Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/23/19

Area Forecast Discussion
National Weather Service Amarillo TX
654 PM CDT Thu Aug 22 2019 .AVIATION... VFR conditions are expected through the 00Z TAF period. Latest radar trends shows mostly clear conditions expected through the overnight period. Winds will range between south and southeast at 5-15 kts. VCTS conditions are possible starting around 18Z through to the end of the TAF period. Better timing of thunderstorms for tomorrow afternoon will be illustrated in future TAF updates. Meccariello && .PREV DISCUSSION... /Issued 327 PM CDT Thu Aug 22 2019/ SHORT TERM...This Evening through Friday Afternoon.. Latest mid level water vapor imagery reveals shortwave trough and associated moisture field crossing into western OK and central KS. Drier and more subsident air is advancing east into the Panhandles in the wake of the shortwave. As mid level clouds exit the Panhandles, temperatures have started to rise into the mid 80s with dew points near 60. Visible satellite shows two cumulus fields, one in southwest zones and one in northeast zones. If temperatures can recover into the low 90s, an isolated thunderstorm can`t be ruled out as MLCIN starts to erode. However, the weak subsidence aloft and drier air aloft should keep coverage limited, if anything can form at all. Given these concerns, went slightly below previous forecast and NBM with slight chance PoPs across most of the area. If a storm does develop, progged soundings suggest 700 to 1200 SBCAPE in a low shear environment. High bases and DCAPE of 1000 to 1500 J/kg will still promote a strong wind gusts potential. For tonight, will have to watch convection coming off the higher terrain of NM/CO. Most of the CAMs suggest this activity will dissipate before making it into the Panhandles, but the RAP indicates a subtle 500mb wave that may have enough lift to carry storms into the area overnight. These would likely be elevated with some gusty winds and brief heavy rain if they do make it into the area. Otherwise, expected low temperatures mainly in the mid 60s. For tomorrow, a much more notable upper level trough will cross central Rocky Mountains. There is decent agreement in the raw guidance showing a leading shortwave as 500mb winds shift to the northwest through the afternoon. Low level theta-E advection will increase as a lee surface trough develops near the TX/NM state line. A few storms could develop along and east of the surface trough within a 700mb theta-E axis in the western zones Friday afternoon. Moderate instability (1000 - 2000 J/kg) and better effective shear (20-30 knots) will support a few stronger storms especially going towards the evening hours in the northwestern zones. Ward LONG TERM...Friday Night through Wednesday Night... Broad scale high pressure off the western coast will provide northwest flow to the Panhandles. Lee surface low is expected to develop across SE Colorado and track a bit east. Best area of convergence looks to be along the NM/TX border where storms can pop up, and track east along a subtle wave embedded in the northwest flow. Storms may start out discrete, but then merge into a line, and could very well impact all the Panhandles. ML CAPE values in the 1000-2500 J/kg range along with marginal shear and helicity would support strong to severe storms tomorrow night. Hail and wind will be the primary threats, with more wind after the storms line out. Another round of storms will be possible on Saturday as the lee low shifts further east, the drier air will be in place through the Amarillo/Guymon line. Areas to the east will still have the chance for storms. Again, high CAPE and shear values just east of the main dryline convergence could support strong to severe storms on Saturday as well. Sunday, upper level high shifts a bit east, as well as the lee surface low, and most of the Panhandles should be dry, other than some potential lingering storms in the morning. Temperatures will be hot and dry with most areas reaching and likely exceeding 100 degrees again. The heat stretch will be short lived as a weak cold front is expected, bringing the temperatures back into the 90s for Monday. The southwest could still hold onto low 100s. Cutoff low over the Great Lakes associated with this cooler air will merge with another low over south central Canada and provide a stronger surge of cooler air. There is still a potentially decent 850mb temperature gradient (10C) from SW/NE, but for now will not go astray from the blends. As the trof amplifies over the Great Lakes and Midwest late in the week, the upper level ridge will slowly shift back towards the four corners. Surface high will shift over the southeast MO area and start to push moisture back to the Panhandles from the southeast. This could set up an interesting profile given the potential low level jet setup from the south and then decent mid level northwest flow on the lee of the upper level ridge. High surface moisture, very good turning, and decent ML CAPE values could lead to some interesting evening/nighttime storms on Tuesday. Still uncertain if we will have a trigger for these storms given the loss of daytime heating when all these ingredients come into play. Keeping an eye out for possible strong cold front with storms to be associated on Wednesday night, right now too far out and too many model discrepancies to have confidence. Weber AVIATION...18z TAF Cycle: VFR conditions are expected through the period. Confidence in storm impacts for any given TAF site has decreased, so have left mention out of TAFs. There is still potential for isolated storms to develop, but at this time the higher chance is east of the terminals through the early evening hours. Will amend TAFs if storm activity does develop further west. Some storms may try to move out of NM later in the evening and overnight, so the next forecast update may need to address this. Winds should be generally be out of the south at 5 to 15 knots. Ward && .AMA Watches/Warnings/Advisories... TX...None. OK...None. && $$ 29/15
Area Forecast Discussion
National Weather Service Boston/Norton MA
952 PM EDT Thu Aug 22 2019 .SYNOPSIS... A cold front moves across Southern New England overnight, then stalls just off the South Coast. A wave of low pressure then moves along the front and close to the region. Scattered showers and embedded thunder may impact much of CT/RI and Southeast MA through Friday morning. The front moves farther offshore Friday afternoon with drier and less humid weather to follow. Canadian high pressure then provides dry weather Saturday with a mild afternoon and cool night. Onshore flow Sunday will yield cooler conditions along with a few showers possible. Cool weather likely lingers into early next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Cold front has moved into Northern MA. Position of the front is well indicated by dew points. Dew points at 9 pm in CT-RI-SE MA were 70 to 75 (oppressive humidity) while values at Pittsfield, North Adams, Orange, Fitchburg, and Lawrence were in the mid to upper 50s. Radars show showers over NYC and SW CT moving east. This batch is mostly a concern of our South Coast areas from around 1130 PM to 230 AM. SBCAPE from the SPF RAP shows 500-1000 J/Kg lingering over CT- RI-SE MA through midnight, then diminishing. This should support the showers moving across from NYC. Synoptic support increases later tonight as Canadian upper trough swings south, and our area moves under the right entrance region of the supporting upper jet. PW values are forecast around 2 inches overnight, supplying moisture for clouds and showers/thunder. We will continue to show an area of scattered showers/thunder developing overnight along and south of the cold front, mainly areas south of the Mass Pike. Min temps will be highly dependant on the dew points. South of the front temps and dews will linger in the low to mid 70s. North of the front we expect temps to fall into the 60s, except mid to upper 50s along the Berkshire east slopes and parts of Northern Worcester County. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... 4 PM update ... Friday ... Showers with embedded thunder and heavy rain possible during the morning across CT-RI and south of the MA pike, especially south coast of RI/MA. For what it`s worth the new 12z EC has trended slower with the departing rain shield, however all guidance including the CAMs support a drying trend in the afternoon along with sunshine developing from northwest to southeast. Should turn out to be a nice afternoon with highs in the upper 70s to lower 80s (seasonable for late Aug) but very comfortable humidity with dew pts falling into the upper 40s and lower 50s! Friday night ... Dry post frontal airmass overspreading the region with a cool north drainage flow. Thus leaned toward the cooler guidance with lows in the 50s regionwide, upper 40s for NW MA and around 60 for the big city of Boston. && .LONG TERM /SATURDAY THROUGH THURSDAY/... 4 PM update ... Highlights... * Mild temperatures and dry conditions Saturday * Cooler than normal temperatures expected Saturday through Monday, with spotty light rain or showers at times * Temperatures moderate by mid week, with another chance for showers Tuesday through Thursday Details... Saturday and Sunday... The weekend looks overall pleasant and cooler, with a very comfortably dry airmass in place. A large area of high pressure at the surface moves east from southern Canada into northern New England and remains anchored there through the weekend. While some lingering weak troughing and cold pool aloft remain, high pressure and an especially dry column should keep rain chances to a minimum. Best chance of some showers will be on Sunday as moist low level advection increases on north easterly flow which could allow for some shallow showers...can`t rule out a pop up shower for most of the region but the best chance would be along the south and east coasts and coastal plain. Speaking of northeasterly flow around that surface high, the pressure gradient tightens on the southern end, bringing gusty northeast winds on Sunday (and to a lesser extent on Monday), mainly along the south coast into Cape Cod where winds could gust to 25-35 mph. Comfortable conditions both days under a deep cold pool. H85 temps down around 6-8C will support below average high temperatures in the 70s each day...60s along the east coast on Sunday given increased onshore flow. Dewpoints remain comfortable in the 50s. Monday through Thursday... Monday looks to remain mostly dry with continued influence of high pressure and only a slowly moistening atmospheric column. Winds along the south coast remain gusty but start coming down. It`s not until Monday night/Tuesday that we really see signs of a warm frontal feature ahead of two incoming low pressure moving from the Great Lakes into Canada, and another potentially approaching southern New England up the east coast. High degree of uncertainty on how these features play out and interact with each other, but the general idea will be increasing moisture as dewpoints surge back into the upper 60s Tuesday, into the 70s by Wednesday into late week. Overall an unsettled pattern with at least periodic rain chances Tuesday through Thursday as several frontal boundaries and shortwaves move through. Not much instability for thunder, at least through mid week given cool northeast flow. Temperatures remain a bit below normal Tuesday, in the 70s, before rebounding into the low 80s by mid-late week as warmer subtropical air is pulled up the coast downstream of the trough. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/...Moderate confidence. Tonight... Mainly dry initially. VFR-MVFR cigs/vsbys moving into CT-RI-SE Mass 03Z to 06Z. Isolated thunder possible. Mainly VFR and dry north of the MA pike. Friday... Showers in MVFR-VFR possible during the morning across RI/CT and southeast MA, especially along the south coast and Islands. Otherwise trend will be for VFR, dry weather and NW winds. Friday night... VFR, dry weather and northerly winds. KBOS Terminal...High confidence in TAF KBDL Terminal...High confidence in TAF. Outlook /Saturday through Tuesday/...Moderate confidence Saturday: VFR. Saturday Night: VFR. Breezy. Slight chance SHRA. Sunday through Sunday Night: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA. Monday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA. Monday Night: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA. Tuesday: VFR. Breezy. Slight chance SHRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/...High confidence. Tonight ... Scattered showers and isolated thunder especially 11 PM to 2 AM along the southern waters. Additional showers arrive on most waters after 2 AM. SW winds slowly shifting to NW as a cold front stalls over the southern waters. Seas lingering at 5 feet south of Block Island, but expected to diminish. We will continue the Small Craft Advisory to 2 AM. Friday ... Scattered showers with isolated thunder and heavy downpours possible in the morning, then trending drying in the afternoon from NW to SE. Friday night ... Cold front offshore with WNW winds and dry weather. Outlook /Saturday through Tuesday/...Moderate confidence. Saturday: Winds less than 25 kt. Seas locally approaching 5 ft. Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Slight chance of rain showers. Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers. Monday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers. Monday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 2 AM EDT Friday for ANZ254>256. && $$ SYNOPSIS...Nocera/BW NEAR TERM...WTB/Nocera/BW SHORT TERM...Nocera LONG TERM...BW AVIATION...WTB/Nocera/BW MARINE...WTB/Nocera/BW
Area Forecast Discussion...Updated
National Weather Service Billings MT
926 PM MDT Thu Aug 22 2019 .UPDATE... Cold front was about to move into Rosebud County at 0230Z per surface obs. Inverted trough was over E. Sheridan, Powder River and SW Custer Counties. Thunderstorms that moved through Billings area earlier did have hail up to golf ball size and accompanying damage. Two areas of storms remained. One was a line over SE MT oriented N to S in the trough. The other was N of KBIL in post- frontal regime just ahead of upper trough. A few other storms were moving NNE through Big Horn County. PWAT`s were over an inch in SE MT with ML CAPES of 1000-1500 j/kg. Wind shear continued to be minimal in the SE. Given the above, the threat for severe weather continued N and E of Billings. Latest RAP had good handle on precip. placement so adjusted nighttime PoPs toward this model. HREF showed precip. dissipating late tonight over the E, but approaching upper trough will generate more convection over western areas. Temps looked reasonable. Adjusted winds toward ADJLAV which had good handle on speeds. Arthur && .SHORT TERM...valid for Fri and Sat... Trough was approaching from the west with a low developing at the surface, while an associated cold front moved through western areas this afternoon. Ahead of the front, southeast winds were gusting to around 40 mph near the Dakotas border. The cold front will continue to push east through the evening with showers and thunderstorms developing over the southern mountains and moving off onto the plains, while another area of focus for thunderstorm development will be an area of convergence over eastern areas. Some of the thunderstorms could be strong to severe over the area with good instability, but marginal shear. Best chances for strong thunderstorms will be generally east of Billings. Main threats will be strong wind gusts, hail, and heavy rainfall with PWATs approaching 1.50 inches. Showers and thundestorms will linger overnight as the aforementioned trough and associated low move overhead, and upslope flow continues at the surface. Shower and thunderstorm chances are greatest over the southern mountains and foothills on Friday as the trough continues to slide east. A strong storm is possible over far southeast Montana. Overall drier conditions can be expected for Saturday, but a weak wave moving through the region in northwest flow will bring shower and thunderstorm chances to the area during the evening. High temperatures behind today`s cold front will be mainly in the 70s on Friday, with highs warming into the 80s for Saturday. Low temperatures mainly in the 50s are forecast through the short term. STP .LONG TERM...valid for Sun...Mon...Tue...Wed...Thu... Generally zonal flow aloft will veer to west-northwest through the day Sunday, but remain dry through the day. Highs around 80 degrees are expected for Sunday. A cold front will shift across the region Sunday evening/night shifting flow aloft to northwest, and bringing precip potential across the region into Monday. Activity should clear out by Monday afternoon. This wave will start the extended period of cooler weather from Monday through Thursday, with temps solidly in the 70s, and a nice break to recent hot stretch. Ensembles appear in good agreement that a drier Northwest flow will persist through this cool period as well. One caveat is that there are several waves moving through the flow, which point to some shower activity through the day Tuesday. Overall atmospheric moisture availability seems pretty limited, but boundary layer moisture may be enough to support some shower/thunderstorm activity. The operational ECMWF swings another wave across the region to end the period, bringing potential for isolated showers to end the work week. Have carried some slight pops for this period, but is quite a ways out at this point. Gilstad && .AVIATION... Showers and thunderstorms will continue over the area overnight, mainly east of KBIL. MVFR/IFR conditions are expected in the storms with heavier rainfall. There will be areas of mountain obscuration. Gusty SE surface winds will continue over KMLS. Ceilings will lower over much of the area late tonight to MVFR/IFR. Low ceilings will continue into Friday morning. Most areas will improve Fri. afternoon. Scattered showers and thunderstorms are expected over the area on Friday with areas of mountain obscuration. Expect MVFR/IFR conditions in thunderstorms, mainly E of KBIL. Arthur && .PRELIMINARY POINT TEMP/POPS... Fri Sat Sun Mon Tue Wed Thu ----------------------------------------------------------- BIL 060/079 060/089 059/080 052/076 052/076 050/075 050/075 33/T 11/B 31/U 21/U 12/W 21/U 11/B LVM 051/079 053/085 050/078 045/076 045/076 043/075 043/076 52/T 11/B 20/U 11/U 12/W 21/U 11/B HDN 060/077 057/087 057/078 051/074 049/075 048/073 047/074 33/T 11/B 31/U 22/U 11/U 21/U 11/B MLS 062/078 059/087 059/077 052/073 050/073 048/070 047/070 52/T 21/B 31/U 22/U 12/W 21/U 11/U 4BQ 060/078 056/086 058/078 050/073 049/073 047/070 046/070 53/T 41/B 32/R 32/U 12/W 21/U 12/W BHK 062/080 056/085 057/076 050/071 047/072 045/069 044/068 32/T 32/T 43/R 22/U 12/R 21/U 11/U SHR 056/076 053/087 055/078 047/073 046/075 045/072 044/073 26/T 31/B 22/R 32/U 12/W 21/U 22/W && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$
Area Forecast Discussion
National Weather Service Louisville KY
949 PM EDT Thu Aug 22 2019 .Forecast Update... Issued at 945 PM EDT Thu Aug 22 2019 Lowered POPs overnight as the latest CAMs indicate only isld-sct coverage of showers and storms during the overnight period. Low temps in the upper 60s/lower 70s still look on track. && .Short Term...(This evening through Friday) Updated at 243 PM EDT Thu Aug 22 2019 Storms are firing up along a remnant outflow boundary in southern Kentucky from convection earlier in the morning. Storm motions are nearly parallel to this boundary, and as a result, we`ve seen some localized high rainfall amounts and potential minor flood issues due to training storms. The good news is that in some of the more recent low level radar scans from KHPX/KOHX, the outflow boundary the storms fired along is beginning to outrun the convection, which has helped to taper down the training convection threat as storms weaken behind the cold pool. Additionally, there is a low threat for severe weather near the Lake Cumberland region this afternoon. This part of the region has remained partly cloudy to mostly clear for a good part of the day, which has allowed the environment to become unstable and fuel developing storms. So far, storms have remained below severe limits, and generally expect them to remain sub-severe as we move through the rest of the afternoon, but can`t rule out a marginally severe storm developing. Gusty winds and small hail will be possible in the strongest storms. Another line of showers and storms currently along the western TN/KY borders will move into south-central Kentucky over the several hours. There`s a bit of uncertainty regarding how this line will evolve as the current convection in south-central Kentucky may stabilize the atmosphere ahead of it. Recent runs of the HRRR suggest it might hold together through the BWG metro area before gradually weakening as it approaches the Lake Cumberland region. The line in western KY/TN isn`t moving particularly fast, but if it becomes cold pool dominant it might speed up a bit and lower any potential flood threat. As we move into the overnight hours, models indicate the potential for another wave to move through, but vary on the timing and placement of the precipitation axis. Meanwhile, a cold front will begin dropping in from the north, and slowly push through southern Indiana late tonight, and then central Kentucky tomorrow morning. Chances for showers and occasional storms will persist through the morning, but it appears that by the afternoon we may begin to see some clearing in southern Indiana and perhaps northern Kentucky. Highs will generally stay in the low to mid 80s due to the abundant cloud cover and shower coverage. .Long Term...(Friday night through Thursday) Updated at 255 PM EDT Thu Aug 22 2019 Cold front and associated precip will be pushed south into the Tennessee Valley Friday evening, giving a taste of early fall for much of the weekend. Temps will run solidly below normal through the first part of Sunday, with Saturday highs just either side of 80 and lows Sunday morning dipping into the 50s across most of the area. Dewpoints will run in the 50s, certainly atypical for late August. By Sunday afternoon we`ll see an inverted sfc trof ahead of an upper impulse trying to undercut a blocking ridge, and precip chances will ramp up across south central Kentucky. Scattered storms will expand across the Ohio Valley Monday and Tuesday as the Great Lakes ridge gives way to a series of upper troughs coming out of the Plains. Deep closed low over NW Ontario will help to push a front through the Ohio Valley, perhaps as soon as Tuesday night, which would support a drying trend Wed-Thu. However, confidence is limited so consensus leaves us with low chance POPs during the middle of next week. Below-normal temps will continue, but with warmer nights and slightly higher dewpoints. && .Aviation...(00Z TAF Issuance) Updated at 740 PM EDT Thu Aug 22 2019 Forecast problem of the day is a slow moving frontal boundary over the area. Attempted to time the precipitation occurrence at each TAF site. Overnight looking for showers, with isolated thunderstorms possible. A better chance for thunderstorms Friday afternoon. We can look for periods of MVFR ceilings at SDF, HNB and LEX. Light and variable winds will become more northeast Friday morning, with wind speeds 4 to 5 knots Friday afternoon. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...AMS Short Term...DM Long Term...RAS Aviation...MRC
Area Forecast Discussion
National Weather Service Morristown TN
904 PM EDT Thu Aug 22 2019 .DISCUSSION... Scattered showers and thunderstorms continue this evening with greatest coverage across the central valley and mountain foothills. According to RAP forecast analysis, this is in a location of low-level convergence and upper-level divergence. A weak jet streak and diffluent flow aloft is resulting in upper divergence supporting deep lift with a converging 850mb flow of about 20 kt. This is expected to shift northeast overnight with near term guidance suggesting the 850mb flow increasing. This will result in greater boundary layer convergence across NE TN and SW VA between 09z and 12z Friday. The severe weather threat appears very low, but a few thunderstorms could have gusty winds with 850mb flow forecast to be near 30 kt. The main hazard will be heavy rainfall which may result in isolated flash flooding concerns late tonight and early Friday morning across NE TN and SW VA. PW values will be high, near 1.9 inches which is near the max of climatology for this area, and flow will be nearly parallel to the southward moving frontal boundary approaching the region later Friday. Numerous showers and thunderstorms are expected on Friday ahead of this frontal boundary with greatest coverage across the northern two-thirds of the forecast area. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 73 89 72 88 / 50 60 40 70 Knoxville McGhee Tyson Airport, TN 71 86 69 86 / 60 60 50 50 Oak Ridge, TN 72 86 68 86 / 50 60 40 30 Tri Cities Airport, TN 69 82 65 81 / 60 70 50 40 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ JB
Area Forecast Discussion
National Weather Service Blacksburg VA
1132 PM EDT Thu Aug 22 2019 .SYNOPSIS... A cold front moves south into the region Friday. By Saturday, the front will extend from the Carolinas to the southern Plains. Cooler high pressure will build into the Mid Atlantic region Sunday and Monday. && .NEAR TERM /THROUGH FRIDAY/... As of 1123 PM EDT Thursday... Have lowered pops as we head into early overnight throughout most of the region. Exception will be area of moisture convergence along an instability axis in Northeast TN into Western NC that seems to staying active as it edges closer to the NC High Country. Near term models suggest at least 50/50 threat of this stuff holding on into early morning so have pops around 50-60 percent in the far southwest. These showers/storms may fade toward 3am, before another batch arrives ahead of a shortwave moving across KY by dawn into the WV and far SW VA mountains, aided by approach of front to our north. Increasing clouds should maintain less dense fog tonight, but patchy fog appears likely given the storms we had earlier. Previous discussion from early evening... Have finally seen showers/storms weakening early this evening with main axis of instability and deep moisture convergence pushing east toward the Tidewater. Another area of showers, maybe a few storms arrives later this evening in the mountains, but as high-res models are keeping things in a weakened state, not strong storms expected. Will reduce pops as radar and models trends favor a drier evening over most of the forecast area, with a blend toward slight chance of showers east late, with better chance in the mountains. Previous discussion from early this afternoon... Scattered showers and thunderstorms in the mountains will spread east this afternoon into tonight. Some of the storms will be severe containing damaging winds, hail and heavy rains. These storms were initially generated by an outflow boundary from the Tennessee Valley heading east. The leading edge of this cold pool will advance eastward around 25 kt, and will be the one focus for thunderstorm activity. In addition, the combination of instability, orographic lift, convergence and low level boundaries will generate additional showers and thunderstorms this afternoon into this evening. The HIresw-arw-east, HRRR and NAMnest showed convection spreading east between 21z-00z. Coverage and strength of storms will increase into this evening, then decrease. SPC 18z Mesoscale analysis indicated CAPES from 2000 to 3500 j/kg in the east with surface based LIs minus 2 to minus 5. The best bulk shear will be to our north of our region. A cold frontal boundary to our north will slowly drop south and will reach central West Virginia to northern Virginia late tonight into Friday. Scattered showers and thunderstorms will diminish with the loss of solar heating this evening into tonight. Late tonight into Friday morning, additional storms will move into the western mountains. The combination of light winds and low level moisture will result in areas of low clouds and fog. Low temperatures tonight will range from the upper 50s in the mountains to the lower 70s in the piedmont. A southward-sagging, west-east oriented cool front will interact with poorly-defined vort maxima and lead to scattered showers and thunderstorms Friday into Friday night. Some of the storms will be strong to severe with damaging winds, hail and heavy rains. The SPC Day Two convective outlook highlights a marginal risk for eastern portions of our forecast area Friday, given the effective shear values. High temperatures Friday will vary from the upper 60s to the mid 80s in the piedmont. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 300 PM EDT Thursday... The frontal boundary will continue to drop south into Friday night. A weak surface wave low/mesolow overnight Friday into early Saturday may briefly stall the front`s southward progress. This suggests opening with high PoPs on Saturday morning at least to Southside seems realistic, lower PoPs north. Northerly/northeast flow on the cool side of the front and rain falling on the south side of the frontal zone should help shift the front`s position into north- central NC toward Saturday afternoon with falling PoPs toward slight chance or dry. Biggest forecast challenges Saturday are timing the front`s passage into central NC, and on temperatures due to variation in cloud cover. To the latter point, cooler/drier air should filter in on the northeast flow, with lowering dewpoints to much more comfortable levels. Saturday night into Sunday will have quieter weather. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 300 PM EDT Thursday... Outset of the long-term period will see a slow-moving frontal boundary to our south across the Carolinas with a sprawling surface ridge building across the Great Lakes and into the northeast. The bulk of the heaviest rainfall associated with this frontal boundary should be suppressed mainly to our south and east but portions of southern CWA will likely see lingering showers and storms into the day Saturday. A much cooler and drier period appears to be in store for the second half of the weekend and into early next week. Highs will be 10 to 15 below what has recently been experienced with daily highs in the 70s or even upper 60s and overnight lows will be 50s west to low 60s east. Will certainly feel different. The surface high will shift north and east toward mid-week with increasing southerly flow and warmer temperatures along with renewed chances for mainly afternoon convection. An approaching front toward mid- to late late week will possibly trigger a few stronger thunderstorms in an increasingly warm and unstable air mass. A trough of low pressure currently along the FL coast has been given a 30 percent chance of tropical storm formation near the SC/NC coast in the latest NHC 5- day outlook but impacts on the local weather look to be negligible or minimal at this writing. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... As of 715 PM EDT Thursday... Have low confidence in this forecast as models are varying on low cloud/fog formation late tonight while next batch of showers moves into the mountains toward 08-12z. With some clearing and wetter ground may see fog to MVFR/IFR at most places with MVFR cigs, and possibly IFR cigs in the mountains. More showers and thunderstorms will be approaching the central Appalachians from the west Friday morning which may lower ceilings to MVFR at KLWB and KBLF. As the cold front approaches from the northwest on Friday, scattered to numerous MVFR showers and thunderstorms will develop. Will aim for better threat of this east of the mountains Friday afternoon. Confidence on critical parameters is low tonight but higher toward late morning into the afternoon. .Extended Aviation Discussion... Weather pattern will continue to promote scattered showers and thunderstorms. A cold front will approach from the northwest Friday evening into Saturday, resulting in scattered to numerous thunderstorm with potential for organized clusters of thunderstorms to track across the Ohio Valley into the Mid- Atlantic region. Improving conditions with more in the way of VFR will be possible for Sunday, pending just how far south of the Mid Atlantic area the front progresses. Some MVFR showers are possible in the southwest Virginia and northwest North Carolina on Monday. Scattered showers and thunderstorms are expected Tuesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/KK NEAR TERM...KK/WP SHORT TERM...AL/PC LONG TERM...PC AVIATION...KK/WP