Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/12/23

National Weather Service Sioux Falls SD
523 PM CST Sat Mar 11 2023 .SHORT TERM...(This Evening through Sunday) Issued at 242 PM CST Sat Mar 11 2023 KEY MESSAGES: 1. Windy and cold Sunday, with scattered flurries possible. 2. Roller-coaster temperatures this week, with a cold Monday, warmer Tuesday-Wednesday, then cooling down again late week. 3. Transition to colder air mass will bring our next chance of wintry precipitation somewhere in the Thursday timeframe, possibly starting as a mix before changing to more snow. -------------------------------- REST OF THIS AFTERNOON: Low pressure responsible for our snowfall today is currently still spinning over western ND this afternoon. Light snow lingers over portions of our MN/IA counties as of 20Z, mainly east of US Highway 59 (Marshall-Worthington-Sioux City). This should continue to trek east and out of our forecast area through the balance of the afternoon. TONIGHT-SUNDAY: The low pressure tracks east through southern ND and into central MN tonight, with the associated cold front pushing east across our forecast area this evening. Post-frontal west-northwest flow will increase in our far west by late evening, with stronger winds advancing east and weakening slightly as they reach the I-29 corridor around 12Z, and continuing to weaken slightly as they progress into southwest MN/northwest IA Sunday morning. Have seen some gusts topping 40kt/46mph in southeast MT/northwest SD this afternoon, and if we were able to fully tap into the 40+kt winds atop the mixed layer per the latest RAP soundings, could see a period of advisory level winds in areas along/west of the James River Valley late tonight into Sunday morning, and will join our neighboring SD offices with a Wind Advisory from midnight tonight through 10AM CDT Sunday. Temperatures through most of this area have warmed into the mid-upper 30s today, and did not receive much new snowfall either, so while there could be some low drifting, would not expect blowing snow to be a significant issue. The colder air will be accompanied by additional stratus spreading southward into the forecast area later tonight and Sunday, so after a welcome sunny day for at least western portions of the forecast area today, clouds will likely be rather abundant again on Sunday. Not a lot of deep moisture for this to work with, but soundings indicate the top of the cloud layer could tap into the DGZ, so scattered flurries seem a possibility near/northeast of a Huron to Sioux Falls to Spencer line. Colder temperatures and the gusty winds will make for a blustery day, with highs only in the 20s, and wind chills in the single digits-lower teens. .LONG TERM...(Sunday Night through Saturday) Issued at 242 PM CST Sat Mar 11 2023 MONDAY: Still a cold day with highs again in the 20s, but much less wind with a surface ridge moving across the area, so will not feel quite as brisk as Sunday. TUESDAY-WEDNESDAY: Strong warm front moves across the CWA Tuesday, with the wedge of warmest air, as much as +10C(!), building into our southern counties Wednesday. If we were snow-free, this could result in quite a warm-up, as full mixing could push temperatures well into the 60s through the Missouri River Valley Wednesday afternoon. Alas, most, if not all of the forecast area does have some snow cover to overcome, and the question is how much impact this will have on limiting our temperatures. Still seeing a broad spread among the NBM membership, with as much as a 10F difference between the 10th and 90th percentiles on Tuesday, growing to 15-25F on Wednesday. For both days, the NBM mean remains fairly close to the 50th percentile, so feel comfortable leaving the forecast as is for now. WEDNESDAY NIGHT-FRIDAY: Deterministic models are fairly similar in timing a strong cold front through the forecast area late Wednesday night-Thursday morning, as a deepening upper trough digs into the northern Plains from central Canada. These deterministic solutions alone would lead one to think we could be in store for another significant precipitation system. However, examining the ensembles shows that these deterministic solutions are relative outliers on the high side, with the mean much lower, and a large majority of ensemble members near or below this mean. That said, it looks like a pretty good chance for at least some light precipitation, but with very high uncertainty on amounts at this range. Late week confidence is much higher that cold air will again settle into the region, with highs Friday-Saturday potentially as cold, or colder, than we see to start off the week. && .AVIATION...(For the 00Z TAFS through 00Z Sunday Evening) Issued at 521 PM CST Sat Mar 11 2023 Back edge of MVFR stratus trying to push east of I-29 early this evening. A secondary reinforcement of this stratus may be possible keeping stratus near the I-29 corridor for a couple more hours before clearing. A secondary cold front arrives later tonight bringing 40+ mph winds through the Tri-State area into Sunday morning. Also expecting more stratus to drop southward towards midnight, thickening through the overnight and remaining overcast for a good portion of Sunday. Colder air rotating around the departing upper low moving through North Dakota will lead to the potential for a few flurries or snow showers into Sunday. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...Wind Advisory from midnight CST tonight to 10 AM CDT Sunday for SDZ038-050-052-053-057>060-063>065-068-069. MN...None. IA...None. NE...None. && $$ SHORT TERM...JH LONG TERM...JH AVIATION...Dux
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
855 PM CST Sat Mar 11 2023 .UPDATE... Issued at 849 PM CST Sat Mar 11 2023 Light to moderate snow has just about filled in across the northern part of the CWA, namely areas north of I-80. Webcams across the Rockford metro and vicinity show snow accumulating on cooler surfaces and even a few roads are beginning to gather a dusting. Further south, we`re seeing light rain and rain/snow mix filling in where there`s just enough positive energy above the surface to melt the snow on its way down. As we continue to cool both diurnally and dynamically with still a little bit of room between temps and wet bulbs, we should see the rain/snow line drop south through the remainder of the evening and into the overnight. Additionally, many areas across the metro have been struggling with some dry air through roughly the 800-900mb layer inhibiting precip aloft from reaching the ground over the past couple of hours. However, ACARS soundings out of MDW show that we`ve recently managed to overcome that thanks to modest, albeit ample, low level warm advection, a tad earlier than RAP and HRRR soundings were suggesting we would. RAP mesoanalysis places a notable swath of 700mb f-gen over the central and western CWA on the leeward side of the encroaching trough which lines up well with where we`ve been seeing the more moderate snowfall which has been pulling visibilities down as low as one mile here and there. This f-gen is expected to continue pushing to the northeast with the trough through the rest of this evening. The better synoptic forcing will also eject to the northeast as the trough axis approaches meaning we`ll likely see the heaviest of the snow over the next few hours. Snow is still expected to continue through the night but will lighten up as forcing lets up and we maybe see little bit of dry advection near 925mb, or so the RAP and HRRR say though it`s tough to nail down where that`s coming from. All in all, the forecast through the night looks to be on track. Doom && .SHORT TERM... Issued at 308 PM CST Sat Mar 11 2023 Through Sunday night... A pair of upper level disturbances are noted in the water vapor imagery across the Plains early this afternoon. The first of these is currently shifting eastward into the Lower to Mid- Missouri Valley, while a more pronounced northern stream upper low is moving eastward into western North Dakota. These features will play a large role in our sensible weather tonight through early Monday. While cloud cover has been, and will continue to be persistent through the day, warm air advection in advance of the approaching Mid-Missouri Valley disturbance is helping drive temperatures well into the 30s (with some low 40s south) as of this writing. Expect these readings to hold steady in the 30s to around 40 into early this evening. Precipitation is expected to hold off across the area through late this afternoon. Thereafter, we should see the warm air advection driven precipitation shield across IA steadily translate eastward across the area through the evening in concert with the parent mid-level disturbance. While the entire area looks to see precipitation from this event tonight, overall amounts will be much lower than they were with Thursdays weather system. However, precipitation types do look to be a bit tricky again with this event, especially for areas south of I-80, where warmer boundary layer conditions will reside into early this evening. These slightly warmer conditions will likely result in areas south of I-80 onsetting as a period of rain for a few hours this evening before potentially mixing with a bit of wet snow later in the evening. Farther to the north, a brief rain snow mix is possible at onset, but slight cooler conditions should support primarily wet snow shortly after onset. While some wet snow accumulations still appear likely tonight, especially for northern areas, light precipitation rates and marginal surface temperatures should keep total amounts mainly under 2". In fact, many areas are likely to see less than an inch, and mainly on grassy and elevated surfaces! The main mid-level disturbance (the primary forcing mechanism) is expected to shift east of the area a bit after midnight tonight. As it does so, a much drier mid-level airmass is expected to shift overhead atop a lingering low-level moist layer. In spite of this, light precipitation is likely to continue across the area overnight as low-level isentropic upglide continues in this moist layer in response to the northern stream system shifting into the Upper Midwest. While precipitation type may continue to support some light snow overnight, there is concern that the snow quality will become rather poor overnight, possibly even mixing with (or changing to) drizzle at times as the much drier mid-level airmass shifts overhead. This suggests that any additional snow accumulations late tonight into early Sunday morning may become minimal. The lower level moist layer should become deep enough across far northern IL to support a continued period of snow showers mid to late Sunday morning as low-level warm air advection continues. While this is the case, marginal surface temperatures during the daylight hours will once again limit any minor slushy accumulations to grassy areas and elevated surfaces. Temperatures should warm close to 40 early Sunday afternoon, so any lingering precipitation there will likely fall as light rain. Late in the day and into the early evening hours, the northern stream system is expected to drive a cold front eastward across the area. This may result in a quick moving area of rain and snow showers as the front interacts with a corridor of steep low-level lapse rates. Certainly cannot rule out some minor accumulations with this across parts of northeastern IL, especially if a brief period of heavy rates materialize, but the main limiting factor for much in the way of accumulation will be the warm surface temperatures preceding the front. Another period of possibly more robust snow showers looks possible either very late Sunday night, or early Monday morning as a secondary cold front and an attendant mid level disturbance drops southward across the area. This potential will have to be monitored as it could occur during the early Monday morning rush. KJB && .LONG TERM... Issued at 221 PM CST Sat Mar 11 2023 Monday through Saturday... Highlights for the long term forecast period: * Lingering isolated/scattered snow showers and flurries on Monday * Unseasonably chilly for the first half of the upcoming workweek; milder heading into the latter half of the week * Precipitation likely to return to the area Thursday and/or Friday The vort max responsible for our late Sunday afternoon and Sunday night precipitation chances will likely be centered over or near the southern half of Lake Michigan come Monday morning. This feature will continue to wander off to the southeast throughout the day on Monday, and our forecast area will spend the day entrenched within a cold cyclonic flow regime as the associated low pressure centers at the surface and aloft remain east of our longitude. The ensuing cold air advection should ensure that skies remain overcast or mostly cloudy throughout the day and that high temperatures won`t make it out of the 30s. Low-level lapse rates will also steepen in response and should bring about some blusterier conditions for the morning and afternoon hours on Monday with regular north-northwesterly gusts into the 20-30 mph range appearing to be likely. The main question forecast question for Monday is whether there will be any additional snow showers lingering around and what the nature of those showers would be like, in terms of both coverage and intensity. The present thinking is that the residual forcing associated with the mid/upper-level trough and the steepening low- level lapse rates should be just enough to support isolated to scattered snow shower activity in our forecast area on Monday, but that the relative absence of quality moisture and the overall magnitude of the forcing at play should limit impacts to just occasional brief visibility reductions beneath the more coherent snow showers and perhaps some streaky dustings or coatings of snow occurring on colder surfaces. The exception to this could be in portions of northwest Indiana, where marginally favorable lake effect parameters may be able to support a longer duration snow band or two that could leave behind a narrow corridor of 1+" of snow on the ground when all is said and done. However, this is a low confidence scenario at this vantage point. Considering everything altogether, maintaining slight chance and chance PoPs across most of our CWA in lieu of the lower NBM PoPs seemed warranted at this time. Even if true snow showers didn`t materialize, think that some flurries may still be wrung out of the overhead stratocumulus deck over at least a portion of our forecast area on Monday. The magnitude of cold air advection should wane Monday night, but there appears to be a decent chance that the low cloud cover overhead will scatter out to some extent. Low temperatures appear likely to at least dip into the 20s either way, and if skies do clear out, then lows in the teens appear very attainable, at least across interior northern Illinois. High pressure will build into the region on Tuesday, and while clear skies should allow temperatures to bounce back a bit, the relatively cold starting point and marginally cold to neutral thermal advection should still keep Tuesday`s highs below normal for this time of year. Return flow on Wednesday will then kickstart the return of warm air advection, which will be further prolonged into Thursday as a developing surface low over the Great Plains maintains poleward low-level thermal and moisture trajectories to its east. A return of 50+ degree temperatures thus appears likely for most or all of our forecast area on Wednesday and/or Thursday, and it would not be surprising for some 60+ degree readings to be seen on Thursday as well if the aforementioned low pressure system is not as progressive as the fastest ensemble solutions currently suggest (most 12Z guidance was not that progressive with this system). The aforementioned developing low pressure system will be spawned as northern stream and southern stream waves embedded within western CONUS longwave troughing interact with one another Wednesday into Thursday. Some forecast guidance is suggesting that these two waves will phase nicely, culminating in a closed-off upper-level low that will spiral over the Great Lakes as we head into next weekend. Other guidance suggests that there won`t be much of any phasing between these two waves, and whatever low pressure system develops won`t hang around very long after passing through our area. Either way, the odds of rain occurring here sometime in the Thursday through Friday time frame look fairly good for a system that`s still 5-6 days away. Snow can`t be ruled out on the backside of this system, especially if a closed low does come to fruition over the Great Lakes, but this is still a lower confidence forecast item that, along with the finer details of the earlier rainfall, will become clearer in the coming days as additional forecast guidance continues to come in. Ogorek && .AVIATION... For the 00Z TAFs... Aviation Forecast Concerns: * Snow develops this evening, with a period of IFR vis and minor accumulations overnight. IFR ceilings linger at least into Sunday morning before improvement to MVFR. * Snow tapers off by morning and likely becomes a mix of snow and drizzle. Period of heavier convective rain/snow showers possible in the afternoon. * East winds tonight become southeast Sunday morning, then south briefly Sunday afternoon ahead of a cold front. Winds shift west behind that front Sunday evening, with some gusts around 20 kt. Light snow will spread across the area this evening as a mid- level disturbance currently over IA approaches. There could be a very brief rain/snow mix as precipitation begins, but should change to all snow fairly quickly as intensity picks up. The strongest forcing looks to be from late evening to past midnight, when IFR visibility and minor accumulations are likely. Weakening ascent and decreasing saturation in favored snow-growth temperature levels suggests snow will weaken in intensity by the pre-dawn hours, with visibilities improving to MVFR. Moist low levels will likely maintain IFR ceilings into Sunday morning however. A second upper trough over the upper Midwest will maintain weaker forcing across the region through the day Sunday, with lighter intermittent light snow/flurries. Several models indicate loss of saturation in the ice-bearing thermals range and thus may see a mix of light snow and drizzle especially during the midday and afternoon hours. A period of heavier snow/rain showers is possible during the mid-late afternoon hours, as low-level lapse rates steepen ahead of an approaching cold front. Scattered snow showers may persist behind the front Sunday evening, though with low confidence in coverage, as somewhat drier air spreads in. Easterly winds tonight will turn southeast Sunday morning, then light southerly ahead of the cold front during the afternoon. Behind the front, winds will shift to the west-northwest, and will become somewhat blustery with gusts around 20 kts. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Lubbock TX
514 PM CST Sat Mar 11 2023 ...New AVIATION... .SHORT TERM... (This evening through Sunday) Issued at 216 PM CST Sat Mar 11 2023 Current RAP analysis has the surface low over eastern Kansas with west winds across the forecast area this morning and afternoon. Winds have already begun to increase this morning with 30 to 40 mph sustained winds and gusts up to 50 mph, especially across the far southern Texas Panhandle and northern South and Rolling Plains. Elsewhere winds will be breezy at 15 to 25 mph with some gusts up to 35 mph possible. A Wind Advisory remains in effect until 7 PM CST across the southwest and south central Texas Panhandle and much of the South Plains. Temperatures off the Caprock are warming quite nicely this afternoon into the 80s, with areas along the Caprock slightly cooler in the 70s. As of 1 PM CST, the cold front associated with the surface low is located in the Southern Texas Panhandle over Amarillo. The front is expected to approach the far southern Texas Panhandle in the next few hours where the boundary will stall across the northeast zones as the surface low moves farther east. Temperatures immediately behind the front across the Texas Panhandle this afternoon are in the upper 50s to 60s. Therefore, temperatures in the next few hours may be halted across the far southern Texas Panhandle behind the fast approaching cold front. Tonight, mostly clear skies and light northeast to east winds as the front continues to push southward will give way to brisk temperatures in the 30s to lower 40s. A few areas across the far southwest Texas Panhandle may approach near freezing low temperatures by tomorrow morning. Heading into tomorrow, zonal flow will continue aloft with a few high clouds possible. The cold front is expected to stall again near the southwest to western South Plains with west winds and temperatures in the upper 60s to lower 70s ahead of the frontal boundary. Otherwise, east to southeast surface winds are expected across much of the forecast area which will contribute to cooler temperatures in the upper 50s to lower 60s. A few models have a slight chance for some light rain showers to generate across the west starting in the late afternoon hours, mainly along that surface boundary. && .LONG TERM... (Sunday night through next Friday) Issued at 216 PM CST Sat Mar 11 2023 A cold front will continue pushing westward across the FA late tomorrow evening and will reach central New Mexico by Monday morning. Guidance continues to show the possibility of rain showers late tomorrow night/early Monday behind the front as a weak upper short wave moves over the region. Some precip does look to be possible, but if it occurs it would likely be lighter than portrayed by the models as the main forcing will be from isentropic lift. Precip chances will be better late Monday through late Tuesday morning as a more defined upper shortwave develops near the Four Corners and pushes southeastward towards the FA. Moisture should still be in place across the region as surface winds continue to be out of the southeast. Rain chances will push to our east by midday Tuesday following the exit of the shortwave. We will begin a warming trend into the upper 70s/low 80s by Wednesday as upper ridging sets up over the region. This will quickly change by Thursday. An upper trough is progged to move into northern California early Wednesday, amplify, and push eastward towards New Mexico by late Wednesday evening. A developing surface low ahead of the upper trough would allow for a windy Wednesday evening. While models are in agreement with the development and passing of the upper trough, they disagree on the tilt which, in this case, would determine the validity of forecasted precip. The GFS keeps the trough more positively tilted as it approaches the region and the ECMWF has a neutral to slightly negative tilt. The positive tilt would result in a dry forecast where as the ECWMF`s solution would allow for better precip chances. These systems tend to be more positively tilted and dry, but there is still plenty of time for the models to smooth out the details. Regardless of the outcome, the setup would allow for windy conditions on Thursday morning ahead of a cold front, and windy conditions behind the cold front Thursday afternoon and evening. && .AVIATION... (00Z TAFS) Issued at 514 PM CST Sat Mar 11 2023 VFR prevails for the TAF period. Cold front has crossed KCDS and will continue to move southward throughout the remainder of the evening, with winds shifting to the north at KPVW and KPVW prior to 06Z tonight. Winds will continue to veer during the overnight hours and into tomorrow with speeds generally around 10 kt. Sincavage && .LUB WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 7 PM CST this evening for TXZ021>024-027>030- 033>036. && $$ SHORT TERM...11 LONG TERM....51 AVIATION...09
Area Forecast Discussion
National Weather Service Memphis TN
826 PM CST Sat Mar 11 2023 ...New UPDATE... .UPDATE... Issued at 819 PM CST Sat Mar 11 2023 Showers and storms have developed this evening across the Mid South. Strong to severe storms will move into north Mississippi later tonight with large hail and damaging winds being the main threat. Following the passage of the cold front, cooler and dry weather will prevail through midweek. Freezing temperatures will are expected Monday morning over parts of northern West Tennessee. && .SYNOPSIS... Issued at 238 PM CST Sat Mar 11 2023 Showers and thunderstorms will move through the Midsouth tonight, along a fast-moving cold front. A few of these thunderstorms will be capable of producing large hail, damaging winds and localized flash flooding, mainly during late evening and early overnight hours. Showers and isolated thunderstorms may linger over north Mississippi Sunday morning. Following the passage of the Sunday`s cold front, cooler and dry weather will prevail through midweek. Freezing temperatures will are expected Monday morning over parts of northern West Tennessee. Freezing temperatures are forecast over most of the Midsouth Tuesday and Wednesday mornings, with a hard freeze likely over much of West Tennessee early Tuesday and Wednesday. PWB && .DISCUSSION... (This evening through next Friday) Issued at 238 PM CST Sat Mar 11 2023 Early afternoon GOES water vapor imagery showed a low amplitude upper level ridge over the lower MS River valley, downstream of trough axis lifting through the Great Plains. Warm advection downstream of the trough axis is contributing to modest elevated instability over the Ozarks, into western portions of the Midsouth. Convection may be additionally aided by the right entrance region of a 90kt 250mb jet streak over the lower Ohio River Valley. Early afternoon SPC Mesoanalysis page showed 60kt of 0-6km bulk shear over the Midsouth, likely aiding in the organization and maintenance of showers and thunderstorms. The midlevel trof will lift into the MS River valley this evening and early overnight, as diffluent flow flow aloft overspreads the Midsouth. Showers and thunderstorms will focus along a southeast- moving surface cold front and attendant frontal wave. 18Z HRRR depicts modest prefrontal mixed layer CAPE of 500 to 800 J/kg. Midlevel lapse rates prevail near 6.7 C/km late this evening, decreasing to around 5.5 C/km overnight. This is about the time the HRRR depicts a 60kt 700mb speed max arrival, more bowing structures and tendency for forward-propagating storms. The implication: A marginal large hail threat over the MS River delta this evening will likely transition to a marginal damaging wind threat over north MS overnight. Overnight flooding rain threat may lessen with the more progressive storm evolution depicted by the HRRR. Dry and cooler conditions will prevail from Sunday afternoon through the middle of next week, as a continental polar airmass prevails. With dewpoints in the upper 20s to lower 30s, nighttime freezing temps will be possible as soon as the pressure gradient relaxes and winds go light. This appears most likely to occur Tuesday and Wednesday mornings, with hard freezes over West TN, and at least a light freeze over most of the Midsouth. In the interim, Monday morning could see temps drop to around freezing over northwest TN. With strong mixing and winds Monday morning, it likely feel the coldest morning of the week, with wind chills dipping to the low 20s from far northeast AR through the MO boot heel and and far northern West TN. Monday morning wind chills will drop to the lower 30s over north MS. A Freeze Watch will likely be issued in a subsequent forecast package. The next rain event will arrive late Thursday into Friday, associated with a progressive longwave trough. Severe thunderstorm threat with this system will likely remain limited, given the limited time for a robust low level instability axis to develop. PWB && .AVIATION... (00Z TAFS) Issued at 538 PM CST Sat Mar 11 2023 Spotty shower and thunderstorm development is currently ongoing across the Mid-South and is expected to continue through the overnight hours, becoming more widespread by midnight. An approaching cold front will allow for winds to become northerly at 10-12kts by sunrise. As this front moves through, IFR ceilings are possible across all sites, but this will only last a few hours before returning to MVFR by Sunday afternoon. ANS && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$ PUBLIC FORECAST...MJH AVIATION...ANS
Area Forecast Discussion
National Weather Service Pocatello ID
123 PM MST Sat Mar 11 2023 .SHORT TERM...Tonight through Sunday night. Early afternoon satellite imagery was showing a weak to modest west flow across the WRN states in the wake of yesterdays storm system. Looking upstream, a low pressure system was centered off the WRN Canadian coast. Numerical models show a weak disturbance cycling through the base of the low into NRN California Sunday morning with attending clouds and moisture spreading into the region during the day for a chance of snow showers across the southern and central mountains during the day. As this disturbance lifts NE Sunday night, the low off the WRN Canadian coast begins to amplify ingesting more Pacific moisture into the strengthening SW flow across the region. This should result in a better chance of seeing snow showers across a broader area of SE Idaho Sunday night, particularly the CNTRL mountains where 1 to 2 inches of additional snowfall may be realized. Temperatures remain below normal for this time of year. Huston .LONG TERM...MONDAY THROUGH NEXT SATURDAY. Active wx remains on tap for the Mon-Wed timeframe next week, with consensus growing in the most significant rain/snow falling in a roughly 48 hour period from Mon eve through Wed eve, courtesy of 2 shortwave troughs ejecting inland off the Pacific loaded with moisture. This event will remind us spring is coming, as snowfall accumulations will be HIGHLY elevation-dependent. Tue, except windy conditions from the SSW, with the ern Magic Valley and lower Snake Plain downsloped and thus warm and relatively drier (light showers), with significant snow falling in the mntns, especially surrounding the Wood River Valley. Most accumulations will occur above about 6,000 feet. Wed, expect a cold front shifting strong/gusty winds into the west, and the most significant snowfall gradually shifting into the ern highlands, again with most accumulation above about 6,000 feet, with everything ending Wed night. Storm totals will likely reach 1-2 feet in the mntns, but an inch or less from the lower Wood River Valley down across the Magic Valley, Snake Plain, and srn highland valleys as temps will support mostly rain there. Highs in the 40s, and lows perhaps not dropping below freezing Mon/Tue nights across the ern Magic Valley, lower Snake Plain, and srn valleys, combined with rain, means we will need to closely watch for localized flooding, likely to a greater extent than what we started to see with yesterday`s event in a few spots. The ECMWF EFI continues to highlight climatologically high rain/snow for this event with a more modest overall response for wind, and our snowfall forecast currently sits comfortably near the NBM 50th percentile with minor adjustments made in valley bottoms. Keep in mind the rain/snow line will fluctuate diurnally between about 5,500 feet and 6,500 feet. 500mb cluster analysis continues to show a hint of uncertainty as to exactly how quickly the second shortwave will clear out Thu (currently we are forecasting a mostly dry day), but stronger consensus in the ensembles by Fri at which point an amplified (although progressive) ridge will give us a break. 01 && .AVIATION...The next 24 hours will be characterized by a break in impactful wx for southeast Idaho terminals under shortwave ridging, with moderate to high confidence in VFR cigs/vsbys just about everywhere along with light winds less than 10kts. Model guidance does suggest the sfc will be quite moist tonight (supported by yesterday`s widespread rain and snow), yet most models are not developing fog/low stratus issues. A hint of low stratus appears in MOS guidance near KIDA along with some development on the HRRR between about 08z and 17z Sun AM (especially just west of the terminal), so while confidence is very low in this occurring (perhaps a 10% chance), we`ll be keeping an eye on it. Sun, expect increasing mid-level clouds from SW to NE throughout the day. Precip will be moving our way associated with the next approaching shortwave trough, but the HREF suite "washes out" model-simulated radar echoes as they try to penetrate into the forecast area, with little consensus on organized rain/snow at any given location through Sun eve. At this time, confidence is at least moderate in dry conditions at KPIH, KIDA, and KDIJ, but lower for KSUN and especially KBYI (where we have gone ahead and introduced VCSH after 13z Sun). Beyond, expect a period of wet, windy, and more impactful wx for aviation Mon through Wed. 01 && .HYDROLOGY...Avalanche debris continues to partially block the Big Wood River near Hailey threatening a number of homes in the Della Vista subdivision. Thus the Flood Warning was extended for another 24hrs. .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$
Area Forecast Discussion
National Weather Service Portland OR
249 PM PST Sat Mar 11 2023 .SYNOPSIS...A weak atmospheric river and associated frontal system will impact the region with widespread rain Sunday through Monday, but river levels are not expected to reach flood stage. Snow levels will increase to over 5000 feet Sunday morning and afternoon as a warm front lifts northward across the area. Snow levels will then fall behind a cold front on Monday, lowering to around 2000 feet Monday evening. Precipitation should be more disorganized and showery Monday night through Wednesday before drier and warmer weather arrives on Thursday due to a transient shortwave ridge passing over the Pacific Northwest. Chances for light rain return on Friday as a weak front sweeps eastward across western OR/WA. && .SHORT TERM...Saturday night through Tuesday...Models and their ensembles remain in agreement for moist southwesterly flow aloft Saturday night through at least Monday afternoon. It appears moisture will peak Sunday night into Monday as the polar jet to the north buckles southward and merges with the sub-tropical jet to the south and sends a 120-130 kt jet right over Oregon on Monday. This will help bring a plume of sub-tropical moisture into the region, and the GEFS/EPS remain in good agreement that IVT values will peak somewhere between 250-500 kg/ms as a weak atmospheric river impacts northwest OR and southwest WA. At and near the surface, the deterministic NAM/GFS/EURO are all showing a warm front lifting northward across the forecast area Sunday morning with a weak AR pushing into the area behind the warm front as PWAT values increase to 0.7-0.8 inches. Overall forcing looks very weak during that time, suggesting rain will generally be light in intensity rather than heavy. Hourly rain rates from the HRRR and UWWRF on Sunday only peak around 0.1-0.15 inches per hour. This is nowhere near enough to prompt concerns for flash flooding, river flooding, and/or debris flows. The NBM continues to show snow levels rapidly increasing to over 5000 feet behind the warm front, thus limiting winter weather impacts to the high Cascades above pass level. This is good news for anyone who is planning on driving over the Cascade passes on Sunday, as precipitation will be in the form of rain or a rain/snow mix rather than all snow. However, snow levels will begin to decrease late Monday into Tuesday morning behind a cold front that is set to push eastward across the area Monday morning and afternoon. Both the GFS and the EURO depict much stronger Q-vector convergence and mid-level frontogenesis with the cold front when compared to the warm front, and the latest CAM guidance is simulating a large swath of light to moderate stratiform rain over the area along and ahead of the cold front. This round of rain looks to be heavier compared to the warm frontal precipitation, but hourly rain rates are still nowhere near our thresholds to prompt concern for debris flows over our recent burn areas in the Cascades. Precipitation should quickly transition to scattered showers behind the cold front Monday evening. Given the showery nature of precipitation behind the front when snow levels are set to decrease to 1500-2000 ft Monday night, not expecting overly significant snow amounts as pass level (generally just an inch or two, however 3-5 inches is possible for Willamette Pass where precipitation appears heavier). Below the snow level, forecast rain amounts have not changed much. Still expecting 1-1.5 inches of rain from 5 AM Sunday through 5 AM Tuesday across the interior lowlands and 1.5-2.0 inches at the coast. Generally expecting 2-3 inches over the mountains, but locally higher amounts up to 4 inches are possible. Fortunately, these rain amounts are not high enough to prompt river flooding concerns. Tuesday currently looks drier as the AR shifts further south and focuses mainly on southwest OR and CA. That being said, some model guidance (including the 12z deterministic EURO) does shift an area of heavier precipitation into northwest OR, especially south of Salem. Meanwhile, the deterministic GFS keeps our area dry on Tuesday except for the Lane County Cascades and foothills. Will leave NBM PoPs for Tuesday given the uncertainty, which shows a 30-50% chance of rain, except 60-70% in the Cascades. -TK .LONG TERM...Tuesday night through Saturday...The GEFS/EPS/CMC ensemble mean for 500 mb heights are all showing a transient upper level trough pushing eastward across western OR/WA Tuesday night with an attendant cold front at the surface. The EURO depicts a slightly stronger front compared to the GFS. In fact, the GFS suggests the front will quickly decay after moving inland, resulting in only light showers for the mountains with mainly dry conditions for the lowlands Tuesday night and Wednesday. The EURO brings decent rain amounts even to the lowlands, around 0.25 inches or higher. Regardless of the outcome, overall impacts look low and snow amounts in the Cascades look too low to prompt winter headlines. Models and their ensembles are still in excellent agreement on Thursday, showing a shortwave ridge passing over the region. This will bring dry weather and warmer temperatures with highs at least in the mid to upper 50s. The NBM 1D Viewer is still showing a 15-20% chance for high temperatures of 60 degrees or warmer Thursday afternoon across the Willamette Valley and a 5-15% chance along the coast, highest over the central coast and southern Willamette Valley. The outcome will ultimately come down to cloud cover conditions; if skies wind up mostly sunny then highs near 60 would most likely materialize. It appears Thursday`s pleasant weather will be short-lived, as rain returns to the forecast Friday with temperatures cooling slightly at the surface and aloft. -TK && .AVIATION...00Z TAFs: At 22Z satellite imagery showed a weak warm front over southwest Washington lifting to the north. Flight conditions have improved to VFR across the area, with cigs generally 060 to 080. Expect VFR to prevail across the area through at least 06Z Sunday. Cigs begin to lower across the south half of the area after 06Z Sunday as a warm-frontal boundary draped across northern California drifts north. Increasing -RA across the south after 10Z will result in MVFR conditions. The frontal boundary reaches the Columbia River around 15Z Sunday. Expect predominant MVFR conditions after 15Z Sunday, with areas of IFR possible along the coast. For detailed Pac NW aviation weather information, go online to: KPDX AND APPROACHES...At 22Z cigs 060-070 were noted at the terminal and vicinity, except 035-045 in the Tualatin River Valley. Cigs AOA 080 to prevail Saturday evening. Cigs expected to lower to around 070 by midnight. Light rain develops between 12Z and 15Z, with a greater than 70 percent chance of MVFR starting at 15Z. Expect predominant MVFR after 15Z. Weishaar && .MARINE...At 1 PM, satellite imagery showed an upper level low over the northeast Pacific west of Hadai Gwaii and a moist frontal boundary along 40N streaming into northern California. Wind speeds were generally 15 to 20 kt. Little change through Sunday morning. Models show a 1000 mb surface low centered near 45N 128W by 11 AM Sunday. Expect increasing southerly wind over the southern waters around midday and then spreading north through the afternoon. The surface low is forecast to move onshore near the southern tip of Vancouver Island early Sunday evening. Model guidance shows 30 to 35 kt boundary layer wind speeds (used as a proxy for gusts) developing over the waters around 5 PM Sunday. The National Blend of Models (NBM) shows a 65-70 percent chance of gale force gusts at buoy 46050 Sunday night. The high resolution ensemble mean model output indicates 35 kt gusts over a majority of the area 5 PM Sunday. Based on the above, will upgrade the Gale Watch to a Gale Warning valid 5 PM Sunday to 2 AM Monday, except starting at 7 PM for PZZ251 and PZZ271, including the Columbia River Bar. This looks to be a marginal, low-end gale event. The wind shifts to westerly late Sunday night, with wind speeds decreasing to around 15 kt by 7 AM Monday. Another rapidly-developing low pressure well west of the north California waters early Tuesday, is forecast to remain south of the forecast area. This results in general northerly wind over the waters. Longer range models show a fairly strong frontal system impacting the waters late next week. Mixed swell continues over the area through early next week. However, overall wave heights will be 7 ft or less through early Sunday afternoon. Combined seas peak 10 to 11 ft late Sunday night, with a substantial wind wave component. Wave heights settle to around 6 ft Monday. Spectral model guidance suggests wave heights approach 20 ft late next week. Not sold on this outcome just yet, as the NBM guidance shows 12-15 ft. The 90th percentile NBM wave heights valid 11 PM next Saturday are 15-19 ft. Weishaar && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory from 2 PM to 7 PM PDT Sunday for Coastal waters from Cape Shoalwater WA to Cape Falcon OR out 10 NM- Columbia River Bar-Waters from Cape Shoalwater WA to Cape Falcon OR from 10 to 60 NM. Gale Warning from 7 PM Sunday to 2 AM PDT Monday for Coastal waters from Cape Shoalwater WA to Cape Falcon OR out 10 NM- Columbia River Bar-Waters from Cape Shoalwater WA to Cape Falcon OR from 10 to 60 NM. Small Craft Advisory from 11 AM to 5 PM PDT Sunday for Coastal waters from Cape Falcon OR to Cape Foulweather OR out 60 NM. Gale Warning from 5 PM Sunday to 2 AM PDT Monday for Coastal waters from Cape Foulweather OR to Florence OR out 10 NM.Coastal waters from Cape Foulweather OR to Florence OR from 10 to 60 NM. Small Craft Advisory from 8 AM to 5 PM PDT Sunday for Coastal waters from Cape Foulweather to Florence OR out 10 NM- Waters from Cape Foulweather to Florence OR from 10 to 60 NM. && $$ Interact with us via social media:
Area Forecast Discussion
National Weather Service Raleigh NC
955 PM EST Sat Mar 11 2023 .SYNOPSIS... Weak high pressure will build east into the region through tonight. Cold air damming will develop across central NC Sunday, north of an area of low pressure and associated frontal zone that`s forecast to track east across GA, SC, and southern coastal sections of NC through Sunday night. && .NEAR TERM /TONIGHT THROUGH SUNDAY NIGHT/... As of 950 PM Saturday... Only minor changes were made with the evening update. Widespread high clouds across the region that had been in place earlier are largely dissipating, and some spots have begun to radiationally cool particularly in the NE as current temperatures are 36F at KTDF, KHNZ, and KIXA. Widespread clouds will begin to move in from the west in a few hours, but they should arrive late enough in the NE for low temperatures of about 33-35F there, where some patchy frost will be possible. Still not expecting any subfreezing temperatures, and ensemble probabilities of this occurring are quite low. In the west, temperatures should stop falling once the clouds arrive and until precipitation moves in. Dew points are in the mid-to-upper-20s across the northern Piedmont as expected with the surface high pressure wedging down, but did raise them a bit in the south and east as they are in the 30s there. As for precipitation, delayed its arrival slightly based on the 00z high-res guidance (including the HRRR, RAP, and NAMNest). Also slightly cut back the area of forecast 0.1-0.2" snowfall amounts tomorrow morning across the northern Piedmont, as a later arrival of precipitation would tend to favor less frozen, and snow depth forecasts in the latest HRRR and RAP are now essentially zero. Still expecting very minimal to no impacts especially given the very warm soil temperatures. Otherwise, the previous discussion is below: As of 400 PM Saturday... Patchy frost possible over the nrn Coastal Plain tonight. A wintry mix of rain and snow will develop late tonight-Sunday morning over the nrn NC Piedmont, which may briefly change to all snow for a few hours near the VA border Sun morning, but with little to no accumulation as it mostly melts as it falls. Shortwave ridging will build from the Great Lakes east to the mid Atlantic tonight, then offshore through Sunday night, through which time and downstream of a closed mid-level cyclone in the nrn stream that will move from the nrn Plains to the upr Great Lakes. Meanwhile, and more importantly for cntl NC, a lwr amplitude perturbation in the exit region of an energetic/active srn stream will stream from the cntl Plains this afternoon to the OH Valley and cntl Appalachians through early Sunday. A strong mid-level WAA regime and nw to se-oriented band of 700 mb frontogenesis will precede and accompany that feature and spread from the mid MS Valley/mid-South this afternoon to the srn mid Atlantic by 09-12Z Sun. Lwr-level WAA and isentropic lift will follow and overspread cntl NC through the day and early nighttime hours Sun. At the surface, the center of weak (~1018 mb) high pressure will ridge across the mid Atlantic tonight, then offshore, but with associated surface dewpoints in the 20s that will have been deposited over VA/NC and favor hybrid to in-situ cold air damming Sun-Sun night. Around the srn periphery of that damming regime, a lead low will migrate newd into the TN Valley/srn Appalachians Sunday, then yield to a secondary/coastal low forecast to develop along and offshore the NC coast, along the wedge front, Sunday night- early Monday. Considerable cirrus/cirrostratus has already overspread SC and srn NC this afternoon; and this high-level moisture will continue to overspread the remainder of the Carolinas overnight - slowest and thinnest over nern NC, including the nrn/cntl Coastal Plain. Those areas may radiationally-cool into the lwr-mid 30s and favor the development of patchy frost. Otherwise and elsewhere, temperatures will cool into the upr 30s to mid 40s this evening, steady as clouds thicken and lower overnight, then diabatically cool into the mid 30s where and when precipitation overspreads the Piedmont through Sun morning. The trend in model guidance since last evening has been for a faster arrival of that precipitation band late tonight-early Sunday. A combination of top-down and forecast partial thickness/TRENDS nomogram favor the presence of a deep/near freezing isothermal layer aloft and melting of snow in a shallow, above freezing surface layer that will likely support a larger and more prolonged area of rain/snow mix or even all snow across the nrn NC Piedmont Sunday morning. That appears to be the case after an initial period of light rain incompletely saturating/cooling the sub-cloud layer at onset, then both warming and drying aloft, and insolation from a mid- March sun angle, during the afternoon, which would favor a changeover to rain/drizzle that will continue through Sunday night. ***However, most/all snow should melt as it falls*** owing to 1) very warm soil temperatures that have ranged from mid 40s to lwr 50s F the past couple of mornings to 50s to near 60 F this afternoon, 2) above freezing air temperatures except for perhaps a 2-3 hr period when heavier precip rates would favor "melting out"/ diabatically- cooling to 32-33F an otherwise ~750-1000 ft AGL above freezing surface layer, and 3) a mid-March/late winter sun angle through the morning-midday hours. Any accumulation of perhaps a tenth to two would be limited to any period of all snow and confined to elevated surfaces near the VA border. Otherwise it will be a chilly and raw/wet end to the weekend, with periods of rain and drizzle lingering through much of Sun night, and with a small diurnal range of highs in the upr 30s north to low-mid 40s south, and lows just a degree or three cooler Sun night. Rainfall amounts are expected to range around one half inch, slightly lower across the nrn Piedmont and higher across the srn tier. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... As of 218 PM Saturday... Monday: The sfc low will quickly exit offshore early Monday morning leaving behind just lingering stratiform rain across our far eastern zones. Behind the system, low-level stratus will likely linger into Monday afternoon, before another sfc cold front finally clears cloud cover late Monday night. Given the extensive cloud cover expected for much of Monday, max temperatures will struggle to reach above the mid to upper 50s for much of our area. Low-level thicknesses are expected to plummet into the 1280 to 1290m range overnight Monday. However, given that residual stirring of winds expected, don`t believe we`ll see strong radiational cooling as a result. As such, the current forecast calls for sub freezing lows across the NW (upper 20s) to slightly above freezing lows elsewhere (lower 30s). Thus, future shifts may need to issue a freeze warning for those in the northwest Piedmont Monday night. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 218 PM Saturday... Upper pattern through the extended: An anomalous upper low will move across the upper Midwest and through the New England Monday through Wednesday morning promoting wnwly flow aloft over central NC. Mid- level riding will then build across the central US promoting nwly flow aloft over our area Wednesday/Thursday. Flow will then turn more swly Friday through Saturday as the next upper trough approaches our area. Tuesday through Thursday: Strong CAA is expected to develop across our area as chilly sfc high pressure over the central US eases eastward. Increasing nwly flow through the depth of the atmosphere will promote anomalously dry conditions (PWAT ~20 to 25% of normal) Tuesday through much of Thursday. Additionally, good mixing should promote gusty conditions Tuesday and Wednesday afternoons. Tuesday in particular will likely see frequent gusts of 25 to 35 mph especially across northern areas. Given the anomalously dry air expected during this period, the pattern will favor increased fire weather danger concerns especially Tuesday afternoon. Sub-freezing conditions appear increasingly likely across most of central NC Tuesday night into Wednesday morning as low-level thicknesses drop to near record lows for mid-March. Additionally, ensemble probabilities for sub-freezing temperatures range from 100 % in the Triad to 55% in the southern Coastal Plain Wednesday morning. Thus, a freeze warning will likely be needed for much of central NC Tuesday night/early Wednesday morning. Winds decouple Wednesday night promoting another round of chilly overnight lows in upper 20s/lower 30s. Daytime highs Tuesday/Wednesday will remain chilly in the upper 40s to upper 50s (~10 degrees below normal). Near to just above normal highs return Thursday afternoon in the lower to mid 60s. Friday through Saturday: The chilly sfc high will move offshore by Friday morning promoting sswly low-level flow and warmer temperatures across our area. Daytime highs will reach well above normal into the upper 60s/mid 70s Friday (overnight lows in the mid 40s). Rain associated with an approaching sfc cold front is expected to approach and push through central NC sometime late Friday through Sunday morning. Latest 12Z deterministic guidance (as well as ensemble probabilities for measurable precip) has slowed down the arrival of precip compared to previous runs. Thus, have trended the POPs down for Friday compared to the inherited previous forecast, but with highest POPs currently still forecasted on Saturday. This will likely need to be altered, however, as uncertainty decreases closer to next weekend. Highs on Saturday will depend on cloud/cover precipitation, but as of now the forecast calls for upper 50s in the NW to upper 60s in the SE. Overnight lows follow a similar gradient in the mid 30s (NW) to around 40 in the far SE. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... As of 640 PM Saturday... 24 hour TAF period: High confidence VFR conditions will prevail through about midnight at all terminals. Cigs will thicken and lower quickly between 06Z and 12Z Sun, with sub-VFR conditions earliest (08Z-10Z) at KINT and KGSO, then subsequently at KRDU, KRWI and KFAY. Cigs will likely drop into the IFR/LIFR range everywhere by 15Z at all terminals and remain there through the end of the TAF period. Visbys will also drop to between 1SM and 4SM everywhere. Additionally, there could be a brief period of some SN mixed with the RA from onset through about 15Z, most likely at KINT, KGSO and possibly KRDU, then change over to and remain all liquid through the end of the period. Finally, there continues to be a signal for LLWS potential owing to the presence of a 35-40 kt LLJ late Sun aft through Sun eve, primarily at KFAY, KRDU, and KRWI, as the low tracks northeast along the Carolina coast. Looking ahead: Light rain/drizzle could linger into Sun night, while LIFR/IFR conditions will persist through Sun night/Mon morning. VFR conditions should return by Mon afternoon and prevail through mid- week. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL NEAR TERM...Danco/MWS SHORT TERM...Luchetti LONG TERM...Luchetti AVIATION...KC