Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/18/17


Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
847 PM CDT Mon Apr 17 2017 .UPDATE... Issued at 844 PM CDT Mon Apr 17 2017 Thunderstorms have taken off now that energy is starting to lift out across the high plains this evening. With freezing levels being quite low will likely see a few hailers overnight, but severe chances still look relatively low. Showers/storms will migrate east with the llj overnight before mostly moving out by early morning Tuesday. && .SHORT TERM...(This Evening through Tuesday) Issued at 251 PM CDT Mon Apr 17 2017 The forecast challenges are how much areal coverage of thunderstorms will there be and how strong could they become tonight? Currently, under an increasingly cloudy sky, temperatures are warming through the 40s and 50s on generally east-southeast winds of 5 to 15 mph. Surface high pressure is exiting stage "east" this afternoon and return flow breezy/windy southeasterly boundary layer winds are starting to pick up some gust character as well. The latest 850hpa dewpoint analysis shows +1C to +5C moisture advecting northward on these stronger winds over western NE and western SoDak. Fast forward to later this evening: Latest Rap Refresh model guidance shows strong low level moisture advection in the low level jet overnight, while strong mid/upper level jet streak winds overspread the region. A strong mid level shortwave of low pressure (still digging over the northern Rockies) will move across the northern plains tonight. The latest Rap Refresh suggests lee-side troffing will consolidate into a surface low between Rapid City and Philip this evening before it moves northeast to near Aberdeen by 09Z Tuesday and Wheaton MN by 12Z Tuesday. Between the lift associated with this low and the interaction of low level and upper level jets and available low level moisture (for April), model progs of instability and shear appear to be enough to support thunderstorm activity tonight. Not much in the way of precipitation is expected over this cwa prior to 00Z (7 PM CDT), but the 12Z/18Z suite of CAM solutions today are now all generating thunderstorms that appear to be routed in the boundary layer over UNR`s cwa (between 21Z and 03Z) which they then lift northeastward into this cwa (becoming elevated) mainly at or after 02Z (9 PM CDT) on the nose of the best low level jet forcing and 850hpa moisture advection. In fact, several solutions also hint at a separate secondary cluster of thunderstorms developing in/north of the surface low further north and west near the border of the Dakotas and Montana closer to the core of the upper circulation/dynamic lift later after 04Z and sweep those storms east-northeast through north central South Dakota before lifting up into North Dakota. If convection does indeed develop, it will need to be monitored mainly for potentially large hail later this evening mainly west of a line from Mound City to Miller. East of that line, sub-severe small hail could occur in the strongest of any ongoing convective activity later in the night, along with brief heavy downpours. Precipitation from this potential convective activity should be clearing the far eastern forecast zones early Tuesday morning. Presently, still looks like guidance is generating between a quarter inch and a little over a half inch of precipitation with this precip scenario. Breezy north-northwest winds will be in play Tuesday morning mainly over northeast South Dakota in the wake of this low pressure system until the pressure gradient between the departing low and an approaching area of high pressure relaxes. Tuesday should be a dry day, with high temperatures running generally near to perhaps a degree or two above normal. .LONG TERM...(Tuesday Night through Monday) Issued at 251 PM CDT Mon Apr 17 2017 West to southwesterly flow continues at 500mb at the start of the period as the low off the Pacific Coast continues to eject waves around and into the central U.S. The sfc low will be over the Upper Great Lakes, with a sfc ridge extending from central Canada down through the eastern Dakotas. This ridge will shift into MN by Wednesday morning while the next sfc low moves along the western NE/KS. While the main boundary with all the warm air and better chance of convection stays in NE/KS, expect more of a steady rain to move across our area. A widespread 0.25 to over 0.5 inches is anticipated, although the location of highest potential will likely shift as the time nears and forecast solutions become a little more consistent. The initial 500mb wave differs in intensity/timing. A secondary wave and sfc low across eastern MT late Wednesday afternoon will likely be associated with some precipitation. There is a small potential of for light precipitation extending from ND across our northern counties at through the day Thursday and into Thursday evening as a ridge builds in at 500mb. In our southern counties, high pressure will be the rule, as a sfc high crosses NE and extends a ridge up trough our area. The 500mb ridge will shift to our east Friday, as the remnants of the Pacific low move into the western half of the nation and organizes into a progressive low across KS Friday night. A little more uncertainly comes into play for the end of the week and into the weekend. We look to be in between organizing sfc low pressure near OK and large high pressure across much of western and central Canada on Saturday. The 500mb low should eject northeast across the mid MS valley Saturday night, with a more amplified ridge building across the Northern Plains. Yet another system, this time in the form of an elongated sfc trough looks to stretch from southern Saskatchewan through the western Dakotas and western OK late Sunday night. With a more amplified northern stream, will need to wait and see how much moisture is available to get widespread showers across our area. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 620 PM CDT Mon Apr 17 2017 VFR conditions are expected for much of the taf period, except for perhaps at KABR and KATY late tnt when some mvfr cigs may form. Showers and thunderstorms will march across the state overnight, brief ifr conditions can be expected with any storms. The wind will be gusty out of the southeast through much of the night. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...TDK SHORT TERM...Dorn LONG TERM...KF AVIATION...TDK
Area Forecast Discussion
National Weather Service Bismarck ND
942 PM CDT Mon Apr 17 2017 .UPDATE... Issued at 928 PM CDT Mon Apr 17 2017 Little change with this update other than to blend to observed trends and the 00 and 01 UTC hi-resolution rapidly updating iterations. As of 0230 UTC, a dry slot was clearly evident ahead of the potent shortwave that was located on the North Dakota and Montana border. Strong moisture transport and low level warm air advection ahead this potent shortwave into southwest and south central North Dakota will continue through 08-09 UTC with significant frontogenesis in the 925-700mb layer along the I-94 corridor. Thus, rainfall amounts in excess of 1 inch are possible, especially across the James River Valley. Will also have to monitor convection across the southwest and south central as the HRRR through the evening has suggested the potential for isolated organized storms within its updraft helicity forecasts in a high shear/low CAPE/strongly forced environment. UPDATE Issued at 537 PM CDT Mon Apr 17 2017 Given the presence of low level dry air, characterized by 20 to 30 degree temperature-dewpoint spreads, lowered PoPs through 03 UTC with the initial shortwave. Thereafter, greater forcing and moisture arrives post 03 UTC as the surface low strengthens across central North Dakota. Maintained the mention of thunderstorms southwest and south central tonight highlighted by SREF thunderstorm probabilities in the 20-45 percent range associated with a strengthening low level jet and weak instability. && .SHORT TERM...(This evening through Tuesday) Issued at 222 PM CDT Mon Apr 17 2017 This period will encompass a shortwave h500 trough and deepening surface low forecast to track across the North and South Dakota borders tonight. This low will bring widespread showers and isolated thunderstorms to much of the region with some wet snow mixing in late tonight north. The fairly short wavelength of this h500 wave will bring some sharp thermal profiles and a strong response in the h850 winds. The North American Ensemble Forecast System (NAEFS) has a V component of the wind near a climatological maximum tonight. Supporting this model earlier runs of the NAM depicted 75kts of h850 wind across NE South Dakota tonight. While the latest 12Z run not quite as robust it still is quite strong. Although this wind will not mix to the surface since it moves through around midnight it will act to pull available moisture into the region. The NAEFS precipitable water profile is also impressive near 90 percent of the climatological max. So there should be plenty of moisture for a decent precipitation event. With the ground now fairly dry the soils should soak up the moisture. Storm total rainfall is forecast between a quarter and three quarters of an inch from southwest through northeast North Dakota by Tuesday morning. A narrow band of CAPE supported by strong 0-6 km wind shear will support isolated to scattered thunderstorms along a triple point in the frontal system as it moves across the southern third of the region tonight. .LONG TERM...(Tuesday night through Monday) Issued at 222 PM CDT Mon Apr 17 2017 The extended period will see several h500 troughs move through but in fairly weak mid level flow. The best chance for rain will be Wednesday followed by generally below normal precipitation chances. Highs will be in the 50s Wednesday and mostly in the 60s Thursday through the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 928 PM CDT Mon Apr 17 2017 Widespread rain showers with embedded thunderstorms will continue to develop across southwest and south central North Dakota tonight. IFR conditions are possible as ceilings lower through the night. While rain showers will be less prevalent across northern North Dakota, IFR ceilings will also develop through the night. Some snow may mix with rain late tonight north. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AYD SHORT TERM...WAA LONG TERM...WAA AVIATION...AYD
Area Forecast Discussion
National Weather Service Denver/Boulder CO
927 PM MDT Mon Apr 17 2017 .UPDATE... Issued at 925 PM MDT Mon Apr 17 2017 There was a bit of weak convection over Washington County early this evening, but it died out. There has been no convection for last two hours anywhere in the CWA. The new satellite mid level water vapor pictures marginally show a weak upper trough pushing eastward out the CWA right now. The flow aloft right now is due northwesterly. The easterly 3/5ths of the plains are holding on to lower 50s F dew points right now, but to the west the dew points are in the 20s F. There is nothing upstream as far as convection goes. Will get ride of any pops this update. && .SHORT TERM...(This evening through Tuesday) Issued at 131 PM MDT Mon Apr 17 2017 Upper low over northern rockies with tail end of upper trof will move across Colorado tonight. There is some weak qg ascent with this system but still a batch of high clouds which are moving across the plains this afternoon and may be cutting down the heating a bit. Main concern still centers on thunderstorms developing over the plains later this afternoon and evening with the potential for an isolated severe storm. Surface dewpoints maintaining in the mid 40s to lower 50s over the far plains ahead of the dry line. With temperatures in the low/mid 70s expect surface based CAPES in the 1000-2000j/kg. Sufficient shear for a few severe storms with mainly large hail and damaging winds. Despite lingering low level inversions feel large scale lift and additional heating will allow a few storms to develop. Latest HRRR showing strongest storm mov ing across Washington county later this afternoon/evening. For later tonight and Tuesday, some drier air will move in behind tonight`s trof but still could be some patchy fog and low clouds over far eastern Colorado. Drier on Tuesday but could see a few showers developing in the mountains late in the day in advance of next trof. .LONG TERM...(Tuesday night through Monday) Issued at 131 PM MDT Mon Apr 17 2017 Flow aloft will be southwesterly Tuesday evening with the jet moving from the SW to NE over portions of western CO. At the surface, a low centered east of I-25 will help to bring increased SW winds over the southern plains. This will help to increase fire danger into the evening hours for areas on the plains south of I-70. By midnight on Tuesday the surface low will move east over the plains with a cold front dropping south bringing flow on the plains more northerly by early Wednesday morning. A trough embedded in the SW flow will increase moisture in the high country and bring a chance of rain and snow to the mountains through Wednesday. Colder air will move in by the late morning dropping the freezing level to 8500 ft. A lee side surface low will build on the plains increasing downsloping off the foothills. The upper jet will set itself up over Central CO increasing westerly winds into the mountains with gusts to 55 mph possible at mountain top by the afternoon. This will help to increasing downsloping and keep conditions over the lower foothills out to Denver Metro dry. Further east wrap around moisture will bring a slight chance of rain to the far eastern plains by the afternoon. Winds will also increase on the plains behind the frontal push with sustained winds of 15 to 20 mph with gusts to 30 mph. By Wednesday evening increased subsidence from the west and high pressure building on the plains will help to end any showers over the east. Temperatures for Wednesday will be in the lower 70s. By Thursday upper ridging between systems will build in clearing out any precipitation. The cold push from the North will have settled in bringing temperatures down into the mid 60s. The next system to affect CO will be over the West Coast Thursday afternoon with models bringing it into CO by Thursday night. At this time both the EC and GFS keep the system as an open wave as it makes its way over the state. Upon exiting into KS is when the GFS cuts it off. At the surface, a building surface low to the SW will help to keep SE flow over the plains and into the base of the foothills Thursday evening. This will help to create orographic convection over the foothills Thursday afternoon. Precipitation will become widespread through Friday as the trough pushes through the state. Continue with likely pops for both Thursday and Friday with some changes still possible as models refine the path of the system. Temperatures for Thursday and Friday will continue to decrease with 60s on Thursday and 50s by Friday. Do not believe that freezing levels on the plains will get low enough for snow, however decent rain will be possible with snow still expected for the higher foothills and mountains. Precipitation will slowly come to an end Saturday with cooler NNW flow aloft. Upper ridging will increase by Saturday night with mild conditions expected for Sunday. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 925 PM MDT Mon Apr 17 2017 The DIA LLWAS winds on the IDS4 are showing weak drainage winds in place at many of the sensors. Some have weak westerly winds. The numerous models show weak wind speeds all night at DIA but few of them show south-southwesterlies. There is not much of a low level pressure gradient in place overnight so it seems normal drainage pattern winds should be the rule. I will go that route. && .FIRE WEATHER... Issued at 131 PM MDT Mon Apr 17 2017 Some elevated fire weather concerns for Tuesday afternoon with some southwest wind gusts in the 10-20 mph for a brief time Tuesday afternoon over the Palmer Divide region. Humidities will drop to around 15 percent. Overall conditions for red flag are marginal and there is some green up underway so will not issue any fire hilites. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...RJK SHORT TERM...Entrekin LONG TERM...Bowen AVIATION...RJK FIRE WEATHER...Entrekin
Area Forecast Discussion
National Weather Service Billings MT
746 PM MDT Mon Apr 17 2017 .UPDATE... Showers continue to move east, and as of 730 pm MDT were along and east of a Miles City to Sheridan line. There is some lightning in Carter County, and in fact, one storm intensified a little north of Boyes earlier and probably produced some small hail before weakening. Low level shear definitely stronger in our southeast courtesy of southeasterly boundary layer winds in this area. Latest HRRR continues to show showers exiting our east by 05z and this is consistent with current radar trends. Have adjusted evening pops to account for all of this. The remainder of the night will be quiet with decreasing winds from west to east. We did see a few high wind gusts earlier this evening, not associated with thunderstorms, including a 64 mph gust at the Sheridan airport. JKL && .SHORT TERM...valid for Tue and Wed... Pacific cold front is currently moving across the forecast area this afternoon. Surface obs showed the front moved through Livingston around noon as pressure rises were noted along with some light rain along with a thunderstorm in the vicinity. Clouds will be increasing from the west today so these clearing skies should fill in once again. The front is currently moving through the central counties and will be moving through the far eastern areas by early evening. Water Vapor and Visible satellite showing clearing and subsidence right behind the front so expect some gusty west/northwest winds behind the front for a short period. Shower chances will spread from west to east this afternoon into this evening along with the possibility of an isolated thunderstorm. As is normal this time of year, with freezing levels so low, pea size hail will be likely with any thunderstorm. An upper low and trough off the Pacific Northwest coast Tuesday and Wednesday will provide for a southwest flow aloft across the forecast area both days. Unsettled weather will continue both days with shower chances continuing west of Billings Tuesday as another disturbance approaches the forecast area. By Tuesday night into Wednesday, a stronger upper level disturbance moves across north central Wyoming and across northeast Wyoming/southeast Montana Wednesday morning. At the same time, a surface low will move across the Nebraska Panhandle while a 700mb low tracks across northeast Wyoming. As a result of this placement, models place a good area of qpf across areas from Yellowstone County southeast to Carter Counties. As a result, I increased precip chances to likely for these areas late Tuesday night through most of the day Wednesday. Temperatures will be a bit above normal Tuesday with readings in the 60s. Areas of rain Wednesday will allow temperatures to cool back to the middle 50s to around 60, which is pretty much normal for this time of year. Hooley .LONG TERM...valid for Thu...Fri...Sat...Sun...Mon... Thursday should be a nice day across the forecast area as a ridge of high pressure passes overhead. To our west, an upper level trough will begin to push into the region by early Friday morning. Models diverge with rain chances across the region as some models want to deepen the upper level low further west (better rain chances for is) while others quickly move it through to the south (drier solution). For now left a chance for rain and mountain snow across much of the area on Friday afternoon. Good agreement that another ridge of high pressure moves in for the weekend, keeping conditions mostly dry and warm (in the mid 60s). Another weak disturbance is possible last Sunday afternoon into Monday so left a mention of rain chances in those periods. Overall, temperatures will remain at or above normal through the extended period. Dobbs && .AVIATION... Showers and thunderstorms over southeast MT this evening should exit MT by 04z Tuesday. These showers/storms could produce MVFR conditions and wind gusts up to 45 kt. Otherwise, VFR will prevail across southern MT and north central WY tonight. RMS/JKL && .PRELIMINARY POINT TEMP/POPS... Tue Wed Thu Fri Sat Sun Mon ----------------------------------------------------------- BIL 040/065 041/061 038/065 042/059 040/064 043/066 044/063 02/W 26/R 11/U 12/W 21/B 02/W 30/B LVM 036/060 037/060 031/062 037/056 033/063 038/065 038/061 13/W 33/R 11/B 33/W 21/B 13/W 31/B HDN 037/066 042/061 038/068 041/062 039/065 040/068 042/064 11/B 26/R 11/U 12/W 21/B 01/B 30/B MLS 039/065 042/057 036/067 042/066 042/066 043/069 045/064 41/B 26/R 21/U 01/B 11/B 01/B 20/B 4BQ 039/066 044/058 038/066 040/061 040/063 041/068 044/063 51/B 67/R 31/U 12/W 21/B 01/B 31/B BHK 036/062 039/058 034/064 037/062 038/063 038/066 040/060 50/B 26/R 31/U 01/B 11/B 01/B 31/B SHR 036/063 041/056 033/062 039/055 037/060 038/065 040/061 32/W 67/R 21/B 34/W 21/B 01/B 31/B && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings
Area Forecast Discussion
National Weather Service Caribou ME
1204 AM EDT Tue Apr 18 2017 .SYNOPSIS... A frontal boundary will remain across the region through tonight with some snow possible. High pressure is expected to ridge down across the region on Tuesday into Tuesday night. && .NEAR TERM /THROUGH TODAY/... Update 12:00 AM: Have adjusted winds, temperature, and dew point based on latest observations. No other changes. Previous discussion... An inverted trof will be the focus for precipitation tonight and then drier wx in the offing for this term. The 18Z sfc analysis showed the inverted trof setting up across the region w/the best convergence residing across northern and eastern areas. Radar showed precip affecting basically northern and the eastern section in the form of some snow across the St. John Valley w/some accumulation occurring(around an inch so far). Further s, rain and drizzle w/patchy fog. Temps across the northern 1/2 of the CWA were in the 30s while further s down into the central and downeast region, temps were in the 50s and 60s thanks to some clearing. For tonight into Tuesday, the inverted trof will shift westward per the latest runs of the NAM and RAP which were matching up nicely w/the radar. 12Z UA showed an 700mb trof sitting back across Ontario set to swing across the region. This feature in conjunction w/ the inverted trof at the sfc will allow for an area of precip to set up say from northern Maine down into Washington County. Temps will be falling back as colder air filters down from Canada. It will be cold enough even into Washington County for some snow. The best chances for accumulations will be in the higher elevations. This cooldown w/cooling temps will lead to some icing possible on area roads. Things are expected to drier on on Tuesday as high pres to the n ridges down across the region. It will be a chilly day w/clouds hanging on across the region especially to the north and west. Daytime temps are forecast to be 5 to 10 degrees below normal for mid April Tuesday night will be a rather chilly night w/partial clearing late at night. Overnight temps look like they drop back into the mid/upper 20s for the northern 1/2 of the CWA w/downeast around 30 or so. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... Return flow from the south expected by Wednesday as the surface high pressure pulls off into the Canadian Maritimes. Clouds will be on the increase during the day as a 500m shortwave trough approaches the state from Quebec province. Fairly good agreement that rain will spread from west to east during the day on Wednesday. Could be a few snowflakes mixed in across the higher hills at the onset. Rain showers will continue into Wednesday night, mixing with snow across the higher terrain. Overall QPF amounts look light with the wave, with most areas receiving between a tenth to quarter of an inch. Not expecting to much of a rise on any area rivers. Showers expected to end Thursday morning, with some partial clearing during the day on Thursday as weak ridging builds over the area. Temperatures will run near average for this period. && .LONG TERM /FRIDAY THROUGH MONDAY/... Active pattern continues Thursday night into Friday as an Ohio Valley low pressure system quickly tracks into New England. Still a lot of spread and run-to-run discontinuity with this system in regards to timing and track of the surface low. The ECMWF/GEM have trended north and more aggressive with the QPF compared to their previous runs and are closer to the GFS solution. We will have to watch this event in regards to how much rain falls due to elevated rivers and how much snow may fall across Northern Maine Friday night. The surface high due north over Quebec province and thermal profiles will support snow, especially after sunset on Friday night. Will watch how this evolves over the next few days. Partial clearing is expected by Saturday and all guidance is showing high pressure cresting over the region on Sunday. Very little agreement in the models by Monday next week. Overall temperatures will run near average for this period. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/... NEAR TERM: IFR/MVFR conditions tonight across the north w locally LIFR conditions in snow. VFR dropping to MVFR and perhaps IFR later tonight for KBHB & KBGR. IFR/MVFR for early Tuesday for all terminals w/a gradual improvement to VFR for KBHB & KBGR by 15z or so. VFR for all terminals for Tuesday night. SHORT TERM: MVFR conditions possible later in the day on Wednesday as rain showers and lower cigs move into the region as a weak area of low pressure approaches. Partial clearing on Thursday before rain and maybe some snow for the northern TAF terminals returns Friday into Friday night. IFR conditions or lower could be possible through the period at all TAF terminals. && .MARINE... NEAR TERM: No headlines this term. Will see winds increase slightly tonight to 10 to 15 kts and turn more to the n and hold this direction and speed into Tuesday. Seas will average 3-5 ft w/an ese swell component. Winds will gradually drop back Tuesday night and turn more to the e. SHORT TERM: South winds off the waters on Wednesday will decrease and turn more easterly during the day on Thursday. Seas will generally run 3 to 5 through this period. More significant coastal low expected by Friday with buildings seas and prolonged period of easterly winds. && .HYDROLOGY... The mattawamkeag River at Mattawamkeag remains above flood stage this evening, and is expected to remain above flood stage this week with minor flooding. Other rivers across the HSA remain elevated and are running fast and cold, but are not expected to flood. A weather system late in the week will need to be watched closely for the potential of rain and snow that could cause additional rises. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...Mignone Short Term... Long Term... Aviation...Mignone/ Marine...Mignone/ Hydrology...
Area Forecast Discussion
National Weather Service Goodland KS
555 PM MDT Mon Apr 17 2017 .SHORT TERM...(This evening through Tuesday) Issued at 214 PM MDT Mon Apr 17 2017 This afternoon-Tonight: Stratus, patchy fog, and drizzle have lingered in region of BL moisture pooling in southerly flow just east of surface trough. HRRR shows this pocket of better moisture slowly drifting north-northwest. This stratus should hamper severe threat this afternoon further east, and if this lingers through the evening as long as SREF probabilities may indicate it may. There has been enough clearing in eastern Colorado to allow for better instability to develop, though this is still just outside our CWA. Short range guidance still favors enough clearing and instability to support activity developing transitioning eastward into our CWA. Good deep layer shear (possibly decent low layer shear where there is clearing) may support more organized cells (primarily in CO). Beside elevated convection further east, confidence is higher in severe threat primarily in our far west late this afternoon/evening. Better forcing is still expected o slide north of our CWA, though with WAA ahead of surface low and LLJ we may see convection maintained eastward and this is still favored by all guidance. I was not confident enough to increase coverage beyond 30 percent despite overlapping precip signals. Saturday: There is a chance we may see stratus linger Saturday morning behind the weak cold front (behind surface low), but this should burn off as drier air is shown to finally overspread our CWA. WAA during the day should also support warmer temperatures (assuming clearing skies), and highs should approach 80F for most (low to mid 80s possible). At this point lack of forcing (generally subsident), less instability, and lack of surface feature should support dry conditions during the day Saturday once main precip chances end early in the morning. .LONG TERM...(Tuesday night through Monday) Issued at 203 PM MDT Mon Apr 17 2017 Going into the extended period...the passage of a shortwave across the region Tuesday will allow for nearly zonal flow to set up over a good portion of the country...with H5 ridging over the southern tier. Zonal flow lasts into the Thursday night timeframe w/ only a quick moving shortwave passing just north of the region Tuesday night into Wednesday morning. The track of this system will focus any potential precip along the extreme northern border. This shortwave will give way to a much stronger system that initially comes out of the Pacific NW...then SE off the Rockies as a closed low before shifting into Plains region across Kansas. Following its ride off the Rockies the system does slow into the Plains and will allow for potential area-wide precip lasting from Thursday night into Saturday morning. System slowly clears region thru the day Saturday...giving way to H5/H7 ridging for the remainder of the weekend into next Monday. There is a weak shortwave that follows the ridging on next Monday...but latest model runs keep the system dry as it shifts into the western/central Plains. For QPF purposes...the late week system has potential to bring 0.60- 1.00" of rain to the area. Some thunder potential during this time that could enhance local amts. The northern tier system could bring a few hundredths of an inch of rain. Extensive cloud cover will play key role in area temps in the extended. For Wednesday ahead of main precip/cloud shield mainly 70s for highs with a few 80s in the SE. 50s and 60s for Thursday into Saturday. Coolest on Friday as exiting system brings in cooler air on return flow. Upward trend going into the latter portion of the weekend into next week with 60s giving way to low 70s. Overnight lows will peak near 50F Tuesday night...dropping into the 30s at the end of the week before rebounding into the 40s by end of weekend. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 426 PM MDT Mon Apr 17 2017 The moist southerly near surface flow is keeping the low clouds in place across much of the central high plains region this evening. Expect the surface trough moving across the region to change the wind direction to a north or northwest direction after 14Z with winds turning southeast again by late in the day as the surface lee trough retrogrades back to the front range. KGLD will start out MVFR, but will become VFR after 02Z. MCK should remain VFR through the TAF period. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...DR LONG TERM...JN AVIATION...LOCKHART
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1008 PM EDT Mon Apr 17 2017 .SYNOPSIS... A weak cold front will push into the area from the north tonight, enhancing the possibility of showers and thunderstorms. This front is expected to drop just south of the forecast area Tuesday and then return north as a warm front on Wednesday. This will keep unsettled weather in the forecast through midweek. Another storm system will impact the region next weekend. && .NEAR TERM /THROUGH TUESDAY/... As of 1000 PM EDT: One area of showers and TSTMS continues to sag southeastward across the Upstate, while another area of convection approaches from the west. The upstream activity is generally weakening, with only a few hundred J/kg of CAPE at most to work with. The CAMs that showers will continue into the overnight, but should decrease in coverage. PoPs were tweaked to line up with these trends. Otherwise, an area of high pressure ridge down the Eastern Seaboard overnight, pushing the cold front thru the southern edge of the CWFA. Cold air damming will develop, with easterly upslope flow and upglide overnight allowing precip to expand again in the early morning (either as light showers or drizzle). Isolated TSTMS remain possible thru roughly midnight over the fcst area, but otherwise profiles don`t look supportive of elevated convection. Overnight, min temps should be about 10 degrees above normal with high temps tomorrow about a category below normal where the CAD is in place. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 245 PM EDT Monday...a kind of tricky forecast through the middle part of the week because of what should be an ongoing cold air damming wedge in place Tuesday night and into Wednesday. The guidance shows plenty to maintain the wedge, with low level isentropic lift and warm advection over the cold dome, along with easterly upslope flow to maintain precip production centered on the Blue Ridge overnight and early Wednesday. A high precip probability is warranted, so chances have been raised into the categorical range on the Blue Ridge and likely in most other places. The isentropic lift gradually weakens early in the day and the warm advection late in the day, so precip chances go down, however it is entirely likely that patches of light rain/drizzle will be more widespread and persistent than indicated. It is the high temps that are really problematic with a high bust potential. Have nudged downward a degree or two so we range from the mid-60s in the I-40 corridor to the mid-70s across the Lakelands. However, it is at least as likely that temps won`t get out of the 50s in the usual damming locations. The weakening trend of the forcing continues into Wednesday night while the remaining wedge cool-pool drains away, so in spite of the model guidance showing some response, I think we will see a period of inactivity, thus the dry forecast by early Thursday morning. We are left with a nearly zonal upper flow pattern for Thursday and into Thursday night, with little in the way of forcing. Although, we should retain enough low level moisture to fuel the development of convection with some diurnal heating. This suggests accepting the model portrayal of what looks like a typical diurnal convective precip scenario, thus the chance over the higher terrain and slight chance to the east. Temps will be warmer on Thursday...well above normal. A front should approach from the west early Friday morning, but will most likely remain to our west through sunrise. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 240 PM EDT Monday: Guidance remains in general agreement through the period. An upper low moves from the Great Lakes on Friday to new England on Saturday as short wave ridging builds over our area in its wake. A cold front associated with the upper low moves across the area Friday with high pressure building in from the north Friday night. There will be enough moisture, forcing, and instability for scattered diurnal convection to develop Friday. Precip returns for Saturday as the surface high quickly translates east allowing a moist southerly flow to develop. Temps around 10 degrees above normal Friday drop to near or slightly above normal for Saturday with a cooler air mass and clouds. A stronger upper low then moves into or across the area Sunday and Monday. The GFS keeps the low more open and faster with a deep trof developing on Sunday. The axis of this trough reaches the spine of the Appalachians by the end of the day then quickly moves east of the area Monday. The ECMWF keeps the low closed and slower bringing it to the Middle TN/KY border by the end of the day Sunday then slowly moving it across the Carolinas Monday. This, of course, creates differences in the surface pattern. The GFS spreads precip across the area on Sunday with a hybrid damming pattern as the surface low takes on a Miller B type configuration. The cold front and lows move east of the area Sunday night ending precip with a relatively dry Monday. The ECMWF has a stronger low to our west with a strong cold front. Precip still spreads over our area Sunday but with some in situ damming. A triple point low forms along the front and the developing TMB and generally moves along the I-85 corridor Sunday and Sunday night. The complex low and frontal systems only slowly move east of the area Monday. Of course, these differences could have a profound effect on the amount of precip and or any significant thunderstorm development. Therefore, have gone with a blend for the forecast which highlights the agreements. PoP increases to likely through Sunday then diminishes on Monday. Do show thunderstorms for a portion of the area as well. Temps remain nearly steady a little below normal both days. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... At KCLT and elsewhere: An area of showers with a couple of isolated TSTMS continue to cross the NC mountains and into the Upstate. Instability looks limited, but highest in the Upstate. Using the HRRR as the preferred guidance with respect to convection, I will go with -SHRA or VCSH at the NC TAF sites, and VCTS for the first 1-2 hours in the Upstate TAFs this evening. There should then be a lull in precip late tonight thru at least mid-morning Tuesday. Meanwhile, a backdoor cold front will push thru the area late this evening, bringing winds around out of the NE, except switching to SE at KAVL, with gusts expected during the day. Low clouds should begin to develop as cold air damming (CAD) sets up. Guidance is in good agreement on MVFR to IFR cigs by daybreak. If the wedge deepens, cigs may improve, especially across the NC piedmont. But another round of showers is expected to develop atop the wedge, and may help lock in or lower cigs further during the day. Deeper convection should stay south and west of all the TAF sites, due to the stable air within the wedge. Outlook: CAD should persist Tuesday night and most of Wednesday as well. Low clouds and showers are expected to be widespread under the CAD. The wedge should erode by early Thursday with a return to more typical diurnal thunderstorm potential for Thursday and Friday. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 100% High 87% Low 41% Med 76% KGSP High 100% Med 79% Low 51% Med 77% KAVL High 100% High 91% Med 70% High 83% KHKY High 100% High 86% Low 55% High 81% KGMU High 100% High 86% Low 51% High 81% KAND High 100% High 94% Med 65% High 97% 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: www.weather.gov/gsp/aviation && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...SW NEAR TERM...ARK/JPT SHORT TERM...PM LONG TERM...RWH AVIATION...ARK
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1020 PM CDT Mon Apr 17 2017 .DISCUSSION... The MCV appeared to be slowly drifting eastward toward Washington County at 9:30 PM. High res models were showing the possibility of redevelopment east and south of the MCV tonight. The caveat is that each model has a different solution as to its location and track through the night. The HRRR looks to be verifying best so far this evening. The latest NAEFS climatological percentile PW has SE Texas in the 97th to 99th percentile tonight. The PW of 1.50 inches agrees with the 00Z CRP sounding. Given the latest HRRR model runs and the input from the other high res models, have tweaked the POPs upward for the remainder of tonight. Also adding locally heavy rainfall to those areas with rain chances 60 percent or greater through mid morning Tuesday. 40 && .PREV DISCUSSION... /ISSUED 650 PM CDT Mon Apr 17 2017/ AVIATION.../00Z TAF/ Short term forecasting for TAFs will lean heavily on GOES 16 data, radar imagery and surface analysis due to a mesoscale convective vortex (MCV) moving into the area spawned from last night`s convection across south Texas. Also we have a cold pool driven outflow boundary with a line of showers and storms moving towards SE Texas from central Texas. Convective allowing models provide at least some guidance but it does not take much for storm mode and evolution to change on the mesoscale. Trends for this evening`s convection should be downward and expect convection to be dissipating through 02-03Z. There should be a break in activity but with the MCV convection may start up mid morning so trended TAFs in that direction. KCLL/KUTS may be impacted by outflow this evening as well which is not mentioned in TAFs. These may need to be amended depending upon convective trends with activity to the north. MVFR ceilings are forecast for the morning hours 09-15Z but will depend upon convection. Given cloud cover already over much of the area I have a hard time thinking IFR/fog will develop. Models show the MCV getting stretched out tomorrow but there should be plenty of lift with it along with moisture. Locally there should be 1.5 to 1.8 inches of precipitable water so it may not take much heating to trigger convection given available lift and outflow boundary present. TAFs will carry VCTS for most of tomorrow with hopes of fine tuning possible rounds of TSRA with future TAF updates. Overpeck && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 66 83 67 84 67 / 70 50 10 20 10 Houston (IAH) 67 83 68 84 68 / 60 60 10 30 10 Galveston (GLS) 72 81 72 80 73 / 40 50 20 20 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ Discussion...40 Aviation/Marine...39
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
654 PM CDT Mon Apr 17 2017 .SHORT TERM...(This evening through Tuesday) Issued at 336 PM CDT Mon Apr 17 2017 An upper level trough will move across the Northern and Central Plains tonight. Steep mid level lapse rates 7.5-8.0 c/km and sbcapes 500-800 j/kg will combine with 0-3 km shear from 40 to 45 kts. This will be supportive of marginally severe hail and wind gusts west of valentine through Ogallala. Coverage will likely be isolated at best, with rapid refresh and RAP models showing very little development into the northwest. The best forcing aloft will be across South Dakota. However, with precipitable water values around three quarter of an inch early this evening increase to over one inch across the eastern forecast area overnight. IF any organized areas of storms do develop, brief heavy rain is likely. Thunderstorms chances are from 20 percent across the southwest, and 30 to 40 percent across north central and central Nebraska. The trailing end of any showers or storms should exit the eastern zones by daybreak. A weak cold front will also sweep thorugh the area overnight. .LONG TERM...(Tuesday night through Monday) Issued at 336 PM CDT Mon Apr 17 2017 On Tuesday, partly cloudy and mild with highs ranging in the 70s. Southwesterly flow will be across the western conus as nearly zonal flow exists across the Central Plains. A disturbance will exit California and move into the Great Basin on Tuesday. By Tuesday evening, this upper trough will approach the area, providing another chance for showers and thunderstorms. A warm front across northern Kansas will remain nearly stationary. Increased instability and 0-3km shear from 30-45 kts sufficient for strong storms across most of western Nebraska overnight. The thunderstorms are expected to be elevated, so marginally severe hail will be the most likely hazard. Some storms may also contain brief heavy rain. As the upper trough crosses the area on Wednesday, showers and a few thunderstorms remain likely across north central Nebraska. Chances decrease or end across southwest Nebraska. Models differ on amount of cold air advection behind the front. Current forecast highs remain near the previous, although the GFS model would support warmer highs in the lower and mid 70s across southwest Nebraska. Northwest winds to increase to 10 to 25 mph Wednesday afternoon. An upper trough will dig across the Pacific Northwest into the Great Basin on Thursday, and close off over Colorado and western Kansas on Friday afternoon. This southeastward tracking system will provide better chances for showers to the southwestern half of the forecast area Thursday night through Friday night, while most of the northeast should remain dry. Aside from a slight chance for morning showers southeast on Saturday morning, the remainder of the weekend looks dry. A mid level disturbance Monday for a slight chance of showers. Forecast highs on Wednesday contrast from mid and upper 50s north, to the mid 60s to lower 70s south. Highs in the mid 60s Thursday, cool to the mid and upper 50s by Friday and Saturday, influenced by the upper trough and Canadian high pressure across the region. By Sunday, upper ridging builds back into the the region to bring warmer highs in the mid and upper 60s. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 649 PM CDT Mon Apr 17 2017 Mid and high clouds over most of western Nebraska tonight. Some MVFR cigs will move into southwest Nebraska over night. Strong southerly flow will continue through the early morning. Some isolated showers or virga will continue to move to the east over the Nebraska Sandhills through midnight. Winds will shift to the west and then northwest through Tuesday morning. With uncertainty of showers have only carried vcsh. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Roberg LONG TERM...Roberg AVIATION...Power
Area Forecast Discussion
National Weather Service Lake Charles LA
1042 PM CDT Mon Apr 17 2017 .UPDATE...Latest model output showing deeper moisture associated with east Texas trof to expand eastward into the region overnight. Have introduced pops for all but the most eastern portion of the forecast area, with the highest over southeast Texas. Radar showing considerable convection being maintained just to our west with activity migrating east. Have also noted some development over the near coastal waters. && .PREV DISCUSSION... /issued 722 PM CDT Mon Apr 17 2017/ DISCUSSION... For 00z TAF issuance. AVIATION... Afternoon diurnal convection has been a little more lively today as area lies in weak troffing aloft and a very soupy airmass...although recent radar trends show this slow-moving activity is beginning to diminish. Have not included any additional precip for the remainder of the night although regional 88Ds do show precip associated with a weakening MCV approaching metro Houston at this time...latest HRRR runs agree on this fizzling with little to no impacts expected on the swrn terminals for now. After another round of low clouds late tonight, we should see more convection popping up with daytime heating tomorrow as weak low aloft builds slowly ewd into the forecast area. 25 PREV DISCUSSION... /issued 250 PM CDT Mon Apr 17 2017/ DISCUSSION... Wx map shows surface high pressure ridging across the Northern Gulf, keeping area with southeast winds. Radar showing scattered showers and thunderstorms along and north of I-10 in Southeast Texas and Louisiana. With coverage more uniform and further west resembling sea breeze convection, had to bump up pops across SE TX again this afternoon. Temperatures this afternoon are in the lower/mid 80s. Scattered afternoon showers and thunderstorms expected through early this evening, diminishing after sunset with the loss of daytime heating. Abundant Gulf moisture, daytime heating, and more defined SW to NE oriented trough aloft across E Texas to the Western Gulf is expected on Tuesday. This should provide increased focus and instability, leading to better than normal chances of showers and thunderstorms by Tuesday afternoon. For Wednesday through Friday, the weakness aloft and trough axis is expected to move east of the area. Thus, weak ridging with increased stability and drier air aloft should limit our shower chances to 20% at best. By Saturday, a significant upper level trough aloft will move across the Central and Southern U.S. brining increased precipitation chances by Saturday afternoon and evening across the region. Cooler and drier air expected behind the frontal passage Saturday night into next Sunday. DML MARINE... High pressure off the east coast ridging westward across the Gulf coast will provide a predominate southeast to south flow for most of this week. Abundant Gulf moisture, daytime heating, and a relative weakness in the upper levels, will combine for a daily chance of scattered showers and a few thunderstorms through Tuesday afternoon. Shower and thunderstorm chances will diminish Wednesday through Friday as high pressure aloft builds back over the region. A cold front is expected to bring an increased chance of showers and thunderstorms Saturday, followed by offshore flow after the frontal passage. DML && .PRELIMINARY POINT TEMPS/POPS... AEX 64 82 64 84 / 20 50 20 20 LCH 67 81 66 83 / 20 40 20 20 LFT 66 82 64 83 / 20 40 20 20 BPT 67 82 68 83 / 30 40 20 20 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...None. TX...None. GM...None. && $$ PUBLIC...23
Area Forecast Discussion
National Weather Service Lubbock TX
1100 PM CDT Mon Apr 17 2017 .AVIATION... The latest guidance still indicates that IFR ceilings and visibilities will develop in the KCDS area around 09 to 10 UTC. There is a small chance that KCDS could see dense fog and LIFR VSBYs from 12-15 UTC. KLBB and KPWV look to remain VFR at this time. E-SE surface winds will come around to the south on Tuesday and increase into the 12-16 kt range with VFR conditions through Tuesday evening. && .PREV DISCUSSION... /issued 655 PM CDT Mon Apr 17 2017/ AVIATION... Moist upslope flow at KCDS is expected to result in a period of MVFR to IFR ceilings early Tuesday morning. We expect KLBB and KPVW to remain VFR, although there is a non-zero chance some category reductions could briefly impact either terminal. Otherwise, winds will come around to the south Tuesday morning, with VFR conditions through the end of the forecast. UPDATE... Despite several boundaries seen on radar in the moist E-SE flow across the Rolling Plains, it appears that the cap will be too strong for any local t-storm development this evening, and we have dropped PoPs below mention. The HRRR continues to generate a small t-storm complex in the Panhandle night that could possibly edge southeast toward our northeast counties after midnight. This potential looks very small at this point. PREV DISCUSSION... /issued 349 PM CDT Mon Apr 17 2017/ SHORT TERM... Southward propagating MCS continues across north and northwest Texas with most recent development along west-moving outflow boundary along and north of I-20. Previous boundary from overnight convection has brought deeper moisture to areas east of the Caprock where surface dewpoints are holding in the mid-upper 50s. A more aged but still discernible W-E surface boundary exists across the far southern CWA where another moisture and instability axis exists. Meanwhile hi-res satellite imagery shows a shortwave trough working across the High Plains of West Texas with overall forcing and enhanced shear relatively absent from this feature. Expect moderate instability to exist across much of the eastern half of the area by early evening coincident with deeper moisture with potential storm development along previously mentioned boundaries and within upslope regime immediately along the Caprock escarpment. Lack of shear and deficient quantity of CAPE will limit overall health and vigor of any updrafts that do form. Expected easterly flow will maintain higher low level moisture across the Rolling Plains so have added mention of patchy fog there toward daybreak. Mid level heights will increase overnight as shortwave ridging builds across the region. A surface trough will strengthen during the day Tuesday with increased moisture gradient and an uptick in winds. The lack of any upper level support, warmer and drier temps aloft should effectively keep a lid on convective development. LONG TERM... Do not anticipate major changes to medium range forecast this period. Weak shortwave ridging Tuesday night with southerly boundary flow will give way to mid/upper flow becoming more zonal by Wednesday. W/SW surface winds will allow for a warm day Wed with dryline pushing east into the eastern Rolling Plains or perhaps east of the entire region. In any event, temps warm into the upper 80s or even lower 90s Wed with a mostly dry and capped atmosphere. Some changes coming by Wednesday night as upper low and trailing trof moving eastward across the central/northern Plains will push associated cold front into our region by Thursday morning. NAM hinting at some post frontal convection Thursday afternoon. Definitely cooler then with NE surface flow. Ensemble MOS has high temps back in the 70s on the Caprock. Thursday night into Friday...attention shifts to SE moving negatively tilted upper trof which is progged by models to approach W TX Thursday night or early Friday. With likely moist easterly upslope flow combining with forcing...could see a few showers and thunderstorms in this time frame and will likely leave pops as is with chance category across the northern South Plains and SE Panhandle and slight chance elsewhere except over the SW where pops unlikely. This second upper low is progged by GFS to be located across southern KS early Saturday with more substantial front/cooling into the weekend. Rain chances by Saturday look slim with system quickly racing to the NE of the region. Sunday and beyond...upper ridging looks to build in early next week with a dry northwesterly flow thereafter. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ 33
Area Forecast Discussion
National Weather Service Melbourne FL
945 PM EDT Mon Apr 17 2017 .UPDATE... East-west axis of expansive Atlantic pressure ridge lies near the Florida-Georgia border and continues to sag south. Weakening/veering onshore ESE-SE flow has dropped to about 10KT in the surface-1KM layer. 3.9UM IR satellite imagery shows large swath of higher-based stratocu/lower based altocu (6-8KFT), which formed over the southern third CWA in weak upglide and pancaked up against the 770-750MB cap, beginning to break up. Local radars show a few piddling light rain showers over the interior SW peninsula dying off, with nothing of note upstream over the Atlantic, even offshore SE Florida. Current temps in the U60s-L70s north/inland and M-U70s central-south coast. Remainder of tonight...flow should be light enough to allow boundary layer to decouple over all areas, resulting in min temps across most areas to drop into the L60s, with a few U50s north/inland and some M60s along the immediate Treasure Coast. threat for localized dense smoke/fog mixture will exist near any of the many smoldering fires across the CWA. Commuters are urged to check for road conditions and potential road closures near the problematic spots over the past week or so. Current forecast, which also shows a small chance for coastal showers for the southeastern 3 counties, looks fine. && .AVIATION...VFR. Localized dense mix of smoke/mist should be confined to areas away from local forecast aerodromes. && .MARINE...Current buoy and C-MAN reports indicate winds AOB 10KT with seas 3-4FT in an 8-9sec period swell. CWF looks spot on. && UPDATE/AVIATION...Cristaldi DSS/IMPACT WX...Weitlich && ...Only Meager Rain Chances Through Late Week... Tuesday... RAP analysis shows mid lvl troffing over the GOMex has eroded the wrn flank of the ridge aloft, mean H85-H50 flow has shifted to S/SW AOB 5KTS. This weakness in the ridge will allow a pocket of enhanced moisture over south FL to works its way north into the Treasure Coast/Lake-O region by daybreak Tue. However, while the strength of the H100-H70 ridge has weakened, the definition of its anticyclonic curvature remains distinct clear back to the TX coast. Position of the ridge axis will limit the ability for low lvl moisture to work its way much farther north than the Lake-O region. At the same time, indications of any meaningful mid lvl short wave energy or upr lvl jet development overhead thru Tue evng are weak at best. As a result, the 17/12Z GFS MOS PoPs appear way overdone acrs the Treasure Coast/Lake-O region. Will undercut by a good 20-30pct, limiting PoPS to areas south of Cape Canaveral and the Orlando Metroplex...capping at 30pct. No change in airmass...max temps should be near climo avg...L80s along the coast and M80s inland. Wed-Thu... More of the same continues. High pressure over the western Atlantic is forecast to keep low-level flow east to southeasterly. Air mass continues to be too dry for any sort of decent precipitation chances with MOS guidance advertising generally 10-15 percent PoPs in most areas. Have only included a slight chance of showers for Brevard county southward over toward southern Okeechobee on Wednesday afternoon and evening. Overnight Wednesday into Thursday only have a slight chance of showers for the immediate Treasure Coast. Amounts will be very light. High temperatures will be low 80s near the coast and mid 80s inland. Lows will be mid 60s near the coast and lower 60s inland. Fri-Mon... Axis of Atlantic surface ridge axis will extend over central Florida through Sat, then the GFS and ECMWF show the western end of the ridge breaking down on Sunday as a frontal trough approaches. Subsidence and very dry air are forecast over the area on Friday then the GFS indicates a narrow ribbon of moisture working in from the east/southeast on Saturday. This moistening looks iffy as the ECMWF remains quite dry, but will retain the small POP from the previous forecast for the Treasure Coast. On Sunday, there looks to be a chance for sea breeze convection ahead of approaching frontal trough, though northward transport of moisture is still somewhat questionable. On Mon, the GFS shows a band of slightly higher frontal band moisture moving across the area. Though frontal convergence is forecast to be weak, a bit cooler temps aloft associated with an approaching shortwave trough may lead to a chance of storms. It`s way too far out in the forecast to put a lot of faith in exact model solutions and will keep POPs Sun-Mon around 30 percent and not include thunder yet. Temps will continue above normal with highs mostly in the upper 80s inland and reaching the mid 80s along the coast by Saturday. && .AVIATION...Thru 18/18Z. Sfc winds: Thru 18/00Z...E/SE 8-12KTS...ocnl G18-22KTS S of KVRB. Btwn 18/00Z-18/03Z...bcmg E/SE 4-7KTS. Btwn 17/03Z-17/06Z...bcmg vrbl E/SE AOB 3KTS. Btwn 18/12Z-18/15Z...bcmg E/SE 8-12KTS. Vsbys/WX/Cigs: Thru 18/12Z...E of KMLB-KOBE areas CIGS btwn FL030- 040 slgt chc MVFR shras. Aft 18/12Z...S of KISM-KMLB slgt chc MVFR shras...S of KGIF-KVRB chc MVFR shras. && .MARINE... Tonight-Tuesday...High pressure ridge centered south of Bermuda and extending west acrs the FL Panhandle will maintain a light to gentle E/SE breeze acrs the area...locally moderate along the Treasure Coast Tue aftn as the onshore flow promotes the formation of an Atlc sea breeze. Seas 3-4FT nearshore and 4-5 feet offshore early this evng...subsiding to 2-3FT nearshore and 3-4FT offshore and in the Gulf Stream by daybreak Tue. Slgt chc of shras south of Cape Canaveral and in the Gulf Stream. Wed-Thu...High pressure over the western Atlantic will remain north of the waters and maintain a east/southeast wind flow. Speeds look close to 10 knots in the north and 10-15 knots in the south. Seas mainly 3-4 feet. Fri-Sat...Surface ridge axis is forecast to settle across central Florida. This will keep the gradient flow around 10 knots. The daily sea breeze and nocturnal marine wind increases will produce speeds 10-15 knots. Overall, conditions look good with seas 2-3 feet. && .FIRE WEATHER...Ridge axis over the FL panhandle will maintain an E/SE sfc/transport flow acrs central FL thru midweek. This should keep aftn min RH values AOA 40pct over the interior and AOA 50pct along the coast. However, the prospect for any significant rainfall is low through late week. Dry soil and associated drought indices will continue their slow, steady climb. Winds at night will be light and the low level inversion will promote trapping of smoke near the surface and continue to exacerbate visibility problems on some roadways near smoldering fires. && .PRELIMINARY POINT TEMPS/POPS... DAB 61 80 65 80 / 0 10 10 10 MCO 62 85 65 85 / 10 10 10 10 MLB 63 79 68 80 / 10 20 10 20 VRB 63 79 67 80 / 20 20 10 20 LEE 62 86 65 86 / 10 10 0 10 SFB 61 84 64 84 / 10 10 10 10 ORL 62 85 65 85 / 10 10 10 10 FPR 63 79 66 81 / 20 20 10 20 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$
Area Forecast Discussion
National Weather Service Raleigh NC
1002 PM EDT Mon Apr 17 2017 .SYNOPSIS... A cold front will drop southward into central NC overnight. This front will stall in vicinity of the SC border through late Tuesday, then head back to the north as a warm front Tuesday night and Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 1002 PM Monday... Surface cold front and H8 trough will drop slowly south,in back-door fashion, settling near the SC state line by daybreak. Broken band of pre-frontal showers and storms will continue to move east-southeast through the Sandhills and coastal plain over the next couple of hours. Loss of daytime heating and cooling from convective outflow has worked in tandem to stabilize the boundary layer. Thus, once the aforementioned convective band exits the forecast area in the next 2 to 3 hours, any re-development along the southward sinking cold front should primarily be in the form of showers overnight. Low level nely flow will gradually advect a cooler air mass into central NC overnight. Thus should see minimum temps vary from the mid 50s far north to 60/lower 60s south. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... As of 355 PM Monday... A hybrid cold air damming scenario unfolds Tuesday as northeast flow near the surface advects a cooler more stable air mass into our region during the morning. A few thousand feet above the surface, a swly flow will maintain enough lift to produce overcast skies. This set-up will be more pronounced across our western areas as low level easterly flow will bank up against the higher terrain. This should result in overcast skies and much cooler conditions. Forcing does not appear strong enough for widespread precipitation, though expect a few showers to occur in vicinity of the stalled sfc boundary. Enough dry air may work its way ne into our northern coastal plain counties to result in partial sunshine in the afternoon. Thus, should see the warmest high temps Tuesday across the northeast third of the forecast area with temps 65-70. Overcast skies across the west-southwest will hold max temps in the low-mid 60s. A mid level s/w approaching from the west will enhance the sly flow above the stable surface layer Tuesday night. This overrunning set- up should cause scattered showers to blossom over the sw half of central NC, especially overnight Tuesday night. Expect a diurnal change in the temperatures of no more than 4-6 degrees Tuesday night across the sw half while temperatures across the ne will cool after sunset under variably cloud skies. && .LONG TERM /Wednesday through Monday/... As of 310 PM Monday... Wed/Wed night: Models depict the gradual erosion of the low level stable pool during the day, although given that the NAM/GFS/ECMWF all show a subtle mid level perturbation shifting into the area from the west, initiating precip over western/central/southern NC, history tells us that the models may be too fast to erode this cooler surface air mass, even in the south. Will trend temps a shade under statistical guidance, with highs ranging from the mid 60s NW to the lower 70s SE. Dynamic forcing for ascent will overall be small given the weak mid level flow resulting in minor DPVA, and upper divergence will also dwindle as it heads east across NC during the day. But PW is projected to exceed 1.3", highest SE, with weak steering flow potentially leading to slow-moving cells generating elevated localized rainfall, along and ahead of a weak 850 mb trough moving NE across the region. Expect good chance to likely shower coverage areawide, highest in the western CWA, during the first part of the day, shifting into SE sections and slowly decreasing during the afternoon as lift mechanisms decrease, followed by largely dry conditions overnight as the mid-upper levels dry a bit and an in situ mesohigh forms over the western Carolinas. Areas of stratus are likely Thu night with strengthening 925 mb moisture transport within and just above the stable depth. Lows in the upper 50s to near 60, resulting in a diurnal temp range of less than 10F across much of the Piedmont. Thu/Thu night: We should finally see erosion of the stable pool Thu, as 850 mb winds become northwesterly as the 850 mb ridge becomes more W-E oriented and settles over southern GA. Very warm temps will return within SW low level flow, ahead of the cold front moving through the OH Valley, and weak flat mid level flow combined with downslope warming at 850 mb should allow for fair skies and some decent insolation. With a general lack of lift mechanisms, low deep- layer shear, and unimpressive mid level lapse rates, a dry forecast is favored, with only isolated chances in the SE due to a possible inland-moving sea breeze, and in the NW with terrain-affiliated convection shifting off the mountains. Continued dry Thu night ahead of the incoming front. Highs in the mid 80s and lows in the lower to mid 60s. Fri through Mon: Looking like a trend to stormier conditions in this period. The cold front to our NW early Fri will be tied to a northern stream trough crossing the Great Lakes and Northeast Thu night through Sat, leaving a weak longwave ridge over the Southeast states and Carolinas early in the period, which should somewhat limit the southward progression of the cold front through the Carolinas, despite a strong surface low associated with the mid level low and a cool high pressure building in behind it. I tend to favor the ECMWF, which stalls the front near the NC/SC border, over the faster and farther-south frontal passage of the GFS. Expect good shower/storm chances with frontal approach Fri afternoon/evening, followed by a short relative lull in precip late Fri night into Sat. The next potent mid level wave, moving onto the West Coast Wed night, is projected to deepen over the central CONUS on Sat, then amplify over the Ohio Valley/Mid South/Gulf States Sat night/Sun and over the Eastern Seaboard Sun night/Mon (although its strength depends greatly on how much phasing takes place with the northern stream, a factor that is difficult to determine with any confidence this far out). Storm coverage and strength should both be on the increase Sat night/Sun into at least early Mon, with the retreating stable pool/wedge air mass complicating matters with its enhanced low level vorticity field, yielding a potential strong to severe storm risk, if enough instability can be achieved. We should see a decreasing trend in showers/storms west to east during Mon as the trough axis shifts to our east, with cooler high pressure building in behind the surface low and frontal complex. Expect above normal temps and good shower/storm chances Fri, especially east of Highway 1. Near normal temps Sat (cooler N than S) with low to no pops. Warm SE and cool NW Sun with the approaching occluded strong storm system, with a trend to likely pops for much of the area Sun into Sun night, tapering west to east Mon with below normal highs. -GIH && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 840 PM Monday... 24 Hour TAF Period: The main area/broken line of showers and storms is currently pushing eastward through the southern and eastern portions of the area, currently affecting KRWI and soon to affect KFAY. Brief gusty winds to 25 kts or so are possible with the main outflow. Otherwise, MVFR/IFR cigs and/or visbys are expected with the main band/line. Additional isolated to scattered showers will be possible as the low level frontal zone moves through the area very late this evening into early Tuesday morning. A period of at least 2- 4 hours of IFR cigs will be possible behind the main front. The surface cold front is expected to push through SC into southern GA on Tuesday. The latest NAM and GFS soundings, along with the HRRR show drier air in the low levels now pushing into the area on Tuesday morning with a return to VFR conditions at all sites by late morning/early afternoon at the latest, with locations across the north possibly VFR in the 08-12Z range. The latest hi-res models now show dry weather expected for Tuesday as well. Outlook: Aviation conditions are expected to deteriorate Tuesday night as the low level boundary begins to lift northward, leading to an increase in shower activity and lowering of ceilings back into the MVFR/IFR range. An unsettled weather pattern is expected Wednesday through Saturday. This will lead to periods of sub VFR ceilings and visibility, along with chances for showers and isolated thunderstorms. At this time, the highest threat for adverse aviation conditions appear to be Wednesday and Friday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...CBL SHORT TERM...WSS LONG TERM...Hartfield AVIATION...BSD/WSS
Area Forecast Discussion...UPDATED
National Weather Service Reno NV
600 PM PDT Mon Apr 17 2017 .UPDATE... Deep moisture continues to stream into the Sierra, but the overall pattern remains somewhat disorganized. That said, rain rates are approaching 1/4" per hour and have increased amounts in the Tahoe Basin and have also increased the precip threat there this evening. Further east, there is a bit of shadowing along the 395 corridor, but lift increases along and east of a line from the Pah Rahs to the Wassuks in Western Nevada. Rain is falling in Fallon and Lovelock already. Radar trends show it increasing there and the HRRR also keeps the rain going there through the evening. Updated the rain chances there to near 100% this evening although amounts will be light, around a tenth of an inch. Otherwise, no more updates for now. We will continue to monitor the precip rates and coverage to make any other adjustments later this evening if necessary. Wallmann && .SYNOPSIS... Breezy conditions continue with the next weather disturbance producing additional valley rainfall and higher elevation snowfall tonight through Tuesday. After a final weak system Wednesday night and Thursday, a drier trend with a significant warm up is expected heading into the weekend. && .PREVIOUS DISCUSSION... /Issued 236 PM PDT Mon Apr 17 2017/ SYNOPSIS... Breezy conditions continue with the next weather disturbance producing additional valley rainfall and higher elevation snowfall tonight through Tuesday. After a final weak system Wednesday night and Thursday, a drier trend with a significant warm up is expected heading into the weekend. SHORT TERM... An upper disturbance off the central and northern California coast will move into northeast California and Nevada late tonight. Ahead of the main forcing, a brief period of warm air advection rain is shown in simulations for this evening in west-central and central Nevada (including Pershing and Churchill Counties) near and north of a fairly subtle low-level boundary there. The boundary can be evidenced per wave clouds, with the boundary near the southern edge of the clouds in visible imagery. Moving onto late tonight, the aforementioned upper disturbance will move into the region. This is shown in simulations to tighten up the low-mid level thermal gradient over western NV and the northern Sierra, with precipitation breaking out along the boundary as the main forcing arrives late tonight. Simulations have zeroed in on the I-80/Highway 50 corridors or slightly farther north for the best shot at heavier precipitation amounts tonight, with between 0.10 and 0.25 inch certainly possible for western and west-central NV through tonight (and a touch more possible Tuesday morning). Confidence is high in this band of precipitation developing tonight...but still medium on the exact location of heavier precipitation. As far as snow levels/Sierra impacts tonight and Tuesday morning, this will be mainly a high elevation snow event. Currently, snow levels are running from 7500 feet to about 9000 feet from Plumas County to Mono County, respectively. The snow level should not come down much through the bulk of tonight, with the upper wave pushing most of the cold air into the Pacific Northwest. There should eventually be a slow lowering of snow levels on Tuesday morning to around Donner Summit/Pass level so there is a small window where some slush could accumulate on I-80 over that pass. However, it should melt off quickly by mid-morning. Farther north into northeast CA, it does not look like snow levels will fall quite far enough to impact higher roads there (including Highways 36 and 44 west of Susanville). As the upper wave moves into Nevada on Tuesday, the boundary/front will get a push south with precipitation expected to spread into eastern Mono and Mineral Counties. The NAM and GFS even hint at afternoon convection in the Basin and Range (east of Fernley) on Tuesday, which could bring very small hail pellets and an isolated lightning strike. While a couple small storms are possible Tuesday afternoon, the probability remains too low to mention in the forecast. Tuesday night and Wednesday, brief drying moves into northeast CA and western NV with temperatures on Wednesday rebounding to around average. Snyder LONG TERM...Wednesday night and beyond... The last in a series of shortwaves is forecast to move quickly through northern CA and northern NV Wednesday night and Thursday, with the best potential for a short period of precipitation from the late night through early morning hours. There will be some cooling with snow levels likely dropping to 5500-6000 feet around the Reno-Tahoe region, and near 5000 feet for northeast CA. Moisture will be limited with current model QPF projections around 0.25 inch along the Sierra crest from Tahoe northward, with lesser amounts near the crest in Alpine-Mono counties. For western NV, the best chance for measurable rainfall will be from I-80 northward with amounts 0.10 inch or less. Snowfall associated with this system will generally be light, mainly 1-3" around Tahoe-Truckee and northeast CA above 5000-5500 feet. Some slick/slushy travel conditions are possible into Thursday morning around Tahoe (mainly near or above 6500 feet) and higher elevation roads in northeast CA (Fredonyer/Yuba passes and CA-44 west of Susanville). For Thursday, lingering showers will taper off during the daytime hours with brisk west to northwest winds keeping cool conditions over the region. Choppy conditions are possible on Pyramid Lake Thursday afternoon-early evening. By Friday, a ridge of high pressure will build over CA-NV, leading to dry conditions, lighter winds and a quick warmup with highs in the mid-upper 60s for most lower elevations and 50s near the Sierra. For the weekend into early next week, another trough moving quickly across the Pacific Northwest will flatten the ridge a bit with some increase in cloud cover mainly north of I-80 by late Saturday into Sunday. Light rain showers are possible Sunday from Susanville- Gerlach northward, but overall impacts on outdoor activities should be minimal. Further warming is expected as temperatures will be 10-15 degrees above average each day, except slightly cooler north of I-80 Sunday due to the weak trough passage. Moderate afternoon and evening breezes are expected through Monday. Looking ahead past Monday, a weak trough passage across the Great Basin may bring a round of showers and some cooling Monday night into Tuesday. This pattern of weak inland trough passages could remain in place through much of next week, preventing a significant warmup but precipitation amounts should be light. MJD AVIATION... For tonight into Tuesday, a stronger and wetter shortwave will enhance precipitation with a continuous period of terrain obscurement along the eastern Sierra and widespread MVFR conditions for KTRK/KTVL, eventually spreading south to KMMH. Snow levels will remain above Sierra terminals so snow accumulations are unlikely. Western NV airports will see periods of light to occasionally moderate rain with showers, but conditions should remain mostly VFR with higher mountain tops possibly becoming obscured. Tuesday afternoon, there is a low (10%) chance for thunderstorms over west-central Nevada (well east of KRNO). If any storms form, small hail (less than 1/2") and a few lightning strikes will be possible. Surface winds will be fairly modest through Tuesday (gusts 20-25 kts) but Sierra ridges will continue to have gusts 60-70 kts. Some light to moderate turbulence will remain possible. Hohmann/Snyder && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit... http://weather.gov/reno
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
521 PM MDT Mon Apr 17 2017 .SHORT TERM...(This Evening Through Tuesday Night) Issued at 242 PM MDT Mon Apr 17 2017 Upper ridging across the region is giving way to a strong shortwave cross the northern Rockies into central MT. A secondary weak shortwave is pushing across northeast WY and approaching the Black Hills. This secondary wave is bringing clouds to the area at this time. Deep southerly low level flow continues across the CWA with temperatures reaching into the 50s and 60s. Instability across the Nebraska panhandle is sliding northward into southwest SD. Models are showing SBCape values reaching 1500 j/kg over the panhandle which will slide northward into southwest SD over the next couple hours. The HRRR is showing storm development associated with the weaker wave initiating in the late afternoon hours over parts of northeast WY...then sliding eastward over the southern Black Hills into southwest SD. There is enough shear for one or two supercells to develop. The toughest hinderance to storms will be the cap in place...but could see a few storms break through as the wave crosses the area. Storms will move E/NE into central SD this evening while a secondary area of showers develops just ahead of the main wave across northwest SD and a surface cool front pushing through. Upper ridging and dry weather will return Tuesday behind the departing wave. Highs will be in the 60s to low 70s...with the warmest spots across south central SD. A broad upper trough will push into the western CONUS with a strong upper wave across the Great Basin. This system will bring increasing clouds late Tuesday...and chances for precip late Tuesday night. .LONG TERM...(Wednesday Through Monday) Issued at 242 PM MDT Mon Apr 17 2017 Rain and showers will continue on Wednesday, with decent precip amounts expected in some areas by the time the system exits Wednesday evening. Models continue to show QPF amounts of close to an inch or more. The 12z GFS shows some parts north of the Black Hills reaching close to 2 inches. Some snow accumulation is possible across the highest elevations of the Black Hills Wednesday morning, but this would likely be limited to the highest elevations where up to two or three inches of accumulation are possible. Cool conditions on Wednesday, with highs in the 40s and lower 50s. A brief break from pcpn is expected on Thursday before the next system digs southeast from the Northern Rockies to the Central Plains Thursday night and Friday. Models have continued the northward trend. This system will bring rain to the area...though the higher Black Hills could see another inch or two of snow. Drier weather is then expected for the weekend as an upper ridge builds across the region. && .AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening) Issued At 518 PM MDT Mon Apr 17 2017 Gusty southerly winds will shift to the west/northwest this evening as a cold front moves through. Winds could gust to near 50 knots over NE WY along the front. Showers and thunderstorms will develop and move from west to east across the area this evening along the cold front, mainly from around the Black Hills NE. Local MVFR/IFR conditions expected with the thunderstorms, along with possible gusty winds and small hail. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ SHORT TERM...13 LONG TERM...13 AVIATION...JC