Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/11/22


Area Forecast Discussion
National Weather Service Des Moines IA
551 PM CST Sat Dec 10 2022 ...Updated for the 00z Aviation Discussion... .DISCUSSION.../Tonight through Saturday/ Issued at 358 PM CST Sat Dec 10 2022 Forecast Highlights: - Patchy widespread fog expected late tonight through Sunday morning - Quiet and mainly Dry Sunday into Monday with mild temperatures - Large system continues to signal more active weather, with mixed ptypes and breezy/windy conditions late Monday through much of the work week Dreary and foggy conditions continued across Iowa throughout the day, with patchy fog still being reported this afternoon over most of the region, along with widespread stratus outside of some clearing over parts of western Iowa. Drizzle continued mainly over eastern and portions of central Iowa through much of this morning as the upper level shortwave moved across the upper Midwest, though has since ended. Temperatures largely due to the dominant cloud cover has kept temperatures on the cooler side today with values in the low to mid 30s north and in the upper 30s further south. Therefore knocked highs down a few degrees to account for these trends. Model soundings continue to overall highlight the potential for returning patchy to locally dense fog tonight into Sunday morning. The NAM and RAP soundings favor more saturation in the lowest half to 1 kilometer space with subsidence and light winds, though the GFS keeps a drier column overall though other parameters looks favorable. HREF guidance paints an area of relatively widespread fog over much of the state, leaning with the more saturated solutions. Will continue to include fog in the forecast into Sunday before eventually dissipating later in the day. Use extra caution and take it slow on the roads if traveling late tonight into Sunday. Stratus looks to be a bit slower to move out tonight, especially east, which could limit dense fog potential but cannot rule it out completely, especially north. Overall, western Iowa could see some clearing this evening while the rest of the state continues to see lingering cloud cover. Temperatures are expected to be cooler in the upper teens through the 20s tonight, as winds turn more northwesterly with weak CAA bringing in cooler air. With an narrow upper level ridge and associated surface high pressure system pushing through behind the departing shortwave trough Sunday, quiet and dry weather is expected. Low level flow will remain northwesterly through the afternoon before shifting more southerly, which will allow for mild temperatures with highs in the 30s north and in the low 40s further south. Cloud cover will largely hang on over much of the state through the afternoon, before clearing from southwest to northeast into the evening. Dry weather should remain for the most part Monday, though increasing moisture with the increasing southerly flow will quickly bring returning cloud cover ahead of a large system expected to impact the region over the following several days. Temperatures will remain mild in the upper 30s north to mid 40s south. A very strong upper level trough and developing low pushing out of the Rockies Monday into Tuesday continues to signal a longer term active weather period through much of the next work week. A longer band of more widespread lift just ahead of the system with increasing moisture looks to bring in increasing precipitation chances Monday evening into Tuesday. Deterministic models continue to generally remain in agreement on the general track of the system , but again strength remains somewhat different as the GFS and Euro favor a slower onset of precipitation not arriving until Tuesday, though the NAM and Canadian models are more robust with an earlier start Monday afternoon to evening in western Iowa. A much colder NAM solution however paints a broad area of freezing rain Tuesday morning into the afternoon suggesting ice accumulations down into central Iowa, before switching over to rain. With warmer air more favorable over the region from the rest of the model solutions, all precipitation will more likely fall as rain throughout Tuesday across the state. More efficient rain production continues to also be evident with overall totals looking to range upwards of an inch in parts of the state, though the strength differences among models do introduce more uncertainty given the timing out ahead of the system, as the GFS ensembles also indicate a wider range of solutions in the most recent runs. Freezing rain cannot be ruled at times Tuesday mainly over northern Iowa with minor ice accumulations still looking possible. Gusty winds continue to look rather concerning as NBM guidance in recent runs has favored stronger values in the 30 to 40 mph range, isolated to 45 mph especially north Tuesday as the tighter pressure gradient travels across the state. Advisory potential continues to look more certain but will have to continue and watch if the trend remains consistent in the coming days, as adjustment are expected to occur. Into Wednesday as cooler air moves in, a transition mainly to a rain/snow mix to snow is expected as the system lifts northeast, largely impacting northern into portions of central Iowa while dry air further south could allow for a short period of dry weather. Specific snow totals are not known at this time, as this will largely depend on the evolution on this system which continues to be more uncertain this far out, but overall QPF totals looks rather light in comparison to Tuesday`s projected values. Model guidance continues to largely depict lingering snow over much of the state Thursday as another system over the northeastern CONUS traveling southwest blocks this large system from making a quicker exit, which again looks to remain on the lower side for any additional accumulations. Colder air behind the departing system Friday into the weekend will allow for slightly cooler highs in the 20s to low 30s and lows mainly in the teens. && .AVIATION.../For the 00Z TAFS through 00Z Sunday evening/ Issued at 548 PM CST Sat Dec 10 2022 Clearing has moved into western Iowa but the cloud level steering flow will shift from the west to the north/northwest overnight which will eventually stop the eastward movement and draw even more stratus south out of MN. KDSM/KFOD are the most likely to have a few periods of VFR overnight otherwise MVFR/IFR cigs will remain common. Some fog is possible in the clear regions which could help fill in cigs as well overnight. Cigs should finally break later Sunday afternoon if the eastward push is halted tonight. The wind will be mostly light through the period. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Bury/Martin AVIATION...Donavon
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
754 PM CST Sat Dec 10 2022 ...New UPDATE... .UPDATE... Issued at 725 PM CST Sat Dec 10 2022 Lowered the PoPs slightly across the Hill Country into the overnight as the latest HRRR runs and the WRF-NSSL indicate that majority of the activity develops along and east of the I-35 corridor where the southward advancing front is expected to meet an ongoing region of surface convergence extending from around I-35 into the Houston CWA. SPC with the recent 01 UTC update of the Day 1 Convective Outlook adjusted the marginal risk for tonight into coastal plains where the models blossom the strongest convection in that region of stronger surface convergence. WPC introduced a marginal risk as well this afternoon for excessive rainfall for areas mainly along/east of I-35 and north of I-10 as these storms could be capable of producing a quick 1 to 2 inches of rain with a few localized higher amounts possible. Additionally, expanded patchy fog for across much of the region into Sunday morning once the storms ends given lingering low- level moisture levels with small dew point depressions and modest post-frontal northerly winds. && .SHORT TERM... (Tonight through Sunday night) Issued at 140 PM CST Sat Dec 10 2022 Synopsis/Mesoanalysis: 12 PM CST surface observations depict a slow- moving cold front extending from the DFW Metroplex southwest into the Edwards Plateau and Big Bend region. Warm, moist air is entrenched to the south of the boundary, with most stations reporting air temps in the mid 70s and dew points in the middle 60s. Lower 80s have been noted over portions of the Coastal Plains. Combined with low-level convergence along the slowly-progressing frontal boundary, this air mass should help fuel scattered thunderstorm development primarily to our north through the early and middle afternoon hours. Augmented further by encroaching height falls and DPVA affiliated with a shortwave trough currently centered over Sonora, this activity should persist through the overnight hours tonight, impacting locations primarily along and east of US 281 between midnight and daybreak Sunday morning. Despite a weak northerly wind shift behind the departing front, warm and muggy conditions will continue through the duration of the short term period. This Afternoon: Although the encroaching cold front will still be situated to our north, showers and isolated thunderstorms can`t be ruled out along and east of I-35 and I-37. Recent radar and satellite trends have indicated several attempts at convective initiation over this portion of the CWA, each being thwarted by a capping inversion evident in the 12Z DRT RAOB and composite soundings from AUS and SAT Intl Airports. Nevertheless, short term model guidance suggests that the cap will erode with continued surface heating, boundary layer moistening, and approaching pre- frontal convergence through the late afternoon and early evening hours, likely explaining the development of isolated convection just ahead of the front in these solutions. Have thus accounted for this potential in the afternoon update. Though certainly not widespread, an isolated strong/severe storm is possible with this prefrontal activity, with damaging wind gusts in excess of 60 MPH and hail exceeding quarter size being the primary concerns. Tonight: Anticipate a gradual increase in thunderstorm coverage along/east of US 281 as the Sonora shortwave begins to overspread the region. Like this afternoon, an isolated severe thunderstorm is possible as this activity moves through. Given a predominantly linear convective mode arising from parallel alignment between the deep layer flow and advancing surface front, damaging wind gusts reaching/exceeding 60 MPH will be the primary hazard in any severe storm. While secondary to damaging winds, an isolated tornado can`t be ruled out, particularly in any location where surface winds can back out of the east-southeast. The Storm Prediction Center has thus continued to carry a marginal (level 1/5) risk for severe weather over the eastern CWA in light of this potential. Tomorrow-Tomorrow Night: Conditions will remain muggy despite the passage of the front. Many locations in the Coastal Plains, Winter Garden, and portions of the I-35 corridor will see patchy fog through the mid morning hours Sunday. Some of said fog could become dense. Sunday highs should be a touch cooler than today with pesky cloud cover sticking around into the late afternoon hours. Mild lows and additional patchy fog will be possible Sunday night into early Monday morning. && .LONG TERM... (Monday through Saturday) Issued at 140 PM CST Sat Dec 10 2022 Southerly flow will return quickly on Monday as lee side surface cyclogenesis develops ahead of a deep slow-moving low level trough in the western CONUS. 850mb winds near 25-30 knots will lead to weak ascent from warm-air advection. Forecast soundings show a decent moist layer with adequate lapse rates for some isolated light rain showers or perhaps some drizzle Monday afternoon. Will forecast 10- 20 PoPs for areas mainly east of the Highway 281 corridor. Things should dry out for Monday night, but a Pacific front will move east into the areas late Monday night into Tuesday morning and will bring with it a chance for deeper convection. Should see a decent coverage of showers and thunderstorms along and just behind this frontal boundary for areas mainly north of a Kerrville to New Braunfels to Cuero line. The best areas of forcing will be well to our north and therefore not expecting much in the way of strong storms or heavy rainfall from this activity. Rainfall amounts will generally average less than a quarter of an inch. Things will dry out Tuesday night with a dry forecast then expected for the remainder of the long-term forecast period. Temperatures in the extended will begin warm with highs in the upper 60s to near 80 on Monday and Tuesday. Should see slightly cooler temps behind the front on Wednesday with highs in the 60s to near 70. A stronger front is expected on Thursday and highs Friday and Saturday should be in the upper 40s to 50s across the area. No rain is expected with this front. Low temperatures in the period will follow the same trend as the highs, starting off well above normal, before returning back into the 30s to lower 40s Friday and Saturday. && .AVIATION... (00Z TAFS) Issued at 518 PM CST Sat Dec 10 2022 VFR flight conditions are in place this evening but expect for conditions to deteriorate tonight into Sunday as a cold front will advance into and across the region. Convection will be expected to develop along and out advance of this boundary as it moves into the region. The greatest storm potential for the I-35 TAF sites (KAUS, KSAT, KSSF) where a solid line of convection is likely to develop occurs by around the midnight hour and likely should continue for a few hours. Activity then gradually wanes into the morning where I have kept VCSH in the TAF package at those sites. MVFR ceilings and visibility could accompany these storms. Flight conditions will remain poor behind the storms through Sunday morning as lingering low-level moisture will yield to patchy fog and early morning ceilings as low as IFR to LIFR. Gradual improvement back to MVFR levels can be expected into and through Sunday afternoon. The winds become north to northeasterly behind the front but speeds should remain below 10 knots. As mentioned in the previous 18Z aviation discussion, no storms are expected with the approaching front at KDRT. Additionally, expect VFR conditions to continue through the majority of the night before deteriorating with MVFR to IFR ceilings and visibility. Winds will trend northeasterly at around 5 knots through Sunday morning before becoming more variable as winds at KDRT will gradually shift more east then east-southeasterly in direction during the afternoon. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 61 68 59 73 / 60 20 10 10 Austin Bergstrom Intl Airport 61 70 59 74 / 70 30 10 10 New Braunfels Muni Airport 63 70 60 76 / 70 30 10 10 Burnet Muni Airport 58 65 56 70 / 50 10 0 10 Del Rio Intl Airport 61 73 62 77 / 10 10 10 0 Georgetown Muni Airport 60 67 57 72 / 70 20 0 10 Hondo Muni Airport 62 73 60 75 / 40 10 10 10 San Marcos Muni Airport 62 71 60 75 / 70 30 10 10 La Grange - Fayette Regional 64 72 60 76 / 70 50 0 10 San Antonio Intl Airport 62 71 60 74 / 60 20 10 20 Stinson Muni Airport 64 72 62 76 / 60 20 10 20 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term...Brady Long-Term...29 Aviation...Brady
Area Forecast Discussion
National Weather Service Marquette MI
646 PM EST Sat Dec 10 2022 .SHORT TERM...(This evening) Issued at 318 PM EST SAT DEC 10 2022 Radar returns are starting to intensity across Upper Michigan as a negatively-tilted trough continues its eastward propagation into the Upper Midwest. Light snow is currently being reported across the western half of the UP, and this is expected to become more widespread over the next several hours during a period of frontogenetical forcing. A lack of moisture and significant forcing should limit snowfall amounts with projections still in the 1 to 2 inch range through the evening. Meanwhile, temperatures across the area are generally in the upper 20s/low 30s with light and variable winds. .LONG TERM...(Sunday night through Saturday) Issued at 409 PM EST SAT DEC 10 2022 Light snow continues to spread in this afternoon courtesy of weak warm advection ahead of an approaching shortwave (currently analyzed in RAP analyses over MN). ASOS sites across the far western UP and in northwestern WI have been reporting visibility below a mile at times, with an initial band moving through right now showing decent reflectivity around 20 to 30dbz. So, while snow is for the most part fairly light, with guidance continuing to come in below an inch for most of the area, would not be surprised to see some higher embedded totals closer to or even in excess of an inch especially across the western UP. Snow largely tapers off west of M-95 by 06Z, and continues to wrap up across the eastern UP through 12Z. However, as winds shift more northerly behind the exiting shortwave, we may continue to see some lingering lake effect flurries or light snow showers especially across portions of Marquette and Alger counties through Sunday. After light snow tapers off tonight/Sunday, surface high pressure building over James Bay will bring about dry weather at least through early Wednesday. However, light winds and mild lake temperatures result in a persistent marine layer (shallow moisture to 2-3kft) and associated low-level cloudiness, except across the far east where downslope flow limits cloud cover. Above normal temperatures prevail through the extended forecast period, except across the east where less cloud cover allows for more efficient nocturnal cooling and near normal daily average temperatures. The overall trend toward a slower system continues with precip onset possibly holding off well into Wednesday morning. Heights continue to rise over our region through the beginning of the work week. Meanwhile, a deepening low pressure system over the Plains will become vertically stacked by Tuesday night/early Wednesday. Guidance continues to struggle to bring this much farther east with the ridge firmly overhead and seeming to suppress this Plains system further southward as it tries to track towards the Great Lakes. The low center decays slightly Wednesday and deepens again over IN by early Thursday. This feature then slowly moves eastward towards the Atlantic coast through the end of the work week. Since this low pressure track is not close to our area, several rounds of light to moderate precip seem most likely. The first round of precip Wednesday into Wednesday night will be forced by strong southeasterly warm air advection, but very dry low levels (pwats ~0.10") delay onset and reduce overall amounts. Additional rounds of lake enhanced or pure lake effect precip are possible late next week as low level flow backs northerly. However, 850mb temps aren`t cold (median values of -4C to -7C) so precip amounts should remain light. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 646 PM EST SAT DEC 10 2022 Weak warn air advection continues to spread snow across the area, but is beginning to come to an end over the far west. Varying conditions across the area late this afternoon with KIWD with VFR ceilings and visibilities, while KCMX is LIFR and KSAW is low end MVFR. Ceilings will fill back in at KIWD over the next few hours, and there may be some minor restrictions to visibilities due to BR, but the snowfall should be done there. KCMX will see ceilings lift a bit into IFR/low MVFR over the next few hours as the snowfall there also tapers off before ending around 6Z. Ceilings and visibilities at KSAW will become IFR later this evening as the snow will persist there into the early morning hours. not se && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 409 PM EST SAT DEC 10 2022 Southeast winds fall below 20 knots this evening as surface ridging builds over Lake Superior. Light winds persist through Monday night, then east-southeast winds increase up to 25 knots. ESE winds increase up to 30 knots by late Tuesday evening and winds stay elevated Tuesday night through Wednesday. During that time frame, a period of low-end gales is possible. Winds weaken below 30 knots Wednesday night and back northeasterly on Thursday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...TDUD LONG TERM...LC AVIATION...RJT MARINE...LC
Area Forecast Discussion
National Weather Service Pendleton OR
408 PM PST Sat Dec 10 2022 .UPDATE... Based on the latest observations and forecast trends, we have dropped all current winter weather and wind headlines for the today/this evening period. The only winter weather advisory in effect is for central Oregon for later tonight into Sunday for the next system. Will take a look at the data and see if additional headlines will be needed. && .PREV DISCUSSION... /issued 315 PM PST Sat Dec 10 2022/ UPDATED AVIATION DISCUSSION... SHORT TERM...Tonight through Monday night...A challenging forecast presents itself as guidance is struggling with the placement of crucial mesoscale features, and still exhibits some slight, but important, differences in the synoptic pattern. The main upper-level, cut-off low is visible just offshore in water vapor imagery and continues to slowly track southeast. The main surface low is visible on both visible and Day Cloud Phase satellite products, located offshore in the northeast Pacific and also tracking slowly southeast. Ensemble and deterministic guidance are in excellent agreement that these features will both track southeast through the night with the surface and parent upper lows both gradually filling in as they approach the southwest Oregon coast. By 06Z tonight, some subtle placement differences become apparent in current 12-18Z deterministic guidance as well as 12Z ensemble mean 500 mb heights and vorticity. All guidance agrees on diffluent southerly flow aloft, but exact location of the mid-level vorticity maximum remain slightly different among guidance. Moreover, deterministic runs are hinting at a secondary surface low forming in south-central or southeast Oregon overnight into Sunday morning. Model-to-model and run-to-run variances are quite significant with the NAM favoring a more westward placement in central Oregon while the HRRR tracks this feature much further east into southeast Oregon. Of concern, the ECMWF EFI paints a bullseye for climatologically unusual precipitation and snowfall right over central Oregon with positive Shift of Tails (SoT) exceeding values of 1 indicating some extreme outliers among ensemble members. Indeed, delving further into ensemble members reveals substantial uncertainty in precipitation totals and snowfall for much of central and eastern Oregon, dependent upon where the secondary surface low tracks and where the band of heavy precipitation sets up. The takeaway is that forecast uncertainty remains notably high for such a short lead time, and impacts from the moderate to heavy snow band will be moderate to high, wherever it forms. For now, confidence in advisory-level snowfall for central Oregon has prompted a Winter Weather Advisory for 06Z Sunday to 06Z Monday, though other areas of north-central Oregon through the foothills of the Blue Mountains and into the eastern mountains may also see impactful snowfall through Monday as wraparound snow showers linger. Monday and Monday night, the upper low is anticipated to track southeast into the Great Basin with the heaviest precipitation tapering off through Monday afternoon in northeast Oregon. Colder air will be advected into eastern Oregon and eastern Washington as flow aloft turns northerly. Plunkett/86 LONG TERM...Tuesday through Saturday... A transition back to completely dry conditions will be well underway to start the extended period on Tuesday as the focus shifts to a stable but cold weather pattern through the end of the week. The ECMWF Extreme Forecast Index highlights these below normal temperatures for the inland Pacific Northwest, but doesn`t point to much else in the way of unusual weather features. Primary impacts will be in the form of low stratus and freezing fog centered over the Columbia Basin which may lead to localized slick road conditions. On Tuesday deterministic and ensemble guidance are in good agreement in the overall upper-level pattern into the middle of the week as the axis of a broad long-wave trough continues to progress eastward through the Rockies and a ridge of high pressure amplifies off the coast of the Pacific Northwest. Dry northerly flow aloft prevails overhead leading to completely dry conditions across the CWA. A more impactful byproduct of this northerly flow is the reinforcement of cold air over the region advecting southward from British Columbia leading to well below normal temperatures throughout the inland Pacific Northwest midweek; -4 to -8 C 850mb temperature anomalies by Wednesday. Expect high temperatures in the 20s across the Columbia Basin into Central Oregon, the John-Day Basin, and Grande Ronde valley Wednesday afternoon. Additionally the fairly tight temperature spread between the 25th and 75th percentiles in the NBM ensemble adds confidence to projected below normal temperatures Tuesday through Thursday and beyond. Outside of the cold temperatures at the surface, model soundings from the deterministic GFS and ECMWF indicate the development of a boundary layer temperature inversion come Tuesday/Wednesday as well, which combined with near surface moisture would facilitate persistent low clouds and freezing fog throughout the Columbia Basin up into the peripheral foothill areas into the end of the week. Where freezing fog is present slick road conditions follow. This will be especially true in some of the aforementioned peripheral foothill areas just above the base of the stratus deck like the Horse Heaven Hills and portions of US-97/197 where freezing fog appears most robust. Guidance begins to diverge further in the progression of the upper- level pattern towards the end of the week, having ramifications for potential precipitation chances and temperatures changes going forward. Come Thursday a “Rex-block” is very likely in place over the eastern Pacific due to a strong area of high pressure off the coast of British Columbia and vertically stacked upper-level low off the coast of California. Although, it is worth noting there is some ensemble disagreement on the exact placement of the above features. Locally this should continue to keep conditions dry however a shortwave dropping southward along the British Columbia/Alberta boarder into Idaho and Montana Thursday is worth keeping an eye on. Exploring the Ensemble Cluster Analysis reveals uncertainty in the placement of this feature although most solutions keep it far enough to our east to avoid any impacts. Still, nearly 22% of the total grand ensemble members nudge it westward enough for light snow shower to potentially move into the northern Blues and Wallowas. In either case, guidance continues to trend high and low temperatures even lower into the first half of the weekend; nearly 10-20 degrees below normal across the region come Friday and Saturday. Schuldt/99 AVIATION...00Z TAFs...Mostly VFR conditions continue the rest of the afternoon into the early evening hours although YKM may see CIGS/VSBY fall back to MVFR quicker than other sites due to increasing low clouds and mist. As the night progresses conditions deteriorate to MVFR and IFR at the rest of the airport sites as CIGS and VSBY lower. At BDN and RDM, a band of snow swinging northward from California arrives near 14z although there still uncertainty as to the exact timing of this precipitation. LIFR can’t be ruled out at two aforementioned airports but confidence in the timing/placement of heavier snow in central Oregon remains low Sunday morning. Breezy winds at KPDT, RDM, BDN, and ALW continue to decrease this evening, becoming lighter overnight. 99 && .PRELIMINARY POINT TEMPS/POPS... PDT 28 35 28 35 / 30 60 50 20 ALW 30 37 29 35 / 30 50 40 20 PSC 30 35 28 34 / 20 40 30 10 YKM 25 38 21 37 / 20 40 10 0 HRI 29 36 29 36 / 30 50 50 10 ELN 25 38 25 37 / 20 30 10 0 RDM 25 36 21 36 / 50 70 40 0 LGD 30 38 29 33 / 40 60 60 30 GCD 27 37 26 35 / 40 60 60 20 DLS 34 42 32 41 / 50 70 30 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory from 10 PM this evening to 10 PM PST Sunday for ORZ511. WA...None. && $$ SHORT TERM...77 LONG TERM....99 AVIATION...99