Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/29/20

Area Forecast Discussion
National Weather Service Bismarck ND
1010 PM CDT Wed Oct 28 2020 .UPDATE... Issued at 953 PM CDT Wed Oct 28 2020 With this update we trimmed up PoPs and adjusted precip type based on 00Z forecast soundings and new high-res guidance coming in. Overall the changes made resulted in a slightly slower onset time, especially in the southern half where forecast soundings are slow to saturate until around 18Z or after. Additionally, recent forecast soundings show a relative clean transition from snow to rain for most areas. The exception being the northwest, with RAP soundings showing a brief period of overlap between possibly enough saturation and a lingering warm nose to produce some very light freezing rain around 12Z to 15Z. This is also supported by the incoming 00Z HREF precip type product. Stratus across central has expanded southeast into James River Valley area, though eroding on the west edge. We bumped up lows slightly in the north-central where stratus should persist the longest. Additionally, with the surface high stretching over eastern North Dakota fog may develop where there is still snowpack in southeast North Dakota. With the expansion of stratus into this area there is enough uncertainty to leave out fog for now, but this will need watching. UPDATE Issued at 637 PM CDT Wed Oct 28 2020 Updates were made to extend sky grid coverage for persistent stratus across northern North Dakota, which guidance is handling relatively poorly. This may impact lows tonight, with forecast lows around or below currently observed surface dew points. We`ll continue to monitor sky cover trends in the near term before beginning to adjust temperatures tonight. No adjustments needed at this time to tomorrow`s precipitation. && .SHORT TERM...(This evening through Thursday night) Issued at 220 PM CDT Wed Oct 28 2020 At the surface, a backdoor cold front will continue to drift slowly south and west through the rest of the day before stalling/washing out and becoming more of a stationary front. This will setup a weak baroclinic zone from the far northwest corner of the state, southeast along the Missouri River and then east to the southern James River Valley. North and east of this boundary will see slightly cooler temperatures through the short term than west and south. Subtle ridging will quickly move across the state tonight embedded within northwest flow aloft ahead of an approaching weak shortwave/Alberta Clipper. As this system approaches, clouds will once again be on the increase and precipitation chances will start to develop across the far northwest Thursday morning (mainly as light snow) as the wave interacts with the baroclinic zone. This baroclinic zone will transition back to more of a warm frontal zone and will start to drift north and east as the precipitation spreads south and east along it. As we move into the afternoon, temperatures will warm enough to change precipitation to a mix of light rain and snow before transitioning briefly to a wintry mix of light rain/snow/freezing rain/sleet across portions of the Turtle Mountains and James River Valley before it exits the area tomorrow evening. Along and east of the baroclinic zone, expect a trace to maybe a little over an inch of snow accumulation with the highest totals across the Turtle Mountains and the James River Valley. QPF will generally range from a trace along the western edge of the precipitation to a couple tenths of an inch east. Temperatures will be a bit cooler on Thursday than today almost everywhere except for the far west central and southwest (on the warm side of the boundary) but weak warm air advection will once again be on the increase through the day. Clouds may start to decrease overnight Thursday night as upper level ridging and high pressure starts to nudge in. .LONG TERM...(Friday through Wednesday) Issued at 220 PM CDT Wed Oct 28 2020 Dry conditions, warmer temperatures, and a windy Saturday highlight the long term forecast period. An upper level ridge axis moves overhead on Friday, bringing with it more warm air advection and a mostly sunny sky over all but the Turtle Mountains and James River Valley. High temperatures will range from mid 30s northeast to near 50 across parts of the southwest. Expect breezy southerly winds Friday afternoon ahead of another Clipper and shortwave trough/cold front. The cold front will sweep across the state overnight Friday into Saturday morning as the surface low remains north of the International border. All guidance continues to keep the passage of this front dry, but wouldn`t be surprised if we end up seeing some spotty light rain and/or snow showers by the time it gets here. After the Clipper passes, gusty winds will develop out of the northwest on Saturday. At the moment, sustained winds up to 30 mph and gusts to 45 mph seem reasonable and the expectation is that we will at least need a Wind Advisory at some point in future forecast shifts. With evening forecast temperatures to range from the mid 20s to lower 30s on Saturday, this will lead to apparent temperatures dipping into the upper single digits above zero north to the teens elsewhere. Thus a brisk and chilly Halloween evening is likely across all of western and central North Dakota. We will go ahead and start messaging the potential of wind headlines in the Hazardous Weather Outlook. Its likely to remain a bit breezy in places overnight into Sunday morning but winds will likely shift to the west/southwest and relax during the afternoon as warm air advection once again moves across the state. Thus, temperatures will rebound slightly on Sunday before warming more for the start of the work week, with forecast highs in the widespread 50s Monday through Wednesday. CIPS analogs would suggest that 60s may also be possible across much of the west and central during this time frame but its still a ways out for high confidence and quite a bit of spread remains among the various ensemble members of the GFS and ECMWF. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 637 PM CDT Wed Oct 28 2020 Generally VFR conditions this early evening, before increased low level cloud cover is expected with a clipper arriving Thursday. Mostly widespread MVFR with pockets of IFR ceilings expected, especially at KMOT-KBIS-KJMS. Rain or snow is expected to develop between 15Z to 18Z at KMOT and possibly between 12Z to 15Z at KXWA, though less certain. Light rain and snow transitions east after 18Z. Breezy winds, gusting up to 25 kts, shift from south to west through the afternoon and evening. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AE SHORT TERM...ZH LONG TERM...ZH AVIATION...AE
National Weather Service Eureka CA
248 PM PDT Wed Oct 28 2020 .SYNOPSIS...Dry weather is expected through early next week. Above normal afternoon temperatures are expected each day, after chilly mornings and patches of early morning frost in some of the interior valleys. Skies will generally remain clear except for occasional coastal clouds and possible fog through the weekend. && .DISCUSSION...Upper level ridging will dominate through Friday. Above normal afternoon temperatures are expected in the interior for at least one more day. The dry air mass and clear skies will allow temperatures to fall into the mid 30`s in some of the valleys of southern Humboldt and northern Mendocino again tonight. A frost advisory has been issued for these colder valleys. It will be colder in Trinity county valleys, however many sites have already seen a season ending freeze. Frost advisories and freeze warnings will no longer be issued for Trinity county until Spring. A transient shortwave disturbance will move across the Pacific NW on Friday and temporarily flatten the ridge. This shortwave will likely induce a low level push of higher humidities for coastal areas and adjacent river valleys as high pressure rebuilds offshore behind the disturbance. Satellite imagery has already been showing low clouds and possible fog forming offshore and along the southern Mendocino coast this afternoon. The offshore gradients tonight will likely keep the bulk of the low clouds over the coastal waters. BUFKIT time-height sections for coastal land sites were not showing a considerable increase in low level humidity and low clouds tonight and Thu. Just offshore, profiles moisten up tonight and Thu, suggesting a greater potential for low cloud cover along the Mendocino coast through Thursday. Otherwise, inland areas will remain quite dry through the weekend. A few upper level stations were still reporting 5 to 10% RH`s today. The RH`s were higher, 15-25%, at stations with stronger winds, gusts from 20 to 30 mph. Locally critical fire weather conditions are expected for the windier sites, due to the very low RH`s. Widespread and long duration red flag conditions are not expected, however. A marine push may result in higher RH`s this weekend, however the highest mountain peaks will probably not see any significant RH increase. The ridge aloft will spring back up quickly this weekend, for generally warmer daytime temperatures in the interior. Another transient shortwave will move into the ridge early next week, around Tuesday. Rain appears unlikely, however will leave a 15-20% chance for a few hundredths. && .AVIATION...Visible satellite imagery continues to show some stratus developing off the Mendocino coast and more off the SF Bay area. Winds are expected to remain light through the period. Late tonight the HREF is showing some stratus near the coast of Humboldt and Del Norte counties. HRRR has been progressively brining more stratus closer to the coastal terminals in the early morning hours with local southerly return flow in recent runs. However, the airmass is still relatively dry with light offshore flow expected at times. Nevertheless, the 0Z TAFs may need more stratus. && .MARINE...Winds and seas continue to relax, with the remaining Small Craft Advisory in the Northern Outer Waters now expired. Light northerlies will settle in for most of the remainder of the week, with periods of coastal southerly return flow. Small mid-period NW swells will linger in the waters until a longer period NW swell builds in beginning early Saturday morning. Forecast data continues to trend a little higher with it, to likely reach 7 feet at 11 seconds on Saturday. The northerlies will pick back up starting Friday, and potentially remain elevated Saturday. Late Sunday afternoon a long-period WNW swell will begin filling in, and will build to around 4 to 5 feet at 16 seconds by Monday morning. This could pose a sneaker wave threat depending on how strong the winds and short periods waves are at this time. && .EKA WATCHES/WARNINGS/ADVISORIES... CA...Frost Advisory from 3 AM to 8 AM PDT Thursday for CAZ104-106-110- 111. NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 3 PM PDT this afternoon for PZZ470. && $$ 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 North Platte NE
728 PM CDT Wed Oct 28 2020 .SHORT TERM...(This evening through Thursday night) Issued at 315 PM CDT Wed Oct 28 2020 Main concern tonight through Thursday morning will be the development of stratus and patchy fog. Surface high pressure will become centered over western NE tonight as stratus develops westward over the area overnight. Light winds and weak cold air advection, with residual near surface moisture from today`s snow melt will contribute to fog formation. This is supported by the latest 15Z SREF, but not well supported by the latest HRRR and RAP. That being said, limited mention of fog to patchy. Stratus looks much more prevalent than the fog at this time. On Thursday, surface low pressure will develop across the western Dakotas and Nebraska panhandle. The stratus and patchy fog will lift from west to east during the morning. Southwesterly winds will also develop for areas near and west of Highway 83. Areas in the northeast will clear out last, with poor mixing. Highs will range from the low 40s northeast to the low 50s west. A weak cold front will move in Thursday night with clear skies. .LONG TERM...(Friday through Wednesday) Issued at 315 PM CDT Wed Oct 28 2020 Dry conditions Friday through next Wednesday. An upper trough will move through the Northern and Central Plains Friday night through Saturday. This will bring a cold front through the area on Saturday. Highs Friday and Saturday will mostly range in the upper 40s to mid 50s, then slightly cooler in the mid 40s to lower 50s Sunday. Monday through Wednesday, an upper level ridge across the western U.S. will flatten out and move east. Geopotential heights at 500mb will remain above normal around 580dm. The Polar front will also retreat well north across the northern Canadian Prairies during this time. the NBM forecasting highs in the 60s to low 70s, with the latest GFS and ECMWF suggesting further upside into the 70s possible. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 721 PM CDT Wed Oct 28 2020 Low ceilings (MVFR/IFR) are expected to develop after midnight tonight and last until about mid morning Thursday. This is primarily expected to be along and east of HWY 83. VFR is expected all areas by Thursday afternoon. Winds will be light, generally 10 kt or less. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Roberg LONG TERM...Roberg AVIATION...Taylor
Area Forecast Discussion
National Weather Service Marquette MI
634 PM EDT Wed Oct 28 2020 .SHORT TERM...(This evening through Thursday) Issued at 342 PM EDT WED OCT 28 2020 Latest RAP analysis, and GOES Satellite show a weak, closed surface low of about 1003mb over southern Ontario from this morning and will continue to move across Ontario throughout the day, which will ease the tight pressure gradient from last night that brought the gusty southwest winds. So far, drier low level air mass is keeping any precipitation from reaching the ground but as we continue into the rest of the day, low level moisture will increase, mainly across the north and western parts of Upper Michigan with another shortwave moving through today and tonight. This shortwave will have just enough lift and fgen to produce showers across the north half but can`t rule out an isolated shower or two across the south. Behind the shortwave, winds will turn to the north and having 850mb temps falling to about -10C, which will help initiate some lake-effect snow over the north wind belts. Not expecting much in the way of accumulation with maybe an inch at most in spots. Lingering light snow showers will continue through Thursday afternoon before clearing out by Thursday night. Light rain showers, mixing in with snow over the Keweenaw, have begun to move in over the western UP this afternoon and will spread east through the rest of the evening, mainly across the north. These light rain showers will transition over to snow showers and with winds turning more northerly late tonight, lake-effect will take place over the north wind belts. These should not reach far inland as winds won`t help to sustain long LES bands and as mentioned from previous discussion, did cap ProbIce at 85 to keep mentions of freezing drizzle out of grids. In regards to the Lake-Effect snow potential late tonight into Thursday morning, a few of the Hi-res models, with the 12z GFS hinting that this as well, are hinting at a long fetch band setting up from about Nipigon Bay towards the Keweenaw Peninsula. If a band does set up, this could bring a couple inches of snow to the higher terrain areas over the north wind belts but not highly confident in this but worth mentioning. Winds will become light by Thursday night with precip clearing out. Temperatures this afternoon may be close to reaching maximum for the day but did blend in official and latest obs to better reflect temperatures this afternoon. Still thinking mid to upper 40s for the far south central. Thinking cloud cover will hang around and not have many breaks which will keep temperatures from falling too much tonight and have lows in the 20s in most spots and low 30s along the lakeshores. Behind shortwave, highs Thursday will be in the 30s with maybe a 40 near Menominee. .LONG TERM...(Thursday night through Wednesday) Issued at 404 PM EDT WED OCT 28 2020 Thursday night will usher in some pretty chilly overnight low temperatures, especially across the inland higher terrain where lows could easily dip below 15 degrees based off the radiational cooling from clear skies. Moderated temperatures along the lakeshores can be expected with temperatures staying 7 to 10 degrees warmer compared to the elevated terrain. Upper level ridging pattern begins to take hold over the CWA from Friday afternoon through Saturday. Dry conditions are anticipated at this time with the warming air mass aloft and subsidence down to the surface. Afternoon highs in the mid to upper 30s for Friday should be a nice temporary change of pace as the sun should make an appearance over the region by late afternoon across a majority of the region. Building clouds on Saturday will limit temperature maximums despite warm air advection pushing the afternoon highs approximately 10 degrees warmer compared to Friday. Temperatures at 700mb level on Saturday approach 0 to -2 Celsius. The main story for this Halloween weekend will be the shift from a warmer Saturday afternoon to a strong upper level shortwave trough impacting the weather Saturday night through late Sunday afternoon. At this time of analysis, tightening pressure gradients will enhance wind speeds across Lake Superior inland to the lakeshore areas upwards of 45 knots. Additionally, the lake effect regime will really come into focus as northwest winds will cause 1 inch per hour or higher snowfall rates in the most intense snow bands. The first period for snowfall will begin 6z-12z Sunday. Beach erosion looks plausible as the high end gale scenario unfolds from late Saturday night through Sunday. As the strong upper level shortwave trough pushes further east, a secondary upper level disturbance will create the opportunity for snow showers across the CWA again on Monday. Upper level ridging looks to take hold over the region allowing for moderated temperatures near 50 degrees by the middle of next week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 634 PM EDT WED OCT 28 2020 A shortwave will move through Upper Michigan this evening. This will bring mostly light rain showers around IWD & SAW with a mix of ra/sn to CMX this evening. Winds will gradually transition from westerly to northerly by tonight in the wake of the passing shortwave with -sn developing at CMX and SAW with lake-effect taking shape. MVFR conditions will continue through most of the forecast period, but there will be times at IWD and CMX overnight that will be IFR/LIFR with some upslope flow. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 342 PM EDT WED OCT 28 2020 Winds will continue to diminish through the rest of the afternoon, heading into Thursday and Friday mainly below 20 knots. Pressure gradient will ease as well with mostly westerly winds continuing over the lake heading into Saturday. Then attention will turn to Saturday afternoon into Sunday. Confidence has continued to increase with the potential for a high-end gale event with southerly gales to 35 knots over the east half Saturday afternoon first, then winds backing to the northwest with gales to 40 knots over the west half Sunday morning and high-end gales to 45 knots with a window of storm force gusts for several hours over the east half Sunday afternoon. Waves between 14-19 ft are certainly possible, given how long the storm force gusts last Winds will diminish to 20-25 knots by Monday morning. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JH LONG TERM...BW AVIATION...07 MARINE...JH
Area Forecast Discussion
National Weather Service Springfield MO
1057 PM CDT Wed Oct 28 2020 ...Updated for 06Z Aviation Discussion... .SHORT TERM...(This evening through Thursday) Issued at 227 PM CDT Wed Oct 28 2020 ..A Flood Watch is in effect until Thursday Evening.. Current GOES 16 WV satellite imagery depicts an upper-level closed low spinning into the Red River Valley of Texas. Meanwhile along the northern Gulf Coast, Hurricane Zeta is making landfall. A steady rain has lifted into southern Missouri this afternoon and will persist through the overnight hours as the upper- level low pivots into the Ozarks and a moisture-rich air mass glides isentropically into the region on a deep Gulf fetch. In glancing at the latest NBM probabilities and HREF runs, our confidence remains high that a swath of 1-3 inches of rainfall will spread across the entire area this evening into Thursday afternoon, with the higher amounts along and south of I-44. Some of the more recent runs from the HRRR and RAP suggest some isolated 3-5 inch maxima occurring somewhere along Missouri/Arkansas border. This should not be discounted given the anomalously moist airmass in place. Per climatology (GEFS M-Climate output), this airmass ranks above the 99th percentile for available moisture for this time of year. We are less confident in the impacts this heavy rainfall event will have. Despite a very dry summer and early fall, antecedent conditions have been wetted by rainfall that occurred this past Monday in locations south of I-44. With incoming rain expected to fall over a similar footprint, rises to creeks, small streams and low-water crossings could lead to some flooding. If nothing more, this rainfall event will alleviate the current drought conditions. Otherwise, synoptic wind gusts will increase late tonight into early Wednesday as Hurricane Zeta makes its extra-tropical transition and begins to phase together with the departing upper- level low. Occasional gusts to 35 MPH will be possible, mainly along the Ozark plateau. Rain will gradually end from west to east by Thursday evening as the upper-level low opens up and translates across the Tennessee Valley and a ridge begins to build into the region. .LONG TERM...(Friday through Wednesday) Issued at 227 PM CDT Wed Oct 28 2020 The pattern turns quiet by Friday as upper-level flow becomes zonal across the Plains. Temperatures should rebound to nearly 60 degrees as compressional warming across the front range advects into the area. Shortwave energy will dig into the Great Lakes region later this weekend. This will help drive a dry cold front through the Ozarks late Saturday night. Temperatures will be a little cooler on Sunday behind the frontal passage, but generally speaking, temperatures into next week look seasonal with daily highs near 60 degrees and overnight lows near 40 degrees as an amplified ridge builds across the Plains. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1057 PM CDT Wed Oct 28 2020 Widespread rainfall will continue through the overnight hours along with widespread IFR to LIFR flight conditions in both ceilings and visibilities. In addition northerly winds will pick up between 06Z-09Z with some gusts as highs 35 knots through the morning hours. These will begin to diminish by late morning. Flight conditions will also improve from west to east as the afternoon wears on eventually into VFR conditions by late afternoon. && .SGF WATCHES/WARNINGS/ADVISORIES... MO...Flood Watch through Thursday evening for MOZ082-083-088-090>098- 101>106. KS...Flood Watch through Thursday evening for KSZ097-101. && $$ SHORT TERM...Albano LONG TERM...Albano AVIATION...Raberding