Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/18/21

National Weather Service Albany NY
1008 PM EDT Tue Aug 17 2021 .SYNOPSIS... A warm and humid, tropical airmass will move into the region tonight with scattered showers and a few thunderstorms. Tomorrow, showers and thunderstorms will be most numerous north and west of the Capital Region. The remnants of Tropical Cyclone Fred will bring a more widespread, and possibly heavy rainfall Wednesday night through Thursday with humid conditions persisting. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... .Update... Heaviest, most persistent rain has been staying west of Albany Forecast Area. Parts of Central New York saw 3-5 inches of rain this evening. Scattered showers now occurring over most of our New York zones, but mainly dry over western new England zones. Winds are light an variable. Temperatures are in the mid 60s in the terrain to the mid 70s in the mid Hudson Valley. Latest run of the HRRR has periods of showers over the Adirondacks continuing overnight with showers over the rest of the area diminishing. .Previous... PWATs are on the rise on the transitional air mass with the latest SPC RAP Mesoanalysis showing 1.6-1.9". The 12Z KALY sounding was 1.91". Forecast area will get into better tropical environment into tonight. The 1.91" PWAT is in the 90-100% of climo for this time of year. Intense rainfall rates will be possible with any convection. Weak elevated instability is noted so an isolated thunderstorms or two is possible. The heaviest rainfall will be north and northwest of the Capital Region. A lull is likely to continue to the south and east. FFG values remain high due to the recent dry spell since Aug 1st, so any hydro issues look minimal through the afternoon. Some ponding of water and poor drainage flooding is possible. An isolated FFG may be possible near the western Mohawk Valley if intense rainfall rates are realized due to high PWATs. Low-level theta-e advection continues overnight with some scattered showers possible or maybe an isolated thunderstorm. Synoptic forcing becomes nebulous the with warm front drifting through. Better chances of showers continue from ALY north and west. A sticky night is expected with dewpts in the 60s to spotty lower 70s. Lows will be in the 60s to around 70F. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Tomorrow...The guidance continues to vary on the track of the remnant circulation of TC Fred. The circulation lifts northeast of the TN Valley into the OH Valley and wrn PA. In the confluent zone northeast of Fred, enhanced low-level convergence will allow for periods of moderate to heavy showers to occur west of most of the forecast area but then to slide eastward during the day. In the tropical environment, PWATs will be in the 1.7-2.0+ range range. Low stratus will likely linger over the region into the late morning into the afternoon. A conditional thunderstorm threat is possible if any heating occurs during the day. Low-level shears increases with low to moderate instability. An isolated tornado may be possible or damaging wind gusts as a Marginal Risk is in place southwest of Albany along the eastern Catskills, Schoharie and western Mohawk Valley. Some locally heavy rain is possible, but the guidance (majority has shifted north and west) with the low and mid level ridging building in off the coast. Highs will only get into the 70s to spotty lower 80s in the valleys. Some 60s will linger over the higher terrain. Wed night to Thu...A subtle shift in the rainfall with TC Fred with the EC/NAM trending north and west to the GFS and some of the CAMs. The NAM is the furthest west slamming the Adirondacks and western Mohawk Valley northward with the heaviest rainfall. The EC and GFS hit the northern Catskills/Capital Region/northern Berkshires north and west with 1-3" of rainfall. We had an extensive collaboration call with WPC with neighboring WFOs to shift the QPF north some and move the SLIGHT Risk for excessive rainfall north of the mid Hudson Valley in Day 2. The Marginal Risk was expanded in Day 3. See the hydro discussion with more details. PWATS are +2 to +3 STDEVs above normal so intense rainfall rates with local orographic enhancement are possible. The timing and placement of the rainfall is uncertain but locations north and west of the Capital Region may get the higher QPF at this time. 1-3" with locally higher amounts are possible. Low to modest amounts of instability will exist some isolated to scattered thunderstorms are possible in the tropical air mass. Lows WED night will be in the 60s. THU highs will be in the 70s with some 60s over the mtns. It will likely be a gray day with temps below normal. Thursday night...showers diminish with the remnant circulation of Fred moving downstream of New England. Have kept a chance of showers in prior to midnight with a slight chance of thunderstorms. Lowered PoPs after 06Z with some weak ridging building in the wave of the trough. Some patchy fog may also occur with lows in the 60s still in most locations. && .LONG TERM /FRIDAY THROUGH TUESDAY/... The long-term forecast period will continue to feature warm and humid weather conditions with day-to-day chances for showers and thunderstorms as eastern New York and western New England sits in the warm sector of a storm system well off to our northwest with an associated frontal boundary to our north, a cold surface frontal boundary to our west, and upper level ridging/higher geo-potential heights overhead. As far as precipitation chances, there`s been better continuity amongst forecast guidance overall over the past few days, but still some uncertainty in the spread. In general, the deterministic solutions are showing more spread than the ensembles. Given the abundance of moisture that`s forecast to be over the area with PWAT values still ranging 1-2 STDEVs above normal, weakness in the mid- levels with a weak mid level low and associated impulses, and an unstable environment, afternoon/evening scattered showers and thunderstorms will be possible each day of this long-term period. Have 30-40% PoPs each day of the extended during the afternoon and evening hours. Given that 0-6km bulk shear values are low and there`s weak flow aloft, not expecting any thunderstorms to become organized. That said, thunderstorms (diurnally-driven) will be of the garden/pulse variety. Rainfall could become moderate to heavy under any convection given the high moisture environment with PWATS 1-2 STDEVs above normal and dewpoint values in the upper 60s to lower 70s. There`s still uncertainty in the timing of the cold fropa. Right now, it appears to be in the Tuesday evening into Wednesday timeframe given how slow the system is moving. Once the cold front passes the region, it will being a cooler and drier airmass into the region mid to late next week. As far as temperatures, high temperatures are forecast to be in the lower to mid 80s along the river valleys with 70s over the higher terrain. Nighttime will remain warm and humid with overnight lows holding in the mid to upper 60s (upper 50s and lower 60s higher elevations). && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... Light rain or rain showers should overspread all the TAF sites this evening. Ceilings will gradually lower overnight to MVFR. IFR ceilings are also possible By 09-12UTC with some restrictions to visibility in fog down to 1-2 miles with very moist airmass in place. Any fog should lift tomorrow by 13-15UTC. MVFR ceilings look to linger through at least 15 UTC tomorrow at most TAF sites and could struggle to improve to VFR even by 18 UTC. Some isolated showers or thunderstorms are possible after 18UTC tomorrow, but coverage looks limited and locations too uncertain to include in TAFs at this time. Southeasterly winds turn light and variable tonight before shifting to the south - southwest by 12 UTC becoming sustained at 5 - 10 kts during the day. Outlook... Wednesday Night: High Operational Impact. Definite SHRA...TSRA. Thursday: High Operational Impact. Likely SHRA...TSRA. Thursday Night: Moderate Operational Impact. Chance of SHRA...TSRA. Friday: Moderate Operational Impact. Chance of SHRA...TSRA. Friday Night: Low Operational Impact. Slight Chance of SHRA. Saturday: Moderate Operational Impact. Chance of SHRA...TSRA. Saturday Night: Low Operational Impact. Slight Chance of SHRA. Sunday: Moderate Operational Impact. Chance of SHRA...TSRA. && .FIRE WEATHER... A warm and humid, tropical airmass will move into the region tonight with scattered showers and a few thunderstorms. The showers and a few thunderstorms will be most numerous north and west of the Capital Region tomorrow. The remnants of Tropical Cyclone Fred will bring a more widespread rainfall Wednesday night through Thursday with some thunderstorms and humid conditions persisting. A moist, tropical air mass will be over the area through Thursday with periods of rain and elevated RH values. Winds will be south to southwest for much of the period. && .HYDROLOGY... Localized hydro issues may arise Wednesday night through Thursday across the ALY HSA. A warm front will move through the region early tonight. Some late afternoon and evening, slow- moving showers and thunderstorms may move back into this area north and west of the Capital Region. This may result in an isolated flash flooding threat mainly over the Mohawk Valley into the southern Adirondacks. A slight risk of excessive rainfall is in place in this area per WPC guidance. The remnants of TC Fred will approach late Wednesday night into Thursday. An area of heavy rainfall will likely accompany the remnant circulation. There is uncertainty as to the timing and area of heavy rainfall, but the risk is maximized has shifted northward and is from the northern Catskills, Capital Region north and west, where a slight risk of excessive rainfall exists per WPC collab this pm. Rainfall amounts will be in the 1 to 3 inch range. Fairly dry antecedent conditions should mitigate the flood threat somewhat, but areas of urban/poor drainage flooding and a few flash floods cannot be ruled out especially north and west of Albany. MMEFS and NERFC guidance shows no main stem river flooding at this time. However, the trends will continue to be monitored. A Flash Flood Watch may be needed later in time especially for some areas. Chances of rain persists Friday into the weekend, but will be more localized. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Wasula NEAR TERM...SND/Wasula SHORT TERM...Wasula LONG TERM...Evbuoma AVIATION...SND FIRE WEATHER...Wasula HYDROLOGY...Thompson/Wasula
Area Forecast Discussion
National Weather Service Gaylord MI
1123 PM EDT Tue Aug 17 2021 .UPDATE... Issued at 959 PM EDT Tue Aug 17 2021 Main concern is the patchy fog, and how much it will obscure locations. At this point the fog will probably lower the visibility to about a mile. There could be some location that could see lower visibility, but generally things should be decent. So, not much to change on the forecast for the night. && .NEAR TERM...(Through Tonight) Issued at 325 PM EDT Tue Aug 17 2021 High Impact Weather Potential...Minimal Pattern Synopsis/Forecast...18z surface analysis shows high pressure centered off the New England coast ridging back west into the Great Lakes. A cold front sits off to our northwest from far northwest Ontario into North Dakota. Remnants of Tropical Depression "Fred" are lifting northeast across north Georgia. Water vapor imagery shows a nice little spiral north of Georgian Bay spinning away from Michigan...part of a positively tilted PV anomaly that stretches back southwest across Iowa and into Kansas. Departing circulation over northeast Ontario has been throwing bits of mid/high cloud back into eastern Upper throughout the day along with some diurnal Cu across Chippewa county...and a couple areas of Cu across far northwest Lower as well as south of a CAD- APN line...both areas where surface dew points have managed to hang on around 60+F. No real changes in the pattern tonight as surface ridging/ anticylonic flow holds...with a PV "filament" lingering over northern Lower as part of the overall elongated short wave trough axis. Primary Forecast Concerns...Pretty minimal concerns and mostly reflect the concerns from the past several nights revolving around fog possibilities. As winds remain on the light side and clouds remain clear/thin will probably see some fog develop especially in interior low lying areas especially around lakes and rivers which is typical for cool nights this time of year. Overnight lows should be mostly in the 50s...but some interior cold spots could dip into the 40s. && .SHORT TERM...(Wednesday through Friday) Issued at 325 PM EDT Tue Aug 17 2021 High Impact Weather Potential: Minimal... Pattern Synopsis/Forecast: Last 48 hours have seen large scale, upper-level pattern across the CONUS go from more or less zonal to more positively tilted... with additional shortwave energy digging into the broad troughing in the Pacific northwest. Bermuda high is retrograding westward into the southeastern US as Fred meanders northward on the inland side of the Appalachians...with that same weak troughing/PV anomaly action across the inner half of the country/Great Lakes region as has been noted the last few days (best noted on water vapor satellite imagery today by a long swath of dry air ahead of some cloud activity extending from a little niblet to our northeast this morning...back into the southern central Plains). Will look for this overall pattern to continue...with Fred attempting to make its way northward...but ultimately unable to do much to our weather here in Northern Michigan beyond some increased cloud cover and perhaps (perhaps....) some small rain/storm chances by Wednesday afternoon. Loosely split flow across the center of the country seems to favor the Great Lakes for subsidence and high pressure, on the north side of that PV anomaly, however. As upstream troughing digs eastward through the middle/end of the week...will look for it to build ridging in the northern stream...only further reinforcing the split flow idea. Depending on the exact position of the pattern...this could mean we remain overall dry and quiet even into the end of the short term...though some uncertainty yet remains. Primary Forecast Concerns: Rain chances...or a lack thereof...and possible smoke effects... Welllll....17/12z HRRR vertically integrated smoke guidance continues to keep the bulk of the smoke to our west/northwest, caught up in the more active part of the flow as stronger shortwaves pass well north of us. Weakly split flow here in the Great Lakes looks like it will continue to keep the majority of the smoke from moving in, at least through 12z on the 19th (Thursday morning). Looking at today`s visible satellite imagery...can see diurnal cu popping across central WI/E central UP ahead of the smoke...with cloud development under the smoke limited to activity driven by a cold front/dryline crossing the northern Plains. Given that smoke guidance suggests some higher concentrations filtering into the UP Wednesday and Wednesday night (looks to have a tough time making it into Northern Michigan, at least initially)...and given upstream trends and prior experience with smoke this summer... first loose guess is that highs across the UP Wednesday (and perhaps again Thursday) will not reach their full potential as the smoke blocks out some of the better heating, despite minimized cloud cover there. Did lower max temps for Wednesday across the E. UP, though we`ll see if it was enough or not. Otherwise, it should be warmer with more diurnal Cu across most of Northern Lower. Will have to wait and see how things turn out for Thursday and beyond regarding smoke...but I suspect the plume may primarily miss Northern Lower, encroaching at times here and there...adding extra wrenches into the forecast for the upcoming week. By Wednesday, there are some signals for increased moisture into especially southeastern Michigan...perhaps getting as far north as our southern/southeastern CWA? Whether this is totally from remnants of Fred...or related to some of that PV action to our southwest lifting into the not entirely clear. Either way...there is perhaps somewhat of a better chance of showers and maybe a rumble of thunder Wednesday afternoon than the last couple days, given a little more potential for instability as we become a little warmer and more more moist in the boundary layer than we`ve been the last few days...and some slight steepening of lapse rates is possible aloft as the PV anomaly to our southwest tracks up into the area, bringing some slightly cooler 500mb temps in with perhaps little change to the lower level temperatures. Even so...guidance still seems to want to keep things drier and push better precipitation chances out farther into the end of the week. Model derived soundings suggest the cooling aloft Wednesday may lead to mainly elevated instability over a weak but somewhat deep cap in the mid- levels, so it could go either way, depending on how warm we get in the afternoon. Additionally...soundings suggest a pretty deep layer of dry air aloft...which could further mitigate precipitation chances. With this somewhat more warm and moist atmosphere in place...Thursday and perhaps even Friday may end up seeing some isolated shower/storm development. Ridging looks to strengthen to our west ahead of the approaching upstream trough Thursday into Friday...while the same PV anomaly mischief seems to linger across the Great Lakes into end of the period. Depending on exactly where these features end up, either one could ultimately serve to instigate some precipitation, whether due to the weak perturbations aloft or lake breeze development...though there is still a lot of uncertainty surrounding precipitation chances through the remainder of the period. Bottom line: stereotypical summer weather ahead -- warm, increasingly humid, and isolated showers and storms possible at times, probably especially in the afternoons and especially inland along the lake breeze(s), though many locations should stay dry. .LONG TERM...(Friday night through Tuesday) Issued at 325 PM EDT Tue Aug 17 2021 High Impact Weather Potential: Minimal attm... At this point in time...looks like the best chance for showers/ storms (which may or may not also be dwindling...?) should be Saturday (ish) as that upstream trough swings through. Current model runs look less impressive with this for us compared to yesterday at this things appear to be less certain yet again...though they do seem to be getting on board with the overall pattern a little better now. Would guess this uncertainty, and continuing uncertainty into the remainder of the period, relates at least in part to the Atlantic basin tropical systems -- Grace and Henri -- both of which will be affected by that retrograding ridge across the southern US. Even so...will still have to keep an eye on the weekend as it could be somewhat active as far as storms go...especially considering that this is still peak outdoorsy- camping season across our beautiful Northern Michigan CWA. Either way, it`s always good to remember to include the weather in your vacation plans. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1113 PM EDT Tue Aug 17 2021 The main issue is still the fog potential for the TAF sites. TVC should remain fog free overnight with the very light south flow. The rest of the sites (MBL, PLN, APN) all will probably see some type of restriction, with MBL expected to fall to around 4sm prevailing, and tempo restrictions to 3/4sm or maybe 1/2sm FG. After 12 or 13z, the fog should lift and diurnal Cu will form over the region, so CIGs should maintain VFR if they form at all. && .MARINE... Issued at 325 PM EDT Tue Aug 17 2021 High pressure ridging in from the west should keep winds on the lighter side and allow for lake breezes to dominate things Wednesday and Thursday. Increasing signals for some fog and haze to develop over the next several days...lake waters are warm so will take some decently high dew points for that to occur. Fog on the St. Mary`s River is possible tonight with some cool air drainage. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LH...NONE. LM...NONE. LS...NONE. && $$ UPDATE...JL NEAR TERM...JPB SHORT TERM...FEF LONG TERM...FEF AVIATION...JL MARINE...JPB
Area Forecast Discussion
National Weather Service Bismarck ND
942 PM CDT Tue Aug 17 2021 .UPDATE... Issued at 940 PM CDT Tue Aug 17 2021 Fire weather danger conditions are starting to improve across the CWA late this evening, although lingering hot temperatures are making for some low RH in the southwest. Light southeast breezes continue for some areas in the south, with a northeast flow across the north. Overall improving fire weather conditions are expected through the night, thus have let the Red Flag Warning expire. Made some minor adjustments to PoPs based on current radar trends. Surface low in MT will strengthen the low level jet tonight. Where this jet meets the low a few showers and thunderstorms are possible. Atmosphere is fairly capped, and these storms should be mostly elevated. Thus severe weather is not expected at this time. HRRR Smoke Forecast also showing easterly flow should improve smoke tonight, so have reduced mention of this later tonight. Surface front will then slowly make its way across the region tomorrow. Initial passage looks to be fairly dry, and have lowered daytime PoPs. Wednesday night could see some increased moisture along and behind the front, perhaps returning isolated to scattered showers and thunderstorms. Look for another generally warm day as well on Wednesday, with upper 90s expected across central portions. UPDATE Issued at 658 PM CDT Tue Aug 17 2021 Minimal updates needed early this evening. A few weak returns are currently showing up on radar across the west and across the James River Valley. Although a few showers may come out of these returns, especially in the west, dry air at the surface will limit chances for showers and thunderstorms this evening. Made some adjustments to PoPs based on latest trends. Winds have increased slightly early this evening, bringing warm temperatures and low RH values to much of the state. Will let the Red Flag Warning continue until at least 8 PM CDT for the time being as a result. && .SHORT TERM...(This evening through Wednesday) Issued at 142 PM CDT Tue Aug 17 2021 Cloud cover, along with smoke, have inhibited temperatures so far today for central North Dakota. It seems unlikely many of these locations will reach originally forecast highs, thus have lowered highs a bit along the eastern half of the forecast area. Winds are not quite picking up as expected in the southwestern part of the state either as the surface low center has already nudged into the state. Weaker winds along with the aforementioned reduced temperatures for the eastern counties may prevent much of the area from fully reaching Red Flag criteria. Still, with how dry the area has been, it wouldn`t take much for any fires that may develop to spread rapidly, thus will allow the Red Flag Warning to remain in place. Could see a few showers this afternoon into tonight for the western and northern forecast area. Overall though, with so much dry air present, expect coverage to remain isolated and rain amounts to be low. Besides precipitation chances, HRRR Smoke indicates an improvement in near-surface smoke this evening and overnight, although more elevated smoke will likely remain in place for Wednesday. .LONG TERM...(Wednesday night through Tuesday) Issued at 142 PM CDT Tue Aug 17 2021 The extended period begins with a west CONUS trough and east CONUS ridge in place. Through Friday night, the west CONUS trough will gradually lift northeastward through the region producing some of the better shower and thunderstorm chances in a while. While precipitation will be possible throughout the majority of the period, presently the best chances of seeing more widespread moderate precipitation are Thursday night through Friday. For the most part, instability looks to be limited, so rain showers are likely to be more prevalent than thunderstorms, although rumbles are thunder are certainly expected at times. Even a severe thunderstorm or two Thursday evening is not completely out of the question further southeast towards the southern James River Valley. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 658 PM CDT Tue Aug 17 2021 Overall look for VFR conditions through the forecast period. Through tonight, a few isolated showers and thunderstorms are possible across the west and north. Confidence is low that this will impact any TAF sites, and ceilings should generally remain at VFR levels. A breezy south southeast wind may also be found at times through tonight, with some low level wind shear possible for a few TAF sites. Wednesday then looks to see mainly dry and VFR conditions. A breezy south wind looks to be found for more sites, although a switch to a northerly wind may be found from KXWA to KDIK and KXWA to KMOT on Wednesday afternoon. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Anglin SHORT TERM...Telken LONG TERM...Telken AVIATION...Anglin
Area Forecast Discussion
National Weather Service Des Moines IA
633 PM CDT Tue Aug 17 2021 .DISCUSSION.../Tonight through Tuesday/ Issued at 359 PM CDT Tue Aug 17 2021 Forecast Highlights: -- Warm, humid through Thursday. -- Smoke aloft Wednesday in Northwest and Northern IA. -- Thunderstorm chances return later in the week, severe storms possible Friday. TODAY THROUGH WEDNESDAY: A few clouds in central to eastern Iowa along with the return of wildfire smoke to northwest Iowa can be seen on GOES-16 Satellite this afternoon. With a weak mid-level ridge in place and the remnants of the upper-level trough pushing off to the east through the day today, mainly quiet weather continues. Moisture return this afternoon aided by southerly low level flow has caused dew points to surge into the 70s in western Iowa with mid to upper 60s dew points elsewhere as of 2pm. The return of the humidity has pushed heat indices back into the 90s in western Iowa as of 2pm. High temperatures this afternoon are expected to climb into the mid to upper 80s with heat indices topping out in the upper 80s to low 90s across the area. With a thermal ridge continuing to build off to the west and moving eastward into tomorrow and Thursday, a stronger push of theta-e advection will raise temperatures a few degrees on Wednesday with high temperatures near 90 and heat indices topping out in the low to mid 90s on Wednesday afternoon. Breezy southerly winds are expected on Wednesday afternoon as the pressure gradient tightens with 10 to 20 knot wind gusts becoming common. Some scattered convection could still be possible on Wednesday afternoon, mainly associated with peak heating and in southern Iowa, but any storm chances look to be isolated at best. The formation of diurnal cumulus is likely with with the warm and humid airmass in place and an unstable boundary layer, but forecast soundings in southern Iowa remain mostly dry at the surface and mid levels so any updrafts that do form will be difficult to maintain. With all these caveats and scattered/isolated nature of any possible convection, kept forecast dry for Wednesday. The return of smoke from western wildfires today in northwest Iowa will continue into Wednesday with the higher concentrations aloft moving somewhat east overnight into tomorrow impacting northwest into northern Iowa through the day on Wednesday and with smoke aloft making its way towards central Iowa overnight into Thursday, as of the latest HRRR model output. Added additional sky cover to account for smoke aloft Thursday in the sky grids, but no visibility impacts expected as of current model trends. THURSDAY AND BEYOND: The mid-level trough that will bring our next system pushes east from the the Inter-Mountain West Thursday into Friday. An associated surface cold front will be move through the area on Friday into Saturday with precipitation chances ramping up late Thursday into Friday morning ahead of the aforementioned cold front. Although scattered showers and a few storms are possible throughout the day Friday, the best chances for storms looks to be Friday afternoon into early Saturday morning. Some strong to severe storms are possible with most models suggesting the trough will take on a negative tilt allowing for the surface cyclone to deepen as it approaches the area. A ribbon of high instability will be ahead of the cold front though deep layer shear may be a lacking ingredient. 0-6km shear away from the boundary is 20-25 knots but higher shear values could be along, but more likely behind the boundary. The SPC has introduced a 15% probability of severe storms over much of the northwest half of the state, so we will continue to monitor these trends over the coming days to further evaluate the severe weather potential. In terms of temperatures, Thursday will be similar to Wednesday with the warm and humid conditions continuing. High temperatures will once again be near 90 with heat indices climbing a degree or two warmer across the area, but again in the low to mid 90s. The precipitation/storms and cloud cover on Friday will provide some temperature relief dropping temperatures back into the 80s and the cold front passage helping to drop temperatures a bit more on Saturday with locations in northwest Iowa dropping back into the upper 70s with low to mid 80s elsewhere. There are additional chances for precipitation late Sunday into early next week, but details will continue to be ironed out in the coming days. && .AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/ Issued at 632 PM CDT Tue Aug 17 2021 Widespread VFR conditions for much of the forecast period. Only concern would be some low lying fog early morning Wednesday, but this will be mostly patchy. Surface winds to remain from the south to southeast for the period. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KCM AVIATION...Cogil
National Weather Service Sioux Falls SD
1049 PM CDT Tue Aug 17 2021 .SHORT TERM...(This Evening through Wednesday) Issued at 342 PM CDT Tue Aug 17 2021 A breezy afternoon across the area with low pressure over the Rockies and high pressure over the Mississippi Valley resulting in a decent SPG through the region. Even with temperatures in the mid 80s to mid 90s, along with the gusty winds, relative humidity values have remained in check so there have been no fire weather issues. Winds will fall off overnight, though not light by any means, and with the southerly low level flow it will be a mild night with lows in the mid 60s to around 70. Not much change in the weather for Wednesday. With the aforementioned surface pressure gradient and soundings indicating momentum transfer winds of around 15 to 20 kts, it will be another breezy day. Latest HRRR smoke model continues to indicate smoke aloft for tomorrow, which could impact temperatures slightly, though with model 850 mb temperatures of 19 to 25C consecutively from east to west across the area, we will again see highs in the upper 80s to mid 90s. .LONG TERM...(Wednesday Night through Tuesday) Issued at 342 PM CDT Tue Aug 17 2021 Another nearly carbon copy day on Thursday will little change in the overall pattern. It will be breezy with highs in the upper 80s to lower 90s. As for Thursday night and Friday, an upper level trough situated over the western CONUS begins to shift eastward, landing in the Northern/Central Plains by Friday evening. The GFS continues to be the most progressive and generally stronger with the system than the NAM/ECMWF/GEM, though still a bit slower than previous model runs. The GFS still brings a leading cold front/surface trough into our far western CWA by 03Z Friday, while other deterministic models have it farther to the west. Because of this, GFS develops precipitation quicker on Thursday evening - and the resultant NBM pop grids look to bring higher pops in too quickly on Thursday night. Models do indicate a low level jet developing through central SD in the late evening, and this could aid in thunderstorm development. While there will be instability in place, effective bulk shear does not look that impressive over our area during that time period, so think the severe threat would be on the low end but enough that an SPC marginal risk is appropriate in our west for that night. The main surface trough/cold front begins to push eastward across the area by late Friday afternoon or evening - though again there are model differences in the timing of this feature, with the GFS continuing to be the fastest. While thunderstorm activity will be likely sometime during the day on Friday, it is still difficult to say how much of a severe potential there is because of the differences in frontal timing and strength of upper level forcing. In any event, cannot completely rule out some severe storms on Friday afternoon as supported by a 15% prob of severe weather per SPC on Day 4. By Saturday models show the upper level wave tracking off into the northern Great Lakes region so we should dry out for that day. With cold air advection behind the system it will cool down to below normal levels with highs mainly in the 70s. Another shortwave is progged to slide into the Northern Plains sometime in the Sunday to Monday time frame, but models are differing in handling this feature, so confidence is low in precipitation chances. Overall, it appears that near normal temperatures will be the rule for the beginning of the week. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1048 PM CDT Tue Aug 17 2021 For the most part, will be a repeat of conditions from last night and earlier today, for tonight and tomorrow. Surface winds will remain sporadically gusty for KFSD/KHON areas overnight. Very small chance that could see a few shards of cloud between 1000-2500 ft AGL into KSUX/KFSD 11z-14z as increased moisture feeds in beneath the inversion aloft. Slight stronger winds with gusts around 25 kts will develop again by 17z Wed. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...JM LONG TERM...JM AVIATION...Chapman
National Weather Service Hastings NE
618 PM CDT Tue Aug 17 2021 .DISCUSSION...(This evening through Tuesday) Issued at 345 PM CDT Tue Aug 17 2021 Summary... Warm and dry conditions through Thursday afternoon, then chance for shwrs/storms with next cold front Thursday night into Friday. Brief cool down expected behind the cold front, before hot temperatures return for second half of the weekend and into early next week. Analysis... Somewhat "busy" upper level pattern noted on aftn WV imagery consisting of the remnants of Fred over Southeast/Mid-Atlantic, remnant weak troughing from S Plains into Lower MO Valley, shortwave ridging from Four Corners NE into central High Plains, and finally, a strong upper trough digging SE through the Pac NW. We have some fair wx CU over SE half of CWA, but not expecting this to bubble up to any shwr/tstm activity owing to broad subsidence/mid level dry air noted on WV. Can see a slight haze to the sky this aftn, and true color sat imagery confirms a nearly stationary swath of smoke stretching from SE Colorado, across central Nebraska, northeastward into Upper MS Valley. Sfc vsbys are nearly perfect in the region, however, which suggests this smoke layer is elevated in nature. Have maintained a haze-free forecast as HRRR shows main impacts W/NW of the area. Forecast details... It looks to be mainly a persistence forecast for the next 36-48 hours, with little in the way of upper forcing to support organized pcpn, or even much cloud cover for that matter. NAM has backed off on it`s temps for Wed, so now nearly all guidance, sans the GFS, is in good agreement in temps being similar or only slightly warmer than yesterday/today for Wed/Thu. Looks like a decent pressure gradient (by late summer standards) will continue to provide breezy conditions thru Thu, so overnight lows will be mild in the upper 60s to near 70F. Our weather should eventually turn more active later on Thu as the western trough gradually shifts E and pushes a cold front onto the Plains. Still have some uncertainty on exact timing on certain features, with GFS still faster than other model solutions, but I think the general evolution of Thu eve to Fri night time frame is becoming more clear. Models are in good agreement that the primary zone of initial tstm development late Thu aftn will be W/SW of the area over the higher terrain of CO/WY, in an area of upslope flow, along and ahead of the cold front. Some models (namely some NAMNest runs) develop activity further E in two zones: across NW/W KS along apparent dry line feature and/or across N KS in zone of enhanced WAA. Have a feeling these solutions are overdone given modest capping amidst weak ascent/lapse rates, and fairly dry mid to upper levels. Can`t completely rule these solutions out, but think our primary tstm chcs will come during the overnight as tstms attempt to roll eastward off the High Plains, possibly supported by incr low level jet. However, it`s uncertain how successfully this activity will be at holding together owing to decr shear and incr CINH with time and eastward extent. Also, models are a bit unclear as to where best low level convergence will be on nose of veering LLJ. Agree with SPC that if storms can organize, W portions of CWA would have a non-zero chc for severe (mainly dmg wind) during the late eve and early overnight, with activity probably weakening further E. Some NAM/EC runs point towards W/NW/N portions of CWA standing best chance for a potential MCS Thu night. Evolution on Fri will likely depend on how activity unfolds Thu night. Could easily envision a scenario where Thu night convection is just strong enough to sweep the outflow/effective cold front thru most of the CWA Thu night/Fri AM, such that the best aftn instability and chc for redevelopment would be over far E portions of CWA, or even just to the E. On the other hand, NAM and EC maintain a slower trough progression that would give at least central and eastern portions of CWA a chance to destabilize by mid to late aftn and support new tstm development along the advancing cold front. IF this were to happen, would think svr chcs (both hail and wind) would be higher than Thu eve due to stronger shear, better timing with peak instability, and better upper level support. Have seen these scenarios play out both ways, so will just need to watch trends, esp. regarding tstm organization Thu night and overall system timing. Still expect cooler conditions behind the front, esp. for Sat, with highs mainly in the 80s. This cooldown looks to be short- lived, though, as both EPS and GEFS bring upper 80s and 90s back to the forecast area for Sun, and perhaps more widespread 90s for early next week as heights build. Another shortwave is forecast to track from central Rockies into northern Plains late Sun into Mon that may try to drag a cold front into Neb., but rising heights suggest this front will stall or washout somewhere in the area early next week. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday) Issued at 617 PM CDT Tue Aug 17 2021 Skies are expected to be clear through the period. Winds from the south will continue through the night and into the daytime on Wednesday. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Thies AVIATION...JCB
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
934 PM EDT Tue Aug 17 2021 .SYNOPSIS... High pressure over the Gulf of Maine will continue to slide southeast tonight. Humidity and chances for showers and some thunderstorms increase Wednesday with showery and humid weather expected through the end of the week as the remnants of Tropical Depression Fred advance northward. Temperatures will generally run in the upper 70s to low 80s each day. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Update...Minor changes to reflect latest observational trends. There is a small break in more widespread shower coverage for the time being...which will give way to more showers moving out of NY in several hours. Previous discussion...Showers that have been located over western New England and Upstate New York today will spread north and east during the overnight hours. The latest HRRR suggests that the best chance for showers will be over New Hampshire and the western mountains of Maine. PWs rapidly increase tonight across the region topping out at 2 inches by morning in some areas. The increasing surface dew points and deep layered moisture may allow for a couple of the showers to be heavy, mainly along and near the Connecticut River Valley. The cloud cover and increasing moisture will make for relatively uniform temperatures during the overnight hours. Lows will mainly be in the lower to mid 60s. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... A few showers will form on Wednesday ahead of the approaching remnants of tropical cyclone Fred. CAPE values will be on the increase as the atmosphere destabilizes during the day. This will allow for scattered thunderstorms as well, some of which could contain locally heavy rains. High temperatures will climb to the mid 70s to lower 80s across the region with the warmest temperatures across southern New Hampshire and interior southwest Maine. It will feel rather muggy however as surface dew point values climb to around 70. The 12Z model suite suggests the remnants of TC Fred will begin to cross the region late Wednesday night. There is considerable uncertainty as to how much rain will fall and the location for this precipitation. However this will need to be monitored for the potential of locally heavy rains. Plentiful low level moisture will allow for patchy fog to develop overnight. It will be a mild night with lows mainly in the mid to upper 60s. A few locations across southern New Hampshire may not fall below 70 degrees. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Overview: The forecast will begin with a large western Atlantic ridge in place as Tropical Storm Henri loops around Bermuda. Deep southwest flow will allow for increased humidity as tropical moisture begins to move northeastward from the Gulf. The remnants of what is now Tropical Depression Fred will bring an increased chance for rainfall to the area late Wednesday night through Thursday Impacts: The potential exists for locally heavy rainfall on Thursday as the remnants of Tropical Depression Fred interacts with a shortwave trough to our north. There remains differences in model guidance for the placement and magnitude of the heaviest rain axis but currently southern NH is favored. In addition, dewpoints will once again climb to near 70F with overnight lows only into the 60s, which although they will not be accompanied by temperatures into the 90s it will still feel rather unpleasant. Forecast Details: While there remains some differences between the GEFS and global model spaghetti plots, there is now moderate to high confidence that the remains of what is now Tropical Depression Fred will move northeastward through the Ohio River Valley before moving east across New England by early Friday. This will occur as an upper level shortwave passes to our north, which will supply Fred with some additional energy and thus increase our rain chances. Deep tropical moisture will be advected northward under deep southwest flow, which will allow PWATS to approach 2.00", especially across southern portions of the forecast area. Using the SPC sounding climatology, these would be about 200% of normal. In terms of QPF, there remains differences between individual forecast models as well as between their operational and ensemble means. Today`s forecast runs have trended further northward with the heaviest rainfall axis but this could once again shift south in future runs and therefore confidence remains low. The control runs are generally higher than the ensemble means with the ECMWF ensembles the most bullish on rainfall amounts of between 1.00-2.00", especially across southern NH. The ECMWF is also notably slower than the GFS and CMC with having the low not pass through the area until later on Friday. Should these heavier rainfall amounts be realized in a few hour time period, then some flash flooding would be possible, especially across urban and hilly areas. The latest day 2 and day 3 excessive rainfall outlooks released by the Weather Prediction Center places extreme southwest NH as well as York County ME into the Marginal risk category. Rain will end from north to south on Friday with skies gradually clearing, especially towards the international border. Saturday and Sunday will be a warm and muggy with high temperatures into the upper 70s to lower 80s as dewpoints remain near 70F. Skies will be partly cloudy each day and given the humid airmass that will be in place a few mostly diurnally driven showers and thunderstorms will be possible during the afternoon and early evening hours. Upper level ridging will try to build into the eastern CONUS through the middle of next week but a few shortwaves will likely ride under the northern periphery and provide at least some chances for scattered showers and thunderstorms each afternoon. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... Short Term... Scattered SHRA and lowering cigs may bring periods of MVFR tonight before a return to mostly VFR Wednesday outside of SHRA and a few TSRA. Patchy fog late Wednesday night will lead to localized IFR conditions. Long Term...VFR conditions expected outside of any SHRA/TSRA. While more widespread showers and isolated thunderstorms are expected on Thursday, the remainder of the forecast period will mostly feature diurnal showers/thunderstorms across interior locations. && .MARINE... Short Term... Patchy fog may form over the eastern waters tonight. Otherwise, winds and seas remain below SCA threshold through Wednesday night as high pressure over the waters slides to the southeast through midweek. Long Term...Winds and seas are expected to remain below SCA criteria through Saturday. Some marine fog/stratus will be possible as moist warm air moves over the relatively colder waters. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Legro
Area Forecast Discussion
National Weather Service Louisville KY
920 PM EDT Tue Aug 17 2021 .Forecast Update... Issued at 920 PM EDT Mon Aug 17 2021 Convection has dissipated across the forecast area this evening. Back edge of rain shield from the remnants of Fred continues to straddle our border with WFO JKL. The back edge is pivoting back to the west slightly, but should continue to pull more back to the east over the next several hours as the remnants continue to push off to the northeast. Will hold on to some isolated/scattered showers over our far eastern sections through about 18/06-7Z or so and then go dry after that. Out to our west, some isolated convection was beginning to fire from Evansville south to near Hopkinsville. HRRR runs had been hinting at that, but those solutions keep that activity west of our area and then dry it up around midnight or so. For the overnight period, we expect low stratus to redevelop across the region. The most stratus will be located east of the I-65 corridor with some potential for fog. More widespread fog development will be possible out west of I-65. Widespread fog threat is not overly high. However, areas and/or pockets of dense fog will be possible, similar to last night. Areas that saw appreciable rainfall this afternoon will likely be the areas that see the most dense fog. Will go ahead and throw out a Special Weather Statement for the western half of the CWA to highlight the fog threat. && .Short Term...(This evening through Wednesday) Issued at 222 PM EDT Tue Aug 16 2021 Isolated to scattered showers have developed this afternoon across the region. The bulk of the showers have generally been confined to locations between the I-65 and I-75 corridors, where weak convergence has aided in convective development. Up to this point, there has been very little to no lightning activity with this precipitation. Visible satellite shows a modest cu field west of the I-65 corridor where upper level clouds have been a little thinner today and allowed for surface heating to reach near convective temperatures. Additional shower and occasional storms may fire off in these areas this afternoon and early evening. Once the sun sets, we should see precipitation activity taper down in coverage. Clouds associated with Tropical Depression Fred will move off to the northeast overnight, and should allow for a good period of clearing for a decent portion of the region. With high moisture content in place near the surface and light to calm winds, this should be a good setup for fog/stratus to develop around or shortly after midnight. If we had widespread rains today, would be concerned about dense fog potential... but think that dense fog should be limited to concentrated areas and isolated in nature. Fog and stratus should slowly burn off after sunrise tomorrow, with it lingering the longest toward the Kentucky Bluegrass where it will likely be thickest. The morning and early afternoon hours should start out dry, with PoPs increasing toward the mid and late afternoon hours ahead of a weak wave moving in from the west- southwest. There will be a very marginal amount of shear associated with the wave moving into a modestly unstable environment, so some organized clusters and/or broken lines of convection could move into central Kentucky after 21z. SPC has highlighted portions of central Kentucky in a Day 2 Marginal Risk for severe weather, which seems appropriate given the circumstances. .Long Term...(Wednesday night through Tuesday) Issued at 200 PM EDT Tue Aug 17 2021 A weak upper level low drifts northeast across Lower MI Wednesday night into Thursday. Particularly 06-12z Thursday, central KY and southern IN will be beneath the right entrance region of a very modest 55 kt 250 mb jet streak. A mid-level shortwave trough draped south across the mid-MS Valley will be favorably positioned just upstream, but height falls look quite weak. In addition, a subtle mid-level ripple in the flow does look to lift ENE from the Memphis area Wednesday night. HREF members point to the possibility of a band of convection moving east, just ahead of the TN wave. Stronger convection looks most likely across Middle TN, but certainly enough confidence to go high chance/likely hourly PoPs across south-central KY around and shortly after 00z Thu. Convection will diminish in coverage and intensity overnight. ML/MUCAPE already looks somewhat modest by 00z and steadily diminishes overnight. Surging PWATs from the southwest will support occasionally heavy or even torrential rainfall. At least scattered showers are likely to be ongoing at 12z Thursday, and hi-res models suggest the best chance across southern IN and northern KY in proximity to a weak sfc trough and the axis of deepest moisture. Weak plenty of moisture and the weak upper trough still overhead, diurnal scattered convection will be possible Thursday. However, the moist profile and cloud cover will likely limit sfc heating. Wind fields will remain weak, but given the moisture, some locally heavy rain will be possible. Highs should be in the upper 70s to lower 80s for most. Moisture depth diminishes Thur night into Fri as the primary upper trough axis shifts further east, but the upper low will be trapped over Ohio with high pressure off to the north and east. Despite the continued cyclonic flow aloft, precip coverage should be lower Fri with more isolated activity. There could be a window Fri night into Sat with a better chance for rain/storms with warm, moist air advection ahead of a sfc trough. This occurs just before the broad subtropical ridge across the southern tier of the US strengthens and expands northward this weekend into early next week. This does look to bring a stretch of hot, humid conditions with generally more sparse precip coverage. && .Aviation...(00Z TAF Issuance) Issued at 723 PM EDT Tue Aug 17 2021 IMPACTS: -Fog impacts in areas mainly west of I-65 (KHNB/KBWG) -Low clouds and some fog possible over at KLEX DISCUSSION: Scattered showers continue to move through the region this evening as we remain on the northwest periphery of the remnants of tropical cyclone Fred. Expect convection to wind down over the next hour or two across the area with the main rain shield remaining just east of the I-75 corridor. Models still have a good fog signal for KHNB/KBWG. Hit KHNB harder with fog on this package and kept a similar forecast for KBWG. Some patchy fog is possible at KSDF, but vsbys should remain around 6SM or above through the period. KLEX will see a gradual build down in cloud cover overnight with winds shifting from the east-southeast to the northeast, then to the northwest as the remnants of Fred pass by. Some patchy fog and low stratus are likely to affect that terminal late tonight and into Wednesday morning. CONFIDENCE: Medium to high on all elements at all sites. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update.......MJ Short Term...DM Long Term....EBW Aviation.....MJ
Area Forecast Discussion
National Weather Service San Francisco Bay Area
538 PM PDT Tue Aug 17 2021 .SYNOPSIS...Cooling trend has begun in our region as an upper- level trough tracks across NorCal. Dry, gusty offshore winds will result in critical fire weather conditions across the interior North Bay Mountains and portions of the East Bay Hills from tonight into Wednesday. Smoky and hazy conditions will also return to the Bay Area with the arrival of northerly winds through midweek. && of 03:00 PM PDT Tuesday...It`s a cool afternoon today. Many observation sites are reporting current temperatures ranging 3 to 14 degrees cooler than 24 hours ago. The upper level trough is currently over NorCal and it rapidly increased the marine layer depth this morning to about 2000 ft. Much of the marine stratus has scattered out along the North Bay coastline but we have some lingering low level clouds along the SF Peninsula and around portions of the Monterey Bay area. Biggest concerns are the elevated fire weather risk tonight into Wednesday due to gusty offshore winds along with impacts from higher concentrations of smoke near the surface. The forecast is still on track as hi-res models continue to show enhanced N to NE winds moving into the Napa County hills tonight. The enhanced winds are likely to spread into the interior hills of Sonoma County and into the East Bay hills. Peak gusts are still within the range of 30-45 mph with highest peaks potentially reaching up to 55 mph. Also, relative humidity values will be lower due to the drying impact of the offshore winds. Thus, the Red Flag Warning remains in effect from 11 pm tonight through 3 pm Wednesday. NOTE: enhanced winds may develop in far NE Napa County a little earlier (around 9 pm). The models do indicate that there could be a secondary round of N to NE winds Wednesday night into Thursday morning, but at this time it looks to be weaker than the first round. However, we will be monitoring that in case the Red Flag Warning needs to be extended. Another impact of the N to NE winds is that they will transport the smoke from NorCal wildfires down into our region. The timing is the same as the Red Flag Warning....near surface smoke concentrations will increase in the North Bay tonight and then spread southward overnight into Wednesday which will impact the rest of the Bay Area including South Bay and may even reach into Santa Cruz County. If you notice higher levels of smoke, take precautions by keeping your windows closed or wearing masks if outdoors to prevent you from breathing in the particulates. As we get into Thursday, the trough will linger over the Great Basin to our east. Our temperatures are expected to be fairly seasonable for the rest of the week as we get back into our typical marine influenced summer pattern. In the extended forecast, the ECMWF and GFS show another trough moving into the west coast on Saturday with the potential for a third trough early next week. That means no significant heating events in the long term forecast. && of 05:30 PM PDT Tuesday...For the 00z TAFs. VFR conditions presently prevail at all terminals, with marine stratus having now cleared entirely aside from areas near the shoreline of Monterey Bay. Expect overnight redevelopment to be more limited than last night, at least from around the San Francisco Bay Area northward, as drier offshore flow develops. However, latest HRRR smoke forecast continues to show these N/NE winds will advect both near surface and total column smoke to the region. This will result in worsening surface and slant range visibility tonight in the North Bay and Wednesday across the SF Bay Area, with some smoke potentially making it down to Monterey County by Wednesday afternoon. Breezy onshore winds into this evening, though less so than yesterday. Gusts of about 20-25 kt along the coast anticipated before winds diminish overnight. N/NE winds aloft at about 1,500 to 2,000 feet will increase over the interior North and East Bay later tonight. This may result in some minor LLWS issues. Vicinity of KSFO...VFR. Some scattered low clouds may return later tonight, but moderate confidence in forecast of no ceiling development. Breezy onshore winds through mid-evening with peak gusts into the 25-30 kt range, but not as windy as yesterday. Slant range visibility issues by late tonight as smoke drifts in from various wildfires. Some reduced surface vis may occur tomorrow morning/afternoon. KSFO Bridge Approach...similar to KSFO. Monterey Bay...Latest satellite images show just one area of marine stratus still persisting, over the coastal plain and hills adjoining the central portion of Monterey Bay. Low clouds are anticipated to return this evening as the marine layer remains in place. Winds aloft will shift offshore late tonight drifting wildfire smoke over the area on Wednesday, potentially resulting in some reduction of slant range visibilities. && of 02:00 PM PDT Tuesday...Strong north to northwest winds today with gale force gusts will continue over the northern and outer waters through Wednesday morning. Winds are forecast to peak tonight before diminishing on Wednesday. These strong winds will generate locally steep waves and result in hazardous seas conditions. Winds will ease across most of the waters on Wednesday, but locally breezy conditions will persist over the northern outer waters. Seas remain mixed with a light southerly swell as a result of tropical cyclone activity to the south along with a weak northwest swell. Steeper short period northwest waves also continues at periods of 7 to 9 seconds. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...Red Flag Warning...CAZ507-511 SCA...SF Bay until 9 PM SCA...Mry Bay until 9 PM SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 9 PM GLW...Pt Arena to Pigeon Pt 10-60 nm SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm GLW...Pt Arena to Pt Reyes 0-10 nm until 3 AM SCA...Pt Reyes to Pigeon Pt 0-10 nm until 3 AM && $$ PUBLIC FORECAST: Bingaman AVIATION: Blier MARINE: AS Visit us at Follow us on Facebook, Twitter, and YouTube at:
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 225 PM CDT Tue Aug 17 2021 Quiet weather continues across the area for the next couple of days, with active weather returning by Friday as a frontal boundary moves into the area. Geocolor satellite imagery shows a smoke layer aloft continues to affect northeast NE, and recent HRRR smoke model output suggests this may remain status quo tonight but may thin a bit Wednesday. At least the smoke doesn`t appear to be impacting air quality or surface visibility at this time. Wednesday will be similar to today, with mostly sunny skies, southerly breezy winds, and highs again in the upper 80s to lower 90s. When combined with the humidity, heat index values will again range in the lower to mid 90s. This temperature trend continues into Thursday. And a few locations along/south of I80 could make a run for heat index near 100 Thursday afternoon. Precip chances may begin increase Thursday afternoon south I80, but really increase Thursday night ahead of a cold front that moves into the area Friday. Scattered to numerous storms will be eventually become possible Friday into Friday evening. SPC placed a good portion of the area in a 15% probability of severe on their day 4 outlook this morning, so severe weather potential is something we`ll be looking at more closely as we get closer. For Saturday, we`ll probably cool down slightly in the lower to mid 80s with dry weather. But the heat returns for Sunday with highs back into the mid 80s to lower 90s. There will also be spotty storm chances in the extended period, but honestly confidence is pretty low in the details as models are generally out of sync on the timing. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 554 PM CDT Tue Aug 17 2021 LLWS threat appears to be focused at KOFK after 06Z tonight. Otherwise VFR conditions will prevail through the period. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...DeWald AVIATION...DEE
National Weather Service Raleigh NC
945 PM EDT Tue Aug 17 2021 .SYNOPSIS... The remains of Tropical Storm Fred will track slowly north through the southern Appalachians through early Wednesday. After this system moves north and away from the area, typical warm and humid summertime weather will return to the region later in the week, with a daily risk of scattered storms. && .NEAR TERM /THROUGH TONIGHT/... As of 945 PM Tuesday... TD Fred`s center is located over far E central TN, near the NC border, at this hour, and it will continue to track northward over the S Appalachians overnight, reaching W WV toward daybreak. The anticipated relative lull in precip over central NC continues this evening, with only isolated to scattered disorganized showers in the last several hours. While this low-pop period should persist for another hour or two, attention then turns to the line of strong and potentially tornadic storms E of Fred, over the NC Foothills into W and central SC. The latest HRRR runs take this line into our W shortly after midnight and drift it slowly eastward (although individual convective elements will be moving nearly due N) overnight, reaching the Triangle region toward sunrise. While nocturnal stabilization with loss of heating would seem to be in our favor here, the current RAP-estimated MLCAPE remains 1000-1500 J/kg, with the better effective deep layer shear and 200+ m2/s2 SRH both expected to continue to ease slowly from W NC northeastward across the NW Piedmont overnight. So, we are not yet out of the woods in terms of both a severe threat (mainly in the NW Piedmont overnight) and a heavy rain threat (with training cells and still-anomalously- high PW likely to lead to higher totals). Have made some pop adjustments to account for this timing and threat heading through tonight and into early Wed morning. Still expect lows mostly in the low to mid 70s. -GIH Earlier discussion from 325 PM: Fred has weakened to a tropical depression, with its circulation center approaching the southern NC mtns. The weakening remnants of Fred will continue to track north- northeast through the NC mtns during the late afternoon and evening hours. With the 2.0-2.3" tropical moisture centered over central NC, intermittent shower activity will continue through tonight, with some daytime enhancement of some thunderstorms through the afternoon. In the wake of the broken convective band that`s currently moving north through the northern Piedmont and northern coastal plain counties, latest radar trends suggest central NC will experience a late afternoon/early evening lull. Rain chances are then expected to increase after midnight as the primary rain tropical rain band(currently over central SC and eastern Ga moves through the area. Additional rainfall amounts through daybreak are expected to range from a half inch across the NW Piedmont to around a tenth of an inch across the NE coastal plain. Despite the recent increase in rain that central NC has seen over the past several days, rainfall amounts have been hit and miss. Antecedent hydrological conditions are still rather dry, with 1 to 3 hr FFG still in the 2.5-3.5" range. Thus, do not think a Flash Flood watch is warranted, with only isolated instances of minor flooding possible, mainly in poor drainage and/or urban areas. Additionally, close proximity to Fred`s stronger low-level wind field will provide some favorable low-level kinematics to support some rotation within any strong updrafts that develop, mainly during peak heating and across western NC. Lows tonight in the 70s. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 325 PM Tuesday... The remnants of Fred will race newd away from the area, moving through the central Appalachians through the afternoon, and reaching the NE US by the evening. The tropical moisture plume of 2-2.25" will shift eastward over eastern NC by late morning/early afternoon, with slightly drier filtering into western piedmont counties. Scattered showers and thunderstorms will continuously re-develop within this axis of anomalously high PWATs, with diurnal destabilization allowing for some isolated/widely scattered re- development back over the western Piedmont. Could still see some locally heavy rain that could result in some minor flooding. Otherwise, weak shear and lapse rates should preclude a severe threat. Highs ranging from mid 80s west to upper 80s east. Cannot rule out some isolated showers Wednesday evening, but otherwise it should be mostly dry Wednesday night with areas of fog possible. Lows 70 to 75. -CBL A negatively-tilted mid-level trough will approach the region on Thursday, resulting in decent height falls and forcing for precipitation. Thus, have high chance POPs on Thursday. A subtropical ridge will also extend across the western Atlantic on Thursday, which will pump warm and very humid air into our region, with highs in the upper-80s to lower-90s and dew points in the mid- to-upper-70s. This could bring heat indices up to 105F in portions of the eastern Piedmont, Sandhills, and southern Coastal Plain, and a Heat Advisory may be needed for this area on Thursday. -JD && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 945 PM Tuesday... Fri/Fri night: A surface frontal zone to our NW, on the SE side of the baggy closed low over OH/WV/PA, will slowly drift southeastward into central NC. This weak low level mass convergence plus incoming DPVA aloft, increasing upper divergence in the LFQ of a 60+ kt northwesterly jetlet over the Ohio Valley, and 2-2.25" PWs streaming over much of our area (esp E) all support high pops, peaking in the afternoon/evening. Thicknesses will still be a bit above normal but temps should be modulated by considerable cloudiness. Highs around 90 to the lower 90s. The combination of incoming surface high pressure drifting over WV, the surface circulation around Henri as it moves northward well off the NC coast, and SE-moving convection outflow Fri evening and night should help push the surface front to our E and S sections overnight. Lows 70-76 with decreasing pops and partial clearing W late. Sat through Sun night: The surface front should hold over our SE CWA Sat, prompting better convection coverage there in the afternoon in contrast to the slightly drier NW sections. Then, as so often happens with summertime fronts over NC, the front should quickly lift north and effectively wash out by Sunday, as mid level ridging builds anew from TX/OK across the lower Miss Valley and Mid South to the interior Southeast states. But Henri may still affect our weather as it is expected to drift N or NNW over the NW Atlantic toward the New England coast over the weekend: Depending on its exact location and the degree to which it merges with the mid level low, there is a chance that the surface front could hold up across our far NE, if the Henri circulation prompts frontogenesis in that area. Will retain mostly diurnally-favored pops Sun, highest in our E half (SE and along the front in the NE), where low level moisture should be most abundant. Expect highs both days close to normal, in the upper 80s to around 90, with lows in the upper 60s/lower 70s. Mon through Tue: Tough forecast as NC will be the battleground between the Southern Plains / Lower Miss Valley mid level ridge and the baggy trough / shear axis extending along the East Coast, with any surface features very weak. The ECMWF keeps pops high, esp E (assuming warmer mid levels and lower CAPE further W). The latest few GFS runs are drier but have trended toward less ridging extending into the Carolinas and a greater number of ridge-riding MCSs or MCVs tracking from the Midwest and Ohio Valley through VA and NE NC. Without a clear signal favoring one way or the other, will stay the course with temps near to slightly above normal, esp W, and pops close to climatology, chances of mainly afternoon storms, higher SE. -GIH && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 815 PM Tuesday... The remnants of TS Fred will continue to move north through the NC mountains tonight and early Wednesday. While there is a lull in showers across central NC this evening, a line of showers and isolated storms in upstate SC will move gradually north-northeast overnight, impacting GSO/INT between roughly 04-08Z, with scattered showers possible further east toward RDU/RWI/FAY overnight. Very heavy rain and low vsbys will occur within the showers and storms. The line of showers will continue to move east during the morning hours and may increase again during the day on Wednesday. Ceilings will lower to MVFR/IFR overnight and only gradually lift to VFR through Wednesday afternoon as winds shift from SErly tonight to SSWrly on Wednesday. Outlook: Afternoon showers and storms will return Thursday and continue each day through the weekend. Sub-VFR conditions from fog/low stratus will be possible each morning. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield/CBL SHORT TERM...CBL/Danco LONG TERM...Hartfield AVIATION...Smith
Area Forecast Discussion
National Weather Service San Diego CA
847 PM PDT Tue Aug 17 2021 .SYNOPSIS... A low pressure system moving into the West will bring stronger onshore flow with gusty westerly winds in the mountains and deserts. The marine layer will deepen and should produce some drizzle or a few light showers for the coast, valleys, and foothills, mainly late nights and mornings into Thursday. Clearing may be difficult in many areas west of the mountains on Wednesday. High pressure to the east will bring warmer weather and less extensive coastal clouds next week. && DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low clouds had already blanketed much of the immediate coast by sunset and are now surging inland. Skies were clear inland except for some smoke aloft. The onshore sfc pressure gradients have turned sharply onshore, reaching 11 MBS from San Diego to SW NV early this evening. West wind gusts peaked at 50 MPH through the San Gorgonio Pass and remain around 30 MPH with gusts to 45 MPH. These gusty winds will continue through tomorrow night, building the marine layer clouds onto the lower coastal slopes and into the passes. The forecast has been updated this evening to remove the isolated thunderstorm threat and to modify POPS/QPF through 36 hours to more closely mirror the 00Z HRRR guidance. With the aid of upslope, HRRR forecast QPF now exceeds 1/3 to 1/2 inch on favored coastal slope locations of the Santa Ana and San Bernardino Mts through Thursday morning. Some coastal areas have between 1 and 2 tenths of an inch as well. From previous discussion... A low pressure trough is amplifying across the West today and Wednesday. This is rather unseasonal for this time of year and will extend our deepening marine layer while shoving monsoonal moisture to the east. A coastal eddy will also develop to contribute to all this deepening. This is expected to thicken the clouds as well as extend them into most if not all of the valleys overnight. Areas of drizzle or a few light showers are expected late tonight into Wednesday and again Wednesday night into Thursday, most likely in the foothills or near the coast. Temperatures near normal today will dip below normal Wednesday through about Saturday. For folks in the inland valleys, waking up to low clouds overhead and high temperatures in the 80s will be quite a change from what most of our summer has featured. The trough moving through the West will also boost onshore westerly winds through mountain passes and desert slopes the next few afternoons and evenings, with gusts exceeding 40 mph in the favored passes. The trough departs Friday, but another trough fills the void by Saturday across the West. This one is weaker, so the onshore breezes, marine layer cloudiness and temperatures will not respond as profoundly as with the bigger trough. Next week, ensembles show some rebuilding of a high pressure ridge over the West, but with differing strengths. Some solutions also show the monsoon door opening a crack sometime next week, for now beyond our forecast window. There will be a warming trend, which could return temperatures back to near normal Monday or Tuesday, while restricting coastal clouds nearer to the coast. && .AVIATION... 180345Z...Coast/Valleys...BKN-OVC stratus with bases 1000-1500 ft MSL and tops to 4000 ft MSL will spread rapidly inland through the valleys by 07Z with areas of higher terrain obscured. SCT -SHRA will will occur mainly 09Z-19Z Wed especially over higher terrain, with local vis 2-4 miles in -SHRA/BR. Clearing will be slow and partial Wed with BKN-OVC clouds becoming SCT-BKN 18Z-21Z Wed and bases rising to 1500-2000 ft MSL with tops locally to 5000 ft MSL. BKN-OVC stratus is likely again Wed night with more SCT -SHRA. Mountains/Deserts...Areas of west/southwest winds 15-25 KT gusts 30- 45 KT will occur from the mountain crests east/north through the desert slopes and into the deserts with strong up/downdrafts through Wed evening, with strongest winds Wed afternoon/evening. Areas of terrain obscurations will occur on the coastal slopes below 4000 ft MSL tonight and below 5000 ft MSL Wed/Wed evening due to clouds and - SHRA. && .MARINE... No hazardous marine conditions are expected through Sunday. && .BEACHES... A south-southwest swell of 3 ft/17-19 sec from 200 degrees will build Wednesday evening, peak Thursday and Friday, then slowly lower this weekend. This will generate surf of 4-6 ft with sets near 7 feet along south-facing beaches of Orange County Thu and Fri. Strong rip currents and dangerous swimming conditions are expected. Above average high tides peaking near 6.5 feet will also occur, which may lead to coastal beach erosion and minor flooding. Please see the Beach Hazards Statement for the latest details. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement from Wednesday evening through Friday evening for Orange County Coastal Areas. PZ...NONE. && $$ PUBLIC...10/MM AVIATION/MARINE/BEACHES...Maxwell
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
857 PM MDT Tue Aug 17 2021 .UPDATE... Issued at 853 PM MDT Tue Aug 17 2021 Thunderstorms that were located over parts of far western South Dakota have now ended. UPDATE Issued at 453 PM MDT Tue Aug 17 2021 Isolated high based thunderstorms have developed along a N-S surface trough currently located near the SD/WY border. Expect little or no rainfall from these storms so may see a couple of wildfires develop due to the lightning. && .DISCUSSION...(This Evening Through Tuesday) Issued at 217 PM MDT Tue Aug 17 2021 Upper air analysis shows upper ridging over the northern plains and an upper trough digging into the western CONUS. As the trough slides eastward, an associated surface low approaches western SD, expected to pass through later Wednesday. Ahead of the low, a tighter pressure gradient will bring in breezy conditions today. Coupled with temps reaching into the 100s today and RH values nearing 10 percent, a red flag warning is in effect for northeastern WY and western SD. Smoke aloft and near surface continues to restrict visibility throughout the forecast area. Have kept mention of smoke in through Wednesday based off the HRRR model. As we progress towards mid-week, ridge slides eastward and upper trough shifts over the rockies. Timing of frontal passage Wednesday will be key in high temperatures, as models still differ a bit on timing, but expect passage during heating hours. Ensembles still have a 12 degree spread based off differing timing. Following frontal passage, winds will shift out of the north and the region cools down. Highs for Thursday are only expected to get up to the mid 60s for northeastern WY and the black hills, with warmer temps in the 80s closer to central SD. CAMs all agree on potentially widespread showers/storms late wednesday into Thursday following the front. With increased buoyancy and moderate shear in the region, SPC has us in a marginal risk severe. High PWATs also point to at least some areas seeing some locally heavy rainfall. A more active pattern is expected approaching the weekend, as the upper trough slowly slides eastward into the midwest. Models show the upper low moving through the northern plains around Friday/Saturday, bringing more potential for precipitation. && .AVIATION...(For the 00Z TAFS Through 00Z Wednesday Evening) Issued At 522 PM MDT Tue Aug 17 2021 Areas of MVFR visibility due to smoke will continue tonight with some improvement during the day on Wednesday. Isolated thunderstorms, with locally gusty winds, are possible over parts of northeastern Wyoming and far western South Dakota through 03Z this evening. && .FIRE WEATHER... Issued at 853 PM MDT Tue Aug 17 2021 A cold front will slide into northeastern Wyoming tonight and western South Dakota Wednesday. Elevated fire weather conditions are expected in the warmer air ahead of the front on Wednesday afternoon. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...WY...None. && $$ Update...10 DISCUSSION...Dye AVIATION...10 FIRE WEATHER...10
Area Forecast Discussion
National Weather Service Las Vegas NV
832 PM PDT Tue Aug 17 2021 .SYNOPSIS...Low pressure dropping into the Great Basin will bring a cooling trend to the region while also limiting monsoonal thunderstorm activity to eastern Lincoln, Clark and Mohave counties through Thursday. Breezy conditions can be expected as well. Temperatures will remain slightly below average through the weekend with generally dry weather. && .UPDATE...Thunderstorms have been very isolated and relegated to Lincoln County and northern Mohave County. Am tracking an outflow boundary moving west across Coconino and just starting to enter Mohave County over the Grand Canyon/Kanab Creek region. Question is just how far west this may go to support convection the rest of this evening. camPops suggest the threat for isolated thunderstorms will remain across parts of Lincoln, as well as parts of Mohave County overnight. Trough dropping south into the Great Basin will continue to support gusty south-southwest winds the rest of tonight through Wednesday. The Lake Wind Advisory remains in effect through tomorrow evening. Another issue tonight will be the continued smoke/haze and lower visibilities across parts of Inyo, Esmeralda and Nye Counties. A storm spotter in Goldfield reported the visibility down to about a half mile. Populated grids using the 00Z HRRR Smoke with NBM showing area of lower visibility in the previously mentioned counties. Sent out an update for the rest of tonight. && .SHORT TERM...through Thursday night. Main focus of the short term period will be around thunderstorm chances and gusty winds as a large trough develops into the Great Basin. Ahead of this trough, rich monsoonal moisture continues to stream north, up the Colorado River Valley and into mainly eastern Lincoln county en route to the eastern Great Basin. Its mainly along and east of this axis where thunderstorm chances will be confined. This afternoons RAP analysis suggests 1000-2000 j/kg of mixed layer CAPE is present across northern and eastern Lincoln county along with 20-25 knots of deep layer westerly shear. While not expecting widespread thunderstorms as the the stronger forcing will be further north into Utah, a few isolated storms forming in this environment through the evening may pose a risk for strong downdraft winds and isolated hail to nearly a quarter size. The Storm Prediction Center has highlighted the northern Panhandle of Lincoln County in a Slight risk of severe storms through the evening. The aforementioned trough will dig southward Wednesday, reaching into the Great Basin by the afternoon. Mid level temps will be cooling through the day, though moisture will remain limited to our eastern zones. Expecting a similar overall outcome with thunderstorm activity on Wednesday, though overall forcing will be a little stronger while instability will trend weaker. The trough will push east into Utah on Thursday, with thunderstorm chances shifting to our far eastern border before drying out completely for the remainder of the week. Outside of storm chances, areas of smoke have been prevalent across the region as the flow aloft shifts more westerly and blows California wildfire smoke our direction. This will continue to occur for the next several days as the trough to our north dominates our local wind flow patterns. Greatest reductions in air quality and visibility will be across Inyo, Esmeralda, and central Nye counties, with more of a pesky haze elsewhere. Breezy south winds have also been noted as pressure gradients increase in response to the incoming Great Basin trough. These winds will stick around overnight and into Wednesday before easing on Thursday. Winds have been strongest on the Nevada National Security site in Nye county where gusts over 40 mph have been reported, though most areas have seen gusts in the 25-30 mph range. Gusty winds have also been ongoing across Lake Mead and Mohave, and the Lake Wind Advisory through tomorrow still looks good. On the plus side, the deep trough will result in a cooling of regional temperatures, with afternoon highs falling a few degrees below normal Wednesday and Thursday. .LONG TERM...Friday through next Tuesday. As the Great Basin trough lifts eastward Friday, another trough is likely to drop south in its wake for the weekend, keeping the West in a somewhat cool and breezy pattern. This will keep monsoonal moisture at bay and also maintain fairly moderate temperatures by August standards. Temperatures will gradually rebound closer to normal next week as low amplitude high pressure begins to rebuild across the Southwestern US. && .AVIATION...For McCarran...Breezy south to southwest winds will continue through the early evening. Expecting a stronger period of winds 23Z-04Z this evening, with gusts over 25KT likely and gusts over 30KT possible. For tonight, moderate confidence gusts will decrease to 20-25KT after 06Z but continue through the night. There is a low chance that gusts end at 06Z. Either way, elevated south winds at 10-15KT will continue through the night. Winds may vary 150- 180 degrees 09Z-14Z before increasing again out of the south- southwest late Wednesday morning. Gusts to around 25KT are likely through Wednesday afternoon. Other than winds, no impactful clouds are expected with dry conditions persisting through the period. For the rest of southern Nevada, northwest Arizona and southeast California...Isolated thunderstorms are possible across south- central Nevada and western Arizona this afternoon and evening. Best chances will be through Lincoln County into southwest Utah. Otherwise, Gusty south to southwest winds will continue across the region through the evening before diminishing early tonight. Winds will increase again late Wednesday morning and afternoon, with the strongest winds on Wednesday likely up the Colorado River Valley. Smoke will spread south through the southern Great Basin tonight and Wednesday morning, with visibilities around 5-6SM possible at BIH after 09Z tonight through 15Z. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...Pierce DISCUSSION...Outler AVIATION...Nickerson For more forecast information...see us on our webpage: or follow us on Facebook and Twitter