Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/07/19


Area Forecast Discussion
National Weather Service Hastings NE
651 PM CDT Fri Sep 6 2019 ...AVIATION UPDATE... .SHORT TERM...(This evening through Saturday Night) Issued at 154 PM CDT Fri Sep 6 2019 Radar shows light showers and sprinkles across west-central Nebraska this afternoon. With relatively dry low levels, very little rain is actually reaching the ground. Nevertheless, the HRRR shows some spotty activity persisting for a few more hours. Therefore I added some low PoPs in portions of Dawson county to account for this. Tonight, high pressure will move off to the east as an approaching upper trough leads to falling heights aloft. By early Saturday morning, a few thunderstorms could move into northwestern portions of the area. On Saturday, the aforementioned trough will continue to push into the area, and we expect to see thunderstorms redevelop in the afternoon and evening in the vicinity of a warm front that creeps back into the area in the afternoon. A few storms are possible in the afternoon, but the main timeframe for storms may end up being in the late evening as the low-level jet enhances low-level convergence. I expect the highest coverage of storms to occur roughly from Phillipsburg to Red Cloud to Geneva and then gradually move southeast through the overnight. The HREF mean shows 2000J/kg or more of MUCAPE along with up to 40kts of deep- layer bulk shear. This would be supportive of at least a few strong to marginally severe storms. .LONG TERM...(Sunday through Friday) Issued at 154 PM CDT Fri Sep 6 2019 In summary, we will remain in a fairly active pattern through the upcoming week. This forecast features daily chances for rain and thunderstorms across the local area. Rain isn`t guaranteed each day, but it really can`t be ruled out in any period at this point. Temperatures will be up and down, but daily highs should generally be within 5 degrees of climatological normals for this time of year (upper 70s and low 80s). After a mostly dry daytime on Sunday, thunderstorms become likely Sunday night as another upper wave moves in from the west and southwest. Following that, a deeper, slower moving trough will set up over the northwestern CONUS, putting us in southwest flow and giving us daily chances for thunderstorms Monday through Thursday. Models then show this main trough and associated cold front moving through the area Thursday into next Friday. This may lead to a more noticeable cooldown and perhaps a drier stretch of weather as we head into the following weekend. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 651 PM CDT Fri Sep 6 2019 Conditions are expected to be VFR until tomorrow afternoon/evening when cigs are expected to drop down with potential storm development. Some left over convection from the high plains is possible at the terminals in the early morning hours. However, the better chances for storm development are in the afternoon and evening hours tomorrow, due to moisture advection into the area and along a frontal boundary. Winds will be gradually turning from easterly to southerly over the next several hours as the surface high moves off to the east. While winds will remain fairly light overnight, wind speeds are expected to pick up in the mid to late morning hours tomorrow. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ SHORT TERM...Mangels LONG TERM...Mangels AVIATION...Shawkey
Area Forecast Discussion
National Weather Service North Platte NE
626 PM CDT Fri Sep 6 2019 .SHORT TERM...(This evening through Saturday night) Issued at 300 PM CDT Fri Sep 6 2019 Near-term concerns revolve around potential for thunderstorms tonight through Sunday as the weather pattern begins to turn active over the next 5 or so days. Upper-level ridge continues to sit across the southern Rockies. Flow aloft will quickly transition from northwesterly to more zonal as a Pacific Northwest trough moves onshore and begins to quickly shift east within the flow aloft. Height falls will overspread the area as a string of shortwaves moves into the central plains beginning tonight and persisting through much of the weekend. As the initial energy moves into the area, strong southerly h85 flow will develop and help usher in better moisture quality. Thinking most activity Friday afternoon will be focused across the central Sandhills south to Interstate 80 in association with a weak pulse of energy that is expected to clear the area by late afternoon. Current look at radar shows scattered light rain showers south of Highway 2 and west of Highway 83. Most this activity is elevated in nature and is struggling to reach the ground as Ogallala is reporting clear skies and no observed precipitation over the past few hours. CAMS, most notably the HRRR and NAM Nest, acknowledge the existence of this activity and are quick to kill it off by the early evening as it moves to the east. Scattered rain and thunderstorms will develop this afternoon off the front range of Colorado and Wyoming and will slowly push east with time. This activity will be late arriving and because of that, have very limited instability to work with. SPC highlights a Marginal Risk of severe weather but stops it short from reaching the local area and and am in strong agreement with that. Main shortwave will be unlikely to move into the area until after sunset tonight and so have limited the arrival of PoPs into the area generally as such. Will see PoPs ramp up quickly however as main h7 shortwave and related low-level jet begin to move into the area. Have highest PoPs for areas north of Highway 2, closer to the mid-level vort max which will slide west-southwest to east-northeast across South Dakota. Once again, instability will be limited given lack of appreciable surface heating but cooler mid-level temperatures will yield sufficient lapse rates to generate a few thunderstorms locally. PWAT values will be in excess of 1.25", which is exceeding the 90% moving average according to the SPC Sounding Climatology page. This should be favorable for a few locally heavy rainfall amounts but given fast motion of the shortwave, dwell time over any one location will be rather short so should see most if not all locations see rain amounts of less than three quarters of an inch. Given increased cloud cover, will see low temperatures remain more mild than the previous night as values fall to around 60 degrees. Saturday morning sees a lull in activity as the area is caught between the leading shortwave trough and the main trough that`ll move into the area later that evening. High temperatures on Saturday will range from low 70s across north central Nebraska to the upper 80s for far southwest into the southern Panhandle. As temperatures climb, will see the potential for moderate instability to develop. Mid-level flow will be strong, in the 30 to 40 knot range at h5, thanks to the aforementioned short waves moving through. This will allow for strong deep layer shear overspread much of the area. The question generally remains to be the level at which instability will manage to develop. SPC covers the entirety of western Nebraska in a Day 2 Marginal Risk for severe weather. Thinking the highest confidence in the threat for strong to severe storms to develop is generally along and south of Interstate 80. This thought is backed up by the NAM, SREF, and ECMWF. Thinking the threat for strong to severe is lower going north, but cannot completely rule it out at this point. Forecast sounding analysis from the NAM shows marginal lapse rates but ample dry air in the mid-levels which will be favorable for hail, perhaps up to 1" in diameter, and damaging wind gusts as delta theta-e values approach -30. Lows Saturday night will fall into the 50s across most the area. .LONG TERM...(Sunday through Friday) Issued at 300 PM CDT Fri Sep 6 2019 Beginning 12z Sunday. Will see dry conditions set up for the first half of the day on Sunday. Temperatures will be cooler than see on Saturday, with daytime highs ranging from the upper 60s across far north central Nebraska to near 80 in the southern tier of counties. Rain and thunderstorms are likely to return late Sunday into early Monday as a strong negative-tilt trough moves into the area. With favorable moisture hanging onto the area due to the absence of any moisture scouring frontal boundary, expect scattered to widespread rain and thunderstorms to develop and potentially lead to some locally heavy rainfall. WPC covers the whole area under a Marginal Risk of Excessive Rainfall as PWATs again look to reach values nearly 2 sigma-levels above climatological values. Activity will again be quick to move out by early Monday morning, however, given such strong forcing and high moisture availability, will see the threat for locally heavy rainfall once again. Early thoughts are for some areas to see around an inch of rain Sunday night through Monday morning, with some isolated areas potentially seeing higher totals. Will continue to monitor this closely given how wet much of the Sandhills have been. Extended outlook will see overall pattern shift to a more active one as large scale pattern favors troughing in the west to ridging in the east. This will put the central plains within general southwest flow aloft and more susceptible to larger systems. Main trough looks to eject onto the plains during the second half of next week, with increasingly wet weather expected through the work week. Temperatures will generally favor the 70s and 80s through that time with slight day-to-day variations possible. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 625 PM CDT Fri Sep 6 2019 Late evening and overnight there is increased potential for showers and thunderstorms with scattered coverage expected, mainly to affect the Sandhills and northern NEB, through tomorrow morning. Generally VFR conditions are expected, though with convective activity could see bases and ceilings down to low end VFR (less than 7 kft) to MVFR. Generally light rainfall is expected with any activity. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Jurgensen LONG TERM...Jurgensen AVIATION...Roberg
Area Forecast Discussion
National Weather Service Marquette MI
636 PM EDT Fri Sep 6 2019 .SHORT TERM...(This evening through Saturday) Issued at 408 PM EDT FRI SEP 6 2019 Water vapor imagery and RAP analysis show nw flow into the Upper Great Lakes btwn a ridge over the Rockies and troffing over eastern Canada into the ne CONUS. Shortwave that passed across the area last night is now heading into the Lwr Great Lakes. Next feature of interest is a shortwave dropping se from northern Manitoba. In the wake of last night`s system, clouds have been very slow to break up across Upper MI. In addition, cyclonic ne low-level winds helped to maintain widespread -dz across much of Baraga/Marquette counties thru the morning and into the early aftn. This -dz has recently ended, but spotty light pcpn is still lingering in portions of n central Upper MI. With the abundant cloud cover, temps have been held down to the mid 50s to lwr 60s for much of the area. Where clouds are finally breaking, temps will rise a little over the next couple hrs. Shortwave over northern Manitoba will drop se tonight, passing just n and e of Lake Superior late tonight thru Sat morning. Cold front associated with this wave will cross Upper MI late tonight and will exit by mid morning Sat. Since there hasn`t been strong column drying today, fcst soundings indicate moisture still lingering up to 5-8kft tonight ahead of the cold front. With modest deep layer forcing brushing the area, probably can`t rule out a few -shra along the front. Schc pops were utilized for a short time, corresponding with fropa, mainly across the n and e. With cyclonic flow and 850mb temps falling to around 5C Sat morning, there could be some lake enhanced -shra into the eastern fcst area. Otherwise, quite a bit of cu/stratocu should develop during the course of the day under 850mb caa. In addition, as nw-se oriented 120kt upper jet translates ese thru the day, Upper MI will become situated under the right entrance, and this should support considerable high clouds spreading overhead. So, with the combination of lower clouds and high clouds, expect the day to turn mostly cloudy. Will be a cool day with high temps in the upper 50s and lwr 60s for the most part. S central will reach the mid 60s. Will also be on the breezy side over the n central and e on Sat with gusts to 20-25mph. .LONG TERM...(Saturday night through Friday) Issued at 439 PM EDT FRI SEP 6 2019 Models indicate that a gradually progressive pattern will prevail. A mid/upper level ridge from the Southern Plains through the Rockies will give way to lowering heights this weekend as a strong shortwave moves in from the Pacific. As a result, northwest flow through the Great Lakes with mainly below normal temperatures this weekend will give way to southwest flow next week as a warm front lifts toward the region bringing in more widespread precipitation. After a drier period in the middle of the week, a mid/upper level trough will lift toward northwest Ontario with the associated warm front will moving across the area late next week with the potential for more widespread rain. Sat night and Sun, 850 mb temps dropping to near 2C with lake temps in the 13C-15C range, instability will be marginal to support any lake effect with increasingly anticyclonic flow and inversion heights around 5k ft. An isolated light shower or sprinkle cannot be ruled out north central but the probability was not high enough for pcpn mention. Surface high pressure will continue to dominate through Sunday with seasonably cool air (highs to around 60) as winds slowly veer to the northeast. Enough low level moisture will linger below the shallow inversion to keep skies mostly cloudy through the period. Mon-Tue, Models remain in good agreement with a warm front approaching the area by late Monday into Tuesday which will bring widespread to the region. Some thunder may also be possible by Tuesday as moisture/instability spread to the northeast. PWAT values climbing at or above 1.50 inches (nearly 200% of normal) will also support the potential for heavy rain as well. Wed, previous models consensus would push the higher pcpn chances east of the area by Wed as ridging begins to move in from the nw. However, the possibility of anothern weak shortwave approaching the area with the sfc boundary lingering to the south could support some additional pcpn into WI and possibly Upper Michigan, per 12z GFS/ECMWF. Thu-Fri, Models indicate another mid/upper level trough and associated sfc low lifting northeastward from the western/central Plains toward the Upper Great Lakes Thu night into Fri a warm front moving across the region. Expect another episode of widespread rain with this system. Strong moisture advection will also bring in enough unstable air for some thunderstorms and heavy rain. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 635 PM EDT FRI SEP 6 2019 A gradual influx of drier air will result in improving conditions thru the the evening hrs. At KSAW, MVFR conditions will improve to VFR by mid evening. A cold front will pass late tonight/early Sat. In the wake of the front, expect MVFR cigs to redevelop at all terminals Sat morning. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 408 PM EDT FRI SEP 6 2019 A cold front will drop se across Lake Superior tonight. Ahead of the front, winds will be under 20kt, but after the front passes, expect nw winds to increase, especially over the central and eastern lake where gusts to around 25kt will occur on Sat. Over the w, winds will fall back under 15kt. Winds will be mostly under 20kt for Sat night/Sun as high pres passes over or just n and e of Lake Superior. Winds will then be on the increase later Mon into Tue as the high pres departs and low pres tracks e toward the Upper Mississippi Valley. Not out of the question that there could be a period of easterly gales as the low approaches late Mon night into Tue morning. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Rolfson LONG TERM...JLB AVIATION...07 MARINE...Rolfson
Area Forecast Discussion
National Weather Service Phoenix AZ
553 PM MST Fri Sep 6 2019 .UPDATE... Updated Aviation section. && .SYNOPSIS... Seasonably hot weather will persist into the early part of the weekend before a significant cool down into next week. A weather system will move through the northern part of the region early Sunday bringing rain chances to mainly eastern Arizona, but also cooler conditions areawide. An unsettled weather pattern will persist through the first half of next week with shower and thunderstorm chances returning to much of Arizona while temperatures fall to below normal readings. && .DISCUSSION... Mid-upper level ridge extends from the Baja Peninsula northeastward into northern New Mexico, resulting in a light southwesterly steering flow. Meanwhile, conditions are seasonably moist with PWATs above 1.5 inches across the lower deserts. Latest ACARS soundings indicate two warm layers around 850 mb and 450 mb, which is resulting in considerable convective inhibition in the Phoenix area. However, along the periphery of the Valley, MLCAPEs have reached 500-1000 J/kg with less CIN. Latest local CAMs, HRRR and HREF are in good agreement and indicate isolated thunderstorms are likely in these areas, but will dissipate around sunset. Mean layer flow will become more westerly Saturday ahead of a weak short-wave trough across northwestern AZ and a deeper trough off the CA coast. Latest National Blend shows slight warming ahead of these systems, resulting in pockets of high Heat Risk across the Phoenix area. The day will start out quite warm, possibly breaking the record high min for the date of 87 degrees (set in 2011). Forecast high in Phoenix is 108 degrees, though 110 degrees is not out of the question. Latest long-range ensembles suggest this could also be the hottest day for the remainder of the year and an Excessive Heat Warning has been issued for the Phoenix area and Wickenburg. In addition to the heat, drier air will overspread the southwestern deserts, which will confine afternoon shower and thunderstorm activity to Gila County. && .PREVIOUS DISCUSSION... Moisture levels still look to be on the increase beginning Saturday, most likely Saturday night into Sunday as active monsoon conditions across northern Mexico should send moisture northward into Arizona. There is still some uncertainty for this weekend as any shift in the track of the shortwave may change our rain/storm chances. Models are at least in good agreement significant moisture will get pulled northward ahead of the advancing trough, but mostly show the moisture across eastern Arizona. The shallower depth of the trough also means we will likely see more of a westerly dry flow aloft. For now, best chances for rain fall across the eastern Arizona high terrain early Saturday night through Sunday, with at least a chance into the lower deserts later Sunday as a weak circulation across Sonora Mexico inches northward near the border. Model guidance diverges more for early next week with the European ensemble suite pointing toward best rain chances for south-central and eastern Arizona late Monday into early Tuesday whereas the GEFS mostly distributes QPF evenly Sunday night through Wednesday. Even though forecast confidence in the timing and positioning of any subtle disturbances early next week is quite low, it seems possible many locations from Phoenix eastward should see at least some rainfall at some point Monday through Wednesday. The potential storm severity and impacts look less impressive now that the shortwaves are more likely to pass farther to our north, but the increased winds aloft should at least keep a chance of some strong storms in the forecast early next week. Anticipated QPF amounts are just as hard to pin point, but with forecast low level mixing ratios near 12 g/kg this will at least bring some localized flooding potential across the eastern half of Arizona. As our long lasting high pressure ridge finally gives way to broad scale upper level troughing beginning Sunday, much cooler air will settle across the region. Forecast highs drop to between 100-105 on Sunday and bottom out in the middle 90s to around 100 degrees for Tuesday and Wednesday. Unfortunately, models agree the high pressure ridge will begin rebuilding late next week, eventually becoming centered over the Southwestern U.S. at some point the following weekend. The increasing heights aloft and drying conditions late next week will bring temperatures back to around or even a few degrees above normal at some point late next week. && .AVIATION...Updated at 0055Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: An isolated storm over northern portions of the metro (near/north of 101 Freeway) passing through the vicinity of DVT will cause enhanced gustiness for a brief time though it appears that it will dissipate before reaching SDL. Expect storms to remain outside of the vicinity of PHX and IWA. Couldn`t rule out outflow reaching PHX and causing a change to a crosswind but confidence in that is too low at this time to reflect in the TAF. Will continue to monitor. Otherwise, expect storms in the region to taper off with decreasing surface heating. Overall, westerly winds will prevail the rest of the evening with a slow trend toward downvalley/drainage patterns. Expect PHX will be the last of the TAF sites to lose the west wind tonight before light and variable toward morning. Also toward morning, anticipate isolated weak showers to pass by to the east possibly brushing IWA. Otherwise, anticipate the development of ceilings (bases AOA FL120) roughly between 10Z-16Z. Saturday`s storm activity is anticipated to remain well east of metro Phoenix. Anticipate a bit stronger southwest and west winds in the afternoon as well. Southeast California/Southwest Arizona including KIPL and KBLH: No pressing aviation concerns for the TAF sites though IPL is expected to have a modest sundowner this evening with a distinct change to westerly winds with some moderate gustiness early this evening. Expect west winds to continue at IPL through the period with some gustiness developing again Saturday in the afternoon. Meanwhile BLH will follow familiar diurnal trends with more noticeable gustiness Saturday afternoon. Aviation Discussion not updated for amended TAFs. && .FIRE WEATHER... Monday through Friday: Isolated to scattered showers and thunderstorms will continue each day on and off from Monday into Wednesday, especially from the S- central lower deserts to the higher terrain of east AZ. Max Ts will stay several degrees below seasonal normals through Thursday. Min RH will range from the teens over SE CA to above 20 percent elsewhere through Thursday before drying to the teens on Friday. Excellent overnight recovery through Tuesday night will fall to fair by Friday night. Winds will be light to seasonably breezy. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Excessive Heat Warning from 10 AM to 8 PM MST Saturday for AZZ534-537-540>544-546-548>551. CA...None. && $$ DISCUSSION...Hirsch PREVIOUS DISCUSSION...Kuhlman AVIATION...AJ FIRE WEATHER...Sawtelle
Area Forecast Discussion
National Weather Service Sacramento CA
327 PM PDT Fri Sep 6 2019 .SYNOPSIS... Cooling trend this weekend into the middle of next week, followed by a gradual warming trend late next week.. A slight chance of showers over the northern mountains next Tuesday afternoon and evening. Otherwise, dry weather is expected through next week. && .DISCUSSION... Satellite imagery and heat signatures show two wildfires burning very hot over western Tehama county this afternoon. Latest HRRR smoke indicates that smoke should remain mainly over the western portions of the aforementioned county, at least through Saturday. Elsewhere, dry conditions are being observed under brief upper level ridging. Current temperatures are running 2 to 7 degrees cooler than yesterday, with Valley highs in the 80s to low 90s. An approaching upper level trough will result in synoptic cooling across interior NorCal over the weekend. Weekend highs will be 5 to 10 degrees cooler than today, with Valley highs in the 80s, and low 60s to upper 70s over the mountains. At this time, models keep best dynamics north of the region, so interior NorCal should remain dry through the weekend. A fairly strong delta breeze can be expected on Saturday as the trough pushes into the West Coast. HREF probabilities suggest marine stratus advecting into the Delta region. Another upper level trough will move into the PacNW early next week, bringing much cooler temperatures. By Monday, temperatures are forecast to be around 2 to 10 degrees below normal. && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... Mean trough forecast along the West Coast next week with temperatures below average. Latest deterministic and ensemble guidance suggest possible showers or thunderstorms associated with the trough passage Tuesday afternoon into the early evening over the northern mountains. Therefore, have introduced precipitation chances given latest model trends. Ridging rebuilds late in the period, with temperatures trending near or slightly above average. && .AVIATION... VFR conditions next 24 hours. Gusts 15-25 kts vicinity Delta, winds generally under 10 kts elsewhere. Possible low cloud intrusion 12z- 18z Saturday for the Delta and Sacramento area airports. Breezy Saturday afternoon, wind gusts 25-35 kts vicinity Delta, Sacramento Valley 22Z- 02Z southerly wind gusts 15-20 kts. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$