Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/11/18

Area Forecast Discussion
National Weather Service La Crosse WI
624 PM CDT Fri Aug 10 2018 .SHORT TERM...(This evening through Saturday) Issued at 314 PM CDT Fri Aug 10 2018 At 3 PM, scattered showers were moving south across north-central Wisconsin and northeast Iowa. This was associated with a weak convergence boundary between the upper level ridge to our west and the trough located over the Great Lakes. Mixed-layer CAPES have climbed up to 1500 J/kg. However, like much of this summer, there is little shear. As a result, they develop and then quickly rain themselves out as they shut of their supporting updraft. With the loss of diurnal heating late this afternoon and early evening, they will quickly dissipate. For late tonight into Saturday, soundings show light winds up to 800 mb. However, they also show temperature-dew point spreads of 2F at 11.12z. As a result, put the greatest concentrations of fog in the Mississippi tributaries and Wisconsin River Valley. From late tonight into Saturday, the HRRR shows that smoke from the western Canadian wildfires will spread into the area. The highest concentrations will be along and west of the Mississippi River. This smoke may briefly lower visibilities to as low as 5 miles at times. The Minnesota Pollution Control Agency has issued an Air Quality Alert for the entire state through 12 PM Sunday. On Saturday afternoon, another short wave trough will move southeast through the Great Lakes. The CAM models indicate that a convergent boundary will be located across central Wisconsin. Like this afternoon, there will ML CAPES up to 1500 J/kg with weak shear, so only expecting scattered diurnal showers and thunderstorms. .LONG TERM...(Saturday night through Friday) Issued at 213 PM CDT Fri Aug 10 2018 500 hPa ridging continues across the region through Monday as a Canadian trough cuts off across the lower Great Lakes into the Ohio River Valley and a secondary cut-off low meanders across the Central /Southern Plains. Skies look mostly sunny/clear both days with highs generally in the 80s. Tuesday into Wednesday, a northern stream short-wave moves across the Dakotas into Minnesota and may ingest the secondary cut-off low across the plains. These interactions complicate the overall flow pattern and differ from model to model. End result in increasing precipitation chances Tuesday into mid-week with POPs in the 20 to 40 percent range. Still early, but severe weather looks unlikely at this time. Despite ample instability ahead of an eastward advancing cold front, deep shear is lagging behind the boundary and generally between 20 and 30 kts. Synoptic flow becomes even muddier to end the week with the potential for additional short-waves in a weak quasi-zonal pattern. Consensus POPs from 20 to 30 percent seem reasonable, but overall predictability is low. Temperatures mid-week through Friday do appear to cool off a bit behind Tuesday night`s frontal passage with daily highs generally in the 70s. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 624 PM CDT Fri Aug 10 2018 Diurnal cumulus continue to dissipate as the sun descends toward the horizon. Skies to generally be cloud-free tonight, but there is the smoke from the NW CONUS and SW Can wildfires that the NW to N mid/upper level winds will be spreading across the area for later tonight and Sat. Models indicate a thicker plume of smoke to be over the area Sat and with diurnal mixing, some reductions in vsby are likely, especially by later morning. This is always hard to fcst, but several upstream vsbys in N MN in the 4-7SM range. Included 6SM FU at both KRST/KLSE for much of Sat. Another favorable night for radiational valley fog formation. However, sfc dew points some 5F to 10F lower this afternoon vs. Thu afternoon, and may limit the BR/FG a bit, especially in the broader MS river valley. Only carried a 5SM BR FU at KLSE 09-14z at this time. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Boyne LONG TERM....Boyne AVIATION.....RRS
Area Forecast Discussion
National Weather Service Bismarck ND
936 PM CDT Fri Aug 10 2018 .UPDATE... Issued at 936 PM CDT Fri Aug 10 2018 We added a mention of fog from 09 to 14 UTC over east central ND and in particular the James River valley with this update. That was predicated by seasonably high boundary layer moisture content with surface dewpoints in the 60s to near 70 F in that region as of mid evening, increased particulates for condensation resulting from the low-level smoke concentration, and persistence given the fog that occurred there last night and early this morning. Recent HRRR cycles have also been simulating fog development there, and locally dense fog is certainly possible. Otherwise, only minor changes were made to the remainder of the forecast, though we did reduce overnight lows ever-so-slightly in western ND where a drier air mass and less smoke concentration closer to the 500 mb ridge axis may promote a bit greater radiational cooling. The eastward advancement of the ridge axis aloft could reduce smoke in parts of southwestern and south central ND further on Saturday, as the 18 UTC HRRR-smoke simulation suggested, but we have maintained a broad-brushed approach in carrying a smoke mention in all of our forecast products for all of western and central ND through the weekend at this juncture. Later trends in observational and model data may allow us to refine spatiotemporal smoke trends slightly. UPDATE Issued at 702 PM CDT Fri Aug 10 2018 Little change with this update cycle as we merely blended observed trends and rapid-refresh guidance into hourly forecast fields for the evening. As of 00 UTC, a weak surface boundary is noted from northwest into central ND from about Stanley to Bismarck, with higher boundary layer moisture content to its east where dewpoints are generally over 50 F, but this feature will have very little in the way of impact on sensible weather through the evening. && .SHORT TERM...(This evening through Saturday) Issued at 327 PM CDT Fri Aug 10 2018 Currently, surface high pressure was over the Manitoba/North Dakota border. The upper level ridge continues to build over the Rockies and western Plains. The upper level ridge will build further into the Northern Plains this weekend. This anomalously strong thermal ridge is forecast to have H850 temperatures in their climatological 99th percentile for western and most of central ND Saturday. Record to near record temperatures are forecast for Saturday. See the table in the long term section for forecast and record temperatures. In addition, the smoky haze from fires in the western US and Canada will remain with us on Saturday. .LONG TERM...(Saturday night through Friday) Issued at 327 PM CDT Fri Aug 10 2018 Record to near record temperatures and a fire weather watch on Sunday are the main highlights in the long term. On Sunday the thermal ridge reaches its peak over western and central North Dakota. The H700 temperatures are forecast to reach their 99th to its maximum in western North Dakota. We are looking at widespread max temperatures in the lower 100s across the western half of North Dakota, with mid to upper 90s from the Turtle Mountains to James Valley. The latest model runs are more consistent on the cold front timing and are projecting the front entering northwestern North Dakota late Sunday afternoon, and reaching central North Dakota around daybreak Monday morning. Southerly winds are forecast to increase on Sunday to 20-25 mph. See the fire weather section below for details regarding fire weather impacts. Regarding temperatures, record to near record temperatures are forecast for both Saturday and Sunday: Station Saturday`s high Sunday`s high record forecast record forecast Williston.....102 101 102 103 Dickinson.....102 100 102 102 Minot.........101 102 101 103 Bismarck......104 101 102 102 Jamestown.....103 93 102 95 The cold front moves southeast slowly across the state Monday, with a chance of thunderstorms developing along the front mainly Monday evening and night. More zonal flow aloft develops thereafter, with periodic chances of showers and thunderstorms. A relative cooler period with highs in the 70s and 80s Tuesday through Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 936 PM CDT Fri Aug 10 2018 Smoke will continue across most of western and central ND through the weekend, with occasional MVFR visibilities likely, especially in northwest and central ND late tonight and Saturday morning. Additionally, fog may develop over east central ND, including the James River valley and the KJMS terminal, from about 09 to 14 UTC, with potential IFR conditions. Winds will be light, and should become predominately southerly on Saturday around 10 kt as weak surface low pressure develops over Montana beneath the strong ridge of high pressure aloft. && .FIRE WEATHER... Issued at 327 PM CDT Fri Aug 10 2018 Near critical fire weather conditions are possible Saturday. Critical fire weather conditions are possible Sunday. A fire weather watch has been issued for many western North Dakota counties...including Williams and Mountrail counties and all counties south and west of the Missouri River. Very warm and dry weather continues into the upcoming weekend. Widespread high temperatures in the low 100s are expected across western and central North Dakota Saturday and Sunday. These conditions will allow grassland fuels to continue to transition towards curing. Saturday: High temperatures in the lower 100s are expected over western and central North Dakota with minimum relative humidity values of 10 to 20 percent. Wind speeds are expected to be rather light Saturday, generally 15 mph or less. Our confidence in stronger winds, which would push conditions into the critical territory, is not high enough at this point to issue any fire headlines, but near critical fire weather conditions are expected Saturday, especially southwest. Sunday: Forecast confidence continues to increase that winds on Sunday may reach 20-25 mph with higher gusts during the peak heating of the day, when relative humidity values are usually the lowest. A cold front is forecast to enter far northwestern North Dakota late afternoon Sunday, and push slowly through western and central North Dakota Sunday evening into Monday morning. Mixing up to 8,000 feet ahead of the front should allow southerly winds of 20 to 25 mph to mix down to the surface on Sunday. Speaking with the NDFS, grassland fuels over far western North Dakota appear very dry, especially so south of McKenzie County. The fuels farther north and east are not as far along in curing, but may be able to carry fire very easily should 20-25 mph winds with low relative humidity set up. FMO was not concerned with Renville, Ward or McLean county. Thus, even though weather conditions of less than 20 percent RH and winds of 20-25 mph are expected across all of western and nearly all of central ND (except James Valley)...will keep the fire weather watch confined to west of the Missouri River and just north of it in the northwest part of ND. A NWS employee account of dry grasses in western Mountrail County and eastern Williams - thus wanted to include areas in eastern Williams and western Mountrail counties in the watch. As the front approaches, we do not expect the southerly winds to reach criteria over Divide and western Williams counties, but we may see eastern Williams reach criteria. && .BIS WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Sunday afternoon through Sunday evening for NDZ009-010-017>020-031>034-040>045. && $$ UPDATE...CJS SHORT TERM...JV LONG TERM...JV AVIATION...CJS FIRE WEATHER...JV
Area Forecast Discussion
National Weather Service Cleveland OH
1004 PM EDT Fri Aug 10 2018 .SYNOPSIS... A stationary front from west to east across the area will move little tonight. A weak wave of low pressure will move east along the front and force the front south as a cold front Saturday. A ridge of high pressure will build slowly east over the area during the rest of the weekend and persist through Monday. Low pressure will move north across western Pennsylvania by Monday night into southern Ontario Canada Tuesday. && .NEAR TERM /THROUGH SATURDAY NIGHT/... A quiet evening is expected over northern OH and nw PA in the wake of scattered to numerous showers and thunderstorms. Just the far southwest part of the CWA near MNN to Knox County has any lingering chance of showers/storms for the next hour or two. The rain has moistened the boundary layer and fog has already begun to form near CAK and BJJ. We can expect more fog to form generally along and south of US-30 and a bit further north too. Will mention patchy fog in the zones away from the lake. Current overnight low temperature forecast seems reasonable with lows ranging from near 60 in inland nw PA to near 70 on the islands being surrounded by warm Lake Erie. Drier air will filter south into the region on Saturday and help stabilize the region. POPs have been lowered in the southern counties. The upper level trough is expected to deepen and become more pronounced by Saturday morning resulting in the development of an upper level low pressure system overhead. This trough and subsequent low pressure system will trigger cyclogenesis over the Carolina Coast. This low will begin a slow track north toward the eastern portions of the forecast area by the end of the weekend. As the surface ridge tries to build in behind the front Saturday, some drier air will push in as well and will bring an end to the threat for showers and thunderstorms during the day Saturday into Saturday night. As upper level low pressure lingers over the forecast area and surface ridge builds toward the local area, expecting temperatures to be struggling to get into the lower 80s in the east but will make it to the lower 80s west. Overnight lows will not change much and stay in the 60s. Leaning in the direction of a blend of the HRRR and GFS models with this forecast package as these two appear to be doing well with handling the convection over the local area at this time. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... Upper level low will be over central Ohio on Sunday with chances of showers/thunderstorms remaining in the forecast. The thunder will spike late afternoon then taper off during the evening. These conditions will likely linger into Tuesday as the low only slowly drifts eastward. Best chances of rainfall will be from Mid Ohio to NW PA. Temperatures will be very close to seasonal averages through the short term forecast. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Upper level low pulls away to the east on Tuesday night. Dry conditions with a brief period of ridging expected before moisture returns to the area ahead of the next trough on Wednesday. Models depict an upper low meandering out of the southern Plains that will be pulled north across the area ahead of another trough moving through the northern stream. It will take some time for the atmosphere to moisten on Wednesday and and lowered pops for the first half of the day. Thursday looks like the wettest day of the week as these features merge overhead. Temperatures will be seasonal with the warmest day expected on Wednesday with lesser amounts of clouds and showers. && .AVIATION /00Z Saturday THROUGH Wednesday/... Showers and thunderstorms have moved south of the region and weakened but have moistened the boundary layer. Cloudiness has diminished. Dewpoints are rather high in the mid to upper 60s. In rain cooled areas the temp/dewpoint spread is less than 5 degrees and winds are light. Conditions appear to be favorable for fog development in areas away from Lake Erie especially south of US-30 after 09Z which would affect YNG CAK and MFD and perhaps FDY terminals. Visibility may drop below 2SM and Cigs may form and lower below 1000 Ft. Fog should dissipate by mid to late morning in the 1330-1500 UTC time frame. Less humid air will gradually work south across the region Saturday afternoon so VFR conditions are expected. OUTLOOK...Non-VFR possible through Monday and possibly Wednesday. && .MARINE... Cold front will continue to drift southward toward southern Ohio this evening. So expect to see northeasterly wind persist on the lake into Saturday. Winds will weaken slightly Saturday night but a surface trough will then persist over the central Great Lakes into Tuesday. Current thinking is that the longer fetch may nudge winds to 2 to 4 feet on Sunday for the central lake. This will need to be watched closely with only slightly higher winds nudging waves up to small craft advisory levels. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Lombardy NEAR TERM...LaPlante SHORT TERM...Mullen LONG TERM...KEC AVIATION...LaPlante MARINE...Mullen
Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
642 PM CDT Fri Aug 10 2018 .UPDATE... Issued at 642 PM CDT Fri Aug 10 2018 Please see the 00Z Aviation discussion below. && .SHORT TERM...(This evening through Saturday) Issued at 316 PM CDT Fri Aug 10 2018 An upper level trof will move past the Arrowhead this evening. Moisture is a bit lacking, but what is available will lead to a few thunderstorms. Thermodynamic profiles suggest a general thunder scenario. Rainfall amounts will be on the light side however. Otherwise, Upper level and surface ridging will build across the area tonight and Saturday. Smoke will continue to drift over the region thanks to a northerly flow aloft bringing the smoke from Canadian fires into the region. An air quality alert is in effect until noon Sunday. Warm minimum and maximum temps tonight and Saturday. .LONG TERM...(Saturday night through Friday) Issued at 316 PM CDT Fri Aug 10 2018 The upper ridging persists through Monday. At the surface, a southwesterly flow develops Sunday afternoon through Monday evening. This will continue to bring a warm and humid airmass into the region. Monday night finds a cold front beginning to affect the international border area. This front will be aided by a piece of vorticity moving along this area in a westerly flow. Expect showers and a few thunderstorms to develop along the border and drift southeastward. The cold front slowly progresses into the forecast area through Tuesday night before stalling out. Meanwhile, an upper level wave will be dropping south out of south central Canada to the northern Minnesota border by 12Z/7am Wednesday. Additional showers and storms will percolate across the region, diminishing Wednesday night from northwest to southeast. The ridging returns on Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 642 PM CDT Fri Aug 10 2018 High pressure will remain in place over the Upper Mississippi River Valley through the forecast period. Flow aloft will be northwesterly, which will advect smoke from Canadian Wildfires into the region. This will bring some visibility reduction with MVFR conditions anticipated at INL. HIB/BRD will also see some visibility reduction, but should remain in the VFR range this evening. As was the case yesterday expect radiation fog to develop as the airmass is essentially the same as it has been the past two nights. Uncertain how the smoke will impact the fog development, but mostly utilized persistence in forecasting fog formation and when the lowest visibilities are expected. As of right now anticipate MVFR to IFR visibilities, but lower are possible. Just have held off at this point from lower due to the smoke over the region. Fog will dissipate around 12Z to 14Z as the mixed layer develops. Expect smoke to impact terminals on Saturday per HRRR smoke guidance with some visibility reduction. Winds will be less than 10 knots through the forecast. && .PRELIMINARY POINT TEMPS/POPS... DLH 62 88 62 86 / 0 0 0 0 INL 57 90 63 91 / 0 0 0 0 BRD 63 88 64 87 / 0 0 0 0 HYR 61 87 59 87 / 0 0 0 0 ASX 62 85 59 86 / 0 0 0 0 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...None. && $$ UPDATE...WL SHORT TERM...GSF LONG TERM...GSF AVIATION...WL
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1006 PM CDT Fri Aug 10 2018 .UPDATE... A broken line of storms has developed oriented northeast to southwest from Kendall County down to Dimmit County. This line is very slowly moving to the east. These storms are producing copious amounts of lightning, moderate to heavy rain, and gusty winds. A gust front has begun to move out ahead of the leading edge of the convective line, which may begin to decay the intensity of the convection and hinder its eastward progress if it manages to cut the storms off from their warm, moist inflow source. In the short term, grids have been updated for current trends. PoPs out west have been decreased considerably where rain has ended, with PoPs increased considerably where storms are ongoing and heading in the near term. Convective allowing models have been performing quite poorly today, with the most recent HRRR runs initializing terribly. Thus, I am not putting too much stock in what they are showing for the remainder of the evening and overnight hours. For now, essentially using a blend of various models for PoPs in the 1 am to 7 am (6z to 12z) time frame, with this resulting in decreasing PoPs a bit, especially across the western areas and into the Hill Country (from 70% down to 50%). && .PREV DISCUSSION... /ISSUED 704 PM CDT Fri Aug 10 2018/ AVIATION... Scattered to numerous showers and storms continue around DRT and points to the northeast. Outflow boundary continues to move closer to the San Antonio sites and latest runs of the HRRR does show some isolated activity for the I35 sites later this evening. Will include the mention of VCTS for the San Antonio sites and VCSH for AUS for later this evening. Beyond the near-term, it is tough to pin down exact precip timing, but think the best chances will be in the afternoon hours for all sites tomorrow and will include vicinity activity. There is a small chance for some MVFR ceilings after daybreak tomorrow, but opted not to include the mention of that for now. Changes to the TAFs regarding precip is likely as timing differences become known. PREV DISCUSSION... /ISSUED 250 PM CDT Fri Aug 10 2018/ SHORT TERM (Tonight through Saturday Night)... Through the remainder of the afternoon and into the evening focus for showers and thunderstorms will be across the southern Edwards Plateau and into the western Hill Country, where forcing along differential heating/remnant outflow boundary is best. Several CAMs models suggest upstream convection developing southward into portions of Val Verde, Edwards, Real, and Kerr counties. Convection could build further south toward the U.S. 90 corridor through the mid evening into the instability axis, where SPC analysis indicated MLCAPE approaching 3000 J/kg. A few strong storms are possible with inverted V soundings out west indicating potential for gusty winds. However main threats will be lightning and some brief heavy downpours. Forecast confidence overnight is low, however there are some signals in a few of the CAMs of development of isolated to scattered convection farther east into the CWA. The mid and upper level trough axis will deepen Saturday and Saturday night, with the base of the trough orienting itself across the northwest CWA. Convection during the day on Saturday is hard to pinpoint, and may be mainly diurnally driven in the afternoon closer to outflow boundaries left over from overnight convection. However focus Saturday night in most of the models appears to be through the southern Edwards Plateau, western Hill Country and Rio Grande as a weak inverted low level trough develops over the region, low level jet increases, and larger scale ascent/forcing in the base of the trough align. There is the potential for locally heavier pockets of rainfall through this region, given climatological high precipitable water values and relatively slow storm motions and potential for mergers. Some streamer convection will also be possible farther east into and east the I-35 corridor. LONG TERM (Sunday through Friday)... The base of mid and upper level trough axis will remain across the far northwest CWA Sunday and Sunday night. As ridge across the northern Gulf of Mexico nudges slightly to the west the deep moisture feed focuses mainly near I-35 west to the Rio Grande. Difficult to pinpoint evolution of storms during the day on Sunday and may be very dependent on what happens Saturday night. However, models are consistent with showing potential for another nocturnal event Sunday night across the Hill Country and Rio Grande given the deep moisture over the area, larger scale ascent with the trough, and stronger low level jet orientation more perpendicular to the escarpment. While generally the southern Edwards Plateau, Hill Country, and Rio Grande could use the rainfall given the drought conditions, there is the possibility of some pockets of rainfall rates that develop that could produce localized flooding. We will highlight this in the HWO. Drier air will gradually build into the region from east to west Monday through Monday night as the mid and upper level ridge flattens over the area and trough lifts to the north. This will result in drier and warmer conditions developing Tuesday through the remainder of the forecast. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 75 92 75 91 76 / 50 50 60 40 50 Austin Bergstrom Intl Airport 75 92 74 92 76 / 50 50 60 40 40 New Braunfels Muni Airport 74 92 75 92 75 / 50 50 50 40 50 Burnet Muni Airport 73 89 72 88 72 / 60 50 60 50 70 Del Rio Intl Airport 77 90 73 85 73 / 50 50 80 70 70 Georgetown Muni Airport 74 91 73 90 75 / 50 60 60 40 50 Hondo Muni Airport 74 94 74 91 74 / 70 40 60 60 70 San Marcos Muni Airport 76 92 74 92 76 / 50 50 50 40 50 La Grange - Fayette Regional 77 93 75 94 77 / 30 50 40 30 20 San Antonio Intl Airport 76 93 76 91 77 / 60 50 60 50 60 Stinson Muni Airport 77 93 76 93 77 / 50 40 60 50 60 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Mesoscale/Aviation...Hampshire Synoptic/Grids...BMW
Area Forecast Discussion
National Weather Service Hastings NE
557 PM CDT Fri Aug 10 2018 .SHORT TERM...(This evening through Sunday) Issued at 218 PM CDT Fri Aug 10 2018 The most notable feature currently is the smoke that has moved in from the fires over over Washington state and British Columbia. This has lead to hazy skies, but has remained mostly aloft, so we have kept any mention of smoke out of the grids. The HRRR and RAP smoke models indicate that we should see this smoke slowly become thinner through tonight and tomorrow. Other than that, the short term forecast is pretty quiet. The forecast area will remain under the influence of an upper level ridge through Sunday, which should lead to dry conditions. Winds will become southerly Saturday and Sunday but will remain relatively light as the weak surface high pressure area moves to the east. Temperatures will be similar to today, with highs in the upper 80s to low 90s. .LONG TERM...(Sunday night through Friday) Issued at 218 PM CDT Fri Aug 10 2018 The quiet pattern will begin to change on Sunday as models develop an upper low over western Texas and slowly moves it through the TX/OK panhandles and into southwest Kansas. There is some question on how quickly deep moisture will return to the area with this feature, but the model consensus would bring at least some chance into souther parts of the area late Sunday night, with a better chance for the entire area Monday and Tuesday. This feature will be very slow to move through the area, and it will take a northern stream wave to finally kick it out of the area Tuesday night into Wednesday. As a result, I am cautiously optimistic that the southeastern portions of the forecast area (that are also some of the driest spots) will see beneficial rain. Although its still early, the overall threat for severe weather looks somewhat limited due to a lack of low-level shear. Nevertheless, its still August so we can`t completely write off the threat at this point. Increased cloud cover will keep temperatures a bit cooler through the beginning of the week, with highs only forecasted to reach the low to mid 80s each day. Periodic chances for thunderstorms continue Wednesday through Thursday night as remain in a messy zonal to slightly northwesterly upper level flow pattern. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 547 PM CDT Fri Aug 10 2018 Smoke/haze has reduced the visibility at KGRI to 5SM for the majority of the day. Have maintained a slightly reduced visibility into tonight, before increasing. Cloud cover will be fairly minimal with a scattered mid/high deck possible heading into Saturday. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ SHORT TERM...Mangels LONG TERM...Mangels AVIATION...Fay
Area Forecast Discussion
National Weather Service Wilmington NC
940 PM EDT Fri Aug 10 2018 .SYNOPSIS... Bermuda high pressure anchored offshore and an area of low pressure inland, will bring an increase in showers and thunderstorms through the latter half of the weekend into early next week. Rain chances begin to decrease by the middle of next week, as low pressure moves north of the region. && .NEAR TERM /THROUGH SATURDAY/... As of 9 PM Friday...Upper level impulse over western NC generating convection well to the west of the FA attm. This feature will get close enough to the area overnight that it could kick off a shower or storm but it will be fighting stability induced by nocturnal cooling. Have lowered pops to slight chance all areas overnight with no pop eastern areas until about 2 AM. Forecast mins in the middle 70s look good. Previous discussion from 3 PM follows: Cu building along northern border and just north of local area this afternoon in best moisture and lift just south of sfc front. Modified sounding showed ML CAPE up around 2k and PW increasing to over 2 inches with DCAPE up around 735 by late this aftn. Dry air and subsidence in the mid levels has provided a bit of cap to our south as ridge extends up through the Southeast. Sea breeze made a good run inland as prevailing flow remained weak with an isolated shower or two, but the main activity will remain just south of front over northern tier of forecast area. HRRR did a decent job of depicting the convection this aftn so far, weakening into this evening as heating of the day cuts off. Expect a quiet overnight for the most part as ridge gets nudged farther south and east as deepening mid to upper trough makes its way east toward the Carolinas. A few minor perturbations will ride through the deepening W to SW flow over the Central Carolinas and should see some convection flare as front moves back north and west of the area as a warm front. This activity should remain to the north of local forecast area for the most part. Will keep minimal pops over Pender and Bladen counties late tonight, but should see a lull through the morning before convection begins to flare along sea breeze and then I-95 corridor Sat aftn as upper level dynamics enhance activity along trough inland. Heating of the day and moistening of the boundary layer on Saturday will add to the upper level dynamics, increasing the potential for shwrs/tstms Sat aftn into the evening. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 300 PM Friday...An upper level trough begins to cut-off over the Great Lakes around 00 UTC Sunday and drops over the Ohio River Valley by Sunday night. At the surface a cold front will shift across the Carolinas and stall just to the west of i-95. This will align the best moisture and instabilities over the eastern 2/3 of the forecast area. The highest precipitable waters of 2.0" will be along the coast and BL CAPE values will run from 1500 J/kg in the extreme west of our area to 2500 J/kg at the coast. So can expect good chances of thunderstorms Sunday with heavy rains possible. Lows will be in the lower to middle 70s west of Interstate 95 and middle 70s elsewhere except a few upper 70s along the immediate beaches. Highs will be in the upper 80s to around 90 with the increased cloud and storm coverage. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM Friday...`Cooler and Wetter, Followed by Drier and Hotter` may be one way to describe anticipated long range weather. ECMWF/GFS solutions showing good H5 adhesion in dropping an upper low SE across West Virginia Monday, then northward into New England Wednesday. Sensible weather impacts include, below normal Max-T numbers Mon/Tue due to high rain chances, and above normal overnight lows due to cloudiness. The `snap-back` upper ridge in wake of the departing upper system will bring hotter and drier air Thu/Fri, and notably lower daytime POP values. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... As of 00Z...Expect mainly VFR conditions through most of the valid TAF period, now that convection over the area has mostly died. There is an outside chance for patchy MVFR fog tonight but the probability of it occurring does not warrant inclusion in the terminals attm. Convection well to the west should not affect the area overnight. Aft 18Z, have included VCTS northern and western terminals to account for expected isolated to scattered convection. Extended Outlook...MVFR/IFR from isolated to scattered SHRA and TSRA, especially each afternoon and evening across all sites through Saturday. Increasing chances for showers and tstms on Sunday. Isolated convection Monday through Wednesday. && .MARINE... NEAR TERM /THROUGH SATURDAY/... As of 900 PM Friday...Winds have dropped back to about 10 KT over the waters and should remain there overnight. Winds will increase heading through Saturday as gradient tightens between a trough inland and Atlantic high pressure offshore. Seas will run 2 ft or less tonight and will increase to 3 to 4 ft by late Saturday. SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 PM Friday...A cold front will be moving toward the coast on Saturday evening but will stall around 100 miles inland. This in turn will see the southwest winds blowing around 15 knots through the entire period. With the duration and fetch of the wind, the seas will increase from 2 to 3 feet Saturday night to 3 to 4 feet on Sunday and a few 5 footer are expected at 20 miles off the coast mainly north of Little River Inlet after midnight Sunday. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 300 PM Friday...Anchoring of Bermuda High pressure this period maintains a SW wind, generally between 10-20 kt, a few higher gusts inshore during the afternoon heating inland. Just about all of the wave energy will be tied to wind-seas, and short-period waves, with very little long period wave energy seen. TSTMS and showers to be numerous MON/TUE, with a drying trend beginning WED. && .TIDES/COASTAL FLOODING... As of 800 PM Friday...The latest forecast has the tide gage located on the lower Cape Fear River at downtown Wilmington peaking around 6 ft MLLW about 947 pm EDT, which is this evening`s high tide. Shallow flooding commences at the 5.5 ft MLLW height threshold and occurs within a window surrounding high tide. For tonight`s potential, flooding will be possible between 8 pm EDT to midnight EDT. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Beach Hazards Statement from 6 AM EDT Saturday through Saturday evening for SCZ054-056. NC...Beach Hazards Statement from 6 AM EDT Saturday through Saturday evening for NCZ106-108-110. Coastal Flood Advisory until midnight EDT tonight for NCZ107. && $$ SYNOPSIS... NEAR TERM...31 SHORT TERM...RH LONG TERM...MJC AVIATION...31
Area Forecast Discussion
National Weather Service Phoenix AZ
855 PM MST Fri Aug 10 2018 .UPDATE... Updated DISCUSSION and AVIATION sections. && .SYNOPSIS... Favorable northeasterly flow aloft along with sufficient moisture will keep an active monsoon pattern in place through the weekend. Thunderstorms that develop will have the potential to approach severe limits, with strong winds, frequent lightning, areas of blowing dust, and locally heavy rain possible. The increase in moisture will also help keep temperatures below normal through the weekend. && .DISCUSSION... So far, this evening has been much quieter than last evening - despite strong northeasterly steering flow. Activity over the higher terrain (especially Rim and southern Yavapai County) has been more isolated. The 00Z PSR sounding shows a cap at about 760 mb with considerable associated CIN. The MLCAPE values not overly impressive either at around 450 J/kg. However, Gila County has just recently become quite a bit more active - likely in associated with a disturbance aloft. With strong storms moving toward the lower terrain of south-central AZ (including metro Phoenix) and good temp/dew point spreads, there is good potential for very strong winds to affect a large area. The key question is whether or not the outflow will be strong enough to overcome the CIN. In recent days, we`ve seen high CIN values be overcome so have not given up on storms moving across the valley floors. As for model data, the HRRR has been trending down on it`s activity the 02Z has now dropped the late night activity for Gila and Maricopa Counties. However, it has been handling current activity poorly. For instance, it hasn`t been depicting the northern Yavapai storms nor the Gila County storms (as of this writing). Meanwhile, the NAM Nest which has handled early evening activity better, brings strong storms right through Gila, Maricopa, and Pinal Counties. With fast storm movement, we may not see much in the way of true flash flooding - but could still see nuisance flooding. Will not cancel the Flash Flood Watch yet, but may need to pare back some areas. && .PREVIOUS DISCUSSION...Issued 213 pm.... Latest water vapor imagery depicts an elongated trough in TX extending back westward into Arizona. Further north, an anticyclone predominates across the Great Basin. Between these two systems, a much stronger than normal northeasterly steering flow persists across the Desert Southwest. Still expecting tonight to be relatively active across the forecast area, with the aforementioned northeasterly flow and well-below normal temperatures in the mid-levels. Latest ACARS soundings out of KPHX still show that temperatures have barely warmed from this morning and are as cold as -8C to -9C at 500 mb. Looking upstream, latest water vapor imagery shows some reflection of increased drying associated with vorticity near the Four Corners. This will likely provide extra ascent to cells forming along the Mogollon Rim later this afternoon and this evening. Forecast is weighted heavily towards the HREF, which indicates that activity will be most concentrated across south-central Arizona. NAM Nest initialized last night`s activity well and also suggests activity will move through the Phoenix area tonight. Successive runs of the HRRR also continue to point to a complex of storms dropping rapidly out of the higher terrain and into the Phoenix area perhaps as late as midnight. Given its past success this summer, this seems reasonable and above average PoPs were retained for tonight. PWATS are not exceptional, though still sufficient to produce storms with heavy rain. The most vulnerable areas for flash flooding are across eastern Maricopa County, where the highest rain totals have been observed the past few days. However, there is a discernible threat further south and west, given the stronger than normal steering flow and a Flash Flood Watch has been issued as far west as La Paz County. && .AVIATION... South-Central Arizona including KPHX, KIWA, and KSDL... Storms over Gila County will push outflow into metro Phoenix. The TAF site most likely to see a strong wind shift (and reduced visibilities from this outflow) is KIWA. Expect at least isolated storms to move across the Valley floor behind the outflows (generally from east to west). Have held off for now on TSRA in the TAFs but that could very well change. Any storms that form will be able to reinforce the pre-existing outflow winds in terms of strength/speed but will make for more erratic directions. They would also produce brief very heavy rain. Southeast California/Southwest Arizona including KIPL and KBLH: Storm activity near and west of the Lower Colorado River Valley looks unlikely. However, storms from south-central Arizona may reach portions of La Paz and Yuma County (after midnight). More likely will be outflow from distant storms. At this time, the TAFs do not reflect outflow related wind shifts but that is subject to change. Aviation Discussion not updated for amended TAFs. && .FIRE WEATHER... Monday through Friday: Monsoon moisture and precipitation chances are forecast to decrease early next week. During this period, storms will mainly be relegated to the higher terrain with only a remote chance in the lower elevations. Consequently, temperatures will be near to slightly above average while afternoon humidity minimums drop between 15-20 percent for the lower elevations. Apart from this, winds will be light with the typical afternoon breezes. A better chance of storms may return late next week. && .SPOTTER INFORMATION STATEMENT... Spotter reports may be needed later this week. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Flash Flood Watch until 2 AM MST Saturday for AZZ531-533-534- 536>544-546-548>551. Flash Flood Watch until 11 PM MST this evening for AZZ545-547- 552-556>558-560>563. CA...None. && $$ DISCUSSION...AJ PREVIOUS DISCUSSION...Hirsch/Hernandez AVIATION...AJ FIRE WEATHER...Hirsch/Wilson