Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/18/21

National Weather Service Hastings NE
643 PM CDT Sat Apr 17 2021 .DISCUSSION...(This evening through Saturday) Issued at 307 PM CDT Sat Apr 17 2021 Biggest forecast concern is the chance of snow coming Monday night. Ongoing sprinkles/showers, focused more west, should diminish by evening as deep layer moisture wanes and shortwave trough axis within a mean synoptic trough shifts south/southeast of the area tonight. A particularly shallow and steep inversion is forecast by model soundings for tonight. Shortwave ridging within the mean synoptic trough in place over the central/eastern United States should stave off any precipitation and help boost temperatures a bit, although probably still a tad below normal as we continue to be under the influence of the cool synoptic scale trough. A surface cold front is forecast is widely forecast to come through Sunday night, passing through the tri-city area shortly after midnight give or take a few hours. Some minor timing differences among models, with the HRRR and GFS being a bit faster than the NAM solution, but effectively bringing in cold air advection late Sunday night, in time to make Monday exceptionally cold for this time of year, topping out only in the lower 40s at best for the tri-cities, with somewhat cooler temps to the north and a tad warmer to the south. There will be a chance of post-frontal precipitation to develop during the day on Monday, mainly on the Nebraska side as a band of enhanced 700 mb frontogenetic forcing is expected to develop within a 700 mb trough as there is widespread agreement in the model world of this development. Temperatures during the day should keep precipitation primarily as rain. The 700 mb frontogenetic forcing gathers strength by Monday night as it slips to the south across north central Kansas. This is also widely accepted among model solutions. Models and ensembles are also in decent agreement that as temperatures cool, snow amounts will probably top out in the 1-3 inch range for north central Kansas, given the relatively small window to work with. Ensembles indicate that precip may hold over a bit into early morning Tuesday compared to a bit of an earlier shutoff by operational runs, but besides this, models and ensembles seem to be in decent agreement with the upcoming scenario and the associated snow amounts. Although GFS has shifted a bit farther north with heavier qpf, the ECMWF has shifted south and backing off qpf. The NAM indicates a tighter band, with qpf closer to the ECMWF. Forecast has backed off a bit into the 1-2 inch range, and given the time of year, I am not inclined to hold on to very high amounts, especially this far out, given overall ensemble and operational model solutions. The upper wave does not completely clear until after Tuesday, so I did put in some sprinkles for Tuesday afternoon with increasing low-level lapse rates. Overall upper air ridging into mid-late week next week finally returns us to near normal for temperatures by next weekend. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday) Issued at 638 PM CDT Sat Apr 17 2021 We have a few showers primarily around Kearney at forecast issuance time. These showers will quickly die off after sunset with a dry night expected. Ceilings have been rising and we expect VFR conditions throughout the remainder of the TAF valid period. The wind will shift from northerly at TAF issuance time to westerly winds by late tonight into tomorrow morning. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Heinlein AVIATION...Wesely
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
955 PM EDT Sat Apr 17 2021 .SYNOPSIS... High pressure builds back into the area through this weekend. An area of low pressure will move through on Monday. A strong cold front moves through the area late Wednesday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... As of 955 PM Saturday...Fast zonal flow aloft leading to a decent amount of mid and high level clouds across eastern NC. While the layers below 700 mb remain fairly dry, the combination of some mid-level energy moving east through the zonal flow aloft and a weak frontal trough over the area could kick up some very light showers or sprinkles overnight. The HRRR and 3km NAM continue to some isolated light showers or sprinkles over the central and northern tiers of the CWA primarily and will leave the very low PoPs in those areas overnight. With cloud cover will help hold low temperatures in the 50 to 55 degree range overnight. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... As of 340 PM Sat...Upper heights build slightly over the region with skies clearing on the backside of the shortwave. Main challenge for tomorrow is the possibility of a few isolated shallow showers along the seabreeze. More hi-res guidance has latched onto this idea and held an isolated shower mention for the afternoon, predominantly along and east of Highway 17. Raised forecast highs a couple degrees tomorrow with plenty of sun around during the day, and also considering 12z forecast low-level thicknesses initialized a bit lower than this morning`s sounding observation. Low to mid 70s expected, with mid 60s for OBX. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... As of 245 AM Sat...A cold front will remain stalled to the south through the middle of next week, with weak areas of low pressure strengthening along it. A strong front will push through the area Wednesday afternoon, with much cooler air behind it. Sunday night through Tuesday...Front will remain stalled to the south through mid week as waves continue to develop along it. Weak low pressure and shortwave energy aloft will be enough to support scattered showers and iso tstms Monday, and increased pops a bit. High pressure will build in briefly Monday night and Tuesday, then pushing offshore late Tue ahead of the next front. Increased pops Tue slightly from previous forecast. Gradual warm up through early next week, with highs back into the 70s inland and upper 60s for the Outer Banks Mon and Tue. Wednesday through Friday...Stronger front is progged to push through late Wednesday, as waves of low pressure continue to move along the stalled front offshore. 00z guidance in better agreement with respect to timing, pushing the front offshore by early Wed evening. Increased pops a bit from previous forecast but still looks like it becomes a bit moisture starved moving east of the Appalachians. Will keep sc tstm mention Wed afternoon with modest instability and strong shear (50+ kt bulk shear). Much cooler and drier airmass expected behind the front with high pressure building in from the WSW and upper troughing. We could have some Frost/Freeze concerns inland Thursday morning. EC/GFS mos guidance show lows falling into the low to mid 30s. Lowered temps a few degrees, but not quite that low yet. Highs Thu generally in the 60s with dewpoints falling into the 30s. Another cool night Thu night, with highs warming into the mid 60s to low 70s Fri. EC and CMC have a strong storm system impacting the area next weekend, but still 7 days out. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Short Term /through 00Z Monday/... As of 715 PM Saturday...VFR conditions expected at all the TAF sites through this cycle. Some mid and high level cloudiness associated with some mid-level shortwave energy channeled in a zonal flow will persist overnight. This energy along with a weak frontal trough over the area will lead to a small chance of some isolated showers or sprinkles, but not enough to include in the TAFs. Scattered to broken mostly mid clouds will persist on Sunday. Long Term /Sunday night through Wednesday/... As of 245 AM Sat...Pred VFR conditions expected through the period. Scattered showers and isolated tstms are possible each day, mainly diurnally driven, which could briefly reduce conditions to sub- VFR. && .MARINE... Short Term /Tonight and Sunday/... As of 955 PM Saturday...Little change needed to the marine forecast on this update. Winds at late evening as SE at 5 to 10 knots for the most part, with a few gusts to around 15 knots over the northern tier. Seas are checking in at 2-3 feet with 11-12 second swells. Winds veer southwesterly overnight at 5-10 kts and then back to the north as another weak front drops across the waters overnight. Bit of divergence in the intensity (or even existence) of a post- frontal surge and shot the forecast down the middle of guidance, favoring northerly winds at around 10 kt. Sea breeze regime seen today will be in place again tomorrow. With such little impactful wind, seas remain at 2-3 feet through the short term with periods of 10-12 seconds. Long Term /Sunday night through Wednesday/... As of 245 AM Sat...Front will remain stalled to the south through the period as weak waves of low pressure move along it. Fairly quiet wx expected across the waters the next few days, but expect many wind shifts with stalled front and weak lows in the vicinity. Winds generally 5-15 kt through Tue with seas 2-4 ft. A strong cold front will approach the waters Wednesday, pushing through Wednesday afternoon and early evening. SCA conditions likely to develop Wed afternoon with gusty SW flow ahead of the front, then stronger NNW winds 20-25 kt and seas 4-7 ft developing behind it. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...None. MARINE...None. && $$ SYNOPSIS...MHX NEAR TERM...CTC SHORT TERM...MS LONG TERM...CQD AVIATION...CTC/CQD/MS MARINE...CTC/CQD/MS
Area Forecast Discussion...updated
National Weather Service Portland OR
835 PM PDT Sat Apr 17 2021 ...Updated aviation discussion... .SYNOPSIS...An unusually warm and dry stretch of weather for April will likely continue for much of the upcoming week, but there is a decent chance cooler and wetter weather will return towards next weekend. && .SHORT TERM...Tonight through Monday night...Water vapor satellite imagery this afternoon reveals an area of upper level high pressure centered over the far northeast Pacific near western Washington and Vancouver Island. A broad shortwave trough encompasses much of the eastern Pacific while another shortwave trough is currently cresting the upper level ridge across northern British Columbia and will slide southward down the east side of the Rockies over the coming days. Surface observations indicate temperatures have climbed to near 80F along much of the north Oregon and south Washington coastline and across much of the lowlands of interior northwest Oregon and southwest Washington. Expect an additional couple degrees of warming this afternoon with several record high temperatures for April 17th in jeopardy including those at Portland, Hillsboro, Troutdale, Salem and Eugene. Relative humidities have once again plummeted into the teens and twenties across many interior valley and foothill locations this afternoon. However, pressure gradients have decreased substantially across the area, and as a result, winds have generally remained 10 kt or less. Nonetheless, fire danger will remain elevated through Sunday, particularly for the time of the year as fuels remain unusually dry for this time of the year and relative humidities remain low during the afternoon hours. Visible satellite imagery or just looking out the window reveals a beautiful, not a cloud in the sky kind of day across most of northwest Oregon and southwest Washington this afternoon. The main exception to this remains along the central coast of Oregon between Florence and Depoe Bay where fog and low clouds continue to hug the coastline. Expect these clouds to spread back onshore between 3-5 PM before gradually spreading northward along the coast overnight. Latest HREF, RAP and NAM guidance suggests the fog and low clouds tied to this southerly wind reversal should reach the mouth of the Columbia River by daybreak and likely spread northward along the Washington coast Sunday morning. Meanwhile, the GFS and UW-WRF are generally much more pessimistic with regards to clouds and keep our coastal areas clear into Sunday morning. Given the former guidance is handling the current fog and low clouds vastly better than the GFS and UW-WRF, opted to trend the cloud cover forecast towards more clouds for the coast through Monday. Models are in good agreement the area of upper level high pressure currently over the region will weaken this weekend as a lobe of the aforementioned shortwave trough in the eastern Pacific slides eastward towards the Pacific Northwest on Monday. Several members of the GEFS and EPS ensemble systems produce measurable rain across portions of our CWA late Monday into Monday night, particularly our southwestern zones around Lane, Lincoln and Benton Counties. This appears to be in response to these models developing an area of elevated convection due to negative thetae lapse rates between 700- 500mb and large scale lift occurring along the leading edge of a PV anomaly. NBM PoPs are still generally 10% or less across these zones late Monday, but opted to at least put in a slight chance mention of sprinkles given the pattern. The latest operational model soundings do not appear terribly favorable for measurable precipitation reaching the ground so do not see a big reason to argue with the current NBM PoPs. /Neuman .LONG TERM...Tuesday through Friday...Mostly dry and warm weather through the middle of next week as high pressure dominates west of the Rockies. Temperatures will slowly lower around 10-15 degrees through Friday. Within the flow around the high pressure, a shortwave with a weak upper level low will pass over the area Tuesday morning. Some models are showing a brief period of showers but ultimately not expecting a lot of accumulation. This system has eroded over time as well so confidence with it`s manifestation is marginal as it easily could be impacted by the dry airmass. The stubborn high pressure and dry air mass looks to start shifting east and being eaten away by a broad area of low pressure dropping down from the north Pacific. The low has quite a bit of consistency among models even this far out. The main impact this low may bring some long waited precipitation towards the end of the week. The main challenge is the timing and whether or not the incoming low pressure will be deep enough to "push" the high pressure out of the area. -Muessle && .AVIATION...A dry air mass will keep inland areas of northwest Oregon and southwest Washington with VFR flight conditions through the next 24 hours. Along the coast winds are expected to switch around to a light south-southwest wind tonight and Sunday, which will result in marine air with low clouds and fog spreading north up the coast. KONP is likely to see IFR conditions developing early tonight by 06Z, then a good chance of IFR conditions persisting through the day Sunday. Further north the chances for IFR conditions in low clouds and fog begin as early as late tonight, but the best chances for IFR conditions reaching KAST don`t come until daylight hours Sunday after 16Z. For detailed regional Pac NW aviation weather information, go online to: KPDX AND APPROACHES...VFR conditions for the next 24 hours. && .MARINE...Rather benign conditions will continue through the weekend with generally light northwesterly winds across the waters and seas 4 to 5 feet into Sun morning. Near the Oregon coast there is a good chance of a southerly wind reversal as marine stratus and areas of fog push northward Sun morning. Onshore westerly winds are likely Sun afternoon up to 10 kt before turning northwest again late. Surface high pressure builds northward Monday while thermally induced low pressure returns over northern California early next week. The increased pressure gradient across the coastal waters will result in increasing northerly winds with low end Small Craft Advisory gusts of 25 to 30 kt most likely late Monday through Tuesday. Seas are also likely to climb into the 6 to 8 ft range Tue into Wed and be somewhat choppy. Seas will likely fall to below 5 ft and winds decrease during the latter part of next week. Some weather models suggest that by next weekend a storm system could bring increasing southerly winds and seas next weekend, but confidence in the details, is relatively low at this time. /DDH && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ Interact with us via social media: