Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/21/17

Area Forecast Discussion
National Weather Service Bismarck ND
951 PM CDT Thu Apr 20 2017 .UPDATE... Issued at 951 PM CDT Thu Apr 20 2017 Forecast remains on track. Latest RAP run has backed off considerably on fog coverage later tonight, much closer to HRRR solution. Models still indicate good fog coverage across central ND, but have backed off across the south. Light winds, clear skies and recent rainfall across this area in particular should support fog development overnight. UPDATE Issued at 646 PM CDT Thu Apr 20 2017 No changes with the update other than to blend with latest obs. Satellite imagery continues to show clearing from west to east. Main concern for overnight will be fog development. RAP continues to hit fog the hardest, while the latest HRRR has backed off slightly southcentral, with most extensive coverage across the southwest and James River valley. && .SHORT TERM...(This evening through Friday) Issued at 302 PM CDT Thu Apr 20 2017 Mid/upper level synoptic pattern favors a brief omega type block forming over western and central North Dakota through the short term period. Although this will result in a dry forecast, prospects of fog formation will increase tonight into Friday morning. For the near term, through this afternoon and early evening, popcorn type/isolated rain showers remain on track this afternoon south central into the James River Valley with a tail end shortwave trough shifting through south central ND. Sufficient low to mid level lapse rates will result in isolated showers until sunset. Latest water vapor shows a closed upper level low in northeastern Minnesota and another shortwave in western Idaho which is forecast to develop into a closed low as it traverses into Wyoming later tonight into Friday. A brief omega block pattern evolves across western and central North Dakota. Main concern will be radiational fog/possibly dense, developing after midnight especially in central and southern North Dakota. Subsidence aloft with a clearing sky in the west this afternoon will expand into central ND tonight. Expecting to see a gradual clearing from west to east this evening, however clouds in central ND may inhibit or delay fog formation until late tonight. Low level moisture remains with southeasterly winds developing as surface high pressure builds into the Turtle Mountains. High resolution models in combination with the BUFKIT Hydrolapse/CrossOver Temperatures and Modified Richardson Number all point to fog. Expecting areas of fog/possibly dense after midnight into Friday morning with overnight lows in the 30s. For Friday after the morning fog, blocking high pressure results in subsidence and mostly sunny conditions with highs in the 60s. .LONG TERM...(Friday night through Thursday) Issued at 302 PM CDT Thu Apr 20 2017 Mid/upper level high is shunted south Friday evening as northwest flow with an embedded shortwave trough and associated cold front move into northern North Dakota. This front then sags to the southern ND border Saturday afternoon. A chance of rainshowers resides mainly across the north Saturday as depicted by the alignment of synoptic scale forcing and low level frontogenesis. There could be a period of rain/snow mix Saturday morning across the north. Very cool in the north with high temperatures 40s to lower 60s south. Frontal boundary stalls in northern South Dakota Saturday evening with a chance of showers developing north of the front, into southern North Dakota. Thereafter the pattern remains progressive with a series of systems mostly tracking from west to east across South Dakota. The GFS and ECMWF are not as wet with the initial system slated for Sunday night and Monday across central and southern ND. Still a high chance of pops to likely pops remain in the gridded data. Periodic chances for precipitation continue Tuesday through Thursday but confidence for anything significant and organized remains low at this time. Highs will be in the 40s and 50s through the period. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 646 PM CDT Thu Apr 20 2017 Clouds continue to erode from west to east early this evening. Expect fog development most areas overnight into Friday morning, with IFR possible at most locations and LIFR currently in the forecast from KDIK-KBIS-KJMS. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JNS SHORT TERM...KS LONG TERM...KS AVIATION...JNS
Area Forecast Discussion
National Weather Service State College PA
1115 PM EDT Thu Apr 20 2017 .SYNOPSIS... A frontal system will move through the Commonwealth tonight and early friday. A ridge of high pressure will then build into the area Friday night. A new storm tracking across the southeast states could potentially affect southern Pennsylvania this weekend. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... The meso anal shows the main low over lower Michigan. A cold front extends from the low and bisects Indiana off through southern Illinois. A warm front extends from lake Erie east along the NY/PA border then doglegs sharply south through the Susq River Valley. This has moved little since this morning and has helped enhance windshear over the north where several storms have shown good rotation. A line of convection is moving through the northern mountains as of 10PM with isolated strong/severe storms embedded in the line. The storms are moving into progressively more stable air so the threat of damaging wind and hail should transition into briefly heavy rain. The HRRR shows the MCS continuing across the CWA overnight with a line of showers marking the cold front finally moving through the Central Mountains between 12-15Z Friday morning. It will be another very mild overnight in the 50s region-wide. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... 00Z models a bit slower with passage of cold front Friday, so have held onto the chance of morning showers over all but the northwest mountains. Pre-frontal heating across the southeast counties will likely yield a few thunderstorms across that portion of the state before the front finally exits the area by late afternoon. Friday will be another warm day with increasing sunshine and GEFS 925temps supportive of max temps well into the 70s southeast of the Alleghenies. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... The extended period will begin dry as a shallow cold front settles south of the region for Friday night and Saturday. EFS trends for Saturday and Saturday night track moisture farther south than previous runs...with showers brushing the southern third to half of central PA Saturday afternoon and evening before sliding south of the Mason Dixon line for Sunday and Monday. With uncertainty remaining on the northern extent of showers for this system...have maintained consistency in slight chc to chc POPs during this time frame. Baroclinic zone will be lurking south and southeast of the area early to mid week...while a frontal system crosses the Great Lakes and approaches by Wed-Thu. This should bring an increasing chc of showers by Wed-Thu...but confidence in timing very much in doubt by Days 6-7 as large scale height rises at the end of this time period and beyond will hinder the eastward progress of the Glaks frontal system. The aforementioned height rises are a potentially important signal for the beyond Day 7 timeframe of a large warmup for next weekend. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Widely scattered showers and isolated storms over the east, given southeast flow. Will adjust 03Z TAFS for this. Left some showers in for later, given activity over the Ohio Valley. However, activity to the west is spotty. Should clear out behind the cold front by lunch time on Friday. Outlook... Sat...Mainly VFR with chance of rain increasing by Sat night over the southern airspace. Sun...MVFR/IFR with rain mainly across southern PA. Mainly VFR across the north. Mon-Tue...No significant weather expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Fitzgerald LONG TERM...DeVoir AVIATION...Martin
Area Forecast Discussion
National Weather Service Grand Forks ND
936 PM CDT Thu Apr 20 2017 .UPDATE... Issued at 935 PM CDT Thu Apr 20 2017 No changes necessary. UPDATE Issued at 633 PM CDT Thu Apr 20 2017 Although no returns as of yet from regional radars will keep isold shras going for another hour or so but low confidence on anything developing. Otherwise only changes were to adjust cloud cover to allow for more clearing over Mn. && .SHORT TERM...(This evening through Friday) Issued at 258 PM CDT Thu Apr 20 2017 Any showers this evening and the possibility of fog tonight will be the main issues for the period. Water vapor loop shows the main upper low moving through eastern MN, but another weak shortwave has been rotating along the backside of it through eastern ND. Some of the clouds have taking on a more cumuliform appearance on sat loops, and the SPC meso analysis page shows some fairly steep low level lapse rates across the northern Red River Valley. The HRRR and to a lesser extent the RAP has some showers developing mainly along and west of the Red as that shortwave moves through this evening. Will continue to keep some low POPs going across much of the western counties into the early evening before any showers dissipate after we lose daytime heating. The rest of the night should remain dry as surface high pressure builds into the region. With the high coming in, winds will decrease overnight and become light and variable. There will be at least some clearing after sunset, and with recent rainfall, patchy fog formation will be possible. Have a mention for most of the area. Temps tomorrow will depend on exactly if and where fog forms and how fast it dissipates. Not too much mixing tomorrow at least early on with the surface high shifting only slowly eastward. However, think by afternoon we will at least get some south to southwest winds, so with sunshine late in the day think that highs will be in the upper 50s to low 60s. .LONG TERM...(Friday night through Thursday) Issued at 258 PM CDT Thu Apr 20 2017 Friday night through Sunday...A backdoor cold front will move down from Canada during Sat morn into the aftn with some light rain or showers, freshening wind and falling temps behind the boundary. Look for this feature to pause near the ND/SD border before slowly moving back to the north as a warm front during Sun. The thrust of the pcpn will most likely be Sun night into Mon where amounts of between one quarter to one half inch of rain will be spread throughout the region. Monday through Thursday...Packages of ensemble guidance point toward a cool week to come with average maximum temps in the upper 40s to low 50s and lows dropping to near freezing most nights. Periods of light pcpn could feature a wintry mix early in the morning, especially across northern locations. Differences persist between the GFS and ECMWF in timing and position/strength of shortwaves and sfc systems. The GFS is weaker and farther south generally affording the forecast area a drier solution. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 633 PM CDT Thu Apr 20 2017 Clouds looking pretty cellular so anticipate clearing through the evening. With clearing...low level rh in place and diminishing wind main concern tonight will be fog. With high center dropping into the DVL basin this area looks to have the best potential for fog supported by model fog guidance. Dropped vsby down in DVL but with lower confidence to the east left out of TAFs but will monitor. Otherwise expect VFR conditions through the period. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Voelker SHORT TERM...JR LONG TERM...WJB AVIATION...Voelker
Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
923 PM MDT Thu Apr 20 2017 .UPDATE... Issued at 920 PM MDT Thu Apr 20 2017 Updated the forecast through midnight tonight. Cold front will continue moving through western CO this evening with a nice vort max in the flow traveling just north of Grand Junction and should track over Rifle and Eagle. UPDATE Issued at 819 PM MDT Thu Apr 20 2017 Winds have been dropping steadily in the zones impacted by the Red Flag Warnings with relative humidity values climbing back up and above 15 percent. With weather conditions improving in regards to fire weather conditions, have allowed the Red Flag Warning to expire for Colorado Fire Weather Zones 207 and 290. Now we turn out attention to the increasing showers and isolated thunderstorms across our central and northern zones. Expect snow levels to slowly drop through the overnight period with light to moderate snowfall accumulations across the northern and central mountains above 9000 feet. Current Winter Weather Advisories remain on track with the heaviest snowfall expected across the Park Range near Steamboat Springs and over the Flat Tops. HRRR run has nudged snowfall up a bit, but still within advisory criteria. Rabbit Ears Pass and Vail Pass will be impacted by this passing system. && .SHORT TERM...(Tonight through Friday night) Issued at 333 PM MDT Thu Apr 20 2017 Isolated to scattered showers popping as expected in the warm...highly mixed atmosphere this afternoon. Dry air really infiltrating from the southwest is keeping most of the activity limited to the central and northeast zones with a few strikes of lightning in the mix. The warm temperatures and instability is also helping mix winds down with Red Flag conditions being met across SW.Colorado and the occasional strong gusts near showers. The upstream system digging out of the PacNW has trended northward the past 24 hours with the slower fropa of the GFS also verifying better today. This front will be the focus for organized precipitation moving across the northern half of the CWA this evening with the large scale dynamics and orographic flow keeping precipitation focused on the portions of the central and northern Colorado mountains through Friday evening. The northward trends of the models will not have a huge impact on the forecast with the best accumulating snow favored over the higher terrain from the Park to the Elk Ranges. Some snow likely to fall in the upper Yampa...Colorado and Eagle Basins but temperatures do not appear favorable for accums on the roadways at this time. The pattern in the central CONUS takes on a mini-Rex pattern as the negatively tilted trough over the Rockies undercuts the ridge of high pressure it will be replacing. This allows a back edge energy to rotate across the northern mountains to front range early Saturday and may keep some snow showers going across the divide. Temperatures on Friday can be expected to be some 10 to 15 degrees cooler than today behind the front with lows dipping in into the mid to lower 30s in some of the western lower valleys. .LONG TERM...(Saturday through Thursday) Issued at 333 PM MDT Thu Apr 20 2017 A gradual warmup begins Saturday with warm and breezy conditions setting up for Sunday as we get transitory short wave ridging setting up over the Rockies. A pattern change does look to be on the horizon after this as more amplified ridging in forecast to develop in the northern Atlantic and central Pacific. This will force the jet stream farther south leading to a general and prolonged trough pattern over the West. As a result cooler and more active weather will be impacting our region. Details still fuzzy but appears a brush by system is likely Monday followed by a more significant storm system by midweek. Downstream blocking will allow this system to organize and wrap up farther west than the past several storms. Temperatures stay seasonable up until this possible scenario then would cool significantly to end the week. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 540 PM MDT Thu Apr 20 2017 Scattered showers and thunderstorms will continue through this evening with showers becoming more widespread along and north of Interstate 70 after 09Z tonight. Rain or a rain/snow mix will changeover to all snow in the mountains overnight, favoring the northern and central CO mountains for moderate to locally heavy snowfall rates through Friday morning. CIGS will gradually lower this evening with widespread MVFR to IFR CIGS/VSBYS over northern and central CO mountains, through about 18Z Friday. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Winter Weather Advisory until 6 PM MDT Friday for COZ004-010-013. UT...None. && $$ UPDATE...CC SHORT TERM...15 LONG TERM...15 AVIATION...JDC
Area Forecast Discussion
National Weather Service Grand Rapids MI
738 PM EDT Thu Apr 20 2017 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 322 PM EDT Thu Apr 20 2017 Showers and thunderstorms will end this evening as a cold front moves across Lower Michigan. High pressure will then build into the region providing sunshine from late Friday through the end of the weekend. Night time tempeatures will be cool Friday night and Saturday night and patchy frost is possible. && .SHORT TERM...(This evening through Saturday night) Issued at 322 PM EDT Thu Apr 20 2017 Forecast concerns deal with convection this evening and the potential for frost Friday night and Saturday night. Latest sfc obs shows low pressure over Lake Michigan with a warm front extending southeast from near Grand Haven to just south of GRR to north of Jackson. The cold front stretched from the low south to near the Il/In border. An area of showers/storms was moving east across the eastern cwa producing small to medium size hail. This precipitation will move east of the cwa by 4 pm or so. Then what? It appears as though we`ll have a couple of hours in which the atmosphere may be able to destabilize again before the cold front sweeps east. Latest hi res vis loop shows clearing skies developing over far southwest Lower Michigan. If this continues the I-94 corridor may see storms redevelop in a couple of hours and these storms could be strong/severe too. Moderate shear 40-50kts exists along with 500-1000 j/kg sbcape in the warm sector. The HRRR indeed shows storms developing over Calhoun county around 5 pm and moving east by 7 pm. The current severe thunderstorm watch remains in effect until 8 pm. Mostly cloudy skies will continue tonight as the upper trough swings through. Friday will be chilly with highs 45-50. Skies will gradually clear Friday afternoon setting the stage for cold temperatures Friday night. We expect temperatures to fall into the mid 30s both Friday night and Saturday night. Given the abundant low level moisture in place, frost seems like a real possibility along/south of I-96; we added patchy frost to the grids both nights. .LONG TERM...(Sunday through Thursday) Issued at 322 PM EDT Thu Apr 20 2017 The beginning of this period will have near normal temperatures and dry weather. However toward the end of this period we get back into a warm and wet period with thunderstorms likely. The big picture is similar to yesterday, our East Asian Jet will be weak early in the period. That allows the upper low over Hudson Bay to dig just far enough south (southern edge of the upper level circulation) into the Upper Great Lakes over this coming weekend so as to blocks the next Pacific system to our south. This will also allow dry weather with a warming trend early next week for Southwest Michigan. By early next week the East Asian jet feature comes back across most of the Pacific and that digs a western trough. Over time that trough slowly moves inland enough to bring showers and thunderstorms with warmer temperatures to this area by Wednesday. This will be just the begging of an extend wet period that will likely last more than a week. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 738 PM EDT Thu Apr 20 2017 Most of the region was VFR behind the thunderstorms, but some areas across Central Lower still was seeing IFR conditions. The ceilings will trend down overnight, with MVFR, fuel alternate ceilings developing. At this point expect there will be enough wind to help keep ceilings from falling into the IFR range. Into Friday morning the ceilings will lift, expecting a return to VFR by the 14-17Z time frame. The VFR should continue for the rest of the day. WNW winds will continue at 15 to 20 knots through the next 24 hours. && .MARINE... Issued at 322 PM EDT Thu Apr 20 2017 No changes to the headline. Waves will slowly diminish Friday as high pressure builds over the lake. && .HYDROLOGY... Issued at 1142 AM EDT Thu Apr 20 2017 Thursday morning rain totals surpassed 1 inch in Mason, Ottawa, and northern Kent counties. Generally two thirds of an inch fell upstream of Croton and one third fell upstream of Evart. Expecting only a slight additional rise at Evart, while Croton could reach bankfull on Friday. Looking Glass and Sycamore avoided the heaviest rain while Maple caught some of it. While flood stage being reached is not the most likely scenario, Looking Glass appears to be the most vulnerable of all the rivers if it gets repeated storms Thursday afternoon. Fortunately, dry weather is expected Friday into early next week. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory until 6 PM EDT Friday for LMZ844>849. && $$ SYNOPSIS...04 SHORT TERM...04 LONG TERM...WDM AVIATION...JK HYDROLOGY...CAS MARINE...04
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
947 PM EDT Thu Apr 20 2017 .SYNOPSIS... An unsettled pattern will continue as a front stalls over our area, with showers and thunderstorms possible each afternoon through the weekend. A low pressure system will exit the area Sunday, with the area drying out next week. && .NEAR TERM /THROUGH FRIDAY/... Evening Update...The area remains under broad high pressure while areas of weak h5 energy traverse a flat ulvl ridge. This has maintained a couple -shra across the far wrn zones. Expect this activity to continue to wane during the overnight. Recent obs show tdd/s ranging from 5-10 degrees F across FA. Think most locales will struggle to reach crossover temps and llvl vert change of humidity will remain negative per HRRR soundings overnight. Thus...not anticipating much of a early morning fg threat outside of the NC mtn valleys and fthills where most of the measurable precip occurred the past 12 hrs. 730 PM Update...The fcst is in good shape. Conv activity continues to wane due to loss of sfc adj pops down mainly over the NC mtns. Expect mlvl debris clouds to hang around in weakening flow with passing Ci thru most of the evening. Temps and td/s are right on track. 500 PM Update...Made some minor tweaks to the hr/ly temps as the mtn valleys are running about 5-7 degrees below the fcst curve. The tstms developing are remaining quite shallow and short-lived associated with a relatively weak passing h5 wave. Not anticipating much more coverage or intensification thru the next update. As of 230 PM EDT Thursday: The pattern aloft features weak ridging across the southeast while split flow yields a closed northern stream low over the Great Lakes, while another trof moves through the southern stream atop the Desert Southwest. At the surface, subtropical ridging dominates over the southeast leading to deep ridging, while a cold front drives eastward out of the Plains into the mid MS and OH River Valleys. Closer to home, ample diurnal heating has allowed for modest instability, upwards of 1000j/kg over the NC/GA and SC mtn regions, while tapering down to around 500j/kg eastward over the Piedmont. With that, any weaker CIN has eroded, or continues to erode atop the mtns/escarpment as convection prevails, while any CIN continues to hold for points east. Guidance tends to favor continued growth of coverage through the afternoon as heating peaks, with any mtn convection propagating slowly eastward along the mean steering flow aloft. This warrants low likely to high chances pops for the mtns through the afternoon, topping out at high chances eastward across the northern NC Piedmont. Points south into CLT metro as well as the I85 corridor regions of SC/GA will be under the influence of the strongest CIN as mentioned above, thus only slight chance pops were featured. Any convection should remain below severe limits as mid lvl lapse rates are rather poor, therefore only garden variety tsra is expected. Pop will lower into the overnight hours as diurnal heating induced instability wains, thus leading to non mentionable pops by NLT midnight. Convective debris spread about the region will erode with time yielding mostly clear skies, however with the exception of the mtn valleys where low stratus is possible. Overall, not expecting widespread fog issues tonight as Td depressions should remain large enough to negate saturation, yet locations that experience rainfall today/tonight will have a non zero chance of patchy fog, especially in the aforementioned mtn valleys. Otherwise for Friday, despite height falls aloft, H5 flow will develop a more swly pattern therefore yielding warmer temperatures through a deep layer. With that, guidance favors even poorer lapse rates and thus less instability on Friday in the warm sector ahead of the front, which should remain north of the fcst area through the remainder of the the period. However, the fcst will still feature healthy pops across the mtns, with near climo pops over the lower terrain. Temperatures on Friday will be quite warm, generally upper 60s to mid/upper 70s over the mtns, while reaching into the mid 80s across the Piedmont amidst partly sunny skies. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 130 PM Thursday: A split flow regime will be in place across the eastern Conus through the short term period, with an upper low expected to drift from the mid-Mississippi Valley into the southeast coastal states from Fri evening into Monday. There is some controversy as to the location of an associated frontal zone at the start of the period, as the NAM and a majority of mesoscale guidance tends to keep the boundary north and west of our forecast area, while the global models generally depict it as having moved into the area by Saturday evening. Considering the orientation of the upper flow pattern, the NAM and its cohorts probably have the right idea, as I don`t see any mechanism, other than perhaps organized convective outflow that would give the boundary a southward push prior to Saturday night. (In fact, even the global models tend to retreat the boundary north of our on Saturday). As such, we expect convection to remain scattered and to be primarily driven by the diurnal heating cycle through the day Saturday. Instability will be adequate for strong updrafts Sat afternoon/evening, but shear won`t support anything much more organized than perhaps a couple of mesoscale clusters, so a severe weather threat exists, but appears to be marginal. The forecast gets a bit more interesting (and uncertain) beginning Sat night and continuing through Sunday, as deep layer forcing increases across the region, and the front begins sweeping across the TN Valley and the southern Appalachians. Meanwhile, high pressure building into the northeast Conus in the wake of a transient northern stream short wave trough is expected to establish cold air damming across the Eastern Seaboard Sat morning through Sunday. As usual, the NAM is by far the most aggressive in the timing and southward extent of the cool air wedge, although the global models are also trending in the direction of developing CAD over our area, albeit keeping it primarily confined to western NC. Pops increase to likely to categorical across the area during this time, but uncertainty regarding the surface pattern (including the location of potential surface cyclogenesis) means there is also considerable uncertainty regarding the degree of any severe weather threat for the late weekend. It`s also worth noting that the NAM is much more intense and slower with the upper low track, digging it farther to the south than the global models. The result is a strong upslope/ upglide response/heavy rain signal over the cold pool by the end of the day Sunday. The NAM does have a habit of over- intensifying upper lows, so this evolution seems dubious, but that`s one more potential scenario to ponder. Temps will remain much above normal through at least Saturday, then are expected to fall to near or even a few degrees below climo Sunday, as cold air damming will likely become established across at least part of the forecast area. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 200 PM EDT Thursday: Medium range picks up 12Z Monday AM just as the the surface low is sliding off the Atlantic coast to exit our area. The upper low may linger over the Carolinas for another 24 hours or so with Atlantic moisture wrapping around the back side in the cyclonic pops were tapered off gradually through Monday PM. A wedge of surface high pressure will build over the Appalachians in the wake of the surface low late Monday and through Tuesday. The parent high is progressive and will shift off the northeast coast by late Tuesday, allowing the surface ridge to break down as another low pressure system sweeps across the central plains. Global models are showing different solutions as far as the track of this low, though they both come to a similar conclusion as far as sensible weather. The ECMWF, with the more southerly low track, brings a surface cold front through the area Wednesday afternoon, though anemic deep layer moisture greatly limits any QPF response. The more amplified GFS swings the low up towards the northeast, sweeping the front northward before it can make it into our area. Though the upper flow amplifies considerably towards the end of next week, any issues should remain past the end of the current extended forecast. A slight increase in cloud cover is the only sensible weather advertised through the end of the medium range on Thursday. Temperatures will begin the period near average and gradually rise to above average through Thursday. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... At KCLT and Elsewhere: Mainly VFR conds thru the period. The pattern doesn`t change much over the next 18 hrs with a broad sfc high engulfing the region. Ongoing isol -shra/tstms will continue to diminish thru 06z...with mainly debris clouds persisting thru daybreak. KHKY and KAVL could see early morning VSBY restrictions...likely remaining in the MVFR range. A weak cold front works in and stalls near the NC/SC line aft 18z which will spawn sct -shra/tstms. Thus...have prob30 thunder for all sites except KAND late in the period. Outlook: Another backdoor cold front is expected to settle over the fcst area this weekend, with restrictions and precipitation likely. Confidence Table... 01-07Z 07-13Z 13-19Z 19-00Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% High 100% High 100% High 100% KHKY High 100% High 93% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...LEV NEAR TERM...CDG/SBK SHORT TERM...JDL LONG TERM...LEV AVIATION...SBK
Area Forecast Discussion
National Weather Service Huntsville AL
943 PM CDT Thu Apr 20 2017 .NEAR TERM...(Rest of tonight) Issued at 943 PM CDT Thu Apr 20 2017 GOES-16 imagery shows a band of mostly mid-level clouds gradually drifting into the HUN CWFA from the north, while area radars show showers rapidly diminishing as they approach the TN-AL state line. A few showers have been persisting along the AL-GA state line but these are drifting into Georgia. Area temperatures are mostly in the low- mid 70s with a few cooler exceptions. Short-range and convection-allowing models are in solid agreement on keeping the area dry until after 09-10Z, although the HRRR does bring in a stray shower or two at times along the NW state lines. Forecast PoPs will be tweaked but the general trends will stay the same with 20-30% mainly north and west of Huntsville. Sky cover will need to be adjusted slightly to match the approaching cloud bands mentioned above. Temperatures are on track to reach the low-mid 60s, although some minor adjustments may be needed for cooler spots. A little bit of fog is possible where rainfall occurred earlier (as evidenced by the Scottsboro observation) but it should not be widespread. .SHORT TERM...(Friday through Saturday) Issued at 106 PM CDT Thu Apr 20 2017 Forecast gets a bit interesting beginning on Friday. The aforementioned frontal boundary or perhaps a prefrontal trough/outflow may help spark convection across the area on Friday. Model progs show a moderately unstable airmass with weak shear. With fairly dry air aloft, expect some slow moving storms with gusty winds and locally heavy rain the primary concern. Again, given the surface features the highest pops will be positioned north. May see another lull in the festivities Friday evening before the the cold front finally makes its formal approach toward the region. The 06z/12z model trends have been for a weaker low and more of an open wave feature to move across on Saturday. In terms of precipitation and convective potential that would spell a somewhat downward trend in potential. The 12z NAM has thrown us a hard curveball with the introduction of additional northern stream energy into the trough and an eventual cutoff low by Sunday. Not sure I`m exactly diving into the deep end with that solution, but either way, the initial surge of energy on Saturday will place the highest QPF along and north of I-40 to the Appalachians. Our convective potential will be mostly convergence driven with the front along with the diurnal forcing. Overall, that doesn`t look overly impressive but sufficient for high chance to likely pops. The upper flow does become increasingly divergent late Saturday/Saturday evening which should help increase precip/QPF potential. Based on the timing of the front will taper pops from west to east on Saturday evening with perhaps some lingering showers behind the front. .LONG TERM...(Sunday through Wednesday) Issued at 200 PM CDT Thu Apr 20 2017 There is quite a bit of disagreement between NAM12 and synoptic models guidance concerning how quickly the surface and associated upper low push east of Alabama. NAM12 seems to be an outlier and keeps the surface low much further west. Therefore, it keeps high precipitation chances over northern Alabama and Southern Middle Tennessee. The synoptic models move the surface low much further east into the Carolinas. Since the ECMWF does keep some precipitation over northeastern Alabama on Sunday (and given how wet the NAM12 is), forecast reflects Superblend model forecast of isolated to scattered lingering showers on Sunday (~ 40 percent chance in eastern counties/20 percent near the AL/MS border). Even if we do not see as widespread shower activity, cloud cover and cold air advection will make it seem very cool. Highs in the upper 50s to around 60 degrees will be a far cry from Saturday`s highs (about a 25-30 degree difference probably). In fact given the 925 mb temperature values forecast by models the highs on Sunday could even be a bit cooler than that. By Sunday evening, models move any lingering precipitation into northeastern Georgia and the Carolinas. Clouds may not decrease until after midnight, except in locations west of I-65. This should allow for slightly cooler low temperatures in the mid to upper 40s in northwestern Alabama around daybreak on Monday. With abundant sunshine on Monday, believe highs should rebound into the lower to mid 70s (925 mb temperatures climbing back into 15-17 degree range). This warming trend will continue as an area of high pressure continues to hold in place over the Tennessee Valley. Expect highs to climb back into the lower 80s by Tuesday and could be even warmer later in the week. A strong storm system develops over the upper Midwest towards the end of the week, but energy with this system will remain too far north to affect northern Alabama and southern middle Tennessee through Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 636 PM CDT Thu Apr 20 2017 VFR conditions are expected (with some confidence) through ~14Z Friday. Confidence decreases afterward as showers/storms develop near a cold front sagging into the region. Scattered showers/storms could impact either KHSV or KMSL after 14Z, but impacts are more likely after 16-17Z as the front gets closer and heating maximizes. TAFs include VCTS at that point because details are difficult to time at this range. Future TAF issuances will hone these details. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...BCC SHORT TERM...15 LONG TERM...KTW AVIATION...BCC For more information please visit our website at
National Weather Service Jackson KY
1047 PM EDT Thu Apr 20 2017 .UPDATE... Issued at 1047 PM EDT THU APR 20 2017 Only a few showers have popped up across eastern Kentucky thus far this evening. The general trend in the HRRR has been for less activity through first part of the overnight, before the cold front gets closer towards dawn. This seems reasonable given the current radar trends. As such, have delayed the better POPs later still. Temperatures have cooled into the mid 60s in the valleys, while broader valleys and ridges remain in the lower 70s. A modest ridge/valley split should continue over the next few hours, before thicker cloud cover moves in and mitigates the differences a bit more. Updates have been sent. UPDATE Issued at 631 PM EDT THU APR 20 2017 A broken line of showers and thunderstorms is attempting to make it in from central Kentucky. Most of this activity is diminishing as it is heading east, and all of the convection across eastern Kentucky has dried up, thanks to dew points in the lower to mid 50s, with a few upper 40 degree readings noted. As such, have delayed the POPs somewhat in the east and kept it dry until the cold front moves in closer later tonight. Skies have also thinned, and will allow for a bit of decoupling in the eastern valleys this evening. Updates have been sent. && .SHORT TERM...(This evening through Friday night) Issued at 428 PM EDT THU APR 20 2017 Ongoing isolated showers and thunderstorms are expected to continue to wain during the rest of the afternoon as we await an incoming cold front overnight. It is along and just ahead of this cold front that we will find our next best chances for precipitation across the CWA, including thunderstorm potential. Latest NAM12 forecast soundings are still showing soundings becoming saturated throughout the column after 6Z (first in the north and a few hours later in the south), giving good support for likely to numerous coverage. That being said, CAPE values aren`t looking that great, generally between 400 and 700 j/kg overnight, with very little llvl wind shear and moist upper levels that would deter any hail potential. As such, expect this to be more of a localized heavy rain event, with some good lightning based on the intensity of the rain...but otherwise not expecting much in the way of high winds (wind speeds aren`t very impressive aloft) or hail. Thunderstorms may intensify slightly during the first half of the day Friday across the southern CWA as the front continues southward through the state. As temps warm through the morning with southerly flow, this will help to boost CAPE values above 1000 j/kg, with LI`s falling to -4 across the central and southern CWA. Some low level wind shear will also be present with southerly winds near the surface and westerly flow in the mid and upper levels. All together, thunderstorms will likely be more prominent in coverage and strength tomorrow with some gusty winds and small hail not to be ruled out. However still think the main threat will be localized heavy rains and lightning. In the northern CWA the front will have already passed, so while showers and thunderstorms are still possible, they will likely be elevated in nature given more northerly flow moving in at the surface. By the latter half of the day, the front will have sagged just south of the state, where it will stall out through Friday night. This will keep enough moisture over the region to promote continued widespread precipitation. However, with northerly flow in the low levels on the north side of the front, we will not see much in the way of instability or thunderstorm potential. As such, have thunderstorms decreasing Friday evening, and kept out all mention of thunder from Friday night through Saturday morning. While temperatures should still reach the upper 60s to mid 70s during the day Friday despite cloud cover and precip in place, northerly winds behind the system will cool the airmass down substantially, dropping to the upper 40s to mid 50s for Saturday morning lows (coolest in the north). .LONG TERM...(Saturday through Thursday) Issued at 430 PM EDT THU APR 20 2017 The period will begin with a trough extending from Quebec southwest into the mid MS Valley and lower MO Valley region with riding extending from parts of the Eastern Pacific north into the Western Conus. At the surface, a wave of low pressure is expected to track along a boundary that will have stalled out to the south of the region during the near term period. This low will slowly track toward the Carolinas through Sunday evening while the southwestern end of the upper trough closes off into an upper level low and moves across the Lower OH Valley and into the TN Valley and southern Appalachians through the weekend. This upper low should meander into the Southeast and finally off the southeast coast for Monday into Tuesday. In its wake, an upper level ridge will build into the Southern Plains and lower OH Valley Sunday night into Monday. However, this ridge will dampen beyond Monday as a broad trough develops from the Western Conus into the Central Conus through midweek. Late in the period, a shortwave trough moving from the Plains into the Great Lakes should generally track northwest of the area with an associated surface boundary briefly approaching the OH Valley at midweek. However, another shortwave moving through the trough should lead to cyclogenesis to the Lee of the Rockies late in the period with the low tracking toward the mid MS Valley late in the period with the boundary returning north as a warm front. Unsettled weather should persist over the weekend, with a steadier rain or showers on Saturday as the shortwave approaches and surface low tracks to the south. Limited instability in the south could lead to isolated thunderstorms, but most locations should receive a good soaking rain from Saturday into Saturday evening. Shower chances will linger into the day on Sunday and possibly even Sunday evening mainly in the southeast as the upper low moves across the area. High pressure will bring drier weather and clearing skies by late Sunday night and persisting into Tuesday evening. With the shortwave passing northwest at midweek and the cold front dropping toward the OH Valley isolated convection will be possible on Tuesday night or early on Wednesday in the far north. At the next system nears late in the period, additional showers and thunderstorms will be possible. However, higher chances are possible after the period. High temperatures and average temperatures will be below normal over the weekend. However, with more sunshine and high pressure in place high temperatures should moderate to above normal levels by Tuesday through Thursday. The pattern from early to the middle of next week should support rather strong nocturnal inversions and valley low && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) ISSUED AT 751 PM EDT THU APR 20 2017 An approaching cold front will bring scattered to numerous showers and thunderstorms to the area overnight into Friday from northwest to southeast. VFR conditions will generally prevail through 06z, and then ceilings will lower down to MVFR/IFR from northwest to southeast as the boundary sags southeast into the area early Friday morning. The front will linger across southeastern Kentucky during the day on Friday, with additional convection firing up, likely sustaining the MVFR ceilings. Some ceiling improvement looks to take place from the north by Friday afternoon. Southwest winds at 5 to 10 kts, with some gusts to around 15 kts, through early this evening, will gradually shift to the west and northwest through Friday. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...JMW LONG TERM...JP AVIATION...GEOGERIAN
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
632 PM CDT Thu Apr 20 2017 .SHORT TERM...(This evening through Friday) Issued at 325 PM CDT Thu Apr 20 2017 All models have shifted the storm track toward the wrn solns shown by previous runs of the GFS and ECM. Thus measurable rainfall will likely be along and west of a line from KAIA-KLBF-KLXN with amounts increasing west. Dry air being drawn in from the east could shift the rain line even farther west and the 18z RAP suggests the good rain could be as far west as the Front Range in COLO. The series of storms earlier this week appears to have taken a toll on moisture. The shift west will delay the onset of rainfall across Southwest Nebraska until late tonight and Friday morning. Highs Friday remain in the 50s and widespread cloud cover is expected. .LONG TERM...(Friday night through Thursday) Issued at 325 PM CDT Thu Apr 20 2017 Pacific high pressure moves overhead Saturday and another storm system will enter the Nrn High plains Sunday. The models continue to advertise a dry south wind Sunday increasing to 20 to 25 mph in the afternoon. A fairly strong cold front will move off the Texas coast and shut down moisture return. Another Pacific cold front sweeps through Nebraska Monday. Modest moisture return develops and rain chances are in the forecast Tuesday through Thursday. This morning`s run of the ECM...GFS...GEF and GEM models suggests a series of disturbances will move through the Cntl Plains. This is a favorable pattern for rain given that a stationary front should set up on the cntl High plains which would draw moisture west for thunderstorm initiation. The forecast is for showers with highs in the 50s and 60s. The GFS and ECM suggest lapse rates could steepen sufficiently across Wrn Neb for thunderstorms and later forecasts will address this feature. The WPC rainfall forecast has responded by wetting the region with a 1/2 to 3/4 of an inch of rainfall and the CPC has outlooked parts of Neb for heavy rainfall Tuesday and Wednesday. The CPC outlook suggests locally higher rainfall amounts could develop. POPs have been limited to 30 to 50 percent given the uncertainty of the storm tracks. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 628 PM CDT Thu Apr 20 2017 Visual flight rules expected tonight with light easterly winds under 10kts over western Nebraska. Increasing high clouds late tonight as showers try to move in from northeast Colorado. MVFR cigs expected over southwest Nebraska towards sunrise with VCSH showers being carried at KLBF. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Power
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
926 PM EDT Thu Apr 20 2017 .SYNOPSIS... A cold front will drop into the Mid Atlantic Friday. Weak high pressure builds over the area Friday night before low pressure impacts the area Saturday night and Sunday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Thunderstorms were able to feed off of steep low-level lapse rates, decent CAPE (around 1000 j/kg), and 30-40 kt bulk shear to organize into a line that crossed the forecast area late this afternoon and evening. These storms entering a slightly more hostile airmass (less CAPE and a bit of CIN), likely aided by nightfall and the loss of daytime heating. Will be clearing the forecast area by 10-11 pm. Database will follow suit. The next area of thunderstorms are back in northwestern Pennsylvania. This area pre-frontal as well. There should be a weakening trend overnight, but the HRRR suggests echoes will approach the northwestern corner of the forecast area after midnight. Will have chance PoPs returning at that time. Most likely just showers, but with a little lingering MUCAPE, adequate shear and lapse rates...wouldn`t rule out an elevated rumble. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... Cold front will push through the area Friday. Still some uncertainty with regards to timing...which will have a large impact on sensible weather across the area. Thunderstorms are expected along/ahead of the front. A few of these storms could become marginally instability increases compared to today (e.g., MLCAPE ~1000-1400 J/kg). Latest SPC Day 2 Marginal Severe risk was shifted further north into our area...which makes sense considering the timing uncertainty of the frontal passage and thus how much destabilization can occur. While slightly better than today...strong wind field remains to the north of the area...which results in only marginally favorable shear profiles for storm organization. Front will stall to our south late Friday into Saturday, leaving us with extensive cloud cover as we remain in the cool sector. Low pressure will approach the area from the SW during the day Saturday...allowing for overrunning precipitation to develop over the area during the afternoon and through the overnight. Uncertainty remains in regards to how far north the greatest QPF sets up...latest trends in the guidance continue to push the highest totals south...keeping them over central VA. 1-2 inches of rain are possible across central VA...with generally less than an inch expected north of I-66. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Low pressure at the surface will likely sink south of the area Sunday as the upper level low forcing it becomes cutoff from the westerlies. The low may meander off the coast for a couple days with high pressure building to the north. This would result in a cool and dreary pattern into the first half of next week. By the middle of next week, the low should move away and high pressure rebuilds to the southeast of the area, resulting in southwesterly flow and a marked increase in temperatures. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... Thunderstorms over BWI/MTN at this time. Otherwise, all activity has pushed east of the area. In metro Baltimore, activity will push east by 10pm. No additional storms anticipated tonight. Fog is another story. There is now sufficient low level moisture. Will be adding MVFR to TAFs shortly, and will reassess to see if IFR warranted. There is certainly a chance at that. Thunderstorms with gusty winds are possible Friday...with flight restrictions possible in any stronger thunderstorms...VFR expected outside of thunderstorm activity. Low clouds and periods of rain could impact the terminals Saturday afternoon through Sunday morning...with sub-VFR possible. Sub-VFR likely in low clouds/onshore flow (generally northeasterly around 10 knots) Sunday into Monday. && .MARINE... Weakening showers and thunderstorms reaching the Bay at this hour. We believe that gusts will be under 30 kt, but are monitoring in case additional Marine Warning will be warranted. A cold front will cross the waters Friday. Additional showers/storms...some with gusty winds...will again be a consideration. All should monitor in case another round of Marine Warnings are issued. Rain is expected for the waters Saturday. Generally sub-SCA conditions expected Saturday night and Sunday. SCA conditions possible Monday with increasing northeasterly flow. Northeasterly flow between high pressure to the north and low pressure to the south may push gusts into Small Craft Advisory territory early next week. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...MSE NEAR TERM...HTS SHORT TERM...MSE LONG TERM...DFH AVIATION...HTS/MSE/DFH MARINE...HTS/MSE/DFH
Area Forecast Discussion
National Weather Service Memphis TN
941 PM CDT Thu Apr 20 2017 .UPDATE... A few storms continue across the northern portion of the CWA this evening, in proximity to the surface cold front that will be moving slowly south overnight. However, with the loss of surface heating, waning instability and an overall increase in convective inhibition should limit the intensity of any thunderstorms that develop. The greatest rain chances will be north of I-40 during the overnight hours. On Friday, showers and thunderstorms will increase in coverage by mid/late morning as the boundary layer destabilizes. There will be sufficient shear and instability to support organized storms, but forecast parameters don`t jump off the chart. Abundant cloud cover and scattered to numerous showers and thunderstorms may limit the amount of instability that is realized. That said, a few strong to severe storms are certainly possible. The marginal risk continues for nearly all of the Mid- South to cover this potential. There is also a risk for locally heavy rainfall across the CWA. The deep-layer shear vector is forecast to parallel the low-level boundary orientation, enhancing the potential for training storms. Precipitable water values are progged to be on the order of 1.2 to 1.5 inches. While not extreme, this is roughly 150% of normal for mid April. PoPs were adjusted during the overnight period, focused more north of the TN/MS line. Otherwise, tweaks were made to other forecast parameters were minor. Johnson && .PREV DISCUSSION... /issued 312 PM CDT Thu Apr 20 2017/ Skies remain partly cloudy over much of the forecast area this afternoon with temperatures ranging from the mid 70s to mid 80s. Scattered showers and thunderstorms were found over portions of northwest Mississippi and much of west Tennessee at this time. A cold front currently extends from northwest Indiana through southeast Missouri and into southwest Texas. The front will drop south into northern sections of the forecast area tonight. As it does, more thunderstorms are expected over the region tonight. There is a marginal risk of severe weather over northern portions of the forecast area with large hail and damaging winds as the main threat. Temperatures will remain on the warm side with lows Friday morning in the low to mid 60s. The cold front will continue to push slowly south into north Mississippi on Friday with more thunderstorms expected. There will be a marginal risk of severe weather during the day on Friday over the entire forecast area with large hail and damaging winds as the main threats. The air will be a little cooler behind the front so temperatures will vary some depending on where the front is in the afternoon with highs ranging from the upper 60s to lower 80s. By Friday night, low pressure will develop along the front over north Texas and track into northeast Arkansas by Saturday morning. This will lift the cold front back north as a warm front Friday night with more thunderstorms expected. There will still be a marginal threat of severe weather Friday night as well. Rainfall could become heavy at times starting Friday night and continuing into Saturday. Temperatures will remain a little cooler than the past few days with lows Saturday morning in the mid 50s to mid 60s. The surface low will track through the region on Saturday bringing a cold front along with it. This will mean more thunderstorms are expected on Saturday with some severe storms still possible during the day. Temperatures will cooler on Saturday with highs in the lower 60s to mid 70s. The cold front will be moving out of the forecast area by Saturday night with rain starting to end from west to east. Temperatures will be on the cool side with lows Sunday morning from the mid 40s to lower 50s. High pressure will start to build into the region on Sunday bringing a period of dry weather for Sunday through Wednesday. Temperatures will be on the cool side Sunday but gradually warm for Monday through Wednesday. By Wednesday night, a new storm system will be moving into the central plains bringing more thunderstorms to the region for Wednesday night and next Thursday. ARS && .AVIATION... 00Z TAF Set Convection along and east of the MS River is quickly dying due to the loss of daytime heating. Meanwhile, convection ahead of an approaching front has begun to push into NE AR. Models indicate KJBR could be impacted around 2Z. Models diverge on what exactly happens with the convection overnight. The NAM keeps most of the activity across NE AR while the RAP bring convection south into the Memphis Metro area. For now have leaned toward the NAM. Thus have kept vicinity and tempo wording in KJBR through 10Z. Expect redevelopment of convection to begin along the front around 13-15Z near Memphis. Low clouds and VSBYS will likely be confined to the convection through at least sunrise except for KMKL where some fog may develop due to rain that occurred today. S winds around 6-8KTS will occur ahead of the front. Winds will turn around to the N-NE behind the front. KRM && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion
National Weather Service Nashville TN
850 PM CDT Thu Apr 20 2017 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Cold front currently located from central IL southwestward across central MO. Mosaic depicts an area of shower and tstm activity just south of the boundary. Models in agreement with moving the front into our area by 12z. However, forcing and the area of higher moisture depth are both expected to decrease with time. Thus, I am in agreement with both ISC grids and Hrrr data which suggests that the greatest pops will be oriented from north to south after midnight. Will therefore go ahead and leave likely pops across the north but lower the southern pops. Otw, overnight lows of 60 to 65 still looks reasonable. Update out shortly. && .AVIATION... 00Z TAF DISCUSSION. Uncertain terminal forecasts thru 21/24Z. Several adms possible, especially 21/09Z-21/24Z. Divergent model solutions, took mean. Sfc front near BNA 21/12Z. South of CSV after 21/18Z. Initial zonal upper level pattern becoming progressively swly thru 21/24Z. Can not rule out VFR VCSH all terminals thru 21/09Z. MVFR vsbys with increasing chances of light to mdt shwrs/tstms thru 21/24Z with predominate MVFR ceilings. Veering sfc winds SW to NW CKV per most post frontal, with persistent SW sfc winds BNA/CKV. 5kt-10kt speed range, 10kt-15kt CSV 21/19Z-21/24Z. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......21 AVIATION........31
The remainder of the short term forecast discussion is unchanged...

An upper level trough will push the upper ridge further east Friday night. A surface front will reach the central Oregon coast early Saturday morning, but dry weather and east winds will persist to the north. Clouds and rain will return to areas south of Salem Saturday morning, but north of Salem may stay dry and possibly even be sunny in spots til close to noon. By the afternoon cloudy skies and rain will return to the entire Portland forecast area. The rain will be rather light, and the front will be out of the area early Saturday evening. An upper trough will maintain post-frontal showers through Sunday with snow levels settling close to the Cascade Passes (around 4500 feet). ~TJ .LONG TERM...No Changes. Previous discussion follows...Sunday night through Thursday...Next week will be marked by a continuation of a cool and wet weather pattern. A series of fronts will move across the region bringing periods of steady stratiform rain, followed by abundant showers in the onshore flow behind each disturbance. Forecast models remain in fairly good agreement with respect to the overall pattern through about Tuesday, when they suggest a low pressure system may develop and move north through the coastal waters. Depending on the orientation and track of this disturbance, breezy conditions are possible later Tuesday across the coastal areas and in the Coast Range. Showers may begin to taper off briefly late Wednesday as models suggests weak shortwave ridging moves over the region, but weakly onshore flow aloft may maintain precipitation in the higher terrain. Forecast models do begin to diverge a bit for the second half of the week, but the biggest net disagreement is more regarding the timing of brief dry periods. The GFS would suggest a bit of a longer dry period with flow turning more northwesterly, compared to the more zonal flow pattern in the ECMWF. However, plenty of spread among NAEFS members keep at least chance PoPs in the forecast through each 12-hour period in the extended. Likewise, temperatures next week look to remain several degrees below seasonal normals. Cullen && .AVIATION...Any lingering showers will come to an end later this evening, with skies clearing overnight. Expect predominately VFR conditions the next 24 hours. However, there could be a brief period of patchy fog or low stratus between 12Z and 16Z due to light winds, mostly clear skies and lingering surface moisture. Any fog or low stratus that develops Fri morning will burn off quickly, yielding mostly clear skies through Fri night. KPDX AND APPROACHES...Predominately VFR the next 24 hours. A few hours of patchy fog or low stratus possible between 12Z and 16Z. /64 && .MARINE...Winds will be generally 15 kt or less through Fri morning as high pres builds over the coastal waters. The high pres will move inland during the day Fri, which will allow offshore winds to develop late. Models continue to suggest that the offshore winds may reach borderline advisory speeds late in the afternoon and into Fri night, but confidence is low. A weakening occluded front will move across the waters Sat, bringing a period of solid small craft advisory southerly winds and possibly even some brief low-end gales. A weak trough will move across on Sun, but expect winds to remain 20 kt or less. A progressive weather pattern appears to set up over the region for most of next week, with numerous frontal systems modeled to move across the waters. Seas are currently around 8 ft this evening and will continue to gradually subside, falling to around 5 ft by Fri afternoon. The Sat frontal system will likely push seas back around 10 ft for a short period. They should then drop back below 10 ft for Sun into early next week. /64/Pyle && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ Interact with us via social media: This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. The area is commonly referred to as the forecast area.
Area Forecast Discussion
National Weather Service Charleston WV
1018 PM EDT Thu Apr 20 2017 .SYNOPSIS... More widespread storms late tonight as a cold front crosses the region. Front lifts back north late Friday night/Saturday. System exits Sunday. Dry early next week. && .NEAR TERM /THROUGH FRIDAY/... As of 1015 PM Thursday... Updated POPs based on current radar, then blended toward the HRRR and RAP through the night. Still showing a line of likely POPs moving through overnight. Also updated temperatures based on current obs and trends. As of 230 PM Thursday... Surface boundary with associated surface trough acting as a trigger for some convective development this afternoon with a thin line of thunderstorms extending from just south of KPKB to KBLF. Also still seeing some isold redevelopment in eastern KY. Will keep at least isold POPs through this evening with higher values to the east. Front approaches from the west tracking through from the 06Z-12Z timeframe. Have not strayed far from inherited forecast in terms of timing the line that will be associated with front as it moves through. For temps...went with model blend with generous nod toward inherited forecast. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 245 PM Thursday... Focus remains on the front lifting back to the north, providing a focus for an extended period of showers and storms through Saturday night. GFS is more generous in terms of holding the higher PWATS through Saturday into Saturday night, which would lend to higher QPF, whereas the NAM is a bit quicker in pulling the mid level moisture out of the area. Regardless, will need to watch areas for repetitive rounds of showers and storms once the frontogenetic zone lifts back north into our CWA, as highlighted by the update to the HWO this morning. Ground conditions are currently still being set up with convection today and the cold front tonight. Lingering on the colder side of the boundary keeps temperatures below normal for much of the CWA in the short term. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 245 PM Thursday... Long range models now strengthening the short wave trough affecting the Great Lakes and its southern extent of rain into the northern half of the CWA. However, blended guidance still keeps not only the values of these POPs low, but the area remains contained as well. Until then, drier conditions prevail for the beginning of the week as temperatures rebound again under increasing thicknesses and 850mb temperatures. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... As of 715 PM Thursday... Tricky forecast with multiple lines of broken thunderstorms approaching from the west. Think there will be some consolidation of these, but still rather difficult to time out restrictions to any individual airport. Did not include IFR right off the bat due to broken nature of the lines, but am fairly confident that IFR tempos will be needed as things progress. Cold front will sink through overnight with showers and thunderstorms lingering across the south much of Friday. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SATURDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Brief MVFR and maybe IFR could occur with showers and thunderstorms tonight and tomorrow. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE FRI 04/21/17 UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11 EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07 CRW CONSISTENCY H H H H H H M M M M H M HTS CONSISTENCY H H H H H H M L L H H L BKW CONSISTENCY H H H H H H H H H H M M EKN CONSISTENCY H H H H H H H M H H H M PKB CONSISTENCY H H H H H M M L M H H M CKB CONSISTENCY H H H H H H M M H L H M AFTER 00Z SATURDAY... IFR possible Saturday into Sunday with another wave of low pressure. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...KMC/26 NEAR TERM...KMC/MZ SHORT TERM...26 LONG TERM...26 AVIATION...MZ
Area Forecast Discussion
National Weather Service Blacksburg VA
955 PM EDT Thu Apr 20 2017 .SYNOPSIS... High pressure over the Southeast States will move east and weaken this evening into tonight. A cold front will approach from the west tonight and enter the mountains Friday morning. This front will stall near the NC/VA border Saturday, with a secondary low moving across the area Sunday. This will keep us in a wetter pattern through the weekend. && .NEAR TERM /THROUGH FRIDAY/... As of 955 PM EDT Thursday...Comparatively quieter weather at this point in the evening under weak/relative surface ridge. Across a large part of the Piedmont, current T/Td spreads are rather narrow with dewpoints in the low 60s and winds being light to calm. There`s been periods of mist and fog that have developed in some locales, such as Farmville and into central and eastern Campbell County. I suspect that areal coverage may expand further as we progress into the overnight in the Piedmont and Southside given relatively wet soil and little significant change in dewpoints projected through overnight. It`s slightly drier along and west of the Blue Ridge, and so I kept this confined to the NC foothills, Piedmont and Southside areas. Not thinking dense fog but enough to cause some reduced visibility in patchy areas. Expect a continued dry forecast until after 2 am when threat of showers begins to intrude into our far western counties from a pre-frontal trough in the eastern Ohio Valley. Previous near term discussion issued at 400 PM follows... Scattered showers and thunderstorms have develop this afternoon in the unstable warm airmass. Surface boundary with associated surface trough acting as a trigger for storms with best coverage in Southeast West Virginia. The combination of orographic lift and instability creating convection along the Blue ridge mountains. The Day One convective outlook places the threat for severe weather to our northwest with the better instability closer to the cold front. An isolated strong storm may be possible this afternoon into this evening. Shaped pops this afternoon into tonight towards a blend of the HRRR and NAM. With the loss of solar heating this evening, expect showers and thunderstorms to dissipate. A cold front in the Ohio Valley will move east tonight and reach the Central Appalachians and Mid-MS Valley by Friday morning. Ahead and along the cold front, scattered showers and isolated thunderstorms will move into the mountains Friday morning. Low temperature tonight will range from the mid 50s in the mountains to the lower 60s in the Piedmont. A wet Friday is expected for our region as a cold front pushes east with scattered showers and thunderstorms. The Day 2 Convective Outlook has place the entire forecast area in a marginal threat for severe weather Friday. There is a severe weather potential with possible thunderstorm activity along/ahead of the southward advancing surface cold front. The main threat is for damaging winds and hail. High temperatures Friday will vary from the mid 60s in the northwest mountains to the mid 80s in the Piedmont. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 400 PM EDT Thursday... The need for an umbrella or a raincoat may be an understatement this weekend. Potential for 1 to 1.5 inches of rain is high, with moderate confidence for 2 to 2.5 inches of rain from Friday night through Sunday night inclusive. A stalled surface front is forecast to bisect the Mid-Atlantic Region through the weekend, extending from the North Carolina Coast Saturday into an area of low Pressure over western Tennessee. This area of low pressure is forecast to slowly move east along the stalled front providing a focus for occasional showers and thunderstorms which may morph into an all out period of rain or periods of rain at times through the weekend. Our forecast area is expected to be on the cooler, north side of the front, thus resulting in cooler than normal temperatures, winds primarily out of the north or northeast. The only exception may be Saturday when strong southwest wind flow aloft across the mountains battles with the impinging northeast low level flow coming in from northern WV/VA resulting in potentially warmer conditions for the higher elevations and into far southwestern VA and NC. The more dense cooler air will eventually win out by Saturday night with the entire CWA succumbing to the cooler temperatures by Sunday. The severe weather threat at the present time looks marginal per abundant cloud cover which is forecast to limit instability. Of greater concern will be the potential for runoff issues per increasing confidence for repetitive rainfall and long duration which could linger into Monday. Model Median forecasts for some of the Rivers, such as the Dan River, are indicating at least 50 percent chance for area rivers to experience a rise of half bank to three quarters bank full, and a 30 percent chance for near bankfull or minor flooding. This introduces the potential need for a Flood threat headline at some point for the weekend, and will continue to highlight this in the Hazardous Weather Outlook. Folks that have plans that involve area streams and rivers this weekend should pay close attention to the forecast and potential changes which may occur with respect to the river stage forecasts. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 850 PM EDT Thursday... Recent model runs of the 18Z GFS and 12Z ECMWF still trend towards a wetter Monday. The exiting low pressure system will be slower than previously thought. Further analysis has shown a gradual increase in precipitation chances from the Piedmont to the Blue Ridge Mountains. Southeastern West Virginia and neighboring Virginia counties still show little, if any, chance of precipitation. While observing the models, neighboring forecast offices` trends for higher precipitation chances were also considered. As of 420 PM EDT Thursday... Low pressure will linger along the Mid Atlantic coast Monday, the models trending slower with its departure. This suggests Monday may turn out to be a wetter day than currently forecast with potential for clouds to linger into Tuesday before any sort of drying trend becomes established. For now will trend pops upward for Monday and hang onto some cloud cover for Tuesday. With an east or northeast wind, temperatures will be slow to recover until the sun returns for mid Week. A dry forecast is currently being entertained for Wednesday and and Thursday. A surface front is forecast to move into the Ohio Valley from the Great Lakes, but think this front will stall north of the area as High pressure amplifies over the southeastern CONUS. Temperatures Monday will be cooler than normal, trending closer to normal Tuesday, and then above normal for the second half of the week. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... As of 745 PM EDT Thursday... Earlier scattered to numerous showers and storms have dissipated and/or shifted eastward into eastern Virginia. This leaves the TAFs in VFR conditions that should continue through much of the overnight. Will be watching for development of IFR visibility fog at Lynchburg and Danville given recent rain and that dewpoint/moisture values are currently highest. Winds generally southwest 4-6 kts, lightest with eastern extent. A pre-frontal trough, and later a cold front, will focus additional showers into southeast West Virginia by 08-10z. Expect a deterioration in ceilings toward VFR/MVFR from west to east with increasing coverage of showers. Development of scattered thunderstorms mainly during the afternoon, though a rough timing would be toward the mid to late Friday afternoon hours per the 3-km NAM. Kept either VCSH and/or unrestricted showers due to low confidence at this time range. Winds southwest around 6-10 kts, veering westerly slightly during the afternoon. Extended Aviation Discussion... VFR to MVFR cigs into Friday night with this front. As front moves south Saturday morning, will see more coverage and this is especially true Sunday. During this time, expect cigs/vsbys to be highly variable but most of the time should be sub-VFR. Front moves east Sunday night, with some lingering sub-VFR possible over the mountains, but mainly VFR Monday with high pressure nosing in from the northeast. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK NEAR TERM...AL/KK SHORT TERM...PM LONG TERM...DS/PM AVIATION...AL/KK/WP