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

Area Forecast Discussion
National Weather Service Bismarck ND
936 PM CDT Fri Aug 7 2020 .UPDATE... Issued at 933 PM CDT Fri Aug 7 2020 Updated to better cover current radar trends and linger pops in the north a little longer. KMBX radar shows a few storms developing near / north of Minot. The 00Z NAM NEST and latest HRRR suggest that activity should gradually move northeast and exit the forecast area around 05z. UPDATE Issued at 808 PM CDT Fri Aug 7 2020 Made a quick update to better reflect the ongoing convection. The line has decreased in coverage over the past hour, but the storms that remain continue to be strong to severe. Expect them to gradually weaken with the loss of daytime heating which is in line with the latest HRRR. UPDATE Issued at 637 PM CDT Fri Aug 7 2020 Late afternoon radar mosaic shows a line of storms has formed along the eastern moving boundary in central North Dakota. The CAMS have now generally caught on to this idea. Specifically, the HRRR suggests the storms will continue to move east for the next several hours before diminishing. UPDATE Issued at 405 PM CDT Fri Aug 7 2020 A line of increasingly agitated cumulus has developed from northern Dunn county through central Stark county. This cumulus field is placed along a line of modest convergence, though possibly aided by differential heating given the 10-15 degree difference in surface dew points from east to west of the line. While 12Z guidance had a fairly strong mid-level inversion in this area, the early afternoon NUCAPS sounding product indicated a substantially lesser cap in the area of the currently growing cumulus (MLCIN of -155 J/kg from the 12Z NAM and around -40 on the NUCAPS sounding). With current satellite trends (including increasing glaciation seen on GOES-East Day Cloud Phase RGB) indicating better confidence for convective initiation, an isolated severe threat will be possible. Very steep mid-level lapse rates of 8+ C/km on the NUCAPS sounding show ample instability aloft for hail production, though mitigated somewhat by just marginal effective deep layer shear of around 25 kts. The current mid-level height rise pattern contributes additional uncertainty in convective coverage, though clearly there is enough convergence for convective initiation attempts in the near-term. Given the formation of thunderstorms by this evening, severe hail and locally damaging wind gusts will be possible. && .SHORT TERM...(This afternoon through Saturday) Issued at 200 PM CDT Fri Aug 7 2020 The MCV that moved across southern North Dakota this morning has now moved into the Red River valley, and any afternoon thunderstorms that develop from its remnants will remain east of our forecast area. At the mid levels, we will see height rises and capping through the rest of the day with low amplitude ridging building in. This pattern will likely keep most of the area dry through the day. At the surface, low pressure was centered over southeastern Saskatchewan, with a warm front extending southeast into north central North Dakota, and down through the James the Red River valleys. This boundary is easily identifiable on visible satellite imagery, marking a sharp cut off in cloud cover to its west. A cold front was also extending south from the low, near the Montana North Dakota border. As an upper trough continues to approach the region this evening, we will see some neutral to falling heights across the north after 03z, which may help to fire a couple of isolated storms in the vicinity of the north central along the advancing cold front. Most of the forcing stays well north of the International Border but convergence along the wind shift and strong instability may be enough to support a few updrafts tonight. CAMs remain meager with developing convection, and only a couple even produce storms. Given the strong instability in the forecast, any storms that can mature may become strong with some small hail and gusty winds, but the severe threat appears rather low with meager deep layer shear in the range of 25 to 35 knots. Additionally, westerly winds at the lower and mid levels suggest updrafts may have a hard time sustaining themselves because of parcel detrainment, even with strong instability present. Storms will quickly move out/diminish after 06z, with lows in western and central North Dakota ranging from the lower 50s northwest to the mid 60s across the southern James River valley. Finally, it is worth noting that near critical fire weather conditions will be possible this afternoon across portions of the far west. Much of this area will see minimum relative humidity values ranging from 20 to 25 percent. Sustained winds may approach 15 to 20 mph, but these winds will only overlap the lowest humidity values for maybe an hour or two. The west will once again see dry conditions on Saturday, but winds will be much lighter. Highs will be slightly cooler on Saturday, generally in the 80s. .LONG TERM...(Saturday night through Friday) Issued at 200 PM CDT Fri Aug 7 2020 Instability and precipitation chances increase Saturday evening and night across the southwest, expanding north and east overnight. Severe weather will likely remain south of the state Saturday night and east of the forecast area on Sunday. A few stronger storms may be possible across the southern James River valley Sunday afternoon, however. Otherwise, after Sunday, general height rises aloft with a return to mainly zonal flow should maintain fairly low chances for thunderstorms through Tuesday. It is worth noting that CIPS extended analogs have been consistent in showing a strong signal for severe weather towards the end of the work week. We have a very long way to go to work out any specific details, but this will be a time period that we will be watching closely as we may become fairly active again. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 637 PM CDT Fri Aug 7 2020 The main concern will be the chance of thunderstorms at KBIS and KMOT over the next couple of hours. A line of thunderstorms has developed in parts of central North Dakota and will continue to move east over the next several hours. Opted to carry a brief tempo group for TS at KBIS since that location appears to have the best chance of storms. Did not add to KMOT, but will keep an eye on it and update if needed. Kept the other TAF locations VFR for now. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...CK SHORT TERM...ZH LONG TERM...ZH AVIATION...CK
Area Forecast Discussion
National Weather Service Cleveland OH
913 PM EDT Fri Aug 7 2020 .SYNOPSIS... High pressure over the Great Lakes region will remain over the area through Saturday. A warm front will approach the area on Monday. Low pressure over the northern Great Lakes on Monday night will extend a cold front across the area on Tuesday. && .NEAR TERM /THROUGH SATURDAY NIGHT/... 930 pm update... There weather is quiet and pleasant this evening. No changes were needed with the near term forecast. Previous discussion... Removed PoPs in NWPA as dry air has proved too great to get any appreciable cumulus field started in the area. Otherwise, forecast remains on track. Lake enhanced clouds will continue to drift southwest across the area with areas along the lakeshore becoming mostly clear this afternoon. In addition to these lake enhanced clouds, starting to see some diurnally- driven cumulus across the area. Have a short window for a slight chance of showers and thunderstorms across NW PA this afternoon, mainly in eastern Crawford County. This is the area where the GOES-derived fields like LI, CAPE, in addition to the RAP fields, are showing the most likely spot for any shower development. Otherwise, temperatures will rise into the upper 70s to lower 80s today, trending on the cooler side where clouds reside and vise versa. By Saturday, drier mid-level air and coincident upper level ridging is set to arrive as surface high pressure retains a tight grip across the Ohio Valley. Expecting mostly sunny skies with temperatures slightly warmer than today, into the low to mid 80s. Lows will fall into the upper 50s to lower 60s. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... A weak shortwave trough should exit our CWA to the east by midday Sunday and be followed by a shortwave ridge over our region Sunday afternoon through Sunday night, allowing fair weather to grace our area. By Monday and Monday night, additional and weak shortwave troughs should begin affecting our region from the west as these disturbances revolve around a mid- to upper-level low in vicinity of western Hudson Bay. At the surface, a high pressure ridge gradually exits our CWA through the period as the embedded high pressure center moves from the Upper Ohio Valley toward the southern Appalachians. By Monday night, a cool front should begin passing through far-western portions of Lake Erie and northern Ohio as the front drifts eastward. This front will cause chances for isolated to scattered showers and thunderstorms to increase from west to east Monday and Monday night. Simultaneously, humidity will increase as a low-level return flow of Gulf of Mexico moisture overspreads our region. Temperatures trend above-normal through the period. Sunday afternoon`s highs should reach the 80`s to 90 degrees. Overnight lows should reach the 60`s to lower 70`s Sunday night. Monday should be warmer, with afternoon highs reaching the mid 80`s to lower 90`s. Monday night will be muggier, with lows in the mid 60`s to lower 70`s. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Flow aloft becomes more cyclonic Tuesday through Thursday as a longwave trough becomes established over the eastern Great Lakes and vicinity, and the embedded mid- to upper-level low advances from Hudson Bay toward Labrador. Simultaneously, multiple shortwave disturbances embedded in the longwave trough will affect our CWA. At the surface, the aforementioned eastward-moving cool front should exit the rest of our region by the end of Tuesday. Behind this front, a weak surface high pressure ridge should build over our region from the west. Multiple rounds of isolated to scattered showers and thunderstorms remain possible, especially during the afternoon and early evening hours of Tuesday through Thursday. Afternoon high temperatures should reach the low to mid 80`s Tuesday through Thursday. Lows should reach the 60`s to lower 70`s Tuesday night and Wednesday night. A high pressure ridge aloft may begin overspreading our CWA from the west Thursday night and Friday. Simultaneously, a trough aloft may begin to undercut this ridge from the Upper and Mid Mississippi Valley region. At the surface, high pressure ridging should begin exiting our region to the east as a surface low approaches from the Lower Ohio Valley. This pattern should allow chances of isolated to scattered showers and thunderstorms to persist over our region. Thursday night lows in the 60`s to lower 70`s should be followed by afternoon highs in the low to mid 80`s on Friday. && .AVIATION /00Z Saturday THROUGH Wednesday/... VFR conditions across the TAF sites will prevail through the next 24 to 30 hours with this TAF update. High pressure and light winds will continue along with mostly clear skies. The majority of the winds will be light and variable under 5 knots. There may be a little bit of a lake breeze influence for CLE and ERI tomorrow with light breeze of 5 knots from the north. Otherwise, there are no aviation concerns at this time. Outlook...Non-VFR possible with afternoon showers and thunderstorms on Monday through Wednesday. && .MARINE... Northeasterly winds around 10 knots this afternoon will be followed by light and variable winds tonight through Saturday as a high pressure center moves from Lake Huron to Lake Erie. This high pressure center will then drift toward the southern Appalachians Saturday night through Monday. Simultaneously, winds will become southerly to southwesterly at about 5 to 15 knots over Lake Erie. Southwesterly winds of about 5 to 15 knots shift to westerly following the passage of a cool front that should drift eastward over the lake Monday night and Tuesday. By Tuesday night and Wednesday, winds should become light and variable over Lake Erie as high pressure builds from the west. Waves will likely be no larger than 1 to 3 feet through the period. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Sefcovic NEAR TERM...Griffin/Kahn SHORT TERM...Jaszka LONG TERM...Jaszka AVIATION...Griffin MARINE...Jaszka
Area Forecast Discussion
National Weather Service Grand Forks ND
1025 PM CDT Fri Aug 7 2020 .UPDATE... Issued at 1024 PM CDT Fri Aug 7 2020 MCV and associated thunderstorms finally exiting the forecast area. Cold front in central ND moving east and there are scattered storms with area in north central ND and the other area was near BIS but that is fading away. Still a chance of t-storms along the front as it moves east overnight. && .SHORT TERM...(This evening through Saturday night) Issued at 353 PM CDT Fri Aug 7 2020 Showers and thunderstorms continue in the vicinity of an MCV moving ENE across the area this afternoon. South and east of this feature looks to be the best area for severe storms over the next few hours with ML CAPE at 1500-2500 J/kg and deep shear of 25-40 kts. Area of clearing southwest of MCV in area of outflow could be the best area for redevelopment as indicated by latest HRRR run. Severe storm threats will be mainly winds to 75 mph and 2" hail, but also a tornado or two will be possible. Any storms that develop have the potential to grow upscale to a line of storms in the eastern forecast area before exiting across east-central MN. A cold front will be pushing east across ND later tonight. Some storms could be severe with this potential line of storms...with the best chance along the Canadian border. Decreased chances somewhat with this features as CAMs have trended more towards storm that are isolated in nature. The cold front will usher in drier air for Saturday. Another system is expected to push east across SD and northeastward into eastern ND and MN by late Saturday night. Chances are mainly for the southern half of the forecast area after midnight. .LONG TERM...(Sunday through Friday) Issued at 320 PM CDT Fri Aug 7 2020 The main chance for impactful weather is found at the beginning of the period on Sun, followed by another chance around Thu. During Sun an approaching surface front and upper wave will increase chances for strong to severe convection. Current timing places this front in the vicinity of Devils Lake by noon, progressing to the valley by mid afternoon, then west central MN by early evening. CAPE and shear is available and it would appear the strongest storms would likely be proximal to the frontal position at peak heating time. Bulk shear at 0-6km coincident with the boundary should be in the 30 to 50 kt range, along with SB CAPES between 2 and 4K. The Red River Valley could be the main target region, with storms moving to northwest and west central late afternoon and early evening. High pressure is on schedule to provide quieter weather on Mon through Wed, with the next chance for stronger convection presenting on Thu. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 703 PM CDT Fri Aug 7 2020 Thunderstorms moving out of Bemidji Airport area 01z. Otherwise TAF sites will be t-storm free this evening and maybe all night as thunderstorm coverage overnight more isolated. South winds to become west by 09z in the RRV and toward 12z-15z BJI. Some brief MVFR cigs psbl mainly east of the Red River for a time tonight or early Saturday, higher chances Bemidji. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...Riddle SHORT TERM...Knutsvig LONG TERM...WJB AVIATION...Riddle
National Weather Service Hastings NE
646 PM CDT Fri Aug 7 2020 .SHORT TERM...(This evening through Saturday night) Issued at 400 PM CDT Fri Aug 7 2020 Upper air and satellite data showing continued generally westerly flow across the region this afternoon, as we sit on the northern edge of high pressure centered over TX. A subtle shortwave disturbance embedded in the westerly flow kept pesky isolated showers and a few rumbles of thunder around portion of the area into the early afternoon hours...mainly between I-80 and the NE/KS state line. The day started out with plenty of low level stratus across the CWA...and it has been slow to diminish across areas along/east of HWY 281. To the south/west of this area, skies are mostly sunny/`ll likely take a couple more hours for things to clear further in the east. Even with the isolated precip/clouds and with several hours yet for temps to rise along/east of HWY 281, temperatures this afternoon have worked out pretty well...3 PM obs are in the mid 80s to right at 90. Little change in the sfc pattern today, with the CWA remaining in between high pressure over the Great Lakes/Midwest and a trough of low pressure extending through the High Plains. Speeds have topped out around 15 MPH for most, with at least occasional gusts of 20-25 MPH. Dry conditions remain in the forecast tonight. Models are in good agreement showing little change overall in the pattern, with flow remaining westerly and the CWA sitting between the departing disturbance to the east and the next one that will be moving in later Saturday. At the sfc, models showing low pressure sliding a bit further east into SW NE/W KS tonight...with a weak frontal boundary extending NNE through portions of central NE. Expecting winds to turn more light/variable near/along this sfc boundary, and the development of fog will again be a concern as we get into late tonight/pre-dawn Saturday morning. Inserted a mention of patchy fog for areas north of Phillipsburg/York line...may end up needing an `areas` mention for I-80 north where some models show better potential. Also increased sky cover in this area for the potential for another round of low level stratus. Once any morning fog/clouds dissipate, the main focus as we get through Saturday turns to the west, and the increasing chances for thunderstorms. Models showing the upper level ridge axis shifting a bit east, with a shortwave disturbance emerging from the Central Rockies later in the day. The main sfc boundary is expected to be set up over western portions of NE/KS by mid-late afternoon, providing a focus for thunderstorm development as the better upper forcing moves in. Kept chances out until after 21Z, and even that may be too soon, as models are in good agreement showing hefty capping to overcome/mid level temps around 15-16C. It may be closer to/after 00Z before activity moves into/develops over the western CWA...and there are still questions with the coverage/southern extent. The best chances for more widespread activity currently look to slide north of the CWA. What would help bring more storms to our CWA would be the lift along the nose of the LLJ that develops in the evening, but there are even some questions there with its location. Current forecast has the higher PoPs (30-40%) along/north of I- 80...but can`t completely rule out precip for any particular area, so have 20 PoPs all the way into north central KS. For thunderstorms that develop, certainly no shortage of instability available...and deep layer shear is sufficient for severe weather to be a concern. The SPC Day 2 outlook has most of our Neb counties included in the Slight Risk area, with the Marginal south into much of our KS area. Large hail, damaging winds and heavy rain would be the primary hazards. Activity looks to push east of the CWA sometime during the 06-09Z time frame. Did not make any notable changes to other weather elements for Saturday. Expecting SSE winds around 10-15 MPH for most areas, perhaps on the gusty side across our KS counties. Still expecting it to be a hot day, with high temperatures reaching the lower-mid 90s for most...and combined with dewpoints in the 60s and 70s...heat index values across much of the CWA look to top out in the 100-105 degree range. Opted against a Heat Advisory at this time, with current forecast heat index values below 105 (official criteria) vs at or above that value...but it will be something for upcoming shifts to watch. .LONG TERM...(Sunday daytime through Friday) Issued at 400 PM CDT Fri Aug 7 2020 General overview of this 6-day period: As a whole, this stretch can probably be summed up as "pretty typical summer/August weather". In the mid-upper levels, our Central Plains area resides (generally) within a west-northwest flow pattern, along the interface between stronger flow to our north, and weaker flow to our south, where a large-scale ridge will be centered over the AX/NM/west TX region much of the next week. With the exception of Sunday-Monday (which are respectively the overall-hottest and coolest days out of these six...more on this below), the majority of this time looks to feature near to slightly above normal readings for mid-August (not overly-hot, but not nearly as cool as what we saw a few days back either). This means highs mainly mid-80s to around 90, and overnight lows mainly well into the 60s. As for rain/thunderstorm chances, there are several of them scattered throughout the entire Sunday evening-Friday time frame, but as is also typical of this "summery" weather pattern, they will be driven by more subtle disturbances aloft and/or nocturnal low level jet forcing. This means that confidence in "exact" details of timing/location is fairly low in any one particular day/night period, other than to say that the evening through early morning hours would tend to be more favored than the majority of the daylight hours for precipitation (again, very typical for this time of year). For sure, there is good reason that all rain chances (PoPs) through this time frame have been held down in the 20-40 percent range at most, as confidence is not there to go higher (yet). Severe storm chances: While no days/night currently "scream" widespread severe weather (especially given such subtle forcing mechanisms), this weather pattern is known for occasional bouts of at least limited strong/severe storm activity, especially during the evening and early-overnight hours. Have little doubt that at least a few periods will eventually be assigned Marginal/perhaps Slight Risk categories by SPC as they draw closer in time, but it`s just too soon to confidently assess exactly which ones. Technically, our extreme northern coverage area (CWA) is already "nicked" by the southern fringes of a Marginal Risk area for Sunday evening, but some of the latest raw model data actually suggests that our west- southwest areas may be just as deserving of a Marginal Risk for Sunday, so would not be surprised to see things change a bit in later outlooks versus the current SPC Day 3. With the "big picture" covered above, will finish up with a bit more detail on the Sunday-Monday time frame, which are not only the nearest-in-time of the "long term" periods, but also the most intriguing in terms of temperature trends/contrast from one day to the next. Not to mention that heat concerns for Sunday are trending upward. Sunday-Sunday night: While we have been "talking up" Saturday afternoon heat concerns for a few days now (in our Hazardous Weather Outlook etc.), Sunday has trended upward/a bit "worse" than previous forecasts, and in fact now looks just as hot (if not hotter) than Saturday for much of the CWA. Needless to say, a mention of Sunday heat has now been added to our HWO, as the afternoon looks to feature widespread 100-105 heat index values, with the overall-highest readings favoring Nebraska counties east of Highway 281. Given that 105+ heat index is technically our Advisory criteria, this could end up being a pretty close call to needing one for at least parts of the area. As for actual air temperatures (Max T), most of the CWA is now aimed into the 93-97 range, with typically-hotter southwestern counties perhaps flirting with 100 degrees. Fortunately, there should be at least a modest southerly breeze during the afternoon (generally 10-15 MPH, with some higher gusts especially in KS zones) to provide some limited relief. Turning to precipitation/thunderstorm chances, have maintained the dry forecast area-wide for the daytime hours (prior to 7 PM), as odds favor any lingering Saturday night activity to be departed off to our east by sunrise. However, have also maintained some low- confidence PoPs/storm chances for Sunday evening-night, as latest NAM/GFS suggest that at least limited activity could either drift in from our west and/or form overhead late in the night as a cold front starts to drift in from the north. As hit on above, do not be surprised to see a bit more of our CWA eventually end up in an SPC Marginal risk in later outlooks. Monday: While most of the daytime is looking dry/storm-free, cannot completely rule out some spotty activity near and behind the aforementioned cold front working trough the area. However, this cold front is truly the bigger story of the day, as it will bring a period of somewhat-breezy northeast winds to the CWA (gusts 20+ MPH), and also a solid 10+ degree cool-down (versus Sunday) to MOST of our CWA. That means highs "only" in the low-mid 80s for most of the area. However, our KS zones will not feel this push of cooler air quite as much, and especially Rooks-Osborne-Mitchell counties could still manage to hit 90 (still cooler than Sunday). && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday) Issued at 619 PM CDT Fri Aug 7 2020 Fog is the main concern through the period are there are some indications that vsbys could drop significantly towards morning...but others that are conflicting. Expect steady southerly winds this evening to diminish as they shift and become southeasterly overnight...with hints of LLWS focused just to our east. As winds diminish and skies remain clear along with elevated dewpoints...the potential for fog exists with lows forecast to be a few degrees below afternoon dewpoint values. expect some fog to develop after midnight...but density is still a bit uncertain as main supporters are these crossover temps being exceed and SREF guidance, with the HRRR not indicating any fog potential at all. Otherwise...after any fog that develops burns off...expect light southeasterly winds tomorrow with just some passing mid/high level clouds. A chance for thunderstorms will spread from west to east across the local area after 09/00Z. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ SHORT TERM...ADP LONG TERM...Pfannkuch AVIATION...Rossi