Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/05/16


Area Forecast Discussion
National Weather Service Bismarck ND
1039 PM CDT SUN SEP 4 2016 .UPDATE... Issued at 1037 PM CDT Sun Sep 4 2016 Cancelled the watch as the threat for severe storms has ended across the James River Valley. Otherwise no change to the forecast. UPDATE Issued at 946 PM CDT Sun Sep 4 2016 Models have backed off on pops west late and now not till after 12Z so scaled back during the overnight period west. Otherwise, widespread showers and thunderstorms continue over my southeastern counties. Still ample shear and instability though do think the overall severe threat has diminished. Feel better leaving the watch as is for now with this update given SPC mesoanalysis, but am confident we can let it go before midnight. UPDATE Issued at 742 PM CDT Sun Sep 4 2016 Greatest threat for thunderstorms remains over the far south central and into the James River Valley this evening around a stationary frontal boundary. Thus far no severe weather in my southeast, though instability and shear parameters still elevated enough for an organized storm or two to develop for the next few hours, so will maintain the Severe Thunderstorm Watch as is with this update. Tampered down pops central and west until the overnight when the next wave lifts towards the Northern Plains. UPDATE Issued at 500 PM CDT Sun Sep 4 2016 Quick update to issue a Severe Thunderstorm Watch for Logan, LaMoure, McIntosh, Dickey Counties. && .SHORT TERM...(This evening through Monday) Issued at 246 PM CDT Sun Sep 4 2016 The main focus for the short term is potential severe thunderstorm chances this afternoon and evening across the southern James Valley. A trough centered just east of Bismarck this afternoon will be the focus for thunderstorm development. A slight clear patch in the clouds across south central North Dakota has allowed temperatures to climb into the 70s. The latest HRRR run indicates convective initiation around 6 PM across far south central North Dakota. The bulk of the instability should remain along and just south of the ND/SD border. However, storm motion could bring stronger storms across northern South Dakota into Emmons, McIntosh and Dickey Counties later this evening. Plenty of moisture and shear will be present along the front to sustain storms once they develop. The main trough will exit the area tonight, with a slight break in the shower/thunderstorm activity overnight before another wave moves into western North Dakota Monday morning. Very high PWAT values and training storms could create some hydro issues later tonight with rainfall rates greater than an inch an hour. Thankfully impacts should be short-lived as a break in the action is expected overnight. .LONG TERM...(Monday night through Sunday) Issued at 246 PM CDT Sun Sep 4 2016 The rest of the week looks cooler and active as a broad cyclonic flow will remain over the northern plains with several shortwaves moving through. The most models highlight Wednesday for the best chance for showers this coming week as a pronounced shortwave moves through. There is a chance for showers and thunderstorms through Saturday. Monday will be the coolest with upper 50s northwest and 60s southeast. Then highs will be in the 60s to lower 70s for the remainder of the week. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 742 PM CDT Sun Sep 4 2016 Thunderstorms will impact the James River Valley this evening including KJMS. Elsewhere mainly isolated showers this evening until after midnight when we will see increasing chances for showers west then into the central towards 12Z. MVFR cigs with localized IFR cigs area wide through much of the 00Z period. Also potential for reduced visibilities in precipiation and/or fog. && .BIS Watches/Warnings/Advisories... NONE. && $$ UPDATE...MM SHORT TERM...AJ LONG TERM...AJ AVIATION...NH
Area Forecast Discussion
National Weather Service Grand Forks ND
939 PM CDT SUN SEP 4 2016 .UPDATE... Issued at 933 PM CDT Sun Sep 4 2016 Primary concern has transitioned from severe threat to areal flooding concerns as deep moisture convergence over the sfc boundary, which has barely moved since the 7 PM CDT update, continues to dump heavy rain from roughly a Warroad MN to Grand Forks ND to Valley City ND line. Main adjustments to grids are extending the categorical POPs well into the overnight period and also increasing QPF amounts along this band of activity. Severe threat remains well to the south however an evolving MCS over s central SD is progged by HRRR to lift through our southeastern zones in the midnight to 6 AM timeframe. Could result in eastward expansion of severe box depending on wind damage reports/potential across central and eastern SD. For now, appears threat to Ransom- Sargent-Richland counties is diminishing. UPDATE Issued at 601 PM CDT Sun Sep 4 2016 Current METARs indicate a well defined surface boundary extending from Baudette MN to Hillsboro ND to Forbes ND before extending through central SD. The eastern and southern side of this boundary, mainly over the southern RRV and west central MN, continues to have plenty solar with temps around 80. Meanwhile, the best deep layer shear remains along and west of the boundary. Main severe threat will be in southeastern ND as the boundary moves east into the area that heated out this afternoon. Slow progression of boundary will generally keep regions east of the valley out the threat area. A severe thunderstorm watch is now in effect for Ransom...Sargent and Richland counties through midnight. Have adjusted wx grids for severe wording and increased POPs to categorical across the north. && .SHORT TERM...(This evening through Monday) Issued at 305 PM CDT Sun Sep 4 2016 Forecast challenge in the short term will be T coverage/severe potential. Earlier today high resolution models struggled with current convection with RAP and HRRR doing the best of late. HRRR has improved over the last several hours leading to somewhat higher confidence on what will happen overnight. Boundary from northern valley to near JMS and into central SD will drift slowly east overnight. Clouds/rain have limited instability especially across the northern two thirds of the forecast area. Airmass becoming increasingly unstable from the far SW FA into SD. This appears to be the favored location for convective initiation later this afternoon or early evening. Convection will likely then propagate NE along the boundary during the night so it may be later before northern portions of the region from the valley west get rain. Severe threat looks to be limited to the S-SW fa. By morning boundary will be bisecting the FA from NE-SW. Convection will probably be ongoing in the am most likely over the ne fa. At prime heating front will be across the far se fa and will have to monitor for severe potential there. Across the remainder of the fa will maintain some chance pops but would not be surprised if most areas stay dry. Column steadily cools during the day with warmest readings over the far E-SE closer to the boundary. .LONG TERM...(Monday night through Sunday) Issued at 305 PM CDT Sun Sep 4 2016 An upper level wave will be moving through the region on Monday night. Models have surface low in eastern SD/SW MN Monday at 7 PM. Most models have an inverted trough/cold front extending NE from the low to the Arrowhead of MN...although the GFS is further west with the front. There will likely be some elevated instability in the SE forecast area, including the Fergus Falls and Wadena areas, Monday evening. With effective shear of 40-50kts and MUCAPEs of 1500-3000 J/kg, a threat for severe storms will exist. A sharp theta-e gradient will exist along the cold front...with a strengthening low level jet by 10 PM. The front gets a nudge eastward later Monday night as the upper wave passes to the north. Tuesday looks generally dry with highs in the mid 60s north to mid 70s south and partly sunny skies. Another wave will bring a chance for showers/thunderstorms on Wednesday/early Thursday. Yet another wave will affect the area on Friday. All in all the pattern looks active with highs generally in the mid 60s to mid 70s. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 601 PM CDT Sun Sep 4 2016 Thunderstorms will impact sites along and north of the Highway 2 corridor early in the evening and spread into FAR/BJI areas over the next several hours. Low MVFR/IFR cigs expected to fill in behind convection and continue through the night into late tomorrow morning. Not ideal flying conds over the next 18 hours. FAR will have a break through mid evening before cells begin impacting its aerodrome. && .FGF Watches/Warnings/Advisories... ND...None. MN...None. && $$ UPDATE...Speicher SHORT TERM...Voelker LONG TERM...Knutsvig AVIATION...Speicher
Area Forecast Discussion
National Weather Service GLASGOW MT
837 PM MDT SUN SEP 4 2016 .SHORT TERM...for northeast Montana...tonight through Tue... Update... Due to a dry boundary layer, light rain has been slower to reach the ground across parts of the forecast area than expected. Nevertheless, radar echoes are present, especially across western and central portions of the CWA. Although the steadiest rain so far has occurred over parts of southern and central Montana, the expectation is still that this activity will spread further north and east overnight and on Monday as the boundary layer reaches saturation and as forcing for ascent increases when an absolute vorticity maxima reaches the area presently indicated over southern Idaho on water vapor imagery. Overall expect widespread wetting rains to still be on track, though perhaps amounts may be somewhat lower than previous expectations given the delayed start to the event. Maliawco Previous Discussion... A large trough of low pressure aloft is entrenched over the northern Rockies region which places northeast Montana in a steady moist SW flow aloft. Unfortunately, the precipitation models have a difficult time pinning down the variable rain bands that result from these dynamics. The HRRR and EC and the GEM seem to be the more accurate models while the GFS and NAM are of next to no help at all. Tried to blend the best consensus I could find for all adjustments to the forecast. Because of the variable nature of these rain showers, would not be surprised if some locations accumulate over an inch of rain while others only receive a trace of rain. Tonight: The first wave of precipitation continues to do what it has done for most of the day already - concentrate more over our southern zones, making feeble attempts to extend northward toward the international border only to peter out to just a trace. Monday: The closed upper low center becomes an open wave and moves directly over northeast Montana. The models improve just a bit with consensus on the precip amount and placement. Best chances for accumulating rain will be between Monday morning and Monday afternoon and could easily be a bit more widespread than what we experienced today. Monday night the upper level wave weakens and lifts northeastward over Saskatchewan and ends the rain from SW to NE across many locations by the overnight hours. Tuesday as the flow becomes more zonal, only lingering chances for trace to minimal amounts of rain can be expected over our NE zones. Expect temperatures around 20 degree below averages for this time of year through Tuesday morning as the cold continental air mass from Canada continues to hold sway. BMickelson .LONG TERM...Tue night through Sun... Going forecast has a good handle and 12z models didn`t provide much need for change. At the end of the period, a disturbance brushes the area from the north and could knock temps dwon along with bringing the chance of showers. TFJ Previous Discussion... Cool conditions expected from midweek through next weekend with longwave upper trof over North America. Lowered heights and the southward shift of the jet will keep temperatures below normal for the period. Main chance for rain will be with a shortwave trof pushing through the northern Rockies midweek. System tracks along the Canadian border with thunderstorms possible ahead of the low Tuesday night into Wednesday. A second wave follows on Thursday but models differ on how far south it dips so uncertainty is increased regarding rain chances. Ebert && .AVIATION... A large upper level trough will continue to dominate the weather pattern for the next 24 hours. This will bring isolated areas of light rain to the region. Expect VFR conditions with areas of MVFR in heavier rain. Wind will continue out of the Northeast under 15 knots. Proton && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ weather.gov/glasgow
Area Forecast Discussion
National Weather Service Hastings NE
711 PM CDT SUN SEP 4 2016 .UPDATE... Issued at 659 PM CDT Sun Sep 4 2016 Diurnally driven strong to severe thunderstorms across northwest Kansas will slide northeast into our north central Kansas and south central Nebraska counties this evening. These storms will likely be more scattered in coverage south of interstate 80 and there is some question as to how well they will hold together after sunset, but large hail, damaging winds, and flash flooding will be possible with these storms. Additional strong to severe thunderstorms are expected to form on the nose of the strengthening low level jet between 9pm and midnight with the greatest coverage of these later developing storms likely north of I-80 and even more so along and north of hwy 92. && .SHORT TERM...(This evening through Monday) Issued at 227 PM CDT Sun Sep 4 2016 We have a chance for thunderstorms this evening. There will be a couple thousand J/kg of most unstable CAPE (upwards to near 4,000 per the NAM) with decent bulk (0-6km) shear around 45 knots to support updrafts capable of large hail around half dollar size (or larger) and thunderstorm wind gusts around 60 mph. Initially, there is a chance for some of the early thunderstorms to develop into supercells and there will be a small threat for tornadoes before storm mode goes more into a cluster of storms. The higher instability is across western portions of the county warning area...and I believe thunderstorms will impact our area here initially. A surface trough is currently in place across western parts of the Central Plains. Thunderstorms are already developing across eastern Colorado. The HRRR is initializing well and capturing this in the 19Z run. The HRRR brings these storms into western parts of our area as early as 6pm. A flood warning is in effect for portions of north central Kansas until 730 pm tonight. Please see the latest Flood Warning product for more information. Chances for additional rainfall look more favorable for areas north of the flooded area. .LONG TERM...(Monday night through Sunday) Issued at 227 PM CDT Sun Sep 4 2016 Throughout the extended there are multiple chances for thunderstorms. Some of these chances could produce storms capable of strong to severe weather. The Storm Prediction Center has us outlooked the next several days in a row. Monday is really the only day that doesn`t look as favorable for thunderstorms...and really the only dry period in the forecast until next weekend. Any additional rainfall in those areas that have already received a lot of rainfall could potentially be prone to more flooding. This will need paying attention to over the course of next week, in particular north central Kansas, which doesn`t need anymore rainfall. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday evening) Issued at 659 PM CDT Sun Sep 4 2016 The primary aviation concern will center around both strong low level wind shear...as well as thunderstorms this evening through tonight. Some of the thunderstorms in the area could be strong to severe, but too early to say for sure if these more scattered thunderstorms will directly impact the terminals or not. The most likely time for thunderstorms will be between 9pm and 1am. The low level wind shear will be rather strong through a majority of the overnight hours. && .GID Watches/Warnings/Advisories... NE...None. KS...None. && $$ UPDATE...Wesely SHORT TERM...Guerrero LONG TERM...Guerrero AVIATION...Wesely
Area Forecast Discussion
National Weather Service Goodland KS
954 PM MDT SUN SEP 4 2016 .UPDATE... Issued at 954 PM MDT Sun Sep 4 2016 Finalized update to cancel severe thunderstorm watch and flash flood watch early. Storms have dissipated and are no longer anticipated for the rest of the night. && .SHORT TERM...(This evening through Monday) Issued at 152 PM MDT Sun Sep 4 2016 Main concerns once again are thunderstorm coverage and heavy rainfall/flash flooding/flooding concerns. Confidence is lowered due to poor performance of models with yesterdays event, and some model disagreement on how the evolution of tonight will pan out. Air mass remains very moist and unstable. Area soundings this morning showed precipitable water values near 1.5 inches. A persistent instability/theta-e axis remains draped across the center of the area from southwest to northeast. There one surface boundary near the western end of the area and another draped over the eastern end. PV/Satellite analysis show a decent shortwave moving in from the southwest. At the same time all the models show a right rear quadrant of the upper draped across the area. The shortwave and jet lift move across the area from west/southwest to the east through the evening. Where the models are having trouble is where to put the development. Some have it in the west and others in the east. Considering that currently thunderstorms have developed and are now moving into the western portion of the area, that looks to be the way to go. Current trends favor the Rap and Hrrr. So expect scattered thunderstorms producing heavy rainfall to move across the area once again. Due to instability and shear in place, severe looks likely as well. All in all a similar setup to the last few days. So will keep the flash flood watch going with the northeast portion of the area extremely susceptible to more rainfall and flooding. For Monday...with exception of jet lift, setup looks similar tomorrow. Instability/moisture axis remains in the same place. So more thunderstorms will be expected along with locally heavy rainfall and possible severe. .LONG TERM...(Monday night through Sunday) Issued at 145 PM MDT Sun Sep 4 2016 Trough extends down out of western Canada all the say into the southern portions of California Monday night into Tuesday morning with high pressure over the southern Mississippi Valley. The surface boundary draped from southwest to northeast across the CWA continues to remain nearly stationary as we head through the day on Tuesday. This will provide a focus for scattered thunderstorm activity through the afternoon and into the evening once more with only moderate instability and relatively weak upper level support provided by passing shortwaves. A cold front will push through the region later on Tuesday with slightly drier air behind it that will linger into the middle to end of the week. Dry weather prevails through Saturday with another, stronger cold front traversing the region on Friday. Due to dry air in place preceding the front, PoPs will be low across the CWA and should remain east of the region. Afternoon high temperatures will be in the middle to upper 80s Tuesday with a few 90 degree locations in the eastern portions of the CWA. Slightly cooler highs prevail for Wednesday and Thursday with highs in the middle 80s. Cold frontal passage will cool things off a bit heading into Friday and Saturday with afternoon high temperatures reaching the upper 70s to lower 80s. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 520 PM MDT Sun Sep 4 2016 For KGLD...Mainly VFR conditions with scattered low/mid clouds. VCTS 00z-03z...3sm br 10z-13z and VCSH 17z Monday onward. Winds SE 10-20kts becoming SSW by 03z Monday at 15-25kts. LLWS 220@50kts from 03z-10z. For KMCK... Mainly VFR conditions with scattered low/mid clouds. VCTS 00z-03z...3sm br 10z-13z and VCSH 17z Monday onward. Winds SSE 10-20kts w/ gusts to 25kts after 17z Monday. LLWS 200@50kts from 03z-10z. && .GLD Watches/Warnings/Advisories... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...RRH SHORT TERM...BULLER LONG TERM...TL AVIATION...JN
Area Forecast Discussion
National Weather Service Miami FL
911 PM EDT SUN SEP 4 2016 .AVIATION... VFR conditions to prevail at all TAF sites. Models indicate increase in moisture and large scale low level convergence over the area by morning with gradually increasing shower chances. Thunder also possible in the vicinity of the terminals by midday Monday as daytime heating decreases stability. && .PREV DISCUSSION... /issued 812 PM EDT SUN SEP 4 2016/ UPDATE... A loop of water vapor imagery shows a distinct moisture front dropping from north to south down the central Florida peninsula. Small scale models continue this trend, but weaken the storm activity as it moves into our CWA. Chance pops appears warranted for areas around Lake Okeechobee through early tonight. Deeper moisture will also filter in from the east late tonight, thus increasing chance showers and thunderstorms along portions of the east coast metro and inner coastal waters by early morning. With an abundance of moisture and instability over the region Monday afternoon into the evening, likely pops was maintained for nearly all land areas. Otherwise, all other forecast variable appear on track. PREV DISCUSSION... /issued 441 PM EDT SUN SEP 4 2016/ SYNOPSIS... Showers and thunderstorms will continue across the northern interior and the Gulf coast regions this evening. Otherwise, dry conditions should prevail for the east coast metro. Tomorrow, an increase in moisture will ramp up shower and storm activity area wide. As high pressure builds over the Atlantic by mid week, a typical summer weather pattern should return to South Florida. With a return to east to southeast flow, scattered afternoon/evening convection will mainly affect the interior and Gulf Coast. DISCUSSION... Water vapor imagery continues to show a band of elevated mid and upper level moisture stretching to the south and southwest from post Tropical Storm Hermine down toward the Gulf of Mexico. However, over South Florida, dry/sinking air was observed. This subsidence has acted to keep convection at bay this afternoon. The 12Z KMFL sounding indicated a distinct dry layer around 700 mb with a capping temperature inversion. By late afternoon, light east winds in the lower levels will allow for a sea breeze convergence over the western interior. Both the HRRR and HiRes WRF generate storm activity over a general area stretching from Naples to Lake Okeechobee into the evening. This has been reflected well in the grids. By late tonight, the 12Z GFS indicates a moisture surge pushing across the Atlantic waters and towards the East Coast metro. Thus, pops will increase tonight into tomorrow morning along the Atlantic coast. By Monday, deeper moisture will advect into the region from both the north and east, creating the potential for an active day of showers/storms area wide. With the swath of moisture lingering over South Florida through late Monday, the chance of showers and storms will continue into the night. The main threats from the strongest storms will be brief heavy rain, gusty winds, and frequent cloud to ground lightning. Heat index on Monday will be peaking between 100-104 degrees, with highest values over southern Collier County. Tuesday through the weekend, high pressure building over the Atlantic will bring a return to the more typical summerlike pattern to South Florida. Highest chances of afternoon storms will be over the interior and Gulf Coast. During the nights, activity may shift back towards the Atlantic coast. Beaches: From Monday afternoon through Wednesday, models project a 3- 4 foot 11-12 second swell, generated by Hermine, to drop southward down our Atlantic coastal waters. This scenario would create elevated surf along the Atlantic beaches and an enhanced rip current risk. Will continue to monitor NWPS output as the swell approaches. MARINE... As a high pressure ridge continues to build across the Atlantic through late week, winds will turn light and easterly. There will be a chance of showers and thunderstorms throughout the period. A 11-12 second swell, generated, by Hermine, will push south through the Atlantic coastal waters Monday afternoon through early Wednesday. Seas could peak around 3-5 feet east of Miami- Dade/Collier counties and 5-7 feet in the coastal waters east of Palm County. Conditions will begin to improve by late Wednesday. && .PRELIMINARY POINT TEMPS/POPS... West Palm Beach 79 90 77 87 / 20 60 40 50 Fort Lauderdale 80 89 78 88 / 30 60 40 50 Miami 80 90 78 89 / 30 60 40 50 Naples 77 91 75 89 / 40 60 30 60 && .MFL Watches/Warnings/Advisories... FL...None. AM...None. GM...None. && $$ SHORT TERM...27/JT LONG TERM....27/JT AVIATION...22/KS
Area Forecast Discussion
National Weather Service Blacksburg VA
752 PM EDT Sun Sep 4 2016 .SYNOPSIS... High pressure will remain across the region tonight into midweek as Hermine lingers off the mid-Atlantic coast over the next few days. The area of high pressure will finally give way to a cold front late in the week, which should bring the next chance for showers and storms by next weekend. && .NEAR TERM /THROUGH MONDAY/... As of 745 PM EDT Sunday... No significant changes needed at this time. Last vestiges of light rain showers associated with east-west oriented upper trough rotating through the region on the back side of Hermine dissipating and/or shifting south out of the RNK CWA. HRRR indicates little to no activity from this point forward, so have trended toward zero pops by 12Z Mon. Temperature/dewpoint readings only needed minor changes. As of 230 PM EDT Sunday... An upper level low/short wave will track across eastern Virginia and eastern North Carolina through this evening and merge with Post tropical Hermine off the Mid Atlantic Coast Monday. Today`s short wave is tracking south into very dry air and strong subsidence and will bring an increase in clouds to the piedmont into this evening. These clouds may produce a few sprinkles as the short wave passes to the east. Behind this short wave, more dry air will enter the region with abundant sunshine set for Monday. Heights increase Monday, especially across the mountains, to have temperatures warm to or just above seasonal normals (lower 80 west to mid 80s east). && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 230 pm EDT Sunday... Ridging both surface and aloft will continue to gradually assert itself from the southwest through the period between Hermine still off Delmarva and the next upstream mid level trough. Dry north to northwest flow combined with strong subsidence should keep overall pleasant weather in place with temps and dewpoints slowly rising by the middle of the week. Could also see some bands of clouds swing back across the northern/eastern counties early on pending the proximity of Hermine but too dry for any showers at this point. Otherwise mainly clear/sunny with lows Monday night in the 50s to lower 60s and highs Tuesday mid/upper 80s west to around 90 east. Should become a bit more humid Tuesday night with lows mostly upper 50s to mid 60s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 200 PM EDT Sunday... Strong upper ridging will remain in place midweek between the next upstream shortwave trough approaching from the northwest and Hermine that is still expected to be meandering off the mid-Atlantic coast. This in combination with a dry north/northwest trajectory should keep Wednesday into Thursday dry/warm before the flow aloft turns more zonal later Thursday in response to flattening upper heights. Appears may see just enough low level moisture return by Thursday evening to pop isolated convection far western ridges, otherwise keeping it dry both days with highs mid/upper 80s mountains to low 90s east. Somewhat deeper moisture returns by late in the week as added subtle height falls in conjunction with the flow turning more west/southwest should erode ongoing subsidence in place. Although most of the shortwave troffiness will shear by well to the north, looks like enough to push a weak surface cold front south toward the area Friday before it lifts back north by Saturday ahead of a bit stronger front that may push into the area Sunday. Latest models also suggest that a pre- frontal axis of deeper moisture will be over at least western sections Friday/Saturday with perhaps another band of showers/storms along the second front across the region on Sunday. Since still mostly diurnal will continue overall chance pops mainly west through the period for now. Otherwise return of humidity will make things quite muggy again given highs 80s to lower 90s, except perhaps a bit cooler on Sunday with the weak boundary around. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... As of 745 PM EDT Sunday... VFR conditions expected through the TAF valid period. East-west oriented upper trough rotating around upper low over top of T.S. Hermine will shift south of the region this evening. Associated mid-level moisture and spotty showers will shift south as well and dissipate. Ceilings have been and will continue to be VFR, trending toward SKC by 06Z and beyond, likely to continue through the remainder of the TAF valid period. Visibility will also be VFR through the TAF valid period with the exception of KLWB. Am concerned with calm winds and slightly northeast drainage, that fog may develop here after 08Z. Not going to take it down to 1/4SM FG at this time, but cannot completely rule out this possibility. For now, will stop at 1SM as confidence in fog development overall is not as high as usual given overall dryness of air mass just off the surface. Winds will continue to be NE east of the Blue Ridge to ESE west of the Blue Ridge tonight on back side of Hermine with speeds generally 5kts or less. With upper trough south to east of the area and Hermine slightly further away Monday, expect a northwest wind 5-7kts in most areas. High confidence in cigs throughout the TAF valid period. High confidence in vsbys throughout the TAF valid period, except at KLWB, where confidence is medium in the 08Z-13Z time frame. Medium to high confidence in wind speed/direction throughout the TAF valid period. Extended aviation discussion... Generally VFR conditions expected through much of the extended period as Hermine lingers off the mid-Atlantic coast for several days into the mid part of the week. This will put our area in a subsidence zone for several days. Relatively light winds and a mainly clear sky should support the development of some patchy late night/early morning fog in some of the deeper mountain valleys. As low-level moisture continues to increase throughout the week, expect late night/early morning fog/low clouds to be on the increase. A cold front will arrive by the end of the week bringing the next chance of showers and thunderstorms and any sub VFR cigs. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/RAB NEAR TERM...RAB/RCS SHORT TERM...JH LONG TERM...JH AVIATION...RAB/RCS
...Update to aviation forecast discussion...

.SHORT TERM...(This Evening through Monday) Issued at 314 PM CDT SUN SEP 4 2016 Overnight/early day convection has diminished with some lower cloud building in as low level moisture increases. Water vapor showing fast southwest flow over the Central Rockies and Northern Plains with shortwave making quick progress into western Colorado early this afternoon and scattered convection has developed ahead of it. Breezy southerly winds helping push temps tin the lower and middle 80s with dewpoints near 70. Will likely see at least isolated activity persist in western portions of the state through the afternoon. HRRR has been consistent in more of a broken line of storms forming, but even it struggles to maintain this activity into the CWA. Hard to completely rule out a stray storm making it this far east but will keep a mention out. Modest isentropic upglide resumes tonight over a 50kt south- southwest low level jet with moisture in the low-mid levels not very near saturation at any particular level. Again could see something isolated develop mainly after midnight to just after sunrise but don`t believe a mention is in order. The low level jet and high dewpoints should keep lows in the lower 70s for the most part. Stronger southerly winds, modest warm air advection from the overnight, and less cloud should allow for Labor Day highs around 90. .LONG TERM...(Monday Night through Sunday) Issued at 314 PM CDT SUN SEP 4 2016 For the extended period, the general idea from the models is for southwest flow aloft to transition to more of a of a progressive pattern with shortwave troughs periodically moving through the northern and central plains by the end of the work week and the weekend. But before the transition, increasing moisture is progged to occur along a surface trough/frontal boundary that sets up just to the west and north of the forecast area through the middle of the week. Models suggest that by Wednesday, a subtropical fetch of moisture will get pulled into the area with PWs approaching 2 inches. So the period from Wednesday through Friday looks to be unsettled with some instability and reasonable flow for storm organization. For Monday night and Tuesday, the model consensus is for the surface trough/front to remain to the northwest of the forecast area with not much in the way of synoptic scale forcing anticipated. With this in mind have kept a dry forecast until Tuesday night when the forecast shows some small POPs across far northern KS as the boundary gets a little closer. Temps are forecast to be above normal. Persistent southerly flow and increasing low level moisture should keep lows in the lower and middle 70s. Highs Tuesday are expected to be around 90. For Wednesday through Friday night, the forecast has a chance POP for the reasons mentioned above. Models show an upper level trough passing to the north of the forecast area Wednesday which doesn`t really give much of a push to the surface boundary and allows it to kind of stall out across northern KS and southern NEB. Large scale forcing appears to remain subtle but there are signs for a vort max to lift across the area Wednesday and Wednesday evening. The stronger flow is expected to remain just north of the area so odds for severe weather appear to be greater over northern KS Wednesday where models increase deep layer shear. By Thursday the boundary becomes less defined so a lack of focus for convective development makes forecasting mesoscale details with confidence a little tricky. Nevertheless the expected instability could lead to scattered strong storms. By Friday, Models bring another upper trough through the plains and a better push to the frontal boundary. The addition of lift from the cold front with the anticipated instability may provide the best opportunity for precip. The main uncertainty in the forecast is how strong the push to the front on Friday will be. The ECMWF is quite a bit stronger with the surface high behind the front and as a result is quicker to move the boundary through the area and slower to develop return flow on the back side of the surface ridge. The Canadian seems to be in the GFS camp in terms of the magnitude of the surface ridge behind the front. So the forecast is a compromise of the solutions. Have a dry forecast for Saturday and Saturday night with all guidance showing the boundary at least through the forecast area by 12Z. Additionally have kept a slight chance POP for Sunday from the model consensus thinking the ECMWF may be to strong with the high pressure and there could be some warm air advection back into the forecast area. Temps trend cooler for Saturday and Sunday, but not nearly as cool as the ECMWF would suggest. && .AVIATION...(For the 00Z TAFS through 00Z Monday Evening) Issued at 615 PM CDT SUN SEP 4 2016 VFR conditions are expected throughout the period. LLWS is expected between after 03Z as the LLJ increase from the SSW near 45 knots. Winds will increase between 14-15Z with sustained 15-20 knots and gusts near 25+ knots. && .TOP Watches/Warnings/Advisories... NONE. && $$ SHORT TERM...65 LONG TERM...Wolters AVIATION...Baerg
Area Forecast Discussion
National Weather Service Billings MT
302 AM MDT MON SEP 5 2016 .SHORT TERM...valid for Tdy and Tue... As the Pacific trough continues to move across the area this morning, some light showers remain. However, the bulk of the energy with this system has already moved through, and things will begin to wind down through the morning. Before it does, a couple of small waves of energy will move across mainly southeastern Montana. This will keep some higher rain chances from mainly Rosebud County eastward. The satellite imagery is showing some drier air working into behind the showers in Wyoming. Going into the afternoon, the GFS and the HRRR are showing some clearing working into southern Montana. Given this, have skies clearing out some. With the reduced rainfall and cloudiness, have temperatures a little warmer today. Flow will remain northwesterly through the remainder of the short-term. Tuesday will mostly be dry, with near seasonal temperatures. Overnight into Wednesday, a weak wave will move through the area bringing a slight chance for some precip to southeastern Montana. Reimer .LONG TERM...valid for Wed...Thu...Fri...Sat...Sun... Models in good agreement for most of the extended period. They indicate several short waves crossing over the region for the latter half of the work week. However, moisture appears limited as the best precipitable water values remain generally north and east of our CWA. Flow aloft turns zonal Saturday leading to dry and stable conditions. Extended range proggs then suggest a trough will drop down into the Rockies at day 7 (Sunday) with some decent moisture aboard leading to an increasing chance of precipitation. Therefore, we have increased PoP`s in that time frame. BT && .AVIATION... Widespread showers and MVFR/IFR and possibly local LIFR Cigs will continue across the TAF sites this morning. Expect CIGS to improve to from west to east between 14Z and 19Z. BT && .PRELIMINARY POINT TEMP/POPS... Tdy Tue Wed Thu Fri Sat Sun ------------------------------------------------------- BIL 063 044/073 051/071 049/073 048/070 048/079 053/075 5/T 21/U 11/B 11/B 11/U 10/U 12/W LVM 060 037/071 043/069 043/071 040/069 041/077 045/073 5/T 21/U 21/N 11/B 11/U 11/U 12/W HDN 066 043/075 048/074 046/075 045/072 044/080 048/076 4/T 21/U 11/B 11/B 11/B 10/U 02/W MLS 063 045/073 052/072 049/074 049/070 048/079 053/077 7/T 20/U 22/W 12/T 21/N 10/U 02/W 4BQ 067 044/071 050/073 048/075 048/069 046/078 051/076 6/T 22/T 32/W 11/B 21/B 10/U 02/W BHK 062 043/069 049/069 046/072 046/066 044/076 049/075 6/T 21/B 45/T 12/T 22/T 20/U 02/W SHR 067 042/073 047/073 045/074 044/069 042/078 046/076 5/T 22/T 21/B 11/U 21/B 10/U 02/W && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings
Area Forecast Discussion
National Weather Service Hastings NE
458 AM CDT MON SEP 5 2016 .SHORT TERM...(Today and tonight) Issued at 422 AM CDT Mon Sep 5 2016 We continue with upper level southwest flow as a synoptic trough over the Rocky Mountains/Great basin continues push out multiple impulses from its base. A strong low-level jet axis essentially bisects our CWA from southwest to northeast. The nose of the jet could pose a slight chance of some small showers or thundershowers, but should not amount to much. I considered taking thunder out for early this morning before 7 am as MUCAPE is very low and mid-level lapse rates are meager. However, with the modest shear due to the strong low-level jet, I kept it in, especially considering that we are still in the warm season. At the surface, a very slowly moving cold front is just to the northwest of the CWA and seems to be ever-so-slowly sagging south toward the CWA as the front is oriented from southwest to northeast. Although areas like Ord have become calm or near calm as the front approaches, I kept mention of fog out as dewpoint depressions do not appear to warrant this, and the fact that the HRRR keeps any fog development west/northwest of the CWA. Today should be dry as we experience subsidence behind the latest impulse that came through. Another more significant vort max is on the way from the southwest and by this evening, we could be in for a round of showers/thunderstorms. We may be able to get some surface based convection going near the front in the early evening, especially for areas near Ord. We will probably have to wait until after 7 pm to wait for the capping inversion to break. With a veering wind profile and slow- moving if not stalled front, we could not only be looking at some large hail and damaging wind gusts if some sun breaks out, we could get an isolated tornado in the early evening, so I mentioned this in the HWO. As the vort max enters the plains, it will give us a rather glancing blow. Essentially our northwest/north half of the CWA stand the best chance at getting precipitation from this wave. Severe parameters support severe mention, but frankly, severe weather looks more probable to the north of the CWA as it looks heading into the late evening and overnight. For temperatures, I kicked them up a notch, especially for tonight with the higher dewpoints and warm air advection in the southern two-thirds of the CWA that should remain south of the stalled front. .LONG TERM...(Tuesday through Sunday) Issued at 422 AM CDT Mon Sep 5 2016 Aloft: SW flow will be ovr the Cntrl Plains Tue with a trof over the Wrn USA and a subtropical high over the E. The Wrn trof will deamplify with its wavelength increasing. A broad trof will evolve over the Nrn 1/2 of the CONUS by Wed with the flow arguably becoming zonal. The subtropical high will be quashed. Sidenote: TS Newton is currently off the coast of MX. It is fcst to circulate poleward on the backside of the high...with its remnants lifting into AZ Wed. It`s possible a piece of the mid-lvl energy could make it into KS Thu. Surface: At dawn Tue the slow-moving cool front will extend from CO across Neb to Lake Superior. This front will remain quasi-stationary thru Wed. In the meantime...another cool front will be making its way thru the NW USA. This front will arrive here Thu night and merge with it. This will nudge the front a little further SE. Another front will arrive Thu night and this will force the combined front far S and E of the region. Strong high pres will quickly slide into the region Fri night-Sat...and then depart into the Ern USA Sun. This fcst area will be in the warm sector Sun...with a strong cold front plunging S into the Nrn USA. Temps: warmer than normal Tue-Wed as long as clouds don`t hang around unexpectedly. Then near normal or cooler than normal Thu-Sun. A few daily details... Tue: A few tstms afternoon/eve...and possibly into the overnight hrs. Gut feeling is our PoPs are too high...mainly due to input from the SREF. Deterministic model consensus puts the best QPF over Nrn Neb...along and N of the front. Am inclined to believe it because it has been so difficult to get rain over S-cntrl Neb the last 90 days. I hope I`m wrong. The warm sector is likely to be capped. So the primary way tstms build S to I-80 or Hwy 6 will be for a cold pool to form and drop S into the warm sector. Convergence/WAA along and N of the front will increase in the evening as a 40-45 kt low-lvl jet develops. Temps in the 80s with dwpts 66-70F will result in MLCAPE of at least 2000 J/kg. Initial storms will develop in the environment with 40-45 kts of deep layer shear. Svr tstms will be possible. Wed: Probably dry...but can`t rule out an isolated tstm or two... mainly along and E of hwy 281. For what it`s worth...18Z/00Z/06Z model QPFs and highest SREF probs target areas SW-NE across KS and then into Ern Neb for best chance of thunder...although it will be more isolated with southward extent over KS. Any storms that might develop could be svr with MLCAPE 1500-2000 J/kg and 40 kts of deep layer shear. SEVERE: used Large Hail Parameter and Craven-Brooks SigSvr to indicate potential for golf ball size hail in the HWO. Thu: A couple tstms possible with shortening wavelengths/approaching trof and the RRQ of a strong 120 kts upr-lvl jet. However...model QPFs are far from impressive. Fri: removed thunder from the fcst as EC indicates stability as the low-lvl moist axis gets shoved S of the fcst area. Sat-Sun: Dry and wonderfully comfortable...especially Sat with dwpts upr 40s-lwr 50s. && .AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Monday night) Issued at 1255 AM CDT Mon Sep 5 2016 The main issue will be low-level wind shear overnight into early Monday morning. The low-level jet is strong enough to include shear in the forecast, despite the fact that surface wind will be relatively strong. && .GID Watches/Warnings/Advisories... NE...None. KS...None. && $$ SHORT TERM...Heinlein LONG TERM...Kelley AVIATION...Heinlein
Area Forecast Discussion
National Weather Service Melbourne FL
330 AM EDT MON SEP 5 2016 ...High Risk for Dangerous Rip Currents Developing Today... .DISCUSSION... TODAY/TONIGHT...(LABOR DAY) Several locations received generous rains of 2-4 inches yesterday as advertised in the presence of high PWAT air from the trailing moisture band and weak sfc trough stretching over the FL Peninsula extending from Hermine which was located well to the north. With the assistance of a weak impulse aloft, local precipitation was able to persist well into the overnight. There has been a general diminishing of activity from MLB southward, but maritime convection was being invigorated from increasing NE flow that will work its way down the coast from JAX courtesy of high pressure pushing south down the U.S. Seaboard. The result is a ~15KT NE wind surge today which will be instrumental in bumping the banded moisture/trough and associated rain chances to South FL by tonight advecting in deep layer drying. Rain chances greater south forecast area trending toward Lake Okeechobee as day progresses. Max Temps U80s to near 90. Min Temps L/M70s. The increasing onshore flow along with arriving long period swells will promote a high risk for rip currents at area beaches, even as overall sky conditions improve behind the push. A concern to beach-goers this Labor Day from larger volumes of water piling ashore and an increased number/intensity of rips especially during the times of the outgoing tide. TUE...A much drier airmass will be across the region to start Tuesday with GFS indicating PW values as low as an inch. However models indicate a gradual increase in moisture in the slightly elevated low level northeast flow through the day, which may lead to some showers developing over the waters and reaching the coast later in the day/evening. Still rain chances look to be quite low with MAV/MET guidance keeping any mentionable PoPs south of Orlando, and even then rain chances are no greater than 20 percent. For now will maintain a slight chance for showers/storms over the Treasure Coast and Okeechobee County, but looks like much of the area should remain dry. WED-SUN...Onshore flow will persist through the extended as West Atlantic high pressure builds back in, with ridge axis remaining north of the area. E/SE flow will continue to gradually increase moisture and rain chances across the region, with PoPs reaching back up to 40-50 percent by the weekend. Greatest coverage of afternoon convection will be over the interior and a lingering chance of onshore moving showers/isolated storms will persist along the coast in the overnight and morning hours. Temperatures remain near normal through the period. && .AVIATION...Recent assortment of variable ceilings and vsbys as debris -RA and -SHRA gradually diminishes near KMLB/KVRB but NE wind surge being felt north of Cape Canaveral with onshore moving SHRA prompting VCSH for KDAB/KSFB. Plenty of residual moisture available for patchy BR to reduce vsbys and introduce tempo IFR ceilings for inland sites KLEE/KSFB during periods of light/variable winds. Wind surge will win out and improve conditions after 12Z trending from KDAB south and southwest but not before VCTS temporarily enters the forecast window for a few hours 16-20Z ahead of clearing line of NE winds G20KT during the afternoon. && .MARINE... TODAY/TONIGHT...Cautionary conditions will develop over the waters today continuing overnight as a NE wind surge of 15KT moves in behind a weak sfc trough over Central FL being pushed toward the South Peninsula. Seas will build to 3-5FT nearshore today and up to 6FT offshore. This will occur in the presence of long period 2-3FT swells of 10-12 seconds. Deteriorating boating conditions will work southward from Flagler Beach eventually to Jupiter Inlet, with gusty winds an additional concern near the coast, intracoastals, and within inlets. GFS model has winds just a little stronger than HRRR model so Advisory conditions not out of the question, especially in the Gulf Stream. TUE-FRI...High pressure will build back in north of the area with a persistent onshore flow through the week. Wind speeds up to 10-15 knots Tuesday-Wednesday forecast to decrease slightly to 5-10 knots into late week. Seas up to 6 feet offshore Tuesday, mainly in a long period swell will gradually decrease, becoming 2-3 feet Thursday and Friday. && .PRELIMINARY POINT TEMPS/POPS... DAB 86 72 87 73 / 30 0 10 10 MCO 88 73 89 73 / 30 10 10 10 MLB 87 75 87 75 / 30 10 10 20 VRB 87 75 88 74 / 30 20 20 20 LEE 89 72 90 73 / 30 0 10 0 SFB 88 72 90 73 / 30 0 10 10 ORL 88 73 89 73 / 30 10 10 10 FPR 88 75 87 73 / 40 20 20 20 && .MLB Watches/Warnings/Advisories... FL...None. AM...None. && $$ SHORT TERM...DS LONG TERM....DW
Area Forecast Discussion
National Weather Service Marquette MI
515 AM EDT MON SEP 5 2016 .SHORT TERM...(Today and tonight) Issued at 514 AM EDT MON SEP 5 2016 WV imagery and RAP analysis indicated a broad area of mid/upper level sw flow through the plains to the wrn Great Lakes between a trough over the wrn CONUS and a ridge from the Gulf of Mexico through the ern Great Lakes. At the surface, increasing southerly flow prevailed into Upper Michigan between high pres over the ern Great Lakes and a trough from the ern Dakotas to nw Ontario. A shortwave trough into wrn MN along with strong inflow of moisture supported an MCS over much of MN and nw WI into nw IA. The lead area of 850-700 mb theta-e advection was bringing shra/tsra into wrn Lake Superior and wrn Upper Michigan. Today, Radar and satellite trends along with short term high res models suggest that the MCS will lift to the northeast with the greatest pcpn amounts/coverage over the wrn cwa this morning. After the pcpn moves through and weakens, expect a lull in the pcpn by late this afternoon into this evening with subsidence in the wake of the shrtwv/MCV. Expect enough sunshine through the thinning convective debris this afternoon to boost high temps into the lower 80s, except over the ern cwa downwind from ssw flow off of Lake Michigan where max readings will remain in the mid to upper 70s. Tonight, expect another shrtwv to emerge from the plains. However, confidence in the timing/location is low given the impact of the ongoing large area of convection. Much of the convection may again focus on wrn and nrn Lake Superior. Nevertheless, with the frontal boundary just to the west, and MUCAPE values into the 1000-1500 J/Kg range, likely shra/tsra pops were mentioned over the far west with chance over the rest of the cwa. With effective shear values into the 30-40 knot range, some stronger storms and isold svr may be possible. With PWAT values to around 1.75 inch, the main hazard will more likely be heavy rain. .LONG TERM...(Tuesday through Sunday) Issued at 417 AM EDT MON SEP 5 2016 Much more active weather is on tap for the upcoming week with the overall upper pattern transitioning from the amplified western troughing/eastern ridging early this week into a more zonal pattern across the CONUS by next weekend. Until the pattern shift occurs...SW upper flow will remain across the Upper Lakes for much of the week allowing a series of shortwaves to move across the area and trigger periods of enhanced showers and thunderstorms. The timing of these shortwaves remains difficult for models to resolve. While it won`t rain the entire week, current model consensus is keying on the wettest periods being late Tuesday, Wednesday afternoon into Thursday morning, and Friday night into early Saturday. Ingredients will be in place for some locally heavy rain especially through midweek. These ingredients include a slow- moving surface cold front paralleling the upper flow as it moves through the Upper Great Lakes region, shortwaves and assoc sfc waves lifting NE across the area and frontal boundary in a broad SW upper flow, and PWs increasing to around 2 inches. As a result, much of the U.P. remains highlighted in the NCEP Hazardous Outlook for a heavy rain threat Wed into Thu. WPC QPF graphics indicate that most of the U.P. should see rain totals in the 1-3 inch range through the upcoming week with the heaviest rain potential over the south central fcst area. Day 2 SPC Convective Outlook has much of the western half interior and south central portions of Upper Mi in a marginal risk for severe weather. Of course, much of severe threat will be dependent on cloud cover, but if we could see some morning sunshine to help with destabilization along the incoming frontal boundary, marginal risk seems reasonable as NAM model soundings show mid-level cap eroding with MLCAPEs rising to near 2000 j/kg range by Tue afternoon and 0-6 Km bulk shear values fm 30-40 kts. Will include a mention of isolated severe thunderstorms Tue afternoon/early evening in the HWO over western interior and south central. The driest days this week look like Thursday and then again Saturday afternoon through next Sunday. Despite significant cloud cover, temperatures will run above normal at least through midweek...especially overnight lows with high minimum temp records in jeopardy Tuesday and Wednesday. Dewpoints in the mid to upper 60s into Thursday will make it feel quite humid. A front moving through by the weekend should then cool temperatures back to normal with lower humidity. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 121 AM EDT MON SEP 5 2016 As a steady SW flow draws moister air into the Upr Great Lks, some -shra and perhaps a TS wl impact IWD and CMX, mainly in the 09Z-18Z time frame. But the near sfc air wl remain dry enuf to allow for VFR conditions to predominate at all 3 TAF locations. Best chc for lower MVFR conditions wl be at IWD, where the showers chcs are greatest. Maintained fcst of LLWS at IWD thru sunrise with the LLJ above a nocturnal radiation invrn. Expect some gusty winds by Mon aftn at the more exposed SAW and IWD locations as daytime heating mixes out these winds. More LLWS is likely tngt at SAW under the sharper pres gradient ahead of slowly aprchg cold fnt. There could be some showers/TS at mainly IWD and CMX by late this evng ahead of this fnt, but confidence is too lo to include in the fcst attm. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 514 AM EDT MON SEP 5 2016 Winds through the middle of next week are expected to remain mainly at 20 kts or less. The only exceptions would be today with south to southwest winds up to 25 knots in gusts over eastern Lake Superior ahead of an approaching low pressure trough and again Thursday as a low deepens to the northeast of Lake Superior. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...Voss AVIATION...KC MARINE...JLB
Area Forecast Discussion
National Weather Service Billings MT
920 AM MDT MON SEP 5 2016 .UPDATE... Water vapor imagery shows upper low lifting to north central MT, with dry slot surging into southeast MT. Pcpn has tapered off significantly across our south over the past couple hours, and this trend will continue thru the remainder of the morning as ascent lifts north and out of our cwa, though we are still seeing impacts from low clouds and areas of upslope flow/drizzle. Have lowered pops thru 18z per current radar trends. PV will remain over south central MT, and with abundant moisture and low convective temps would expect rapid development of clouds and some light showers as skies become scattered to broken. This diurnal development will diminish quickly this evening. Next issue to consider is fog potential tonight as sfc high settles in and winds become generally light. Not expecting much boundary layer drying today, and low temps tonight should fall thru our afternoon dew pts, so looks like a reasonable chance of fog across much of our cwa tonight. Latest HRRR runs are starting to suggest fog as well. Have added patchy fog 06z- 15z Tuesday. JKL && .SHORT TERM...valid for Tdy and Tue... As the Pacific trough continues to move across the area this morning, some light showers remain. However, the bulk of the energy with this system has already moved through, and things will begin to wind down through the morning. Before it does, a couple of small waves of energy will move across mainly southeastern Montana. This will keep some higher rain chances from mainly Rosebud County eastward. The satellite imagery is showing some drier air working into behind the showers in Wyoming. Going into the afternoon, the GFS and the HRRR are showing some clearing working into southern Montana. Given this, have skies clearing out some. With the reduced rainfall and cloudiness, have temperatures a little warmer today. Flow will remain northwesterly through the remainder of the short-term. Tuesday will mostly be dry, with near seasonal temperatures. Overnight into Wednesday, a weak wave will move through the area bringing a slight chance for some precip to southeastern Montana. Reimer .LONG TERM...valid for Wed...Thu...Fri...Sat...Sun... Models in good agreement for most of the extended period. They indicate several short waves crossing over the region for the latter half of the work week. However, moisture appears limited as the best precipitable water values remain generally north and east of our CWA. Flow aloft turns zonal Saturday leading to dry and stable conditions. Extended range proggs then suggest a trough will drop down into the Rockies at day 7 (Sunday) with some decent moisture aboard leading to an increasing chance of precipitation. Therefore, we have increased PoP`s in that time frame. BT && .AVIATION... MVFR/IFR conditions with patchy drizzle and fog will gradually lift N of the area this afternoon. Expect VFR this afternoon with isolated to scattered showers and possibly a thunderstorm. MVFR conditions are possible with the precipitation. Isolated showers or thunderstorms will continue this evening. Precipitation will end late this evening, but patchy fog and stratus will form across much of the area, reducing visibilities and ceilings. Expect areas of mountain obscuration through this evening. Arthur && .PRELIMINARY POINT TEMP/POPS... Tdy Tue Wed Thu Fri Sat Sun ------------------------------------------------------- BIL 063 044/073 051/071 049/073 048/070 048/079 053/075 3/T 21/U 11/B 11/B 11/U 10/U 12/W LVM 060 037/071 043/069 043/071 040/069 041/077 045/073 5/T 31/U 21/N 11/B 11/U 11/U 12/W HDN 066 043/075 048/074 046/075 045/072 044/080 048/076 3/T 21/U 11/B 11/B 11/B 10/U 02/W MLS 063 045/073 052/072 049/074 049/070 048/079 053/077 5/W 20/U 22/W 12/T 21/N 10/U 02/W 4BQ 067 044/071 050/073 048/075 048/069 046/078 051/076 2/T 22/T 32/W 11/B 21/B 10/U 02/W BHK 062 043/069 049/069 046/072 046/066 044/076 049/075 6/T 21/B 45/T 12/T 22/T 20/U 02/W SHR 067 042/073 047/073 045/074 044/069 042/078 046/076 3/T 22/T 21/B 11/U 21/B 10/U 02/W && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings
Area Forecast Discussion
National Weather Service Hastings NE
627 AM CDT MON SEP 5 2016 .SHORT TERM...(Today and tonight) Issued at 422 AM CDT Mon Sep 5 2016 We continue with upper level southwest flow as a synoptic trough over the Rocky Mountains/Great basin continues push out multiple impulses from its base. A strong low-level jet axis essentially bisects our CWA from southwest to northeast. The nose of the jet could pose a slight chance of some small showers or thundershowers, but should not amount to much. I considered taking thunder out for early this morning before 7 am as MUCAPE is very low and mid-level lapse rates are meager. However, with the modest shear due to the strong low-level jet, I kept it in, especially considering that we are still in the warm season. At the surface, a very slowly moving cold front is just to the northwest of the CWA and seems to be ever-so-slowly sagging south toward the CWA as the front is oriented from southwest to northeast. Although areas like Ord have become calm or near calm as the front approaches, I kept mention of fog out as dewpoint depressions do not appear to warrant this, and the fact that the HRRR keeps any fog development west/northwest of the CWA. Today should be dry as we experience subsidence behind the latest impulse that came through. Another more significant vort max is on the way from the southwest and by this evening, we could be in for a round of showers/thunderstorms. We may be able to get some surface based convection going near the front in the early evening, especially for areas near Ord. We will probably have to wait until after 7 pm to wait for the capping inversion to break. With a veering wind profile and slow- moving if not stalled front, we could not only be looking at some large hail and damaging wind gusts if some sun breaks out, we could get an isolated tornado in the early evening, so I mentioned this in the HWO. As the vort max enters the plains, it will give us a rather glancing blow. Essentially our northwest/north half of the CWA stand the best chance at getting precipitation from this wave. Severe parameters support severe mention, but frankly, severe weather looks more probable to the north of the CWA as it looks heading into the late evening and overnight. For temperatures, I kicked them up a notch, especially for tonight with the higher dewpoints and warm air advection in the southern two-thirds of the CWA that should remain south of the stalled front. .LONG TERM...(Tuesday through Sunday) Issued at 422 AM CDT Mon Sep 5 2016 Aloft: SW flow will be ovr the Cntrl Plains Tue with a trof over the Wrn USA and a subtropical high over the E. The Wrn trof will deamplify with its wavelength increasing. A broad trof will evolve over the Nrn 1/2 of the CONUS by Wed with the flow arguably becoming zonal. The subtropical high will be quashed. Sidenote: TS Newton is currently off the coast of MX. It is fcst to circulate poleward on the backside of the high...with its remnants lifting into AZ Wed. It`s possible a piece of the mid-lvl energy could make it into KS Thu. Surface: At dawn Tue the slow-moving cool front will extend from CO across Neb to Lake Superior. This front will remain quasi- stationary thru Wed. In the meantime...another cool front will be making its way thru the NW USA. This front will arrive here Thu night and merge with it. This will nudge the front a little further SE. Another front will arrive Thu night and this will force the combined front far S and E of the region. Strong high pres will quickly slide into the region Fri night-Sat...and then depart into the Ern USA Sun. This fcst area will be in the warm sector Sun...with a strong cold front plunging S into the Nrn USA. Temps: warmer than normal Tue-Wed as long as clouds don`t hang around unexpectedly. Then near normal or cooler than normal Thu- Sun. A few daily details... Tue: A few tstms afternoon/eve...and possibly into the overnight hrs. Gut feeling is our PoPs are too high...mainly due to input from the SREF. Deterministic model consensus puts the best QPF over Nrn Neb...along and N of the front. Am inclined to believe it because it has been so difficult to get rain over S-cntrl Neb the last 90 days. I hope I`m wrong. The warm sector is likely to be capped. So the primary way tstms build S to I-80 or Hwy 6 will be for a cold pool to form and drop S into the warm sector. Convergence/WAA along and N of the front will increase in the evening as a 40-45 kt low-lvl jet develops. Temps in the 80s with dwpts 66-70F will result in MLCAPE of at least 2000 J/kg. Initial storms will develop in the environment with 40-45 kts of deep layer shear. Svr tstms will be possible. Wed: Probably dry...but can`t rule out an isolated tstm or two... mainly along and E of hwy 281. For what it`s worth...18Z/00Z/06Z model QPFs and highest SREF probs target areas SW-NE across KS and then into Ern Neb for best chance of thunder...although it will be more isolated with southward extent over KS. Any storms that might develop could be svr with MLCAPE 1500-2000 J/kg and 40 kts of deep layer shear. SEVERE: used Large Hail Parameter and Craven-Brooks SigSvr to indicate potential for golf ball size hail in the HWO. Thu: A couple tstms possible with shortening wavelengths/approaching trof and the RRQ of a strong 120 kts upr- lvl jet. However...model QPFs are far from impressive. Fri: removed thunder from the fcst as EC indicates stability as the low-lvl moist axis gets shoved S of the fcst area. Sat-Sun: Dry and wonderfully comfortable...especially Sat with dwpts upr 40s-lwr 50s. && .AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Tuesday) Issued at 627 AM CDT Mon Sep 5 2016 Significant Wx: LLWS now until 14Z and then again tonight. Today: LLWS end by 14Z. VFR with just a few altocu 10-13K this morning. Then a few CU develop around 3500 ft this afternoon. S winds will increase to around 20 kts with G30 kts. Confidence: High Tonight: VFR. LLWS redevelops. There is a very low probability of an IFR tstm and G40KT...but left it out for now due to high uncertainty. S winds decrease but remain gusty at times. Confidence: Medium && .GID Watches/Warnings/Advisories... NE...None. KS...None. && $$ SHORT TERM...Heinlein LONG TERM...Kelley AVIATION...Kelley
Area Forecast Discussion
National Weather Service Lincoln IL
934 AM CDT MON SEP 5 2016 .UPDATE... Issued at 934 AM CDT Mon Sep 5 2016 Main forecast update was to add some 20% PoP`s across areas east of I-55 this morning. Radar imagery the last couple hours has been showing some isolated showers tracking northeast amongst the scattered cumulus in this region, most numerous south of I-70. 06Z NAM-Nest model was the only one that seems to pick up on this, and indicates the shower threat should be more across Indiana by midday. Some light showers are starting to show up as far west as Carlinville, but cumulus field and latest RAP cu-rule guidance showing little in the way of cumulus west of I-55, so am not expecting much further westward development. Temperatures are on track and only required some minor tweaks. && .SHORT TERM...(Today and tonight) ISSUED AT 323 AM CDT Mon Sep 5 2016 Ridge of high pressure that provided cool/dry weather to central Illinois over the past couple of days has shifted eastward into the Appalachians. As a result, winds are beginning to veer to a more southerly direction. This will help bring warmer and more humid conditions back into the area today. Given increasing low-level moisture and surface dewpoints climbing into the upper 60s and lower 70s, diurnal cloud cover will be more robust than in previous days. In fact, NAM Cu-rule suggests SCT-BKN clouds east of I-55 this afternoon. Have adjusted sky cover to go with partly sunny conditions across the eastern half of the KILX CWA accordingly. Despite additional cloud cover, southerly winds will help boost high temperatures into the middle to upper 80s. Diurnal clouds will fade away toward sunset, leading to mostly clear conditions tonight. Overnight low temperatures will range from the middle to upper 60s in the Wabash River Valley...to the lower 70s west of I-55. .LONG TERM...(Tuesday through Sunday) ISSUED AT 323 AM CDT Mon Sep 5 2016 Blocking pattern will remain in place across the central/eastern CONUS through mid-week, as remains of Hurricane Hermine meander off the Mid-Atlantic coast. Upper ridge will build over the Midwest, with both the GFS and ECMWF showing 594dm 500mb heights over central Illinois by Tuesday and Wednesday. With surface high sliding off to the east and southerly winds developing across the area, a period of very warm and increasingly humid conditions is expected. Based on 850mb temps progged to climb to around 20C, it appears Tuesday and Wednesday will be the warmest days of the forecast period, with high temperatures both days reaching the lower 90s. While a few models (particularly the GFS) suggest widely scattered convection within the warmer airmass, main baroclinic zone and strongest forcing will stay well to the N/NW until Wednesday night. As a result, have gone with a warm/dry forecast through Wednesday. After that, upper blocking pattern will break down as remains of Hermine get shunted northeastward and prevailing Midwest ridge flattens. 00z Sep 5 models are in relatively good agreement, with slow-moving cold front over the central/northern Plains pushing into the area Wednesday night. Given deep-layer moisture characterized by precipitable water values in excess of 2 inches and increasing upper support, have opted to go with high chance to likely PoPs mainly after midnight. The front will stall across central Illinois during the day Thursday as it becomes parallel to the upper flow, resulting in continued chance PoPs. All models then show a wave developing along the boundary, causing the front to lift back northward Thursday night into Friday. Due to enhanced synoptic lift with this feature, have introduced likely PoPs across the W/SW CWA Thursday night, then everywhere north of the I-70 corridor on Friday. A stronger short-wave trough will dig southeastward into the region for the upcoming weekend, eventually pushing the persistent frontal boundary well to the east and south. Latest models have sped up the wave, with the ECMWF now showing the front along the I-70 corridor as early as 12z Sat. GFS remains slightly slower, but still shows the boundary clearing the area by early afternoon. At this time, will hold on to chance PoPs east of I-55 through the day Saturday, followed by a return to cooler/drier weather Saturday night and Sunday. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 644 AM CDT Mon Sep 5 2016 VFR conditions expected across the central IL terminals through the 12Z TAF period. Scattered cumulus around 5000 ft AGL across the area this morning expected to clear at least from KSPI-KPIA westward late in the morning...but will be replaced by diurnal cumulus development by 17Z across the area through 00Z. Winds SE 5-10 kts in the morning becoming S 10-15 kts with gusts to around 20 kts after 17Z. Winds decreasing to under 10 kts after 00Z. && .ILX Watches/Warnings/Advisories... NONE. && $$ UPDATE...Geelhart SHORT TERM...Barnes LONG TERM...Barnes AVIATION...Onton
Area Forecast Discussion
National Weather Service Marquette MI
743 AM EDT MON SEP 5 2016 .SHORT TERM...(Today and tonight) Issued at 514 AM EDT MON SEP 5 2016 WV imagery and RAP analysis indicated a broad area of mid/upper level sw flow through the plains to the wrn Great Lakes between a trough over the wrn CONUS and a ridge from the Gulf of Mexico through the ern Great Lakes. At the surface, increasing southerly flow prevailed into Upper Michigan between high pres over the ern Great Lakes and a trough from the ern Dakotas to nw Ontario. A shortwave trough into wrn MN along with strong inflow of moisture supported an MCS over much of MN and nw WI into nw IA. The lead area of 850-700 mb theta-e advection was bringing shra/tsra into wrn Lake Superior and wrn Upper Michigan. Today, Radar and satellite trends along with short term high res models suggest that the MCS will lift to the northeast with the greatest pcpn amounts/coverage over the wrn cwa this morning. After the pcpn moves through and weakens, expect a lull in the pcpn by late this afternoon into this evening with subsidence in the wake of the shrtwv/MCV. Expect enough sunshine through the thinning convective debris this afternoon to boost high temps into the lower 80s, except over the ern cwa downwind from ssw flow off of Lake Michigan where max readings will remain in the mid to upper 70s. Tonight, expect another shrtwv to emerge from the plains. However, confidence in the timing/location is low given the impact of the ongoing large area of convection. Much of the convection may again focus on wrn and nrn Lake Superior. Nevertheless, with the frontal boundary just to the west, and MUCAPE values into the 1000-1500 J/Kg range, likely shra/tsra pops were mentioned over the far west with chance over the rest of the cwa. With effective shear values into the 30-40 knot range, some stronger storms and isold svr may be possible. With PWAT values to around 1.75 inch, the main hazard will more likely be heavy rain. .LONG TERM...(Tuesday through Sunday) Issued at 417 AM EDT MON SEP 5 2016 Much more active weather is on tap for the upcoming week with the overall upper pattern transitioning from the amplified western troughing/eastern ridging early this week into a more zonal pattern across the CONUS by next weekend. Until the pattern shift occurs...SW upper flow will remain across the Upper Lakes for much of the week allowing a series of shortwaves to move across the area and trigger periods of enhanced showers and thunderstorms. The timing of these shortwaves remains difficult for models to resolve. While it won`t rain the entire week, current model consensus is keying on the wettest periods being late Tuesday, Wednesday afternoon into Thursday morning, and Friday night into early Saturday. Ingredients will be in place for some locally heavy rain especially through midweek. These ingredients include a slow- moving surface cold front paralleling the upper flow as it moves through the Upper Great Lakes region, shortwaves and assoc sfc waves lifting NE across the area and frontal boundary in a broad SW upper flow, and PWs increasing to around 2 inches. As a result, much of the U.P. remains highlighted in the NCEP Hazardous Outlook for a heavy rain threat Wed into Thu. WPC QPF graphics indicate that most of the U.P. should see rain totals in the 1-3 inch range through the upcoming week with the heaviest rain potential over the south central fcst area. Day 2 SPC Convective Outlook has much of the western half interior and south central portions of Upper Mi in a marginal risk for severe weather. Of course, much of severe threat will be dependent on cloud cover, but if we could see some morning sunshine to help with destabilization along the incoming frontal boundary, marginal risk seems reasonable as NAM model soundings show mid-level cap eroding with MLCAPEs rising to near 2000 j/kg range by Tue afternoon and 0-6 Km bulk shear values fm 30-40 kts. Will include a mention of isolated severe thunderstorms Tue afternoon/early evening in the HWO over western interior and south central. The driest days this week look like Thursday and then again Saturday afternoon through next Sunday. Despite significant cloud cover, temperatures will run above normal at least through midweek...especially overnight lows with high minimum temp records in jeopardy Tuesday and Wednesday. Dewpoints in the mid to upper 60s into Thursday will make it feel quite humid. A front moving through by the weekend should then cool temperatures back to normal with lower humidity. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 742 AM EDT MON SEP 5 2016 As a steady SW flow draws moister air into the region and a disturbance lifts through the area shra/tsra will imapct IWD and CMX this morning. But the near sfc air wl remain dry enough to allow for mainly VFR conditions. The best chance for MVFR conditions will be at IWD with the most persistent rain. More LLWS is likely tonight under the sharper pres gradient ahead of slowly approaching cold front. There could be some showers/TS at mainly IWD and CMX by late this evening ahead of this front, but confidence is too low to include in the fcst attm. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 514 AM EDT MON SEP 5 2016 Winds through the middle of next week are expected to remain mainly at 20 kts or less. The only exceptions would be today with south to southwest winds up to 25 knots in gusts over eastern Lake Superior ahead of an approaching low pressure trough and again Thursday as a low deepens to the northeast of Lake Superior. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...Voss AVIATION...JLB MARINE...JLB
Area Forecast Discussion
National Weather Service Billings MT
300 PM MDT MON SEP 5 2016 .SHORT TERM...valid for Tue and Wed... Water vapor imagery shows upper trof axis still over the northern Rockies, with stronger shortwave having departed to our northeast but lingering PV over south central MT. Convective temps are rather low and we are already seeing scattered showers develop west of KBIL and tracking east. There is also an area of thunderstorms in southeast Carter County extending to near Devils tower that is along region of strong low level frontogenesis. This stronger activity should push east of our cwa over the next couple hours as front does likewise. Overall, expect isolated to scattered showers and a few low-topped t-storms between now and sunset courtesy of the cyclonic flow aloft and daytime heating, along with abundant residual boundary layer moisture. Dry conditions will prevail late tonight. Main forecast concern in the short term is fog potential late tonight into Tuesday morning. Looks like a good setup for fog as sfc ridge settles in producing light winds and clearing skies. Low temps tonight should fall below current dew pts, by several degrees in some places, and HRRR has trended consistently towards fog across parts of the cwa after midnight. SO, with confidence have added patchy fog from 06-15z. A Billings upslope fog event is possible. We will see some theta-e return into southeast MT on Tuesday with LIs near -2c by late in the day. Could see a shower/t-storm pop by late afternoon but better chance of this will be thru the night as next Pacific shortwave moves thru the area. Will keep isolated pops for our west-central parts Tuesday night but much better potential for pcpn will be east of sfc trof, i.e. Rosebud County eastward, with activity extending into Wednesday morning before energy shifts east. We will see a gusty W-NW wind with good mixing in post-frontal regime across the lower elevations on Wednesday. Gusts should reach 25-35 mph. Drier air will advect into our cwa behind early Wednesday shortwave, so will keep only isold pops for the high terrain. After a chilly night tonight with lows in the upper 30s to mid 40s (dewpts are too high for a serious risk of a freeze), temps will turn warmer the next two days with highs back to the upper 60s to mid 70s across the lower elevations. This will be closer to normal but still a few degrees on the cool side for early September. JKL .LONG TERM...valid for Thu...Fri...Sat...Sun...Mon... Good agreement in the global models continues through the extended period. Northwesterly upper level flow will keep temperatures seasonably cool with a few showers as a weak disturbance crosses the region Thursday afternoon into Friday. Not expecting widespread precipitation with this disturbance, but the better chance will be to the east and northeast of Billings, and closer to the upper level low passing over northeastern Montana. Expect a breezy Friday across the forecast area as the disturbance quickly passes. Conditions turn drier and warmer over the weekend with temperatures nearing 80 on Saturday as a ridge of high pressure moves overhead. By the end of the weekend, models are beginning to agree on the next cool down. Global models suggest an upper level low diving south across the forecast area. With good agreement in this system being a cooler one, would not be surprised to another chance for high elevation snow, so lowered temps and increased precip chances for the higher terrain and nearby foothills. Dobbs. && .AVIATION... MVFR conditions will gradually lift to VFR this afternoon. Isolated to scattered showers and a few thunderstorms will decrease this evening. MVFR conditions are possible with the precipitation. Areas of fog will develop late this evening producing MVFR/IFR conditions. Areas of stratus are likely as well, especially E of KBIL. The stratus will produce IFR to LIFR conditions E of KBIL. VFR will return to much of the area after 15Z Tuesday. Lower conditions may linger longer over KMLS. Expect areas of mountain obscuration through this evening. Arthur && .PRELIMINARY POINT TEMP/POPS... Tue Wed Thu Fri Sat Sun Mon ----------------------------------------------------------- BIL 044/073 052/072 049/073 048/070 048/079 053/074 045/058 20/U 21/N 11/B 11/U 10/U 12/W 33/W LVM 037/071 043/070 043/070 041/068 042/077 045/073 039/053 21/U 21/N 11/B 21/U 11/U 13/W 33/W HDN 042/075 048/074 045/075 045/072 043/081 048/076 042/062 21/U 21/B 11/B 11/U 10/U 02/W 22/W MLS 044/073 052/073 049/074 048/069 047/080 052/076 047/063 20/U 33/T 11/B 23/W 20/U 02/W 22/W 4BQ 044/071 050/073 048/075 048/068 045/079 051/076 045/061 22/T 32/T 11/B 21/N 10/U 01/U 22/W BHK 043/069 049/070 046/072 046/065 043/076 049/075 044/060 20/B 45/T 12/W 22/W 20/U 01/U 22/W SHR 041/073 047/073 044/074 044/068 042/079 047/077 042/054 22/T 21/B 11/B 21/B 10/U 12/W 33/W && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings
Area Forecast Discussion
National Weather Service Des Moines IA
344 PM CDT Mon Sep 5 2016 .SHORT TERM.../Tonight/ Issued at 344 PM CDT Mon Sep 5 2016 The primary concern will be convective trends later tonight. Much of the precipitation has exited the state with the warm sector surging northward and the best 0-2km moisture convergence now from SD across southern MN. Heat indices are now into the mid 90s central and south. The front is currently on the Siouxland doorstep and impacts for IA weather will depend on whether it will develop more surface based soon, or wait for more of an elevated potential later this evening. Conditions are quite favorable for supercell development just to our west, and the Bunkers motion would suggest a more easterly motion if that were to occur. This would eventually push the outflow and convergence farther south into IA to be realized by the low level jet and associated convergence. However examination of visible satellite imagery currently shows little vertical development along the front. The more likely scenario, and that supported by most models, is that strong moisture transport along the 305K isent surface will produce convection from the Siouxland area across southern MN fed by 35- 45kts of inflow. The RAP mean wind suggests motion parallel to the front with Corfidi vectors either neutral or weak from the same direction. This supports a heavy rain potential just across our border with precipitable water, specific humidity and integrated water vapor transport all very near climatological maxes. Have added heavy rain wording to the forecast north, but held off on a headline for the moment due to this thinking and high resolution models highlighting MN rather than IA as well. .LONG TERM.../Tuesday through Monday/ Issued at 344 PM CDT Mon Sep 5 2016 Active weather pattern sets up this week with periodic severe weather and heavy rain potential Tuesday into Wednesday. Utilized a blend of the ECMWF/NAM Tuesday into Wednesday, and then a ECMWF/GFS blend through the remainder of the forecast period. Tuesday into Wednesday...Models continue to shift convection further north during the day Tuesday with the frontal boundary looking to drape across far northern Iowa into southern Minnesota. The latest ESRL HRRR, NSL WRF, and SPC WRF have all shifted the convection further north and delayed the timign until late Tuesday afternoon. There maybe some elevated convection that develops during the afternoon within the WAA regime and theta-E advection north of Highway 30. However, a fairly strong cap remains in place and the stronger forcing looks to transition further north into Minnesota through the day Tuesday. Shaved off pops across the southern portions of the forecast area during much of the day Tuesday. With the drier forecast, leaned toward increasing winds and temperatures for Tuesday with the good mixing and strong surface pressure gradient. The stronger winds are likely to occur over the southern two-thirds of the CWA. Strong moisture transport continues across the state Tuesday night into Wednesday. Deep moisture convergence will be along or just north of the Iowa/Minnesota border by 00z Wednesday and gradually transitions south-southeast through 12z Wednesday as the front is slow to move. By around 12z Wednesday, the front looks to remain oriented from around MCW to ALO southwest to DNS to CRL area into east-central Nebraska. A strong atmospheric river continues to pump moisture into this area with warm layer clouds depths remaining persistent around 4000 meters between 00-12z Wednesday and even through much of the day Wednesday. Another shortwave tracks across the state Wednesday providing additional thunderstorm chances. Certainly a long duration moderate to heavy rain threat and have introduced mention of heavy rain across northern Iowa during this time. With the PWATs ranging from 1.5-2.0 inches Tuesday into Wednesday, slow storm motion and possible training of thunderstorms, the potential exists for flash flooding Tuesday night into Wednesday. River flooding is also possible over portions of northern Iowa, but had low confidence to issue any hydrologic related headline due to the uncertainty of frontal boundary location as well as the delayed timing of the convection. May need to consider at least a flash flood watch over the far northern portions of the CWA for late Tuesday night into Wednesday. Some of the contigency river forecasts (max QPF vs min QPF) for the Cedar River Basin reach just over minor flood stage (if at all) and not until late in the work week into the weekend for any potential impacts. The only concerned location would be Cedar Falls (CEDI4) if the max QPF forecast comes true in this basin. As far as the severe weather potential, agree with the Slight Risk shifting further north where the boundary is located on Tuesday/Tuesday night. 0-6km bulk shear ranges near 35-40 knots over far northern Iowa Tuesday evening with decent MLCAPE values present. Initial storm mode looks to be supercells but will likely quickly transition into heavy rain producers. Cannot rule out the threat for wind late tomorrow night into Wednesday morning over far northern Iowa with the amount DCAPE present (500-1000J/kg). MCS maintenance probability over the north ranges around 40-50% overnight into Wednesday morning. Thursday into Friday...Surface high pressure builds into the state Thursday but is quickly removed a fairly decent surface low pressure and mid-level shortwave moves northward into the state by Friday morning. A strong trough and cold front move south late Friday night into Saturday, with Saturday morning looking to be somewhat windy behind the front. GFS is slightly more potent than the ECMWF, but both are in agreement with the timing of the trough Friday night. && .AVIATION.../For the 18Z TAFS through 18Z Tuesday afternoon/ Issued at 106 PM CDT Mon Sep 5 2016 Primary concerns will be convective trends and LLWS into Tue morning. Thunderstorms along the IA/MN border should continue to lift north away from TAF sites this afternoon leaving VFR conditions and brisk southerly winds in place. These brisk winds will sustain themselves above the boundary layer into the night producing LLWS ahead of the NE/MN frontal boundary, mainly affecting north and west sites /KFOD/KMCW/. Convection is also expected to develop along the front and reach at least the northwest third of Iowa overnight. Have only included VCSH at KFOD/KMCW for now until confidence in timing and locations becomes more clear. && .DMX WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...Small LONG TERM...Podrazik AVIATION...Small
Area Forecast Discussion
National Weather Service Miami FL
439 PM EDT MON SEP 5 2016 .SYNOPSIS... Numerous showers and thunderstorms will continue into early evening over most land areas. During the evening, showers will slowly diminish with the loss of daytime heating. Through Friday, as high pressure builds over the Atlantic, deep southeast flow will favor an enhancement of shower/thunderstorm activity across the interior and Gulf regions of South Florida. During the nights, activity will favor the east coast. Expect near normal temperatures for this time of year. && .DISCUSSION... Water vapor imagery continues to show a mid to upper level moisture boundary draped east to west across South Florida. Analyzing the 12Z morning sounding, there were multiple indicators of an active day with respect to convection. First, CAPE values were around 3500 J/KG, a sufficient amount for strong updrafts. No appreciable temperature inversion (cap) could be seen, which had favored early initiation. A PW value of 2.14 represented a very moist atmosphere. This, in combination with weak winds in the low to mid levels, has led to increase risk of flooding today in low lying and poorly drained areas. The HRRR and Hi-Res WRF model keep convection ongoing through at least early evening. Have left likely pops in the grids over all land areas to account for this. The water spout potential will remain elevated along the coastal waters due to light winds in the lower levels. Tonight, after the loss of diurnal heating, shower and storm activity should diminish with highest chances remaining along the east coast. On Tuesday, the 12Z GFS keeps the aforementioned mid and upper level moisture front over the CWA with the highest PW near the very southern tip of Florida. Thus, chance to likely pops have been added to this region Tuesday afternoon. The main impacts from these storms will again be heavy rain, brief gusty winds, and frequent lightning. Wednesday through Thursday, high pressure building over the Atlantic will bring a return to the more typical summerlike pattern to South Florida with east flow prevailing. Expect highest chances of afternoon, sea breeze driven showers and storms over the interior and Gulf Coast. During the nights, activity may shift towards the east coast. From Friday into the weekend, long range models advect higher moisture up from the tropics and increase storm activity. Beaches: From this evening through Wednesday, models project a 3-4 foot 11-12 second swell, generated by Hermine, to drop southward down our Atlantic coastal waters. This scenario would create elevated surf along the Atlantic beaches and an enhanced rip current risk. These conditions may warrant marine and rip current products to be issued later this afternoon. && .AVIATION... Weak boundary sliding south into region helping to generate SHRA/TSRA over ATLC that are occasionally brushing east coast. Coverage increases across rest of region after 14Z becoming sct-nmrs, but confidence in timing is low so will keep VCTS rather than TEMPO groups. TEMPO MVFR conditions with most activity, occasional IFR with heavier showers. Prevailing ENE flow through the day. && .MARINE... High pressure ridge continues to build across the Atlantic through late in the week with chance of showers and thunderstorms throughout the period. A 11-12 second swell, generated, by Hermine, will push south through the Atlantic coastal waters late today through early Wednesday building seas close to exercise caution to advisory along the Atlantic waters late tonight into Tuesday. Seas could peak around 3-5 feet east of Miami- Dade/Collier counties and 5-7 feet in the coastal waters east of Palm County. Conditions will begin to improve by late Wednesday. && .PRELIMINARY POINT TEMPS/POPS... West Palm Beach 77 88 76 88 / 50 40 30 40 Fort Lauderdale 77 89 77 88 / 50 50 40 40 Miami 77 89 77 90 / 40 60 40 40 Naples 75 90 73 89 / 30 50 20 50 && .MFL Watches/Warnings/Advisories... FL...None. AM...None. GM...None. && $$ SHORT TERM...27/JT LONG TERM....27/JT AVIATION...ALM
Area Forecast Discussion
National Weather Service Omaha/Valley NE
342 PM CDT MON SEP 5 2016 .SHORT TERM...(tonight through Thursday) Issued at 337 PM CDT MON SEP 5 2016 Latest water vapor imagery in combination with RAP analysis shows a mid level trough axis extending from southwestern Canada into the Great Basin with a lead shortwave drifting northeast across Wyoming and into into the western Dakotas. 12z upper air analysis showed an 850mb thermal ridge extending from the southwestern CONUS all the way into southern MN with dewpoints around +16 to 17C aided by a 50kt southwesterly low level jet. PW`s remain high with the 12Z observed sounding indicating 1.82". At the surface this afternoon...a cold front extended northeast from lee side low pressure over western Colorado across central Nebraska and into northeast South Dakota. Latest visible satellite shows a shrinking stratus deck over western and north central Nebraska behind the frontal boundary with a congested CU field over northeast Nebraska. Focus for thunderstorms late this afternoon/evening will be along the surface front with latest CAMs indicating development as early as 20-22Z across northeast Nebraska. RAP analysis shows cap is quickly diminishing in this area with MUCAPE values around 2500-3000 J/KG. This activity should persist for a few hours before moving off to the northeast with the main activity forecast to develop across northwestern Kansas and move along the boundary overnight. CAMS also show potential MCS development across north Central Nebraska overnight and sliding along the Nebraska/South Dakota border. Thus, much of the CWA should remain dry overnight except the north. The front begins to slowly drift southeast Tuesday with increasing potential for heavy rain along and behind the boundary. Possibility for a few supercells does exist across a portion of the northern CWA Tuesday afternoon where a slight risk has been outlooked from SPC. Front finally slides south Wednesday when mid level shortwave kicks through. Again...the potential for heavy rain exists with strong to severe thunderstorms. Wednesday night into Thursday looks dry as the frontal boundary pushes south of the forecast area. .LONG TERM...(Thursday night through Monday) Issued at 237 PM CDT MON SEP 5 2016 By Thursday night, the front begins to lift north as another mid level shortwave ejects into the Central Plains. A stronger shortwave trough will move through the Northern Plains Friday pushing a much stronger cold front through the CWA leaving the area dry for next weekend. && .AVIATION...(18Z TAFS for KOFK...KLNK and KOMA.) Issued at 1202 PM CDT MON SEP 5 2016 Generally expect VFR conditions at KOMA and KLNK through the period. Low level wind shear should occur again tonight as surface winds decouple but boundary layer winds aloft increase into the 40 to 50 knot range. For KOFK...did include a PROB30 group for TSRA later this evening. Depending on how the front progresses and how convective outflow develops...low clouds could move into KOFK. For now did mention MVFR ceilings toward 13z but ceilings could drop lower than that and sooner. Confidence just not high enough though at this time to go with IFR. && .OAX Watches/Warnings/Advisories... NE...None. IA...None. && $$ SHORT TERM...Kern LONG TERM...Kern AVIATION...Miller