Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/30/21

Area Forecast Discussion
National Weather Service Goodland KS
919 PM MDT Wed Sep 29 2021 .SHORT TERM...(This evening through Thursday night) Issued at 209 PM MDT Wed Sep 29 2021 Satellite imagery and 500mb RAP analysis showed southwest flow over the region this afternoon, with the High Plains placed between an upper ridge to the east and an upper trough pushing into the Rockies. Meanwhile at the surface, a cold front approached the area from the northwest. At 2 PM MT, a thin line of cumulus clouds/storms had developed along a lee trough axis just east of the Colorado border. Temperatures ranged from the low 70s to mid 80s, with southerly winds shifting to the north from the west. For tonight: A line of thunderstorms/MCS is expected to develop by the early evening, generally just east of the Colorado border, as the cold front moves into the region. This line should gradually move southeastward overnight. While severe weather is not anticipated due to the nature of the front and shear profile, some gusty winds could occur with these storms. However, the main threat is still anticipated to be heavy rainfall and flash flooding, particularly along and east of Highway 83 in northwest Kansas. PWATs of 1-1.5 inches are forecast, which exceeds the 90th percentile for this time of year. Parameters also support some backbuilding/training of storms, further suggesting a flood threat. That being said, dry soils will be a limiting factor due to their ability to absorb a decent amount of moisture and prevent significant runoff. Have continued the Flash Flood Watch for the eastern part of the area. Otherwise, temperatures fall into the low 40s to mid 50s overnight, with the cooler temperatures in eastern Colorado behind the front. Can anticipate strengthening north winds behind the frontal passage, with gusts around 30 mph or so. On Thursday, the boundary should be clear of the region to our east, with lingering showers and storms slowly tapering off to the southeast through the morning hours. Southwest flow prevails aloft as the trough to the west digs into the Desert Southwest, likely closing off into a low. Dry weather is anticipated during the afternoon as temperatures rise into the 60s. Dry conditions continue into Thursday night ahead of the southwest system, with lows in the low 40s to low 50s. .LONG TERM...(Friday through Wednesday) Issued at 235 PM MDT Wed Sep 29 2021 For this long-term forecast period, the main period of interest will be Friday into Saturday as an upper level disturbance moves across the Plains. Beyond this time frame, expect generally quiet weather. To begin with Friday into Saturday, an upper level low, currently located over the desert southwest, will progress slowly northeast across the Great Plains. South winds preceding this system shall lead to moisture advection with precipitable water readings climbing to around 1.25", above the 90th percentile for this time of year. Atmospheric lift increases as the low moves in, and should see precipitation break out south of the Tri-State Region, eventually spreading north across the forecast area during the day Friday. Rain may begin approaching I-70 as early as Friday afternoon, but most of the precipitation should hold off until the overnight hours Friday. Rain will slowly come to an end Saturday afternoon as the system exits to the northeast. Looking at instability, there isn`t much to speak of, so think this will be a long-duration shower/stratiform rain type event with some embedded rumbles of thunder. While precipitable water readings are high for this event, the lack of significant coverage in thunderstorms lowers the risk of flash flooding as it may be hard to get flash flood producing rainfall rates. Therefore, will not be advertising any potential for severe weather and flash flooding with this system as it looks like any threat that exists will be near zero. With rain and cloud cover persisting most of the day Saturday, would not be surprised if low temperatures are lower than advertised. Current forecast is already on the lower end of the forecast spectrum...between the 10th and 25th percentile, but signs point to a cloudy, cool, rainy day. Beyond Saturday, the upper level pattern projects are becoming a little more clear, but still some model disagreements reduce certainty in exactly what will happen. Overall, it looks like an upper level low will dominate over the eastern United States with a upper level ridge over the Plains. This will leave us under light flow aloft without any disturbances moving our way. With south flow at the surface, increasing temperatures aloft, and fair skies/lack of precipitation, think it is becoming safe to say that warmer temperatures will return. So, made a slight nudge to high temperatures, and even some low temperatures, as a result of these factors. Fall will day, just may not be until later in October. Also, it does not appear as though we need to worry about frost or a freeze through at least the next 7 days. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 917 PM MDT Wed Sep 29 2021 Cold front will continue to move east of both KGLD and KMCK with showers ending overnight. Ceilings will be slower to improve, with IFR through early Thursday morning, then MVFR to VFR by mid day on Thursday. Surface winds will also gradually decrease as high pressure builds into the area. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...Flash Flood Watch until 10 AM CDT Thursday for KSZ003-004-015- 016-029. CO...NONE. NE...NONE. && $$ SHORT TERM...JBH LONG TERM...RRH AVIATION...024
Area Forecast Discussion
National Weather Service Marquette MI
643 PM EDT Wed Sep 29 2021 .SHORT TERM...(This evening through Thursday) Issued at 345 PM EDT WED SEP 29 2021 The 19Z RAP Analysis shows a surface high pressure located over the Southern James Bay region, slowly sagging to the south over Ontario this afternoon. The effects of this surface high pressure can be seen on GOES satellite imagery for the visible/WV spectrums. Dry air to the east is slowly being advected into the region, resulting in mostly sunny conditions for most of the cwa this afternoon. This has made it a very nice day as we remain dry, and warm. Temperatures presently are in the 70s for the interior UP across the east half, and in the 60s near the lakeshores as onshore flow occurs from the lake breezes pushing inland. Areas furthest to the west have surged to near 80 degrees, with even a few locations making it into the lower 80s in Gogebic County. Taking a look aloft at the RAP MSAS Analysis for H5 heights, a pronounced upper level ridge is becoming elongated as it continues its amplification into Manitoba and far west Ontario. The ridge axis has shifted slightly to the east since this morning, allowing for temperatures of 16-18C at 850mb to creep northward via WAA. Expect the warmest temperatures at the surface to continue for the west half especially across the interior as the thermal ridge aloft continues to build today through Thursday evening across the west half of the cwa. A large and expansive H5 trough is currently being observed over the New England area, and another longwave h5 trough is present over the Four Corners region aloft. This has the upper level ridge over the Upper Midwest becoming wedged in between it, and this ridge will amplify in the coming 24-36 hours. With the surface high pressure remaining near the Northern Great Lakes, the weather will remain calm and dry overnight. The weak pressure gradient should allow for calm winds to settle into the area. The effects of the surface high pressure will be experienced most across the east and central interior portions of Upper Michigan. Thus, coolest conditions will be in that area. Surface temperatures will decrease down to the 40s in areas over the interior, away from the lakeshores overnight for lows. However, WAA at 850mb with slightly elevated southerly winds across the west half will allow for temperatures to remain in the low to mid 50s for overnight minimums. As previously mentioned in the AM forecast package, patchy fog will be possible late tonight across the cooler areas over the south central and east. Thursday will be more of the same, as the effects of the surface high pressure allow temperatures to quickly rise once again. Mostly sunny conditions can be expected as areas that have low stratus or fog that developed in the morning quickly erodes within a couple hours of sunrise. Most areas can expect to see highs in the 70s over the central and interior east of the cwa, with the lakeshores remaining cooler as onshore flow develops once again by afternoon, limiting temperatures to the upper 60s to near 70. The west half will see the warmest diurnal maximums as 850mb temperatures of 15- 18C mix down to the surface. Expect to see increasing clouds in higher levels of the atmosphere by late afternoon and early evening for areas across the west as the next weather system approaches the area. .LONG TERM...(Thursday night through Wednesday) Issued at 354 PM EDT WED SEP 29 2021 Thursday night, surface high pressure ridge will be centered near the ONtario/Quebec border. On the large scale, upper-level ridging will remain centered overhead sandwiched in a sort-of omega block between a trough pushing onshore into British Columbia and a deep closed upper low over Nova Scotia. The ridge will begin to break down in response to a a couple of weak short waves lifting northeastward out of the Northern Plains, eventually triggering weak cyclogensis over Northern Ontario. This process will lead to increasing cloudiness through the night Thursday night and into Friday, followed by showers overspreading the west half Friday morning. Models indicated there could be enough instability for a few embedded rumbles of thunder as well. Thursday night`s lows will range from the upper 40s east where it will remain mostly clear to the upper 50s west where cloud cover will exist for more of the night. Highs on Friday should still get well into the 70s despite the increased cloud cover, but could end up cooler than currently forecast over the west depending on the coverage of showers. The developing low pressure to the north will slowly drag a weak cold front across the area on Saturday with cloudy skies and showers continuing. Models have been trending towards a slower FROPA, so would not be surprised to see POPs increase on Saturday in subsequent forecast packages. These showers should clear out of the area by Sunday morning as the front settles over the far eastern U.P. and northern Lake Michigan. Look for highs in the 60s both Saturday and Sunday. As for Monday, ensemble clusters still generally show height anomalies aloft retrograding back towards Ontario and the Canadian Prairies form Quebec as ridging erupts over that area. At the same time, some sort of wave will dive southeastward beneath the ridge and then cut off from the flow. However, the total ensemble mean between 24 hours ago and the most recent cycle (last night`s 00z) shifted the ridge to the north and therefore took a pretty substantial jump towards more of a troughing signal over the Great Lakes. Given placement and strength differences, it makes sense that neither the total ensemble mean nor any of the clusters resolves an actual cutoff low. What all of this means is that Monday through the middle of next week, which yesterday looked to still be fairly warm, now looks cool and cloudy. Clearly the models are still trying to figure this pattern out, so have not made any changes to the NBM initialization for this period. Expect highs in the 60s and lows in the 40s to around 50 to continue into the middle of next week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 642 PM EDT WED SEP 29 2021 VFR flight conditions are expected for all terminals through the entire forecast period. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 252 PM EDT WED SEP 29 2021 Surface high pressure will remain over Southern Hudson Bay from this afternoon through late Thursday. This will keep winds below 20 kts. Despite and approaching surface trough early Friday through the weekend, wind gusts are still anticipated to remain below 20 kts due to a weak pressure gradient being present. By Sunday, the surface trough will slowly trek to the south through the Lower Great Lakes. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...BW LONG TERM...RJC AVIATION...07 MARINE...BW
Area Forecast Discussion...UPDATED
National Weather Service Norman OK
1055 PM CDT Wed Sep 29 2021 ...New AVIATION... .SHORT TERM... (This evening through Thursday) Issued at 209 PM CDT Wed Sep 29 2021 On the synoptic scale, troughing in the west is present and slowly moving eastward, influencing lee surface troughing and supporting southerly winds across our area. Moisture transport northward/northwestward is complicated some by residual effects of yesterday`s convection on upstream environment across Texas. Some PBL moisture depletion through the convective overturning process may be recycled northwestward in model depictions with a tendency to mix out a thin layer of moisture. In reality, as this writing, surface observations and evidence in GPS-PWAT and various satellite moisture channels suggest this may be occurring to a lesser degree. Thus, the more moist end of the NWP/CAM spectrum, and non-HRRR (due to dry bias) models seem more realistic for this afternoon`s scenario. Isolated convection should form near a sharpening dryline later this afternoon across western north Texas and far southwest Oklahoma. Visible satellite shows initial relatively high-based diurnal cumulus in the vicinity of Seymour, and this general area should be where at least isolated convection develops. RAP forecast hodographs are lengthy enough to potentially support organized multicells and perhaps transient supercells. Associated convective hazards would mostly be wind given the thermodynamic profile (some midlevel dry entrainment and well-mixed sub-cloud layer), although degree of instability could favor some marginally severe hail. This conditional threat should be across a fairly confined area of western north Texas, mainly after 4pm. Mean cloud-layer wind would support northeasterly storm motions around 20-25 mph, but any quasi-supercells may deviate to more westerly and slow to about half the forward speed. There is evidence of wake subsidence behind the departing wave seen in visible satellite elsewhere. This is especially true across our southeastern counties where a sharp delineation of more robust cumulus/strato-cumulus field abruptly diminishes as mesoscale subsidence, evident in water vapor channel imagery, overspreads it. Therefore, it`s doubtful convection will form anywhere else across our area except perhaps northwest Oklahoma where some HREF CAM members do generate convection late today. There is a mid-level low with a fairly well-defined circulation moving east-northeastward through west Texas now. Although this could help precondition our environment for convection even more, it`s unlikely to be a significant player until perhaps later tonight. Weak mid-level warm advection associated with this feature may support some isolated convection late evening onward even eastward into central Oklahoma. Tomorrow, the aforementioned western trough and associated large scale ascent will combine with an increasingly moist environment (PWAT values above the 90th percentile max moving average on SPC`s sounding climatology) to increase our precipitation coverage substantially. Convection from the previous diurnal cycle over western Kansas may continue to propagate into northern portions of the area near/north of a surface front. Even further south, some warm advection-driven convection likely will increase. Overall coverage and amounts will probably vary given the convective nature, similar to yesterday, but many locations will receive at least some beneficial rainfall. BRB && .LONG TERM... (Thursday night through next Tuesday) Issued at 250 PM CDT Wed Sep 29 2021 Little change is expected into Friday morning, with periodic showers and thunderstorms continuing underneath the upper-level chaos. As the upper-level system becomes more organized during the day on Friday, rain and storms will become more widespread. Limited instability will keep storms mostly under control, so strong/severe storms will be the exception rather than the rule. The storm system finally moves off to the east on Sunday, and rain chances will come to an end for a while. Cooler and drier air will flow into Oklahoma and north Texas behind the departing upper low. Toward the end of next week, the upper low may retrograde all the way back to the southwestern Midwest, bringing rain chances back to Oklahoma. At this point, the chances are low, since that is more than a week away, and the trajectory of the low is quite uncertain that far out. && .AVIATION... (06Z TAFS) Issued at 1051 PM CDT Wed Sep 29 2021 VFR first 6 hours then deteriorating conditions expected toward and after 12Z mainly across northern into central parts of Oklahoma ahead of and near approaching frontal boundary. Latest guidance point to the greatest coverage of shra/tsra across northern into central Oklahoma tomorrow morning. Chances appear lower farther south but convection still possible tomorrow afternoon into the evening hours. && .UPPER AIR... Issued at 209 PM CDT Wed Sep 29 2021 An Upper Air flight is planned for 12z Thursday to sample details of the moisture and temperature profiles that could be helpful to the forecast. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 67 81 64 76 / 20 70 70 70 Hobart OK 66 86 62 78 / 20 50 80 80 Wichita Falls TX 68 87 64 77 / 30 60 80 70 Gage OK 61 79 58 71 / 40 70 70 80 Ponca City OK 66 81 63 78 / 20 80 70 70 Durant OK 67 84 66 79 / 20 60 70 70 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ SHORT TERM...12 LONG TERM....23 AVIATION...11
Area Forecast Discussion
National Weather Service Phoenix AZ
507 PM MST Wed Sep 29 2021 .UPDATE...Updated Aviation discussion. && .SYNOPSIS... A weather system will provide slight to moderate chances for showers and isolated thunderstorms later today and into Thursday, especially from Phoenix eastward. After continued below normal temperatures through Friday, increasing high pressure over the weekend should bring readings back to around normal by Sunday. && .DISCUSSION... Water vapor imagery shows the southern extension of a trough over the eastern Great Basin through the lower Colorado River Valley. Area of cloudiness and modest ascent is resulting some weak showers across central Arizona this afternoon. Although some drying has occurred over the past 48 hours, surface dewpoints are holding in the 50s across the lower deserts, and objective analysis and ACARS soundings are showing PW values near or just under one inch over the southern half of Arizona. A few showers and thunderstorms are possible across La Paz/western Maricopa Counties this afternoon and evening closer to a low-level moisture access, but coverage should remain fairly limited. More widespread activity is expected to develop overnight, primarily from the Phoenix metro area eastward, as the upper trough continues to progress eastward. Latest HREF and HRRR runs are very consistent in highlighting this area overnight, with the main uncertainty being how far westward the area of showers and thunderstorms will extend. Precipitation amounts on average should range between 0.10 and 0.25 of an inch, but the HREF maximum precip fields suggest some isolated locations could receive over 0.50 of an inch. Gusty outflow winds are also possible in the vicinity of any thunderstorms, with the HREF highlighting a 10-30% chance that 30 kt winds affect the Phoenix area overnight. This may be enough to kick up some localized blowing dust in Pinal County. By daybreak Thursday, the bulk of the activity should shift eastward primarily into southern Gila County, with drier air overspreading the lower deserts. Wrap around moisture accompanying the main upper-level circulation may spread southward off the higher terrain towards northern Maricopa County during Thursday afternoon, but expecting any additional precipitation to remain isolated. The upper low will begin to accelerate late Thursday east of the region, bringing modest height rises to the Southwest by Friday. Temperatures will remain below normal and only expected to reach the upper 80s through Friday in Phoenix, and lower to mid 90s in southeast California. Temperatures will gradually warm through the weekend closer to seasonal normal, reaching the upper 90s in many locations Sunday and Monday. NBM guidance is even suggesting there`s some chance for triple-digit readings, peaking Monday at 19% in Phoenix and 32% in El Centro. The next feature of interest will be an intense and well-defined cutoff low near the coast of northern Baja California, that is forecast to rapidly shift northeastward across the Southwest Tuesday and Wednesday of next week. The orientation of this feature is not expected to be too favorable for significant moisture advection and precipitation across the lower deserts, but perhaps moreso across northern Arizona. However, given the potential intensity of this system, some outlying members are highlighting higher QPF amounts. The 95th percentile 24-hour QPF values of the NBM range between 0.25-0.5 inch for south-central Arizona, while the 50th percentile values are 0. Trends will certainly be worth monitoring. Otherwise, a slight decrease in temperatures into the low 90s along with breezier afternoons can be expected by mid-week. && .AVIATION...Updated at 0000Z South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Showers and thunderstorms are expected to develop overnight across portions of south-central Arizona. Latest radar and model trends are suggesting a more active late evening and overnight period, and 00z TAFs were adjusted to include VCTS and ceilings down to 7k feet for the Phoenix sites beginning around 07z. Severe storms are not anticipated, however the strongest storms will be be capable of producing wind gusts above 35 kt. Conditions are expected to improve during the 12z-15z period as the trough axis pushes slowly eastward through the Valley. Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather impacts expected. Mostly clear skies and northerly winds occasionally up to 12 kt will prevail through Thursday at KIPL and KBLH. && .FIRE WEATHER... Friday through Tuesday: Conditions will dry out and warm up through the weekend and early next week. Sunday will be the hottest and driest day with afternoon highs reaching the mid to upper 90s while minimum RH`s drop into the 15-25% range. Min RH`s will be slightly wetter on other days. Overnight RHs will rise into the 40-60% range for most areas on most nights. Otherwise, winds will be fairly light with directions favoring local diurnal/terrain influences. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Rogers AVIATION...Hirsch FIRE WEATHER...12