Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/22/17

Area Forecast Discussion
National Weather Service Bismarck ND
930 PM CDT Wed Jun 21 2017 .UPDATE... Issued at 921 PM CDT Wed Jun 21 2017 Precipitation over southern portions of the area has now pushed well off to the east. The next batch of showers is now knocking on the door over the northwestern portions of the area as showers over northeast Montana continue to push to the east. Expect this to push into the area late this evening, and continue an easterly track overnight as an impulse rotating around an upper low located along the Manitoba/Saskatchewan border continues its easterly path. UPDATE Issued at 622 PM CDT Wed Jun 21 2017 Most storms have pushed to the east of the far southern James River Valley, though a boundary still shows up on radar that is over the southern/eastern portions of Dickey County, which is also denoted by some cloud growth on satellite. Therefore, will keep some low thunderstorm chances going for another hour or so before all pushes east. && .SHORT TERM...(This evening through Thursday) Issued at 300 PM CDT Wed Jun 21 2017 A cold frontal passage this afternoon will be followed by another surge of cold air advection and gusty northwest winds Thursday. We continue to downplay the potential for surface-based storms in our area of responsibility this afternoon since the current pace of a southeast-moving pre-frontal trough and cold frontal boundary suggests they will be mostly east of the area by the time capping is sufficiently eroded for convective initiation. However, there`s been just enough run-to-run consistency in HRRR iterations through its 18 UTC cycle to carry a slight chance of thunderstorms across Dickey County for a brief window in the late afternoon. Forecast soundings do suggest MLCAPE of 1000-1500 J/KG and deep-layer speed shear of 50 kt, sufficient for marginally-severe storms, but again we believe the probability of convective initiation in our area is low since the primary low-level confluence region will quickly be shifting east of the area. Today`s global and CAM model suites suggest another frontal surge marked by additional thermal packing in the 850 mb isotherms will push into northwest and north central ND tonight. Vertical motion associated with a strong but transient 140 kt 300 mb jet streak is expected to move eastward along the international border overnight and will likely yield a deep enough ageostrophic circulation atop the mid-level baroclinic zone in support of scattered showers. That frontal zone and its following cold air advection is then expected to continue southeast across the area early Thursday, away from the deeper forcing aloft associated with the upper-level jet streak. A dry forecast is thus in play tonight and Thursday in southwest and south central ND. Forecast soundings from the 12 UTC NAM and GFS both concur that we will have deep mixing to around 650 mb on Thursday in the cold air advection regime. Mean mixed-layer winds will be near 30 kt and peak speeds at its top will near 40 kt, especially northwest and north central. We weighted forecast winds toward the consensus of 12 UTC MOS guidance, which often verifies well in these cases. Those numbers suggest that a wind advisory may be required with a later forecast release if model trends hold steady, especially from Williston toward Minot Thursday afternoon. .LONG TERM...(Thursday night through Wednesday) Issued at 300 PM CDT Wed Jun 21 2017 Much cooler weather is still expected Friday and Saturday, but only a low chance of showers exists. The 00 and 12 UTC GFS and ECMWF and their ensembles held steady in forecasting a 500 mb trough across the region with temperatures at 850 mb in the 5 to 8 C range Friday and Saturday. Thus, highs will likely struggle to get out of the 60s F and overnight lows will be in the 40s F this weekend. Precipitation prospects will be limited by lackluster tropospheric moisture content, especially since it appears a stronger 500 mb low dropping through the trough may well pass east of the local area. A warming trend is still on track next week as flow aloft begins to return to a more zonal and progressive nature. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 622 PM CDT Wed Jun 21 2017 Gusty northwest winds develop over the area on Thursday. Otherwise, VFR conditions will prevail. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JJS SHORT TERM...CJS LONG TERM...CJS AVIATION...JJS
Area Forecast Discussion
National Weather Service Hastings NE
650 PM CDT Wed Jun 21 2017 .MESOSCALE DISCUSSION... Issued at 608 PM CDT Wed Jun 21 2017 In the interest of maintaining a flow of info...this is not the highest confidence watch we`ve ever issued. Updrafts are struggling to sustain themselves in an environment of weak shear and anemic BL moisture. The altocu are moving toward higher dwpt air...but with increased capping. This will definitely be one of those watches in which most of the watch is quiet. There is still potential for a couple svr tstms. The HRRR and 18Z NAM Nest still develop potent storms near the state line in the next 3 hrs. && .SHORT TERM...(This evening through Thursday) Issued at 255 PM CDT Wed Jun 21 2017 Aloft: Basically zonal flow was over the Nrn half of the CONUS and it will remain zonal thru tomorrow. However...a low was over Sask and it will cont heading E across Srn Canada. The Westerlies will begin amplifying and the zonal flow will gradually become more cyclonic..espcly tomorrow as a shortwave trof rotates around the low into MT/ND. Surface: Occlude low pres was over Sask. A cool front extended from ND back to NV...with a warm front from ND down into cntrl Neb then heading E to near OMA and into the OH Vly. This front has been reinforced with convective outflow. A 1005 mb low was near TIF with a trof extending SSW along the CO/KS border. This low and trof will be responsible for initiating sct tstms and tstm clusters this afternoon/eve. the Canadian low conts E it`s associated cool front will press further S and E...crossing Neb during the daytime hrs tomorrow...and finally clearing the CWA (N-cntrl KS) by midnight. Now: We cont to monitor sat/radar for convective initiation within the sfc trof from the Sandhills back into NW KS. SPC issued MD 1109 at 230 PM. Probability of watch issuance is currently 40%. Reasoning from 943 AM version of this product has not changed. Deep mixing and convergence within the trof should initiate a few tstms that will be outflow dominant. As usual...CAMs depict a wide variety of possibilities for convective coverage and evolution. Shear and instability are lowest within the trof. Any storms or storm clusters that develop and move E will be moving into an environment of increasing shear/instability. Current indications are that sct tstms/tstm clusters will develop and should be SE of the CWA by midnight. Be sure to monitor for any statements/watches/warnings from this office as well as support guidance from SPC. Thu: Tstms should develop along the approaching cool front over WY/SD tonight. This activity should cont E across SD during the morning...but will probably send an outflow boundary S into the CWA. It could trigger a few tstms during the AM N of I-80. During the afternoon/eve...a few tstms could develop S of a line from Beaver City-Columbus or even a little further S from Phillipsburg-Geneva. Am highly skeptical of much tstm activity over the NW 1/2 of the CWA as this area will be N of the front and strongly capped. Bottom line is I think our fcst is too extensive with tstm potential in the post-frontal environment. Where sfc-based tstms to develop (SE 1/2)...certainly large hail and damaging winds will be a threat. High temps are very uncertain over S-cntrl Neb due to the frontal passage. .LONG TERM...(Thursday night through Wednesday) Issued at 255 PM CDT Wed Jun 21 2017 This has been a hot month with 11 days of highs in the 90s at GRI. The rest of the month is looking substantially cooler...with a few days much cooler than normal. Aloft: Amplification of the Westerlies was just beginning. Over the next svrl days a broad trof will develop over the Nrn USA downstream of a ridge along the W coast. This trof will gradually shift into the Ern USA early next week with deamplification fcst toward the middle of the week. Surface: The cool front referenced above will sink SE across Neb during the day tomorrow and will be completely S and E of the CWA by midnight. Weak high pres will build over Neb/KS Fri. Meanwhile another cool front will plunge into the Nrn Rockies. It will arrive here and sink thru the CWA during the daytime hrs Sat. A big chilly and very strong high for summertime will expand over the Plns Sun-Mon from the Canadian Prairies to TX. It will then head into the SE USA Tue with return flow developing here on the Plns. Temps will be cooler than normal Fri-Mon...with at least one day of much cooler the normal Sat. Probably returning to near normal Tue and then above normal Wed. The cool fronts will shove the rich low-lvl moisture far S of the CWA thru Mon. Once it advects back into the rgn Mon night into Tue then the risk of tstms will return. A little/light rain generated by fgen should accompany the front Fri night into Sat...and possibly lingering into Sun S of I-80. Rainfall amts will be minor. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday) Issued at 650 PM CDT Wed Jun 21 2017 Significant Wx: LLWS tonight then WSHFT early Thu PM will necessitate changing RWYs. Tonight: VFR multi-layered clouds before midnight mostly AOA 7K ft. Sct SHRAs are moving in from the W and trying to become TSRAs but they are struggling. It is unlikely they affect the terminals ...but did include VCTS/CB at EAR. Cloud debris should decrease by midnight. S-SSW winds will average 10-15 kts and there could be some ocnl gustiness. LLWS. Confidence: Medium Thu: VFR with no clds AOB 10K ft until a cold frontal passage and WSHFT occurs early afternoon. Then some stratocu could form around 4K ft. The exact timing of the WSHFT/FROPA will need some minor refining +/- 1 to 2 hrs. Light SW winds will become vrbl then become NE and increase to 15-20 kts with gusts up to 28 kts. Confidence: Medium && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ MESOSCALE...Kelley SHORT TERM...Kelley LONG TERM...Kelley AVIATION...Kelley
Area Forecast Discussion
National Weather Service Green Bay WI
935 PM CDT Wed Jun 21 2017 Updated aviation portion for 06Z TAF issuance and new information added to update section .UPDATE... Issued at 921 PM CDT Wed Jun 21 2017 Convection has been slow to develop across the area this evening, likely due to stable air lingering across the area. Local meso plots indicate destabilization has occurred over about the southwest quarter of the state. That will expand northeast during the night, possibly quite rapidly as the LLJ increases. Storms over northern Minnesota have weakened as they shifted east of the main axis of instability. Increasing isentropic lift near the nose of the LLJ still looks favorable for thunderstorms across the area, but have delayed their onset and the highest PoPs until later in the night. The severe risk is also somewhat uncertain. Storms to the west have shown no sign of upscale growth. Right now the most likely path to getting severe weather tonight would be for a few individual storms to get strong enough to generate severe hail after midnight. Grids/ZFP with updated PoPs/Wx were just sent, will tweak/update the wording of the HWO and have that out shortly. && .SHORT TERM...Tonight and Thursday Issued at 239 PM CDT Wed Jun 21 2017 The main concern for tonight and Thursday is timing of thunderstorm activity along with the potential for severe weather. 19z surface analysis indicated a surface warm front draped from western Minnesota to south-central Iowa. Temperatures on the north side of the front were in the 70s across much of our area along with dewpoints in the middle 40s to middle 50s. To the south of the warm front, temperatures were in the middle 80s to lower 90s with dewpoints in the 60s. For tonight, models depict low level jet increasing to 50 to 55 knots as the warm front lifts northward. Elevated convection is expected to develop across central and east-central Wisconsin during the mid to late evening hours. Some differences by a few hours noted between the HRRR and the NAM Nest Models. The latest RAP 13 splits the difference in timing. Models also indicated strong 0-6 km shear of 50 to 60 knots, mid level lapse rates around 6 c/km to support rapid development of storms. Current thinking there would be some large hail at the onset, however wetbulb zero heights on the bufkit soundings were near twelve thousand feet that may lower the number of severe hail reports over an inch. Once the storms form, damaging wind gusts are possible as the storms organize. Most of the activity should be out of the forecast area shortly after sunrise. Low clouds will prevail tomorrow morning which should limit any convective activity. Torrential rainfall can be expected with some of the stronger storms which could lead to urban street flooding and ponding of water on area roadways. Did keep a small chance in the morning then increase chances again Thursday afternoon. Some of the meso models depicts a northern band of showers and storms heading for northern Wisconsin while another band of showers and storms develop across our southern forecast area and then merge late Thursday afternoon. Some of the storms could become severe with damaging winds and large hail, especially south of a Marshfield to Green Bay to Algoma line. High temperatures tricky depending on how much sunshine we get in the late morning and afternoon. .LONG TERM...Thursday Night Through Wednesday Issued at 239 PM CDT Wed Jun 21 2017 Focus in the long term will be ongoing convection Thursday night and on and off chances for more showers and thunderstorms through the forecast period. Thunderstorms (some potentially severe) are likely to be ongoing at 00Z Friday, especially south of a line from Marshfield to Green Bay closer to the location of the surface cold front. Thunderstorm chances will end from NW to SE overnight, with models showing the front and instability moving south of the forecast area by 12Z Friday. The rest of Friday looks mainly quiet. Models still show a weak shortwave to potentially produce a few showers in northern Wisconsin during the afternoon, with perhaps isolated thunder at best with MLCAPE and MUCAPE not more than 200 J/kg. GFS, ECMWF, and Canadian all depict an upper level trough over Ontario and the Great Lakes dominating the pattern across Wisconsin from Saturday through early next week. This flow will continue to bring mid- level shortwaves across the area and result in scattered shower and thunderstorm chances. Models are in less agreement on the exact timing and location of these shortwaves. The best chances seem to be in the Saturday afternoon/Saturday night and Monday afternoon/Monday night time periods. Stuck with a blended model solution which features chance and slight chance PoPs that coincide well with when the best energy moves though. On Tuesday the upper level trough moves east as an upper level ridge builds over the Upper Midwest. This is accompanied by high pressure at the surface and the best-looking day to see dry weather at the moment. Models continue to diverge on timing and track of a surface frontal system to approach the area around midweek. Continued with the blended model solution for now which brings in higher PoPs Wednesday. Temperatures will be running below seasonal normals through most of the long term period, especially across northern Wisconsin where highs will be about 10 degrees below normal Saturday and Sunday. Temps moderate some for the start of next week. && .AVIATION...for 06Z TAF Issuance Issued at 921 PM CDT Wed Jun 21 2017 The main aviation forecast concern continues to be the thunderstorm potential overnight and Thursday. It still looks like 2 rounds of storms are likely, but the onset of the first round has been delayed a bit by lingering stable air across the area. Will continue to try and indicate the most likely time for storms in the TAFs, though it certainly is possible those may need to be adjusted as the storm development unfolds. && .HYDROLOGY... Issued at 239 PM CDT Wed Jun 21 2017 Another round of heavy rain expected tonight into Thursday night. Average rainfall totals of 1 to 2 inches are possible south of a Merrill to Sturgeon Bay line. Locally higher amounts are possible if thunderstorms train over the same area. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE.........Skowronski SHORT TERM.....Eckberg LONG TERM......KLB AVIATION.......Skowronski HYDROLOGY......Eckberg
Area Forecast Discussion
National Weather Service Lincoln IL
910 PM CDT Wed Jun 21 2017 .UPDATE... Issued at 910 PM CDT Wed Jun 21 2017 A shortwave will continue to trigger showers and isolated storms across our northern counties the rest of the evening, and the HRRR is finally catching up with that scenario. Many other high res models are missing the boat with this wave. The stabilizing boundary layer has already limited cloud to ground lighting, as well as in-cloud lightning. However, a few strikes could still occur this evening, so isolated thunder was left in the forecast. Have increased our overnight clouds, especially in the south from Tropical Storm Cindy and in the north from ongoing convection. The clouds will increase lows a few degrees, and have adjusted up slightly in the south and north. Updates this evening have been to PoP/Wx, Sky, and temps. The latest forecast info is already available. && .SHORT TERM...(This evening through Thursday) ISSUED AT 240 PM CDT Wed Jun 21 2017 Weak convection today and associated cooling has kept the warm front from redeveloping north of the forecast area as originally expected. Isolated storms may still be possible near the boundary that extends from near Springfield east to near Paris through the remainder of the afternoon. However, ridging will once again build into the area overnight and the delayed translation of the warm front into Wisconsin is likely to occur late tonight or Thursday morning as strong insolation should assist in mixing. Temps should be higher across central Illinois compared to today due to the sun early on. Low-level moisture will increase as southerly flow becomes more prominent during the day but with 700mb temps progged to climb 4-5C in 24 hours and moving well above 10C capping of significant convection seems likely. We will keep any chc pops confined to near I-70 and southeastward. .LONG TERM...(Thursday night through Wednesday) ISSUED AT 240 PM CDT Wed Jun 21 2017 Model suite from 12z continues to push frontal system southeast into the forecast area late Thursday Night in conjunction with a short wave expected to move across the upper Mississippi Valley. The approach of the front should correspond with the period of best moisture advection from the remnants of Cindy and may lead to a brief period of heavier rain along and behind the front across central Illinois between midnight and Friday morning. Still some uncertianty of the evolution of the front and its interaction with the tropical moisture particularly across southeast Illinois Friday. Will retain likely PoPs southeast of I-57 with an diminishing trend from northwest to southeast as the front sags southeast and remnant circulation center moves far enough east to cut off overrunning potential. Clouds and cold advection behind the front should keep temps noticeably cooler Friday. The cool weather should persist into early next week as the area remains in cool northwest flow and 850 mb temps drop into the single digits through Monday prior to recovering by midweek. Several weak shortwaves will move through the northwest flow bringing periodic clouds and maybe a slight chance of a shower, but overall dry weather should dominate the are from the weekend into midweek. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 646 PM CDT Wed Jun 21 2017 A weak shortwave over eastern Iowa appears poised to push an area of showers into central Illinois this evening. HRRR is the main high resolution model indicating precip will progress across the I-74 corridor, with others keeping showers north the I-74 TAF sites. Based on radar and satellite trends, have added a VCSH for a few showers to affect PIA and BMI this evening. A steady decline in instability later this evening should preclude CMI from experiencing rain. Beyond that VFR conditions are expected to persist, under a veil of high clouds from tropical storm Cindy in the Gulf of Mexico. There are several models indicating a northward surge of low level moisture tomorrow afternoon, triggering MVFR cloud ceilings to develop from south to north. Have included that scenario in the 00z TAFs. Winds will generally remain S-SW over the next 24 hours. Wind speeds will increase tomorrow morning, with gusty conditions developing after 15z. Gusts should reach between 20-25kt at times on Thursday. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Shimon SHORT TERM...Barker LONG TERM...Barker AVIATION...Shimon
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1025 PM CDT Wed Jun 21 2017 .UPDATE...For 06z Aviation discussion below && .SHORT TERM...(This evening through Thursday) Issued at 332 PM CDT Wed Jun 21 2017 Visible satellite shows very little cu this afternoon across the vast majority of the area with the remnants of the morning MCS maintaining mid level cloud cover across far southern Minnesota. Chances for thunderstorms tonight will be focused in two areas, although those probabilities have also decreased. One area will be this evening over west central and possibly extending east into central Minnesota by late evening. A line of cu has formed along the cold front over North Dakota, which is progged to continue pushing southeast tonight to southern Minnesota by Thursday morning. A few storms may fire along it this evening in an environment characterized by MUCAPE of 1000 J/kg before they reach a much more stable airmass further east across Minnesota mid evening. The other area will be across southeastern MN and into central WI late this evening with the development of a LLJ. Given where the nose of this LLJ is expected to be around 06Z tonight, over southern WI, the most concentrated activity will be across central and eastern WI - east of our CWA. Maintained chc PoPs for both these areas, and a dry forecast from southwest to east central MN. CAMs have consistently been showing this all day and believe the global models are way too overdone with developing convection locally, especially the GFS which shows widespread precip occurring across southwestern MN this afternoon. As the front sags south into South Dakota overnight, additional storms may develop as it encounters deeper moisture. This activity will spread east Thursday across central and southern MN behind the front. Forecast soundings are quite stable behind the boundary with poor lapse rates and a cool boundary layer. Further south across southern MN, the close proximity to the EML and deeper low level moisture/higher thetaE should allow for widespread thunderstorms by afternoon. A few of them may become severe with 50-60 kts in the mid levels, but the best probability will be south of I-90 where the quasi-stationary front should be for much of the day. .LONG TERM...(Thursday night through Wednesday) Issued at 332 PM CDT Wed Jun 21 2017 Overall the long term period will be cool and fairly quiet as we will be under northwest flow with the main jet to our south. Saturday will bring a chance for showers and isolated thunderstorms with an upper level shortwave moving through the region. A warming trend appears to be on tap for early to middle of next week, which could bring more thunderstorm chances to the region. By tomorrow evening, the thunderstorm activity across our area will be pushing to the east, with most of the area drying out in the evening. Storms could linger from south central Minnesota through parts of west central Wisconsin. A few of these could be strong but the main severe threat looks to be in the short term period (during the day). All storms should be east of the forecast area by the overnight period. Behind this activity, the flow becomes northwesterly as the cold air advection ensues from the northwest. 850H temps will fall during the day Friday down to around 5 to 8 degrees C. At the surface, expect highs in the upper 60s to lower 70s. The cool northwest flow will continue through the weekend so highs will continue to be cooler than normal right through the weekend. On top of that, a compact shortwave will move through Saturday and spark showers and possible thunderstorms mainly during the afternoon. Continued to follow the GFS primarily for this evolution, but the ECMWF is slower and slightly farther north with this wave. The GFS and EC agree that the flow will become progressive next week and shift the west coast ridge to the east, displacing the deep longwave trough east of our area and beginning a warming trend into the middle of the week as southwest flow develops. With this, more low chances for thunderstorms are sprinkled into the forecast. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1025 PM CDT Wed Jun 21 2017 Model preference is a combo of the HRRR and NAMnest models, which feature a squeeze play of showers and thunderstorms moving into the area overnight from eastern SD and northern IA. Both feature a fairly rain morning for most of the sites, with embedded thunderstorm potential as well. Afternoon convective redevelopment (of stronger storms) still looks to be shifted south/east of most TAF sites (with the exception of possibly KEAU). MVFR cigs/vsbys are possible with thunderstorms, and also with/behind the frontal passage, but expect to be VFR by 00z Friday. Winds shift to the northwest behind the front. KMSP... There is a small threat for thunder early in the period, but the more widespread showers (with embedded thunder) holds off until around/after 10z. The morning looks to have activity around throughout, and then we scatter out during the mid afternoon. /OUTLOOK FOR KMSP/ Fri...VFR. Wind NW 10 kts. Sat...Mainly VFR. Slight chc -TSRA/MVFR. Wind NW 5-10 kts. Sun...Mainly VFR. Slight chc -TSRA/MVFR. Wind NW 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...BORGHOFF LONG TERM...SPD AVIATION...LS
Area Forecast Discussion
National Weather Service Norman OK
619 PM CDT Wed Jun 21 2017 .AVIATION... 0Z TAFs - Some storms could move into portions of NW OK later this evening. If storms do move into area, gusty variable winds could be possible. Otherwise, mid and high level clouds from the storms will stream across portions of the area tonight with high clouds around T.S. Cindy affecting other portions of the area later tonight into Thursday. T.S. Cindy could also affect winds at some TAF sites Thursday. && .PREV DISCUSSION... /issued 346 PM CDT Wed Jun 21 2017/ DISCUSSION... A persisting upper high across the southwestern U.S will continue to bring northwest flow across the southern plains, rolling in another round of showers and thunderstorms off the central high plains. Latest HRRR and Texas Tech WRF models suggest a few storms begin moving into far northwest Oklahoma around 10 pm, and not advancing very far before dissipating by early Thursday morning. So far, the risk for these storms is marginal, with up to golfball size hail and strong to severe wind gusts possible. The remainder of Thursday is expected to be dry with seasonably normal temperatures, with chances for more widespread TSRA returning on Friday through the weekend as a series of short wave disturbances in the upper flow come through. For Friday into Friday night, the storm and rain chances increase as an advancing surface boundary will interact with an upper wave. For this weekend, both GFS and ECMWF suggest additional storms possible as a few more short waves pass through, but uncertain with the timing or moisture available, so POPs will remain low until we get closer in time. One thing for sure, unseasonably cooler air lagging behind Friday`s cold front passage should be arriving by Saturday night. Temperatures for Sunday are expected to 10 to 15 degrees cooler than normal for early Summer. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 68 92 71 88 / 0 0 0 30 Hobart OK 67 94 70 90 / 0 0 10 30 Wichita Falls TX 66 94 72 94 / 0 0 0 20 Gage OK 67 96 66 85 / 20 0 30 20 Ponca City OK 67 91 70 85 / 0 0 0 30 Durant OK 70 89 72 91 / 0 10 0 20 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ 30/25/25
Area Forecast Discussion
National Weather Service Reno NV
845 PM PDT Wed Jun 21 2017 .UPDATE... Convection is decreasing across western Nevada this evening and has ended in the Sierra. A few showers and storms are hanging on from Lyon County east into the far northern part of Mineral County and eastern Churchill County. This activity is associated more with a weak trough that has focused the activity since about 630 pm. With the loss of heating we should see the activity end by around 10 pm. LAtest model guidance is in line with the previous guidance and shows activity developing again Thursday...but covering a smaller area mainly in the Sierra. Updates will be out shortly. && .PREVIOUS DISCUSSION... /Issued 246 PM PDT Wed Jun 21 2017/ SYNOPSIS... High pressure will bring much above average temperatures through the weekend, with cooler temperatures possible next week. Isolated to scattered thunderstorms are expected today near and south of Interstate 80, with isolated storms in Mono County Thursday through Saturday. Flooding will continue for the creeks and streams in Mono County and for portions of the Walker River. SHORT TERM... A weak upper trough axis is dropping south through western NV and the northern Sierra this afternoon. This, along with a weak surface trough extending through Mono/Mineral Counties, is providing focus for developing convection this afternoon. So far convection remains meek but this is expected to change as heating maximizes into the early evening. Recent HRRR runs have pegged the initial cell locations (eastern Mono County and out in central NV) better than the NAM/GFS. The HRRR shows isolated showers and thunderstorms congealing into scattered coverage this evening south of Highway 50 in western NV and over eastern Churchill County...with activity moving north (likely on outflows from earlier storms). Still, while confidence in the HRRR is growing due to its fairly consistent and so-far accurate depiction of convective location, steering flow is very light so storm motion will be driven by smaller-scale features such as storm outflows. These can be quite chaotic and unpredictable. Therefore, a broad-brush approach to evening storms (especially north of Highway 50) was taken to allow for possible locations for evening showers and thunderstorms. In any case, large surface temperature-dewpoint spreads should once again allow for storm outflow wind gusts over 50 mph out in the Basin and Range, with areas of blowing dust possible. As far as rainfall, with light storm motions stronger storms will be capable of dropping cores of moderate rain, although they could be rather narrow with the dry lower levels evaporating much of the precipitation on the edges of storms. Thursday, the upper level trough axis will move south into the central Sierra and the southern half of Nevada. This is expected to kick the focus for showers and storms down into Mono County and points south for a quieter day as far as afternoon showers and thunderstorms. Friday, the upper ridge settles back overhead for a rising temperature trend once again. With well above average temperatures and only minor subsidence aloft a few thunderstorms cannot be ruled out in the higher terrain near the Mono County crest. Therefore, a slight chance of storms was added to the forecast there. Over the weekend, the strong upper ridge remains overhead for highs well above the mid 90s to low 100s for lower valleys and mid 80s to lower 90s for Sierra valleys. Thunderstorms will continue to be possible with daytime heating in Mono County both days. However, on Sunday simulations are also beginning to show convection spreading into northeast CA and western NV as a weak impulse moves into northern CA (and induces a zephyr) on the periphery of the upper ridge. This makes sense and is shown in many simulations so storms were expanded out into western NV and up into northeast CA. LONG TERM...Monday through Wednesday... Next week, models continue to show a weakening of the upper ridge for an end to thunderstorms, increasing breezes, and a gradual cool down towards average high temperatures. Snyder Fire Weather... Another very hot and dry day today with thunderstorms developing this afternoon and moderate to poor mid slope recoveries for the next several nights. Thunderstorms are currently forming over the high Sierra in Alpine/Mono Counties and may move into the Sierra Front and the Basin and Range during the late afternoon/early evening along gust fronts from the initial thunderstorms in the Sierra. Thunderstorms should generally be of the wet variety since storm motions are expected to be slow, but lightning strikes can always happen outside of rain cores. Winds will be generally light out of the north today until thunderstorms form, then a quick change to south winds will be possible with gusts of 40 to 50 mph along thunderstorm outflows. Localized Red Flag conditions could easily occur for 1-2 hours as the gusts fronts from thunderstorms move into western Nevada. Hot and dry conditions are expected over the weekend with afternoon thunderstorms a possibility each day, however, storms are expected to be more confined to the Sierra after today. A trough is forecast to approach the west coast early next week which would cause an increase in thunderstorm activity and increased potential for critical fire weather conditions Monday and/or Tuesday as winds increase. -Zach AVIATION... && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday) Issued at 307 PM CDT Wed Jun 21 2017 A subtle upper level wave moving through central Nebraska helped spark scattered showers and thunderstorms over far NE Kansas and locations further north and east late this morning. This wave and the associated shower activity will push east of the area by the mid afternoon hours, with a second wave nipping at the departing system`s heels over SE Wyoming. A dryline across western Kansas will once again be the focus for thunderstorm development later this afternoon and evening. Given the lack of steering flow aloft, convection will not move terribly quickly off the dryline, and have hence slowed the arrival of POPs in the forecast after 21Z. This idea matches most of the CAM solutions such as the HRRR and high-res ARW/NMM cores. The main threats from this event would be large hail and damaging winds in the far western CWA given the SB/MLCAPE values over 4000 J/kg and near adiabatic low-level lapse rates from the surface to above 800 mb. Deep shear values will be lacking, thus the convective clusters will likely be non-steady state and new convection will be driven by previous convective cold pools. Steep mid-level lapse rates above a 30-40 kt LLJ may drive elevated convection into the night over central portions of the CWA, but the lack of deep shear should once again keep the severe threats to a minimum. The upper level pattern will amplify over the northern Rockies during the day on Thursday as a longwave trough digs southward from western Canada. As this wave approaches, the cold front over Nebraska will begin to shift ESE and reach the NW corner of the CWA at the end of the period. High temperatures on Thursday will be near what they reached yesterday and today--reaching the low 90s east to upper 90s west. Heat indices will push 100 degrees in most locations. .LONG TERM...(Thursday night through Wednesday) Issued at 307 PM CDT Wed Jun 21 2017 Thursday night into Friday morning, broad cyclonic flow resides over the northern tier of the CONUS. A deep upper level closed low will amplify short wave energy over the Northern Rockies and eventually send this impulse into the Northern and Central Plains. The closed low will begin to fill into the overnight and thus weaken as it shifts east into the Northern Great Lakes. Best forcing for large scale ascent stays north of the forecast area and leaves northeastern KS under a capped environment much of the day with a strong EML in place. NAM and GFS solutions are more consistent with higher moisture set up and a well mixed boundary layer in place but also strong CINH in place. Both solutions focus gradient of instability along the front as it moves through southern NE late afternoon and into the northeastern KS by early evening. MLCAPE and SBCAPE on the order of 1500-2000 J/kg as it makes its way into northeast KS within marginal deep layer shear with best deep layer shear lagging well behind the front should lead to isolated to widely scattered storms probably at best. Most CAM solutions that go out far enough to include this forecast period are suggesting that any discrete multicells that do develop quickly become a disorganized cluster or quasi linear set up into the evening. The ECMWF solution is similar to the overall concept that the NAM and the GFS arrive at, but slow the overall progression of the cold front slightly with overall less moisture pooling to help initiate activity in the first place. All this being the case, it leads to a low probability set up that severe storms will be long lasting or maintained. The threats that do exist would be possibly some large hail and mainly a wind threat lasting for a short time frame (before boundary layer stabilzation takes place) where storms can break the cap and get going. Therefore, have gone with slight to some chance POPs in the early evening on Thursday. On Friday day time frame high pressure ridge noses into the area and should leave a nice day in place with subsidence aloft. Temps will be in the 80s with dew points in the 50s. Saturday, there may be some showers and storms that make their way into portions of the area coming off the high plains associated with another impulse rotating around the broad cyclonic flow aloft that just continues to skirt the area once again. It`s a low chance set up and one that won`t have a lot of support but too much model variance at this point to determine one way or the other. Latter part of the weekend into the first half of the upcoming week, the pattern becomes more progressive with a low amplitude ridge working into the area and activating the lee trough. This will bring some return flow of moisture back into the area and possibly lead to a couple on and off chance of precip with isentropic lift developing and advecting over the area. All in all, temperatures will be more near normal and comfortable compared to recent heat. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 625 PM CDT Wed Jun 21 2017 VFR prevails at terminals with main concern being the low level wind shear and dissipating convection across western Kansas. Sfc winds are expected to become light around 5 kts aft 01Z with the low level jet increasing around 1000 feet up to 40 kts. This is expected to persist through sunrise before southerly sfc speeds increase above 10 kts near 14Z. Current convection in western Kansas is expected to weaken as it shifts east and southeast. There is a slight chance for a few thunderstorms to reach KMHK by 11Z, hence the VCTS mention. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Skow LONG TERM...Drake AVIATION...Prieto