Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/13/18

Area Forecast Discussion...corrected AVIATION
National Weather Service La Crosse WI
600 PM CDT Thu Jul 12 2018 .SHORT TERM...(This evening through Friday) Issued at 301 PM CDT Thu Jul 12 2018 Latest 18z surface analysis shows cold front extending from over Lake Superior into southeast South Dakota. Weak moisture convergence in the 925-850mb layer continues to allow scattered showers/storms to linger/develop across central Minnesota this afternoon...per latest mosaic radar. Main forecast concerns are severe possibilities/showers and storms over forecast area this evening into tonight. The deterministic 12.12z GFS/NAM/ECMWF are in good agreement in moving surface cold front slowly southward into southern Minnesota and central Wisconsin by 12z Friday. Latest hi-resolution and 12.12z deterministic models show a slower progression of the surface front into the forecast area than previous runs. This will impact timing of shower/storm activity to move into the forecast area. At this time...timing of convection looks to be in the 01-03z into northern parts of the forecast area. As the front moves slowly south...convection will overspread southeast Minnesota and western Wisconsin during the overnight hours tonight. Some of the storms could be strong to severe mainly north of Interstate 90 this evening and into the early morning hours the latest 12.17z RAP shows 0-3km of 20 knots and 0-6km most unstable CAPE of 2500-3500 j/kg over the forecast area. Damaging winds would be a main threat. The 12.12z deterministic models suggest precipitable water values of 1.5 inches to 2 inches over the forecast area. Shower/thunderstorms will have the potential for sufficient rainfall amounts and a locally heavy rain threat. Surface front remains nearly stationary across forecast area during the day Friday. The 12.12z deterministic models show moisture transport/convergence at 925-850mb layer and weak lift along front and this will linger scattered showers and thunderstorms across forecast area. The latest hi-resolution models indicate scattered showers/thunderstorms across the forecast area and will continue this trend in the forecast. At this time...storms should remain below severe limits...however a few could be models suggest 0-6km most unstable CAPE of 3000-3500 j/kg. Depending on how far south surface front moves and if skies will be mostly sunny Friday...temperatures will climb to around 90 degrees over the southern forecast area with heat indices of 95 to around 100. .LONG TERM...(Friday night through Thursday) Issued at 301 PM CDT Thu Jul 12 2018 The front that is across Minnesota, South Dakota and Nebraska today will still be in the area at the start of this period. Just where the front will be is not clear and this is where the uncertainty resides in the forecast. The variation in the models is from near the Iowa/Minnesota border from the 12.00Z ECMWF to across northern Missouri from the 12.12Z GFS with the 12.12Z NAM in between but closer in position to the GFS. The upper level ridge will still be in place across much of the country with the local area still expected to be on the northern periphery of the ridge and on the southern edge of the westerlies. The positive tilt short wave trough working across the northern Rockies today is expected to be moving across the area Friday night and Saturday. By the time the wave gets to the Upper Midwest it looks to have lost much of its amplitude and thus should come through with just some very weak pv advection in the 500-300 mb layer. While not that strong, there will be increase in the low level moisture transport ahead of this wave and into the front Friday night. This forcing should be enough to generate another round of convection along the front that would primarily be over the southern sections of the forecast area. With a lack of shear, any threat for damaging winds and large hail looks very low, but certainly some potential for heavy rain. Precipitable waters will still be around 2 inches ahead of the front and warm cloud depths Friday night will be in the 4 to 4.5 km range. As of now, the area can take some rain without any concerns for flooding, but if this round of convection would happen to fall over areas that receive rain tonight and Friday, it may be necessary with later forecasts to consider a flash flood watch. This front should then get pushed far enough south of the area for relative minimum in the rain chances for Saturday night. The rain chances will then start to ramp back up Sunday as the next front gets pushed into the area. An upper level low will be moving across central Canada with the southern tip of the associated trough getting drug across the Upper Midwest. The GFS shows more short wave energy in the southern extent of the long wave trough than the ECMWF does. With these differences, the GFS has much more convection along the front than the ECMWF does which for now, will result in just some general 30 to 40 percent chances Sunday and Sunday night with the passage of this front. Some lingering chances into Monday across the southeast until the front is well away from the area and then it looks like high pressure will build in at the surface for a period of dry weather from Monday night through Tuesday night. Some rain chances will then be reintroduced starting Wednesday with the potential for another system to be running along the northern edge of the upper level ridge. Significant timing differences between the models having the upper level ridge becoming centered over the West Coast and how fast this will happen to allow this next system to come into the area. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 600 PM CDT Thu Jul 12 2018 Cold front will bring a bkn line of showers/storms across the area this evening, a few strong to severe. The pcpn will continue overnight into Fri morning. The front is progged to slip south of the TAF sites by early afternoon, with more convective potential later in the day, but also moving south with the front. Cigs: still looking at mainly VFR through the period, although a drop into mvfr with any storm remains possible. WX/vsby: some indications in the meso models that the bulk of the shra/ts could stay just north of I-90. Will hold with -shra vcts mention for now, updating for greater impacts from storms as/if needed. Heavy rain will restrict vsbys at least mvfr, but probably ifr for a short period also. Winds: look for a shift from south to more northwest with passage of gust front/front later this evening. Should hold mostly northwest to variable for the overnight, trending more west northwest later in the day Friday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Heat Advisory until 8 PM CDT this evening for WIZ032>034-041- 042-053>055-061. MN...Heat Advisory until 8 PM CDT this evening for MNZ079-086>088- 094>096. IA...Heat Advisory until 8 PM CDT this evening for IAZ008>011-018- 019-029-030. && $$ SHORT TERM...DTJ LONG TERM...04 AVIATION...Rieck
Area Forecast Discussion
National Weather Service Billings MT
817 PM MDT Thu Jul 12 2018 .UPDATE... Water vapor imagery shows a weak shortwave moving from eastern MT into the Dakotas. There remains a few showers and weak thunderstorms east of Miles City and Broadus, but nothing to the west as we move past peak heating and with increasing subsidence. Have adjusted pops to account for current activity. Expect convection in our east to be done by midnight if not sooner. It will be a quiet night of weather thereafter, with mostly clear skies, light winds and lows in the 50s to mid 60s. JKL && .SHORT TERM...valid for Fri and Sat... Extensive cumulus field was seen on visible satellite imagery over the central and eastern forecast area this afternoon. A wave over W WY could be seen on satellite as well. This wave will propagate eastward into NE WY by 00Z tonight. For the evening PoPs, used HREF reflectivities and RAP soundings. Expect convection over the southern mountains spreading E through the southern tier of the area this evening. Best lift, CAPE and shear was noted from K4BQ to KBHK E until about 04Z. Expect heavy rain with any thunderstorms that develop in this area due to precipitable waters well above 1 inch. Given the above, cannot rule out hail and gusty winds with stronger storms as well. Some energy lingers near the NE Bighorns overnight for a slight chance of thunderstorms. Forecast for Friday has changed a little, as weak energy and monsoonal moisture trapped under the ridge, will bring a slight chance of thunderstorms to the southern mountains and nearby KSHR and parts of SE MT in the afternoon. The focus for storms will shift further E into SE MT during the evening. Decent CAPE with low shear and continued high PWAT`s will continue the threat of heavy rainfall with storms. The temperature forecast came in a bit lower with highs in the upper 80s E and NW, and low to mid 90s elsewhere. The energy under the ridge dissipates for late Fri. night through Saturday morning for a dry forecast. Energy under the ridge increases again for Sat. afternoon. At the same time, an upper low pushes E into N. Saskatchewan, driving a cold front S through the area. The energy will combine with some frontogenesis and increasing moisture to bring a chance of thunderstorms to the mountains and portions of SE MT and Sheridan County. Some storms could be strong due to decent CAPES and some shear. Highs will reach the low to mid 90s ahead of the front. Low-level flow becomes more easterly behind the front Sat. night. The upslope flow will combine with lift from the mid-level front to produce scattered showers and thunderstorms Sat. night across the area. Arthur .LONG TERM...valid for Sun...Mon...Tue...Wed...Thu... Little in the way of changes today, as models remain fairly consistent with periodic isolated shower and thunder potential. Timing of individual waves of precip continue to be uncertain. Precip associated with Saturday cold front appears to linger of southern tier as ridging slowly builds over Idaho. A weak disturbance trapped beneath the developing low will tap some monsoonal moisture to additional isolated shower and thunder potential across mountains and southern zones on Tuesday. Models diverge significantly art this point, with different takes on where Ridge builds back into the region. Have continued to carry more widespread pops through much of the extended period, with nod toward consistently more active pattern that has required very little to initiate isolated convection. As for temperatures. Expected highs in the 70s to around 80 across the region on Sunday. Highs will trend upward through the next couple of days as shallow ridging crosses the region, with highs around 90 for Tuesday. Temps are expected to cool slightly, but remain in the mid to upper 80s through the remainder of the period. AAG && .AVIATION... VFR conditions will prevail through the period. Isolated thunderstorms are possible over southeastern Montana and northern Wyoming, including KSHR and KMLS through about 06z. STP && .PRELIMINARY POINT TEMP/POPS... Fri Sat Sun Mon Tue Wed Thu ----------------------------------------------------------- BIL 062/093 065/091 059/078 059/088 061/090 062/085 060/084 00/U 00/U 43/T 21/U 10/U 23/T 21/U LVM 053/090 055/087 053/078 051/086 053/087 052/083 051/083 01/U 00/U 43/T 11/U 20/U 22/T 11/U HDN 061/093 063/093 060/079 058/089 060/091 061/087 059/086 00/U 01/U 43/T 21/U 11/U 23/T 22/T MLS 064/092 067/093 060/077 057/087 062/090 062/085 061/084 10/U 00/U 43/T 11/U 10/U 13/T 31/B 4BQ 062/091 066/096 062/077 057/086 061/089 061/086 060/085 41/U 22/T 54/T 11/U 11/B 23/T 32/T BHK 061/087 065/093 058/074 054/082 058/086 059/083 057/082 20/U 10/U 44/T 11/U 10/U 23/T 31/B SHR 057/090 059/092 057/077 054/086 056/088 057/085 055/084 12/T 11/U 44/T 32/T 23/T 23/T 23/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$
Area Forecast Discussion
National Weather Service San Francisco Bay Area
900 PM PDT Thu Jul 12 2018 .SYNOPSIS...A weak upper level disturbance and associated monsoonal moisture will move through from the southeast tonight into Friday morning, resulting in a slight chance of showers or thunderstorms from around the Santa Clara Valley northward. Otherwise, typical July weather conditions are expected to prevail through the forecast period, with coastal stratus moving inland around the bays night and morning hours and mostly clear skies prevailing otherwise. && .DISCUSSION...As of 9:00 PM PDT Thursday...Today was a typical summer day with low clouds clearing to the coast by midday, warm temperatures inland, and afternoon highs within a few degrees of seasonal averages. The situation developing this evening is not typical, although an influx of monsoon moisture into our area during the summer months is not exactly unusual. The incoming monsoon moisture had increased precipitable water values on the 00Z Oakland sounding to 1.32 inches and PW values will probably increase further overnight as southeast flow aloft continues to advect mid and upper level moisture across our area. The most uncertain part of the forecast is whether a weak mid-level disturbance embedded in the southeast flow aloft will trigger development of precipitation over our area later tonight and into Friday morning. Radar data shows high- based returns currently moving towards the WNW across the San Joaquin Valley and tracking towards the East Bay. This is consistent with the 12Z local WRF model which shows light precipitation developing in the East Bay later this evening and then tracking to the NW and into the North Bay by around midnight. The HRRR has the same general idea, but develops precipitation somewhat later tonight and initially farther to the south over the South Bay. Current forecast includes shower chances tonight and Friday morning from Santa Clara County northward and this looks good. The primary concern in the short term is whether thunderstorms may develop overnight and into early Friday. Thus far, all thunderstorms have been confined to the southern Sierra Nevada with lightning activity dissipating as the storms move westward over the Central Valley. However, models indicate there could be enough mid level instability to trigger isolated thunderstorms over our area later tonight and into Friday morning and so will maintain slight thunderstorm chances across the SF Bay Area. 00Z OAK sounding shows a dry layer below about 8000 feet which may evaporate much of any precipitation that develops over our area before it reaches the surface. So there is a potential for dry lightning, although relatively high PW values may help lower that potential to some extent. Shower/thunderstorm chances will primarily be focused over the North Bay by tomorrow morning as the upper level disturbance continues to lift to the north. Shower/thunderstorm chances will then end in all areas by midday as the flow aloft over our area veers from southeast to southwest, bringing in a drier airmass. For the remainder of the forecast period, the models forecast an upper ridge to be centered over or near California, which will mean continued seasonably warm and dry conditions inland. Onshore flow is forecast to persist, maintaining a marine layer and relatively cool conditions in coastal areas. Both the GFS and ECMWF hint at another influx of monsoonal moisture by late next week. && .AVIATION...As of 4:30 PM PDT Thursday...Satellite image shows stratus along the coast with mid and high clouds moving through the area from SE to NW. While low clouds are expected to spread onto the coast and possibly into STS...the SE flow is expected to keep stratus out of SFO and the approach tonight. A few sprinkles are possible anywhere tonight and Friday and there is an outside chance of a thunderstorm over the northern SFO Bay Area and North Bay. Vicinity of KSFO...VFR. A few sprinkles possible with a very remote chance of a thunderstorm. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Southerly winds off MRY Bay will allow stratus to move in early tonight. IFR after 02Z at SNS and 03Z at MRY. && .MARINE...As of 8:57 PM PDT Thursday...A weak low off the central California coast will keep light southerly winds through Friday. Winds will become northwest later Friday into the weekend as high pressure rebuilds over the eastern Pacific. Monsoonal moisture from the Desert Southwest will bring a slight chance of thunderstorms tonight and early Friday mainly from the Golden Gate and points north. A mixed swell is expected to develop over the weekend. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...None. $$ PUBLIC FORECAST: Dykema AVIATION: W Pi MARINE: W Pi Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Blacksburg VA
1126 PM EDT Thu Jul 12 2018 .SYNOPSIS... High pressure will build across the region from the north overnight and remain in place through much of the upcoming weekend. This should allow for drier weather under seasonable temperatures the next few days. Increasing heat and humidity should return along with better chances of showers and storms ahead of the next cold front for early next week. && .NEAR TERM /THROUGH FRIDAY/... As of 1123 PM EDT Thursday... Forecast challenge overnight will be whether we get low clouds forming in this wedge as winds in the low levels turn more southeast. The latest high-res models and NAM depict more cloud cover forming over much of the forecast areas east of the WV/VA border down into the NC mountains. Will up the sky cover to trend this way. Showers if any will be mainly isolated and confined to the Blue Ridge south of Floyd VA overnight with best threat south of Boone NC. Patchy fog where it rained and in areas with less cloud cover. Previous discussion from early this evening... No major change needed to going forecast. Still looking at isolated to widely scattered showers with perhaps a rumble of thunder in the mountains of NW NC, with individual cells drifting southward. These showers/embedded thunderstorms forming due to east flow on northern end of 850 mb stalled frontal zone over central NC, aided by a weak 500 mb vort max pivoting out of east-central KY. Most recent 18z NAM and past couple HRRR cycles suggest a continuation of at least showers from Grayson County VA into the mountains of NW, NC even after sunset and in spite of cloudy/rain- cooled air as easterly flow continues. Later tonight and into the overnight, majority of guidance advects axis of of 925-850 mb RH westward against the Blue Ridge on the northern extent of the stalled front. This should lead to an increase in cloud cover especially near and within a few miles either side of the Blue Ridge/mountains of NW NC. It`s less certain how far north/east the extent of clouds will be, which could be low-based. May see intervals of mist at times in the western mountains but likelihood of at least partly to mostly cloudy skies limits how low visbys may get in any fog/mist. Temps look to be on track with lows in the 60s, though will tend into the lower 60s further north and west into the Alleghany Highlands/Greenbrier Valley. Previous discussion follows... Convection remains limited across the region this afternoon with the latest SPC mesoscale analysis showing only weak instability across far southern and eastern sections. This in locations where higher dewpoints and subsequent low level moisture persist near the stalled 850 mb front aloft. Latest CAM model solutions including the HRRR still show isolated showers mainly NC ridges late afternoon/early evening with much of this after sunset once mixing relaxes. Also seeing a weak shortwave remnant within the upper trough pushing through the far southwest overnight. This may tend to keep some convection going until midnight if not longer per latest Nam so keeping in low pops mainly NC mountains overnight. Also guidance indicates a bit stronger boundary layer easterly trajectory developing behind the exiting wave late, possibly resulting in more low clouds near the Blue Ridge by daybreak so boosted clouds some late given consensus. Otherwise clear north to partly/mostly cloudy south as current cumulus fields likely transition to trapped strato-cu in spots with loss of heating. Lows mostly low/mid 60s with a few 50s northwest/valleys. Better push of drier air will occur on Friday with any residual deeper moisture over the southwest sliding to the south Friday morning as the earlier shortwave exits. Guidance then suggests a pretty dry column by afternoon as the surface high to the north continues to build in. However still perhaps enough low level moisture along with weak upslope southeast flow to pop isolated showers across the NC ridges, but chances less than today given lack of instability and soundings showing very limited moisture beneath the inversion around TNB. Otherwise expect any low clouds/fog to quickly mix out Friday morning with sunshine increasing under rather deep easterly flow during the afternoon. High temperatures appear similar to Thursday despite more sunshine with highs mainly low/mid 80s per only slight warming aloft. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 325 PM EDT Thursday... Ridge of high pressure initially extending from Halifax to the mid- Atlantic coast will maintain near normal temperatures along with dry conditions for most of the Blacksburg forecast area through Saturday night. Exception will continue to be from the NW NC mountains north toward the Grayson Highlands of SW VA, where combination of upsloping easterly flow on the periphery of the high pressure system and a slightly moister and marginally unstable airmass will persist supporting the development of mid-afternoon into evening isolated showers or thunderstorms. Situation expected to change slightly Sunday into Sunday night as surface ridge drifts offshore allowing lower tropospheric flow to veer into more of a south to southwesterly component. Weak warm moist advection on backside of departing surface ridge and approach of subtle weak short wave trofs embedded in nearly zonal flow aloft will support an expansion of the threat for widely scattered to scattered showers/thunderstorms to most of the forecast area, especially in the afternoon and evening - maximized across the western flanks of the Appalachians. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 325 PM EDT Thursday... Longer range models continue to reflect a series of weak, but randomly spaced and difficult to time short waves embedded in westerly flow aloft - each of which will support redevelopment of diurnally-driven widely scattered to scattered showers/storms - with the threat again maximized across the mountains due to upsloping flow across the western flanks of the Appalachians coupled with better differential heating due to local topographical influences. The highest threat for precipitation during the long-term period now looks to be in the Tuesday into Tuesday night timeframe. The ECMWF has now come more in line with what was the more progressive GFS in maintaining the integrity of a cool front pushing southeast into/through the Blacksburg forecast area during this period. A higher degree of confidence now exists for this more aggressive scenario; however, as is typical for this time of year for weakening fronts pushing this far south, boundary expected to slow/stall just south of the area before washing out or beginning a drift back northward toward the mid-Atlantic region on Thursday. Uncertainty of frontal position warrants maintaining at least a low threat of precipitation on Wednesday into Wednesday night, although it may very well end up being a dry period if front indeed remains progressive. Regardless, by Thursday, especially by later in the day across southern portions of the forecast area, threat should again be on the increase as lower level winds begin to veer into the south in advance of an even stronger cool front that is expected to arrive on Friday or Saturday. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... As of 731 PM EDT Thursday... VFR conditions should prevail through the rest of the afternoon until late this evening. Isolated to scattered showers with embedded thunder still possible through 01z along the mountains of NW NC, with isolated showers in this general area through the rest of the overnight. After around 05z, should see a period of restricted conditions develop as low clouds begin to develop across at least the southern Blue Ridge into Floyd/Montgomery Counties. 15z SREF probabilities of MVFR ceilings are quite high (around 70-90% within a few miles of the Blue Ridge). Have currently shown MVFR ceilings in this area (mainly affecting Blacksburg and later Bluefield TAFs), though some level of uncertainty on northern extent of this MVFR deck from Roanoke north. May see some mist in the western mountains but coverage limited to the river valleys and visbys no worse than IFR. Winds tonight from the east between 3-6 kts. Should be able to scatter out any MVFR low clouds by around mid- morning Friday revealing SCT Cu/SC and VFR conditions. Winds mainly east 3-5 kts except southeast at Bluefield on the western end of the wedge. Extended Aviation... High pressure will dominate with VFR conditions into Saturday before moisture increases ahead of the next upstream cold front for early next week. This may allow for isolated convection Sunday, including localized restrictions to ceilings and visibilities, to become more widespread especially mountains by Monday afternoon and across the region on Tuesday. However confidence is too low to pinpoint where the showers and thunderstorms may occur. && .EQUIPMENT... As of 1205 PM EDT Thursday... The NOAA weather radio transmitter in Hinton, West Virginia, WXM72 on a frequency of 162.425 MHz, is back on the air. We thank our listeners for their patience during this extended outage. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...AL/JH/WP SHORT TERM...WERT LONG TERM...WERT AVIATION...AL/JH EQUIPMENT...JH