Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/20/19

Area Forecast Discussion
National Weather Service Amarillo TX
608 PM CST Tue Nov 19 2019 .AVIATION...00z TAF Cycle... Expect VFR conditions with increasing high clouds through the overnight period. Cigs will begin to fall after 12z Wednesday with overcast conditions increasing in conjunction with shower activity from west to east. A few thunderstorms are also possible, favoring the southern most terminal (KAMA), however thunder can`t be ruled out at any location. Areas of MVFR cigs/vsbys will be possible with this activity, with the main window being between 16z and 22z. After 22z, sky conditions should gradually improve from west to east. Southerly winds will generally be around 10 knots or less overnight, but will become more southwesterly and gusty during the day tomorrow. A few gusts around 30 to 35 knots will be possible. Also can`t rule out some localized wind gusts and heavy rain associated with any thunderstorms that develop. Finally, some marginal wind shear is possible overnight tonight at all three terminals. Ward && .PREV DISCUSSION... /Issued 402 PM CST Tue Nov 19 2019/ SHORT TERM... Current satellite and model analysis depicts an H5 closed low approaching the northern Baja Peninsula. This low which is cut off from the main flow aloft, has been stationary over the past few days. It is now showing signs of moving to the northeast like models have hinted at. Moisture transport is apparent in the water vapor product on the east side of the low. Moisture is moving into Mexico and New Mexico as well as Southwest Texas and is expected to be in the area by tomorrow. This low is progged to move northeast and enter the FA tomorrow as a shortwave. The combination of the shortwave and moisture will help with creating rain showers and some thunderstorms during the day tomorrow. Down stream from the open short wave trough the upper level jet dynamics increase, with wind speeds reaching around 60 kts at H5, even higher at H2, during the afternoon tomorrow. This will increase the over wind shear available. The amount of CAPE available for severe thunderstorms to be possible has been low. Now some models are trending slightly higher with MLCAPE around 500 to 600 J/Kg. The overall bulk shear is approaching 50 knots which is impressive if the instability ends up being there tomorrow. If some more CAPE becomes available we cannot rule out some isolated severe storms tomorrow mainly for the eastern FA. Interestingly enough, the 15Z run of the RAP does show MLCAPE values reaching 1200 to 1500 J/Kg for the eastern FA. It also depicts dewpoints briefly reaching the 60s in the late afternoon. The NAM however, only has dewpoints reaching the mid 50s and does not have such high CAPE. The models with the lower CAPE may be picking up on the cloud cover we could see most of the day with all the moisture coming in. With all that said cannot entirely rule out an isolated severe storm tomorrow, and will have to monitor the trends in the model with next runs. Tomorrow winds will pick up again around 20 to 25 mph as a lee side surface low develops in southeast Colorado late morning. The pressure gradient will be enough to drive some gusty winds. The chances for rain will develop from west to east through out the day with traversing of the upper level trough. The available CAPE for thunder will probably be more in the afternoon for the south and eastern FA. Temperatures should still be able to get into the 60s before the next cold front moves through Wednesday night. Hoffeditz LONG TERM...Wednesday Night through Tuesday... Long anticipated disturbance that is going to kick out the Baja low and evolve into a closed low in the vicinity of SRN CA is now visible on WV near the Pacific NW. Will be interesting to see how much model forecast may change the next couple days as the upper air network samples these system better. For now, models are in decent agreement on the big picture pattern that shows the low moving ENE up through the trough axis (somewhat odd) toward a northern stream strong s/wv that will be moving into the mid-west on Thursday. Despite the agreement, there are a lot of complexities with several models showing a new low center forming further east from the original and becoming the dominant center( also a bit odd) and am not at all confident in these solutions as of yet. If forecasts do hold, the combination of a H250 jet impulse and strong H5 s/wv rotating around the large system will track mainly across the NW Panhandles. The initial fropa will have occurred early Thursday, but a secondary surge will arrive from NW to SE late Thursday afternoon through Friday morning. Differences in the timing and strength of the secondary surge will be key for snowfall potential as will the degree of dynamic cooling produced by the storm system. Several models are showing a H85 wave developing across the far southwest Panhandles which increases the H85 frontogenesis and therefore QPF across the wrn Panhandles. Again, how quickly the atmosphere cools will be huge wrt how much snow accumulation occurs and how far southeast accumulations occur. In general, with these dynamic systems, the faster cooling and quicker frontal progression tends to verify it seems and not crazy about the warm ECMWF H85 forecast. Taking this all into account, the NW Panhandles continue to have potential best potential for a 1-2 inch snow (possibly 1-4 if things come together) esp NW of a Hooker to Hartley line based on current models with lighter accumulations possible a county or two south. There is some concern for a mix of sleet as precip types change from rain to snow, and a mid level dry slot will decrease the moist layer providing some potential for a mix of light freezing rain or drizzle mainly south of the best snow area. Can`t completely rule out a brief period of wintry precip in the far SE, but the window appears brief and closer to sunrise Friday and marginal temps suggest minimal to no impacts if frozen precip does occur across the far SE. Minor changes in H5 evolution and H85 temps can/will strongly impact snow forecast, so stay tuned. Will remain slightly on cool side to start the weekend, but will be near or slightly above normal wrt temps by Sunday aftn. Similar conditions for Monday will be followed by the next cold front and cooler conditions by Tuesday. The assoc upper level system is forecast on vigorous side and both the GFS and ECMWF cut off the H5 low across the Panhandles as it traverses the area, although the ECMWF is 12 hours faster. This will bring the next chance for rain and/or snow to the area Tuesday. Some accumulations would be possible with GFS/ECMWF forecast and it wouldn`t take much of a jog south, to make this system even more interesting with greater potential for an impactful snow event. Gittinger && .AMA Watches/Warnings/Advisories... TX...None. OK...None. && $$ 7/15
Area Forecast Discussion
National Weather Service Green Bay WI
706 PM CST Tue Nov 19 2019 New Information added to update section .UPDATE... Issued at 704 PM CST Tue Nov 19 2019 Low-level moisture across the area, along with a temperature inversion aloft, has led to increasing fog formation across central into north-central Wisconsin. Surface dewpoint depressions are steadily decreasing across those locations along with very light winds, which will lead to increasingly dense fog through the late evening and overnight hours. Hi-res model guidance continues to indicate visibilities dropping below a half to a quarter mile at times overnight into the early morning hours. Farther east, confidence in visibilities dropping below a mile is much lower; therefore, east-central and far northeast Wisconsin has not been included in the advisory. Will monitor observation trends in those locations for potential expansion later tonight. In addition to the fog, surface temperatures are expected to drop to near or just below freezing. This may lead to some freezing fog development and may cause slippery travel on untreated and elevated surfaces. && .SHORT TERM...Tonight and Wednesday Issued at 228 PM CST Tue Nov 19 2019 The latest RAP analysis and satellite/radar imagery show weak shortwave energy moving across the northern Mississippi Valley early this afternoon. Spotty light returns on area radars are reaching the ground, primarily over north-central WI, in the form of light snow. Little to no signs of freezing drizzle/drizzle and visibilities have slowly improved through the day. Some of the lowest visibilities reside within a weak surface trough over the western part of the state. Otherwise, widespread low overcast continues to prevail across the region and extends across Minnesota and eastern Dakotas. As temperatures cool tonight, forecast concerns revolve around fog/freezing fog potential, followed by cloud trends on Wednesday. Tonight...The weak surface trough over western Wisconsin is expected to dissipate later today or this evening, but ample low level moisture will remain beneath the subsidence inversion. Forecast soundings show inversion heights falling and with nocturnal cooling, so should see cloud heights fall as well. Statistical and probabilistic guidance also supports falling visibilities over central and north-central WI. Unsure if a dense fog advisory will be needed, but with temps falling below freezing over central and north- central WI, freezing fog onto road surfaces may lead to slippery or even icy stretches. Will add a mention to the hazardous weather outlook. Just like the past several nights, temps will not fall much, and leaned on the previous nights lows heavily once again. Wednesday...Low stratus and fog will likely persist through much of the morning as a surface ridge axis moves into central WI. With daytime heating, increasing anticyclonic flow, and warming low level temps, it`s possible that partial clearing will occur during the afternoon. On the other hand, ample mid and high clouds will be streaming into the region ahead of the next system, so will likely see filtered sunshine at best where low stratus erodes. Stayed close to the previous forecast for high temps, but may have to be adjusted pending cloud cover. Most locations will see highs ranging from the upper 30s to low 40s. .LONG TERM...Wednesday Night Through Tuesday Issued at 228 PM CST Tue Nov 19 2019 A strong low pressure system is expected to arrive Wednesday night into Thursday, and the GFS/GEFS/ECMWF are in very good agreement on timing and a track through east central Wisconsin. Low-level thermal profiles and thicknesses suggest all rain across the forecast area Wednesday night. The rain/snow line is expected to gradually shift southeast across north central WI on Thursday, but the heavier precipitation should be tapering off as this occurs. Could see 1 to 3 inches of accumulation over Vilas county by evening, aided by lake-enhancement late in the day. Farther southeast, a surge of gulf moisture, with PWATs exceeding 1 inch, will lead to moderate rainfall late Wednesday night into Thursday morning, with rainfall totals likely reaching 0.75 to 1.0 inch. With frost depths of 4+ inches over the forecast area, runoff from the rain could cause minor flooding issues. There is also some concern for minor lakeshore flooding and erosion on the Lake Michigan shoreline, as 6-9 foot waves batter the coast late Wednesday night into Thursday morning. The locations most susceptible to flooding and erosion would be the eastern shore of Door county, and the Two Rivers area, where wave action will be most perpendicular to the coast. Winds will become offshore Thursday afternoon, so impacts will lessen with time. This event is NOT expected to be nearly as impactful as the event on October 21st. As the low pressure system exits, there will be potential for a brief period of light lake effect snow showers over north central WI Thursday night. The weekend looks quiet, with systems tracking north and south of the forecast area. Looks like a generally dry weekend, with temperatures near seasonal normals. Low pressure developing near the TX/OK panhandle early in the work week will lift toward the region on Tuesday, bringing a chance of rain or mixed rain/snow. Models show this system strengthening as it lifts into the western Great Lakes region Tuesday night into Wednesday. The current track would appear to be too far west for a significant snowfall in GRB CWA, but we are 7-8 days out, so significant changes are likely to occur. At a minimum, this system should impact early travel for Thanksgiving Day. && .AVIATION...for 00Z TAF Issuance Issued at 510 PM CST Tue Nov 19 2019 Widespread low stratus and some reduced visibility has been noted across a large portion of the area this evening. MVFR to IFR conditions are expected to linger through much of the TAF period with some LIFR visibility possible across central and north- central WI overnight into Wednesday morning. This would mainly impact the CWA/AUW/RHI TAF sites. Some freezing fog potential is also possible; however, not overly confident in this occurring as temperatures are near to slightly above freezing. Otherwise, some improvement will likely occur, especially in visibilities, during the day Wednesday. && .GRB WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 9 AM CST Wednesday for WIZ005-010-018- 030-035-036-045. && $$ UPDATE.........Cooley SHORT TERM.....MPC LONG TERM......Kieckbusch AVIATION.......Cooley
Area Forecast Discussion
National Weather Service Hanford CA
1202 PM PST Tue Nov 19 2019 .SYNOPSIS... Low pressure will move into the region from the north tonight and Wednesday bringing a chance of rain and mountain snow along with cooler temperatures. The low will move east on Thursday with a return to dry weather. && .DISCUSSION... The focus in the short term continues to be on the two low pressure systems along the West Coast. The southern closed low off the coast of Baja will continue to push a surge of moisture into SoCal and Arizona, while the northern digs south. Ahead of the northern one is some shortwave energy which has edged the cold front into the area. Not expecting much out of that frontal passage, but can`t rule out high elevation snow. The real focus is on the main low digging south as it packs a lot more energy and will phase in the southern low overnight. Before that happens however strong northerly winds associated with the northern low will bring some fire weather concerns to the northern half of the state. Though, Merced County will some breezy winds not expecting nearly the impacts in our area due to the orientation of the valley relative to the winds. With respect to precipitation things should be quite benign until the southern low gets phased into the other as this will bring some of the tropical fetch. Still, the bulk of the moisture will remain southeast of the area, though enough rap around moisture will bring some mountain snow and valley/desert rain. Given the moisture axis and upper level flow the main area for precipitation will be along the Sierra Nevada, Greenhorn Mountains, and Tehachapi Mountains. The western San Joaquin Valley north of Kings County will likely be left out as the measureable precipitation is expect east of Highway 99 for the most part. For the extend, the jet stream remains quite wavy across the area, though things look dry. The good news for the time being is this keeps the eastern Pacific ridge from settling over us. && .AVIATION... Areas of MVFR visibilities in haze can be expected in the San Joaquin Valley with local IFR/LIFR visibilities due to fog through 18Z Tuesday. VFR conditions will prevail elsewhere over the central California interior during the next 24 hours. && .AIR QUALITY ISSUES... On Tuesday November 20 2019... Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Fresno... Kern... Kings... Madera... Sequoia National Park and Forest and Tulare Counties. Further information is available at && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is high. Certainty levels include low...medium...and high. Please visit for additional information an/or to provide feedback. && .HNX WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from 10 PM this evening to 4 PM PST Thursday for CAZ192-193. Winter Storm Warning from 4 AM Wednesday to 4 PM PST Thursday for CAZ194>197. && $$ Meadows
Area Forecast Discussion
National Weather Service Lincoln IL
924 PM CST Tue Nov 19 2019 .SYNOPSIS... Issued at 326 PM CST Tue Nov 19 2019 Widespread fog will develop across central Illinois tonight...resulting in reduced visibilities for the Wednesday morning commute. Once the fog dissipates, a partly sunny and mild day is anticipated on Wednesday with afternoon high temperatures topping out in the lower to middle 50s. && .UPDATE... Issued at 924 PM CST Tue Nov 19 2019 Forecast looks ok for now, but thinking that dense fog is going to develop tonight in the west and possibly spread east as low clouds over the area push to the east. ALready seeing some indications of fog developing in obs and satellite loops in west central IL. Satellite also showing clouds moving east as west. Light winds over most of the area and clear skies appear to be setting the stage for this, along with the light precip we had today. Believe cross-over temp is mid to upper 30s and we are forecasting overnight lows in the lower again another reason to think dense fog will develop tonight. Going to issue a dense fog advisory for tonight through 9 am tomorrow in west part of CWA. Concern will have to expand east...but will do as needed. Update will be coming. && .SHORT TERM...(This evening through Wednesday) ISSUED AT 326 PM CST Tue Nov 19 2019 21z/3pm satellite imagery continues to show overcast conditions across much of central Illinois: however, the back edge of the cloud cover has advanced as far east as a KBRL to KMVN line. Based on satellite loops and HRRR forecasts, it appears skies will clear everywhere south of the I-74 corridor over the next 3-4 hours...while skies remain mostly cloudy further northeast. With clearing skies and decreasing winds, the potential for fog development tonight will be high...especially given the moist boundary layer from today`s light rainfall. RAP/HRRR/NAM/GFSLamp all suggest fog forming west of I-55 early this evening, then spreading eastward across the remainder of the area overnight. Given strong signal from model guidance, have gone with widespread fog except across the far SE KILX CWA where rain did not fall today. Overnight lows will be in the lower to middle 30s. Once the morning fog dissipates, a partly sunny and mild day will be observed on Wednesday with afternoon highs in the lower to middle 50s. .LONG TERM...(Wednesday night through Tuesday) ISSUED AT 326 PM CST Tue Nov 19 2019 The next significant storm system to impact the Midwest will come into the picture late Wednesday into Thursday. As has been advertised for the past several model runs, it appears the most significant rainfall will occur across central Illinois late Wednesday night and Thursday morning...followed by a lull in precip chances Thursday afternoon as a dry slot works into the region. Have carried categorical PoPs west of the I-57 corridor after midnight Wednesday night, then everywhere Thursday morning. Total rainfall will generally range from one quarter to one half an inch. Once the system passes to the east, the trailing frontal boundary will stall in the Ohio River Valley late Thursday into Friday. Several weak impulses will interact with the front to keep precip chances alive across central Illinois, with the best chances focused south of I-70. The airmass will become cold enough to support light snow or a light rain/snow mix on the northern edge of the precip area late Thursday night and again Friday night: however, little or no snow accumulation is expected. After that, mild and dry conditions will be on tap Saturday through Monday...with temperatures climbing back into the 50s by Monday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 601 PM CST Tue Nov 19 2019 IFR cigs will remain at BMI and CMI through the night and into tomorrow morning. DEC and PIA are MVFR but should scatter out by 3-4z...while SPI is VFR. The clearing that occurs across the area will combine with light winds tonight, resulting in ideal conditions for dense fog to develop across the central part of the state and likely spread east toward morning. IFR and LIFR conditions are also likely late tonight through tomorrow morning, but then improving quickly during the afternoon. Winds will become light and variable for the night and then as they increase tomorrow to over 10kts, the direction will be southeast. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Auten SYNOPSIS...Barnes SHORT TERM...Barnes LONG TERM...Barnes AVIATION...Auten
Area Forecast Discussion
National Weather Service New Orleans LA
718 PM CST Tue Nov 19 2019 ...EVENING UPDATE... Performed a gridded forecast update this evening - with the main focus being forecast lows tomorrow morning/highs tomorrow afternoon and dense fog potential early AM. Taking a look at the latest 00Z HRRR guidance valid for 12Z tomorrow morning, comparing it to what was initialized in the 12Z run yesterday morning shows a similar overall atmospheric profile. Only notable difference is a slightly stronger surface subsidence inversion and a bit more of a southerly surface to low-level flow developing (to around 1,000ft AGL). Given this, areas of dense fog will likely develop again around the same areas as last night (generally along/west of I-55 including the southshore and coastal southern Louisiana). Will likely issue a Dense Fog Advisory later tonight before 10PM to get an early heads up for those traveling early tomorrow morning, with possible expansion where needed as observations indicate. Similar to last night, blended guidance continues to come in a bit too warm with overnight lows. Dropped temperatures slightly (not as much as last night) with focus on area drainages from the northshore east across the MS coast). Blended guidance still is struggling with afternoon highs a bit, as some locations today reached the mid to upper 70`s - which confirms this cooler bias. Have manually bumped up highs tomorrow to a more realistic forecast. KLG && .PREV DISCUSSION... /issued 332 PM CST Tue Nov 19 2019/ High pressure is in place and will persist through Thursday. This high pressure is bringing drier air and a bit warmer air into the region for the next few days. Wednesday and Thursday, winds will primarily be southerly, bringing in some moisture from the Gulf into the region as well. Friday and Friday night, a low pressure system will move through the area. Winds leading up to the event will remain southerly, continuing to fuel moisture into the area. Some upper level divergence will help to provide some lifting for the area Friday. The abundant moisture presence combined with the lifting will further be enhanced by the front, however, this front currently seems weak, looking at the models. As a result, there will likely be rain showers with the chance of a thunderstorm Friday and Friday night. If the front remains weak like the models show, then the threat of severe weather would be low. The main threat if the front remains weak would just be rain and scattered thunderstorms. In addition, some gusty winds and frequent lightning would be a concern Friday and Friday night as well. Saturday through the beginning of next week, high pressure builds in, which will help to stabilize the atmosphere. In general, this stable air will help to dry out the area, so the rain chances are pretty low for the beginning of next week again. MSW .AVIATION... .UPDATED 2308Z... Expect prevailing VFR conditions for all area terminals through late evening/early tonight prior to 04-06Z. Main hazard to focus on for terminals along and west of I-55 (including KNEW/KMSY) will be patchy areas of dense fog. Primary time line will be between 06Z and 13Z, or till shortly after sunrise. Impacts to flight categories (IFR/LIFR) can be expected in this time range before all fog dissipates after 13-14Z returning all terminals to VFR. KLG .MARINE... Winds will be variable today, shifting to southeasterly tonight and tomorrow and calm (<15 knots). Winds will be southerly and light (<15 knots) through Saturday. Saturday through Sunday, winds will be stronger (15-20 knots) and northerly. Sunday through early Tuesday morning, winds will be northerly and calm (<15 knots). Tuesday through Wednesday, winds will be southerly and stronger (15-20 knots). Wave heights will correspond with the wind speeds. MSW .DECISION SUPPORT... DSS code: Blue. Deployed: None. Activation: None. Activities: None. Decision Support Services (DSS) Code Legend Green = No weather impacts that require action. Blue = Long-fused watch, warning, or advisory in effect or high visibility event; Marginal risk severe or excessive rain. Yellow = Heightened impacts with short-fused watch, warning or advisory issuances; radar support for slight risk severe or excessive rain. Orange = High Impacts; Enhanced risk severe; nearby tropical events; HazMat or other large episodes. Red = Full engagement for Moderate to high risk of severe and/or excessive rainfall, or direct tropical threats; Events of National Significance. && .PRELIMINARY POINT TEMPS/POPS... MCB 45 75 50 74 / 0 0 0 0 BTR 46 78 53 77 / 0 0 0 0 ASD 44 75 50 75 / 0 0 0 0 MSY 51 75 56 75 / 0 0 0 0 GPT 47 72 52 72 / 0 0 0 0 PQL 43 75 49 75 / 0 0 0 0 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...None. GM...None. MS...None. GM...None. && $$
Area Forecast Discussion...Updated
National Weather Service Phoenix AZ
525 PM MST Tue Nov 19 2019 .UPDATE...Updated aviation discussion. && .SYNOPSIS... A series of strong low pressure systems will bring periods of heavy rain with embedded thunderstorms through tomorrow evening, especially from the Colorado River eastward. The strongest storms may also contain gusty winds Wednesday. Temperatures will fall below normal during this unsettled weather before clearing begins on Friday. Moist conditions will persist over the weekend, though no additional rain is anticipated. && .DISCUSSION... Convection developed early this morning across northern Sonora and has propagated northward into south-central Arizona ahead of a pronounced Theta-E boundary. Latest mesoanalysis shows much of Arizona generally lacks instability, with MLCAPEs > 500 J/kg confined to far southern Arizona. Nevertheless, low-level dewpoints in the 20s and 30s ahead of the boundary have helped to enhance evaporation and downdrafts with peak gusts up to 35 mph across Maricopa and Pinal counties, which has been sufficient to produce areas of patchy blowing dust. Behind the boundary, conditions have moistened considerably with dewpoints increasing into the 50s and even lower 60s at Yuma. Activity this afternoon generally materialized a few hours faster than anticipated and model performance (including the HREF and local CAMs) has struggled. In these scenarios, it is prudent to rely on a HRRR time-lagged ensemble for the near-term, which indicates that scattered showers will persist across south-central Arizona through this evening. Latest IR satellite shows cooling cloud tops across Pima County and it`s reasonable to expect this activity will lift northward this evening around the Baja Peninsula closed low. A Flash Flood Watch remains in effect, though the relatively fast storm motion of the convection may limit the flood threat. Models remain in good agreement that the focus will shift westward overnight as vorticity and jet-forced ascent increases ahead of a closed low diving down the central California coast. NAEFS continues to highlight the central Colorado River Valley with PWAT percentiles exceeding the 99th percentile. Consequently, the strongest cells will be capable of producing a very quick 1 to 2 inches, which could lead to flash flooding. This is reflected in the latest official forecast, which again is weighted heavily towards the WPC QPF. Predictability is expected to increase Wednesday as a broken line of convection develops ahead of the aforementioned low pressure system and migrates eastward across Arizona. A low-level jet intensifying to 40 kt will approach an all-time maximum across southern Maricopa County late Wednesday morning. Although the wind profile won`t be ideal for training cells, some back-building along and ahead of the line will enhance the threat of flash flooding. Latest HREF also suggests the strongest storms will be capable of producing wind gusts as high as 50 mph. General consensus is that the line of storms will move east of Gila County Wednesday evening, with isolated showers generally dissipating elsewhere. GEFS ensembles continue to show the closed low filling across northern Arizona Thursday. However, the cold pool aloft will lead to increased instability and promote the development of additional showers across Arizona. The low will move east of the region Friday, though low-level moisture will linger through the weekend. Latest ECMWF EPS suggests another upper low will be pinched off in the eastern Pacific during the weekend along with a propensity towards another Rex Block. This will yield a slight warming trend across the Desert Southwest into early next week, though temperatures will remain below normal. .AVIATION...Updated at 0025. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: A series of weather systems will continue to bring widespread showers, moderate to heavy at times, to the greater Phoenix area this evening and through the day (at least) on Wednesday. In general, we are looking at RA/SHRA to affect the terminals through the TAF period, but there is sufficient instability to permit isolated thunderstorms at times mainly during the evening hours today. For now, due to model inconsistencies with timing/location of convective cells, decided to leave thunder out of the TAFs and will simply amend as needed should storms start to threaten the terminals. Expect a thunder threat through at least 05z but diminishing after that and into the morning on Wednesday. Again, thunder might become an issue mainly Wednesday afternoon as a front approaches from the west, but confidence in timing/location of storms is too low to mention that far out in the TAF period. Outside of thunder threats, 2 additional significant aviation issues expected: CIGs and wind. Winds will stay generally southeast this evening mostly 15kt or less, then strengthen later tonight and into the morning Wednesday - favoring the south. Expect generally south winds to persist for most of the day Wednesday ahead of the slowly approaching front. Winds should turn to the southwest behind the front but this will not likely occur til after 22z. Potential is there for quite breezy south wind from mid morning into mid afternoon with gusts over 30kt likely and sustained 20kt or higher likely as well. This may pose crosswind issues, especially at KPHX. CIGS also become an issue, dropping below 6kt feet by around 06z this evening and becoming lowest mainly from 12z to 18z Wed. before starting to slowly increase. CIGs may occasionally fall below 3k feet especially during heavier showers or storms. Cannot rule out CIGs briefly below 2k but should it happen it would not persist for very long, especially at KPHX. Visibility may also drop below 5sm at times under periods of heavier rain or thunderstorms. Overall opted to paint a slightly more optimistic appraisal of the situation in the TAFs especially at longer time ranges but know that conditions could easily become more of a concern especially during the day on Wednesday. Southeast California/Southwest Arizona including KIPL and KBLH: Two weather systems will continue to bring showers to the southeast California/southeast Arizona deserts this evening into the afternoon on Wednesday. As of 5 pm convection has been very isolated in far SE California but expect coverage to become more scattered as the evening progresses; CIGS should drop into the 5-7k range for the most part with locally lowered CIGs in heavier showers or storms. Given low expected storms coverage, opted to leave out mention of storms for now but will amend if needed. Conditions should graudally improve during the afternoon Wednesday behind a cold front that will be moving into the Arizona deserts. Winds will favor the southwest to west at KIPL - especially later this evening and during the day on Wednesday, and could become rather breezy during the day with occasional gusts approaching 30kt. Winds to favor the south to southwest at KBLH for most of the TAF period with breezy conditions at times during the day tomorrow. && .FIRE WEATHER... Thursday through Monday: Showers will continue to percolate through the eastern districts Thursday while drier conditions work into the western districts. More widespread dry weather will finally spread into the region over the weekend. Regardless, given the pronounced wet weather preceding this period, fuels across the majority of the area will be quite moist for an extended period. Temperatures will cool substantially Thursday, then only rebound near the seasonal average over the weekend while humidity levels likely will not fall below 50% for an extended period. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Flash Flood Watch through Wednesday evening for AZZ534-537>563. Flash Flood Watch through Wednesday afternoon for AZZ530>533-535- 536. CA...Flash Flood Watch through Wednesday afternoon for CAZ564-565- 567- 569-570. && $$ DISCUSSION...Hirsch AVIATION...CB FIRE WEATHER...MO
Area Forecast Discussion
National Weather Service Riverton WY
338 PM MST Tue Nov 19 2019 .SHORT TERM...(This evening through Wednesday night) Issued at 230 PM MST Tue Nov 19 2019 Mid- and high-level clouds will continue streaming from the southwest over the forecast area late this afternoon and overnight. Although some models are suggesting light high elevation showers late this afternoon, web cams and satellite suggest otherwise. Breezy conditions with gusts over 30 mph will continue from eastern Sweetwater county into Natrona county through about 6pm. Strong trough in northwest flow is advancing toward the area and will increase moisture and instability overnight, with a slight chance of showers over YNP and the northern Absarokas until midnight. At the same time, a surface cold front will move southward from Montana into Wyoming. Latest HRRR model run shows the northerly winds pushing into the northern Big Horn Basin and northern Johnson county between 9pm and midnight. Although the initial push makes it into central WY before sunrise, the strength of the winds does not seems to increase until mid to late morning when the surface pressure gradient increases (due to the higher pressures moving into Montana). Precipitation is likely over the eastern Absarokas and Cody foothills as well as the northern Bighorns during the early morning hours before spreading southward late Wednesday morning. At the same time, models are showing moisture and overrunning moving northward from eastern Utah and western Colorado into Sweetwater county. By around noon Wednesday, the north to northeast wind from northern into southern WY should increase to 15 to 20 mph with gusts over 30 mph. Moderate precipitation, perhaps starting as rain but quickly changing to snow, will develop over southern WY and move quickly into central WY. Surface temperatures are expected to be at or just below freezing, so snow should be able to accumulate during the day. The combination of snow and wind will create hazardous blowing snow across much of central and southern WY. This looks to be a decent ~9 hour precipitation event with sustained overrunning and upslope. Overall, the heavier amounts are expected to be from Lander and South Pass eastward to Muddy Gap and Casper Mountain, then southward toward Wamsutter. Please see the CYSWSWRIW products for more details regarding the issued warnings and advisories. A special weather statement also mentions snow in fringe areas for 2 to 3 inches, though locally higher amounts of 4 inches could be seen in places such as Meeteetse and Ten Sleep. Models today are fairly good agreeing about the onset of precipitation and movement of the cold air and wind. Concern is for the duration of the event into Wednesday night and Thursday morning. The GFS and other global models continue to show the SW cut off low moving from Las Vegas eastward to the Four Corners area. Combining this movement with ridging over the northern Rockies would diminish precipitation quickly from the north early Thursday morning. The NAM however, is taking the low center more northeastward into central Utah. As expected, this pattern would keep more moist easterly flow into central and southern WY. Will have to monitor on subsequent shifts. .LONG TERM...(Thursday through Tuesday) Issued at 144 PM MST Tue Nov 19 2019 By 12Z Thursday, the trough responsible for the snow on Wednesday and Wednesday night will split as the southern stream circulation around the closed low over Vegas expands, and the northern stream trough scoots east and away from the area across Canada, along with the high building over the Pacific Northwest and the ridge building in the southern plains. This will put us under a col region and resulting diminishing snowfall Thursday. Snowfall will be winding down from northwest to southeast Thursday morning, with perhaps a bonus inch of snow from lingering upslope from the east slope of the Wind River Mountains to Beaver Rim. A few flurries will linger across the Casper area, Green Mtns, the southern east slope of the Wind River Mtns amd Sweetwater County through Thursday afternoon. Gradual clearing will take place from north to south Thursday night. Northern Wyoming will clear up in time for significant radiational cooling there with some below zero readings expected in YNP. Should see some patchy fog develop across portions of the Big Horn Basin by Friday morning with fresh snow cover and warm air advection from the north, strengthening temperature inversions and supplying drier air above the inversion enhancing the possibility of fog development.. Friday will feature dry and cold conditions with highs mainly in the 30s. Saturday will be another dry day with highs reaching the low 40s in many areas. Southwest winds will pick up along the southern wind corridor from the Red Desert and South Pass to Casper Friday, coincident with the developing sfc lee side trough. These breezes will continue through the weekend. Temperatures will likely be a few degrees cooler in areas where the wind does not blow, including the western and central basins where temperature inversions could linger through Friday given the fresh snow cover. By Sunday, the high over us that will build in from the Pacific NW will get swallowed up in the westerly progressive flow. The westerly flow will become somewhat difluent Sunday with snow developing in northwest Wyoming out ahead of the next upstream trough. The models appear to be agreeing upon the timing of this trough coming through Monday as it digs, with most of the energy propagating to the Desert Southwest. Monday will be the apex of the snowfall associated with this trough with the far west receiving the brunt of the snowfall given the upslope flow there. Tuesday will see snowfall decreasing but lingering in the northwest ahead of the next upstream shortwave, with the Euro the fastest with the approach of this next shortwave. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 331 PM MST Tue Nov 19 2019 JAC/PNA/BPI...Western state locations will continue to see clouds increase, thicken, and lower this evening as the next push of cold air arrives. Expect rain showers in northwest Wyoming at the lower elevations, including the vcnty of KJAC, along with snow showers in the surrounding mountains. The front will move through after midnight, bringing gusty north winds in its wake. Any wintry precipitation will likely not arrive until after 12Z Wednesday. MVFR/IFR conditions will occur in the southwest including KPNA and KBPI through Wednesday along with mainly MVFR conditions at KJAC. Expect mountain obscuration Wednesday. Eastern and southern sites...VFR continues for the rest of this afternoon for all sites, with generally light winds noted. Breezy southwest winds increase tonight for the corridor from South Pass to Casper, reaching 15g25kts at times. Then the front arrives. Northern sites should see north winds arrive around midnight in KCOD, 09Z in KWRL, reaching RIW/LND/CPR around 11Z, and passing RKS around 13Z. Gusty north winds of 20 to 25 kts are expected through the day Wednesday associated with the front moving north to south. Snow will develop behind the southbound moving front, across the north after midnight. Then snow will increase across central and southern WY after sunrise Wednesday. MVFR/IFR conditions and mountain obscurations expected after 12Z Wednesday for the central and southern locations. && .FIRE WEATHER... Issued AT 144 PM MST Tue Nov 19 2019 Warm temperatures continue for one more day, with highs in the 50s for the rest of this afternoon. Winds from Rock Springs to Casper will reach 20 to 30 mph with higher gusts for the rest of this afternoon. The cold front sweeps through overnight, with an abrupt wind shift from the north at 20 to 30 mph. The front will bring snow for most of the state, with several inches possible at all elevations by later Wednesday. The snow will continue through Wednesday night and then taper off from northwest to southeast Thursday. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from 5 AM Wednesday to 11 AM MST Thursday for WYZ015-018-019-022-030. Winter Weather Advisory from 5 AM Wednesday to 5 AM MST Thursday for WYZ005-007>011. Winter Weather Advisory from 5 AM Wednesday to 11 AM MST Thursday for WYZ017-020-027>029. && $$ SHORT TERM...McDonald LONG TERM...Lipson AVIATION...Lipson/Fisher FIRE WEATHER...Lipson
Area Forecast Discussion
National Weather Service Sacramento CA
341 PM PST Tue Nov 19 2019 .SYNOPSIS... Pattern transitioning to breezy to windy conditions, cooler temperatures and possible showers over mainly the Sierra Nevada south of I-80. && .DISCUSSION... The upper level trough is showing up nicely on water vapor and is currently still an open wave along the CA coast. Over the next few hours we will see this trough close off near Monterey and drop south into SoCal by Wednesday mid morning. Showers have started to develop mainly along the Sierra crest and are quickly pushing east with the strong westerly flow. As the trough closes off easterly flow will develop and that will favor precip on the east slope of the Sierra. Last several runs of the HRRR show a band of light to moderate precip pushing over I-80 and Highway 50 and pushing down the slope to the east of Placerville and Auburn in the 7 pm to midnight range. This is somewhat of an outlier at this time as the HREF along with other models favor that band setting up to the south of Highway 50. It is something that will have to be monitored this evening as snow levels will be falling to just below pass level. Current thinking is 1-2" will be possible over I-80 and Highway 50 this evening into the overnight with the higher snow totals staying to the south where a Winter Weather Advisory is in effect. The bigger impact from this system will be the cooler temperatures and an increase in northerly wind that will develop across a large part of the area overnight and continue into Thursday as the surface gradient tighten. The period of strongest northerly winds are expected Wednesday afternoon as subsidence and upper level support increase. Gusts of 40-50 mph will be possible in the Sacramento Valley and surrounding terrain north of Sacramento. Shower chances will push south on Wednesday and will continue to favor the east slope of the Sierra but light activity will be possible in our area mainly near the crest south of 50. Snow levels will be dropping down to around 5500 feet by Wednesday afternoon and we could see some light accumulation down to that elevation but it should remain minor. Winds will die down quickly Thursday mid morning into the afternoon and we will see an upper level low set up over the Pacific on Friday. This will keep clouds in our forecast along with the cooler but still a bit above average temperatures. Light winds will continue on Friday. -CJM && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday)... To start the weekend, the region will feature an eastward extending ridge with a closed low positioned well off the southern California coast. Perhaps a few additional clouds are possible although this should not hinder temperatures much. Valley high temperatures will easily reach the mid to upper 60s with even a couple 70 degree readings in the upper Sacramento Valley. This is still quite warm for mid-November with departures from climatology on the order of 5 to 10 degrees. Although ridging will allow optimal radiational cooling at night to keep readings closer to average. Moving to next week, global ensembles continue to favor a ridge centered over the east Pacific (i.e., 140W longitude) while longwave troughing extends over the western/central U.S. Models remain adamant about a sharpening shortwave sweeping across the central Great Basin into the Four Corners. This pattern would support another bout of gusty northerly winds on Monday into early Tuesday. With extremely dry fuels in place, elevated fire weather concerns are nearly a given if this setup were to become reality. Looking further beyond, another trough may reach the West Coast by mid-week although impacts remain unclear given increasing model uncertainties. ~BRO && .AVIATION... VFR conditions the next 24 hours with winds increasing from north to south during the overnight hours. KRDD and KRBL can expect northerly wind gusts in excess of 30 knots by around 12Z Wednesday. Breezy conditions are likely over the Sacramento TAF sites starting by 15Z Wednesday with slightly lighter winds down into the upper San Joaquin Valley. ~BRO && .STO WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from 4 AM Wednesday to 7 AM PST Thursday for Central Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF- Eastern Portion of Shasta/Trinity NF-Lake County Portion of Lake- Napa-Sonoma Unit-Northern Sacramento Valley to Southern Tehama County Line Below 1000 Ft-Northern Sierra Foothills from 1000 to 3000 Ft. Includes portions of Shasta-Trinity and Butte Units- Northern Sierra Including Lassen NP and Plumas and Lassen NF/S West of the Sierra Crest (West of Evans Peak-Grizzly Peak- Beckworth Peak)-Southeast Edge Shasta-Trinity NF and Western Portions of Tehama-Glenn Unit-Southern Sacramento Valley in Yolo- Sacramento Far Western Placer, southern Sutter and Solano County Below 1000 Ft. Wind Advisory from 4 AM to 10 PM PST Wednesday for Central Sacramento Valley-Clear Lake/Southern Lake County-Mountains Southwestern Shasta County to Northern Lake County-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-Shasta Lake Area / Northern Shasta County-Southern Sacramento Valley- Western Plumas County/Lassen Park. Winter Weather Advisory until 7 PM PST Wednesday for West Slope Northern Sierra Nevada. && $$