inches of rain will be possible by this evening across the greater Pikes Peak region. It should be noted that the hour by hour runs of the HRRR guidance has been quite persistent with this solution throughout today. Over the remainder of the region, showers and storms will be less prevalent. Tomorrow... We should see a very active day across the region. A more substantial disturbance is fcst to move through the region and plenty of low level moisture will be in place. In addition...20-30 knts of shear will be in place and winds at jet level will be rather strong. A favorable theta-e axis (1000-2000 J/KG CAPE) is forecast to run from the Pikes Peak region down towards KSPD, with this favorable instability feeding the convection which is expected to initiate over the mtns by mid afternoon. Given these favorable thermodynamic fields which will be in place, we are going to see two weather threats affecting the region tomorrow. The first will be heavy rain capable of producing flash flooding over the greater Pikes Peak region (including Fremont/Wet mtns/Pueblo/Pikes Pear area); with the 2nd threat being severe thunderstorms over most of the plains. The most favorable corridor for severe will be from KCOS to KSPD along the favorable theta-e axis. All svr wx types will be possible as LCLs will be rather low. It is not out of the question that 1-3 inches of rain could occur. This potential heavy rain, combined with the locally heavy rain which is expected to fall this evening, will allow for the potential of flash flooding, and a flash flood watch has been issued. Guidance has been consistent at pegging the area mentioned above for the heavy rain for the last several days, and confidence is rather high that flash flooding will be possible tomorrow, especially if locally heavy rains fall this evening in the Pikes Peak region. .LONG TERM...(Thursday night through Wednesday) Issued at 316 PM MDT Wed Jun 30 2021 Main Forecast Concerns/Challenges: 1) Heavy rain threat Thursday night with possible continuation into Friday 2) Daily chance for thunderstorm activity, especially over the mountains 3) More seasonal temperatures return by Saturday Thursday night through Friday...As a continuation of all that was mentioned in the short term discussion about tomorrow, an abundance of llvl moisture and favorable dynamics means that both a heavy rain threat as well as a severe threat will likely continue well into the evening tomorrow. The question that remains to be answered will be where the precip bullseyes will eventually fall. Activity will likely persist until after midnight, though the heaviest rainfall should taper off just prior, and the current end of the watch at 11 PM looks reasonable. A less volatile scenario is forecast for Friday, though llvl moisture will remain in place, there will be lighter southeast surface flow and the upper ridge of high pressure will be slow in gathering strength. Therefore, showers and thunderstorms will once again initiate over the eastern mts right around midday. Temperatures are forecast to warm into the 70s to around 80F for most locations. Saturday through Monday...An upper level ridge of high pressure builds over the Four Corners region, and strengthens over the holiday weekend. There will be a daily shot of convection, mainly tied to the higher terrain, developing during the aftn and persisting into the evening. Flash flooding threat to area burn scars will need to be assessed on a day to day basis, as it will be hit and miss due to the convection. Temps are forecast to start climbing back up to seasonal normal levels as well, with highs in the upper 70s to lower 80s for the high valleys, and in the 80s to around 90F for the plains. Tuesday and Wednesday...The upper ridge remains strong but shifts slightly to the west, as an upper disturbance crosses MT, WY, the Dakotas and NE both days. This shortwave will help enhance convection chances as well as areal coverage both afternoons, but especially for Tue where QPF values increase significantly. Temps are expected to remain at seasonal levels. Moore && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 316 PM MDT Wed Jun 30 2021 Thunderstorms will be more prevalent over the region starting later today and lasting into the Holiday weekend. The overall best chance of thunderstorms capable of heavy rain, gusty winds and possibly small hail will be in the Pike Peak region late this afternoon and evening and especially tomorrow afternoon and evening. MVFR to brief IFR will be possible in the heavier storms which will occur. At KPUB, thunder chances today ar quite low, but there will be a much better chance of strong storms tomorrow afternoon. At KALS, only isolated afternoon and evening activity is possible. && .PUB WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch from Thursday afternoon through Thursday evening for COZ076-077-079>086. && $$ SHORT TERM...HODANISH LONG TERM...MOORE AVIATION...HODANISH
Area Forecast Discussion
National Weather Service Blacksburg VA
915 PM EDT Wed Jun 30 2021 .SYNOPSIS... Upper ridge begins to shift southward tonight as a cold front slowly approaches from the northwest to end the week. Unsettled weather is likely Thursday afternoon into Friday night with this storm system. && .NEAR TERM /THROUGH THURSDAY/... As of 900 PM EDT Wednesday... Adjustments mad for latest radar trends... Last few runs of the RAP had a good handle on the location of storm development. Used this and current radar trends to add isolated to scattered thunderstorms from the New River Valley to the southern Shenandoah Valley through 03Z/11PM. Upper ridge centered across VA/NC will shift southward tonight as a trough digs across Ontario/Quebec into the Great Lakes. Overnight lows will also run warmer than normal by 5F or so, basically mid to upper 60s west of the Blue Ridge to lower 70s east. We start to loss the influence of the upper level ridge Thursday afternoon as it sinks further to the southeast. meanwhile, an upper level trough over Ontario/Quebec will slowly push a cold front across the Ohio Valley. This front will introduce a good chance for showers and thunderstorms to the western slopes (Bluefield to Lewisburg) by mid afternoon. For the rest of the mountains, scattered storms are possible in the afternoon and maybe an isolated shower east of the Blue Ridge. If storms move into the mountains during the afternoon, high temperatures will be cooler than the previous couple of days. With the expectation of storms arriving in the afternoon, highs across the mountains should range from the upper 70s to mid 80s. With less of a chance of rain east of the Blue Ridge, temperatures will once again be warmer than normal with highs in the low to mid 90s. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... As of 200 PM EDT Wednesday... Numerous showers and storms with a slow moving cold front Thursday night into Friday. Drying out for the start of the weekend... An active stretch of weather ahead over the next 24 to 48 hours as a slow moving cold front and upper level low pressure system roll our way. The main focus will be Thursday night into Friday when the bulk of our stormy weather looks to arrive. Locally heavy rainfall is likely along with localized flash flooding concerns. This is due largely in part to PWATS running anywhere between 1.5 to 2.0 inches across the area out ahead of the cold frontal boundary which will be further amplified by a deepening upper level low pressure system and it`s adjacent upper tough digging down from the eastern Great Lakes region. With all that said, the Weather Prediction Center has areas along and west of the Blue rIdge in a slight risk for excessive rainfall. Areas out east are also highlighted in marginal risk for excessive rainfall. This simply means that the airmass in play is very moist and muggy with a lot of water to dump out. This is further addressed in detail in the HYDROLOGY section below. As for rain amounts, we can look for a widespread swath of at least 1.5 inches to 2.5 inches across the area. Localized heavier pockets of 3 inches or better can be found across portions of the Greenbrier Valley back into the Mountain Empire and along the southern Blue Ridge. The good news is that we have been dry the last few days which should minimize the flood threat to a degree. WIth rainfall amounts of at least 1"/hr or better localized instances of flash flooding looks to be the biggest concern especially where we can get slow moving thunderstorms to line up. Our severe weather threat looks to minimized based on current 12z guidance shoving in the clouds and precipitation a bit faster heading into the front half of Thursday. The threat is not zero though especially across northern and eastern portions of our area where the better dynamics can be found. Forecast MLCAPE values per KIAD, KRNK, KDAN, and KRIC sit between 1,000-2,000 j/kg with DCAPE values upwards of 700 j/kg Thursday evening into the overnight. The threat will quickly decrease by Friday as the front continues south and east. Any widespread shower or thunderstorm activity should come to an end late Friday evening into Friday night as the front sags south and deepening upper level low swings north and east. On Saturday, the axis of the upper level trough will pivot through with it`s resultant cold pool aloft. This will keep isolated diurnal shower/storm chances in play on both Saturday and SUnday afternoon. Most of this will be confined to the mountains where better forcing can be found. Most locations look to remain dry with partly to mostly cloudy skies Saturday afternoon. Temperatures will be at or slightly below average through the period. Highs will top out in the low to mid 70s in the west with mid to upper 70s out east Friday under cloudy skies. More sunshine Saturday gets temperatures close to 80 degrees. Overnights lows will bottom out in the mid to upper 50s. Confidence remains moderate in the short term based upon the placement of the front and upper level low pressure system. Some uncertainty remains in regards to rainfall amounts and the flood threat based upon the dry conditions over the last several days. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 230 PM EDT Wednesday... Mainly dry with a warming trend expected July 4-7. After a cool start Sunday, temperatures will rebound with a return to seasonal heat and humidity. The upper level pattern is forecast to deamplify, the eastern long wave trough lifting northeast and away from the forecast area. In response, heights will increase, along with temperature and dewpoints. By mid-week enough moisture should return to support a few pop-up showers/thundershowers during the afternoon/evenings with highest pops over the mountains, but even then, expecting less than 30 percent coverage. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... As of 120 PM EDT Wednesday... Isolated to scattered thunderstorms with some MVFR to IFR visibility due to very heavy rain will continue until around 03Z/11PM. Used the last few runs of the RAP and radar trends for timing and placement of the showers and storms. May add to KLYH at least in the vicinity before midnight. MVFR to IFR fog is possible in the early morning where it rained this evening. Ceilings overnight will be VFR. Numerous showers and thunderstorms are expected on Thursday, especially after 18Z/2PM with MVFR ceilings and visibility. Above average confidence on ceiling, visibility and wind. Average confidence on the timing and location of thunderstorms this evening. Below average confidence of occurrence of fog overnight. Extended Aviation Discussion... Active weather is expected through Friday night as a cold front slowly works its way through the region from the northwest to southeast. Greatest confidence for sub VFR is Thursday night and Friday, associated with numerous showers and scattered thunderstorms. Improvement is expected Saturday and especially Sunday. An upper low is expected to cutoff over the Great Lakes and Ohio Valley this weekend which may cause unsettled weather to persist into the weekend, though should be VFR most of the time. && .HYDROLOGY... As of 100 AM EDT Wednesday... The region will have the potential for locally heavy, potentially flooding, rains for parts of the area Thursday afternoon into Friday Knight. Several atmospheric features are aligning in a way which favors such an outcome: 1) Forecast Precipitable Water is expected to be near 2.00 inches. Such values are between +1 to almost +2 sigma of normal for the start of July via NAEFS and place higher than the Daily Max moving average (1.66 inches) off the SPC Sounding Climatology Page for Blacksburg, VA. 2) Immediately preceding and coincident to the advancing cold front, 850mb-300mb Bulk Shear will be relatively weak and aligned nearly parallel to the front, thus allowing for training of showers/storms, 3) The majority of the precipitation is expected to fall across the region Thursday night through Friday evening with average amounts on the order of 1.25 to 2.25 inches with locally heavier amounts closer to 3.00 to 4.00 inches along some of the mountain ridges. The combination of steep terrain, and locally heavy, potentially training rainfall, can result in flooding issues. 4) The folks at the Weather Prediction Center are examining locally heavy rain concerns for our area as well. Within their Excessive Rainfall Forecasts for Thursday through Thursday night, they have placed Marginal Risk of flooding in areas generally east of the Blue Ridge, and a somewhat more concerning Slight Risk for areas generally along and west of the crest of the Blue Ridge. For Friday, A Marginal Risk is in place for counties along the VA/NC border and the piedmont of central VA. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RCS NEAR TERM...AMS/RCS SHORT TERM...ET LONG TERM...PM AVIATION...AMS/RCS HYDROLOGY...DS
Area Forecast Discussion
National Weather Service San Diego CA
155 PM PDT Wed Jun 30 2021 .SYNOPSIS... Isolated thunderstorms over the San Diego mountains today will dissipate this evening. Isolated convection is again possible Thursday. Coastal areas will be mired in June gloom through the weekend as a coastal eddy and a shallow marine layer limit clearing at the coast. The valleys, mountains and deserts will be warm this weekend with occasional mid and high clouds. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Towering cumulus formed over the mountains today, growing tall enough to generate a thunderstorm near Pine Valley and Mt Laguna between Noon and 1 PM. Farther north in Riverside and San Bernardino County the cumulus hadn`t grown tall enough for precipitation through 1 PM. Moisture convergence was highest in San Diego County where dew points were in the mid to upper 50s. Dewpoints were lower in Riverside County (40s and low 50s), and they were even lower in the San Bernardino Mountains (30s and 40s). This drier airmass will push a little farther southeast Thursday, limiting the T-storm potential primarily to San Diego County. Precipitable water over the San Diego County mountains today was 0.94", tomorrow it is forecast to be 0.90". The high resolution HRRR and WRF models show isolated convection tomorrow afternoon, but with less coverage than today. Dry lightning and strong wind gusts are the most likely threats. Friday through Sunday: A Four Corners high rebuilds over the Southwest bringing warmer days over the holiday weekend. Valley, mountain and desert temperatures will be a little warmer than average, but the coastal areas will be a little below average due to a persistent marine layer that will limit clearing at the coast each afternoon. Southeast monsoonal flow also increases over the weekend which will bring mid and high clouds. The westward extent of the deep moisture is still in question, but most of the long range guidance is dry. && .AVIATION... 302030Z...Coast/Valleys...The coastal terminals are likely to see BKN-OVC conditions through the afternoon. Low clouds spreading back inland after 01/00Z with bases near 700-1200 ft MSL and tops to 1700 ft MSL. Ceilings are expected to be a little lower on tonight and Thursday morning and stratus spreading further inland possibly as far as KONT. Skies will clear for all but the immediate coast 15-18Z Thursday. Thunderstorm activity is not expected to impact the coast/valleys. Mountains/Deserts...Isolated TSRA will continue through 00Z mainly over the mountains with CB bases at 10,000 FT MSL and tops to 30,000 FT MSL. The primary threat will be strong up/downdrafts and local surface gusts of 40 kt. The storms are expected to remain primarily over the mountains with only a low chance of moving eastward into the deserts. Will not mention thunder KPSP/KTRM due to low confidence of desert impacts. Isolated TSRA expected again Thursday afternoon, but less coverage than today. && .MARINE... No hazardous marine conditions are expected through Sunday. && .BEACHES... Expect a high rip current risk through the holiday weekend given the persistent long period south swell. Surf heights will peak Monday/ Tuesday in the 4 to 6 foot range. && .FIRE WEATHER... Isolated thunderstorms with dry lightning and gusty winds over the mountains through early evening, drifting east over the deserts. The moisture decreases Thursday and the greatest chances will be over the San Diego and Riverside County mountains. That drying trend will continue into Friday. Southeast monsoon flow returns over the weekend, but the moisture will once again be elevated. The forecast model are showing increasing mid and high level clouds, but the thunderstorm chances remain low. && .SKYWARN... Skywarn activation is not requested, but weather spotters are encouraged to report significant weather. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC/FIRE WEATHER...Moede AVIATION/MARINE...Moreland
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