Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/03/21

Area Forecast Discussion
National Weather Service Des Moines IA
546 PM CST Sat Jan 2 2021 ...Updated Aviation Discussion... .SHORT TERM.../Tonight through Sunday Night/ Issued at 202 PM CST Sat Jan 2 2021 Confidence: Medium to High Main challenge again tonight will be fog potential and the manner on how this all plays out has lowered the forecast confidence a bit. Though weak area of low pressure southwest of Iowa today will be backing in high to mid level clouds over the southeast this evening, there is little change in the overall light wind pattern and weak ridge of high pressure situated across the area. In fact, by 06z through 12z we are lift with nearly the same conditions over the region as this morning with just a bit of a push of warm air aloft from the west southwest. This warmer air aloft will likely strengthen the inversion over the west and along with the ridge, help to promote additional areas of fog overnight once again. The HRRR continues to be bullish with fog over the entire region again tonight. It was a bit overzealous last night, however. Overall, the same areas from southwest to north central and a bit farther east are likely to see fog again first tonight with a few spots taking longer for the fog to initially develop - most likely around the metro and areas east and southeast where dewpoint depressions remain larger late this afternoon. Will be issuing an advisory for all of the forecast area given that most, if not all should have some areas of dense fog by mid to late evening and through portions of Sunday. Fog is already backing into our area near Marshalltown and Waterloo. The ending time of the advisory is somewhat problematic, but given that today the thicker fog either never lifted or took to at least 18z... most of the surrounding offices and us decided to at least continue the advisory to 18z. It may actually take longer to lift tomorrow in some areas. Winds will remain light with little mixing Sunday and this will likely keep the fog around. Tonight lows will once again bottom out in the single digits and have lowered readings; especially in the east and in the river valley areas. Sunday is showing warming aloft by late day, but it may again be a challenge to burn off all the fog soon enough to bring highs up to expectation. Have made minor adjustments to the going forecast today and expect mid 20s east to the upper 20s/lower 30s central and south. By Sunday night, a more persistent push of warmer air will be directed into Iowa with light southwest surface winds as well as increasing southwest flow aloft. This should act to lessen any risk for areas of fog overnight into early Monday morning. Along with that, overnight lows will generally be in the upper teens to lower/mid 20s. .LONG TERM.../Monday through Saturday/ Issued at 202 PM CST Sat Jan 2 2021 Confidence: Medium With Decreasing Confidence by Wednesday Another in a series of weak, generally moisture starved waves will pass over the region early Monday morning. The only real impact will be a wind shift and a slightly near-neutral, cooler push of air across the north northeast for the day. Otherwise, slightly milder air will continue to move over the region from the west. The model guidance is beginning to shade highs into the 40s across the south for the day, but snow cover should cut back on afternoon readings somewhat Monday as melting increases. We continue this cycle between ridges/approaching weak troughs nearly every 24 hours through at least Tuesday morning. Though the impacts from large storms will be nil through Tuesday, we`ll probably have another chance at fog Monday night into Tuesday morning if sufficient melting occurs Monday night. Tuesday remains quiet ahead of the approaching system. Both the Euro/GFS area in some agreement to continue the warming trend with milder south winds keeping highs warmer into Tuesday. Looking into the midweek system next week still brings many challenges. A look at the last 3 GEFs packages` precip accumulation ensembles shows that the trends have been for 55%/40%/70% of runs showing central Iowa with higher accumulating qpf; so the trends are continuing to bounce around, but are increasing. The GFS has been holding onto an initial more northerly amplification of the wave- pair in the northern/southern stream while the Euro is trending to develop the southern wave initially faster, with more a split configuration across Iowa. Eventually, by 00z Thursday both models are favoring a low just south of Iowa but even then some differences in location will play a huge part in how much precipitation we receive. Along with the location, precipitation types will then need to be parsed out with time as well. Currently, the ensemble guidance supports some solutions with precipitation and will leave slight to chance PoP for now and continue to evaluate any trends in the next day or two. At least there is improving confidence as the system departs with another cold front approaching the region by Friday. Some differences remain in the amount of available moisture and expected light precipitation. The Euro is bringing across a bit more light snow than the GFS deterministic by Friday. Overall next week will be at or above normal for highs with only a slight cool down on Saturday. Normal highs range from the mid 20s north to the lower 30s south and the region will be averaging around 30 north to the mid to upper 30s in the south through the period. && .AVIATION.../For the 00Z TAFS through 00Z Sunday evening/ Issued at 546 PM CST Sat Jan 2 2021 Dense fog to continue at MCW and ALO and is expected to thicken elsewhere across central Iowa later tonight into Sunday morning. High confidence in the long duration LIFR visibility from the dense fog, just lower confidence when it`ll actually settle in over DSM, OTM and FOD this evening. Once it does thicken, it looks to linger for much of the Sunday morning and even MVFR visibility into the afternoon hours seems highly probable. Medium to high confidence in the IFR/LIFR ceilings as expect them to bounce between the two flight categories. && .DMX WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until noon CST Sunday for IAZ004>007-015>017- 023>028-033>039-044>050-057>062-070>075-081>086-092>097. && $$ SHORT TERM...REV LONG TERM...REV AVIATION...Podrazik
Minimal changes from the previous forecast discussion, with the
exception of increasing confidence of the timing of next weeks
storms system. Used mostly Pops from WPC with NBM lagging behind the latest updates from deterministic model runs. Rain showers are expected to move in by Thursday morning and exit mostly on Friday. Some snow will also be possible with some wrap around precip, but with discrepancies with the timing of the system and lingering moisture, we went with rain/snow mix with minimal forecast snow accumulations Friday morning. Previous discussion follows. Thiem LONG TERM /Sunday Night through Friday/... The beginning of the extended period will be characterized by a dry airmass behind the exiting cold front. Relative humidity values are expected to drop into the upper 20s and 30s across the area and precipitable water values will be limited to 0.5 inches or less. Temperatures will also start the period near or just above climatological normals, with morning lows mainly in the 30s and afternoon highs mainly in the 50s to low 60s. A fast-moving upper- level shortwave will traverse the Tennessee Valley on Monday morning. However, considering the limited moisture over the region, very little to no impact will be observed over north and central Georgia from this disturbance. As the disturbance continues to move eastward to the mid-Atlantic coast, upper-level ridging will build in over the southeastern CONUS on Tuesday and remain in place through late Wednesday. A surface high associated with this ridge will lead to continued clear skies and a gradual warming trend through Wednesday. In the later part of the week a synoptic trough will set up over the eastern CONUS, bringing another storm system to the area on Thursday and Friday. Some model discrepancies remain with the evolution and timing of this system, and ultimately the impacts to our forecast area. The latest GFS and ECMWF both develop a closed-off low in the ArkLaTex region on Thursday, which extends a cold front towards the forecast area. However, the models diverge on the speed at which the cold front and associated precipitation approaches north and central Georgia, with timing discrepancies still up to 12 hours in the guidance. Considering the lingering uncertainty with respect to this system, rain chances remain limited to chance PoPs across the majority of north and central Georgia during the day on Thursday and into early Friday. The chance also remains for light snow showers and a light rain/snow mix across far northeast Georgia on Thursday night and into Friday morning due to wraparound moisture behind the system and below freezing temperatures in the far north behind the cold front. However, the potential for frozen precipitation will need to be monitored as model guidance trends towards better agreement. King .AVIATION... 00Z Update... Expect some return of IFR/MVFR ceilings mainly after 02z with abundant low level moisture. Main area of rain should continue to push east of KMCN and KAHN overnight...although isolated showers are possible elsewhere. Fairly quick improvement and scattering after 14z Sunday behind the upper system with increased west to northwest winds 9-12 kts gusting up to 20 kts. //ATL Confidence...00Z Update... Medium on overall cigs/precip trends. High on all else. Baker && .PRELIMINARY POINT TEMPS/POPS... Athens 43 53 34 58 / 50 5 0 0 Atlanta 40 51 34 56 / 20 5 0 0 Blairsville 37 44 29 50 / 30 10 0 0 Cartersville 39 50 30 56 / 20 5 0 0 Columbus 40 56 35 60 / 40 0 0 0 Gainesville 41 50 34 56 / 30 5 0 0 Macon 44 57 34 61 / 70 5 0 0 Rome 39 51 30 58 / 10 10 0 0 Peachtree City 38 52 32 58 / 30 5 0 0 Vidalia 51 60 38 60 / 100 5 0 0 && .FFC WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...41 LONG TERM....Thiem AVIATION...41
Area Forecast Discussion
National Weather Service Fort Worth TX
554 PM CST Sat Jan 2 2021 ...New Short Term, Aviation... .SHORT TERM... /NEW/ /Through Sunday Evening/ Light south/southwest winds and sunny skies allowed afternoon temperatures to climb a tad higher than forecast this afternoon, with several of the western zones topping out around 60. Dry air and light winds should still lead to a good radiational cooling night with lows in the 30s area-wide. Temperature/dewpoint spreads will approach zero during the pre-dawn hours across the northwest zones, and patchy fog has been added in those areas for Sunday morning. Meanwhile, water vapor imagery reveals one shortwave near Memphis and moving away from the area, while another is beginning to take shape near the Nebraska/Colorado state line. The lee-surface cyclone induced by the upstream wave will move into northwest Texas overnight into Sunday. The resulting pressure gradient will increase southwest winds to 10-15 MPH during the day Sunday. This should allow Sunday temperatures to climb into the 60s for all but the northwest, where lingering fog will keep conditions quite a bit cooler. The entire system will move quickly southeast through the Plains, dragging a cold front through the area Sunday afternoon and evening. Northwest winds around 10 MPH behind the front will become light and variable Sunday night, likely setting up the area for a more widespread round of radiation fog. 30 && .LONG TERM... /Issued 304 PM CST Sat Jan 2 2021/ /Sunday night through next weekend/ Expect another cold night Sunday night with lows in the upper 20s across the far western zones to low/mid 30s elsewhere. One issue we will have to monitor is the potential for fog/stratus to develop across parts of North Texas during this time period. Some of the deterministic models like the HRRR and NAM continue to be more aggressive with the fog/stratus, and even NBM probabilities are showing reduced visibilties or low clouds through Monday morning. Surface winds will be calm or light enough to support the fog and/or low clouds, but moisture is expected to be limited and shallow. Confidence is not high enough to include it in the forecast at this time, but we can`t rule some patchy ground fog especially along the Red River counties. We will have to keep an eye on the latest trends through tomorrow. Otherwise, a pretty quiet start of the week with above normal temps thru Wednesday. As a surface high pressure and an upper ridge moves over the region, we will enjoy nice temperatures (60s) under mostly clear skies. Winds will shift to the south on Tuesday as the next trough/upper low moves across the Rockies. Overall forecast details about this system have not changed much, with the best potential for showers and isolated storms east of I-35 Wednesday afternoon. Despite the uncertainties on the track of the low, ensemble analysis show a more progressive pattern keeping the best lift north of our area. For now, we kept PoPs between 20% and 30% mainly across East TX. Instability is forecast to be fairly weak, but we can`t rule out some isolated storms. No severe storms are anticipated. Due to the Pacific nature of this system, we don`t anticipate a extreme drop in temperatures. Our mid-late week forecast include nice temperatures, no rain, and north winds. Highs will stay on the cool side ranging from the low 50s across North TX to upper 50s to low 60s across Central TX. Overnight lows will drop into the 30s to near 40s each night. It looks like our next rainmaker will arrive sometime next weekend. As expected, long range models diverge on the progression of the upper trough, but overall consensus show a slight chance of precipitation either Saturday night or next Sunday. Sanchez && .AVIATION... /NEW/ /00Z TAFs/ Light south winds will increase to 10-15 kt after 15Z Sunday ahead of the next cold front. FROPA in the DFW area looks to be around 22Z Sunday, then just after 00Z Monday for KACT. Northwest winds around 10 kt can be expected behind the front. Winds will become light Sunday night as high pressure enters the area, which could lead to for formation after 06Z Sunday, and may need to be addressed in future forecasts. 30 && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 36 60 34 62 36 / 0 0 0 0 0 Waco 36 66 34 63 36 / 0 0 0 0 0 Paris 33 58 32 59 33 / 0 0 0 0 0 Denton 33 57 29 63 31 / 0 0 0 0 0 McKinney 33 58 32 61 33 / 0 0 0 0 0 Dallas 37 61 36 63 38 / 0 0 0 0 0 Terrell 34 61 32 61 33 / 0 0 0 0 0 Corsicana 37 63 37 63 38 / 0 0 0 0 0 Temple 34 66 34 64 36 / 0 0 0 0 0 Mineral Wells 32 54 29 62 33 / 0 0 0 0 0 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$
Area Forecast Discussion
National Weather Service Lincoln IL
824 PM CST Sat Jan 2 2021 .SYNOPSIS... Issued at 305 PM CST Sat Jan 2 2021 Light drizzle will continue to impact the region through the evening as the next weather system moves through the area tonight. This will bring another chance for accumulating snowfall to location se of the Illinois River Valley, with upwards of 2 inches by Sunday morning. The best chance for snowfall exists across eastern Illinois, while locations in central Illinois will see upwards of 1 inch. Cloudy skies will also persist through the overnight, along with the return of dense fog conditions northwest of the I-55 corridor. Behind this system, High pressure arrives to end the weekend and begin next week. && .UPDATE... Issued at 824 PM CST Sat Jan 2 2021 Evening water vapor imagery shows our upper low located south of St. Louis, with a noticeable curl in the radar imagery over that area. Not a significant amount of precip shown on radar mosaics, likely due to the beam overshooting in this low cloud regime. Local radar in the more sensitive coverage pattern does show an increase in light snow and drizzle over central Illinois in the last 20 minutes or so. HRRR suggests a more organized increase in snow as we get closer to 06Z and the upper low moves into southern Illinois, with the focus continuing to be in the Bloomington to Decatur area and east, with amounts of 1-2 inches. No significant changes being made to the snow amounts in the forecast at this time. Regarding the fog advisory, there is some concern about the eastern extent of it, and high-res guidance showing more of a focus after midnight extending east into the Illinois River valley. Lower visibilities along I-55 may be more from the snow versus the fog, as visibility thus far north of the low have been more in the 1 to 2 mile range on the lower end and the dense fog has been near Quincy. Will continue to monitor this over the next few hours, && .SHORT TERM...(This evening through Sunday) ISSUED AT 305 PM CST Sat Jan 2 2021 Low clouds continue to impact the Midwest as more moisture is ushered into the region tonight. This is evident on radar as light bands of precip are currently pushing through the state. As this evening progresses, the upper level Low pressure system will track towards the Ohio River Valley from the lower Mississippi River Valley. This will track mostly snowfall through the region overnight, as temperatures will drop below freezing after sunset. Some light mixed precip could occur to begin, south of the I-70 corridor, as temps are slightly above freezing...however this will change to snowfall as the Low passes south of the area. With winds coming out of the ne currently, low clouds are expected to linger throughout the overnight into the morning. This will finally begin to shift out of the area Sunday as winds shift to the west behind Low pressure passage and exit. As with most winter time clouds, expecting lingering low ceilings through Sunday morning. Issued a Dense Fog Advisory for tonight through Sunday morning, as these clouds are expected to persist throughout the period. With the light winds lingering into Sunday morning, will have the chance to hold the clouds in place. Only question this afternoon was the possibility of clouds increasing as the Low pressure slides through the region. Thinking was that it will be far enough southeast that the low clouds and excessive moisture would be enough to hold fog in place. This system will slide out of the region Sunday, allowing for the return of High pressure to the area. .LONG TERM...(Sunday night through Saturday) ISSUED AT 305 PM CST Sat Jan 2 2021 Weak High pressure slides through the Midwest late Sunday into the start of the week. However there is some model depiction of another weak frontal system to track through the upper Midwest Monday night into Tuesday. This could swing another weak frontal boundary through the region late Monday. The big question here will be if there is enough moisture to spark a few showers throughout the area. The best energy looks to be east of the Midwest, however some models hint at a chance for precip. Currently left the mention of any precip out of the forecast, as this is a weak system, and not expected to bring any precip to the area. Behind this boundary, a stronger High pressure system slides into the area from the south. Unfortunately, this week`s setup really will be a mixed bag. Heading into mid-week, a large-scale Low pressure system develops across the central Plains and tracks slowly eastward. This will bring the next weather maker to the Midwest Wednesday evening through Thursday. However, models do have some hint that this system might slide south of the area, so there is some detail that needs to be worked out over the next couple of days. If High pressure takes dominance over eastern Canada mid-week, this will help to push the system south of the Midwest Wednesday night, moving the best chance for precip across the se US. If High pressure cannot hold control, then this system is likely to slide into the Tennessee Valley, which would provide some precip to southern Illinois during the second half of the week. Models have differing solutions heading into the weekend, so this will need to be held of for now. But High pressure looks to take control again, as of now Saturday looks dry. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 519 PM CST Sat Jan 2 2021 While widespread ceilings of a few hundred feet are present over much of central Illinois, areas from KCMI east and south have recently seen MVFR ceilings rise over 2,000 feet at times. Deterioration there is expected later this evening as light snow moves into the area, reducing visibilities down below a half mile. Elsewhere, there has been some periods of light snow or drizzle recently, but more widespread light snow is expected toward mid evening. No real improvement in ceilings expected through the period, though perhaps getting closer to 1,000 feet at KPIA/KBMI westward Sunday afternoon. && .ILX WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until noon CST Sunday for ILZ027>031-036>038- 040>042-047>051. && $$ UPDATE...Geelhart SYNOPSIS...Baker SHORT TERM...Baker LONG TERM...Baker AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Jacksonville FL
904 PM EST Sat Jan 2 2021 .UPDATE... Mid to upper level trough over the srn U.S. will continue to push the slow-moving cold front toward our area with a band of showers and embedded thunderstorms. Latest radar trends over the past hour or so has shown a general weakening trend of higher reflectivities but broad low level southwest fetch and PWATs values approaching 1.8 inches will continue to lead to numerous to widespread rain showers rest of tonight. Localized flooding is still possible but the threat is low given the radar presentation. Light to moderate showers still occurring in the flash flood watch area so will keep the watch up through the 11 PM expiration at this time. Recent lightning imagery showing no strikes but weak buoyancy and frontal forcing could still result in a couple of isolated t-storms through late tonight. HRRR shows the band of showers will continue moving east and move off the southeast GA coast around 5 AM and for the northeast FL coast by 8-9 AM. Current forecast handles this well, and only minor adjustments made to the forecast. Min temps may end up just slightly lower so adjusted southeast GA min temps slightly. .MARINE... No change made at this time with marginal winds offshore from the south ahead of the approaching front so will maintain SCEC headline. Seas from nearshore buoys are in line with the current forecast as well. && .PREV DISCUSSION [627 PM EST]... .NEAR TERM [Through Tonight]... A stalled front stretching from the northeastern Gulf into the Florida Big Bend into southern Georgia has maintained a band of moderate to briefly heavy showers mainly over our interior southeast Georgia counties today. Troughing, associated with an upper low, extends into the northern Gulf helping to reinvigorate convection across our area by lifting shortwave energy from the Gulf of Mexico along the frontal boundary. This will increase rainfall intensity along with the chances for stronger thunderstorms with gusty winds that will push out ahead of the boundary into inland SE GA into the evening hours. A Flash Flood Watch is in effect into this evening for portions of inland southeast Georgia. Around 1 to 2 inches of rainfall have fallen today. An additional 1 to 2 inches are expected in the watch area with locally higher amounts possible. The trough will cause the front to move eastward tonight and approach the Atlantic coast by Sunday morning. The upper low driving this system will lift northeastward into the Great Lakes which will lift much of the energy aloft away from the region. This will bring an end to heavier rainfall after midnight and a scattering of showers. Precip will begin to end from northwest to southeast tonight. Cooler, drier air begins to filter in behind the front allowing lows tonight to dip into the 50s across southeast georgia and Suwannee Valley and the low 60s in northeast Florida. .SHORT TERM [Sunday Through Monday Night]... A cold front exits the region by Sunday afternoon with scattered lingering showers in the morning hours mainly south of Jacksonville. Cooler, drier air filters into the region behind the front. Low level ridging will build in over the southeast into early next week in the wake of the cold front. Despite cooler air advecting in, highs on Sunday will reach above climo with increasing sunshine. Temperatures then drop to around climo with lows in the upper 30s to low 40s and highs on Monday in the 60s. .LONG TERM [Tuesday Through Friday]... Surface high pressure over the lower Mississippi valley on Tuesday will move northeastward and expand across the eastern CONUS continuing dry weather for the region. Tuesday night into Wednesday morning will be the coolest night with lingering cold air advection and clear skies. Lows will be in the mid 30s inland and patchy frost will be possible. Around mid-week, another upper low will move into the Plains and develop the next cold front to approach the region. The cold front will move through Thursday night into Friday bringing chances for precipitation with its passage. Temperatures will be above climo on Thursday with southerly flow ahead of the front. .AVIATION... [Through 00Z Monday] VFR at this time but expect showers and possible brief, isolated embedded t-storm to move over southeast GA and northeast FL tonight. Low cigs and vsby restrictions are expected at TAF sites developing after midnight, with MVFR-IFR cigs and MVFR vsby at times. Main period will be from about 06Z to 13Z period for the precip and lowest cigs. We can`t rule out LIFR cig for 2-3 hrs during this period. South-southwest winds 10 kt or less much of tonight and then cold front moves thru around the 09Z to 12Z time frame, shifting southwest winds to west. A chance of LLWS possible around 08Z to 12Z Sunday, mainly over northeast FL, as a low level jet strengthens just ahead of the cold front. Clearing starts developing after about 14Z-15Z Sunday...with VFR likely by 15Z to 18Z. .MARINE... A cold front will move across the coastal waters tonight into Sunday bringing showers and an isolated thunderstorm. Winds will continue to linger around 15 to 20 knots over our offshore waters through Sunday, then slacken behind the cold front. High pressure will then build along the northern Gulf coast region early next week, with a prevailing offshore flow. Rip Currents: SE GA - low risk this weekend. NE FL - moderate risk today, low risk tomorrow with offshore flow .HYDROLOGY... A Flash Flood Watch is in effect for portions of inland southeast Georgia into this evening. Around 1 to 2 inches of rainfall have fallen today. An additional 1 to 2 inches are expected in the watch area with locally higher amounts possible. Highest amounts will likely be areas northwest of Jasper, FL, Waycross, GA, and Jesup, GA. Some localized flooding possible with mainly ponding of water on roads and creeks and streams rising out of their banks. Expect significant river rises following the event for next week on the main stem river basins. && .PRELIMINARY POINT TEMPS/POPS... AMG 53 61 37 60 38 / 100 0 0 0 0 SSI 58 66 42 61 43 / 70 20 0 0 0 JAX 60 69 41 63 41 / 70 30 0 0 0 SGJ 62 70 44 63 43 / 70 50 0 0 0 GNV 60 69 39 64 37 / 80 30 0 0 0 OCF 62 70 42 66 39 / 70 30 0 0 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Flash Flood Watch until 11 PM EST this evening for Hamilton. GA...Flash Flood Watch until 11 PM EST this evening for Appling- Atkinson-Bacon-Brantley-Clinch-Coffee-Echols-Jeff Davis- Northern Ware-Pierce-Southern Ware-Wayne. AM...None. &&
Area Forecast Discussion
National Weather Service Pendleton OR
254 PM PST Sat Jan 2 2021 Updated Aviation Discussion .AVIATION...00z TAFs...VFR conditions expected through the TAF period. Currently strong S to SW winds impacting most sites, having gusted up to and over 30 kts already this afternoon. A front will move through this evening and bring a chance of light showers for most sites. MVFR conditions may briefly occur during rainfall. Cigs will be bkn-ovc around 5-10 kft, decreasing to 4-5 kft overnight. Winds will decrease and cigs will lift and become sct by daybreak Sunday. 74 && .PREV DISCUSSION... /issued 115 PM PST Sat Jan 2 2021/ SHORT TERM...Tonight through Monday night. Active weather pattern for the next few days. A cold front will move across the region tonight bringing high mountain snow and windy conditions. Most of the snow will be along the crest of the Cascades and over the Blue Mountains where winter weather advisories remain in effect. Considered upgrading to warning for the Blues above 4500 feet where HREF is pinging some hefty snow amounts tonight but some of the model guidance is suggesting that snow levels will rise above 5000 feet and NBM snow ratios are only about 8 to 1 which will cut down on accumulation efficiency. Still the situation at the snotels and Tollgate will need to be monitored through the evening. Other concern is the wind. Models are emphatic in showing limited mixing of the winds to the surface with the cold frontal passage tonight. Thus have held off on issuing any wind advisories except for the southern foothills where the HRRR is showing some gusts AOA 50 mph tonight. Winds will diminish quickly tomorrow and snow will end by 18Z. It will be a short break as a warm front lifts north across the area Sunday night spreading mountain snow across the region...with the biggest impact over the east slopes of the Washington Cascades. High mountain snow and valley rain will continue on Monday and as a low pressure tracks across the region...strong winds will be possible Monday afternoon and Monday night. 78 LONG TERM...Tuesday through Saturday...Organized trough will depart our area early Tuesday, leaving behind dry conditions until a southwesterly jet brings another round of valley rain and mountain snow early Wednesday. Global ensembles varying a decent degree with this system, but another few tenths of precip could fall given potent moisture advection as depicted by deterministic GFS and ECMWF. Snow levels will start at around 2000 ft early Tuesday, gradually rising to above 3500-4000 ft as warm air noses into our area via SW flow, before dropping off toward 2000-2500 ft by the end of the long term period. As a result, wintry precip threat will remain in the mountains, as the synoptic pattern favors generally mild conditions given the time of year. Highs will start in the mid to upper 40s Tuesday, dropping off toward the low 40s/upper 30s by the end of the week. Lows will have trouble dropping below freezing before next weekend due to abundant cloud cover expected given upper- level flow pattern. Deterministic guidance diverges a bit after Wednesday`s system, but general pattern favors dry conditions outside of the Cascades, as models back off on the strength of the flow aloft. Ensemble QPFs generally agree with this, with generally dry weather beyond Wednesday. ECMWF tries to bring in a trough by Friday, while westerly flow continues within the GFS. Will stick with NBM for now, which keeps most of the CWA outside the crests of the Cascades dry and quiet Wednesday night through next weekend. 74 && .PRELIMINARY POINT TEMPS/POPS... PDT 41 50 39 50 / 40 50 40 70 ALW 44 50 41 51 / 60 60 50 80 PSC 42 52 40 51 / 30 20 40 60 YKM 33 48 33 45 / 60 10 80 90 HRI 41 52 40 53 / 30 30 40 60 ELN 30 43 32 42 / 60 10 80 90 RDM 37 49 38 50 / 40 50 30 70 LGD 36 43 34 43 / 80 70 50 90 GCD 37 46 37 47 / 70 50 40 80 DLS 40 49 39 49 / 80 50 80 90 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Wind Advisory until 7 AM PST Sunday for ORZ508. Winter Weather Advisory until 10 AM PST Sunday for ORZ502-509. WA...Winter Weather Advisory until 10 AM PST Sunday for WAZ030-520. && $$ SHORT TERM...78 LONG TERM....74 AVIATION...74
Area Forecast Discussion
National Weather Service Portland OR
155 PM PST Sat Jan 2 2021 .SYNOPSIS...An active weather pattern will continue through at least the middle of next week. A cold front moves onshore late this evening with increasing rain and wind. Another system impacts the area Sunday and Sunday night, followed by addtional weather systems through mid-week. A brief break in the action is expected Wednesday night or Thursday, but a return to wet conditions is likely Friday. && .SHORT TERM...Tonight through Tuesday...Early afternoon GOES-17 water vapor imagery revealed an upper level low pressure area just west of Hadai Gwaii with an extensive moisture feed across the Pacific into the Pacific Northwest fed by a strong west upper level jet. Wind is the first weather concern. The 12Z 4km WRF-GFS has backed off slightly regarding coastal wind. The 12Z run shows a swath of 50 kt 10m wind gusts along the coast 03Z Sun. By 06Z, this 50-kt core is located from KTMK to K6S2. There is a dramatic wind shift associated with the cold front immediately behind the south to southwesterly wind core max. The current high wind warning timing for the coast looks on track, but max wind gusts may end up a little lower than forecast. The WRF-GFS and 19Z HRRR 80m wind product indicate 35-40 kt gusts this evening through midnight for the Willamette Valley, mainly south of KSLE. South to southwest wind ramps up in the north Willamette Valley early this evening and gradually works south through the remainder of the evening. The HRRR 80m wind gust product and NBM wind gust forecast suggest 25-35 kt gusts for Clark County. Will maintain the current advisory at this time. Wind speeds will quickly drop off behind the cold front. Expect the cold front to reach KAST around 06Z Sun, KPDX 09Z and KEUG 10Z to 111Z. The other weather concern will be precipitation and potential hydro issues. The ECMWF Precipitable water ensemble mean valid 00Z Sun shows 1.0 to 1.2 inches. Combine this with 50-70 kt 850 mb southwest flow into the Oregon Coast Range and southwest Washington Willapa Hills and the result in impressive orographic lift. Per WPC Mesoscale Precip Discussion, rainfall rates up to 0.5 inches per hour will be possible on southwest-facing slopes in the higher terrain. In addition, the GEFS ensemble mean Integrated Water Vapor Transport (IVT) valid 06Z Sun shows a band of 500-700 kg/m/s directed into much of the forecast area. The ECMWF IVT valid 06Z has slightly higher values. Fortunately, this will be a fairly fast-moving cold front such that these high rainfall rates should be short-lived. Rainfall totals through early Sun morning will be on the order of 2 to 4 inches for the Oregon Coast Range, Willapa Hills and south Washington Cascades. The expected QPF looks to be enough to result in minor flooding on the Greys River. Thus, a flood watch has been issued. Snow levels have risen to 5000 to 5500 feet early this afternoon per the Astoria profiler. Snow levels are expected to lower to around 3000 feet overnight in the south Washington Cascades to near pass level in the Lane County Cascades. However, the bulk of the precipitation will have already occurred by the time snow levels start falling. Expect total snowfall by Sun morning on the order of 6 to 12 inches above 5000 feet. The cold front does not completely go away Sun. The remnants will reside over southwest Oregon Sun morning and then transition to a warm front Sun afternoon due to surface low development well offshore. Rain will increase across the south part of the area late Sun morning or early afternoon and then lift north. Another cold front reaches the coast between 06Z and 12z Mon. The 12Z model runs continue to struggle with the evolution and strength of the surface low. The GFS has been insistent the past couple of runs developing a compact sub-990 mb low pres center just west of Cape Arago 18Z Mon. The NAM shows multiple low pres centers along the baroclinic boundary, all of which are in the mid to upper 990s. The 12Z ECMWF ensembles show a high variability regarding surface low placement and strength. All of which leads to lower-than-average forecast confidence. It appears a lull in the action occurs Mon night and most of Tue, followed by another weather system nearing the coast late Tue. The long period (18-19 seconds) westerly swell is expected to build early this morning then last into the afternoon before slowly losing energy as the dominant wave period drops to 16 to 17 seconds. This supports keeping the High Surf Advisory for today, and also brings an enhanced threat of sneakers waves. Weishaar .LONG TERM...Tuesday night through Saturday...The active weather pattern continues Tue night and Wed as the 12z deterministic runs are in general agreement showing another weather system moving through the area. Some of the model details differ, with the GFS suggesting another possible coastal wind event while the ECMWF has a much weaker pressure gradient. The ECMWF MSLP ensemble mean valid 00Z Thu indicates weak ridging over the area while the deterministic GFS shows a 980 mb low center near KUIL. Favor the ECMWF ensembles, which line up reasonably well with the total mean 500 mb cluster analysis. There is moderate confidence that Wed night through Thu will be rather quiet, but not confidence enough to go completely dry. Model discrepencies become more pronounced Fri and Sat. The 12Z model runs show another frontal system moving into the area Fri. However, the ECMWF shows a wide range of surface low solutions. The 12Z GFS solution would suggest another possible high-wind event for the coast. All in all, rather wet and mild conditions look to persist through the extended period. Weishaar && .AVIATION...Conditions will get worse the rest of today as a strong cold front approaches. Mix of MVFR and IFR along the coast will persist, though cigs will lower a tad more. Southerly winds will gust 40 to 50 kt, with strongest winds occurring between 02Z and 07Z this evening. Cold front will push to Astoria between 05Z and 06Z, then push gradually to the south to Newport by 08Z. Winds will quickly ease behind the front, but MVFR CIGS will persist rest of the night. Farther inland, MVFR will dominate. Current VFR to south and east of KMMV to KUAO line will gradually fall to MVFR by 02Z as rain spreads farther southward. Will remain mostly MVFR overnight into early Sun. Expect south winds gusting 25 to 35 kt at times for most interior lowlands of Willamette Valley this evening, with strongest winds between 03Z and 08Z. Also, expect southerly gusts 40 to 45 kt over the higher ridges of Coast range and Cascades through 08Z. For detailed regional Pac NW weather information, go online to: KPDX AND APPROACHES...MVFR will persist tonight, with rain through midnight. Will maintain breezy south winds, with gusts 20 to 30 kt at times through 08Z. Still think strongest of those winds will be between 03Z and 07Z as cold front draws closer to the region. Winds will ease quickly behind the front after midnight. MVFR will persist through 14Z, with gradually improvement to VFR with broken clouds Sun am. /Rockey && .MARINE...Deep low pressure over the southeast Gulf of Alaska will persist for next several days, maintaining rather active weather on the coastal waters. Strong cold front offshore will push to the Washington coast later this evening. As of 2 pm, southerly winds gusting 35 to 45 kt on the coastal waters, with seas running 20 to 21 feet. As the front draws bit closer, should see boost in the winds, as gradients tighten and strong winds aloft arrive. Current expectation of storm force winds looks reasonable, so no changes. Gusts 45 to 50 kt this evening. Cold front will drop to Astoria between 9 and 10 pm, pushing southward and reaching Newport around midnight, and past Florence by 1 or 2 am. Winds will ease quickly behind the front. Seas will stay at 20 to 25 ft range this evening, peaking between 8 pm and midnight. Afterwards, winds much less overnight, with seas subsiding. But, still a lot of long period westerly swell offshore, so will maintain seas at 17 to 20 ft overnight through next several days. More tranquil later tonight and Sunday, as region sits between fronts. Warm front to the south will lift back to the north later Sun afternoon and Sun night, with another round of strong gales. May have to watch this, as models suggest some potential of storm force gusts Sun night, especially south of Cascade Head. No headlines yet, as have enough with current weather, but overnight shifts will likely issue new gales or storm watch for Sun night. && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory until 4 AM PST Sunday for Northern Oregon Cascades. Winter Weather Advisory from 10 PM this evening to 10 AM PST Sunday for Cascades in Lane County. Wind Advisory until midnight PST tonight for Central Willamette Valley-Greater Portland Metro Area-South Willamette Valley. High Surf Advisory until 4 PM PST Sunday for Central Oregon Coast-North Oregon Coast. High Wind Warning until 1 AM PST Sunday for Central Oregon Coast-North Oregon Coast. WA...Winter Weather Advisory until midnight PST tonight for South Washington Cascades. Wind Advisory until midnight PST tonight for Greater Vancouver Area. High Wind Warning until 9 PM PST this evening for South Washington Coast. High Surf Advisory until 4 PM PST Sunday for South Washington Coast. PZ...Storm Warning from 6 PM this evening to 1 AM PST Sunday for coastal waters from Cape Shoalwater WA to Florence OR out 60 NM. Gale Warning until 6 PM PST this evening for coastal waters from Cape Shoalwater WA to Florence OR out 60 NM. Small Craft Advisory until midnight PST Sunday night for Columbia River Bar. $$ Interact with us via social media: