Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/25/19

Area Forecast Discussion
National Weather Service Buffalo NY
1010 PM EST Tue Dec 24 2019 .SYNOPSIS... High pressure across Quebec will ridge into our region and provide dry weather through Thursday. The next chance for any precipitation will arrive Thursday night into Friday with increasing chances of rain, possibly a mixture of rain and snow across the North Country. && .NEAR TERM /THROUGH WEDNESDAY/... high pressure will continue to ridge into the region overnight which will maintain dry weather and through Christmas Day. The main weather concern for tonight is the potential for fog to move into far western New York late tonight and into Wednesday morning. This fog and stratus can easily be seen on Nighttime microphysics satellite imagery, and is located across eastern Ohio and central Lake Erie. Light easterly surface winds will keep this to our west for most of the night, but as the high moves further away surface winds will become SSW. This flow will move the stratus and fog very close to the far western New York and the Niagara Frontier. Following the HRRR and other mesoscale guidance, expect that this fog to remain north and west of downtown Buffalo, probably just clipping Niagara County and Grand Island. If this happens, it would be roughly between 6 a.m. and noon on Christmas day. There is a potential for locally dense fog and possibly freezing fog, but confidence is not high enough to issue any headlines. Otherwise, a marginally strong sw low-level jet H925-H8 up to 30 kts closer to the warm front will keep temps mainly steady in the upper 20s to lower 40s across western NY. It will be a bit colder closer to the surface high toward Finger Lakes and the North Country where overnight lows will range from the teens to upper 20s. There will be renewed warm air advection Wednesday afternoon with the passage of a weak warm front and as upper heights start to build. This will lead to well above normal temperatures for Christmas Day. Projected inbound thermal profile and mixing potential translating into temperatures warming into the upper 40s and lower 50s from the western Finger Lakes and Genesee Valley westward with around 40 degrees across the North Country. Favor an optimistic cloud forecast with dry conditions and mostly sunny skies by the afternoon. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... A weak shortwave along with the northward pushing front will bring in a bit more moisture Wednesday night, but with little forcing expect only an increase in cloud across the area. A period of deeper southwesterly flow will exist across the area Thursday and Thursday night as the upper ridge axis eases eastward and greater height falls commence upstream. A greater northward transport of moisture will emerge during this time. This noted increase in moisture quality may support the development of a few light rain showers starting late Thursday afternoon or Thursday evening as a lead surface trough and trailing cold front transit the region. The underlying forcing remains weak, so simply a low end potential and of limited coverage/duration. Thursday again should feature above average warmth with highs ranging from the upper 30s across the North Country to the mid and upper 40s across far western New York. Moisture quality continues to improve Thursday night with additional chances for showers, although thermal profiles suggesting it will likely be cold enough to support some light snow showers or even some freezing rain across portions of the North Country. On Friday any risk for any freezing rain across the North Country will end early as warmer air floods northeastward following the passage of the warm front. At the same time sharply diminishing lift and moisture in the wake of the warm front should result in greatly reduced precip chances for the remainder of the day, with a trailing cool front looking to be far too weak and moisture starved to produce much more than some scattered light showers as it traverses our area during the afternoon. By Friday evening the trailing cool front should be largely to our east. Increasing ridging and drying in its wake will bring an end to any lingering light showers across the North Country, while supplying dry and quiet weather to the remainder of the area. && .LONG TERM /SATURDAY THROUGH TUESDAY/... An amplified upper air pattern will be present this long term period, with the Great Lakes region starting the period under an amplified ridge, and fair weather. Under a deep trough over the Plains, a storm system will deepen, driving a warm front through the Great Lakes region Saturday night. On the eastern fringes of this warm front a few rain showers may sneak into WNY late Saturday night. Sunday our region will be within the warm sector of this storm system, with a mild southerly flow bringing low to mid 50s across WNY, and upper 40s east of Lake Ontario. As the storm system nears us from the Plains there will be an increasing threat of mainly rain showers Sunday. The models are still somewhat in disagreement with the passage of this system`s cold front...and leaned upon the slower ECMWF within this amplified pattern...bringing the cold front across our region Monday with additional rain showers. The cold air will deepen behind this front to allow a change over to rain/snow through the day Monday, with cold air sufficiently deep enough by Monday night to support lake effect snow bands falling to the east of the Lakes through the end of the forecast period. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... No issue for aviation operations with VFR expected through 09Z. The main concern is the risk for areas of dense fog to clip the area. By a narrow margin, this is likely to reach KIAG around 11Z, but most guidance keeps it `just` to the west of KBUF. This bears close attention since areas of fog upstream have lowered visibility to a quarter mile at many locations. Any fog will likely dissipate by 15Z or so, with associated stratus possible through 18Z. Otherwise, expect VFR flight conditions through 00Z Thursday. Outlook... Wednesday night...Patchy fog with local IFR conditions. Thursday...Mainly VFR. Thursday night Through Friday...Some restrictions possible in rain showers. Saturday...Mainly VFR. Sunday...MVFR with showers. && .MARINE... High pressure centered over Quebec will keep winds and waves below small craft advisory criteria through at least Thursday. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...AR/Apffel NEAR TERM...AR/Apffel SHORT TERM...JJR/TMA LONG TERM...Thomas AVIATION...AR/Apffel MARINE...AR/Apffel/JLA
Area Forecast Discussion
National Weather Service State College PA
1007 PM EST Tue Dec 24 2019 .SYNOPSIS... An anomalous upper level ridge will continue to bring a lack of cloud cover and mild temperatures to the region for the next couple days. A weak cold front is likely to pass through the area early Friday, then a stronger cold front will sweep through the state Sunday night or Monday bringing widespread rain. && .NEAR TERM /UNTIL 8 AM WEDNESDAY MORNING/... Large patch of fog and low clouds continues to slink back toward the area from wrn PA. HRRR and RAP progs continue the thought of only allowing the clouds/fog to get into Warren County. The clear skies have already allowed temps to drop to 22F at THV, 25F at SEG, and 25F at HMZ. These numbers should level off soon, though, as they near the dewpoints. Fog is possible as well, mainly in the southern valleys. "That wonderful nose of yours will cut through the murkiest storm they can dish up." -Santa && .SHORT TERM /8 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... High pressure brings quiet weather for Christmas Day with full sunshine and temperatures above average yet again. Perhaps some increase in high clouds tomorrow night with mild temperatures. && .LONG TERM /THURSDAY THROUGH TUESDAY/... A warm front lifting into the region from the Ohio Valley could produce a bit of light rain/drizzle across the northern mountains late Thursday into early Friday. Deeper moisture and more significant large scale forcing ahead of mid level shortwave are progged to pass well north of the forecast area. Over central Pa, model soundings shows a relatively shallow layer of moisture and southerly flow, favoring the best chance of measurable rain over the northern mountains, where orographic forcing will be greatest. The bulk of medium range guidance indicates a more potent cold front will sweep through the area Sunday night or early Monday. Strong forcing and a plume of Gulf of Mexico moisture is progged to accompany the fropa and latest GEFS projects rainfall of between 0.5 and 1 inch. Have therefore ramped POPs upward into the likely category Sunday into Monday AM. Also expect breezy conditions behind the cold front Monday and Tuesday. Both the 00Z NAEFS and ECENS indicate a return to drier conditions and more seasonable temperatures early next week, as upper trough swings over the state. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... An area of dense fog west of the Laurel mountains all day today is inching closer to the forecast area. This increase in low level moisture may affect KJST and KAOO overnight. Otherwise, good VFR conditions will continue through Christmas Day. .Outlook... Thu-Fri...Low cigs and isold --shra possible N Mtns late in period. Sat... No sig wx expected. Sun... Low cigs and rain, poss LLWS && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Ross NEAR TERM...Ross/Dangelo SHORT TERM...Ross LONG TERM...Fitzgerald/Colbert AVIATION...Tyburski
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
742 PM PST Tue Dec 24 2019 .SYNOPSIS...24/301 PM. Precipitation will develop along the Central Coast overnight then spread across the region by early afternoon. The heaviest rain and snow will fall late Wednesday night into early Thursday with gusty easterly winds. Conditions will clear on Friday and temperatures will be near normal by the weekend. && .SHORT TERM (TUE-FRI)...24/740 PM. ***UPDATE*** It was a pleasant day today with a sunny start and a mostly cloudy finish. Hgts were only 552 DM today and as a result max temps across the coasts and vlys only reached the upper 50s or lower 60s All eyes on Christmas as a large cold upper low will roll into and through Srn Ca. Unfortunately this storm has been a very difficult to predict and the latest thinking is different from even just 12 hours ago. The upper low is now forecast to develop a little more to the west of the state and then start its eastward swing a little later. This has resulted in delay of the onset of the main rain band. Cannot rule out a few stray showers overnight but if there are any they should be pretty inconsequential. In the morning a trof ahead of the main system will roll through the Central Coast and will bring light rain to the area nothing more than a quarter inch though. This trof will dissipate as it rolls into VTA and LA counties. There will likely be some stray showers but nothing much. Both the HRRR and the NAM agree that the main rain band will move into SLO and SBA counties early tomorrow evening...into VTA county mid or late evening and then into LA county before dawn. Will have to wait for the GFS run but beginning to think that there is a chance that this storm may not quite live up to its billing esp with respect to snow. But not ready to give up yet as the NAM has not been the mdl of choice over the past few days. Will issue update soon to slow arrival of rainfall. ***From Previous Discussion*** The much more impactful part of this storm will come Wednesday night into Thursday as the upper low tracks south just west of the coastline and south to southeast flow increases below 850mb. The strong orthogonal flow across the Transverse mountains and synoptic forcing from the frontal boundary will generate periods of very heavy rain, mostly south of Pt Conception during this period. There is a little bit of instability over the coastal waters but because the low is expected to stay offshore most of the convective potential will remain there as well. However, even without thunderstorms the upslope enhanced rain rates will peak at around .75"/hr which is right at the very low end of where we could see some minor debris flows near the recent burn areas. Should the low track a little farther east and bring more of that convective potential into the mainland areas that could be enough to push this into a flash flood watch situation (especially LA/Ventura Counties) and will see how the pattern evolves over the next 24 hours. Rain amounts from earlier forecasts still look good, generally 1-2" coast/valleys 2-4" mountains, and again 90% of that falling Wednesday night into Thursday morning. The biggest impact from this system is likely to be the snow and very low snow levels impacting some major roads and communities, including the Antelope Valley Thursday. The pattern is looking very similar to what we saw over Thanksgiving with strong northeast wrap around flow developing Thursday morning across our interior (including the Cuyama and Antelope Valleys). Given the good consistency in the models the last couple days decided confidence was high enough to go with a Winter Storm Watch for the AV with up to 8" of snow possible (especially in the foothills). Not as much in the Cuyama Valley but enough for a Winter Weather Advisory. Higher elevations of the mountains in LA/Ventura Counties could see up to 2 feet of snow. The strong northeast flow Thursday will result in gusty winds across much of the area, possibly advisory level in the LA/Ventura coast/valleys. Precip will taper off Thursday afternoon and night, lingering longest across the eastern portion of the AV and San Gabriel Mountains. Dry weather expected Friday but still breezy and cool. .LONG TERM (SAT-TUE)...24/123 PM. Much quieter period of weather this weekend into early next week. Dry and warmer over the weekend as a brief ridge builds. That will break down Sunday as another trough approaches. However, recent model solutions have shifted this trough farther east making it more of an inside slider pattern which significantly cuts down on the available moisture. All the GFS ensemble members have removed rain from their forecasts but a few EC ensembles still show a little precip so will keep some low pops going Sunday night into Monday but the trends are definitely drier. Models differ quite a bit after that in terms of where that upper low will go but all solutions still pointing to a dry forecast Tue/Wed for New Years eve and day. && .AVIATION...25/0128Z. At 0045Z at KLAX, There was no marine layer nor any inversion. Good confidence in TAFs through 14Z. Then less confidence due to timing of the onset of rain and lower cigs associated with the rain. Light showers with VFR cigs are possible at every site but KPMD AND KWJF aft 14Z with increasing chcs of shower activity and MVFR cigs aft 20Z. KLAX...Good confidence in TAF through 14Z. Then less confidence due to timing of the onset of rain and lower cigs associated with the rain. Light showers with VFR cigs are possible aft 14Z with increasing chcs of shower activity and MVFR cigs aft 20Z. Good confidence in no east wind component through 02Z there is a good likelyhood of 8 kt or more of an east wind component after 06Z on the 26th. KBUR...Good confidence in TAF through 14Z. Then less confidence due to timing of the onset of rain and lower cigs associated with the rain. Light showers with VFR cigs are possible aft 14Z with increasing chcs of shower activity and MVFR cigs aft 20Z. && .MARINE...24/156 PM. For the Outer Waters, moderate confidence in the current forecast. Hi confidence in Small Craft Advisory (SCA) level winds across the southern zone (PZZ676) through this evening. Otherwise, winds and seas should remain below SCA levels tonight and Wednesday. For Wednesday night, moderate confidence in strong SCA level southeast winds with hazardous seas, and north to northeast winds to SCA levels Thursday into Thursday evening. SCA level seas can be expected into Friday, then high confidence in winds and seas dropping below SCA levels for Friday night and Saturday. There is then a 50% chance of SCA level winds for Sunday. For the Inner Waters north of Point Sal, moderate to high confidence in the current forecast. Through Wednesday, high confidence in winds and seas remaining below SCA levels. For Wednesday night through Thursday morning, moderate confidence in SCA level southeast to northeast winds and hazardous seas. SCA seas should linger Thursday night then winds and seas should remain below SCA levels Friday through Saturday. There is then a 50% chance of SCA level winds for Sunday. For the Inner Waters south of Point Conception, moderate confidence in the current forecast. There is a 30% chance of SCA level northwest winds through this evening, otherwise winds and seas are expected to remain below SCA levels through Wednesday. For Wednesday night, moderate confidence in SCA level southeast winds, then turning east to northeast Thursday and Thursday night. Northeast wind will continue Friday with a 30% chance of SCA level gusts Friday morning. For Friday afternoon through Sunday, generally high confidence in winds and seas remaining below SCA levels, except for a 50% chance of SCA level wind gusts on Sunday in the east Santa Barbara Channel. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Winter Weather Advisory in effect from 10 PM Wednesday to noon PST Thursday for zone 38. (See LAXWSWLOX). Winter Storm Watch in effect from Wednesday afternoon through Thursday morning for zone 52. (See LAXWSWLOX). Winter Storm Watch in effect from Wednesday afternoon through Thursday afternoon for zone 53. (See LAXWSWLOX). Winter Storm Watch in effect from Wednesday evening through Thursday evening for zone 54. (See LAXWSWLOX). Winter Storm Watch in effect from late Wednesday night through Thursday evening for zone 59. (See LAXWSWLOX). PZ...Small Craft Advisory in effect until 3 AM PST Wednesday for zone 676. (See LAXMWWLOX). && .HAZARD POTENTIAL OUTLOOK (FRI-TUE). High surf possible Friday, mainly along the Central Coast. && $$ PUBLIC...MW/Rorke AVIATION...Rorke MARINE...Sirard SYNOPSIS...Kj
Area Forecast Discussion
National Weather Service Pueblo CO
302 PM MST Tue Dec 24 2019 .SHORT TERM...(This evening through Wednesday) Issued at 302 PM MST Tue Dec 24 2019 Initial upper wave lifting northeastward through Arizona this afternoon, with precip spreading into wrn CO from ern AZ and nwrn NM. Wave looks fairly vigorous, with even some occasional lightning associated with stronger convection over far srn AZ earlier today. Overnight, as disturbance moves through the area, expect precip to expand across srn CO, with San Juans looking most favored for heavy snow, especially in the 00z-09z timeframe. Advisory here looks fine, with even some spotty 8+ inches possible by early morning on west facing slopes/Wolf Creek Pass area. Remaining mountains and interior valleys will see a period of snow showers overnight, with some light accumulations over mainly the higher peaks of the Sangres and Sawatch range. NAM and a few runs of the HRRR have even suggested some snow showers on the plains late this evening as wave comes across, and will throw in some minor pops for much of the east with the updated forecast. Not expecting anything significant away from the mountains, but a few spots could at least see some Christmas Eve snowflakes to enhance the holiday spirit. On Wednesday, upward vertical motion weakens as main wave shifts northeastward into the plains, leaving only some light snow showers over the higher peaks of the Continental Divide by late afternoon. Westerly component to low and mid level flow should keep max temps on the mild side once again, with a few near 60f readings on the plains by late day. .LONG TERM...(Wednesday night through Tuesday) Issued at 302 PM MST Tue Dec 24 2019 Wednesday night-Thursday night...Moderate southwest flow aloft across the region Christmas night becomes more west to southwest through the day Thursday and into Thursday night, as one embedded short wave, ejecting from the deep upper trough across the West Coast, translates across the Rockies, with short wave ridging then progged to build across the region ahead of more eastern Pacific energy digging across the southern California Coast. This system is progged to develop a closed cutoff low across southwest Arizona by 12Z Friday. The Wednesday night passing wave keeps light orographic snow showers in place along and west of the Continental Divide through the day Thursday, with its associated weak cold front translating across the plains Wednesday night, ushering in slightly cooler temperatures (closer to seasonal norms) for Thursday. Latest models are trying to generate some showers along this cold front Wednesday evening/night across the plains, however, the lower atmosphere looks to remain too dry for anything but a flurry, mainly along the Palmer Dvd. Friday-Sunday...Still a lower confidence forecast through the upcoming holiday weekend, as operational models continue to experience run to run differences on timing and location of the southern stream cutoff low and its merging with developing northern stream energy digging across the Northern Tier. The latest GFS and Canadian runs remain similar to their previous runs, however, the latest 12Z EC run is much different as tries to lift the cutoff low across the Central Rockies. At any rate, model ensemble means (including the EC) have moist south to southwest flow developing across southern Colorado through the day Friday as the southwest cutoff low slowly lifts north and east into central New Mexico, with the low weakening as it merges with a strong northern stream trough digging across the Rockies Friday night and Saturday. With that said, forecast challenges remain how far west will the main precipitation shield set up and how fast the colder air associated with the northern stream system moves across the Rockies. For now, I stayed with current NBM pops, which has chance to likely pops across the southern tier of Colordo and out across the far southeast plains Friday and Friday night, with lesser chances the further north and west you go. Precipitation chances continue through Saturday night, though with developing north to northwest flow behind the merging systems, would tend to believe snow showers would be mainly confined to the higher terrain. Currently, snow levels across the area on Friday are between 6000-7000 with mainly rain forecast across the plains until snow levels fall later Friday evening. With that said, the best chances of accumulating snow and travel impacts through the period look to be across the southern mts, though too many uncertainties are abound for any real handle on snowfall amounts. Temperatures at to below seasonal levels remain in the offing for the weekend, with Saturday currently looking to be the coldest day, with breezy north to northwest winds expected areawide. Monday-Tuesday...Slightly warm (near seasonal) and drier weather looks to be in place across the region into early next within modest northwest flow aloft, save for possible orographic snow across the northern and central mts. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 302 PM MST Tue Dec 24 2019 At KCOS and KPUB, VFR the next 24 hours with light winds. At KALS, VFR through late afternoon, then a chance of snow showers develops after 00z, bringing occasional IFR conditions through the night. May even see some patchy fog for a few hours as precip ends toward 12z. VFR conditions then return by 17z-18z. && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 PM MST Wednesday for COZ068. && $$ SHORT TERM...PETERSEN LONG TERM...MW AVIATION...PETERSEN
For frequently asked questions about the Area Forecast Discussion
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday) Issued at 300 PM CST Tue Dec 24 2019 Unseasonably warm weather and quiet conditions persist through Christmas Day. The axis of a broad longwave upper-tropospheric ridge has started propagating eastward over the last 24 hours as a sharp meridional shortwave trough over NW Mexico begins lifting northeastward. This trough de-amplifies as it tracks overhead tonight, with the trough axis passing through by 12Z Wednesday. A region of DCVA ahead of the shortwave should promote an increase in mid to upper level saturation/clouds, but the transient nature of the forcing, coupled with a dry lower-troposphere, should inhibit any precipitate generated aloft from reaching the surface. Expansive cirrostratus emanating from the east-central Pacific and streaming around the mean West Coast longwave should persist through tomorrow, with a break in the clouds likely Wednesday morning owing to localized subsidence behind the departing shortwave. At the surface, a broad region of depressed pressure values extending northeastward from a Front Range lee cyclone should tighten into a more pronounced trough tonight into Wednesday as the mean longwave trough across the West deepens. The boundary stalls during the day on Wednesday owing to subtle height rises behind the departing shortwave, but should begin advancing into the forecast area by Wednesday evening. Highs today reached the low to mid-60s despite the ample high cloud cover and readings on Christmas Day should reach similar if not higher values. The EC /GFS-based MOS guidance and the raw RAP temperature fields indicate a region of higher temperature values along and just ahead of the front, a feature often observed in these scenarios and have boosted temperatures in these areas to account for this possibility. .LONG TERM...(Wednesday night through Tuesday) Issued at 300 PM CST Tue Dec 24 2019 A storm system affects the area Friday through Sunday with colder temperatures arriving in its wake. The surface cold front pushes through the forecast area by midday Thursday, though with only weak CAA behind the front, highs may still reach the mid-40s to low 50s during the daytime hours. Surface high pressure spreads along the Platte River Valley Thursday night, ahead of a secondary H300 shortwave ridge working along the downstream flank of the upper wave cutting off over the northern Baja. Model guidance solutions differ on the spatio- temporal evolution of the upper low as it lifts northeastward Friday through Sunday. However, there is a strong concensus in a prolonged period of moderate to locally heavy precipitation from Friday through Sunday. Isentropic upglide over the baroclinic zone lifting northward as a warm front on Friday will be the main driver for light to moderate rainfall, with increasing upper level kinematic support with the maturing H300 wave and frontogenesis associated with an advancing cold front driving a more intense swath of rainfall Friday night into Saturday. GFS forecast soundings even show a narrow ribbon of 50-100 J/kg of MUCAPE in the eastern forecast area Friday night/Saturday morning and have added a slight chance of thunderstorms to the forecast. Temperatures will also rebound for Saturday in the warm sector positioned over the eastern forecast area, with many locations reaching the 50s. Moisture transport vectors through the lower to middle troposphere parallel the frontal orientation on Saturday, enabling for repetitive rounds of rainfall along the sharply-sloped frontal surface. In addition, forecast PWATs of 0.75 to 1 inch would be in the 99th percentile of observed values for Topeka in late December, underscoring the unusual moisture fetch attendant with this system. The mean 12Z GEFS storm-total QPF for Topeka is centered around 1.5 inches, with a solid clustering of members between 1 and 2 inches. Whether a deformation zone forms within the colder sub-freezing airmass on Sunday remains even more uncertain and hinges on the structure of the lower to mid- troposphere cyclone, thus the forecast contains a broad region of lower PoPs through Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 536 PM CST Tue Dec 24 2019 VFR continues at terminals as a strengthening LLJ ensues aft 00Z, increasing low level speed shear from the southwest at 40 kts, up to 50 kts aft 03Z. Some of these winds may mix down to the sfc, keeping sfc winds near 10 kts sustained overnight. Gusty winds return shortly after sunrise with the potential for restricted ceilings dropping southward shortly after the forecast period. && .CLIMATE... Issued at 300 PM CST Tue Dec 24 2019 Record high temperatures for December 25: 68 degrees at Topeka, set in 1922 and 2016 64 degrees at Concordia, set in 2016 && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Skow LONG TERM...Skow AVIATION...22 CLIMATE...65/Skow