Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/16/20

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
246 PM AKST Wed Jan 15 2020 .SHORT TERM...While the cold continues across Southeast Alaska today, actual temperatures have warmed slightly across many parts of the area, mainly due to greater mixing of the lower boundary layer. Estimated from MDCRS soundings, some parts of the region had a very low inversion of 300 feet, which mixed out around midday leading to some sharper temperature rises. However, with wind comes wind chills; thus it was still unpleasant for many Southeast Alaskans to be outdoors for long. The wind chill warning for White Pass still runs into tomorrow morning. If one calls 50 below wind chill a break, anyone venturing outside on the high point of the Klondike Highway today experienced one. Despite the respite, we leave the warning in place as we expect both winds to rise and temperatures to fall overnight. In fact, the warning may need to be extended into early afternoon Thursday, but we will take a second look Thursday morning before being absolutely certain. Gusty high winds in Juneau continue as weak cold air advection from Canada continues through our mountain passes. Cross barrier flow, while not extraordinary as estimated by the models should strengthen tonight. All high res models are supporting a sharp rise in wind gusts late tonight into Thursday morning. Therefore, the gusts to 85 mph for Downtown Juneau and Douglas still seem reasonable. In fact, as the gradient responds to a low pressing up the BC Coast from the south, we should see the tightening gradient even further. Now heading into the weekend, a new front looks to form out in the North Pacific. We have gale force easterlies building over the gulf. This should support another period of potentially high winds for Downtown Juneau late Friday into at least Saturday night. To prepare for this, we have dried out conditions by reducing pop markedly for the northern Panhandle during this time, in line with temperatures still well below normal. But we have also begun warming temperatures a bit earlier on Sunday as we allow the precipitation bands to climb north. Thus, late Saturday night into Sunday, we are looking for possibly significant snow potential for the southern Panhandle but much lighter snow for the north. Lastly, we did nudge upward temperatures for the next 30 hours over the Inner Channels using the HRRR which seems to be performing far better than the NBM`s disappointing cold bias. We still left the heavy freezing spray for Sumner Strait late tonight into tomorrow morning, as Stikine River outflow may be pretty impressive overnight, and temperatures in Wrangell are indeed quite cold in the middle teens. .LONG TERM...Change is still in the works for the next week as the cold dry weather starts gives in to warming temperatures and rain creeping into the forecast, perhaps even for some locations in the northern Panhandle. Forecast confidence past the weekend is still suffering from what the upstream upper level features will do, but the overall message is a gradual warm up with southerly onshore flow. Forecast confidence is moderate favoring the WPC and NBM for updates. && .AJK Watches/Warnings/Advisories... PUBLIC...High Wind Warning until 9 PM AKST Thursday for AKZ025. Strong Wind from late tonight through Thursday morning for AKZ022. Strong Wind through Thursday morning for AKZ021. Strong Wind through Thursday afternoon for AKZ019. Wind Chill Advisory from 9 PM this evening to noon AKST Thursday for AKZ019. Wind Chill Warning until 10 AM AKST Thursday for AKZ018. Strong Wind through late tonight for AKZ018. MARINE...Heavy Freezing Spray Warning for PKZ011-031. Heavy Freezing Spray Warning for PKZ011. Heavy Freezing Spray Warning for PKZ011. Heavy Freezing Spray Warning for PKZ011. Heavy Freezing Spray Warning for PKZ013. Heavy Freezing Spray Warning for PKZ031. Heavy Freezing Spray Warning for PKZ012. Heavy Freezing Spray Warning for PKZ035. Storm Warning for PKZ012. Gale Warning for PKZ013-021-022-031-043-051. Small Craft Advisory for PKZ011-032>036-041-042-052-053. && $$ JWA/EAL Visit us at
Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
804 PM CST Wed Jan 15 2020 .UPDATE... Based on some 18Z models, the HRRR, TT WRF we have extended the advisory to fill in the WRN counties. This also matches the ABQ advisory better. NAM, HRRR and TTU WRF show a band of snow and possibly sleet impacting the far west tomorrow morning. In fact some suggest around 1" or slightly more snow south of DHT, which may be overdone given we have to overcome the dry air near the SFC initially, but it is certainly noteworthy. Given this have mentioned more sleet and snow potential initially with the new counties (Deaf Smith, Oldham, Hartley) but still expect the transition to sleet. That said, still seeing a huge range in model temperatures in the aftn with the HRRR and ECM suggesting a break in precip and a big temp recovery to near 40 and possibly a struggle to reach freezing again from there, while the GFS TT WRF and NAM keep us wet bulbed down below freezing all day and even suggest temps in the upper 20s for some which would be concerning for greater ice potential. No reason to argue with a blend/middle of the road approach which is basically what the current forecast is and see no reason for more changes attm. && .PREV DISCUSSION... /Issued 559 PM CST Wed Jan 15 2020/ AVIATION... Precipitation will begin spreading north across the area in the morning hours. Coverage will be more patchy initially but will increase to widespread in the afternoon and evening. Freezing rain is expected to be the dominant precipitation type, although can`t rule out brief period of snow or sleet to start things off in DHT and perhaps GUY. Icing on planes on the runway will be the main concern for the TAF sites as elevated surfaces will see greater accumulation. Believe temps may not get cold enough for significant icing on bare ground and runways (esp if treated), but stay tuned on that. CIGs will also fall through the day and should reach MVFR levels in the AFTN. IFR to VLIFR CIGs appear likely near or just after 00z Friday and visibilities will also drop in the evening hours. There is a chance these occur before 00Z but this is not indicated in current TAF package. PREV DISCUSSION... /Issued 311 PM CST Wed Jan 15 2020/ SHORT TERM...Today through Friday... A developing winter system is expected to move from southwest to northeast across the Panhandles starting mid morning Thursday and continuing through Friday morning. The potential is there for impacts due to freezing rain, especially Thursday afternoon through Thursday night. As we go into the morning hours on Thursday, a broad H500 trough will move east across northern Mexico in-conjunction with a broad H500 anti-cyclonic feature shifting west across the western Gulf of Mexico. This will result in mid level flow which will funnel right into the Panhandles from SW to NE. Closer to the surface, good H850-800 east to southeasterly flow with upslope across the high terrain to the west, pronounced H850-700 isentropic lift, and lift downstream of the trough axis itself across northern Mexico will help to spread precipitation across the region. Latest 15/12Z model and numerical guidance continues to moisten the lowest 1kft-1.5kft AGL sooner than previous model data runs. This should help start precipitation across the southern TX Panhandle as early as 12Z and spread north through the morning hours. Dry air aloft is expected, especially across the northern areas which may delay the onset of precipitation. However, precipitation by late Thursday morning into early Thursday afternoon is expected across all of the Panhandles. As a result, wet bulbing will be critical for precipitation type with freezing rain expected to be the main precipitation type by Thursday afternoon through Thursday night. As the main 700 hPa theta-e advection continues, this will be the main catalyst for persistent WAA and lift for precipitation through the overnight Thursday into Friday morning. Precipitation rates will likely be the greatest the second half of Thursday as the main trough continues to move into the Panhandles and provide the main lift downstream of the axis across the region. Eventually, the WAA should erode the sub freezing airmass across the lowest levels of the ATM. As the main trough exits the Panhandles to the east on Friday morning, precipitation should be in the form of rainfall as temperatures will continue to rise on Friday with high temperatures into the upper 50s to lower 60s. The main precipitation type throughout the event on Thursday into Thursday will be freezing rain with rain at times that could be mixed in. The sfc based depth of cold air is still the tricky aspect of the forecast. As of this current forecast, current ice accretion amounts by Friday morning will range from a few hundreths of an inch across the west to a tenth on an inch or locally higher amounts across the east where the highest probs of measurable QPF will exist along with duration of the precipitation. Impacts, especially on elevated surface with ice accretion are of greatest concern with elevated roadways and powerlines that may be impacted. If colder air is entrenched, especially off the caprock, surface based ice accretion after sunset on Thursday may occur and could impact travel. High temperatures for Thursday will struggle to get out of the 30s. Meccariello LONG TERM...Friday night through Tuesday... Upper level storm system will move away from the Panhandles by Friday night. Lows Friday night will fall into the 20`s and lower 30`s under mostly clear skies. The flow aloft will remain fairly zonal and progressive through the weekend. This flow will keep the Panhandles near normal for temperatures. Any systems should stay well to the north of the Panhandles as well. A couple a cold fronts, one Friday night and another early Monday will come through dry. An upper level ridge will move across the Panhandles on Tuesday, so this along with stronger downslope winds should help to push temperatures upward. && .AMA Watches/Warnings/Advisories... TX...Winter Weather Advisory from 9 AM Thursday to 6 AM CST Friday for the following zones: Armstrong...Carson... Collingsworth...Deaf Smith...Donley...Gray...Hansford... Hartley...Hemphill...Hutchinson...Lipscomb...Moore... Ochiltree...Oldham...Palo Duro Canyon...Potter...Randall... Roberts...Sherman...Wheeler. OK...Winter Weather Advisory from 9 AM Thursday to 6 AM CST Friday for the following zones: Beaver...Texas. && $$ 88/88
Area Forecast Discussion
National Weather Service Gaylord MI
915 PM EST Wed Jan 15 2020 .UPDATE... Issued at 915 PM EST Wed Jan 15 2020 Low pressure center has shifted SE of Lower Michigan late this evening...with a weak frontal boundary holding along the southern border of our CWA. Broken area of light synoptic snow continues to stream thru portions of our CWA...with the most persistent snowfall occurring over the Straits area where vsbys have fallen to around 1SM with light snow. Some light drizzle/freezing drizzle is mixing in with the light snow from time to time...but this mix should come to an end soon as CAA begins to activate the lakes as we head into the overnight hours. Winds have already begun to shift to the NW across much of our CWA. Latest RAP drops 850 mb temps into the negative teens overnight...and with the moist layer extending thru 700 mb thru the night...conditions will become increasingly favorable for lake snow shower production. Will certainly keep all headlines in tact for the typical snowbelt areas of NW/North Central Lower Michigan tonight thru Thursday with the expectation of 3 to 5 inches of new snow within these areas. Rest of our CWA will see generally 1 to 2 inches of new snow. CAA will drop overnight lows into the teens to lower 20s. && .NEAR TERM...(Through Tonight) Issued at 401 PM EST Wed Jan 15 2020 High Impact Weather Potential: Moderate ...Accumulating snow this evening and overnight, followed by lake effect. Gusty winds could create areas of blowing and drifting snow... A weak PV-anomaly continues to slide through the upper Mississippi valley this afternoon, supporting a weak surface low just south of Chicago. Some broad weak lift out ahead of the shortwave/PV-anomaly (along with WAA east of this surface low) have continued to produce snow showers, mainly in northern Wisconsin and Minnesota. This area of snow have been struggling to fill in...but it is fighting dry air near 850mb (residual from this mornings sounding). Radar echos have been fairly prevalent across the area, but nothing has started to reach the ground yet in our CWA. Farther to the south in downstate Michigan, an area of rain has broken out, with temperatures in the mid-30s. Precipitation is still expected to fill in between these two as better lift and a corridor of mid-level moisture overspreads our area as we head into the early evening. Snow continues overnight, likely heaviest between midnight and 6am. Slightly wetter snow this evening transitions to increasingly drier and fluffier lake effect through the overnight hours. Overlake instability should reach about 15 C, with decent omega within the DGZ. Inversion heights rise through the night, from about 4 - 5 kft early overnight to 5 or 6 kft in the wee hours of the morning. Total snowfall amounts between late this afternoon through early tomorrow morning are expected to be between 2 and 4 inches. More snow expected Thursday in the typical northwest flow belts. && .SHORT TERM...(Thursday through Saturday) Issued at 401 PM EST Wed Jan 15 2020 High Impact Weather Potential: Lake snow showers continue into Thursday...then potential for more widespread synoptic snow (and maybe rain?) Saturday. Pattern Synopsis/Forecast: Large scale pattern features shows a strongly -PNA trough over the eastern Pacific...with generally zonal flow across the CONUS. Strong storm system off the Pacific Northwest coast...with a weaker short wave trough heading into the upper Great Lakes this afternoon (and an even weaker trailing wave back across the western Dakotas). Polar jet axis cuts right across the Great Lakes...subtropical jet axis has lifted north into Kansas/ Missouri and extending east into the Ohio Valley. Passage of upstream short wave trough Thursday will be followed by strong height rises for the end of the week as ridge axis crosses Michigan Friday. But another piece of energy gets "slingshotted" out of the eastern Pacific long wave trough Friday and quickly moves into the midwest Saturday. This short wave trough will provide the bulk of the forecast issues for the short term portion of the forecast. A couple of surface waves associated with both jet axes upstream of Michigan this over northwest Wisconsin associated with aforementioned short wave trough axis...a second broader area of low pressure over Missouri/Illinois. Strong low level cold advection behind the Wisconsin surface low...with subzero early afternoon cold over the Dakotas/eastern Montana. 1047+mb Arctic high settles into the upper Midwest during the day Thursday with cold advection/lake aggregate troughing lying across Michigan. Pressures then rise across Michigan as surface high splits around the upper Lakes as winter anticyclones are wont to do. As high moves east of Michigan by Friday evening warm advection will commence as next system takes a run at Lower Michigan Saturday. Primary Forecast Concerns: Cold northwest flow across the upper Great Lakes expected to set up northwest flow lake induced convection off the surrounding lakes. 850mb temperatures dropping toward -15C over Lakes Huron/Michigan...and -20C over Lake Superior will result in plenty of instability...and passage of weak trailing short wave trough during the morning won`t hurt the cause though any window for seeder-feeder potential appears to be short-lived. But inversion heights not bad up around 750-800mb and inversion top temperatures in the -20C vicinity (a little colder off Lake Superior). Better accumulation potential looks to be around and east of Grand Traverse Bay in northwest Lower benefitting from a two- lake effective fetch...with a couple inches during the day with some uncertainty regarding how persistent banding will be over a given area. Snow showers will continue into Thursday evening but with increasing subsidence and weakening winds as high pressure builds into the upper Lakes should allow this activity to wind down. Attention then turns to snow potential for weekend system. Storm track for the time being cuts right across Lower Michigan...some question about potential for dry slotting wrapping around the east side of this system and getting into Lower Michigan for a time well as given the storm track the possibility of a surface based warm layer allowing precipitation to change over to rain for a time along the southern periphery of the storm track. Probabilistic guidance of 24h snowfall greater than 6 inches ending 12z Sunday is split between the GEFS (greatest probabilities over northern Michigan with potential for rain along/south of M-55 Saturday) and the ECMWF ensemble (greatest probabilities south of the M-55 corridor where higher QPF potential is in the ensemble). Will continue to message the potential without getting bogged down in the details for the time being...still a number of questions to be answered. The potential for at least advisory criteria snowfall to occur appears to be pretty decent...whether we can go above that is still uncertain. .LONG TERM...(Saturday night through Wednesday) Issued at 401 PM EST Wed Jan 15 2020 Split flow ridging forecast to set up over western Canada extending well north of the Arctic circle...which will allow an Arctic branch of the jet to dive southward and into the upper Midwest/Great Lakes to start next week. There is disagreement on degree of focus temporally of cold air "firehose"...but will allow temperatures to moderate heading into midweek. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 600 PM EST Wed Jan 15 2020 Widespread light snow will develop across Northern Michigan this evening as a short wave slides thru the region. Colder air will arrive overnight into Thursday behind this short wave. Widespread synoptic snow will transition to NW flow lake effect snow showers...targeting our typical snowbelt areas for the most persistent snow showers thru Thursday. Expect mainly MVFR conditions tonight thru Thursday night...with some areas periodically dropping to IFR within some of the heavier snow showers. Winds will shift to the NW tonight and strengthen to 15 to 25 kts early Thursday...with some higher gusts expected. && .MARINE... Issued at 401 PM EST Wed Jan 15 2020 Small Craft Advisories will be expanded tonight into most nearshore zones...which will continue into Thursday evening before pressure gradient flattens as high pressure builds in. Another round of Small Craft Advisories appear to be likely Friday night into Saturday. && .APX WATCHES/WARNINGS/ADVISORIES... MI...WINTER WEATHER ADVISORY until 7 PM EST Thursday for MIZ021-022- 027-028-099. LH...SMALL CRAFT ADVISORY from 4 AM to 11 PM EST Thursday for LHZ346>349. LM...SMALL CRAFT ADVISORY from 4 AM to 7 PM EST Thursday for LMZ323- 341-342. SMALL CRAFT ADVISORY until 11 PM EST Thursday for LMZ344>346. LS...SMALL CRAFT ADVISORY until 11 PM EST Thursday for LSZ321. && $$ UPDATE...MR NEAR TERM...STJ SHORT TERM...JPB LONG TERM...JPB AVIATION...MR MARINE...JPB
Area Forecast Discussion
National Weather Service Denver/Boulder CO
814 PM MST Wed Jan 15 2020 .UPDATE... Issued at 809 PM MST Wed Jan 15 2020 Will see some increase in high level clouds overnight otherwise no changes needed to previous fcst. && .SHORT TERM...(This evening through Thursday) Issued at 254 PM MST Wed Jan 15 2020 500 mb height are rising over Colorado as upper ridging builds up from the south. West-southwesterly flow aloft will be turning more southwesterly overnight, with good warm advection spreading across the area. Clear skies overnight will allow for good radiational cooling over the high mountain valleys as their airmass decouples and winds calm. Pressure gradients will be increasing over the plains as a lee trough deepens along the urban corridor and high pressure pushes in from the Great Plains. This will cause southerly winds across the eastern plains as well as the Palmer Divide to remain breezy with speeds of 10 to 20 mph sustained, with gusts to 30 possible. Moisture will increase from the south Thursday with thickening high clouds through the morning. Temperatures will be about 10 degrees warmer over the mountains due to the warm advection. Over the plains, the high surface pressure system over the Great Plains will push cooler air into the east plains. The deepening surface trough will continue to produce a Denver Cyclone, which may pull in the cooler air into the northern urban corridor, while the southwest flow flowing over the southern foothills and Palmer Divide will bring warmer air downsloping in. Therefore the high temperature forecast is challenging for tomorrow, as it will depend on the location of the circulation center. Have decreased temperatures over the eastern and northern plains for now. It will be tough along the northern foothills where the westerly warmer downslope winds will meet the cooler easterly winds. Weather will remain dry over the forecast area through the afternoon as most of the moisture will still be south of the area, however the one exception may be Lincoln County. Some low level moisture may move in to bring some drizzle, but low confidence in it reaching this far north, so did not include it in the forecast. Some model guidance has it much cooler as well, with a high in the mid to upper 30s. Currently think the southerly flow off the Palmer Ridge should have a warming effect, however the far southern end of the county would be on the "upslope" side of the ridge. If this is the case, may need to look into the possibility of freezing drizzle. But again, low confidence on this event, so not including it in the forecast at this time. .LONG TERM...(Thursday night through Wednesday) Issued at 254 PM MST Wed Jan 15 2020 ...Main concern for this period will be potential for high winds across the Front Range and all of the plains late Friday into Friday night...and accumulating snow/blowing snow in the mountains. Southwest flow aloft will strengthen across the forecast area Thursday night, but we`ll remain in between moisture streams (one extending northeast from New Mexico into Kansas, and the other ahead of the next system dropping in across the Great Basin). By Friday, weather conditions will change fairly quickly with the onset of snowfall in the mountains, and a blast of winds across the Front Range and Plains. Snow will first develop in the high country during the morning hours with increasing QG lift and moisture ahead of the trough moving across the Great Basin and into Colorado. The initial southwest flow may limit snowfall early in this event, but we do expect a sharp uptick in snowfall rates with the mid level cold front, switch to west/northwest flow, and high mid level lapse rates of 7-8 C/km. Travel will likely become hazardous by Friday afternoon along the I-70 Mountain Corridor, with a brief period of very poor visibility due to a burst of heavy snow and blowing snow along the front. Then, snow will taper off rather quickly Friday evening with large scale subsidence and drying. Overall, initial indications are for snowfall of 3-8 inches in the high country. The cold front will push across the Front Range late in the day with a blast of downslope wind. At this time, it`s most likely arrival time would be mid to late afternoon. The airmass should be adequately mixed, there`s strong downward QG forcing, and the low/mid level pressure gradients are high. The local wind forecast program suggests we`ll be reaching high wind criteria due to the gradient alone. We`ll probably need a high wind watch with the next forecast package issuance, and will do so in collaboration with our neighboring offices. There is still some uncertainty to the exact center of downward forcing, but if that moves across the Front Range we could easily be looking at gusts to 75 mph or greater in/near the foothills and 60 mph or more across the adjacent plains late Friday afternoon through Friday evening. By Saturday, we`ll see flat ridging build across and surface high pressure sliding southeast through the Central Plains. That should allow winds to decrease in all but the northeast corner of the state. Dry conditions will prevail, although a bit of lingering mid level moisture could keep a few flurries over the mountain ridges. Little change is expected Sunday. Temperatures will average closer to normal for the weekend. By Monday, a pretty sharp ridge is advertised to pop across the Central Rockies. This will bring warmer and a continuation of dry weather. The next short wave will likely arrive by Tuesday with another toward Wednesday. This would bring a return of snow showers to the mountains, but mostly dry conditions still prevailing on the plains with downslope flow. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 809 PM MST Wed Jan 15 2020 Winds have become southerly early this evening and should remain so overnight. Towards 12z, the HRRR has them going light westerly while the RAP keeps them southerly. For now will keep them from the south. && .FIRE WEATHER... Issued at 254 PM MST Wed Jan 15 2020 Strong southerly winds will blow across the eastern plains tonight and into tomorrow, with gusts of 35 to 45 mph possible. The strongest winds will be found along I-70 east of Denver. Cooler temperatures are expected now for tomorrow however, so humidities should only get into the mid 20s. Drier humidities will be found over the southern foothills and north of the Palmer Divide, where wind gusts should be less than 20 mph. Fire danger will be elevated across the foothills and plains Friday afternoon through Friday night due to increasing winds. Sustained speeds of 25-40 mph will be possible with gusts in excess of 60 mph. While humidity will be increasing behind the cold front responsible for the winds, the dry grasses will certainly be capable of carrying fire spread given the strength of winds. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...RPK SHORT TERM...Kriederman LONG TERM...Barjenbruch AVIATION...RPK FIRE WEATHER...Kriederman/Barjenbruch
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
934 PM CST Wed Jan 15 2020 .UPDATE... Issued at 927 PM CST Wed Jan 15 2020 Made a few changes to the remainder of tonight and into early Thursday morning with clouds and temps. Stratus has been slower to clear than previously thought. Using a combination of extrapolation trends from GOES-East Nighttime Microphysics RGB and the RAP 950 mb RH progs, the main thrust of clearing will be along the spine of the MS River and a good 3-4 hours slower. Temperatures are also quite cold upstream attendant with the large Arctic surface high. Despite more clouds tonight, pure cold advection would argue for slightly colder overnight and early morning temps. Glass && .SHORT TERM... (Through Late Thursday Afternoon) Issued at 255 PM CST Wed Jan 15 2020 Early this afternoon, a flat zonal flow prevailed across much of the CONUS. A fairly strong upper level disturbance was to our north in southeast Minnesota, while a strong storm system was located just offshore from the Pacific Northwest states of Oregon and Washington. At the surface, an area of low pressure was over northwest Indiana with a trailing cold front through central Illinois, the Saint Louis Metro area, and into south-central Missouri. A rather stout 1043mb area of high pressure was the airmass building in behind this front with an even more impressive 1050mb Arctic high pressure behind this. Skies were nearly cloudy areawide with a few breaks starting to show, but a more definitive clearing of clouds does not occur until eastern Nebraska and far northwest Iowa. Temperatures were quite mild ahead of the front, with mid to upper 50s widespread, and temperatures dropping into the lower 40s in northeast Missouri where strong CAA began in earnest. The regional radar mosaic was largely devoid of echo, except in Wisconsin ahead of the upper level disturbance. The cold front will complete its trek through the forecast area before sunset, with the strong CAA occurring a couple hours after accompanied by gusty northwest to north winds. Any breaks in clouds should fill back in again this evening with clouds finally clearing out later tonight. The Arctic airmass is expected to quickly overtake the leading Polar airmass late tonight, building into the Upper Midwest as a 1048mb area of high pressure by sunrise Thursday morning. This is expected to result in temperatures dropping into the teens for areas north of I-70, and into the low-mid 20s elsewhere. The strong storm system will come onshore into northern California on Thursday, resulting in development of an upper RIDGE in the central CONUS. Look for a dry, yet cold, day across the forecast area with the Arctic high pressure in control from the north and filtered sunshine from abundant high cirrus clouds. Either way, it will be MUCH different, as we go from daytime temps 15-20 degrees above normal today to temps 5 degrees below normal this day. TES .LONG TERM... (Thursday Night through Next Wednesday) Issued at 255 PM CST Wed Jan 15 2020 (Thursday Night - Saturday) Strong Canadian high pressure Thursday evening is expected to be located across the Upper Mississippi Valley helping to bring seasonably cold and dry conditions to the area. This high will slide eastward through the period, with surface winds veering slowly from the northeast to the east/southeast by Friday. By late Thursday night/early Friday morning, still expecting precipitation to begin across central Missouri due to increasing low-level warm/moist advection, vorticity advection, and diffluent flow aloft. There is still some uncertainty with the onset of precipitation with different arrival times of these aforementioned forcing mechanisms as well as how fast the very dry low/midlevels of the troposphere become saturated. For now, continued to lean toward the faster guidance (i.e., the NAM/NMM-East) as warm-air advection precipitation events are notorious for beginning about three hours faster than model consensus at this forecast timeframe. Precipitation should overspread the rest of the area from the west/southwest through the morning/early afternoon hours. Precipitation is still expected to begin as snow as the atmosphere saturates/wetbulbs. However, there is now more model agreement depicting a faster transition to sleet, and then freezing rain shortly thereafter. In addition, cooled surface temperatures several degrees through the early evening hours on Friday, which is more in line with the raw NAM/GFS output. The combination of this faster transition to freezing rain and cooler surface temperatures has led to an increase in ice amounts compared to the previous shift. Widespread amounts of 0.10-0.20" are forecast, mainly in a KCOU>>KUIN line. A light glaze up to as much as a tenth of an inch of ice is expected further to the southeast. In terms of snow, highest amounts are forecast to be in northeast Missouri where temperatures aloft will stay below freezing the longest. One to three inches of snow (which includes sleet) is forecast for these locations. While individual wintry elements (snow/sleet/freezing rain) should stay below warning criteria, the combination of accumulating snow/sleet/freezing rain may warrant a warning headline potentially for northwestern parts of the area. Therefore, have issued a winter storm watch for these locations from late Thursday night through Friday evening. The entire area should transition to a cool rain Friday evening as surface temperatures rise above freezing from southwest to northeast. Moderate rainfall will continue overnight, before ending late Friday night/early Saturday morning. The rain may mix with or briefly changeover to snow before ending early Saturday but no accumulations are expected. (Saturday Night - Next Wednesday) A rare period (so far this winter) of below normal temperatures is expected for most of the remainder of the extended forecast as bi- state area will reside beneath northwest flow aloft. Dry weather is also favored, though we will have to watch a northwest flow shortwave/weak clipper system for the potential for light snow sometime Monday. Climatology however would favor any light snow to stay mainly to the north and east of the area. Temperatures will start off seasonably cold through Monday, with highs generally in the teens and twenties and lows in the single digits and teens. Wind chills Saturday night and Sunday morning slightly below zero across northern sections of the area are also likely. Moderating temperatures back to near or slightly above normal is likely by the middle of next week. Gosselin && .AVIATION... (For the 00z TAFs through 00z Thursday Evening) Issued at 543 PM CST Wed Jan 15 2020 Stratus resulting in predominately MVFR cigs/flight conditions will prevail at the all the terminals through at least 02z. Thereafter the stratus is expected to gradually clear from northwest to southeast, exiting the St. Louis region (KSTL/KSUS/KCPS) around 06z. VFR flight conditions will then prevail through the remainder of the forecast period with increasing high clouds on Thursday. Northwest surface winds with occasional gusts up to 20 kts can be expected tonight, diminishing slightly and veering to north and northeasterly on Thursday. Glass && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Winter Storm Watch from late Thursday night through Friday evening for Audrain MO-Boone MO-Callaway MO-Cole MO-Knox MO- Lewis MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO- Osage MO-Pike MO-Ralls MO-Shelby MO. IL...Winter Storm Watch from late Thursday night through Friday evening for Adams IL-Brown IL-Pike IL. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Portland OR
315 PM PST Wed Jan 15 2020 .SYNOPSIS...A strong low pressure area will move across Vancouver Island late tonight. The trailing cold front will slowly slide across the forecast area tonight. Most elevations below 500 feet appear unlikely to see much more than a brief dusting of snow before precipitation turns to rain. More significant accumulations can be expect in the Columbia Gorge and Upper Hood River Valley. It appears the primary freezing rain threat area will be in the Gorge between Multnomah Falls and just east of Cascade Locks late this evening through Thursday morning. Areas east of Cascade Locks should see mainly snow. A threat of lowland snow will continue late Thursday through Friday morning. The progressive weather pattern will continue over the weekend and into the first part of next week. && .SHORT TERM...Tonight through Friday...Water vapor early this afternoon showed a nicely developed, but compact surface low pressure center near 45N 129W. The 3-hr NAM valid 21Z suggested a central low pressure near 975 mb. This is slightly deeper than the 12Z model runs. Lightning continues over the coastal waters and was within about 30 nm of the coast at 2030Z. KLGX doppler radar indicated 75-80 kt south wind about 7000 feet MSL. It appears the tightest surface gradient is fairly close to the low pressure center, with weaker isobar packing toward the trough base. Buoy 46089 had a peak gust of 52 kt late this morning, but the 20Z observations have shown a slightly decreasing trend. Still not confident the high wind warning will verify, especially with the most recent model runs maintaining an east component where the isobar packing is the tightest. By the time the surface isobar orientation becomes a more favorable south direction, which is early this evening, the gradient is much weaker. The HRRR 80m wind product shows the strongest winds late this morning through the afternoon over the inner coastal waters, with slightly lower speeds along the immediate coastline. The KTTD-KDLS gradient was -7.8 mb at 20Z and is expected to peak around -9 mb. Gusts to 70 mph have been noted at Crown Point and 55 mph at Corbett. The 12Z NAM shows the KTTD-KDLS gradient weakening to around -2 mb by 08Z Thu. South surface wind already making an impact over the southern part of the forecast area early this afternoon. K77S and KEUG were already 50 to 55 degrees as of 22Z. Even KSLE had warmed to 47 degrees at 22Z with 30 mph southerly wind gusts. Models in general agreement showing the cold front passing across the coast by late this afternoon and then slowly moving inland tonight. The mid and upper level trough will be splitting as it moves ashore. Not as concerned about widespread or impactful freezing precipitation in the Gorge and vicinity tonight through Thu morning. Model soundings near Hood River would imply more of a snow sounding. The most likely area for freezing rain and its impacts looks to be in the Gorge between Multnomah Falls and just east of Cascade Locks. Subfreezing temps will be stubborn Stevenson eastward, so there will be a zone east of Multnomah Falls but west of Carson that receives icing, perhaps up to a quarter inch. For now, we just have Winter Weather Advisories for the Gorge and Hood River Valley, but will need to monitor closely for the potential necessity to upgrade to a warning. Upper portions of the Hood River Valley and eastern Skamania County will have mainly snow from this system through Thursday morning. Cannot rule out localized spots of freezing rain in some of the normally colder valleys in the North Oregon Coast Range and also SW Washington interior lowlands. The next weather system is forecast to move across the area late Thursday through Friday morning. Even through the gradient through the Gorge will be neutral or weak onshore, there remains a threat of low-elevation snow. Will go with snow levels to near 500 ft across the north half of the forecast area, with any sticking snow confined closer to 1000 feet, except in the Gorge, especially east of Cascade Locks. Low-level offshore flow through the Gorge develops Fri as another surface low heads toward the southern British Columbia coast. Model 850mb temps gradually moderate to around -4C Fri afternoon with south wind flow. Thus, the low-level east flow will be fairly shallow, getting overwhelmed by the the southerly flow. This will allow snow levels to rise to around 1000 to 1500 feet in the north to 2000 to 2500 feet in the south. Weishaar .LONG TERM...Saturday night through Wednesday...A trailing occlusion will likely bring a reinforcing shot of precipitation to the region Saturday. Snow levels should gradually rise to near the Cascade passes by the end of Saturday with another round of decent mountain snowfall expected. Many model scenarios suggest snow levels will rise well above the Columbia River Gorge and upper Hood River valley elevations as well, but given the pattern, cold air will have a difficult time retreating in these areas so have held snow levels closer to the valley floor in these zones for this time period. Otherwise, it looks like there should be another break in the precipitation Sunday and/or Monday before another storm system brings mountain snow and valley rain to the region early next week. BPhillips/Neuman && .AVIATION...A strong cold front just nearing the coast at 2 pm. Still widespread VFR inland, with spotty light precipitation. But, cigs lower to MVFR just ahead and along the front. This front will push across the Willamette Valley this afternoon, and be near the Cascades Crest by 03Z to 04Z. Will see period of strong southerly winds with the front, mainly along the coast and over the higher terrain, and breezy with gusts 25 to 30 kt across interior lowlands as well into early this evening. Air mass behind the front will be milder, but still unstable. So, will see mix of VFR and MVFR, with plenty of showers, with an evening thunderstorm or two along the coast. Cold air in the Columbia Gorge will maintain areas of snow there, and over higher terrain tonight KPDX AND APPROACHES...VFR at moment, but will see increasing MVFR with rain this afternoon, along with breezy east wind. Front will push across ops area early this evening, more showery pattern overnight. Though may see some snow mix in the rain, am not expecting any accumulation. Temperatures stay above freezing tonight and Thu, with just rain showers. /Rockey. && .MARINE...The 21Z MSAS surface analysis showed a 979mb low centered near 47N 128W. This low was a few millibars weaker than this morning`s 12Z guidance. Nonetheless, a strong cold front moved across the waters earlier today. Widespread storm force gusts were reported by offshore buoys, with buoy 46050 peaking near 60 kt, buoy 46089 peaking near 55 kt, and buoy 46029 peaking near 50 kt. Seas were slow to build today, but they quickly ramped up this afternoon with the strongest winds and are currently running around 18 to 20 ft with dominant period around 10 to 12 seconds. Guidance continues to show this low lifting north inside of 130W tonight and making landfall over Vancouver Island as a 990mb low on Thursday. As the low moves further north this evening winds to subside. However, expect a quick uptick in the winds this evening as the bent back occlusion finally moves across the waters with gusts around 35 to 40 kt possible over the central Oregon waters and gusts around 50 to 55 kt possible over the northern waters. Based on the latest obs and guidance decided to end the Storm Warning for the central Oregon waters at 3 PM and replace it Gale Warning through this evening. Will maintain the Storm Warning for the northern waters through this evening. Expect a brief lull in the winds on Thursday with weak gradients over the waters. Unfortunately, seas will likely remain in the mid teens through the morning hours, but look to fall to around 10 ft by Thursday evening, then into the 7 to 9 ft range by early Friday before another strong cold front approaches the waters later Friday. This front will likely bring southerly gales around 35 to 45 kt Friday afternoon with seas building back into the mid to upper teens Friday night into Saturday. The active weather will continue through the weekend and into early next week as additional disturbances move across the waters. /64 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory until 4 PM PST Thursday for Central Columbia River Gorge-Upper Hood River Valley. Winter Weather Advisory until 10 AM PST Thursday for Western Columbia River Gorge. Winter Weather Advisory until 4 PM PST Thursday for Northern Oregon Cascades. Winter Weather Advisory until 4 PM PST Thursday for Cascades in Lane County. Winter Weather Advisory until 4 AM PST Thursday for Coast Range of Northwest Oregon-Lower Columbia. High Wind Warning until 6 PM PST this evening for Central Oregon Coast. High Wind Warning until 8 PM PST this evening for North Oregon Coast. WA...Winter Weather Advisory until 4 PM PST Thursday for Central Columbia River Gorge. Winter Weather Advisory until 10 AM PST Thursday for Western Columbia River Gorge. Winter Weather Advisory until 4 AM PST Thursday for Greater Vancouver Area-I-5 Corridor in Cowlitz County-South Washington Cascade Foothills-South Washington Cascades- Willapa Hills. High Wind Warning until 10 PM PST this evening for South Washington Coast. PZ...Storm Warning until 9 PM PST this evening for coastal waters from Cape Shoalwater WA to Cascade Head OR out 60 NM. Gale Warning until 10 PM PST this evening for coastal waters from Cascade Head OR to Florence OR out 60 NM. Small Craft Advisory until 9 PM PST Thursday for Columbia River Bar. && $$ Interact with us via social media: This discussion is for Northwest oregon and Southwest Washington from the Cascade crest to 60 nm offshore. This area is commonly referred to as the forecast area.
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
708 PM EST Wed Jan 15 2020 .UPDATE... Latest RAP model shows deep layer ridging from west to east residing across the area overnight that eases southward Thu in response to a cold front tracking through the Deep South and into northern FL by late Thu. The ridging will continue to supply a warm and moist air mass with light winds...resulting in some low clouds and fog later tonight. The fog will be patchy for many southern locations... patchy to areas for central locations...and areas to widespread in the north. The fog will begin to lift and mix out starting around 8 to 9 AM. && .AVIATION... 16/00Z. VFR gives way to BR starting around 06Z and continuing TIL 15Z. Expect brief MVFR VSBY/CIGS at TPA/PIE/SRQ with IFR at LAL/PGD. VFR AFT 15Z with SCT CU and SCT OCNL BKN CI. Light to calm winds overnight pick up and beginning shifting in the morning...becoming NW for the afternoon AOB 08KT. && .MARINE... High pressure across the waters will keep winds 5 to 10 knots for the next day or so with a sea breeze component in the afternoon near the coast. A dry front sliding south Fri and high pressure behind it will tighten the gradient with winds up to 20 knots at times for Fri-Sat. The high pressure begins to shift east Sun and allows winds to decrease. However high pressure builds in from the northwest for the start of next week with increasing winds and seas. && .Preliminary Point Temps/PoPs... TPA 66 81 65 78 / 0 0 0 0 FMY 64 84 65 79 / 0 0 0 10 GIF 64 83 65 76 / 10 0 0 10 SRQ 63 82 65 79 / 0 0 0 10 BKV 58 82 62 77 / 0 0 0 0 SPG 67 79 65 78 / 0 0 0 0 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...None. Gulf waters...None. && $$ UPDATE/AVIATION/MARINE...09/Rude UPPER AIR...29/Delerme DECISION SUPPORT...69/Close