Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/17/17

See below for an aviation forecast discussion for the 00Z TAFs.

&& .SHORT TERM...(This Evening through Thursday Afternoon) Issued at 341 PM CDT Wed Aug 16 2017 An area of rain associated with an upper level shortwave trough overhead and a surface low pushing up from the south will continue to affect mainly the southern and eastern portions of the CWA late this afternoon, then just the eastern CWA this evening into the overnight hours. Areas along and east of Interstate 29 may see rainfall amounts in excess of half an inch into the evening hours. This system will push east of the area on Thursday, with high pressure dropping in and bringing a return to dry and warmer conditions, along with mostly sunny skies. Low temperatures tonight will range from the mid 50s to the lower 60s. High temperatures on Thursday will range from the upper 70s to the mid 80s. .LONG TERM...(Thursday Evening through Wednesday) Issued at 341 PM CDT Wed Aug 16 2017 Short wave trough and surface cool front still on track to affect the region Thursday night into Friday as they slide in from the northwest. Models continue to agree well and have been consistent with this system bringing scattered showers and thunderstorms. Otherwise, surface high pressure ridging will build in behind Friday afternoon and night, and then to the southeast on Saturday. The models continue to show an upper level low pressure area moving across central Canada forcing a surface cold front slowly southeast and across much of the Dakotas Saturday through Sunday. The upper level flow will be westerly aloft allowing for this boundary to slow down or stall out. At this time, this boundary does not look to be active with showers/storms from Friday night through Sunday until a short wave trough moves in from the west. Thus, have it dry from Friday night through Sunday with chances of showers/storms coming back for Sunday night. As this boundary slows down/stalls chances of showers/storms remain across the southern CWA Monday. The upper level flow then becomes northwest from Monday night into Tuesday with Canadian surface high pressure pushing in from the northwest bringing dry and cooler conditions for Tuesday and Wednesday. Temperatures will be warming up from Friday into Saturday as winds become south behind the exiting high pressure area. Above normal temperatures in the mid 80s to the lower 90s are expected on Saturday in advance of the surface front. Would not be surprised with some mid 90s out west on Saturday afternoon. Cooler air will bring temperatures back to near to slightly below normal for Sunday through Wednesday dominated by surface high pressure. && .AVIATION...(For the 00Z TAFS through 00Z Thursday Evening) Issued at 640 PM CDT Wed Aug 16 2017 Expect rain to persist across northeast South Dakota into west central MN for several more hours on north-northwest winds. Rain should be tapering off at KABR by 03Z this evening, and at KATY by 07Z tonight. But, sub-VFR conditions are expected to persist at KABR/KATY tonight into Thursday morning before conditions begin to improve at those two terminals. KPIR/KMBG should remain VFR over the next 24 hours. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Dorn SHORT TERM...Parkin LONG TERM...Mohr AVIATION...Dorn
Area Forecast Discussion
National Weather Service Duluth MN
910 PM CDT Wed Aug 16 2017 .UPDATE... Issued at 910 PM CDT Wed Aug 16 2017 Adjusted pops to account for the current radar trends. Still expecting a slight chance of thunder later tonight. Not anticipating any flooding as soil moisture is fairly dry yet according to the CREST and SAC-SMA soil moisture. Made some other minor tweaks. UPDATE Issued at 636 PM CDT Wed Aug 16 2017 Have bumped up pops and brought them in a bit earlier than previous forecast across northwest Wisconsin to better time in the activity moving in from southeast Minnesota. Rest of the forecast is on track. && .SHORT TERM...(This evening through Thursday) Issued at 310 PM CDT Wed Aug 16 2017 The focus remains on the widespread moderate to heavy rainfall forecast across the Northland through Thursday in association with an area low pressure lifting through the Upper Midwest. The latest trend in the models has been to shift the axis of heaviest rain a bit farther east, resulting less rainfall forecast across northwest Wisconsin and more across parts of northeast Minnesota. The RAP seems to have a good handle on the situation, especially in its earlier depiction of a dry slot moving for the middle of today. Used extra weighting towards the RAP on timing and rainfall through tonight. A deepening area of low pressure over northwest Iowa, as of during the middle of this afternoon, is expected to lift across southern Minnesota through tonight and into central/northern Wisconsin Thursday. It will become somewhat vertically stacked tonight as it deepens. This low will bring a period of deep moisture and moderate large-scale forcing for ascent across the Northland. Precipitable water values will increase to 1.5 to 1.75 inches. The forcing will producing widespread moderate to heavy rain across the Northland, primarily tonight through early Thursday afternoon, as the low lifts across the region. The heaviest rains, about 1.5" to perhaps as much as 2.5", are now expected to fall in a wide band from central Minnesota through northeast Minnesota in association with the deformation zone on the northern and western periphery of this system. There could be some thunder here and there through Thursday, mainly across the southern forecast area due to the potential for elevated- based instability and forcing from embedded shortwaves or from the main upper-level low. The instability will likely be fairly weak, so the storms should only result in occasional lighting, heavier rainfall rates, and breezy winds. The rain will gradually pull out of the Northland Thursday afternoon, with drier air filtering into the western forecast area as the low departs. Considering the rain and high moisture, even once the deeper cloud cover exits the western forecast area in the afternoon, broken/overcast cumulus cloud cover should quickly develop, meaning not much sunshine until maybe close to sunset. Expect a cooler and humid day, with highs from the low 60s in the Arrowhead to the middle and upper 60s elsewhere. .LONG TERM...(Thursday night through Wednesday) Issued at 310 PM CDT Wed Aug 16 2017 An upper ridge will be over the Pacific northwest into Alberta/British Columbia Thursday night with a trough from Hudson Bay through the central CONUS. The flow will become zonal over the region through the weekend into early next week then another trough will move over the region early next week. The strong low pressure system will be moving away from the Northland Thursday night with lingering showers ending overnight for most areas. Additional rainfall will be light Thursday night. Brief weak ridging will develop overnight behind the departing low but another shortwave in northwest flow will be moving in during the day Friday. There will be a chance for showers and a few thunderstorms roughly from near Walker to Siren and points west and south during the afternoon and evening. Dry conditions will occur Saturday as the low level flow becomes south to southwest. Highs will range from the upper seventies to lower eighties. Another shortwave and front will move through the Northland Saturday night into Sunday bringing another chance for showers/storms to parts of the area. Highs Sunday will again be in the upper seventies to lower eighties. A stronger shortwave will bring a better chance for showers/storms to the region later Sunday night into Monday night. A dry period is then expected Tuesday into Wednesday. High temperatures Monday through Wednesday will be in the seventies. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 636 PM CDT Wed Aug 16 2017 Mainly MVFR/IFR across the terminals through the forecast with rain and some BR. The exception is HYR starting the forecast with VFR. Expect the MVFR ceilings to reach HYR by 06Z along with a few thunderstorms nearby. Have a VCTS mention due to timing issues with storms. Rain will end gradually from west to east as the system responsible for this activity departs. Some improvement to VFR is also expected toward the end of the forecast. && .PRELIMINARY POINT TEMPS/POPS... DLH 58 63 55 75 / 90 90 20 10 INL 58 64 51 77 / 100 100 10 10 BRD 60 69 55 77 / 100 100 0 30 HYR 63 68 55 74 / 90 60 40 10 ASX 61 70 57 76 / 70 60 50 10 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...Small Craft Advisory until 4 PM CDT Thursday for LSZ141>147. Small Craft Advisory until 4 PM CDT Thursday for LSZ140. && $$ UPDATE...GSF SHORT TERM...Grochocinski LONG TERM...Melde AVIATION...GSF
Area Forecast Discussion
National Weather Service Des Moines IA
706 PM CDT Wed Aug 16 2017 ...Updated for Near Term Trends and 00z Aviation Discussion... .UPDATE... Issued at 706 PM CDT Wed Aug 16 2017 Biggest changes were to the PoPs, wind, and wind gusts for tonight through tomorrow. Subjective analysis at 6:30pm shows low pressure is over southwestern Minnesota near Worthington with a cold front extending southward nearing Estherville, Fort Dodge, Des Moines, and Osceola. 23z objective SPC mesoanalysis shows MLCAPE ahead of the front is between 1000 and 1500 J/kg with effective bulk shear generally 25 to 35 knots. Overall, the best shear has stayed ahead of the best instability and forcing. GOES-16 low level water vapor imagery shows plenty of dry air over the cold front, though moisture is streaming northward into south central Iowa from convection that is crossing from Kansas into Missouri. Looking at current radar and satellite trends, HRRR and ESRL HRRR seem to have the best handling of the situation with dry slot pushing into the western part of the state. Post-editing from the HRRRs accounted for showers that have been trying to develop along the front and may move into northern Iowa this evening. PoPs were greatly lowered over the southwest forecast area through the metro this evening. Still have some PoPs in the east and south, especially southeast, where showers and storms may come out of Missouri and clip the southeast forecast area. Sustained winds and corresponding wind gusts were increased slightly overnight as low pressure deepens a bit as it moves eastward over Minnesota. Winds were also increased moreso tomorrow as low pressure moves into the Great Lakes and with cold advection prevailing for a good part of the day. Wind gusts over will average between 20 and 30 mph with the highest gusts over northern Iowa. && .SHORT TERM.../Tonight through Thursday/ Issued at 243 PM CDT Wed Aug 16 2017 Surface low pressure was located across northwest Iowa at 19Z with a cold front extending southward into southwest Iowa. Convection thus far today has been relatively light. Although instability exists, lack of coherent forcing has limited the convection. Expect the cold front to help provide some coherent forcing for convection this evening and tonight as it slides eastward across Iowa. CAMs keep most of the convection to the south in Missouri and southward, however cannot rule out an isolated severe storm across southern Iowa. Damaging wind and large hail would be the primary threats. Wrap-around moisture and instability behind the system on Thursday will keep chances of showers and possibly thunderstorms mainly across the northeastern CWA. .LONG TERM.../Thursday night through Wednesday/ Issued at 243 PM CDT Wed Aug 16 2017 Thursday Night through Sunday Night: Confidence: Medium Main concern will be next upstream short-wave/frontal boundary that is expected to arrive Friday into Friday night. Quiet weather will continue into the night with lows in the 50s to lower 60s. Bulk shear will be increasing through the morning/afternoon potentially a few storms may be strong to severe and we continue outlooked for marginal. Highs will be similar to the past few days with upper 70s to mid 80s in the south. There are some minor differences between the GFS/Euro as for timing and best forcing. The Euro is a bit farther north with the better forcing Friday into Friday evening. After a quick exit warm air advection will return for late Saturday into Sunday as another system begins to move into the Great Plains. Both the GFS/Euro are hinting at increased warm air advection into the northwest Sunday...which may lead to late day thunder/storms over the far northwest. As a warm front lifts northeast into Minnesota Sunday night convection will be favored over the north/west during the nighttime hours. Monday through Wednesday Confidence: Low to Medium Though the pattern is active through the period...timing differences based on model choice and consensus continue to lead to low confidence. Models diverging Monday with the GFS farther south with the main forcing compared to the European model. The GFS develops an MCS over eastern Nebraska by 06z Monday and slowly decays the activity through 18z...taking the complex over western Iowa/northwest Missouri through 18z. Previous model packages were in better agreement with timing/placement of features. Given the interest in the forecast for Monday...too early to have a definitive answer regarding cloud cover/rain chances given the current information. H850 temperatures continue to be warm both Sunday into Monday and if sunshine is present...should allow highs to reach well into the 80s both days...especially across the south. Models continue to focus more of the thunderstorms through the overnight hours Monday night into Tuesday with some lingering storms in the south later in the afternoon. There remain some timing difference later Tuesday night into Wednesday. && .AVIATION.../For the 00Z TAFS through 00Z Thursday evening/ Issued at 706 PM CDT Wed Aug 16 2017 A cold front will continue to move through central Iowa this evening and overnight bringing a shift of winds from the south to more of a westerly direction. Showers have been widely scattered and have only mentioned VCSH at KMCW and KALO early this evening. Otherwise, fairly high confidence of wrap around clouds with MVFR ceiling restrictions over the northern terminals arriving tonight. Highest confidence of these restrictions is at KMCW where there is also a period of IFR restrictions mentioned. Slightly lower confidence at KFOD and KALO preceded mention of IFR ceilings at this time. For the southern terminals, showers and storms may come close to KOTM, but did not include due to lower confidence. Overall for KDSM and KOTM, have VFR conditions prevailing through the TAF period. Will monitor trends and send amendments if needed. Otherwise for the terminals, winds will become gusty from the northwest through the daylight hours Thursday. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Ansorge SHORT TERM...Zogg LONG TERM...REV AVIATION...Ansorge
Area Forecast Discussion
National Weather Service Quad Cities IA IL
710 PM CDT Wed Aug 16 2017 ...AVIATION UPDATE... .SYNOPSIS... Issued at 330 PM CDT Wed Aug 16 2017 18Z surface data has a warm front just north of I-80 with low pressure in western Iowa. Across Missouri a squall line was moving toward the east. Dew points from the Great Lakes into the upper Midwest were in the 60s. Near and south of the warm front, dew points were in the 70s. && .SHORT TERM...(This Evening through Thursday) ISSUED AT 330 PM CDT Wed Aug 16 2017 Through late afternoon convection will continue to develop and increase in areal coverage north of highway 30 as forcing associated with the warm front moves into Wisconsin. South of highway 30 isolated showers and storms are expected. The question is what happens from roughly 6 PM to midnight. Satellite trends show little in the way of cloud development from central Iowa back into northwest Missouri. Satellite does show a nice push of dry air aloft moving into western Iowa from eastern Kansas. However, the better instability and forcing will be from Kansas into Missouri. What may happen is that another organized line of strong convection will move east across Missouri that slowly develops northeast into eastern Iowa. Recent trends with the RAP suggests this scenario. If this scenario occurs, the overall severe risk would be low as storms across Missouri take advantage of the stronger forcing and greater instability. After midnight, the cold front will sweep through the area. Rain behind the front decrease in coverage with time through sunrise Thursday. On Thursday, wrap around clouds will be over much of the area during the morning and slowly exit the area during the afternoon. Any lingering rain will become more spotty during the morning hours with only isolated showers expected over the northeast third of the area during the afternoon. Temperatures Thursday will be highly dependent upon cloud cover. Areas north of highway 30 may spend much of the day in the 60s before popping into the mid 70s late in the afternoon with clearing skies. ..08.. .LONG TERM...(Thursday Night through next Wednesday) ISSUED AT 330 PM CDT Wed Aug 16 2017 Thursday night and Friday...Wrap around stratocu to clear off to the east Thu evening, with incoming sfc ridge lobe and seasonably cool night in store. Lows in the low 60s and more coverage in the 50s. As for Friday, most of the 12z model runs have continued to be more progressive with vigorous digging short wave in northwest upper flow, with the potential for sctrd showers and a few storms spilling into the western/northwestern CWA by late Fri afternoon. The prime lift window with this passing upper wave now appears will be from 00z-06z Sat, wiht the chance most any precip this feature kicks up will be east out of the local area by early Sat morning. Thus sctrd showers and some storms moving acrs portions of the area Friday evening and into the overnight. Interaction with lift from this system and a more pronounced moisture convergence/THTA-E feed will look to occur on this systems southwestern flank to generate more significant storm clusters or even a MCS type feature, from the MO RVR Valley southward into KS and western/central MO Fri evening. Saturday and Sunday...In the wake of the Fri night system, latest suite of medium range model runs generally suggest a fair weather and warming period for most of the upcoming weekend. High temps by Sunday with adequate return flow, may warm well up in the 80s, with a few guidance solutions even suggesting some 90 degree readings possible along and south of I80. Now looking at the Sunday night MCS generation area potentail, the 12z ECMWF has the southerly warm moist conveyor converging upon a boundary acrs the Dakotas, with resultant storm cluster or MCS propagating eastward acrs MN into early Mon morning. The 12z GFS maintains a further south mode with initiation acrs Neb and the MO RVR Valley, but keeps it festering out to the west through 12z Monday. Just low chance POPs warranted for now in the western CWA for late Sunday night, with a bias that maybe the further south MCS spawning grounds of the GFS may be more in line. Monday through next Wednesday...Latest GFS and ECMWF runs suggest the eclipse day Monday may be hot and humid in the upper 80s to lower 90s acrs much of the area. Latest MCS generation and propagation paths out of Sunday night may not be as impactful acrs the local area with respect to debris clouds...but still way too early to determine those kind of details for that far out at this point. Could see where either an MCV or outflow boundary from earlier upstream convective complex activity becomes the focus for renewed thunderstorm development in or close to the local area later Monday or Monday evening. Long range progs then suggest another digging upper trof acrs the northern plains and upper MS RVR Valley to interact with a warm moist feed up off the Gulf, and possible southwesterly tentacle of monsoonal influence, to fuel strong thunderstorms complexes acrs portions of the upper Midwest(including the local area), Monday night into Tue. Then, for a secondary day in a row, decent longer range agreement of the various medium range models in shunting the active storm track to the south of the region to the southern plains and OH RVR Valley by mid next week. Canadian high pressure will then look to take grip of the region with cooler, drier, and less humid weather for the mid to late next week period. ..12.. && .AVIATION...(For the 00Z TAFS through 00Z Thursday Evening) ISSUED AT 705 PM CDT Wed Aug 16 2017 A cool front will pass this evening with a chance of showers and thunderstorms which may briefly produce MVFR conditions. Winds will shift from the south to the west by midnight with skies clearing over the region until near sunrise. After 17/10Z...low clouds will overspread locations along and north of I-80 corridor including the MLI terminal by 10/14Z with MVFR to higher end IFR conditions lasting until mid to late PM when skies will clear. The BRL terminal will remain fair. Winds will be westerly at 10 to 20 mph through the day on Thursday. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...08 SHORT TERM...08 LONG TERM...12 AVIATION...Nichols
Area Forecast Discussion
National Weather Service Grand Rapids MI
1022 PM EDT Wed Aug 16 2017 LATEST UPDATE... Update .SYNOPSIS... Issued at 334 PM EDT Wed Aug 16 2017 Showers and storms will arrive overnight and continue into Thursday. Some storms could be strong to severe Thursday afternoon, perhaps lingering into Thursday evening. After a muggy highs in the upper 70s to lower 80s on Thursday, we will cool down to the low and mid 70s Friday and become less humid. A few showers may continue into Friday morning, north of I-96. The weekend looks mainly dry, then another chance of showers and storms should move back in Monday night through Tuesday night. Daily highs for the weekend into next week should remain in the upper 70s to mid 80s. && .UPDATE... Issued at 1022 PM EDT Wed Aug 16 2017 Based on the radar trends, and trends in the HRRR and ESRL HRRR I have increased the pop to near 100% over the western CWA after midnight. The instability is not all that great (most unstable cape near 600 j/kg, but what is really happening is the deep moisture is coming into our area. Precipitable water values rise from under 1.5" at 8 pm to over 2.0", which is within a tenth of an inches of the all time record for the 17th of August. The 1000/850 moisture transport increases dramatically between now and midnight over our western CWA and more so our NW CWA. Both the HRRR and RAP models show two low level jets tonight, one around midnight that is mostly focused on NW lower Michigan then a second one, currently helping the convection in MO, heads into our Southern CWA toward Sunrise. So I see two periods of showers / isolated thunderstorms, one around midnight then next around sunrise. Given the amounts of water in the air, we will likely get some brief heavy down pours, I can see isolated locations getting well over an inch tonight then again around sunrise with the next band of convection. Most areas through will likely see less than a quarter inch between now and noon. As for thunderstorms tomorrow afternoon, the primary low level jet is aimed near SE MI. We do get another one that is aimed toward NW Lower Michigan in the evening, that needs to be watched for late day convection with the cold front. && .SHORT TERM...(This evening through Friday night) Issued at 255 PM EDT Wed Aug 16 2017 Showers and storms will move in overnight and continue Thursday. Severe storms are possible Thursday afternoon/early evening, depending on the timing of several ingredients. A quiet evening will become increasingly wet overnight as the upper ridging that was overhead moves east, and a strong upper wave moves into the Western Great Lakes by daybreak. A warm advection surge of moisture and lift will be over the heart of the CWA by 12Z. Showers and a few storms will be on the increase from 06Z, and covering much of the CWA by 12Z. No severe weather is expected with this wave of pcpn. However severe storms will be possible into Thursday. But it will depend on all factors coming together. With the morning showers and storms exiting we will need to destabilize again into the afternoon. The models do indicate some clearing behind the morning wave, allowing for instability to build into the afternoon. The most likely region where this occurs should be for areas east of U.S. 131. Bulk shear values are most favorable into the afternoon for organized storms with hail, around 35 knots, then it tails off to around 25 knots by early evening. However a large portion of this shear is in the lowest 1km into the evening. A warm front will be crossing the CWA, passably supplying more shear locally, and with low LCLs we may see the risk of an isolated tornado. Damaging winds will also be possible with bowing line segments. Precipitable water values spike to over two inches by Thursday morning. So we will also have to watch the heavy rain potential, with very heavy localized rains likely with the WAA rains. Additional heavy rains will be possible into the afternoon, but this will be very more localized with the diurnal convection. A breezy Friday with some warp around showers possible in the morning. Temps will be about 5 degrees cooler, along with falling dew points. More isolated showers and storms possible late Friday night with another upper wave coming through. .LONG TERM...(Saturday through Wednesday) Issued at 255 PM EDT Wed Aug 16 2017 Two main periods of rain look possible in the long term, one on Saturday, and then another centered around the Tuesday timeframe. We are looking for temperatures to warm up quite a bit by Monday of next week, before a pronounced cool down comes in for mid-week next week. A decent short wave will dive in quickly on Saturday, in the wake of the upper system supporting the system for tomorrow into Friday. There is decent agreement that this looks to affect mainly the srn portion of the CWFA. We would not be surprised if this system digs a little further south, and moves south of the area. We will roll with chcs of showers/storms for Sat for the time being. Dry and increasingly warmer weather is expected for Sunday and Monday. We will see a flat upper ridge migrate over the area. Even though the ridge will not be very strong, we will see a solid SW flow bring in very warm air aloft from the Plains states. The atmosphere will likely be capped through Monday. This is favorable for eclipse viewing in the area Mon, aside from some small cumulus development or high clouds that might approach the area. The threat for rain will increase beginning Mon night and will likely max out on Tue. The flat ridge will slip east, and we will see an amplifying trough taking shape to our west. The stronger nature of the wave combined with some Gulf moisture advecting in looks to bring a good shot of showers/storms to the area. This should move out by Wed, leaving a much cooler and drier air mass in its wake. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 751 PM EDT Wed Aug 16 2017 There is some concern for convection to move through the TAF sites overnight and during the day Thursday. As is typical for here, seems most of the convection will struggle to reach our TAF sites. The large area of convection ahead of the warm front lifts north over Wisconsin this evening and we will mostly see virga from mid clouds at least till around 06z. There is some chance a few showers or Thunderstorms will come through the TAF sites at two times. The first window (based on the HRRR and ESLR HRRR) is between 05z and 09z (west to east) and from 09z to 14z (west to east). The trend through is for the more widespread convection to stay north of MKG so I only put VCTS at any of the TAF sites. As the warm front comes through around sunrise I am expecting a period of MVFR CIG but not much rainfall. As the cold front pushes through the area Thursday afternoon, again it is not out of the question there would be thunderstorms after all there is instability and low level convergence ahead of the cold front. However most of the models show a lot of mid-level subsidence and the Low Level jet on the NAM is aimed at TVC in the 21z to 00z time frame. More than likely any convection would be toward the Detroit area in the evening. However we will be watching just in case the storms do become better organized for our TAF sites. && .MARINE... Issued at 255 PM EDT Wed Aug 16 2017 Will issue a small craft advisory for Thursday afternoon north of Holland and extend it through Friday. Southerly winds will pick up Thursday, then become westerly by late Thursday night. Most likely we will need to add the areas south of Holland into Thursday night as this wind shift occurs. && .HYDROLOGY... Issued at 330 PM EDT Wed Aug 16 2017 Multiple rounds of thunderstorms are possible Thursday. This may lead to localized heavy rainfall where storms more frequently occur. Early to mid morning showers and storms are expected along a warm front and afternoon/evening showers and storms are possible especially east of US 131. PWAT values will be quite high, approaching 2.0 inches, along with surface dew points above 70. There is some potential for a few training thunderstorms with MBE velocities occasionally dropping below 10 kts. However, this does not look like a classic flood setup outside of localized ponding of roads. We will continue to monitor trends. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement from Thursday afternoon through Friday evening for MIZ037-043-050-056. LM...Small Craft Advisory from noon Thursday to 9 PM EDT Friday for LMZ846>849. && $$ UPDATE...WDM SYNOPSIS...JK SHORT TERM...JK LONG TERM...NJJ AVIATION...WDM HYDROLOGY...Hoving MARINE...JK
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
143 PM PDT Wed Aug 16 2017 .SYNOPSIS...Near to slightly above normal temperatures through the forecast with the possibility of thunderstorms over the Sierra Nevada each afternoon and evening through next week. && .DISCUSSION...An upper trough continues to impact California this afternoon...providing enough instability over the Sierra Nevada to generate showers. Showers were beginning to develop over the Sierra Crest this afternoon mainly in Fresno County...but this activity is expected to expand in coverage into the evening hours. The high res ARW...NMM...and the HRRR all indicate that activity will generally be concentrated from Sequoia National Park northward. Something of note...snow levels look to be right around 13,500 to 14,000 if showers form over the very high Sierra...expect snow flurries. Snow in August is not uncommon...but can catch hikers off guard. With regards to the unseasonably cool temperatures we have been experiencing this looks to be the last day of below normal temperatures. Upper level high pressure over the Eastern Pacific will begin to build slowly east over California...resulting in a warming trend across the area. Temperatures are forecast to remain near normal through the weekend with little change in the upper level pattern. Showers and thunderstorms will be possible each afternoon and evening over the Sierra Nevada through the weekend. On Sunday an upper low will form off the central California coast bringing a subtle cooling trend. In addition to cooling...there will likely be an increase in shower and thunderstorm coverage over the Sierra Nevada...possibly as far south as the Kern mountains and even the desert. We will continue to watch this closely as there are still subtle differences with the location and movement of the upper low. We heard there is a big event on Monday...the eclipse! As of now... it looks like much of the area will see mostly sunny viewing looks good at the moment. We will continue to monitor the cloud cover forecast closely and update accordingly. && .AVIATION... VFR conditions will prevail across the central CA interior during the next 24 hours. && .AIR QUALITY ISSUES... None. && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is medium. Certainty levels include low...medium...and high. Please visit for additional information an/or to provide feedback. && .HNX Watches/Warnings/Advisories... NONE. && $$ public...Riley avn/fw...Meadows synopsis...Riley
Area Forecast Discussion
National Weather Service Jackson MS
932 PM CDT Wed Aug 16 2017 .UPDATE... Updated for evening discussion. && .DISCUSSION... The POPs have been shaped up for this evening update, mainly focused a few showers to the east--near I-20 AL/MS border. Within an hour everyone should be drying out across ARKLAMS region. The latest run of the HRRR and the CONSShort is throwing in some patchy fog down near Hwy 84 and Hwy 98. With clearing skies down near the coast as dry air starts to seep in, low level moisture from afternoon rain showers, & light winds, I expect a few isolated areas to get a bit foggy. /12/ Prior discussion below: Quick update for early evening...convection has been progressive and has evolved in a manner where the main storm activity is across east-central MS here to start the Tonight period. The remainder of the forecast area is seeing lingering light rain due to convective debris fallout from prev storms. The PoP forecast was updated to show these trends here for early evening then have values lower for the remainder of the night. Thunder wording was drastically lower as well and only focused for a short period across east-central. Temps were also lower to match the rain cooled trends. Overnight lows were not changed. Graphics were removed as late afternoon threats for heat/flooding have diminished. /CME/ Prev discussion Thursday: As that upper & surface ridge build east Thursday over the Florida Panhandle & north-eastern Gulf of Mexico. As an upper jet strengthens over the central Plains & ejects into the mid-northern Mississippi Valley & into the Great Lakes by Thursday afternoon, a surface low & attendant cold front will be diving through the central Plains & towards the area. In addition as the upper low over the western Gulf of Mexico today propagates eastward, flow aloft will be be slightly different with less diffluent flow. Moisture will lessen, with closer to one and three quarters to two inch PWs, & 850mb Theta E only near 340K. Low level moisture will continue to linger & not mix too much. With thermal profiles gradually warming, especially with any compressional heating, expect highs to be slightly warmer potentially around the 92-94 degree range. With dewpoints hovering in the mid-upper 70s, we should be able to maintain some high heat indices near & above 105 degrees across most areas. Heat stress can be expected tomorrow, especially along & west of the I-55 corridor. Updated the HWO/graphics to include an elevated risk for heat while wrapping the limited risk down into the Golden Triangle as well. Issued a heat advisory from 9AM through 7PM Thursday. Due to the changing jet dynamics & less moisture, PoPs will be lower tomorrow, but some 2 inch PWs pooling in the Delta will help more convection to be sparked in the ArkLaMiss Delta & Highway 82 corridor. Global models & CAM guidance (including ARW) indicate this idea. Surface winds & low-mid level flow will be stronger due to an increased gradient & there could be some potential for some stronger storms due to 15-20kts of 0-2 & 0-3km bulk shear. Lapse rates are meager but if we warm enough & dewpoints hold, we should be able to get some better vertical total, which the GFS shows in Delta. Did not introduce anything in the HWO/graphics for now but expect scattered convection across the Delta & Highway 82 corridor with more isolated convection elsewhere. Locally heavy downpours are possible but storms should be moving enough to preclude mentioning anything in the HWO/graphics. /DC/ Thursday night through next Wednesday: The upper low over the Great Lakes will sink a weak frontal boundary down through our region on Friday. Rain chances over the southern half of the CWA will be a bit higher than previous days due to extra lift along the boundary. However, still expect precip to be in the form of scattered afternoon showers and storms, but not widespread. This rainfall will help mitigate the heat stress just a bit. Still expect heat indices on Friday to be near 100 though. Over the weekend, the trough pushes to the east and low level ridging builds in behind it. PWs will remain high, especially in the southern half of the area, 2" and higher, thus this will be where the best rain chances over the weekend will exist. Temps will creep upwards just a bit through the weekend and heat stress will therefore increase as well. Heat indices could approach 105 degrees by Sunday again. Heights will continue to increase going into next week as the upper ridge builds back over the Southeast. Expect the typical diurnal showers and storms with average seasonal temps as well. /10/ && .AVIATION... 00Z TAF discussion: Afternoon convection is dissipating across most of the forecast area with the exception being MEI where a solid TSRA is occurring. Look for a brief period of IFR restrictions at MEI due to the storm with improving conditions by 0020z or 0030z to VFR. The remainder of the area will see the lingering -RA convective debris but remain in VFR conditions. Much of the overnight period will be VFR. However, low level flow and moist conditions will support stratus developing by 10-11z across the NW and N half. A few of the central/southern sites may see that as well, but it may start later and occur in the 12-14z window. Overall, Thursday looks less active for precip/storms with the NW sites having the better chances during the afternoon. Surface winds may also be a tad breezy across the north half as well. /CME/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 73 93 75 91 / 36 20 25 48 Meridian 73 93 75 90 / 60 18 14 49 Vicksburg 73 92 75 91 / 22 25 31 50 Hattiesburg 71 93 75 92 / 33 18 7 54 Natchez 72 91 75 90 / 23 24 16 48 Greenville 74 91 75 91 / 19 35 28 31 Greenwood 74 91 74 90 / 31 33 30 28 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...Heat Advisory from 9 AM to 7 PM CDT Thursday for MSZ018-019-025- 027-034>036-040>043-047>049-053>055-059>062. LA...Heat Advisory from 9 AM to 7 PM CDT Thursday for LAZ007>009-015- 016-023>026. AR...Heat Advisory from 9 AM to 7 PM CDT Thursday for ARZ074-075. && $$ 12
Area Forecast Discussion
National Weather Service North Platte NE
552 PM CDT Wed Aug 16 2017 .SHORT TERM...(This evening through Thursday) Issued at 321 PM CDT Wed Aug 16 2017 The blend of the HRRR models and the RAP appear to be lifting the upper level cold pool and resultant showers/isolated thunderstorms northeast too quickly by 2 or 3 hours. With the loss of heating and collapse of the boundary layer at sunset, the showers should dissipate. Weak high pressure will build in tonight produce clear skies. Drier air and lower precipitable water should stabilize the atmosphere. The NAM will develop thunderstorms off the Cheyenne divide and Black Hills Thursday afternoon. Very modest h850mb return flow develops during the afternoon and sfc winds will be very light. The northwest flow aloft near 35kt would support a multicell environment. SPC gave Wrn Nebraska a 5 percent severe weather chance and the primary hazard is strong wind gusts. blended guidance plus bias correction produced lows in the 50s and highs in the 80s. .LONG TERM...(Thursday night through Wednesday) Issued at 321 PM CDT Wed Aug 16 2017 The storm activity Thursday afternoon could grow upscale and the model consensus suggested a chance to likely POP Thursday night across Ncntl Neb. The best storm coverage and heavier rainfall might remain north across SD or slip southeast into the eastern edge of Ncntl Neb. Better return moisture and forcing develops late Saturday and both the NAM and GFS show some pretty good rain centers developing across either Swrn or Ncntl Neb. Precipitable water increases to around 1.25 inches. Chance POPs are in place, mainly Saturday night. 500mb Winds aloft become zonal and decrease to around 25 kt, perhaps lessening the chance of severe storm development. The moisture remains in place Sunday and yet another upper air disturbance is progged to set off showers and thunderstorms Sunday evening. The cloud forecast Monday continues to evaluate the potential for high cloudiness which could partially obscure the eclipse. The ECM and GFS shows subtropical moisture aloft moving across the Rockies which could produce scattered or broken high cloudiness around noon Monday. The GFS also indicates substantial low level moisture and stratus across Wrn/Ncntl Neb leftover from heavy thunderstorms across Ern Neb Sunday night. The ECM produces the thunderstorms across SD but shows the same moisture in place like the GFS. Thus, it is possible significant cloudiness will occur Monday. As a result, the sky forecast for noon Monday has been increased from 35-40 percent yesterday, to 40 to 60 percent with the forecast today. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 549 PM CDT Wed Aug 16 2017 Skies will become mostly clear tonight behind a departing system currently moving toward the western Great Lakes region. Only few250 expected at KLBF and KVTN the next 24 hours with light winds below 10 kts. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Roberg
Area Forecast Discussion
National Weather Service Nashville TN
858 PM CDT Wed Aug 16 2017 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Widely scattered showers are lingering well into the evening across Middle Tennessee. A very humid air mass is now in place, with dew points still running in the mid 70`s most locations. The 00Z sounding from OHX shows considerable instability, now that the surface ridge has shifted to our east and allowing for some return southerly flow. The HRRR does suggest the existing activity will further diminish with very little activity overnight. So will leave in isolated showers only after 06Z. Hourly grids seem to be doing well, so no forecast changes are planned at this time. && .AVIATION... 00Z TAF DISCUSSION. Scattered showers with a few thunderstorms mixed in have developed in the last couple of hours. Have prevailed some activity at KCKV/KBNA/KMQY through 01Z, though I don`t think flight categories should get any worse than MVFR. This activity should wane this later this evening as we lose the heat of the day. Winds will be relatively light this evening, calm overnight and pick up out of the southwest on Thursday with a few gusts of 15-20 kts. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......08 AVIATION........Unger
Area Forecast Discussion
National Weather Service Pueblo CO
330 PM MDT Wed Aug 16 2017 .SHORT TERM...(This evening through Thursday) Issued at 310 PM MDT Wed Aug 16 2017 Limited CAPE (ML CAPE around 500 J/kg or less) and less forcing has resulted in lower storm coverage and strength across the forecast area today. Best coverage will be across the Pikes Peak region through this evening where high res models have been consistent in spreading showers and thunderstorms eastward off the mountains. Most showers and thunderstorms will diminish during the evening with the loss of heating...however several HRRR runs have been generating another round of showers across northern portions of the southeast plains towards morning. Will maintain some isolated pops across the area to account. Otherwise...most areas will be dry and low temperatures will be on the cool side. Tomorrow will be a more active day for thunderstorms as de-amplifying upper trof moves across the area in the afternoon. Return southerly flow will advect upper 50 dew points back northward into the far southeast plains while passing trof helps mix out low level moisture again and sharpens up a dry line across the far southeast plains. Shear will be stronger...around 30-40 kts...and ingredients come together best across the far southeast corner of the state including Las Animas, Baca, Prowers, and Bent counties. One or two severe storms will be possible in this area with large hail and damaging winds the primary threats. Temperatures will return to closer to normal. -KT .LONG TERM...(Thursday night through Wednesday) Issued at 310 PM MDT Wed Aug 16 2017 Storms that will have developed along the shortwave trough axis earlier in the day Thursday will continue to propagate easterly, and once the storms move over the Colorado - Kansas border, the environment will be favorable for rotating supercells. Forecast BUFKIT sounding over Lamar, CO indicate CAPE values exceeding 2000 J/Kg and 6 km bulk shear values near 40 knots. The main threat from the storms that strengthen over eastern Colorado will be strong thunderstorm winds and large hail. The low level shear is not all that impressive, so the tornado threat is small, but still possible. SPC is in agreement with our severe weather forecast, they upgraded the day 2 outlook over extreme southeastern Colorado to a slight risk this morning, whereas the rest of the southeastern plains are under a marginal risk. The complex of thunderstorms should exit Colorado by midnight, Friday. Moving onto Friday now, the shortwave trough will have passed and lower dew point values fill the region. The GFS20 has storms developing later in the day over the Upper Arkansas River Valley and over Pikes Peak, in response to weak easterly upslope flow, whereas the NAM12 does not have thunderstorms developing, suggesting that there will be westerly flow at the surface. Some uncertainty does exist for Friday, but for the time being, a chance of thunderstorms is included in our forecast grids over the mountains, Palmer Divide, and Raton Mesa. The synoptics over the weekend and into next week include an upper- level low developing over southern California and a broad upper- level ridge building over the southern contiguous United States. The response from the previously mentioned synoptic set-up will be a monsoonal surge of moisture impacting southeastern Colorado. The common daily theme will be thunderstorms initiating over the mountains, followed by the upper-level steering flow propagating the storms over the plains. The intensity of the thunderstorms and showers will be dependent on how much moisture exists and how strong the upslope component of the wind is. According to the GFS20, the precipitable water amounts trend higher as the next week progresses. On Tuesday, models suggest that a cold front will pass, which may spark some showers over the plains in the early morning hours and will lead to moist upslope flow for Wednesday afternoon. -Skelly && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 310 PM MDT Wed Aug 16 2017 TAF sites will predominantly see VFR conditions with KCOS seeing the best chance for a stray thunderstorm in the vicinity of the TAF site. Gusty winds up to 40 kts and brief VFR cigs will be the primary impacts. Thunderstorms will diminish during the evening with light winds expected overnight. Thursday will see another round of thunderstorms develop over the mountains and move off into the adjacent plains. These should remain pretty isolated for the TAF sites with VCTS most likely for KCOS. -KT && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...KT LONG TERM...SKELLY AVIATION...KT
Area Forecast Discussion...UPDATED
National Weather Service Reno NV
831 PM PDT Wed Aug 16 2017 .UPDATE... Thunderstorms around the Tahoe Basin have ended with only few showers/sprinkles lingering near the crest and south of Hwy 50. Thunderstorms put down some decent rain on the west side of the Tahoe Basin with a couple of gauge reports including 0.75 inches around Tahoe City and 0.47 inches near Homewood. We will be updating to remove chances for showers/thunderstorms for the remainder of the night as a more stable northerly flow prevails. Hohmann && .PREVIOUS DISCUSSION... /Issued 235 PM PDT Wed Aug 16 2017/ SYNOPSIS... Mainly light winds with temperatures near or slightly above average is expected into next week. A few afternoon and evening thunderstorms will be possible near the Sierra south of Highway 50 through Thursday. Thunderstorm coverage will expand across the rest of the Sierra Friday, and into northeast California and western Nevada for the weekend into early next week. SHORT TERM... Minimal change to the forecast through Saturday. Easterly flow aloft has kept thunderstorms confined to just west of the Sierra crest so far today, with a few outlier showers over eastern Mono County and far eastern Pershing/Churchill Counties. Most deep convection (thunderstorms) should remain near or west of the crest today; however, very isolated storms cannot be ruled out (due to small-scale forcing/convergence) as far east as Highways 395 and 89 in the Sierra through around sunset. Thursday should feature isolated showers and thunderstorms once again. Flow aloft will remain northeast to east, so any storms should remain west of Highway 395 and south of Highway 50 in eastern California. However, by Friday flow aloft becomes very light so a few storms could eek a bit farther north and east by evening, possibly to near the California-Nevada border and up into Sierra and Plumas Counties. Thunderstorms will not have any large-scale help (shear or strong instability) to increase intensity on Friday so they will rely on small-scale, unpredictable forcing for their intensity. Therefore, most storms should remain modest with outflow winds to around 35 kts, brief heavy rain, and a few lightning strikes. Saturday, GFS/NAM simulations show an increase in westerly flow aloft, especially from Tahoe north, as a weak trough moves over Oregon and far northwest California. This is shown by those models to nudge convection off the crest north of Highway 50. As this was already indicated in the forecast, POP was largely left alone for Saturday. Snyder LONG TERM...Sunday through Wednesday... Sunday into Monday, low pressure is simulated to drop along the California coast. Monday through at least Tuesday, the low is expected to hang out near the central and southern CA coast, putting eastern CA and western NV in divergent flow aloft. This will favor continued rounds of isolated to scattered thunderstorms, mainly during the afternoon and evening but possibly continuing overnight depending on any minor waves moving around the upper low. At this time, storm motions appear slow so the threat for localized flash flooding (especially downhill from burn scars and in steep terrain) will increase over the weekend into early next week. As far as the partial eclipse Monday morning, there is a low to moderate chance that partly cloudy skies will prevail by Monday with residual convective clouds and general divergence aloft favoring at least some clouds. That`s all we can tell you for now so stay tuned if you plan on watching the eclipse. Temperatures should be moderated by clouds and convection early next week so near or even slightly below average temperatures are expected. Snyder AVIATION... Afternoon and evening thunderstorms are expected to remain near or west of the Sierra crest and south of Highway 50 through Thursday, with a 5-10% chance for a storm at KTVL and 15-20% at KMMH. Storms look relatively weak with outflow winds to 35 kts, a lightning strike or two, and brief light rain possible. Valley/terminal winds should remain generally less than 10 kts from a northwest to northeast direction through Thursday. Friday, isolated thunderstorms are forecast to creep farther north and may drift to near the California-Nevada border by evening. This will bring an increase (but still low) in storm chances for KTVL/KTRK, with a storm or two within sight of KCXP/KRNO possible (over Carson Range). As far as significant reductions in visibility (both horizontal and slantwise) due to wildfire smoke, the flow pattern and HRRR smoke forecasts suggest that smoke/haze will be kept along and west of the Sierra crest through Friday. Snyder && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Blacksburg VA
1146 PM EDT Wed Aug 16 2017 .SYNOPSIS... Though the majority of the forecast area is dry tonight, a weak upper-level disturbance should spark scattered showers and embedded thunderstorms mainly south and west of Interstate 77. An even more humid air mass settles in for Thursday, with a better chance for showers and thunderstorms during the afternoon. A cold front moving into the region on Friday sparks another round of showers and storms followed by clearing along with drier conditions for the weekend. && .NEAR TERM /THROUGH THURSDAY NIGHT/... As of 1140 PM EDT Wednesday... Just a minor update to bring T/Td readings in line with current trends and adjust pops according to latest trends. Since HRRR has a fairly good handle on the trend of showers moving into southwest VA at this hour, will follow its trend through the night. Activity in Smyth and Grayson counties should work its way through the CWA near the I-81 corridor over the next few hours, then gradually dissipate across the Piedmont by 10Z. New activity will likely begin developing/moving into western areas toward daybreak. Thursday looks like an active day in terms of convection as a short wave interacts with a very warm and humid air mass. A good theta-e ridge evident through the heart of the CWA Thursday afternoon. Would expect fairly widespread convection Thu. Instability and shear values are not overly impressive, but an isolated strong storm certainly could not be ruled out. Heavy rainfall will likely be the more significant problem. As of 825 PM EDT Wednesday... Isolated showers still feeding off lingering surfaced based instability early this evening across the Mountain Empire of VA through the piedmont of NC. Expect generally dry conditions overnight but some isolated activity may be wafting around mainly east of the Blue Ridge. Previous discussion... HRRR and 3-km NAM solutions display good consistency in showing ongoing shower activity trudging slowly to the east. This general area roughly bounded along and southwest of a line from Bluefield to Hillsville VA to Danbury NC. Otherwise, the rest of the forecast area stays dry through the evening. Some question if showers can linger after midnight in weak convergence field in the NC Piedmont and Southside as modeled by the GFS and the 3-km NAM. I am dubious as mid- level feature should have advanced far enough east by that point to allow for weak subsidence. After midnight, it appears that we see a considerable increase in moisture levels and clouds amid light southwesterly low to mid- level flow. GFS LAMP guidance dewpoints at MOS forecast points all trend upward overnight, so if you thought today was on the humid side, more is on the way. I`ve indicated some patchy fog in for the overnight hours in the Greenbrier and New River Valley, but less cooling due to clouds cast doubt much will develop. It`s currently doubtful we see as much fog as experienced this morning. A mild and rather humid evening with lows from the mid upper 60s to the lower to mid 70s, mildest further southeast. For Thursday/Thursday Night: Looking at quite a muggy air mass areawide. Outside of the higher elevations along the Blue Ridge, upper 60s to mid 70s dewpoints should be rather common Thursday. This moisture extends at depth as well, reflected in PWAT values progged from 1.9-2.2". Though we should likely have a good amount of cloudiness, BUFKIT soundings show an air mass that is weakly capped. So it won`t take much heating to generate enough instability to spark at least scattered showers and thunderstorms. While 500 mb height tendencies are neutral early in the day, they start to fall by the afternoon and should be enough lift, augmented by a pre- frontal or lee trough. Indicated high chance to lower Likely PoPs for showers and thunderstorms. I wouldn`t necessarily discount a couple of SPSable type storms tomorrow, but the deeper layer shear and tall, skinny CAPE profiles summing to values 1000-1500 J/kg should keep severe threat mitigated. With Corfidi vector speeds ranging from 5 to 15 kts indicating slow cell motion and potential for nearby cell growth on old outflow, along with the aforementioned high PWAT air could have some potentially heavy downpours. Showed rainfall amounts from a quarter inch up to localized 0.50-0.70" amounts along the lee of the Blue Ridge south of Roanoke. Confidence wasn`t high enough to address in the HWO or to add heavy rain wording, though WPC`s overnight Day-2 outlook does have our Blue Ridge counties in a Marginal Risk for excessive rain. A general decrease in coverage and intensity of showers and storms should be expected with sunset and generally ending near midnight, though may have a good deal of cloudiness ahead of the primary cold front. Kept highs in the mid to upper 80s with at least partly/mostly cloudy skies, with lows still on the muggy side in the upper 60s to mid 70s. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 230 PM EDT Wednesday... Weak shortwave trough should lift by to the north on Friday allowing a surface cold front to slowly pivot east toward the region by late in the day. Expect some degree of residual showers preceding the boundary across the west early in the day that could jump into the eastern lee trough during the afternoon where deeper convection still appears possible. Most guidance still not overly impressive with lift ahead of the front, given most upper support shearing out to the north with the passing weak 500 mb trough. This while seeing the boundary layer flow turn more westerly espcly mountains behind the pre-frontal axis early on. However progged instability still quite strong east of the mountains where models suggest a narrow band of shortwave energy crossing into the piedmont late. Late day timing could allow for better convergence from the Blue Ridge east espcly if the low level flow backs southwest, and progged very high 850 mb theta ridging materializes. Therefore keeping chance pops with highest out east. Highs again mostly 80-85 mountains to lower 90s east given downslope but also convection dependent. Surface cold front should cross the region Friday night into early Saturday, booted along by a stronger upstream shortwave trough that will pass just north Saturday night. Model consensus shows some lingering convection along the front mainly southeast early Friday night before deeper moisture gets shunted to the east early Saturday. However just how far southeast dry advection can get Saturday remains iffy espcly ahead of the strong upstream shortwave. Latest trends suggest perhaps just enough low level moisture with heating to still spark an isolated shower/storm mainly southeast sections later Saturday so left in a mention. Otherwise should be a bit drier Saturday afternoon with dewpoints dropping off espcly west, and only slight evening pops far south Saturday night for now. Still quite warm Saturday with highs low/mid 80s to near 90 southeast with somewhat cooler lows in the 60s overnight behind the front. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 130 PM EDT Wednesday... Exiting upper trough by late in the weekend will evolve into strong ridging across the region for early next week as Bermuda high pressure links with building heights over the southeast states. Appears this in combination with weak surface high pressure ridging in from the north and lack of upper support, will act to keep a lid on most organized convection for Sunday into Monday. However given close proximity of at least low level moisture near the residual front over far southern sections, will need to leave in an isolated diurnal convective mention espcly southern Blue Ridge for now. Otherwise will be leaving things mostly dry with more clouds far south and less northern half into Monday. Ridging will begin to flatten Tuesday in advance of the next digging 500 mb trough that looks to push another cold front toward the region by midweek. Return moisture ahead of the boundary and less cap should support a scattering of showers/storms Tuesday afternoon especially mountains. Expect a bit more organized convection ahead of the front and under cooling aloft Wednesday when will have medium to high chance pops. Better ridging and warming 850 mb temps to around +22C suggests a rather warm/hot period with highs mostly 80s, except around 90 or warmer piedmont, before cooling slightly on Day7 per more showers around. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... As of 810 PM EDT Wednesday... Upper short wave is pulling off to the east but surface frontal boundary continues to linger over the region with some isolated showers/rumble of thunder. Believe there will be some isolated showers stewing around through the overnight and expect low/mid clouds to be on the decrease, but there is a good amount of uncertainty in how much cloud cover will remain overnight. While this will limit radiational cooling, ample moisture in the boundary layer will allow for some fog formation late. Expect LIFR cig/vsby to set in at KLWB where cloud coverage is already scant, and a tempo to MVFR conditions elsewhere with KROA expected to remain VFR. However, confidence in fog/stratus formation is medium at best as it is tied to extent of higher cloud cover. More upper clouds will result in less fog. Better forcing and increasing moisture along the frontal boundary tomorrow will yield greater coverage of showers/thunderstorms by Thursday afternoon. Winds will generally be light through the period. Extended Aviation Discussion... Expect a continued increase in shower/thunderstorm coverage and strength, lasting until 03z Friday. Outside of thunderstorms look for VFR conditions. Overnight fog is a possibility in the river valleys and in areas that do see rain, though cloud cover/convective debris may limit its spatial extent. Another round of scattered afternoon showers and thunderstorms Friday associated with the primary cold front, though VFR prevails outside of showers or storms. Dry advection and light to moderate west to northwest winds behind the front Friday night could keep overnight fog coverage limited, but a potential sub-VFR ceiling is possible at Lewisburg and Bluefield. Mainly VFR conditions for the weekend under weak high pressure. && .EQUIPMENT... As of 755 PM EDT Saturday Aug 12th... KFCX doppler radar will continue to be down for the rest of the month due to a failing bull gear. It will only be operational during this time frame for brief periods if an imminent significant widespread severe weather and/or hydrologic event occurs. Operating the system for any amount of time until the bull gear is replaced risks a catastrophic failure that would further extend system downtime. From the 17th through the 27th the radar will most likely be down completely as the repairs are expected to be made during this period. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AL NEAR TERM...AL/MBS/RAB SHORT TERM...JH LONG TERM...JH AVIATION...AL/MBS EQUIPMENT...RAB/WERT
Area Forecast Discussion
National Weather Service Shreveport LA
949 PM CDT Wed Aug 16 2017 .UPDATE... Isolated evening convection has ended for the time being but now we begin to look upstream across Oklahoma where a line of convection currently exists along a southwest to northeast oriented cold front. This convection is probably best progd by the HRRR which is quicker bringing the convection down into the I-30 Corridor than the slower 00z NAM output which has initialized too slow. For this reason, have beefed up late night pops...mainly along and northwest of the I-30 Corridor and beefed up pops across mainly our northern zones Thu morning and across our eastern half by Thu aftn. Concerning the update, cirrus has really thinned across our southeast most zones and thus have gone with partly cloudy sky grids through all but the predawn hours when we should begin to see the effects of the convection to the northwest add some sky cover to at least this portion of our region. Hourly fcst temps are in the ballpark to current temps as are fcst overnight min temps so no other changes were necessary attm. Updated zone package out shortly...13. && .PREV DISCUSSION... /issued 728 PM CDT Wed Aug 16 2017/ AVIATION... VFR conditions to prevail through the evening and much of the overnight hours, with MVFR/patchy IFR stratus to move in to most sites around sunrise. In addition, a cold front will dip swd into our area early Thursday, bringing shwrs/tstms to several of our sites through the day. Have opted to only use VCTS attm, but will consider prevailing groups for some sites with a later TAF package. /12/ && .PRELIMINARY POINT TEMPS/POPS... SHV 78 93 76 94 / 10 40 20 40 MLU 76 92 75 92 / 10 40 20 40 DEQ 76 87 73 91 / 60 50 20 40 TXK 77 88 74 92 / 30 50 20 40 ELD 77 90 74 92 / 10 50 20 40 TYR 79 92 77 94 / 10 40 20 20 GGG 79 92 77 94 / 10 40 20 30 LFK 78 96 77 95 / 10 30 10 20 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...Heat Advisory from noon to 7 PM CDT Thursday for LAZ010>014- 017>022. OK...None. TX...Heat Advisory from noon to 7 PM CDT Thursday for TXZ149>153- 165>167. && $$ 12/13