Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/24/21

Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
537 PM MDT Mon Aug 23 2021 .AVIATION... 00Z TAF CYCLE Isolated to scattered showers and thunderstorms will continue into the early evening and then mostly diminish before midnight. Activity will remain concentrated along and south of the Interstate 40 corridor with a few strong to briefly severe cells capable of producing heavy downpours, small hail and gusty downburst winds. Thunderstorms on Tuesday will likely be fewer in number, remaining concentrated over the southwestern to west central mountains of New Mexico while just a few isolated cells develop along and east of the central mountain chain. Hot temperatures and high density altitude readings, especially in the eastern plains of New Mexico, will create difficult ascents for some aircraft. 52 && .PREV DISCUSSION...304 PM MDT Mon Aug 23 2021... .SYNOPSIS... Fewer storms and above average daytime temperatures will be the trend for Tuesday through Wednesday. Highs in the mid 90s to near 100 are expected across eastern New Mexico while upper 80s and 90s will be common for the central and west. These readings will be 5 to 10 degrees above seasonal averages for most locales. Storm coverage will then ramp up on Thursday, especially for the northern half of the state, as a disturbance passing north of the state draws moisture northward. A relatively active monsoon pattern will persist Friday into the weekend with daily rounds of thunderstorms favoring the west and north. Daytime highs should trend closer to seasonal average for Thursday through the upcoming weekend. && .DISCUSSION... SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)... 594dam 500mb high centered near the ArkLaTex and extending a ridge axis west into southern NM per the 12Z upper air analysis. The latest water vapor imagery shows moisture from the eastern Pacific, where TS Marty resides, being pulled northeast across northern Mexico and into southern NM. The 12Z KEPZ sounding confirmed this with a well above normal PWAT of 1.5" and even the KABQ sounding had a PWAT near 1". Surface dewpoint temperatures were an average 4 degrees higher across portions of central and western NM at 1PM compared to 24hrs prior. Given some daytime heating, all of this adds up to a decent round of storms this afternoon, with the focus for deeper convection and stronger storms capable of producing locally heavy rainfall generally south of I-40 in the higher PWAT airmass. Storms closer to our southern border under the ridge axis will be moving slower and more capable of producing torrential downpours with localized flash flooding. Both the latest HRRR and HREF show convecting winding-down shortly after sunset, but the NAM shows precipitation continuing overnight across southern portions of our area similar to last night. Regardless, coverage and intensity will trend down with the loss of daytime heating this evening. Tuesday is looking very similar to today overall with slightly higher pressure heights near 593dam at 500mb and above normal high temperatures, especially across eastern NM. A drier airmass to our west is forecast to get wrapped into the upper high circulation across northwest and north central NM Tuesday and should put the brakes on convection north of I-40 and west of I-25. Storms across the southern high terrain will be capable of producing locally heavy downpours Tuesday afternoon, with the potential for localized flash flooding once again. LONG TERM...(WEDNESDAY THROUGH MONDAY NIGHT)... Wednesday looking to be among the least active days of the forecast period. Shortwave trough modeled to move inland long the northern CA and PacNW coasts early Wednesday resulting in weak compensatory height rises downstream over our part of the world. As a result, the models generally show the strong 595 dam H5 high over the Southern Plains briefly expanding westward. Latest blended PoP guidance trended a little downward for Wed PM and this seems reasonable under what should be slight warming aloft and A weakly forced environment. The above mentioned upper trough to cross the Great Basin eventually nearing the central Rockies late Thursday. Ahead of this wave, a corridor of enhanced forcing for large-scale lift should develop and support a noticeable uptick in storm coverage particularly from WC through NW and NC areas for Thursday afternoon and evening. We would not rule out the possibility of strong if not severe storms in this regime given increasing swly flow aloft though storm motions may preclude significant FF potential. PWAT time series reflect values generally at or just above seasonal averages. And with the west to east oriented upper ridge axis getting forced southward, we are not likely to see a significant moisture tap during this period. The tail-end of this upper wave should graze northern New Mexico Thursday night. Thereafter, GEFS and EPS mean 500mb height fields suggests the upper high reorganizing over the area this weekend with the ridge axis near the NM/AZ line. Meanwhile, this forecaster was expecting to see a weakening backdoor cold front appear across northeast NM in wake of the upper trough passage through the Central Rockies. There may be some evidence for late Friday with another frontal feature for Sunday, but nothing too impressive. KJ && .FIRE WEATHER... No fire weather concerns for at least the next seven days as northern and central NM remain under the influence of ridging aloft with bouts of wetting storms. Some drying through Thursday will limit the wetting rain footprint, which should expand Friday through the weekend as the ridge weakens and PWATS creek back to normal or slightly above normal for the end of August. 11 && .ABQ WATCHES/WARNINGS/ADVISORIES... None. && $$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
906 PM MDT Mon Aug 23 2021 .UPDATE... Issued at 906 PM MDT Mon Aug 23 2021 A couple of strong storms developed in Logan county over the past hour. They`re on the edge of the better moisture, which is also cooler. With the moisture and some convergence on the front of these cells, they will probably continue as they are but we don`t think they will get much stronger than they are now. The rest of the forecast is looking good, with clearing skies. && .SHORT TERM...(This evening through Tuesday) Issued at 252 PM MDT Mon Aug 23 2021 A persistent southwesterly flow aloft will be over the region through Tuesday. Enough moisture entrained in the flow aloft to produce a few high based showers or thunderstorms. Main concern this afternoon and evening will be gusty outflow winds in the 40-50 mph range. The latest HRRR runs suggests this potential. The storms will diminish by midnight. Too dry and stable on Tuesday for thunderstorms with high temperatures back into the mid 90s. Fire danger will be high over North and Middle Parks, reference the fire weather discussion for details. .LONG TERM...(Tuesday night through Monday) Issued at 252 PM MDT Mon Aug 23 2021 Southwest flow aloft will persist over northeast Colorado for much of the week between troughing over the northwest and ridging over the southcentral and southeast parts of the country. Tuesday evening will be clear and dry, and a weak cold front will move over the plains Tuesday night as a disturbance moves through the southwesterly flow aloft. The front will bring slightly cooler temperatures to the lower elevations Wednesday, with highs down to the upper 80s and lower 90s across the plains. Models are showing an increase in low to mid level moisture as well, of maybe 2 to 3 g/kg in the specific humidity fields, which should be enough for isolated showers and storms to develop in the afternoon and evening. Greater low level moisture and instability on the northeast plains, where there could also be around 30 to 40 knots of bulk shear, might support a few severe storms in that area. A stronger trough will move over the northern and central Rockies Thursday and Thursday night, and model agreement is improving about a deep enough trough far enough south to provide some forcing over northeast Colorado. There should also be better moisture ahead of the trough with precipitable water values up to over an inch across the plains and to around two-thirds of an inch over the higher terrain. Expect scattered showers and storms with an isolated severe threat again. Heavy rain may also be possible from the stronger cells but increasing mid level winds should keep storms moving fast enough to mitigate the threat. I once again primarily moderated increases in PoP and QPF in the extended period. Friday is expected to be drier behind the trough with temperatures fairly similar to those Thursday. There could be enough moisture in place for some more isolated, low impact showers. It looks like there might be a westerly stream of smoke in more zonal flow aloft between troughs as well. Another trough should move over the northern and central Rockies Saturday, which still looks to be a little too far north for serious impacts to northeast Colorado. It may bring some more isolated to scattered weak showers and storms, and another front over the plains late Saturday with some cooler air for Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 906 PM MDT Mon Aug 23 2021 VFR through Tuesday. Winds will become southerly by 06z. A period of west winds around 10 knots is expected Tuesday morning before winds go northerly by 18z. && .FIRE WEATHER... Issued at 252 PM MDT Mon Aug 23 2021 Hot and dry on Tuesday with a moderate southwesterly flow aloft over the forecast area. The fire danger will be high over the mountain valleys of Jackson, Grand and Summit counties. Gusty winds to 30 mph and RH values down near 10 percent enough to warrant a Fire Weather Watch for Tuesday afternoon. The Fire Weather Watch for North and Middle Parks will continue into Tuesday evening until 8 pm, as there is potential for critical humidity in the 10 to 15 percent range and with gusts exceeding 25 mph to persist in these areas. We have issued another Fire Weather Watch in those same areas for Wednesday, from noon to 8 pm, due to the potential for similarly hot, dry, and gusty conditions. By Thursday, greater moisture over the area with scattered showers and storms are expected to alleviate this fire danger. && .HYDROLOGY... Issued at 252 PM MDT Mon Aug 23 2021 Low chance of flash flooding through this evening, with decent storm motion and limited storm coverage. Nil on Tuesday with no thunderstorms forecast. Tuesday will be dry and clear, then isolated showers Wednesday will bring a very low threat of flooding. Greater moisture Thursday will allow scattered showers and increase the threat of burn area flash flooding, with localized heavy rain possible though storms are expected to be moving more quickly. The threat should remain limited. Precipitation should decrease in coverage and intensity again for the weekend. && .BOU WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Tuesday afternoon through Tuesday evening for COZ211-213. Fire Weather Watch from Wednesday afternoon through Wednesday evening for COZ211-213. && $$ UPDATE...Gimmestad SHORT TERM...Cooper LONG TERM...EJD AVIATION...Gimmestad FIRE WEATHER...Cooper HYDROLOGY...Cooper/EJD
Area Forecast Discussion...Updated
National Weather Service Billings MT
849 PM MDT Mon Aug 23 2021 .UPDATE... Tweaked the winds this evening with the front coming through the area. It looks like the main front is about through Billings as of 830p. There have been some showers and thunderstorms that have developed mainly from Wheatland County to northern Rosebud County with this front, but most have been quick to develop and then dissipate. Have kept the broad bushed slight chance PoPs across the area. Reimer && .DISCUSSION... Tonight through Wednesday... Cold front was just through KTFX at 18Z and was progged to move into the NW corner of the forecast area by 00Z tonight. HREF focuses on the SE for isolated thunderstorms from 22Z into the evening, and showed possible strong winds with the storms. RAP soundings showed inverted-v`s across most of the area. SREF had possible dry thunderstorms SE this afternoon. Kept slight chance PoPs across the area this evening due to energy in SW flow aloft, lift from the front and the soundings. Models bring front through KBIL around 03Z, and through the entire area by 09Z. Front will usher in cold advection and there will be a tight pressure gradient. Front will also be accompanied by decent pressure rises. As a result, expect windy conditions with N to NW gusts around 30 mph behind the front. Winds will drive smoke and haze out of the area. Went above NBM winds which were not strong enough. Temps will fall into the 40s and 50s behind the front. Upper trough crosses the area on Tuesday and cold advection continues until winds turn easterly late in the day. Highs will mainly be in the lower 70s. Expect gusty winds over the E half of the area. Humidities will range from the mid 20s to 40 percent. Few showers and storms are possible over the southern mountains. Anticyclonic flow aloft moves over the area Tue. night and continues on Wednesday. Warm front pushes N into the eastern part of the area on Wed. ahead of a surface low over WY. So had low PoPs late Tue. night/Wed. morning with the warm front in the E, and PoPs over the W in the afternoon due to upslope flow and energy approaching ahead of next trough. E winds will be gusty over the E on Wednesday and temps will reach the mid 70s to mid 80s. Only lower RH`s were in and near Sheridan County. Trough continues approaching Wed. night and warm front remains over the E with a low-level jet. PWAT`s also increase with the EC suggesting values around 1 inch. SREF had 500-1000 j/kg MLCAPE over the SE Wed. night with fairly strong shear across the area. Had PoPs over much of the area Wed. evening with precipitation shifting N and E overnight. Currently, SPC has a marginal risk over the E Wed. and Wed. night, so will need to keep an eye on this period for strong storms. Arthur Thursday through Monday... Unsettled conditions can be expected through the extended forecast. Large upper trough is progged to move through the region on Thursday bringing shower and thunderstorm chances. Southeasterly flow out ahead of the trough looks to transport moisture and instability into the east, where there is potential for some stronger storms. Shower and thunderstorm chances look to linger for Friday as cyclonic flow remains over the area. Yet another disturbance looks to drop through the region over the weekend bringing additional precipitation chances and slightly cooler temperatures. Weak ridging builds back over the area for Monday bringing drier and warmer conditions. Generally below normal temperatures are forecast through Monday with most places seeing highs in the 70s. A few locations could nudge above 80 degrees Thursday ahead of the upper trough, and again on Monday. Low temperatures in the 40s and 50s are forecast most nights. STP && .AVIATION... VFR conditions will prevail. Slant visibility may be reduced from smoke. A cold front will continue to move southeast this evening into the overnight hours, switching winds to the north with surface winds to 35 kts. Isolated showers and thunderstorms remain associated with the front will continue through around 06Z. Breezy winds will continue into the early morning hours. Carrothers/Reimer && .PRELIMINARY POINT TEMP/POPS... Tue Wed Thu Fri Sat Sun Mon ----------------------------------------------------------- BIL 051/071 049/078 053/079 052/077 051/073 049/072 049/082 20/U 11/B 24/T 53/T 34/T 21/B 00/U LVM 043/073 044/078 049/077 047/075 045/072 044/073 046/083 20/U 12/T 34/T 33/T 33/T 21/B 00/U HDN 050/072 049/083 051/080 050/078 049/076 047/072 047/083 20/U 11/U 23/T 53/T 34/T 21/B 00/U MLS 055/072 049/081 056/079 054/077 052/074 051/071 051/079 20/U 12/W 43/T 63/T 34/T 32/W 10/U 4BQ 056/073 050/084 057/083 054/079 052/077 051/070 050/079 20/U 21/U 33/T 53/T 34/T 32/W 10/U BHK 054/074 046/078 054/077 053/078 051/076 050/072 049/079 20/U 12/W 54/T 64/T 44/T 42/W 10/U SHR 049/073 046/085 050/081 048/079 047/076 045/071 046/082 21/U 11/U 22/T 42/T 33/T 31/U 10/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$
Area Forecast Discussion
National Weather Service Duluth MN
624 PM CDT Mon Aug 23 2021 .DISCUSSION...(This evening through Sunday) Issued at 225 PM CDT Mon Aug 23 2021 Summary: Today will continue to be warm, windy and dry before a much needed change to a wetter pattern with temperatures closer to normal through the remainder of the week. Warm, windy and dry is the main story today. Winds have been mainly out of the west gusting at times to near 25mph with minimum RH values near 30 percent from the Brainerd Lakes region northeastward to the Arrowhead. This will continue the Near Critical Fire Weather Conditions for NE MN. The next chance of precipitation comes overnight tonight into Tuesday morning. A warm front to our south from northeastern Montana to southeastern South Dakota will begin to move northward and develop elevated convection over eastern Dakotas. Bulk shear of 40 knots parallel to the front will allow the convection to continue to move eastward in a linear form. As the warm front moves northward, this will set up the southern portion of our CWA in a waa regime with strong theta-e north of the warm front along with an EML above 700mb. Additionally, elevated lapse rates around 7-8C/km will be moving northward with the front. By 12Z the warm front will be from northeastern SD to extreme southern MN as a shortwave moves in from the SW overtop the warm front along with isentropic lift at 310-315K will provide enough lift to keep ongoing convection moving eastward along the instability axis. Due to what is mentioned above, SPC has the southern portion of our CWA in Marginal Risk. The question remains how long will the convection stay organized and will it move into a Mesoscale Convective Complex which would mean that there will be more of a wind threat than a hail threat. Some models are indicating that the shortwave will remain strong through the afternoon, but the LLJ will decrease substantially by 15Z. Should also state that model hodographs show a small chance of tornado development near 12Z, but quickly diminishes. The HRRR is bringing in additional convection after the main complex moves eastward. This appears that it could develop on a secondary shortwave that moves through but have little confidence in its development given that the previous complex could decrease instability. The next chance of precipitation comes in overnight Thursday into Friday morning. Some model data is showing higher precipitation amounts which will be a welcome sight for drought stricken northeastern MN. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 623 PM CDT Mon Aug 23 2021 An MVFR stratus deck continues to flow across the International Border impacting INL. These clouds are expected to persist through the early portions of the night before lifting further north. Overnight, fog has the potential to develop across northern MN primarily impacting HIB and possibly DLH. A challenging weather system is projected to move in from the west tomorrow morning bringing rains and possibly strong to severe thunderstorms across the region. Model guidance continues to waiver in timing and location so confidence is not high for the onset and duration. Additionally, depending on how the morning convection goes there is potential for a second dose in the afternoon and evening hours. && .MARINE... Issued at 423 PM CDT Mon Aug 23 2021 Winds will be mainly out of the southwest 10 to 15 knots with gusts to near 20 knots switching to the northwest around 10 knots later this evening. By Tuesday morning winds will be out of the northeast 10 to 15 knots with gusts to near 20 knots. Waves will be less than 2 feet. Showers and thunderstorms will develop overnight into Tuesday morning possibly reaching the lake by early afternoon. Strong winds and large hail is possible. && .PRELIMINARY POINT TEMPS/POPS... DLH 57 69 60 76 / 10 70 50 0 INL 49 75 54 71 / 0 70 50 20 BRD 59 79 58 75 / 40 70 30 0 HYR 57 76 60 79 / 20 70 50 10 ASX 57 75 61 80 / 10 60 50 10 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...None. && $$ DISCUSSION...KSE AVIATION...Britt MARINE...KSE
National Weather Service Eureka CA
417 PM PDT Mon Aug 23 2021 .SYNOPSIS...Seasonable temperatures and generally light winds will continue through Wednesday. The coast is expected to see areas of nightly marine stratus with afternoon clearing. Smoke is expected to remain near fires, flowing with daily diurnal winds. Later this week, a warming and drying trend is expected with marine stratus persisting. && .DISCUSSION...Visible satellite imagery shows coastal stratus lingering along the Mendocino coast and smoke from the active wildfires in Trinity and Siskiyou counties has pushed back northeast as light southwest wind aloft develops. The weak upper- level trough is bringing seasonably temperatures and is expected to continue through mid week. Inland areas will see temperatures topping out close to 90 each day in Mendocino and Lake counties with low to mid 80s farther north. Temperatures may trend a degree or two cooler each day as this trough deepens. This cooler air aloft will continue to keep the marine inversion weak and limit the coverage of marine stratus. Afternoon clearing remains likely each day. Winds will be breezy along the coast, but inland areas will generally see diurnal/terrain driven winds. Otherwise, a brief period of increasing winds is expected tomorrow by late afternoon/early evening with westerly to northwesterly flow as a weak low level trough moves through. Thursday high pressure starts to build in over the west coast warming temperatures and increasing winds over the coastal waters and on the immediate coast. Most inland areas are expected to see around 5 degrees of warming. The ensembles have come into better agreement on this. Friday and into the weekend there is more uncertainty of on how much warming is expected. Some of the ensemble clusters show an upper level trough dropping down over Idaho, while others continue to build the ridge in. The scenario with trough would keep temperatures cooler, but may also increase north to northeast winds and lower the RH. The ridge would warm temperatures and keep the stronger northerly winds more confined to the coast. The operational GFS, ECMWF, and CMC are all closer to the clusters dropping a trough into Idaho and they are starting to show some stronger NE winds Saturday morning in Del Norte county. MKK&ZVS && .AVIATION...Once again, stratus blanketed the coastal waters and adjacent land areas this morning. These clouds eroded quickly over land, but held until around midday for portions of the N Coast. These clouds are now gone N of Cape Mendocino, but stratus continues S of the cape and along the Mendocino and S Humboldt coasts. The marine layer is presently about 2000 ft deep at the ACV profiler and a bit deeper to the S at the Bodega Bay profiler. The marine layer N of the cape is forecast to become even shallower later tonight and Tuesday, and the low-level inversion is forecast to weaken. As a result, low clouds which re-develop along the N Coast may clear more quickly Tuesday morning. Low clouds briefly advected N up the Russian River Valley to KUKI this morning. The latest HRRR guidance suggests this may occur again Tuesday morning. Winds will be generally light, with some gusts near 20 kt at KCEC and KUKI into the early evening. /SEC && .MARINE...Northerly winds will continue through the period. There may be enough of a lull to drop headlines for the N outer waters by Wednesday, but winds are forecast to increase once again later in the work week, with gale force gusts likely by Friday afternoon. For the update, have hoisted a Hazardous Seas Warning for the N outer waters from this evening thru Tuesday afternoon to account for an increase in wind over the extreme N portion of the zone and northward. Have also extended the Small Craft Advisory for the S outer waters thru midday Thursday. /SEC && .FIRE WEATHER...The upper level trough will remain over the west coast through about Wednesday. The trough may deepen slightly and this could cool temperatures by a degree or so each day. The afternoon RH and overnight recoveries may diminish slightly as well. Transport winds remain light, but are generally pushing the smoke off to the northeast. Most of our areas will remain free from the thicker smoke aside from areas of Trinity county to the northeast of the fires. Surface winds will generally be light and terrain driven. Tuesday, a brief period of increasing winds is expected late afternoon/early evening with westerly to northwesterly flow as a weak low level trough moves through. More wind prone areas could sees gusts up to 25 mph. Thursday models continue to come into better agreement on high pressure starting to build in and bringing a warming and drying trend. There is decent agreement in the ensembles that this warming and drying trend will continue on Friday. For the weekend the ensembles are starting to show a couple clusters. One brings warming temperatures as ridge builds in. This would like keep winds mainly terrain driven. The other two clusters show a trough dropping into ID/MT and either slowing the warming bringing some cooling. This would also bring some stronger offshore winds and drier air. MKK&ZVS && .EKA WATCHES/WARNINGS/ADVISORIES... CA...None. NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 4 PM PDT Tuesday for PZZ450. Small Craft Advisory until 6 PM PDT this evening for PZZ470. Hazardous Seas Warning until noon PDT Tuesday for PZZ470. Small Craft Advisory until noon PDT Thursday for PZZ475. && $$ Visit us at Follow us on Facebook and Twitter at: For forecast zone information see the forecast zone map online:
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
908 PM CDT Mon Aug 23 2021 .UPDATE... 908 PM CDT Few minor tweaks made to going forecast this evening, mainly to raise overnight min temps slightly. Thunderstorm forecast for later tonight remains somewhat low confidence with CAM guidance still offering diverging solutions on evolution of elevated convection across the region. Chance pops across especially far northern still appear reasonable at this point though, and no changes made. Early evening surface analysis depicts a west-east oriented surface trough, stretching roughly along the I-80 corridor across IA and northern IL. Mid-70s surface dew point temps were pooled along and south of this boundary, with a northward drift noted over the past few hours. Water vapor imagery indicates a mid- level short wave trough propagating east-northeastward across the mid-Missouri River Valley of eastern NE/western IA. This feature will continue to translate east-northeastward tonight, reaching WI and northern IL toward 10Z/4 am. Pooled low-level moisture and the advection of steep mid-level lapse rates (OAX 00Z sounding indicates deep layer of 7+ C/km lapse rates) would appear to support the development of substantial elevated instability across the region into early Tuesday morning, with the caveat being sufficient moistening of a layer in the 800-850 mb range to allow for a forced parcel to break the cap. 00Z upstream RAOBs don`t depict this, though RAP analysis does depict a narrow axis of H8 dew points along the I-80 corridor from NE across IA. CAM guidance has been somewhat split on the extent and location of elevated convection development overnight, with the HRRR decidedly on the dry side and the 18Z 3 km NAM maintaining that models earlier trend of activity developing across northern IA and spreading into northwest/northern IL toward Tuesday morning. Quick glance at the newly arriving 00Z 3 km WRF still brings convection into the IL/WI state line region early Tuesday, though not as extensively and perhaps too slowly (per short wave timing). Basically, the potential for thunderstorms remains across northern IL late tonight/early Tuesday remains a possibility, though of somewhat low confidence. Therefore hesitant to change our current 30-40 percent pops much, with some potential that guidance/RAOB network is not handling moisture fields 100 percent correctly. Otherwise, did raise overnight mins slightly tonight especially across the southern cwa where aforementioned higher dew points will likely keep temps from falling off too much. Can`t rule out some patchy fog in a few spots with moist low levels, though 10+ kt flow atop the boundary layer should work against this somewhat. Ratzer && .SHORT TERM... 330 PM CDT Main concern beyond the near term is later tonight into Tuesday morning for the potential of at least scattered storms to develop overhead northern Illinois and gradually overspread points south and east. This would have a heavy downpour and localized flooding threat, especially if the convective footprint is larger. Depending on how long into Tuesday the convection lingers along with associated debris cloud cover, the potential exists for parts of the area to reach or exceed 105+ degree heat index criteria for Heat Advisory. We`ve been tracking a convectively modified disturbance from eastern Colorado that has reached the Missouri River vicinity near the NE/IA border. After the wave responsible for the northwest Illinois convection this afternoon exits, should have at least a few hours of subsidence in the evening. Later tonight, a plume of even steeper mid-level lapse rates will be advecting eastward as the short-wave drifts overhead. Modest LLJ but decent isentropic upglide on the 310K surface in response to the wave should work to erode MUCIN assuming there`s enough moisture in the 850-800 mb layer. While there`s variance in the details, much of the guidance does indicate enough saturation to tap into large MUCAPE reservoir. HRRR has been a notable dry outlier, though may be starting to see a change on the 18z run. Conceptually do favor the idea of convective initiation overhead in the pre-dawn hours, though lower confidence in exact timing and coverage. Given this, opted to largely forecast continuity though with a modest increase in PoP magnitude into the 40%ish range. As alluded to in intro, high column moisture with PWAT pushing 1.7" or more would support torrential downpours especially in robust convection. Slow storm motions would yield efficient rain producers and will need to watch for training or backbuilding if convective footprint is large enough. Lots of unanswerable questions on how this all evolves through the morning, so needless to say observational trends will be monitored closely. Given the above uncertainty and overall expectation that convection will occur farther east than it did earlier today, confidence is rather low in the temperature and heat index forecast. Convective uncertainty aside, the air mass with 850 mb temps in the lower 20s Celsius amidst dew points into the mid and even locally upper 70s would support heat indices near or above 105F if temps reach the mid 90s. Neighboring offices to the south and west have gone ahead and issued a Heat Advisory, but decision here was to hold off given the potential for convection and lingering clouds to have a substantial effect on temps. Convective trends beyond the morning are also uncertain - other than thinking that there will be a lull after morning storms diminish (assuming they do). We`ll have to watch for a semi-organized cluster of convection to approach from the west and northwest Tuesday evening and night. Have the highest PoPs overnight (30-40%) focused I-80 and north for this potential. Castro && .LONG TERM... 301 PM CDT Wednesday through Monday... A persistent pattern of heat and humidity may finally break early next week, but until then the mid to upper 90s heat indices will linger into the weekend, with actual highs in the upper 80s to lower 90s. Relatively weak southerly flow for most of the period may allow for lakeside cooling on some afternoons. The best bet for significant onshore cooling winds comes on Thursday following the passage of a weak frontal zone late Wednesday. In this type of pattern with an upper ridge to our south and quasi- zonal flow across the northern CONUS, heat headlines and afternoon convection are usually the two competing questions. This certainly will be true on Wednesday ahead of the approaching frontal zone. The latest guidance suggests we might be very close to but just below thresholds for a heat advisory, and additional uncertainty is provided by the influence of possible convection along the surface boundary. Precip chances will remain elevated, though for now still in the chance category, as the front pushes into the area late Wednesday, stalls Wednesday night, then begins to lift back north on Thursday as a warm front extending eastward from a surface low moving from the Southern Plains toward Lake Superior. North of this front on Thursday is also where the cooler easterly flow off the lake would develop. By late in the week and into the weekend, heat and humidity persist but precip chances presently look lower with the lack of additional shortwaves or low-level boundaries to provide a focus for lift. Models then suggest a more significant cold front will move through late Sunday and usher in cooler conditions to start next week, but there is considerable uncertainty that far out in such a weakly forced pattern. Lenning && .AVIATION... For the 00Z TAFs... 630 PM...Forecast concerns include... Chance of thunderstorms Tuesday morning. Chance of thunderstorms Tuesday afternoon/evening. Chance for fog early Tuesday morning. Possible gusty southerly winds Tuesday. Showers and isolated thunderstorms earlier this afternoon have dissipated and not expecting any additional activity this evening. Focus shifts to the predawn hours Tuesday morning when the next chance for thunderstorms will arrive but confidence remains low. This time period is currently covered by prob mention and this looks fine for now. Will need to assess thunder potential with the 03z update this evening. There is another chance of thunderstorms Tuesday afternoon into Tuesday evening and these will likely be dependent on morning activity though there seems to be a bit better signal for activity Tuesday afternoon/evening. Opted for just prob mention for now. Any thunderstorms that do form, at either time period, will have the potential to produce very heavy rain and gusty/erratic winds. There will be some fog potential again overnight into early Tuesday morning, mainly west and southwest of the Chicago terminals. Already have lower vis mentioned associated with the thunder potential but some prevailing mvfr vis may be needed, especially at rfd Tuesday morning. Some patchy dense ground fog may also develop in the usual locations. Winds will remain southerly under 10kts tonight, with some southeast directions possible this evening. Outside of any thunderstorms or their outflow, generally southerly winds are expected Tuesday and there is some potential for wind speeds to increase into the 10-15kt range with some higher gusts. These will be dependent on precip timing/location but medium confidence to increase wind speeds for Tuesday. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Marquette MI
624 PM EDT Mon Aug 23 2021 .SHORT TERM...(This evening through Tuesday) Issued at 351 PM EDT MON AUG 23 2021 Water vapor imagery and RAP analysis show a slowly-weakening shortwave continuing to lift ne through northern Ontario this afternoon. Over the Upper Great Lakes, mid-level ridging is fcst to continue building into the region this afternoon and evening. Higher dew points in the lower to mid 60s combined with steep low-level lapse rates of 7C or greater has resulted in an expansive cu field over much of the western half of the U.P this afternoon. Afternoon temps have risen generally in the lower to mid 80s across much of the area with cooler readings in the mid 70s along the Lake Mi shoreline. Big question late this afternoon/early evening: is will convection initiate along weak sfc trough/convergence area over the nw U.P.? A few of the CAMS still try to get some convection going in this area, but looking at the fcst soundings mid-levels are very dry with even some CIN noted, so I would doubt we`ll see showers forming. Kept fcst dry, and expect diurnal cu to dissipate after sunset in the west. Models indicate a shortwave late tonight could ride along frontal boundary/instability gradient resulting in a possible MCS over central/southern WI although it looks like any convection from this system would stay south of the U.P. Expect min temps in the 50s to lower 60s tonight, coolest over the western interior. Given higher dew points and light winds, I guess it wouldn`t be out the question there could be some patchy ground fog over the western interior, but with low confidence decided not not to put it in the fcst grids. Model agreement/timing is poor for potential convection on Tuesday although there is a signal with several of the CAMs that convection forming over central MN later tonight could congeal into an MCS and then track se or ese as a linear convective system across either northern or central WI on Tuesday following the better instability gradient along the sfc-850 mb warm front. Generally bring chc PoP for showers/t-storms into mainly western and south central portions of the cwa Tue afternoon where convection on northern end of MCS could brush these areas. Expect max temps in the lower to 80s over much of the interior and in the mid to upper 70s near the Great Lakes shores. .LONG TERM...(Tuesday night through Monday) Issued at 423 PM EDT MON AUG 23 2021 We have a tricky forecast to start the extended period, as model guidance is showing high divergence as to when, where, and if convection will develop over the U.P. Tuesday night. As a sfc low in the Northern Plains lifts northeast towards northern Ontario (ON) Tuesday night, expect better synoptic forcing to remain northwest of us. Meanwhile, some CAMs still show an MCS developing mainly just south of the border in WI (such as the NAM4km and HiRESW-Fv3) during the overnight hours. The Euro, NAM12km, and RAP13 still show precipitation over the U.P. Tuesday night, so there is a chance for some precip still, though it doesn`t look as favorable given the lack forcing and the better instability being south of us; if an MCS does develop in WI, I would expect chances for precip over the U.P. to decrease Tuesday night. Therefore, I tried to keep only a chance of showers and thunderstorms across the area, although I did adjust to my neighbors to the south who had a much higher chance of seeing precip in their areas (as the southern U.P. does have a better chance of seeing something Tuesday night). Don`t think severe wx should be a threat Tuesday night; again, the better instability should be south in WI, and the better forcing should be closer to NE MN, even though the 0-6 km bulk shear looks modest (30 to 40 knots). As the low in northern ON combines with another low and shifts east towards Quebec, expect a cold front to move through Wednesday. This front should keep the highest temperatures confined to the south central, where the front will more than likely have the least impact given the jet stream should be north of Lake Superior then. As this front passes through Wednesday, showers and thunderstorms should be confined to the east; again, no severe weather is expected due to most of the precip being done by noon, and the turning of the winds with height is expect to not be as strong (even though the forcing is better). Expect cooler conditions Thursday as a high pressure over northern ON should move cooler Canadian air over the U.P.. Meanwhile, a pressure gradient aloft should begin moving slowly east over us and tighten late this week as a troughing pattern sets up over the Northern Plains. This should allow multiple shortwaves to cross over Upper MI this weekend. Given that ensembles show PWATs in the 90th percentile for these shortwaves (and the forcing doesn`t seem too strong also, which should help with rainfall production), would not be surprised to see a soaking rainfall event this weekend. Global models also are showing some pretty decent winds with the shortwave activity this weekend. Wouldn`t be surprised if we had some breezy conditions, particularly in the Keweenaw. Eventually, we should have a cold front move through next Sunday night into Monday as the troughing pattern moves east. This should bring an end to the precip, and we should also see temperatures become `cooler` and closer to normal next Monday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 623 PM EDT MON AUG 23 2021 VFR conditions should prevail thru this fcst period at all sites. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 351 PM EDT MON AUG 23 2021 Expect winds to remain generally under 20kt across Lake Superior thru Wed. During Thu and Fri, pres gradient will tighten btwn high pres moving from northern Ontario to Quebec and a low pres trof lifting into the Upper Great Lakes. As a result, expect e to ne winds to gust to at least 20-25kt over western Lake Superior on Thu with e to se wind gusts to at least 20-25kt spreading to eastern Lake Superior Thu night into Sat. Would not be surprised to see gusts to around 30kt for a time as well. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...TAP AVIATION...07 MARINE...Voss
Area Forecast Discussion
National Weather Service Omaha/Valley NE
Issued by National Weather Service Hastings NE 535 PM CDT Mon Aug 23 2021 .DISCUSSION... Issued at 530 PM CDT Mon Aug 23 2021 Hot and humid conditions, with occasional/conditional thunderstorm chances, are the main forecast concerns. Hot and humid conditions have developed across much of the CWA this aftn, esp areas along and S of the Platte River. A weak disturbance (as seen on latest WV imagery) ejecting from NE CO into central NE has resulted in iso to widely scat elevated/weak convection for areas around BVN to OFK. Short-term hi-res guidance has not handled this well, thus far. Exactly how this activity evolves is low confidence, but gut feeling is that it will remain fairly weak/elevated as it continues to move NE over next few hrs. Sfc based instability is strong, but MLCINH remains fairly high at 50-100 J/kg per latest SPC mesoanalysis, further supporting the idea this activity will struggle to become sfc based. Appears greater potential for sfc based t-storm development, and associated svr threats, will be closer to NE/SD border, within zone of greater low level wind/moisture convergence, and on edge of stronger mid level capping. Tstms have blossomed over S SD last hr or two, and this activity is forecast to move E/SE and may move into far NW portions of CWA towards late eve. As such, this is where a Slight Risk for severe tstms resides, with large hail and damaging winds the main concerns. Current thinking is that 18Z NAMNest is overdone, and HRRR may be have focused 20-30 PoPs mainly NW of LNK/OMA. The main forecast change for Tue was to issue a Heat Advisory for S half or so of CWA for peak heat indices near 105F. Don`t think there will be significant AM convection or clds, which should allow for rapid warming through the AM. Guidance indicates pooling moisture ahead of a dev sfc low along NE/KS border by aftn, which combined with high temps in the upper 90s/near 100 should lead to heat indices near 105F. Add in evapotranspiration from mature crops and it could be even higher in spots. Winds over central/western ares are lighter. So even though heat indices may be a touch lower, it may actually feel as bad or worse in these areas. Will let mid shift crew get a look at a couple more model runs, but wouldn`t be surprised if current advisory is expanded NW a county or two. The next concern revolves around yet another chc for tstms during the aftn/eve hrs Tue. A shortwave tracking across the N Plains will force a cold front into central NE by late aftn. Intense heating along/ahead of the front and impingement onto NW fringes of low level moisture plume will probably support iso to scat convection in the 21Z to 00Z time frame, probably over NW portions of CWA or just W of there. Upper level support is not great, and mid temps are quite warm at 14-16C, but magnitude of CAPE/shear support a non- zero chc for strong/severe storms. Expect a gradual eastward movement thru the eve. Intensifying low level jet Tue eve could foster upscale growth during late eve, but magnitude of mid level temps casts some uncertainty on size/scope of any potential MCS. IF an MCS develops, will have to watch for locally hvy rn given PWATs near 1.75" and perhaps some subtle training. Again though, confidence on this is very low attm given high model spread (e.g. 18Z HRRR much more active than 18Z NAM Nest.) The rest of the forecast remains on the warm/hot and humid side, but probably not as bad as Tue. Some areas along KS/NE state line could see heat indices near 100F again Wed, and maybe even Thu, but current thinking is that we`ll stay below Heat Advisory thresholds. There are mentionable PoPs (15 percent chc or greater) nearly every period through the extended, but this probably sounds worse/wetter than it will be. This is fairly common for late summer. Appears time frame of best chcs will be Wed night into Thu, esp. for N half/third of CWA, then areawide Sat-Sat night. Won`t go into much more details beyond that as predictability is low. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 619 AM CDT Mon Aug 23 2021 Expect mainly VFR conditions the next 24 hours. There are some MVFR ceilings in the far northern parts of northeast NE north of KOFK and some patchy areas of fog, but we don`t expect these to have much of an impact at the TAF sites. Could see some scattered storms in parts of northeast NE today and mentioned a PROB30 group at KOFK for 21z-24z. Otherwise chances at KOMA and KLNK are not zero but too low to include in TAFs. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Heat Advisory from noon to 8 PM CDT Tuesday for NEZ051>053- 065>068-078-088>093. IA...Heat Advisory from noon to 8 PM CDT Tuesday for IAZ069-079-080- 090-091. && $$ DISCUSSION...Thies AVIATION...Miller
Area Forecast Discussion
National Weather Service Pendleton OR
858 PM PDT Mon Aug 23 2021 .UPDATE...Based on surface observations and satellite imagery, light winds and mostly clear skies are present across the forecast area. This should allow efficient radiational cooling tonight. As such, have lowered tomorrow morning`s minimum temperatures in a few spots, mainly high valley locations. Additionally, updated haze and smoke based on the latest HRRR Smoke run. Otherwise, no major changes to the forecast. 86 && .PREV DISCUSSION... /issued 425 PM PDT Mon Aug 23 2021/ SHORT TERM... Tonight through Wednesday night...An area of low pressure was located over British Columbia with weak troughing over northeast Washington. However, further south, the flow is more zonal. Weak ridging moves in overnight and into Tuesday before a trough off the Pacific Northwest coast moves onshore Wednesday into Wednesday night. With a mainly clear sky and light winds expected tonight, it will be a chilly night in most locations, the coolest night we have had in some time. Most areas will be in the low to mid 40s with the mountains in the 30s, and some mountain locations close to or below freezing. Temperatures on Tuesday will be warmer than today, as the ridging moves in, and many locations, will be close to 80 degrees, with the Basin in the low to mid 80s. Temperatures on Wednesday will be a degree or two warmer than on Tuesday. overnight lows will also warm with most locations in the 40s and 50s. As far as sensible weather, with the trough moving in on Wednesday, and several shortwaves, albeit weak ones, moving though it on Wednesday, there is a small chance of showers or thunderstorms mainly over the mountains. However, none of the guidance is particularly excited about this potential at this time and since the shortwaves aren`t particularly strong have opted to leave the forecast dry for now. The HREF ensemble guidance places a couple of enhanced showers in central Oregon Wednesday night as does the ECMWF, while the GFS and NAM are dry. So it is possible showers and or thunderstorms may need to be added for a portion of the area at a later time. LONG TERM... Thursday through Monday...To begin the long term, an upper level trough will be departing the region, promoting cooler weather and westerly breezy winds. High temperatures look to remain below average across much of the forecast region with 70`s to mid 80`s expected Thursday through Saturday. The breeziest winds should remain the usual locations of the Columbia Gorge and the Kittitas Valley. Into Sunday is where the greatest discrepancies lies in model potential as high pressure ridging is expected to move in through Monday and bring a warming trend for the region. Ensemble clusters show that the strength of the ridge is not agreed upon, but none of the models are stout with it. Rather, only a few degrees of temperatures difference are expected, as we are getting far enough along in the year that major heat events will become more and more unlikely. For Sunday and Monday, current highs look to range in the 80`s, peaking in the low 90`s for the Columbia Gorge and Columbia Basins. With all of this fair weather finally expected for our region, a reprieve in the form of precipitation is not expected. Models continue to keep us dry with only a chance at showers expected for the WA Cascade Crests on Thursday. Goatley/87 AVIATION...00Z TAFS...VFR conditions should prevail over the next 24 hours. Some patchy smoke may drift near YKM/RDM/BDN but is not expected to be as dense as previous days. Winds will generally be under 10kts. 91 && .PRELIMINARY POINT TEMPS/POPS... PDT 42 80 49 82 / 0 0 0 0 ALW 47 83 55 84 / 0 0 0 0 PSC 47 84 51 85 / 0 0 0 0 YKM 42 82 49 85 / 0 0 0 0 HRI 45 84 49 85 / 0 0 0 0 ELN 45 82 49 84 / 0 0 0 0 RDM 34 79 42 80 / 0 0 0 0 LGD 39 79 45 80 / 0 0 0 0 GCD 41 82 51 82 / 0 0 0 0 DLS 50 86 54 84 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...86 LONG TERM....87 AVIATION...91
Area Forecast Discussion
National Weather Service Portland OR
230 PM PDT Mon Aug 23 2021 .SYNOPSIS...A very broad, weak upper level trough over the Pacific Northwest will maintain near average temperatures through most of the upcoming work week. Odds favor a brief return to hotter temperatures late in the weekend. && .SHORT TERM...Tonight through Thursday...Water vapor satellite imagery this afternoon reveals a broad shortwave trough over the Pacific Northwest. As a lobe of this shortwave trough slides southeastward across central Washington this evening, 850mb winds will turn out of the east to northeast. This will limit morning cloud cover across northwest Oregon and southwest Washington Tuesday and result in temperatures warming well up into the 80s Tuesday for inland valleys. The HRRR smoke model does suggest smoke from the Schneider Springs fire in Yakima County, WA will shift into southwest Washington and the northern Willamette Valley Tuesday. While this may result in the sky being a little less blue than normal, not expecting this smoke to bring noticeable impacts. This is primarily based on the fact smoke from the fire today is very limited per satellite imagery. Models are then in good agreement a piece of the shortwave trough currently over the Gulf of Alaska will slide southeastward into the upper level trough currently sitting over the Pacific Northwest. This will result in the upper level trough sharpening a bit and the pressure gradient gradient force becoming more oriented from southwest to northeast across the area. High resolution models are not terribly keen on the idea of extensive marine clouds so have kept sky cover closer to NBM guidance. This is partly due to the fact that marine stratus is currently limited offshore and will likely be so to begin the day tomorrow. As a result, it may not have enough time to congeal despite the pattern looking favorable for a fairly extensive marine cloud layer across northwest Oregon and southwest Washington. Either way, with the loss of easterly winds at 850mb and a return to a more marine air spreading into the area, temperatures should drop several degrees on Wednesday relative to Tuesday. Ensemble and model guidance suggests a weakening front will then drop southeastward towards southwest Washington and northwest Oregon Wednesday night into Thursday. Virga and higher level clouds will likely spread across the area late Wednesday. However, a better chance for rain to reach the ground arrives late Wednesday night into Thursday as the majority of raw ensemble guidance available suggests light rain will move into our northern coastal zones. PoPs are still only the slight chance to chance category at this point given some uncertainty in the exact timing of precipitation. Nonetheless, think it`s safe to say some light rain and drizzle is likely along our northern coastal areas some time late Wednesday night or Thursday. The majority of ensemble guidance weakens the front enough that measurable rainfall does not reach the Portland metro, let alone places like Salem or Eugene or our wildfires in the Cascades. Nonetheless, another push of cooler marine air into the region should lower temperatures back below average for the date on Thursday. /Neuman && .LONG TERM...Thursday night through Monday...Models and their ensembles are in good agreement a low amplitude shortwave trough will linger over the Pacific Northwest through Saturday. However, the degree to which shortwave ridging develops over the northeast Pacific and its proximity to the Pacific Northwest remains in question as we move into late Saturday and Sunday. The probability the area warms and dries out Sunday has gone up slightly when compared to this time yesterday. NBM guidance now suggests the probability of hitting 90F on Sunday is now 50% for Portland and nearly 80% for Eugene. WPC cluster analysis and a look at raw ensemble output does suggest the odds of those hot and drier conditions lasting into early next week is relatively low as another low amplitude shortwave trough settles into the Pacific Northwest. For example, NBM guidance drops the probability of 90F temperatures lasting into even Monday at less than 10% for Portland and around 20% for Eugene. A bit beyond the scope of this forecast, but there is very little sign in the ensemble guidance of a major fall-like storm system bringing a much needed widespread soaking rain event next week. /Neuman && .AVIATION...00Z TAF UPDATE: Northwest flow aloft continues over the area through Tue. Stratocumulus clouds over southwest Washington and northwest Oregon slowly diminishing during the afternoon. As of 2030Z still areas of cigs around 045, but expect these cigs to dissipate as the low-level flow becomes north to northeast this evening and tonight. The 12Z high-resolution cloud cover model suggests minimal marine stratus Tue morning, even along the coast. Expect VFR to prevail across the area through the 18Z TAF period. Cannot rule out isolated IFR or lower conditions along the coast Tue morning, but confidence is low. For detailed regional Pac NW aviation weather information, go online to: KPDX AND APPROACHES...VFR through the 00Z TAF period. However, scattered clouds 040-050 will continue through early evening. Northwest to North wind 10 kt or less, but gusts to 15 kt through the evening. Weishaar && .MARINE...Strong surface high pressure remains over the eastern Pacific through Tuesday. Thermally-induced low pressure along the south Oregon coast will result in gusty wind over PZZ255 and PZZ275. Will maintain the current small craft advisory through 06Z Tue. Latest model guidance shows wind speeds decreasing overnight. Not expecting small craft advisory conditions Tue as guidance suggests 15-20 kt boundary layer wind speeds. Surface gradients weaken Tue night and Wed as another upper trough moves over the waters. This will deepen the marine layer and result in lighter west wind. Small craft advisory level wind speeds may return south of Cascade Head Fri as gradients tighten and thermally-induced surface low pressure strengthens over the south Oregon waters. Meanwhile, west-northwest swell around 5 ft at 8 sec will gradually subside through Tuesday, leaving primarily wind-driven seas by midweek. The next swell train of significance arrives behind a decaying cold front Thu night/Fri, but latest wave guidance suggests seas will remain well below 10 ft through the upcoming weekend. Weishaar && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for coastal waters from Cascade Head OR to Florence OR out 60 NM. && $$
forecast discussion above for more details. I do want to note
that dense smoke will have impacts on predicted temperatures
(cooler daytimes). But for fire weather it is also having an impact by limiting how strong the afternoon diurnal winds get by reducing the Sierra to Nevada thermal gradient and vertical mixing. So that could be an influence on the extent of near- critical conditions Wednesday afternoon. -Chris && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service San Diego CA
134 PM PDT Mon Aug 23 2021 .SYNOPSIS... Low clouds will continue the next few nights, but become increasingly shallower and confined to coastal areas as high pressure slowly expands. A gradual warming trend will bring us near-normal temperatures by Wednesday, and above-normal temperatures thereafter. Increasing smoke aloft may bring hazy skies over the next couple of days, with some higher concentrations near the surface possible as well for the mountains and deserts. There are some indications of thunderstorm activity returning to our mountains/deserts as early as Sunday, but uncertainty remains in the pattern that far out. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Afternoon update... Forecast temperatures were raised slightly for mid to late week. With moderate to high heat risk now expected for the lower deserts, an Excessive Heat Watch was issued Wed-Fri for the Coachella Valley and San Diego County deserts. No other significant changes made today. See below for previous discussion. .SHORT TERM (Today through Wednesday)... This morning`s satellite imagery exhibits little change from yesterday, with an uncharacteristically deep marine layer (for August) extending to the foothills. Signs of the rising heights are evident though, with the thinner low clouds unable to produce any measurable precipitation this morning save for two isolated sites, and with a lesser inland extent in the Inland Empire. Thus, look for slightly earlier clearing compared to yesterday (albeit still slow). Smoke aloft is also faintly visible over SoCal and the California Bight, with much more abundant smoke impacting northern California and the Great Basin. With better clearing and higher pressure, temperatures will be a few degrees warmer today, though highs will nonetheless remain below normal across the region. Over the next couple of days, we`ll stay wedged between a troughing pattern to our north, and high pressure to our east, with prevailing southwest flow aloft. The primary change will be the gradual westward expansion of the high pressure, which will result in a steady warming trend that will return us to near- normal temperatures by Wednesday. Meanwhile, a shrinking marine layer will see low clouds reduce their footprint each night, becoming increasingly confined to coastal areas with a possibility of patchy fog by Wednesday morning. An additional factor to consider over the next few days will be the increased potential for both elevated and near-surface smoke. HRRR smoke products are consistent in showing an area of higher smoke concentrations - currently to our southwest - advecting northeast into southern California through the next 24-48 hours. Most of the smoke should remain aloft, with the main impact being slightly hazier skies, however the mountains and deserts could see a notable increase in near-surface smoke Tuesday as it mixes down. && .LONG TERM (Thursday through Monday)... 500 mb heights will continue to climb late in the work week, with 850 mb temperatures peaking near 29-30 C on Friday across southern California. As such, warmer than normal conditions will return, with highs around 100 F for the Inland Empire and High Desert, and 110-115 F in the Coachella Valley and San Diego County deserts, which translated into moderate Heat Risk for many interior locations. It`s likely that marine layer clouds will be minimal to nonexistent during this period. Differences in model guidance become more substantial for the weekend and into early next week, with mixed signals when it comes to the potential return of monsoonal activity. Higher pressure looks to become somewhat more centered over the Four Corners, with a corresponding increase in southeasterly flow near the surface. For a considerable portion of the ensembles, this is reflected in the form of higher PWAT values and indications of measurable precipitation for mountain/desert locations as early as Sunday, though with some uncertainty in timing. Of the GFS ENS members, approximately half show precipitation at Big Bear on Monday, although over 90% of them show precipitation at some point between Sunday and Tuesday. The EC ENS system is less bullish, however. && .AVIATION 232030Z...Coast/Valleys...Mostly clear skies with 6+ mile vis despite smoke aloft over the region this afternoon. BKN-OVC stratus will spread inland again tonight with onset mostly 03Z-07Z Tue at the coast and 06Z-11Z Tue in the valleys with bases 1500-2300 ft MSL and tops to 3000 ft MSL with higher terrain obscured and local vis below 3 miles in the valleys in fog. The valleys will mostly clear 15-17Z Tue, and the coast will mostly clear 16Z-18Z Tue. Mountains/Deserts...Mostly clear skies will prevail through Tue. Smoke aloft will reduce vis somewhat, but the vis will remain mostly 6+ miles. && .MARINE... No hazardous marine conditions through Saturday. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Watch from Wednesday morning through Friday evening for Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...NONE. && $$ PUBLIC...Rodriguez AVIATION/MARINE...Maxwell
Area Forecast Discussion
National Weather Service Tucson AZ
252 PM MST Mon Aug 23 2021 .SYNOPSIS...High pressure will bring hotter temperatures the second half of the week. A chance of thunderstorms today and Tuesday before storm chances wane into the weekend. Conditions are expected to be more favorable for thunderstorms early next week. && .DISCUSSION...We continue to see troughiness through the region northwest of our area with a strong ridge building across southern tier states. The subsequent southwesterly flow is on the dry side, however a narrow area of high H7 theta-e values from eastern Sonora into the AZ/NM border area is seeing some strong convection this afternoon. On our side of the border that has mainly been Cochise county with severe and flash flood threat. HRRR spreads some of that into Santa Cruz, Graham and Greenlee counties over the next few hours before typical diurnal trends knock things down by early to mid evening. Another chance of thunderstorms tomorrow afternoon before we fall back to well below average coverage with limited moisture and an unfavorable temperature profile the rest of the week. That will open the door for heat, with excessive heat levels possible Wed through Friday. Both NAEFS and ENS ensemble means are above the 99th climo percentile at 850-500mb Thursday. Beyond that, we`re seeing increasing likelihood that an active tropics will help push a deep surge into southern Arizona over the weekend. Next week is starting to look very interesting and potentially very wet. && .AVIATION...Valid through 25/00Z. Isolated SHRA/TSRA will develop east of the KTUS and KOLS this afternoon but a brief VCSH is not out of the question for KOLS through this evening. Better chances for SHRA/TSRA at the terminals will be on Tuesday afternoon between 21z-03z, potentially lasting through 07z at KOLS. FEW-SCT clouds are expected to develop at 8k- 12k feet this afternoon with decreasing coverage overnight. Winds will favor a westerly component this afternoon, remaining around 10 knots before decreasing this evening. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... A near to below normal monsoon pattern is expected through late this week. Isolated to scattered storms will be possible each afternoon primarily east and south of Tucson and over the higher elevations. An uptick in storm activity will be possible Friday into the weekend. Temps will remain above normal Tuesday through at least Friday with triple digit temps expected for much of the lower deserts. 20-foot winds will generally be less than 15 mph when not influenced by thunderstorms and RH values are expected to remain above critical thresholds. && .TWC WATCHES/WARNINGS/ADVISORIES... Excessive Heat Watch from Wednesday morning through Friday evening for AZZ501-502-504-505. && $$ Public...Meyer Aviation...Guillet Fire Weather....Guillet Visit us on Facebook...Twitter...YouTube...and at