Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/21/19

Area Forecast Discussion
National Weather Service Denver/Boulder CO
953 PM MDT Mon May 20 2019 .UPDATE... Issued at 953 PM MDT Mon May 20 2019 Heaviest snowfall is expected to continue through the midnight hour per latest radar/satellite data, and latest totals and snowfall rates prompted the upgrade to an Advisory in the immediate Denver area (2-6", heaviest on the south/east sides of town), and an upgrade to a Winter Storm Warning over the Palmer Divide where 7 to 15 inch totals likely. We may see a decrease in intensity after midnight with some drying noted to the south, but there`s still a lot of forcing later tonight through early Tuesday morning for additional accumulation in that time frame. Main impact for Denver will be broken tree limbs and scattered power outages in the areas that see the heavier totals, and some slush/snow on roads during heavier snow periods. More significant travel troubles over the Palmer Divide with much heavier totals of heavy, wet snow. UPDATE Issued at 845 PM MDT Mon May 20 2019 Radar has been showing several bands of precipitation passing north across the forecast areas, including I-70 from Bennett to Strasburg to Byers. In this area web cameras are indicating snow accumulating on grassy surfaces in locations just east of Denver, and has been heavy at times. Satellite and radar depict stratiform snow funneling up the east side of the Denver metro area tonight. For this reason the Winter Weather Advisory has been extended into eastern portions of Adams and Arapahoe Counties with snow accumulations of three to seven inches. Temperatures have trended colder as well, so we will add additional snowfall to the I-25 corridor from Denver north to Fort Collins. The upper level low is progressing towards the four corners region. Satellite imagery indicates a jet speed max sliding north up the eastern side of Colorado creating strongly diffluent flow and surface pressure falls. This will allow for more lift and heavier snow. The best time period for snowfall across the mountains, foothills, and Palmer Divide will be through the overnight period. The RAP and HRRR models have the moisture decreasing through the early morning, while the GFS and HiRes Euro keep precipitation through Tuesday. Basically, the I-25 Corridor and nearby adjacent plains and Palmer Divide area will have to be monitored closely to see how these waves of precipitation come to fruition, because at the intense snowfall rates and high water content, it won`t take long to cause some problems with more snow/slush on roads, and possibility of broken tree limbs and scattered power outages where heavier snow falls. See below for current Winter Storm Warning and Winter Weather Advisory highlights. && .SHORT TERM...(This evening through Tuesday) Issued at 238 PM MDT Mon May 20 2019 The strong upper low which is currently approaching the 4 corners region this afternoon is providing extensive strong mid and upper level ascent and diffluence over eastern CO. A narrow dry slot over northern NM and the San Luis Valley has allowed for some surface based convection to fire in area of partly cloudy skies and slightly higher cape. This is being drawn northward into the central mtns and NE CO area early this afternoon. Will expect northward moving showers to continue into the evening along with batches of weak to moderate thunderstorms passing across the higher terrain and onto the Urban Corridor and plains. Can`t rule out a few stronger storms containing brief moderate to heavy rain and small hail as they move into a supportive shear environment with a weak Denver cyclone currently in progress. Another area of convection and lift, closer the upper low near Flagstaff AZ is still behind this initial convective feature and will likely be the snow maker and for the mountains and a precip producer for the lower elevations once it arrives over the central CO. The stable drizzle-like sounding across the plains from this morning destabilizes to a degree in the mid and upper level for late and afternoon and tonight, however remains somewhat stable near the surface due to persistent and fairly deep northeast flow at the surface. Forecast cross sections and sounding become near saturated from the surface thru 400mb with lapse rates holding in the 6.5-7.5 C/km range thru the 03z to 12z Tuesday timeframe over the mountains. Can still expect warning criteria snowfall for the mountains as we typically see convective generated snowfall this time of year and especially under this type of synoptic environment. Snowfall totals of 15 inches plus will not be out of the question due to persistent showers and possible banding, especially on south and southwest facing aspects. For the lower elevations, slow levels still expected to fall near the 5000-5200ft elev as wet bulb 0C levels have come in lower on current runs. Will add Palmer Divide to the Winter Wx Advisory thru Noon Tue as 5-10 inches may be possible especially across the higher western portions of the ridge. Looking at Tuesday, will be watching for the timing and extent of drier surface downslope flow pulled off the higher terrain and onto the lower elevations of the NE plains. By 12z Tuesday, the upper closed low near the OK panhandle begins a fairly rapid exit out into NW KS by 18-21z. This will likely bring the beginning of the end to the best precip across the lower elevations as drying NW downslope flow fills in behind ejecting low. As upper low exits the region, NAM and GFS swing another trof axis across the CWA from the north for late afternoon Tue with another brief round of reinforcing cold air aloft. With this last push of cold air advection aloft this may keep the snow or snow showers going into early afternoon Tuesday across the mountains and higher foothills with weak convective rain mixed with snow showers thru afternoon across the lower elevations. By late afternoon into early evening Tue, strong QG subsidence begins to work into southern and central Colorado with rapid lowering of RHs across the CWA. .LONG TERM...(Tuesday night through Monday) Issued at 238 PM MDT Mon May 20 2019 For Tuesday night into Wednesday, the upper level low will be moving to the northeast into central NE. A deep surface low will be over western KS to south-central NE. The wrap around provided by the cyclonic flow of the surface circulation will keep strong NW flow moving into the region with high moisture. This will allow for continued showers over the plains into Wednesday morning and snow in the higher elevations. Warm air advection Tuesday will change over cold air advection as winds in the mid levels turn more to the northwest. Models are showing enough of a cool down in the mid and lower levels that some snow could mix in with the rain overnight into early Wednesday across the plains, mainly North near the Wyoming border and the northern foothills. Low temperatures for Tuesday night will be hovering around the freezing mark with values from 31 to 34 across the plains. The surface low will continue to track to the NNE through the day Wednesday pulling the energy and moisture north leaving CO in SW flow aloft. Conditions will dry over the plains with increasing subsidence but there is a slight chance of storms over the higher terrain with lingering moisture and some instability present. Highs on Wednesday will rebound slightly with temperatures in the 50s. For Thursday, the next upper level disturbance that will affect Colorado will be over Utah and is currently forecasted to push North into Wyoming and southern Idaho. At the surface, a deepening low pressure system over the southern portions of the state will move to the NNE pulling in some moisture in the cyclonic SSE flow. This could help to provide high enough dewpoints across the I-76 corridor for a chance of showers and thunderstorms Thursday afternoon. Elsewhere, lower chances of convection are possible with a chance across the higher terrain. Temperatures will continue to increase with highs projected to be in the lower 60s across the plains and 40s to 50s in the mountains. Friday and into the weekend, the upper low will continue to push North into Canada leaving Colorado in SW flow. Increasing subsidence from the SW with WAA in the mid levels will help to stabilize the plains and bring mostly sunny conditions. Temperatures will be closer to seasonal normals with highs back in the upper 60s to lower 70s with just a slight chance of convection over the mountains. This warmer and drier pattern will continue into the weekend with highs back into the 70s under just a slight chance of storms for the mountains. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 845 PM MDT Mon May 20 2019 IFR conditions with snow will remain in the forecast through early Tuesday morning. Accumulations of 2-5 inches in the grass will be possible, along with some slush on runways. The heavier amounts would favor KAPA and KDEN. Ceilings are expected to slowly lift late Tuesday morning, with more of a mix of rain and snow toward 16Z-18Z. MVFR conditions should prevail thereafter with scattered showers around and only slight improvement of ceilings. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until noon MDT Tuesday for COZ041. Winter Weather Advisory until 9 AM MDT Tuesday for COZ040. Winter Weather Advisory until noon MDT Tuesday for COZ045. Winter Weather Advisory until midnight MDT Tuesday night for COZ036. Winter Storm Warning until midnight MDT Tuesday night for COZ031- 033>035. && $$ UPDATE...Barjenbruch SHORT TERM...Fredin LONG TERM...Bowen AVIATION...Barjenbruch
Area Forecast Discussion
National Weather Service Des Moines IA
704 PM CDT Mon May 20 2019 ...Updated for 00z Aviation Discussion... .DISCUSSION.../Tonight through Monday/ Issued at 348 PM CDT Mon May 20 2019 GOES-East Clean IR Water Vapor imagery shows the upper level low over northern Arizona at the base of the upper level trough over the western US. There is plenty of convection downstream in the diffluence region of upper air pattern over the central Plains. Closer to Iowa, fair weather cumulus clouds were drifting southward across the state with the highest concentration of these low clouds over southern Iowa. Meanwhile, GOES-East Day Cloud Phase Distinction RGB showed high level clouds from the convection over Kansas moving northeastward into the state this afternoon. This will result in sunshine increasingly fading behind these clouds with regional radar showing a broad area of rain slowly moving northeastward. No rain yet in our forecast area as of 3 pm, but that will be changing as strong theta-e advection lifts over the state helping to sustain/expand the area of rain into Iowa through tonight. HRRR might be a bit fast on arrival so have blended CONSShort to slow down the timing slightly. Still, by midnight expect rain over the southern part of the state and fairly widespread showers by daybreak Tuesday. Thunder looks to be limited overnight, but still could be some peals of thunder, especially over southern Iowa. Tuesday will be a raw May day. As the upper level low rotates into Nebraska, strong theta-e advection phased with strong Q-vector convergence will yield periods of showers and thunderstorms. One period will likely be in the morning with another period late in the afternoon. The latter should be fairly progressive across the state with a narrow ribbon of precipitable water values topping 1.5 inches. Given the progressive nature of the rain and flash flood guidance values just shy of or above 2 inches at the 3 and 6 hour time steps, no widespread concern for flash flooding. However, with expected rain totals averaging between 1 to 2 inches this will certainly cause a rise on area waterways. As for the severe threat, forecast soundings show a low level inversion that should limit severe potential. Weak, elevated instability and a freezing level around 13 to 14 kft may result in a few storms that produce near severe sized hail. While SPC has maintained their slight risk over far southern Iowa, the best chance for severe storms will likely be south of the Iowa/Missouri border. High temperatures tomorrow will be close to typical lows for the date and within a few degrees of record low highs. Further, slightly deepening low pressure over western Kansas and high pressure over Ontario will tighten the pressure gradient over Iowa yielding strong winds from the east. BUFKIT soundings from the NAM/GFS/RAP show mixing limited due to the aforementioned inversion with wind gusts peaking between 35 to just shy of 40 knots. GFS soundings show stronger winds at the top of the mixed layer in the low 40s so will need to monitor for possible increase in wind gusts. The strongest winds are expected over northern Iowa and have issued a wind advisory for those areas tomorrow afternoon into tomorrow evening due to the strong, sustained winds. Wednesday looks to be the brightest day at this point and a day to do any outside activities. Winds will not be as strong as Tuesday as surface low pressure passes north of the state, but it will still be a breezy day and much warmer as well with highs mainly into the 70s. Sunshine should become plentiful by the afternoon. The next chance for storms will come later Thursday into Friday as a new upper level low drops into the western US trough and begins to lift out over the Plains. At the surface, a warm front will lift over the state, but looks later in the day than previous model solutions. While parameters are not as impressive, would still expect strong thunderstorms in an environment characterized by up to 1000 J/kg of MUCAPE and strong, supportive deep layer shear with mid- level lapse rates of 7 to 8C/km. Obviously, there will be some timing changes as was noted so will keep a watch on this period for severe risk over Iowa. While a cold front will try to move through the state, it looks likely to stall over the region and keep chances for showers and storms into at least part of the Memorial Day weekend. && .AVIATION.../For the 00Z TAFS through 00Z Tuesday evening/ Issued at 641 PM CDT Mon May 20 2019 Multiple forecast "hazards" in this forecast... Precipitation, Winds, lowering CIGs. Precipitation... High confidence in precipitation occurrence overspreading Iowa from south to north throughout this TAF period. Left thunder mention out of TAFs now... cannot rule our a stray lightning strike or two tonight, but very minimal coverage/potential of thunder not high enough to warrant separate FM group mentioning thunder at this time. Winds... High confidence in strong winds Tuesday morning into Tuesday evening... especially across northern Iowa... KMCW and KALO... with peak winds occurring during Tuesday afternoon. Several FM groups likely will be needed for increasing and later decreasing winds... some gusts of which could exceed 40 to 45 kts during Tuesday afternoon. Winds at KMCW should be a solid 10 kts or so higher than at KDSM. CIGs... Along with the arriving precip, CIGs will be gradually lowering throughout the TAF period. Challenge will be timing IFR CIG arrival... High confidence in IFR... so a matter of when, not if. The when appears to be around sunrise at KDSM, late morning around KFOD, and KALO, and then early afternoon at KMCW. Will obviously be refining these times in future updates. As of now, LIFR does not appear to be likely, but LIFR cannot be ruled out at KDSM sometime around early afternoon at KDSM. Will monitor this also. && .DMX WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 1 PM to 10 PM CDT Tuesday for IAZ004>007- 015>017-023-024-033-034. && $$ DISCUSSION...Ansorge AVIATION...Kotenberg
National Weather Service Kansas City/Pleasant Hill MO
633 PM CDT Mon May 20 2019 .Discussion... Issued at 408 PM CDT MON MAY 20 2019 An analysis of satellite, radar, and surface observations quickly reveal the amount of hazardous weather that is currently going through the plains right now. A deep shortwave trough with strong divergence aloft has quickly evolved a complex of storms and stratiform weather from the panhandle of TX up into eastern Kansas. It is likely we will see three potential periods of hazardous weather in the next 24-30 hours as follows: 1) Flood/Large Hail Threat: Moderate to heavy rain and lightning expected over the area now through the early morning timeframe which may create possible flooding, especially over the KC Metro and areas will saturated soils. Flash Flood Guidance (FFG) is currently 1hr/~1.5" 3hr/~2" 6hr/~2.5". The initial rainfall from these elevated showers will not be impressive, but as the warm front and associated MUCAPE lift north from western OK up into area area after sunset these rain rates will likely pick up to near 1-1.5"/hr in convection. The heaviest rain rates look to occur between 8pm and midnight. Due to FFG being so low it is possible that flash flooding could occur quickly, especially in northern Johnson Co KS that got over 2+" of rainfall Saturday. Local streams and creeks may also rise quickly as most of the rainfall will become runoff almost immediately and will need to be monitored overnight. Large hail could be possible down near Butler up through Sedalia as some MUCAPE will be realized in that area with plenty of shear available. The flood threat looks to decrease after midnight in the KC Metro area with light to moderate rainfall on the stratiform side of the MCS like feature that pushes east. This will then increase the threat over northern Missouri which will last through 3am. Areal flooding is likely in this region with standing water still around from Saturday. There is some uncertainty on how far north the boundary can get with the latest HRRR (18-19) indicating the MCS stalls in its NE track and start to follow the LLJ to the east sliding just south of what the previous runs show. This will be a very dynamic situation and when and where the MCS forms over OK will drive a lot of what happens in the future time frame. 2) Flash Flood Threat: The second round of potential flooding early Tuesday morning could be more of a flash flood threat with the first round this evening completely saturating the soils. This round also looks to be caused by strong isotropic accent as a strong LLJ forms ahead of the cold front along a secondary warm front that will be the main player for this threat and the last one this afternoon. Another 1-2" of precipitation is possible with this round of storms which would easily exceed any FFG by that point in morning and could cause a major issue with rush hour Tuesday morning with roads flooding throughout the KC Metro. People will need to use caution and remember to TURN AROUND DON`T DROWN. The upper level diffluence is very impressive during this time helping to add even more lift to the area during this timeframe. The uncertainty in this period will be how much the first wave this evening altered the overall synoptic pattern with the MCS development to see if this LLJ can reform back up ahead of the front and initiate this flash flood threat. 3) Damaging winds, Large Hail, additional Flooding, and Tornadoes: The third and final threat could be the most impactful depending on how things set up. The main feature that will drive the level of severe weather on Tuesday afternoon will be surface warm front. This feature will the delineation line for elevated and surface based storms. The latest 18z NAM/HRRR/GFS indicate this boundary will stall along out southern CWA boundary from Bates Co into the Lake of the Ozarks. The 12Z guidance had this boundary slightly higher up near HWY 50 so this trend will need to be monitored. Storms north of this boundary will have the primary threat of large hail and flooding, while storms south and along this boundary will have a primary threat of damaging winds and tornadoes. Focus on the warm sector shows a low level wind profile very favorable for QLCS tornado formation and if enough CAPE is realized maybe even embedded supercells along the line. 0-3km bulk shear vectors look to be about 40-50kts at around a 45 degree angle so this will also increase the mesovorticies and damaging wind possibilities as it pushes to the east. The threat will increase the further east (near SPC Enhanced Convective Outlook location) this feature goes with more time to recover and develop surface CAPE. The true nature of how this threat plays out may not really be known until after the morning activity passes through and a true analysis of that boundary is able to be conducted. River Flood Threat: All this QPF is going to have a potentially dangerous result on the Missouri River and tributaries. It is likely most places will get into moderate flooding and if all the QPF occur, or even more than forecasted, then major flooding is looking possible going into the end of the week. There will be a slight break in the constant rainfall Wednesday before a quasi-stationary boundary sets up over our area Thursday bringing rainfall chances back into the forecast through next week only adding to the flooding threat. && .Aviation...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 628 PM CDT MON MAY 20 2019 Multiple rounds of rain showers and thunderstorms are expected to persist through much of the forecast period. The two most significant rounds will arrive late Monday evening into the early overnight and then late Monday morning into the early afternoon. Strong wind gusts will accompany showers tonight up to 30 to 35 kts. This will minimize overall low-level wind shear impacts, though winds at 2kft may approach 50 kts at times during the early morning hours. Precipitation will come to an end during the late afternoon hours Tuesday. && .EAX WATCHES/WARNINGS/ADVISORIES... KS...Flash Flood Watch through Tuesday evening for KSZ025-057-060- 102>105. MO...Flash Flood Watch through Tuesday evening for MOZ001>007-011>016- 020>023-028>031-037-038-043-053. && $$ Discussion...Barham Aviation...Welsh
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
932 PM CDT Mon May 20 2019 .UPDATE... Winds continue 15 to 25 mph with gusts up to 35 this. The Wind Advisory will continue through the rest of the evening. Thunderstorms are slowly building to the east and south over West Texas. Short- range models show convection moving into the northern part of our CWA overnight. There is still a chance that some storms could be strong to severe over our northwest. Our forecast looks to be in good shape. && .PREV DISCUSSION... /ISSUED 643 PM CDT Mon May 20 2019/ UPDATE... See below for the 00z aviation discussion... AVIATION... Currently VFR and windy across the region, with southeasterly sustained winds on the order of 15 to 20 knots and gusts up to around 30 knots. These sustained winds and gusts are expected to continue through around midnight tonight, at which point wind speeds should come down just a little bit. However, still anticipate sustained winds on the order of around 15 knots with gusts up to around 25 knots at AUS/SAT overnight and into early Tuesday morning. Additionally, MVFR CIGs should develop around midnight tonight at AUS/SAT/SSF before improving once more to VFR by late Tuesday morning. Some guidance suggests the possibility of IFR CIGs developing briefly, especially at SAT, but elevated wind speeds should keep the low levels of the atmosphere mixed enough to keep CIGs at MVFR. A cold front will approach AUS/SAT/SSF from the west Tuesday morning, with a thin line of showers (and maybe a thunderstorm) along and ahead of it. There is some disagreement about how this will evolve, with the HRRR and the Texas Tech WRF suggesting the line decaying significantly as it approaches AUS/SAT/SSF. The NAM nest, however, shows a bit more robust of a line of showers moving through. For now, will continue to maintain VCTS at AUS and VCSH at SAT/SSF from 13z to 16z Tuesday morning. Following the frontal passage, winds will shift to west/northwesterly for the remainder of Tuesday morning and much of the afternoon hours. The cold front is then expected to retreat back to the northwest, shifting winds back to south/southeasterly at AUS/SAT/SSF by Tuesday evening. At DRT, VFR conditions are expected to prevail throughout the TAF period, with elevated southeasterly winds continuing through tonight. Winds should then shift to northwesterly by 12z Tuesday morning before returning once more to south/southeasterly by Tuesday evening. PREV DISCUSSION... /ISSUED 309 PM CDT Mon May 20 2019/ SHORT TERM (Tonight through Tuesday Night)... Latest water vapor images show an upper level low pressure system over the northwest part of the state of Arizona. An upper long-wave trough covers most of the Desert Southwest with winds of 120 to 130 knots (based on 300 MB height from the RAP model) approaching the base/axis of it according to latest RAP analysis. Models suggest for this type of forcing to move into the Southern and Central Plains while interacting with others surface features this afternoon into the evening hours to produce an outbreak of tornadoes and severe thunderstorms over those areas. For South Central Texas, isolated showers and thunderstorms are anticipated later this afternoon into the evening hours mainly across Val Verde County as some strong storms could develop ahead of a dry-line currently over west Texas. In the mean time, breezy to windy conditions continue across the area through early Tuesday morning as the low level jet strengthens and upper level winds mix down to the surface. A Wind Advisory is in effect across all of South Central Texas through 1 AM Tuesday. Later tonight into the overnight hours, the dry-line is forecast to slow down while moving to the east, however, a Pacific front is forecast to over take the dry-line. By this time (overnight period), a line of strong to severe thunderstorms is forecast to push across the southern Edwards Plateau. Main weather threats are damaging winds and large hail. Can`t ruled out an isolated tornado or two through the period. The line of strong to severe storms continues to move towards the east and over the Hill Country/I-35 corridor (including both Austin and San Antonio metro areas) mid-late Tuesday morning. The Storm Prediction Center Convective Severe Weather Outlook for Day Two (Tuesday) puts the area above mentioned under a marginal risk of severe thunderstorms. Main weather threats for this period are damaging winds and large hail. Can`t ruled out an isolated tornado across the far northern part of the Hill Country, where conditions are favorable. The line of storm/Pacific front continues to push to the east and exit the area on Tuesday afternoon. Tuesday evening into Wednesday morning should be a dry period. LONG TERM (Wednesday through Monday)... Another upper level trough moves across the northwest Pacific into the four corners region mid-week while an upper level ridge builds across the southern states. Upper level southwest winds aloft keeps slight chances for rain for some of our area Thursday through the weekend. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 72 87 69 89 74 / 30 60 0 10 10 Austin Bergstrom Intl Airport 72 87 69 90 74 / 20 50 0 10 10 New Braunfels Muni Airport 72 88 68 90 74 / 20 50 0 10 10 Burnet Muni Airport 69 84 65 87 71 / 40 50 0 10 - Del Rio Intl Airport 70 91 67 96 76 / 10 0 0 0 - Georgetown Muni Airport 71 85 67 89 73 / 30 60 0 10 - Hondo Muni Airport 71 90 69 95 75 / 30 20 0 0 - San Marcos Muni Airport 72 88 68 90 73 / 20 50 0 10 10 La Grange - Fayette Regional 75 88 73 91 75 / 10 50 - 10 0 San Antonio Intl Airport 72 89 70 91 74 / 30 30 0 10 10 Stinson Muni Airport 73 89 70 92 75 / 30 30 0 0 - && .EWX WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 1 AM CDT Tuesday for Atascosa-Bandera-Bastrop- Bexar-Blanco-Burnet-Caldwell-Comal-De Witt-Dimmit-Edwards-Fayette- Frio-Gillespie-Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Kinney- Lavaca-Lee-Llano-Maverick-Medina-Real-Travis-Uvalde-Val Verde- Williamson-Wilson-Zavala. && $$ Aviation...Runyen/04 Short-Term/Long-Term...05
Area Forecast Discussion
National Weather Service Little Rock AR
732 PM CDT Mon May 20 2019 .AVIATION...21/00Z TAF CYCLE Sctd elevated convection wl affect mainly N AR this evening, with maybe a few storms possible elsewhere. Expect VFR conds to prevail thru the early mrng hrs, followed by low clouds/MVFR CIGS forming once again like today. Main chances for organized storms wl occur ovr WRN AR late Tue aftn ahead of the CDFNT, with other locations affected aft this fcst PD. Breezy S/SE winds wl cont as well. /44/ && .PREV DISCUSSION...(ISSUED 241 PM CDT Mon May 20 2019) Short Term...Tonight thru Wednesday... Trof over the swrn US is swinging toward the southern Plains this afternoon, and will acquire a negative tilt as it swings into the region tomorrow. While all eyes are on the instability and high risk area over TX/OK, a good portion of AR remains in a slight risk this evening, with an enhanced risk covering the far western portions of the state. Low level moisture levels are quite abundant across AR, and maximum CAPE values this afternoon are likely in the 1500-2000 j/kg range. Most of the short term model runs have been showing some showers and thunderstorms developing over the southwestern quarter of the state this evening, which is now in progress. Of particular concern is several HRRR model runs that have been developing some supercell- looking storms across the swrn portions of the state and moving those northward during the evening hours, although the latest run seem to be backing off on that a bit. In any event, BRN values are a bit high for supercell development across the southern half of the state this evening, so I am hedging my bets on this being more multicellular in nature this evening. At some point overnight the line of severe storms across OK will start to push into the nwrn portions of AR, and into the local CWA shortly thereafter. Outflow boundaries from the main line will likely race ahead and trigger some development overnight across the northern portions of the state. By tomorrow things get a bit more interesting. As daytime heating progresses and the line advances deeper into the state, a jet max will rotate around the negatively tilted upper low. In the morning the state will be under the right exit region, which may put a lid on deeper convection. By late afternoon into the evening, the area will start to come under the right entrance region, and combined with the destabilization effects of daytime heating, will make for better chances for severe convection, especially across the northern and northeastern portions of the forecast area. Long Term...Wednesday Night thru Monday... The long term portion of the forecast will be much quieter in terms of weather than what is going on across the region today and Tuesday. A summer-like pattern will be in place through the duration with H500 ridging setting up over the southeast US/Gulf of Mexico. At the surface, with ridging holding tight to the east, southerly winds will remain in place and Td values will be in the 65-70F range. To the north and west of the state, fairly active weather will persist but precip chances will likely remain just outside the forecast area. If the ridge were to contract a bit, northern and western portions of the state would be most prone to seeing chances for rain and thunderstorms. This could begin to occur near the end of the period. Given that it is still May and ground moisture levels remain high, daily max T values shouldn`t get too out of hand. Highs will likely approach or barely exceed 90F across the southeast half of the state on a near daily basis. && .LZK Watches/Warnings/Advisories...NONE. && $$
Area Forecast Discussion...Updated
National Weather Service Pendleton OR
444 PM PDT Mon May 20 2019 Updated aviation discussion .SHORT TERM...Tonight through Thursday. The forecast area is currently located between two low pressure centers--one about 250 miles west of Astoria moving toward the OR Coast and another over northern AZ. The strong low over AZ is circulating showers over southeast OR as far north as Joseph. Showers are increasing west of the Cascades ahead of the offshore. By 5 PM, showers will develop along the east slopes of the WA/OR Cascades and across Deschutes County. Thunderstorms were removed from the forecast for central OR and far northeast OR due to the thick overcast clouds limiting instability. The HRRR lacks increasing return in the Composite Reflectivity progs. By 10 PM, numerous showers will develop across central and northeast OR and south central WA. Although the Lower Columbia Basin will only have a slight chance of showers tonight, showers will likely develop just around sunrise on Tuesday. Nearly all of the forecast area will have a chance of showers on Tuesday. Snow levels will lower to around 5500-6000 feet, so the higher elevations will have snow accumulations around 1-3 inches. From 5 PM today to 5 PM Tuesday, rainfall amounts of 0.10-0.25 inch can be expected across the Columbia Basin down to the Columbia Deschutes Plateau with 0.25-0.5 inch for the east slopes of the WA Cascades as well as the Blue Mountains and the John Day Basin east to the Idaho border. As the low dives south into the Great Basin Tuesday night, precipitation will taper off from the north with only low chance PoPs in the forecast for the southern half of Oregon after midnight. Wednesday is looking to be relatively cool with highs in the 60s mountains and 60s to lower 70s elsewhere (mid 70s for portions of the Columbia Basin. Scattered showers can be expected over central and northeast Oregon and partly to mostly cloudy elsewhere. Winds from the north both surface and aloft will increase and become breezy, especially along ridgetops and southeast Oregon where a tight pressure gradient will be present. Thursday will be partly to mostly cloudy with isolated showers and locally breezy winds. The synoptic pattern is quite interesting on Wednesday with one low centered over the Great Basin and another over the Dakotas pinwheeling around each other. This leaves the Pacific NW under a drier northeast flow aloft Wednesday through Thursday, but a continued cyclonic flow. Wister .LONG TERM...Thursday night through Tuesday...Long term period will continue to see the persistent pattern of long wave troughing over the western US with ridging over the east. General model trend shows upper-level low over the intermountain west lifting northeast into the Northern Plains Thursday night into Friday. Another upper-level low expected to replace it, dropping south out of BC over the PacNW and down over CA/NV around Friday/Saturday and slowly work eastward Sunday/Monday. Expect the potential for showers each day, especially over the mountains, with the best potential Friday through Sunday due to the likely proximity of the upper-level low to the area. Enough instability could be in place for a few thunderstorms as well, mainly Friday and Saturday. Models diverge quite a bit past the weekend, but may see some ridging trying to build in behind the departing upper-level low that could bring warmer and drier weather. Winds will generally be light during through the extended period, with breezy winds possible with passing weather systems, especially in the Columbia Basin/Gorge, but nothing significant expected as of now. Temperatures remain near to slightly below normal through Saturday and then a warming trend takes place Sunday through Tuesday with temperatures rising into the 80s in the lower elevations and 60s to lower 70s mountains. && .AVIATION...00Z TAFs...Showers over the Cascades, Blues/Wallowas into Central OR this afternoon will expand into the Columbia Basin overnight into tomorrow morning. Widespread mid-level cloudiness expected as well. VFR conditions will dominate, although brief MVFR vis/cigs possible under heavier showers. Winds generally under 12 kts, but could see 10-20 kts the eastern Columbia River Gorge near DLS through early evening and again tomorrow afternoon. Perry && && .PRELIMINARY POINT TEMPS/POPS... PDT 48 62 47 70 / 50 60 20 10 ALW 49 65 48 74 / 50 70 10 10 PSC 53 69 51 79 / 20 60 10 0 YKM 51 68 51 77 / 30 60 10 0 HRI 50 66 49 76 / 30 60 10 0 ELN 47 67 48 72 / 40 50 10 10 RDM 37 60 41 67 / 60 50 40 20 LGD 43 57 44 65 / 90 80 30 20 GCD 41 55 43 62 / 90 70 40 30 DLS 49 67 51 76 / 50 40 10 10 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ 85/84/83
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tuesday) Issued at 331 PM CDT Mon May 20 2019 No question that the most important forecast challenge for tonight is just how much rain will fall and where. The severe weather threat, while non-zero, is clearly greater to the south of county warning area. Very strong trough in the desert southwest just starting to turn to the northeast as wind speed maximum evident in water vapor imagery ejecting northeast through New Mexico. Evidence of the strength of the trough can be seen in many different ways. NAM shows, for example, a substantial mid-level stratospheric intrusion over central Kansas by Tuesday afternoon with an area in excess of 10 potential vorticity units down to 300 mb. With that degree of forcing, a nearly moist adiabatic sounding for tonight, and little to inhibit convection, rain and thunderstorms will be widespread and most convective elements will struggle to become discrete. Effective surface boundary will likely end up staying to the southeast of the area tonight, limiting severe potential to areas primarily southeast of Interstate 35. Greatest precip totals tonight are expected to be found along and southeast of Interstate 35 where an average of 2 to 3 inches seems most likely, with locally heavier amounts. If surface boundary is able to progress more northward, higher totals that NAM is showing might occur, but believe HRRR output is more realistic. Totals further to the northwest, especially along the Nebraska border should be the lightest, but will still probably average 1 to 1.5 inches. Confidence in flooding risk is lower there, but given antecedent conditions and steady moderate rainfall occurring there this afternoon, it seems prudent to maintain flash flood watch for entire area. Biggest question for Tuesday is probably how much airmass recovery can take place after overnight/early morning convective complex rolls through. Deepest moisture will be pushed off to the east, but very cold mid-level temperatures will lead to steep lapse rates and even with surface dewpoints in the mid/upper 50s, moderate instability with CAPE values 1000-1500 J/kg could be reached. SPC Day 2 outlook has this scenario well covered. Although QPF amounts will be lighter (and coverage less widespread) during afternoon, any additional heavy rainfall from stronger cells could lead to localized flooding risks. .LONG TERM...(Tuesday night through Monday) Issued at 331 PM CDT Mon May 20 2019 On Wednesday, broad southwesterly flow aloft will be in place over much of the Central and Southern Plains with an attendant surface low located across the High Plains. Models are showing a strengthening low-level jet Wednesday night which will help to bring a warm front across the forecast area by Thursday morning. Thunderstorms are possible along and north of the warm front Wednesday night into Thursday. MUCAPE near 2000 J/kg and effective shear ~30 kt could pose a large hail threat. Throughout the end of the week and into the weekend, midlevel perturbations within southwesterly flow will traverse the area with multiple rounds of showers. With that being said, the potential for flooding is a possibility given the current state of area rivers and lakes. However, confidence in intensity, coverage, and timing are limited at this time. Temperature trends for the long term are expected to remain near normal with highs near 80 and lows in the 60s. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 632 PM CDT Mon May 20 2019 High end IFR to MVFR stratus continue underneath the shield of SHRA with occasional lightning over KMHK/KTOP/KFOE. Current forecast trends show the potential for reprieve from rainfall after 06Z and therefore bumped ceilings to MVFR before the next round of scattered TSRA arrives in the 08-10Z time frame. A strong 55 kt low level jet below 2 kft could translate down to the sfc with wind gusts in excess of 40 kts possible aft 04Z. As the sfc low lifts into eastern Kansas, additional TSRA is expected in the early afternoon with best chances towards KTOP/KFOE. VFR returns thereafter towards the end of the forecast period. && .TOP WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Tuesday evening for KSZ008>012-020>024- 026-034>040-054>056-058-059. && $$ SHORT TERM...Manion LONG TERM...Bunker/Skow AVIATION...Prieto