Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/26/21

Area Forecast Discussion
National Weather Service Boston/Norton MA
1046 PM EDT Sun Apr 25 2021 .SYNOPSIS... Gusty and drier conditions tonight and Monday. Turning milder for Tuesday into Wednesday, with limited chances for showers or thunderstorms across northern and western Massachusetts on Wednesday. A cold front may bring more widespread rains to the region on Thursday with a cooldown in temperatures. Late in the week into the weekend features continued unsettled through generally dry conditions, with temperatures trending near to below average for late April. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 1030 PM Update... No changes in the latest update. Forecast remains on track. 725 PM Update: Coastal low well southeast of Nantucket continues to pull away toward Georges Bank. Outside of very spotty back-end showers across Cape Cod, drier NW flow is increasingly taking hold and this is allowing for more substantial breaks in overcast cloudiness. Expect more of the same thru late evening, with clouds lifting and scattering out with most areas trending mostly clear by midnight. Have reduced PoPs to sub-mentionable levels/dry for the remainder of the tonight period. Focus then turns to cold/dry advection and increasing breezy to gusty conditions. On the winds, I incorporated a bit more of the HRRR winds as it and the RAP guidance seem to have a decent enough handle on the onset of gustiness. Expect NW gusts to begin late evening/midnight across western MA/northern CT and into the early overnight to pre-dawn Monday hrs across central/eastern MA and RI. Though we are looking at cold advection for the remainder of the night, going to have to keep an eye on model consensus low-30s to near 40 degree low temperatures. Though the overall idea of cooler temps west and somewhat milder east makes sense, possible small upward adjustments to temps could be needed in later updates as guidance can sometimes trend too cold in well mixed/breezier wind regimes. Previous discussion: Low pressure passing south and east of Nantucket will move off toward Nova Scotia tonight. Western edge of the rain was moving through Eastern Massachusetts. Expect the rain to taper off by evening. Satellite shows breaks in the clouds over Western CT and Western MA, more breaks over NY. These will work east, bringing clearing skies tonight. Pressure gradient starts the night rather light although favoring a north to northwest wind. As a northern stream shortwave moves past, expect the surface pressure gradient to tighten, bringing increasing northwest sustained wind. Cold advection by this wind will generate mixing that will bring stronger gusts to the surface. Winds aloft will increase to around 25 kts overnight, so expect gusts of 25 to 30 mph overnight. With clearing skies and cold advection, expect temperatures to fall into the 30s and low 40s. Coldest temps will be along the Berkshire East Slopes, which will be 30-32. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Overview... Shortwave that passes overhead tonight digs and closes off as it moves to the Maritimes Monday and Monday night. Upper ridge approaches from the west Monday night. Monday... A sharp pressure gradient continues into Monday. This along with cold advection mixing from above will generate gusty northwest winds. Winds in the mixed layer will reach 30 kt, so expect gusts of 30 to 35 mph during daytime mixing. There is a chance that winds aloft could reach 35 kt, which would support gusts to 40 mph. Mixed layer to 850-mb would support max temps in the mid 50s, and to 800-mb around 60. So the forecast range for max temps will be mid 50s to low 60s, coolest in the hills. It will be a dry airmass, as dew points are forecast to fall into the 20s. Monday night... The pressure gradient diminishes at night as high pressure builds in. Expect mainly clear skies at first, then some mid- high clouds late at night. Temps should again fall into the 30s and low 40s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Highlights... * Warming trend Tues into Wed. Possible 80 degree readings Wed for interior western New Eng. Late-day/evening showers, possible t- storms at least for northern MA on Wed. * Still considerable uncertainty on rain chances Thurs, but trending wetter than not with cooler temps. * Unsettled Fri into Sat, with temps trending near to below-avg by early into the weekend. Details: Tuesday and Tuesday Night: Upper low from Monday night will continue to pull away, and with it comes an anticipated warming trend starting Tuesday, with rising 500 mb heights and surface ridging to our south. Should see plenty of sun, though rising temperatures through the 925-850 mb layer will continue to support a shallower mixing depth. With westerly winds, highs well into the 60s should be fairly common, even to the eastern MA coast. In the interior, highs should reach the lower to mid 70s with an additional boost from downsloping winds. A bit more uncertainty specific to PoPs/rain chances for Tuesday night, as a warm front approaches from the WSW. Models vary on the exact placement and its NE advancement, but there is some elevated instability evident rooted around 800 mb in NAM-based soundings. 12z ECMWF also shows K-indices running around 30-33 units. Each of these sources support a potential risk for showers with embedded thunder, but warm-frontal lift appears better further SW than into Southern New England. For now, have left the forecast dry with an increase in clouds advertised, but it is possible that PoPs/thunder could be introduced as confidence increases. Wednesday into Wednesday Night: Confidence in the forecast unfortunately continues to trend lower than average into the mid to latter part of the workweek. Warm front from Tuesday night looks to lift back northward early on Wednesday, with warm-sector air mass overspreading much of Southern New England. Despite a considerable amount of cloudiness, Wednesday should be the mildest day in the period with high temperatures in the interior reaching well into the 70s (to near 80 in the CT Valley). While most of the first part of the day should be on the dry side, the concern and uncertainty in the forecast comes later Wednesday into the evening. While the GFS and Canadian GEM don`t necessarily subscribe to this solution, the NAM and the 00/12z ECMWF depict a weak/subtle surface low progressing ESE from Ontario into eastern NY/western New England later Wednesday. Mid-level lapse rates are still rather notable at values around 6-6.5 C/km, and K-indices again rise into the 30-35 unit range. Especially in our northern areas (thinking north of the Mass Pike and especially along/north of Route 2), we could have a period of thunder associated with strengthening 700-500 mb winds (effective shear ~45-50 kt) and about 500-800 J/kg of MUCAPE per NAM soundings at Orange, MA. After some coordination with neighboring WFOs, did opt for slight chances for thunder north of the Pike thru early evening, then trended towards showers for most of the rest of the forecast area into the evening hrs. For the evening, lows look quite mild for late-April with values into the 50s, with similar dewpoints. Thursday into Friday: As mentioned, still a considerable level of uncertainty in the details, but most of the global models are coming around to the idea of wetter conditions for Thursday along a cold front, along with cooler temperatures. The ECMWF is something of an outlier in showing Thursday being largely dry in the wake of the Wednesday/Wednesday night activity, with another wave then arriving later Thursday into Thursday nite. Raised PoPs about 10% or so over NBM which brings solid Chance PoPs during the day and at night on Thursday. Cooler highs in the 60s to near 70, lows in the upper 40s to near 50. Differences in model solutions then become even more apparent on Friday. The more progressive Canadian GEM/GFS show a unsettled NW flow regime with cooling thermal profiles; on the other hand the slower ECMWF shows a cold frontal passage later Fri with onset of cooler NW flow more into Fri. Sided closer to NBM given the uncertainty with Chance PoPs initially, then trending lower (e.g. drier) for late in the day and evening. Highs in the lower to middle 60s and lows in the mid 40s. The Weekend: Despite the stated uncertainty in the middle to latter part of the workweek, most of the global models actually show some consistency in showing deep troughing on Saturday associated and a cool pocket of air aloft. This sets up a potential for unsettled (partly to mostly cloudy skies) but generally dry conditions at least for Saturday, with temps trending near to below-avg. It does look to be a brief shot of troughing aloft however, with pattern beginning to transition back towards ridging and drier weather for Sunday. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00z TAF Update: Tonight: High confidence. SCT-OVC VFR ceilings have already developed for most of the TAFs as of the 00z TAF issuance. However residual MVFR-IFR ceilings across SE MA and Cape Cod/Nantucket should trend to VFR thru 02z. Main focus will turn to increasingly gusty NW wind conditions for the second half of the evening/overnight. Expect NW gusts 20-25 kt developing around 03-05z western airports, and around 05-07z for the central and eastern airports, remaining gusty into Monday AM. Monday...High confidence. VFR with clear skies. Gusty winds out of the NW at 10-20 kts with gusts 30 to 35 kts. Monday night...High confidence. VFR. Northwest winds continue gusty in the evening, then diminish at night. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Tuesday through Friday/... Wednesday: VFR. Slight chance SHRA. Wednesday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Thursday: Mainly VFR, with local IFR possible. Chance SHRA. Thursday Night: Mainly VFR, with areas MVFR possible. Chance SHRA. Friday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA. Friday Night: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA. Saturday: VFR. Breezy. Slight chance SHRA. && .MARINE... Tonight... Rain tapers off this evening as surface low exits to the northeast. Winds shifting from the NW and increase to 20-25 kts with gusts up to 30 kts late. Seas 5-9 feet for the southern waters and build to 4-8 ft for eastern waters. Small Craft Advisory continues for most waters. Monday... Small Craft Advisory for all waters. Gusty NW winds with speeds to 30 kt, possibly the lower 30s. Seas 4-7 ft. Monday night... Small Craft Advisory continues. Gusty northwest winds in the evening with gusts to 25 kt, diminishing during the night. Seas 4 to 7 feet, especially on the outer waters. Outlook /Tuesday through Friday/... Wednesday through Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Thursday through Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. Friday Night through Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Slight chance of rain showers. && .FIRE WEATHER... Strong gusty northwest winds are expected across southern New England on Monday as high pressure nudges in from the west and with a deep low near Nova Scotia/New Brunswick. This will promote deep boundary layer mixing and dry relative humidities. Given this setup the forecast has gusts of 30-35 mph with minimum relative humidities of 20-35 percent during the afternoon. Observed rain amounts through 2 PM today... 0.50 to 0.60 inches in Srn RI and SE Mass, 0.25 to 0.50 in Nrn CT, Nrn RI, and parts of Ern Mass south of Boston, 0.25 inch or less across extreme northern CT and much of Western/Central/Northeast Mass. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 10 PM EDT Monday for ANZ232>235-237. Small Craft Advisory from 2 AM to 8 PM EDT Monday for ANZ230- 236. Small Craft Advisory from 2 AM Monday to 6 AM EDT Tuesday for ANZ231-251. Small Craft Advisory until 6 AM EDT Tuesday for ANZ250-254>256. && $$ SYNOPSIS...WTB/BL/Loconto NEAR TERM...WTB/BL/Loconto SHORT TERM...WTB LONG TERM...Loconto AVIATION...WTB/Loconto MARINE...WTB/Loconto FIRE WEATHER...
Area Forecast Discussion
National Weather Service Caribou ME
916 PM EDT Sun Apr 25 2021 .SYNOPSIS... Low pressure will exit across the Maritimes overnight through Monday. High pressure builds into the area Tuesday into Wednesday. Low pressure and a frontal boundary are expected to approach Wednesday night and clear the region Thursday afternoon. A frontal boundary is expected to move into the region on Friday. && .NEAR TERM /THROUGH MONDAY/... 9:16 PM Update: Low pressure is visible on satellite pictures in the Atlantic to the south of the Gulf of Maine. The low will pass east of Halifax by Monday morning with a trough extending back into eastern New Brunswick and northern Maine and into Quebec. The precipitation this evening has been more showery across the north with steadier light rain across Washington County. Overnight, a mid level low and pool of colder air aloft will begin to move in from the west and precipitation will transition to wet snow across the western Saint John Valley and North woods. As the cold air comes in from the southwest snow showers will become possible across the central highlands, although precipitation in this area is more likely to be showers and not a steady precipitation. Further to the east, precipitation should remain in the form of rain/showers overnight. Made some slight adjustments based on the current and expected conditions, but overall the changes were minor. Previous discussion: Scattered showers occurring attm across the northern and western areas in response to the warm front lifting n. Decent llvl convergence in place along the front and steep lapse rates leading to an area of enhanced activity across the northern border late this afternoon into the evening. The RAP soundings indicated some CAPE around 200 joules this afternoon, but best instability shifts ene by early evening. The latest run of the HRRR hints at some instability as does the NAMNEST, but cloud cover has kept a lid on any convective development. After further investigation into the RAP soundings, decided to include a small area across the northern border and nw areas for a tstm and gusty winds given the inverted V-sounding. Low pres will get organized off the southern New England coast and lift up toward the Gulf of Maine tonight. This low will become the primary low as the upper trof becomes negative tilt w/strong PVA coming around the base of the trof aiding in further development. Precip will become more stratiform in the form of rain later in the evening as that low lifts ne. Not expecting a heavy precip event as the best energy w/this system will remain to the east. Temps will start off mild tonight, but the trend of the guidance continues to show that a cooldown is expected overnight into early Monday morning across the western areas as colder air wraps in behind the sharpening upper trof. This will lead to temps dropping down to 0c or lower at 925mbs leading to the potential for rain to mix w/or changeover to snow. The areas to see this potential changeover to snow will be across the NW Woods down into Moosehead Lake region w/maybe around 0.5" of snow by 8 AM Monday morning. Further east, temps will stay warm enough for rain. Upper low closes off across northern New Brunswick on Monday w/cold air swinging further east, and rain mix w/or changing over to a period of snow. The areas to see the changeover will be across Northern Maine into the Maine Central Highlands. Further s, just some rain showers. Not expecting any significant snowfall accumulation w/the potential of around an inch or two across the higher terrain of Northern Maine the Maine Central Highlands. NW winds will be picking up during the day on Monday w/potential for some gusts to hit 30 to 35 mph, w/some sites such as GNR and FVE seeing gusts hitting 40+ mph. Daytime temps will be below normal. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... Vertically stacked closed low pressure over the Canadian Maritimes will slowly drift eastward Monday night into Tuesday. Blocking high pressure upstream with cause the slow movement. The result will be rain and snow showers in the northeast corner of the forecast area Monday night into early Tuesday morning with no more than an inch of snowfall in the high terrain of the North Woods. Most of the area will have lows in the mid to upper 30s under mostly cloudy skies and gusty NW winds. The clouds will move very slowly eastward on Tuesday such that NE Aroostook will stay in the clouds all day with highs only in the lower 50s, but Bangor will see sunshine and highs popping into the mid 60s. This raises some concerns about fire weather given the continuing gusty NW winds and low relative humidity. Weak high pressure builds Tuesday night with clearing spreading across the area and lows mostly in the mid to upper 30s. The high pressure system appears to stay in place most of the day on Wednesday with increasing clouds and chances of showers increasing late day. Highs will move up towards the low to mid 60s for the whole area and this will probably be the warmest day of the week. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... The period continues to be unsettled and generally mild with a lot of uncertainty in the exact timing and details. There is a decent shot for a few days of beneficial rainfall. Using a blend of models, PoPs remained at the chance level or higher most of the period until Sunday. Thursday has the best shot at being dry and Thursday night to Friday night are most likely to be the wettest. The basic scenario involves a rich flow of deep moisture in the southern stream from a cut off low in the southwestern states, a building upper ridge along the southeastern US coast, a series of weak shortwaves in the northern stream and the block in the Atlantic. A warm front will try to push warmer and more humid air into the area, but the details on its arrival vary from Wednesday night per the GFS to Thursday night for other models. That depends on the strength of the upper level ridging in the SE US and how fast the cut off low moves out of the Maritimes. Guidance generally agrees on low pressure crossing the area later Friday, followed by a northwesterly flow and scattered showers for Saturday and Saturday night. High pressure builds by Sunday. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... NEAR TERM: As of 9 pm, MVFR at KBHB and VFR at the terminals from KBGR north to KFVE. Expect conditions to lower to MVFR at all of the terminals tonight with IFR likely by daybreak Monday at the Aroostook County terminals in rain. The rain could mix with, or change to snow by Monday morning across KFVE and then KCAR/KPQI by late morning. Wind variable, but mostly E-SE 5 to 10 knots late this evening, becoming NNW 10 to 15 kts with gusts up to 20 kt late at night into Monday morning. For Monday, IFR north becoming MVFR by late morning for all terminals and then VFR by the early afternoon for KBGR and KBHB. MVFR holding across the northern terminals through the remainder of the afternoon. NW winds 15-20 kt w/gusts 30 kt w/KFVE seeing 35+ kts during the afternoon. SHORT TERM: Monday night into Tuesday morning...MVFR tempo IFR in snow showers north of GNR and HUL. Otherwise VFR. NW winds gusting to 30kt. Tuesday afternoon through Wednesday evening...VFR with light winds. Wednesday night into Friday....MVFR tempo IFR due to rain and low cigs. Light winds. && .MARINE... NEAR TERM: Winds/seas will remain below small craft advisory levels through tonight. SSE winds 10-15 kt becoming NNW 15-20 kt by early Mon morning w/gusts to 25 kt. Seas building to 4-6 ft. Vsbys will lower in rain tonight. Mon...NW winds 15-20 kt w/gusts 25-30 kts. The highest gusts will be across the outer zones. Seas 5-7 ft. Rain transitioning to showers. SHORT TERM: SCA conditions continue into Tuesday morning and the next weather event is the threat of fog Thursday and Thursday night. A weak SCA for the outer waters is possible Friday night. && .TIDES/COASTAL FLOODING... Higher astronomical tides through early week. There is storm surge expected late tonight, but the high tide is expected near 1015 PM. As a result, coastal flooding is not likely. Tuesday night around midnight is a much higher astronomical tide, but no storm surge expected. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory from 5 AM Monday to 10 AM EDT Tuesday for ANZ050>052. && $$ Near Term...CB/Hewitt Short Term...MCW Long Term...MCW Aviation...CB/Hewitt/MCW Marine...CB/Hewitt/MCW Tides/Coastal Flooding...MCW/CB
National Weather Service Sioux Falls SD
1031 PM CDT Sun Apr 25 2021 .SHORT TERM...(This Evening through Monday) Issued at 231 PM CDT Sun Apr 25 2021 Forecast Highlights: 1. A few showers and isolated storms into Monday morning. 2. Near record highs possible on Monday, with some fire danger. 3. Potential for isolated strong storms Tuesday morning. 4. Cooler mid-week followed by strong warmup by May 1. Today: Warm front just beginning to enter the southern CWA at mid- afternoon. Temperatures south of the boundary are mixing well into the 70s, with temperatures on the cooler side of the boundary still climbing into the 60s. Further northeast, stratus is slowly retreating away from the area, but highs may fail to reach the mid 40s until the very end of the day in Southwest Minnesota. Tonight: The surface warm front will continue to slowly edge northward through the night. Continued low-lvl mixing should prevent any large scale fall in temperatures tonight, and will hold overnight lows in the upper 40s to lower 50s. Short term guidance continues to show enhancement of the low level jet after dark tonight, in response to a series of shortwaves crossing the Central Rockies. Increasing low-lvl convergence across portions of central South Dakota into the northeastern third of the state should lead to the development of showers late this evening and overnight. MUCAPE values do climb into the 100-400 J/KG range, but remain very tall and thin the sounding profile. So would anticipate a bit of isolated thunder, but no severe weather. Stratus may try to build southward late tonight, as boundary layer moisture begins to increase. A lot of uncertainty in this development, which could slow the rise in temperatures a bit Monday morning. Monday: Surface low pressure developing in the Nebraska Panhandle should begin to slide east and then north through the day. Strong warm advection with 850 mb temperatures pushing into the lower 20s across northern Nebraska should result in temperatures approaching the top 10 percent of warmest days on record for the 26th. Have generally followed the better mixing shown by the HRRR and RAP, given dry ground conditions and dry low level temperature profile. This combination could lead to falling dewpoints, especially across the MO river valley where RAP/HRRR guidance mix dew points towards the lower 20s to teens. Winds are a bit more uncertain as the stronger surface flow should result across portions of Iowa and Minnesota in the afternoon as the surface low edges into south central South Dakota. The mismatch in winds and lowest RH may preclude any fire weather headlines at this time, but these trends will need to be monitored. .LONG TERM...(Monday Night through Sunday) Issued at 231 PM CDT Sun Apr 25 2021 Monday Night: A cold front will begin to sink southward Monday evening and stall across northwest Iowa by Tuesday morning. Soundings indicate that SFC based convection should be capped along the advancing boundary. However, HREF MUCAPE values approaching 1500 J/KG are projected to advance north of the boundary by midnight. Increasing dPVA and 850 frontogenesis may be enough to develop scattered convection towards the 3am Tuesday hour with this convection continuing into mid-morning Tuesday. Given reasonable speed shear in the effective column, can`t argue with the potential for an isolated stronger hailer Tuesday morning. This is also hinted at in HREF probabilities, and I wouldn`t be surprised to see convective outlook risks increased. Tuesday: Shower and isolated thunderstorm chances may continue through the day on Tuesday. Depending on the positioning of the frontal boundary, areas of Northwest Iowa could see highs climb towards the lower 70s. Further northwest, highs will be much cooler towards the 50s. Wednesday: Shower chances may hold on into Wednesday as mid-lvl troughing will be slow to slide east of the region. Temperatures will remain below normal through Wednesday with a generally north wind. Thursday-Friday: Temperatures will begin to warm up nicely through the end of the week as mid-lvl heights begin to rise and winds turn back southerly. Highs in the 60s are likely Thursday with highs rising into the 70s on Friday. Saturday-Sunday: Strong southwesterly flow aloft arrives for the weekend and this puts the region in a good position to see well above normal temperatures to start the weekend. Gusty southwest winds should push highs well into the 80s Saturday with some uncertainty on passing showers and temperatures a shade cooler by Sunday. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 1028 PM CDT Sun Apr 25 2021 A somewhat low confidence forecast for late tonight into Monday morning in regard to the potential for MVFR and IFR ceilings. Currently the higher resolution models indicating very little lower stratus while the Nam and GFS are much more widespread. Will lean a little more heavily on the high resolution models and keep the stratus in check a little more. Would think that the better chance would be along and north of roughly I-90 which is also along and north of the surface warm front. Tough call with decou;ling winds washing out this front a bit as well. Otherwise any lower ceilings that do develop should lift north pretty quickly in the morning. Scattered showers and an isolated lightnring strike will also be possible overnight with the better chances north of I-90. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...Dux LONG TERM...Dux AVIATION...08
Area Forecast Discussion
National Weather Service Louisville KY
1025 PM EDT Sun Apr 25 2021 .Forecast Update... Issued at 1025 PM EDT Sun Apr 25 2021 Current temps across the region are sitting in the low-mid 50s, with dewpoints in the 40s and calm winds. 00z sfc analysis reveals a 1023mb high located over the Great Lakes and building into our region. This will lead to a clear and cool night with ridge/valley splits and potential fog development. Hi-res guidance has backed off a bit through this evening on fog development for the overnight, but still question the overall extent of it. Believe we`ll see at least patchy fog within the river valleys, but could expand a bit more beyond the valleys in the Bluegrass region. While crossover method indicates the best region to see locally dense fog would be LEX and surrounding areas, one inhibiting factor that could limit overall extent of fog will be soil temps. With 4" soil temps around 9F warmer than the crossover temp, that would suggest more of a scenario with patchy fog with variable visibilities instead of an expansive dense fog scenario. All fog potential is east of I-65 and should only last for a few hours during the pre-dawn Monday hours. Have slightly increased coverage of fog in wx grids, as well as updated the near term grids with latest obs/trends. Updated products coming shortly. && .Short Term...(This evening through Monday) Issued at 225 PM EDT Sun Apr 25 2021 In the near term, clouds will continue to clear out across the CWA this afternoon as a weak cold front pushes southeastward. Satellite imagery shows most locations partly to mostly sunny with the exception of the Bluegrass where low stratus continues to hold. Thanks to the cloud cover, the KY Mesonet shows a nice gradient of temperatures from the west-southwest where temperatures are in the low 60s to the east-northeast where temperatures are in the low/mid 50s thanks to lingering cloudcover. Clouds will clear out overnight as a sfc high continues to build in over the eastern and southeastern US tonight into tomorrow. Winds will become light to calm overnight allowing for good radiational cooling. Once again, areas of patchy fog could form tomorrow morning, especially east of I-65 and along south of the parkways. The best chance of fog is likely across the Bluegrass where clouds were slowest to clear this afernoon and max heating wasn`t reached. Lows will be mostly in the low/mid 40s with some upper 30s across our eastern counties. Upper level ridging will continue to increase heights over the area tomorrow with the axis of the ridging being over the Ohio Valley by tomorrow afternoon. With a 1020mb sfc high off to our east, we will have a good return flow allowing temperatures to warm into the upper 70s with some isolated 80s possible. .Long Term...(Monday night through Sunday) Issued at 228 PM EDT Sun Apr 25 2021 Monday Night through Tuesday Night... Notable upper ridging takes hold over the eastern CONUS through the early to mid week time frame. Meanwhile, steady S/SW surface flow will also develop thanks to the pressure gradient between low pressure over the high Plains, and high pressure centered off the mid Atlantic Coast. Ultimately, this setup will lead to a temperature surge as values reach well above normal by Tuesday afternoon. Soundings show good vertical mixing up into H85 temps around 15C in addition to the steady warm advection at the surface and good solar insolation. All indications are to go on the high side of guidance with those factors in mind. As a result, will look for low to mid 80s just about everywhere. Think we`ll fall short of records that range in the upper 80s to touching 90 degrees for that day, but a good 10 to 12 degrees above normal seems like a safe bet. Also worth noting that Tuesday night lows will be quite mild in the low to mid 60s given steady southerly flow and increasing upper sky cover. Wednesday through Thursday Night... The upper ridge axis will be pushed off the SE CONUS by mid week as a northern stream shortwave moves from the northern Plains into the Great Lakes, and a cutoff low hangs up over the SW CONUS. A baroclinic zone is expected to set up from the Rio Grande River Valley up through our region and into New England between the western trough/cutoff lows and the eastern upper ridge axis through mid week. Expect Wednesday will still be mostly dry and warm with precipitation chances starting to creep in from the NW later in the day. Better chances arrive later Wednesday into Thursday as the upper features mentioned above push eastward and drag the front through our area. Highest pops look to be Thursday, along with some thunderstorm chances. At this point there doesn`t appear to be a whole lot of instability and that is current limiting factor to any severe potential. However, soundings do take on a more tall/skinny profile to the point where some heavier rainfall rates may be possible. Some training may also occur as flow will be nearly parallel to the slow moving boundary for a while. PWATs also appear to peak around 1.5" through the column through mid week. Right now, the heaviest axis of rain looks NW of our CWA, but will be something to watch as over 1" of rain is currently forecast for areas along and west of I-65. Friday - Sunday... By late week, the northern stream shortwave will be the driving factor in pushing the cold front through our area. Meanwhile, the aforementioned cutoff low will slowly meander eastward across TX. We`ll see a dry NW flow aloft and surface high pressure pattern over the Ohio River Valley into the weekend which will bring a return to dry conditions. Highs in the low 70s on Friday are expected to gradually warm to the upper 70s by Sunday. && .Aviation...(00Z TAF Issuance) Issued at 720 PM EDT Sun Apr 25 2021 IMPACTS: Potential fog development overnight for LEX/BWG. DISCUSSION: Latest sfc analysis continues to place a weak stationary/cold frontal feature along and parallel to the Ohio River this evening. VFR conditions across the region at this time will continue for most through the forecast period. Still believe the weak cold front will sag south overnight, leaving a clear sky zone in its wake. RAP model soundings suggest that radiative cooling will be sufficient enough to develop a low level inversion strong enough to prevent turbulent mixing. Additionally, using the crossover method, the highest potential for fog appears to be at LEX, but could also see some patchy BR at BWG as well. Will keep BWG at low- end VFR, but will bring LEX down to MVFR for a few hours for Monday morning. Winds are already pretty light across the region, and expect these calm conditions to continue thanks to a sfc high located to our north and helping with the development of overnight fog. Other than the fog chances VFR ceilings will remain the rest of the forecast with winds turning out of the south tomorrow. CONFIDENCE: Medium on visibility/fog for LEX/BWG. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...CJP Short Term...BTN Long Term...BJS Aviation...CJP
Area Forecast Discussion
National Weather Service San Francisco Bay Area
848 PM PDT Sun Apr 25 2021 .SYNOPSIS...Isolated light showers will continue from about San Jose southward through the remainder of the evening. Otherwise, expect clearing overnight from north to south, with cool temperatures and patchy late night fog. Continued cool, but dry conditions are forecast for Monday. A warming trend begins on Tuesday, with above normal temperatures expected in most areas from Wednesday through Friday. Cooling is forecast for next weekend. && .DISCUSSION...As of 8:45 PM PDT Sunday...A cold front that brought showers to much of our forecast area today continues to weaken as it pushes south through the southern Santa Clara Valley and Monterey Bay Area. Rain totals today were highest in the North Bay where some locations in the coastal hills picked up about a half inch. Otherwise, rain totals were generally less than a quarter inch, with most urban areas accumulating less than a tenth of an inch. Isolated light showers will continue across the southern portion of our forecast area through the remainder of the evening, otherwise expect clearing from north to south overnight. The airmass behind the front is quite chilly with the 00Z OAK sounding reporting an 850 mb temp of 1.4 deg C, and models indicate further cooling to about 0 deg C overnight. Thus, we could see some upper 30s for lows in some of our cooler inland valleys by daybreak Monday, especially in the North Bay Valleys. Also, patchy fog is possible in the valleys late tonight and early on Monday, most likely in the North Bay. Mostly sunny skies are forecast for Monday as the weather system moves well off to our southeast. However, some clouds will likely develop in the afternoon, especially over the hills, as a shortwave trough drops in from the northwest and maintains unstable conditions. Models develop isolated afternoon showers tomorrow, mainly to the north and east of our area. However, the latest HRRR develops a few showers over the hills of Napa and eastern Sonoma County in the late afternoon, and the 00Z NAM develops isolated late afternoon showers along far eastern Santa Clara County as well as the southeastern portions of San Benito and Monterey Counties. Thus a few showers over our inland hills late tomorrow afternoon can`t be ruled out. But for most of our area, expect dry conditions tomorrow. The shortwave trough will bring a reinforcing shot of cool air into our area and so temperatures will remain cooler than normal. However, with more sun tomorrow, afternoon highs should be close to what they were today, or a few degrees warmer in some locations. From Previous Discussion...Tuesday we`ll see the start of a warming trend as the trough digs deeper into the Inter-mountain west and a ridge builds off the Pacific Coast. This will result in closer to normal temps - mid to upper 60s around the Bay, and low to mid 70s inland. Wednesday the ridge shifts over the west coast, bringing some light offshore flow and above normal temps - more widespread 70s and some low 80s. Further warming will occur inland Thursday as the ridge strengthens. Warmest spots will see upper 80s and perhaps 90, which is pretty similar to our last heat event. Temps near the coast will remain seasonably warm, so there will not be much concern in terms of heat impacts. Friday will be the final day of this heat stretch, before weak troughing cools the area back to near normal over the weekend. && .AVIATION...As of 5:22 PM PDT Sunday.....For the 00Z TAFs. It`s VFR-MVFR with showers over the South Bay, the East Bay and north Central Coast. MVFR ceilings tonight and Monday morning. Low level moisture resulting in patchy fog overnight, especially across the North Bay. Vicinity of KSFO...VFR, west wind 10 to 15 knots diminishing to 5 to 10 knots tonight. MVFR ceiling tonight and Monday morning until 16z then VFR through Monday afternoon and evening. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR, southwest to northwest winds at 10 knots diminishing to light and variable tonight and Monday morning. MVFR ceilings tonight and Monday morning then VFR Monday afternoon and evening. && of 5:08 PM PDT Sunday...A weak front continues to move through the waters this afternoon bringing light to moderate showers. Winds will shift out of the west to northwest behind the front from north to south the rest of today with northwest winds expected to prevail by tonight. Brief locally breezy conditions possible along the boundary as it passes by. Winds will increase tomorrow afternoon and evening particularly along the inner coastal waters north of Point Reyes, between Pigeon Point and Point Pinos, and south of Point Sur. Mixed seas to persist with a shorter period northwest swell and a longer period southerly swell. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...NONE. && $$ PUBLIC FORECAST: Dykema/Lorber AVIATION: Canepa MARINE: AS Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Pocatello ID
910 PM MDT Sun Apr 25 2021 .UPDATE...Quick update this evening to adjust PoP and QPF for ongoing precipitation event across East Idaho. Tweaks were slight. Region is in a relative break with bulk of the rainfall occurring in the southeast highlands overnight as upper low continues to sag southeast through Oregon/northern California. DMH && .PREV DISCUSSION... /issued 144 PM MDT Sun Apr 25 2021/ SHORT TERM...Tonight through Tue night. A closed low is making its way on shore tonight and by Mon afternoon should be centered in northern Nevada. This puts eastern Idaho in a consistent period of moist southwesterly flow that is pumping quite a bit of precipitation into portions of the forecast area, mainly the souther tier along the UT-ID border, including the Badger wildfire incident area, and the eastern highlands along the WY-ID border. Closed lows move slowly, and the precipitation is heaviest Mon with a tapering off of precipitation production for Mon night--but no real end in eastern Idaho until the extended forecast period below. By Mon, cold air will have moved in and threatens to produce snow even in the higher elevations of the Snake River plain. There is a lot of freeze-thaw, with even Stanley in the central Idaho mountains getting into the 40s for at least some partial melting. It is difficult to say how much will stick during the period starting tonight and ending Tuesday morning, but nearly 6 inches should fall over Galena Summit between Stanley and Ketchum, 2 inches for Monida pass on Interstate 15, and around an inch for Pine Creek Pass into Wyoming. Raynolds Pass should be the standout for U S Route 20 with nearly 9 inches falling during that same time. Instability of the atmosphere is going up and there is a threat of thunderstorms for Mon afternoon over the entire forecast area and Tue afternoon over the eastern half. Do not expect severity issues with less upper level support compared to yesterday (Sat) and extensive cloud cover suppressing surface heating. Out flow could still approach 45 to 50 mph. Wind is expected to be in the breezy range with a wind shift Mon night from south and west to the northwest. Do not expect Lake Wind Advisory conditions at this time, although thunderstorms may produce poor boating conditions. Messick LONG TERM...WEDNESDAY THROUGH NEXT SUNDAY... Not thrilled with the cool, wet, dreary wx in the short-term portion of the forecast? Allow us to spread some spring cheer! All long- range models and model ensemble clusters support a solid ridge of high pressure building across the Great Basin/nrn Rockies for Wed/Thurs/Fri with high forecast confidence, supporting mostly clear/sunny skies and a warming trend with highs in the upper 50s/ upper 60s Wed surging into mid 70s/mid 80s by Fri. That`s 15-20 degrees above climatological normals for late April, putting record high temps in jeopardy at all of our climate sites Fri. Sure enough, ECMWF EFI (Extreme Forecast Index) values are topping out at 0.6-0.7 for MaxT, suggesting that an unusually warm event is likely compared to the model climate period. That said, a comparison of our NBM-led forecast to GFS/EC ensemble meteograms for MaxT suggest we`re right where we should be with strong ensemble clustering 4 degrees either side of our current forecast, so we didn`t make any nudges. On the fire wx front, the warming trend will be accompanied by a drying trend in afternoon MinRH values (potentially as low as 14-20% by Thurs/Fri) along with diurnally breezy conditions, but depending on how fuels respond to the current/ongoing wet period, we MAY be a little more definitively entering our spring "green-up" by that time which MIGHT take the edge off the early start to fire season we have been dealing with this year. Still, something to be mindful of. Next weekend, all 500mb height ensemble clusters support the ridge breaking down to some degree, and a possible shortwave trough moving across the nrn Rockies. EOF patterns suggest the current greatest source of forecast uncertainty is how strong/amplified the trough will be (which is reflected by a variety of solutions in the deterministic models), with a secondary source of uncertainty tied to exact timing of the trough. The 500mb height clusters reflect a range in potential amplification as well, but they all currently keep the trough axis west of our CWA Sat. SO, while an introduction of clouds/potential precip ahead of the trough may take the edge off of high temps, the generally warm pattern should continue. Unsurprisingly, the clusters with a stronger/more amplified trough yield solutions that are wetter than the mean, and given the heat and overall synoptic picture, t-storms would be possible. Sun, high temps and t-storm potential both revolve around timing of the trough axis/associated cold front, with cluster analysis offering roughly a 50/50 chance of our SE Idaho CWA spending most of the day on the warmer pre-frontal side vs. the cooler post-frontal side of this system, so stay tuned. All things considered, the NBM did a great job of capturing all of these themes and trends, and very few edits were made. - KSmith AVIATION...Cool, dreary, moist, showery wx is the order of the day across SE Idaho as a trough of low pressure continues to slowly push east into the nrn Rockies, and while we may see a SLIGHT overall lull in shower activity and a SLIGHT cig improvement this afternoon for most terminals, clouds will hold on at close to the VFR/MVFR threshold for most locales. Instability (fuel) should remain too low for t- storms. This eve, all model guidance supports a SW to NE oriented swath of more organized precip returning for KBYI/KPIH/KIDA/KDIJ, starting as early as 01z/7pm at KBYI and 03-04z/9-10pm elsewhere (albeit with some timing differences between the high-res guidance sources). This should be followed in short order by cigs trending into MVFR territory and staying there for the rest of the TAF period...while confidence on start-time of this next round is a bit low because of the model differences, timing confidence on the 06- 08z "cig crash" FM groups for KPIH/KIDA/KDIJ in the 18z TAF package are a bit more solid. HRRR guidance wants to go even lower into IFR territory, but held closer to the MOS consensus for now and just used the HRRR for timing...will see how things trend as NAM time- heights somewhat follow the HRRR idea. Didn`t get too aggressive with dropping vsbys for most sites as temps/dew points should be just warm enough to support rain, but`s going to be CLOSE at KDIJ. If precip manages to switch to snow tonight, expect vsbys to crash to 1-2 SM, which is not currently reflected in the TAF. Meanwhile, KSUN may pull off quieter, VFR conditions tonight and Mon AM. Mon afternoon/eve, the heart of the low pressure system responsible for this wx rides the nrn NV border, with continued unsettled and showery conditions expected (potentially into at least Tue AM). A few t-storms will be possible Mon afternoon. - KSmith && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$