Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/21/18

Area Forecast Discussion
National Weather Service Bismarck ND
948 PM CDT Fri Jul 20 2018 .UPDATE... Issued at 941 PM CDT Fri Jul 20 2018 Made some minor adjustments to sky cover. Lowered temperatures a bit central and added a mention of patchy fog over portions of the central, mainly between Bismarck and Jamestown, and from Harvey down to the SD border. Overnight shift can modify as needed. Lots of rain here recently and appears to be a good radiational cooling setup with the position of the surface high early Saturday morning. HRRR, RAP and GFSLAMP are all hinting at possible fog in this area tomorrow morning. UPDATE Issued at 551 PM CDT Fri Jul 20 2018 For the early evening update only a few minor changes. We bumped up sky cover a bit Saturday afternoon in the James River Valley per forecast soundings. Did not increase sky cover enough to produce a ceiling but this may be possible. We also bumped up winds in the west Saturday afternoon into the 15 to 25 mph range. Could be some patchy fog over central ND per the latest iterations of some of the mesoscale models but confidence not high enough at this time to add to the forecast. Will see how models trend through the evening. && .SHORT TERM...(This evening through Saturday Night) Issued at 212 PM CDT Fri Jul 20 2018 Possible smoke impacts this evening into Saturday, and severe thunderstorm potential west Saturday evening highlight the short term forecast. The main question for this evening through tomorrow is possible smoke impacts from a fire approximately 115 miles northeast of Winnipeg as smoke may be transported in the low levels around the surface high. Visibility across the northern Red River Valley and northwest Minnesota downstream of the fire is reduced as low as 4 to 7 miles. The experimental 12Z HRRR-Smoke forecast would suggest an increasing potential for near-surface smoke across western and central North Dakota this evening through tonight, and possibly lingering into Saturday. Will continue to monitor upstream satellite and surface observation trends. For Saturday, did increase highs across the west into the upper 80s and lower 90s, closer to the warm edge of the 12-15 UTC guidance envelope with the low level thermal ridge axis. Regarding convective potential, SPC has placed a Slight Risk across northeast Montana, into far northwest North Dakota, with a Marginal Risk extending east to approximately Portal through Dickinson and Hettinger. The 12 UTC CAM and global consensus is for convection to initiate late Saturday afternoon or early evening across eastern Montana along the cold front and inverted trough. This convection may approach the North Dakota border around 00-03 UTC. While deep layer shear is strong, around 40-50kts and oriented generally orthogonal to the surface boundaries, the zone of 1500-2000 j/kg of MLCAPE is rather narrow, and quickly drops off across western North Dakota. While organized convection, including possibly a supercell or two, may enter western North Dakota Saturday evening, the approach of sunset and propagation too far east of the best instability should limit the severe threat to the west and likely ending by 06 UTC. Thunderstorms may be sustained into the night across central North Dakota with the low level jet, however, their intensity should be weaker and likely less organized. .LONG TERM...(Sunday through Friday) Issued at 212 PM CDT Fri Jul 20 2018 Severe thunderstorm potential central on Sunday highlights the extended forecast. A cold front with a mid level jet streak/shortwave will be the focus for thunderstorm development across central North Dakota Sunday afternoon and into the early evening. Cloud cover impacts from likely ongoing morning convection adds uncertainty to afternoon heating and destabilization. Deep layer shear around 40kts, and generally orthogonal to the cold front, would support the potential for discrete organized convection. Precipitable water climbing to around 1.75 inches supports the potential for locally heavy rainfall, including across portions of the James River Valley that saw very heavy rainfall earlier this week. For much of next week, rather fast west-northwest mid level flow south of the Canadian upper level low supports sporadic chances for thunderstorms associated with low predictability impulses. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 941 PM CDT Fri Jul 20 2018 VFR conditions expected this evening with Northeast winds diminishing and shifting southeast. Patchy fog possible mainly between KJMS and KBIS but not confident enough to add to either TAF at this time. Could be a couple hours of MVFR ceilings late morning or early afternoon at KJMS as Cu field flattens and begins to lift. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...TWH SHORT TERM...PA LONG TERM...PA AVIATION...TWH
Area Forecast Discussion
National Weather Service Caribou ME
944 PM EDT Fri Jul 20 2018 .SYNOPSIS... High pressure will exit to the east Saturday. Low pressure will lift north across the region Sunday. && .NEAR TERM /THROUGH SATURDAY/... 9:44pm update...Biggest change to near term is bumping up cloud cover along the Downeast coast. Light winds and high humidity has harbored growth of a fog shelf just offshore and in some coastal communities. Webcams in Winter Harbor and Bass Harbor confirm the sea level fog working its way towards the coast. Like the HRRR depiction of this bank staying just along coastal Hancock and Washington counties through early morning. Previous discussion: High pressure will cross the region tonight then exit to the east Saturday. Skies will remain mostly clear across northern and central portions of the forecast area tonight through Saturday. Across Downeast areas, expect mostly clear skies much of tonight. However, cloud cover could increase later tonight with low clouds and fog moving inland from the Gulf of Maine which could persist early Saturday. The low clouds will retreat offshore later Saturday morning, leaving mostly sunny skies from late morning through the afternoon. Low temperatures tonight will range from the mid to upper 50s across northern/central areas, to the mid 50s Downeast. High temperatures Saturday will range from the mid to upper 80s north. Temperatures will be cooler across Downeast areas with onshore winds from the Gulf of Maine. High temperatures across interior Downeast areas will range from around 80 to the lower 80s, with temperatures generally ranging through the 70s along the Downeast coast. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... Subtropical low pressure moving north across eastern or central NY Sat night will drive clouds north across the state. Precip will push northeast into the CWA by mid-morning Sun, with high- end chance to likely POPs across much of the central and southern CWA during the afternoon. Precip may die off a bit Sun night, but kept chance POPs across most of the CWA as there will be ample moisture coming onshore. The upper ridge may build back west a bit during the day Mon, leading to reducing POPs over Downeast. However, the axis of action appears likely to shift inland, especially over the northwestern higher terrain, during the afternoon Mon. Expect highs in the low to mid 70s Sun, and in the mid 70s to around 80 Mon. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Pattern remains active for much of the long term as the upper trough remains off to the west through at least Thurs. POPs Tue and Wed highest for central and NWern areas. A wave moving across the area Thurs could spread a better chance of precip back toward the coast. Models seem to be keying in on the upper trough finally starting to shift east on Fri, pushing through a front, with some drier air and likely lowering POPs for later Fri into Fri night. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... NEAR TERM: Low clouds and fog will likely reach Downeast areas late tonight with MVFR to LIFR conditions persisting through early Saturday. Conditions will then improve to VFR levels Downeast through the morning, with VFR conditions persisting through the afternoon. VFR conditions are expected across northern and central areas Saturday. SHORT TERM: IFR to LIFR CIGs and perhaps IFR or lower vsby for KBHB and KBGR developing Sat night. Widespread IFR CIGs will spread northward through the day Sun and persist through much of Monday. Fairly widespread MVFR to IFR CIGs expected through mid-week as the weather pattern changes little. && .MARINE... NEAR TERM: Winds/seas are expected to remain below small craft advisory levels tonight through Saturday. Visibilities will be reduced in areas of fog later tonight with patchy fog through Saturday. SHORT TERM: Light wind and seas under 4 feet will continue through Sat night. Winds will increase during the day Sun and remain moderate breezes with gusts up toward 20kts through Mon. Seas will build Sun, and may exceed SCA criteria Sun night into Mon. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...None. && $$ Near Term...CB/Cornwell/Norcross Short Term...Kredensor Long Term...Kredensor Aviation...CB/Cornwell/Norcross/Kredensor Marine...CB/Cornwell/Norcross/Kredensor
Area Forecast Discussion
National Weather Service Cleveland OH
900 PM EDT Fri Jul 20 2018 .SYNOPSIS... Slow moving low pressure will track from southern Lake Michigan tonight into the Ohio valley by Sunday. The low will weaken and dissipate as it drifts into the Tennessee valley Monday. A cold front will slowly move across the area during the middle of the week. && .NEAR TERM /THROUGH SATURDAY NIGHT/... Convection has pretty much died down so went with scattered showers and isolated tsra for the overnight period. Also removed mention of potential for severe tsra from HWO. Rest of forecast looks reasaonable for the 930 update. Original discussion... Not many changes to the forecast tonight through Saturday night, with the focus of the forecast on convection/severe potential this evening and precip chances Saturday. A slow moving, vertically stacked low will track from near Lake Michigan this evening southward into the Ohio valley late Saturday night into Sunday morning. Several waves of precipitation will rotate east-northeast across the region, with a focus on diurnal development during the afternoon on Saturday. In the immediate, ongoing showers/storms across far northeast Ohio and northwest PA will continue to work northward late this afternoon, while and area of rain with embedded thunderstorms pushes east across the southern part of the area, south of US-30, over the next couple of hours, generally in a weakening trend. Focus turns to line of convection currently across northern Indiana. Modest/narrow corridor of 1000-1500 j/kg SBCAPE exists ahead of this line, with fairly weak/marginal effective bulk shear values of 30 kts or so. Biggest challenge is the intensity trend of this line, and whether or not it will remain organized and severe into the I-75 corridor a couple hours from now. Hi-res guidance has been consistent in weakening any convection as it tracks into the local area around/after 00Z, however the latest runs of the HRRR are not handling the speed/intensity of the current line. The line may weaken if the instability corridor gets pinched off between the advancing severe line and the more stable boundary layer near the I- 75 corridor from ongoing or recently ended rainfall. Still have high likely pops working into the I-75 corridor from 22Z to 00Z, and think there is some potential for a few organized/strong storms to sustain into the area. Convection should diminish from 03Z onward through the night. Kept pops generally in the chance range overnight with a brief period of likely pops across the southern part of the area towards morning, as an area of lift associated with the low level jet moves into the southeast part of the forecast area, with a consistent signal of precip development in recent model runs. A lull in convection is possible through the morning hours tomorrow, however have ramped pops up to likely across the area in the afternoon as modest destabilization of 500-1500 j/kg occurs across the area. Have again trended pops downward through the evening/overnight with a loss of instability. Kept temps near previous forecast tonight and Saturday night, and maybe a degree or two lower for highs on Saturday given expected cloud cover and scattered precip. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... The upper level low will weaken on Sunday as it drifts southward. However with the cooler air aloft within the upper level trough we will have to maintain chances of showers and thunderstorms. Another piece of energy will approach Monday night into Tuesday with chances of thunderstorms increasing by Tuesday afternoon. Sunday looks to be the cool day of the short term with highs in the middle 70s. Seasonal temperatures Monday into Tuesday with highs in the lower to mid 80s. && .LONG TERM /TUESDAY THROUGH FRIDAY/... The long term begins Tuesday night with models showing weak forcing across the area however at the surface there should be a cold front/trough bisecting the area. Best chance of precip should be east with lower level flow bringing atlantic moisture into the area from the southeast. Will have chance pops east to start the night and go up to likely pops after midnight as moisture increases. For Wednesday will continue with the likely pops far east, chance through the central lakeshore and highlands to nothing northwest. Wednesday night and Thursday models try to bring drier air in slowly from the northwest, shifting the best moisture east. The cold front will also shift east and dissipate as another cold front moves into the region from the northwest. With the drier air in place however believe rain chances still drop through the 24 hour period. For Thursday night and Friday high pressure begins building in from the northwest so will go with a dry forecast. Highs Wednesday should get into the low and mid 80s with a few upper 80s west. Thursday and friday look for highs 80 to 83. && .AVIATION /00Z Saturday THROUGH Wednesday/... Thunderstorms moving into TOL area have diminished significantly last 2 hours. Expect showers and tsra to become more scattered after sunset. Expect widespread MVFR to develop overnight with areas of IFR in the West, as the low over Lake Michigan drifts east. OUTLOOK...Non-VFR possible Saturday and Sunday with showers and thunderstorms. && .MARINE... Stacked low pressure will drift from Lake Michigan to southwest Ohio by Sunday morning. This will keep south to southeast wind going on the lake through Saturday afternoon. Winds will then shift a bit more to the east as the low weakens as it drifts further south. Current thinking is that he southeast to south winds will be low enough to avoid the issuance of a small craft advisory. However stronger gusts may occur with any thunderstorms. Low level lapse rates steepen enough on Saturday to be concerned about waterspouts. While it does look marginal the proximity of the upper level low makes us think that the spouts could occur across the western half of the lake from Toledo to Avon. By Sunday easterly winds will increase with a good chance that we will need a small craft advisory. We will take a closer look at this tomorrow. The winds will only slowly decrease Sunday night into Monday becoming light Monday night and remaining that way into Tuesday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Greenawalt NEAR TERM...DJB/Greenawalt SHORT TERM...Mullen LONG TERM...TK AVIATION...DJB MARINE...Mullen
Area Forecast Discussion
National Weather Service State College PA
941 PM EDT Fri Jul 20 2018 .SYNOPSIS... The recent stretch of pleasant and conformable weather across central PA will come to an end this weekend, as the pattern turns decidedly unsettled, muggy and rather wet through next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Convection west of CWA has dissipated leaving the area with a quiet night tonight. Latest HRRR runs show large area of rain approaching SE zones after sunrise, which is covered well in forecast. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Hybrid coastal low will track north along the mid Atlantic coast from eastern NC across the Delmarva on Saturday and approach southern New England by Sunday morning. This low will eventually be absorbed by the anomalous deep-layer cyclone that is expected to move slowly southeastward into the Ohio Valley. Confidence has increased significantly in a period of heavy rain spreading northward across the eastern 1/3 of the CWA later Saturday afternoon into Saturday night. The 12Z HREF mean shows a cyclonically curved, 50+kt LLJ drawing deep moisture inland ahead of the hybrid low, with PWs reaching 1.5 to 2.5 inches over southeast PA. There is definitely a short-duration flash flood risk given the impressive PWs, strong lift and low level moisture transport, but limiting factors include dry antecedent conditions, high FFG and low CAPE. 1-2 inch amounts are likely with localized higher amounts possible. Despite high confidence in a period of heavy rain, decided to hold off on FF watch given aforementioned factors and preference toward a more short-fused issuance. Added heavy rain/ff threat in the HWO. Clouds will hold daytime temps in the low to mid 70s, and it will feel more humid and muggy. && .LONG TERM /SUNDAY THROUGH FRIDAY/... By 12z Sunday, compact coastal low will be sliding north of the area. But very gradually filling inverted low will edge toward western PA while continuing to channeling tropical-like moisture into the region - keeping unsettled weather ongoing through much of next week - peaking in the afternoons. Best daily chances for tstorms shifts to western/central sections Tue/Wed before returning eastward Thu as a cold frontal boundary finally pushes across the state. Temperatures will be below normal Sun with thicker cloud cover and moist SE/E flow, then highs return closer to normal for next week while lows look to remain on the muggy side. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... VFR conditions across the region this evening. Banded showers moving south to north over western Pennsylvania. Expect VFR conditions to continue into Saturday morning, followed by lowering conditions during Saturday as low clouds and showers develop across the airspace. Low VFR to MVFR ceilings are probable Saturday into Saturday night, with some pockets of IFR Saturday night into early Sunday. Showers are expected to spread northward from the Delmarva/Chesapeake Bay region into the south central/southeast airspace early Saturday morning. Expect a period of moderate to heavy rain later Saturday afternoon into Saturday night across the eastern airspace. Unsettled weather with showers and isolated thunderstorms to continue into mid week. .Outlook... Sat...VFR start early, then conditions lowering to MVFR in all areas except VCTY KBFD. Sun-Wed...Frequent showers/isolated T`storms with associated MVFR/IFR restrictions. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl NEAR TERM...Ross/Steinbugl SHORT TERM...Steinbugl LONG TERM...RXR AVIATION...Jung/Steinbugl
Area Forecast Discussion
National Weather Service Grand Forks ND
950 PM CDT Fri Jul 20 2018 .UPDATE... Issued at 950 PM CDT Fri Jul 20 2018 Adjusted POPs a bit for current radar trends as showers over our far eastern tier have pretty much dissipated. Only a few sprinkles remain and will be completely gone in an hour. Smoke will continue to be in issue in some areas but will eventually shift further west as winds begin to turn. && .SHORT TERM...(This evening through Saturday) Issued at 237 PM CDT Fri Jul 20 2018 Air quality alert from the Minnesota Pollution Control Agency in effect until 9am Saturday morning. Smoke from Canadian wild fires leading to reduced visibility and air quality concerns. These conditions will improve by later tonight as the low level flow becomes more easterly and keep the smoke plume north of the region. Upper low will continue to propagate off to the east, with scattered showers (isolated thunder) east of the valley into the evening. Timing the clearing clouds will be the main challenge, which should gradually clear from west to east, but will likely remain across the far eastern FA into Saturday morning. Ridging will build into the region on Saturday, leading to relatively quiet weather with temperatures near normal values. .LONG TERM...(Saturday night through Friday) Issued at 237 PM CDT Fri Jul 20 2018 A shortwave H5 ridge will influence the weather pattern going into Sunday. This will be enhanced by an upper low moving eastward out of Alberta. Winds aloft shift from northwesterly to southwesterly through the day as this low moves into Saskatchewan. Surface winds become southeasterly, allowing moisture levels to increase; however, the relative strength of the low level flow will be weak. Although we expect mostly sunny skies during the early part of the day, increasing cloudiness and precipitation chances become the story during the afternoon hours. Increasing CAPE and generally favorable shear patterns will allow potentially severe thunderstorms to develop along and ahead of a cold front. The highest instability looks to remain west of the Red River with CAPE values approaching the 1500 to 3000 J/Kg range briefly during the late afternoon/early evening. The setup will be favorable for a multi-cell or weak supercell mode with hail, damaging wind gusts, and tornadoes all being possible. The H5 upper low moves slowly through Saskatchewan on Monday before moving into Manitoba on Tuesday. Shortwave troughs of varying strength will pivot around the low, bringing unsettled weather into the region during the Monday through Wednesday period. Another chance of storms is in the forecast for Tuesday evening. Strong to severe storms are possible, however, confidence is low regarding the exact details at this time. Slight rain and thunderstorm chances remain in the forecast on both Wednesday and Thursday with isolated to scattered coverage expected. Much cooler high temperatures in the lower to middle 70s prevail both days. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 700 PM CDT Fri Jul 20 2018 Some MVFR ceilings at KBJI and KTVF moving in and out as some cumulus and showers on the backside of a low pressure system rotate through. All TAF sites should be VFR by later this evening. Still some smoke in the area, although it is not currently affecting visibility. HRRR has the smoke plume shifting southwestward and becoming less dense. Thus, will keep out of the TAFs for now and just amend as needed. North winds around 12 kts will become more northeasterly and decrease towards the end of the period. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JR SHORT TERM...TG LONG TERM...Lynch AVIATION...JR
Area Forecast Discussion
National Weather Service Goodland KS
922 PM MDT Fri Jul 20 2018 .UPDATE... Issued at 922 PM MDT Fri Jul 20 2018 Main severe threat appears to have shifted east of southern portions of the CWA for this evening. Have left in a slight chance for a shower(rw)/thunderstorm(trw) for the next few hours for mainly locales along and south of Hwy 40. No other changes at this time. && .SHORT TERM...(This evening through Saturday) Issued at 255 PM MDT Fri Jul 20 2018 The Tri-State area is situated on the northeast periphery of an upper level ridge, at the southern fringe of speedy NW flow aloft. Light easterly flow will prevail in the low- levels this afternoon into tonight, on the northern periphery of a weak surface low situated over southeast CO/southwest KS. Through Tonight: Challenging convective forecast. The HRRR and NAM NEST continue to suggest that scattered convection will develop invof the aforementioned sfc low along/south of Cheyenne/Greeley/Wichita counties in southeast CO and southwest KS late this afternoon and evening -- where weak low-level convergence is present amidst little/no CIN -- with virtually no development in northwest KS and northeast CO where low-level forcing is weaker and 50-150 J/kg of CIN persists (as of 20Z). Unless forcing is augmented by DPVA attendant a small amplitude wave at the southern fringe of NW flow aloft, the atmosphere is likely to remain capped in northwest KS and northeast CO -- which is fortunate -- because the thermodynamic/kinematic environment in northwest KS is otherwise quite supportive of supercells capable of producing very large hail and damaging winds. At this time, expect convection to be confined well south of US 40, where the thermodynamics/kinematics favor multicellular organization and a brief/intermittent potential for severe downbursts. Convection will wane by 03-06Z in assoc/w loss of heating /increasing CIN/. Saturday: The upper level ridge building eastward over the High Plains is expected to result in pronounced capping /dry conditions/. Expect highs in the lower to mid 90s. .LONG TERM...(Saturday night through Friday) Issued at 127 PM MDT Fri Jul 20 2018 The long term period starts with the region under northwest flow aloft between a ridge across the southwestern CONUS and an upper trough over the eastern half of the country. The pattern remains in place through the weekend as a second upper trough cuts across the Canadian border. A disturbance is anticipated to work its way around the northern edge of the ridge on Saturday which may result in a few storms developing in central Colorado and progressing into our western CWA during the evening hours. However, capping may limit convection. After dry conditions during the day Sunday, better precipitation chances return to the forecast Sunday night. The second trough continues towards the Great Lakes, shifting the ridge westward. Meanwhile, a cold front approaches the area, generating chances for showers and thunderstorms across the forecast area. With PWATs at 1.5 inches, locally heavy rainfall still looks to be a threat. The front continues to pass through the rest of the region early Monday, dropping temperatures for the start of the work week. Throughout the remainder of the long term, a series of shortwaves pass through the northwest flow aloft as the upper trough digs into the Upper Midwest, pushing ridging towards the west coast. This results in better moisture filtering into the area and persistent thunderstorm chances through Friday. Will continue to monitor the potential for severe weather as this timeframe approaches. High temperatures peak in the 90s on Sunday before decreasing mainly into the 80s for the rest of the week. A few locations could see some readings in the low 90s Wednesday and beyond. Low temperatures will stay in the 60s. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 529 PM MDT Fri Jul 20 2018 With high pressure over the terminal region for during the forecast period...both sites will have VFR conditions w/ mainly scattered high clouds. Winds for KGLD...E 10-20kts thru 02z Saturday then SSE 10-20kts. Winds for KMCK...E around 10kts thru 08z Saturday then light/ variable. By 14z...ESE around 10kts...w/ gusts to 20kts after 19z. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ UPDATE...JN SHORT TERM...VINCENT LONG TERM...JBH AVIATION...JN
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1032 PM EDT Fri Jul 20 2018 .SYNOPSIS... High pressure will weaken over the forecast area before a large upper low drops south from the Great Lakes to the Southern Appalachians tonight. This low will remain nearly stationary for several days and support unsettled weather through the middle of next week. && .NEAR TERM /THROUGH SATURDAY/... As of 1015 PM EDT Friday: Still seeing MCS convection march across E TN, and as of this update MRX has issued SVRs right up to the state line. Have increased pops just along the spine of the Appalachians a little over the next couple of hours, but based on CSTAR research on MCSs crossing the southern Appalachians, the thermodynamic environment across the lee of the mountains really does not support the MCS sustaining itself much farther east. Would expect that we might have to issue a few SPSs and not totally out of the question to see a SVR or two, but should not spread too far east. This is shown pretty well in CAM reflectivity guidance. Of increasing concern, however, is a secondary wave of convection just starting to get going across Middle TN, and the HRRR and other CAMs DO have this round of convection pushing east overnight and into the southern mountains and north GA, upper Savannah Valley, around sunrise. We`ve been watching these CAM trends for a few hours now and have seen a consistent uptick in this, especially with some of the 00z HiRes windows in now. Have increased pops accordingly. Other grids look to be on track for now. Otherwise, the potential for severe thunderstorms will dominate the latter part of the near-term period Saturday. For the setup, a 500 mb low center over Lake Michigan this evening will continue to carve out height falls across the Tennessee Valley and into the southern Appalachians through the nighttime hours. Meanwhile, a low pressure system along the coastal plain will move from SC to NC tonight with just a continued low end threat of isolated showers along our eastern piedmont fringe in weak deformation. A series of developing MCSs will make a run south and east of the OH Valley and central TN, but with most of the high resolution, convection allowing models showing little impact across our forecast area overnight into Saturday morning. The most recent runs of the HRRR are the most aggressive, showing upstream convection filling in across central Tennessee and eastern Kentucky by early evening and then brushing the northern mountains and the Smokies vicinity before dissipating in the weaker instability across the high terrain late evening/early overnight. Additional activity may develop and make a run overnight, but with little more than scattered showers and thunderstorm to advertise along the TN/NC border through daybreak. Forcing, instability, and shear should then come together for Saturday. Although profiles look rather capped early in the day tomorrow, the cap should be explosively overcome during the afternoon hours, with 2000 to 3000 J/kg of sbCAPE likely realized east of the Blue Ridge. The best pocket of 7+ deg C/km mid-level lapse rates will then cross the region from mid-afternoon to early evening. The mid-level speed maximum rounding the upper trough will likely yield surface to 6 km bulk shear values of 30 to 35 kt by 21Z Saturday. However, shear will be quite a bit weaker in the lowest 1 to 2 km of the atmosphere and this may toggle the severe potential away from tornadoes to more of a damaging wind/hail threat. Anticipate the better spokes of upper level vorticity under the dominant trough to cross the region mainly from mid afternoon to mid evening and this better forcing should promote the greatest coverage and highest severe thunderstorm chances. Most of our area remains in a well-placed Slight Risk of severe thunderstorms for Saturday. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As of 215 PM EDT Friday: Robust,if not severe, deep convection should be ongoing and numerous at the start of the period, all within the unseasonable moderate deep cyclonic flow around Ohio Valley closed low. Overall coverage will in no doubt wane overnight, but the pattern will remain favorable for some degree of regeneration at any point overnight, so at least low chance pop will remain into early Sunday morning. Through Sunday, upper low will continue it`s southward drift and slowly fill, which will actually result in weaker shear and a little bit of drier air working in from the west. But, at this point, it is hard to believe that diurnally enhanced deep convective coverage won`t become numerous again, especially across western NC. Sunday maxes still should about a category below climo under the influence of the upper low. With the axis of the filling upper low lingering atop the region through Monday, the potential for a deeper southerly flow and influx of rich Atlantic moisture increases. This setup may result in excessive rainfall chances increasing. With Lots of clouds and rainfall progged, max temps may wind up being at least 5 deg f below normal. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 1230 PM EDT Friday: Not a lot of changes made to the ext fcst from the previous package. The op models and ens means agree well with a broad yet weak stacked low sw of the FA to begin the period. This low will likely become more disorganized beginning Wed as an ulvl trof picks it up and shears it out. The mean flow within the sfc-h85 layer will begin e/ly which will provide very good Atl moist flux. Soundings show pwats on the order of 2.00 inches Tue and the potential of some hydro concerns...esp across the eastern facing upslope zones. As the stacked low dissipates the flow becomes less defined and rather weak thru the the potential for upslope heavy precip will lessen. There will be some instability and tstms during this time...but it will remain conditional with llvl sbCIN persisting each afternoon. Will keep the higher mention PoPs each day with some reduction on Fri as a weak cold front shud cross the region during the day limiting convec moreso across the mtns. However...there is much uncertainty with the timing of this front attm. With high cloud cover each day...max temps will be held a cat or so below normal...while mins persist abv normal within weak rad cooling. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... At KCLT and Elsewhere: VFR this evening and into the early overnight period, but this will be short-lived as a round of MVFR to possibly IFR cigs develops especially across NC TAF sites during the pre-dawn hours as moisture increases. Convection to our west is progged to fall apart before it crosses the mountains, with another round of convective potential around daybreak, but confidence still to low to mention more than VCSH at KAVL. Of greater concern is convective potential for Saturday afternoon and have mixed a combination of VCSH/PROB30 TSRA around midday, transitioning to prevailing TSRA at all sites by 18-20z. With SPC slight risk in place, some of these thunderstorms could become severe with damaging winds, but will hold off on including enhanced wind wording until we are in a TEMPO time frame and can narrow down timing with greater confidence. NNE winds this evening will continue to back around the compass NW tonight and toggle WSW to SW just ahead of the approaching trough on Saturday. Outlook: An active/wet period is expected to continue from Sunday through the middle part of next week as a slow-moving storm system begins impacting much of the East. Numerous showers and thunderstorms are expected during this period. While there will likely be an afternoon/evening peak in coverage on most days, higher- than-normal chances will also exist during the overnight and morning hours. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 100% High 92% High 90% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% Med 75% High 100% High 100% KHKY High 100% Med 77% High 86% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...SBK NEAR TERM...HG/TDP SHORT TERM...CSH LONG TERM...SBK AVIATION...TDP
Area Forecast Discussion
National Weather Service Huntsville AL
909 PM CDT Fri Jul 20 2018 .NEAR TERM...(Tonight) Issued at 909 PM CDT Fri Jul 20 2018 The TN Valley is still playing the waiting game this evening. Regional 00Z soundings and Univ. of Alabama-Huntsville soundings all continue to indicate a highly unstable atmosphere. There is some deep-layer shear in place but little low-level shear--at least for now. Both UAH and BMX soundings show a very small cap around 800-825 mb, while the OHX sounding has it almost completely eroded. All that is missing is some lift to erode this cap and realize the instability. Severe convection so far has been limited to east Tennessee, but convective initiation is occurring across Arkansas as of 02Z/9pm. Convection-allowing models have been all over the place today. There are signs that the 00Z CAM runs are beginning to get a better handle on the situation but it is tough to put a lot of faith in them. Several CAMs suggest explosive development over central/eastern Arkansas, which then brushes NW Alabama in the 04-06Z timeframe. The latest HRRR puts very little over the area for the entire overnight period--but also is not resolving current upstream conditions very well. So the 00Z CAM consensus is about the best available option for right now. Instability is not a concern at this point, and deep- layer shear should be fairly robust. Low-level shear will increase over the next 2-4 hours as a low-level jet kicks into place around the parent low, so the tornado watch seems reasonable for now. As far as the forecast, precipitation has been delayed about 3-4 hours, with PoPs peaking from about 05-09Z. Otherwise, based on current trends, both temperatures and dew points have been nudged upward for the rest of the night. .SHORT TERM...(Saturday) Issued at 253 PM CDT Fri Jul 20 2018 The upper low will continue to move east into the Ohio valley on Saturday with a cold front moving through the local area through the day and probably out to the east by Sat night. Although guidance isn`t too excited about spitting out some QPF for Saturday, the cold front and upper wave will provide decent lift for storms. Instability should still increase rapidly by the afternoon combined with high bulk shear and even some low level shear given a llj increasing through the afternoon. Would think we would see something strong along the line but we could be too worked over from today. If we ultimately don`t get much of anything on Friday (totally possible) this would set the stage for stronger storms on Saturday. For now, stay weather aware on Saturday with damaging winds being the highest threat. Temps will rise to the upper 80s to lower 90s with heat index values remaining near 100. .LONG TERM...(Saturday night through Friday) Issued at 253 PM CDT Fri Jul 20 2018 Most models move the main front to our southeast by Saturday evening. The exception to that is the GFS which is a bit slower with the frontal progression and continues to show more widespread showers and thunderstorms near/east of I-65 through midnight before dissipating. This, as alluded to before, seems to be the outlier. Therefore, keeping a token 20 to 30 percent chance of showers/thunderstorms in the forecast east of I-65. Should be slightly cooler with overnight lows dropping into the mid 60s to around 70 degrees. On Sunday, models are in fairly good agreement that the strong surface low over the Ohio Valley moves far enough south to produce 20 to 50 percent shower and thunderstorm chances through much of the day. Wouldn`t be surprised if more widespread showers and thunderstorms developed in southern middle Tennessee (more consistently impacted by the southern edge of the stronger surface low). Decent instability with wet-bulb zero heights around 11,000 feet and some dry air aloft could still produce some scattered strong to marginally severe storms producing up to quarter size hail and wind gusts around 55 mph. However, with much weaker shear, do not think this will be very widespread in nature. Expect with cloud cover and more widespread precipitation than the previous day, that highs will be a bit cooler, in the 83 to 88 degree range. Coolest afternoon temperatures should be in northeastern Alabama and southern middle Tennessee. As the surface low pulls further east in the evening, precipitation chances should diminish and become isolated to scattered. The large surface low continues to meander between eastern Alabama and Georgia through Monday, before being cut-off from the main jet and sinking southwest into the northwestern Gulf of Mexico by the end of the week. A weak longwave trough axis extends southwest into central Tennessee and to the surface low over the northwestern Gulf of Mexico much of this period in models. This will keep lift over or near the area and abundant moisture/instability will be in place over northern Alabama and southern middle Tennessee. Thus, at least high chances of showers and thunderstorms are expected during the day through the end of the week. Highs generally in the mid to upper 90s are expected much of that period. PWATS remain high, so the atmosphere becomes much saturated throughout the column Monday through Friday. Thus heavy rainfall will continue at times, possibly producing some isolated flooding concerns. Overall high temperatures will be in the mid to upper 80s through much of this period, with lows only dropping into the lower 70s. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 701 PM CDT Fri Jul 20 2018 Quiet weather prevailed across the area for the start of the TAF. This will change over the next few hours, as an upper disturbance brings scattered to numerous showers/thunderstorms this evening and in the overnight. The strongest convection will be moving in from NW-SE during the mid/late evening (coinciding with the stronger shear parameters). Have more confidence of higher winds at KMSL this evening when that area moves across NW Alabama. Isolated to scattered convection should continue in the overnight. The stronger storms could produce gusty winds over 30kt and hail. A frontal boundary moving in from the NW should cause winds to become W-NW during Saturday afternoon. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...BCC SHORT TERM...LN LONG TERM...KTW AVIATION...RSB For more information please visit our website at
Area Forecast Discussion
National Weather Service Wilmington NC
627 PM EDT Fri Jul 20 2018 .SYNOPSIS... Low pressure will move up the coast tonight with widespread rainfall. Saturday will be mostly dry with another system bringing showers and thunderstorms early Sunday. Next week is shaping up to be very unsettled as low pressure moves into the Southeast. && .NEAR TERM /THROUGH SATURDAY/... As of 330 PM Friday...on the synoptic scale, the global models are similar on dropping the upper level low into the Ohio Valley on Sunday. The deep moisture, 2.5" precipitable waters, will be shunted off the coast for a short bit on Saturday during the day before it return Saturday night. At the surface this afternoon the surface low is still in coastal Georgia. The 12 UTC runs of the NAM, GFS, and ECMWF show the low pulling out with the NAM the fastest and GFS the slower. All have the low closing in Hatteras by 12 UTC Saturday. The frontal boundary appears to waffle offshore in the wake of the low. For precipitation today we had a couple of spots to get 3 to 5 inches of rain. Currently the band of overrunning precipitation is running from western Horry county to off the coast of New Hanover county. As mentioned by WPC earlier in the day there has been not lightning with any of these showers, but the lift over the frontal boundary and the abundant moisture are making up for the lack up deep instability. Will continue the Flood Watch to midnight for Horry, Georgetown and Williamsburg counties. But with the GFS and ECMWF slower track of the low have extend the time for the Watch for Brunswick, New Hanover, and Pender counties until 2 AM. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 330 PM Friday...As the upper-level low methodically shifts southeastward, another swath of high precipitable water values moves back over the area. A frontal boundary from the west will be approaching the Carolinas late. The chance of thunderstorms increases overnight Saturday with the extreme western portion of the forecast area. This front is expected to stall over early next week. With the deep moisture feed and the upper-level low to the west during this time there is a good chance of thunderstorms throughout this period. Lows will be in the lower to middle 70s and Highs upper 80s at the beaches and the lower 90s well inland. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 330 PM Friday...A very unusual pattern shaping up for the extended period and if it comes to fruition, it could be a very wet period as well. Guidance has the closed low currently in the Upper Midwest, dropping due south and lingering along the Gulf Coast before basically dissipating and or drifting west by the end of next week. This, combined with the Bermuda High to the east sets up a persistent tropical plume which feeds directly into the area through about Thursday. We are maintaining likely pops throughout most of the period subsiding a little very late as the pattern finally shifts to more of a drier westerly flow aloft. Several inches of rain could fall across the area. Temperatures will be stable with highs mostly in the middle to upper 80s and warm and muggy overnight lows well into the 70s. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... As of 00Z...Low pressure moving up the coast with onshore showers. The coverage and intensity are much less than the models were showing earlier, and the HRRR model has backed off considerably over the last few hours. Nevertheless, look for IFR conditions to spread over the CWA beginning around 05-06Z (based on the LAV). Most of the deep moisture moves out of the region by 13Z, with Pender county the last to see precip as the low exits the region. Conditions will improve to VFR by early afternoon at the latest with west southwest flow becoming southwest along the coast. Extended Outlook...Occasional MVFR to IFR conditions due to scattered SHRA and TSRA Saturday through Tuesday. && .MARINE... NEAR TERM /THROUGH SATURDAY/... As of 330 PM Friday...low pressure is located southeast of Savannah and this low is projected to slowly move northward along the stalled cold front that is hanging just inland from the coast. The latest models are showing at low to move off Hatteras late tonight. The winds will increase to 15 to 20 nm and seas will increase to 3 to 5 feet overnight. As the low shift north the winds will shift offshore and the seas will fall back to 2 to 4 feet. SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 330 PM Friday...A frontal boundary pull northward and winds will shift to the southwest south of the front at 10 to 15 knots. Seas will run 3 to 4 feet Saturday night and increase to 3 to 5 feet late Sunday into Sunday Night. LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 330 PM Friday...Along with the public part of the forecast, the Coastal Waters Forecast looks quite unsettled as well. With surface and mid level low pressure to the west, and Bermuda High Pressure to the east, winds and seas should stay elevated. Expect south to slightly southeast winds of 15-20 knots Monday and most of Tuesday. Speeds should drop back slightly on Wednesday in a 10-15 knot range. These winds will keep significant seas elevated in a range of 3-6 feet. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Flash Flood Watch until midnight EDT tonight for Scz053- 054>056-058-059. NC...Flash Flood Watch until 2 AM EDT Saturday for NCZ105>110. Coastal Flood Advisory until 7 PM EDT this evening for NCZ107. MARINE...None. && $$ SYNOPSIS...SHK NEAR TERM...DRH SHORT TERM...DRH LONG TERM...SHK AVIATION...43
Area Forecast Discussion
National Weather Service Memphis TN
858 PM CDT Fri Jul 20 2018 .UPDATE... Thunderstorms are starting to develop over Central Arkansas at this time. The NAM Nest showed this development on the 18Z run. This could be the start of the expected severe weather. Right now if these storms continue to evolve, best chances for severe storms may be along and south of I-40. Will leave forecast as is for now. KRM && .DISCUSSION... /issued 303 PM CDT Fri Jul 20 2018/ Skies are mostly sunny across much of the forecast area this afternoon with temperatures in the low to mid 90s. Current heat index values are close to 110 degrees in areas where the excessive heat warning is in effect. Currently, a cold front extends from northern Indiana into central Missouri. This cold front will continue to drop south tonight and move into the forecast area overnight. Additional thunderstorms are expected to develop ahead of the front tonight and move into the forecast area. Some of these thunderstorms could become severe with damaging winds as the main threat but large hail and isolated tornadoes can`t be ruled out especially over northwest Tennessee. Temperatures will remain rather seasonable with lows Saturday morning in the low to mid 70s. The cold front will continue to move through the forecast area Saturday with scattered thunderstorms expected ahead of the front mainly over north Mississippi. Temperatures will be a little cooler with highs in the lower 90s. Heat index values will be lower on Saturday so no Heat Advisory should be needed. High pressure will briefly build into the region for Saturday night bringing dry weather and slightly cooler temperatures. An upper level disturbance will drop south into Middle Tennessee on Sunday with scattered thunderstorms possible over eastern sections of the forecast area for Sunday and Sunday night. Monday may see some scattered afternoon thunderstorms over eastern sections of the forecast area. Another cold front will approach the region on Tuesday and move into the forecast area on Wednesday. This will mean more thunderstorms both days. This front will die out across the forecast area on Thursday but another front will start to approach the region Thursday and next Friday so more thunderstorms are expected to form. ARS && .AVIATION... Expect SHRAs/TSRAs to develop in a very unstable atmosphere across the Mid-South as an upper level disturbance moves through in the strong NW flow aloft. Moved the timing for TSRAs up a couple of hours given the ongoing trends and latest HRRR run. Expect most of the activity to push south of the region by sunrise. Saturday looks VFR with gusty NW winds. SJM && && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
1008 PM CDT Fri Jul 20 2018 .DISCUSSION...See updated information for land areas below. && .UPDATE...Relatively quiet evening across the central Gulf Coast region as a subsident and somewhat drier deep layer airmass has advected into our region in northwest flow aloft. There still remains considerable forecast uncertainty regarding storm/severe weather potential across our forecast area through the next 12-24 hours. Regional satellite/radar imagery shows the next complex of severe convection developing across central/eastern portions of AR along a frontal boundary and a shortwave trough pushing southeastward within northwest flow aloft on the southwestern periphery of a larger scale trough axis encompassing the OH/TN Valley regions. The bulk of short range guidance quickly brings this shortwave trough southeastward across the Lower MS River Valley and toward AL through Saturday morning. There remains a lot of spread in the short range and higher resolution convection- allowing guidance on storm development/evolution overnight into Saturday morning, with the past few runs of the HRRR tending to weaken convection before it reaches our CWA early Saturday morning. Nonetheless, ascent and increased deep layer moisture associated with the approaching shortwave trough will support a low potential for convective development into our northwest zones through around 7-8 A.M. with additional development possible through the morning/early afternoon across the rest of the forecast area. Plentiful instability with CAPE values between 3000-4500 J/KG and increased 0-6 km shear on the order of 25-40 knots will certainly be supportive of severe storm development if convection moves/develops over our region late tonight into Saturday. Will opt to pull the Marginal Risk a little farther south/east through Saturday morning in our local graphics given short range guidance trends. Severe risk into Saturday afternoon remains conditional on convective evolution through Saturday morning, and will continue to assess this potential overnight after looking at newer available guidance. /21 && .PREV DISCUSSION... /issued 803 PM CDT Fri Jul 20 2018/ DISCUSSION...See updated information for land areas below. UPDATE...Have updated evening zone package to remove heat advisory headlines that expired at 7 pm this evening. No other updates at this time. /10 PREV DISCUSSION... /issued 635 PM CDT Fri Jul 20 2018/ DISCUSSION...Updated for latest aviation discussion below. AVIATION... 00Z issuance...VFR conditions forecast tonight over the coastal terminals. Light south to southwest winds this evening becoming more west late. /10 PREV DISCUSSION... /issued 414 PM CDT Fri Jul 20 2018/ NEAR TERM /Now Through Saturday/...Main impacts to affect the forecast area through Sat afternoon will be the chance for a few strong to possible severe thunderstorms moving into northern sections of the forecast area late tonight and early Sat, generally along and north of highway 84, and persistent heat index values ranging from 108 to 112 degrees. For tonight and early tomorrow thunderstorms will be moving southward towards the coast with the potential for strong gusty straightline winds...frequent cloud to ground lightning and very heavy rain beginning mostly after midnight tonight continuing into the mid morning hours. Most of the model guidance depict a well defined MCS forming over the TN River valley later this afternoon and into this evening pushing southward over northern sections of AL and MS late this evening, then further south through the mid morning hours. Thunderstorms should be on a weakening trend as they move southward overnight though with plenty of deep moisture and instability in place overnight this trend will have to be closely monitored. By Sat afternoon more showers and thunderstorms are expected to develop as the boundary layer becomes recharged from daytime heating. Gusty straightline winds...frequent cloud to ground lightning and very heavy rain will be likely with the stronger thunderstorms during the afternoon on Sat. The best chance for thunderstorm development on Sat will be generally east of the Mobile River including coastal areas and the near shore waters of Al and NWFL. There is plenty uncertainty on the coverage and timing with the development of thunderstorms tonight and on Sat possibly leading to more updates this evening and overnight. Day and nighttime temps will continue to be above seasonal norms combined with dewpt temps ranging from the middle 70s to near 80 for most locations. Heat index values ranging from 108 to 112 degrees F have been recorded in many locations over southeast MS and along the coast today and will likley continue in these through the weekend. As a result a Heat Advisory will continue over all areas of southeast MS and bordering counties in southwest Al through 7 pm tonight followed by another Heat Advisory from 10 am until 6 pm Sat mainly for all coastal counties of AL and NWFL along with Greene, Stone, George and Perry counties in southeast MS. 32/ee SHORT TERM /Saturday night Through Monday night/...The large upper high pressure system over the southern Great Plains will slowly retrograde westward over the Desert Southwest through the short term. An upper level ridge extending southeast from the center of the high over the northern Gulf of Mexico will shift south- southwest over the western and southern portions of the gulf by noon Monday while the center of a large upper low pressure system over the Ohio River Valley region drops south over the southeast states. The surface ridge across the Gulf of Mexico will migrate slowly southward slightly through the period, while a surface low reflected under the upper low across Ohio River Valley region also drops south across the southeast states. Isolated to low-end scattered showers and thunderstorms will develop Sunday afternoon east of the Alabama River as the upper low approaches, and likley remain dry to the west of the river. These showers and thunderstorms will then dissipate through early Sunday evening. Shower and thunderstorm coverage will increase on Monday, with scattered showers and thunderstorms east of the Alabama River, with isolated coverage to the west of the river. High temperatures on Sunday will reach the mid 90s with the very moist airmass still in place. As a result, heat indices on Sunday will reach 107 to 112 degrees across the southern portions of the forecast area, and 100 to 107 degrees across the north. Therefore, the Heat Advisory in effect across the southern portions of the forecast area on Saturday has been extended through Sunday afternoon. /22 LONG TERM /Tuesday Through Friday/...The upper low over the southeast states will persist through midweek, but gradually evolve into an open wave. This upper level weakness will then weaken through the remainder of the long term. The surface low reflected under the upper low across the deep south will also slowly weaken, follow by a surface ridge rebuilding across the northern Gulf of Mexico. Shower and thunderstorm coverage will increase on Tuesday, with isolated to scattered showers and thunderstorms continuing through Friday. The increased cloud cover and convection should knock afternoon temperatures and heat indices down a few degrees. /22 MARINE...Hazardous conditions for small craft can be expected late Sat through Sun evening in response to a strong pressure gradient setting up over the northern gulf waters. this pattern is from a persistent ridge of high pressure over the central and northern gulf combined with a weak frontal approaching from the north stalling near or just north of the coast by late Sun. Most of the model guidance moves the front offshore by early next week. 32/ee && .MOB WATCHES/WARNINGS/ADVISORIES... AL...Heat Advisory from 10 AM Saturday to 6 PM CDT Sunday for ALZ261>266. FL...Heat Advisory from 10 AM Saturday to 6 PM CDT Sunday for FLZ201>206. MS...Heat Advisory from 10 AM Saturday to 6 PM CDT Sunday for MSZ075- 076-078-079. GM...None. && $$ This product is also available on the web at:
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1105 PM CDT Fri Jul 20 2018 .SHORT TERM...(This evening through Saturday) Issued at 252 PM CDT Fri Jul 20 2018 Isolated showers are redeveloping this afternoon. Clearing skies and temperatures rising into the upper 70s/low 80s are building instability. Could see some of these showers develop into thunderstorms through early evening before losing instability around sunset. So far, lightning activity has been confined to northern Minnesota. Coverage is not expected to be particularly widespread, perhaps 30-40 percent. Widespread smoke across northwestern Minnesota associated with wildfires over southern Canada will drift south tonight. Visibilities range from 2 to 5 miles. The RAP smoke model maintains this plume overnight into southwest Minnesota, which seems reasonable with an inversion trapping the smoke near the surface and continued northerly flow. The MPCA has posted an Air Quality Alert for northwest and portions of west central/central Minnesota through mid morning Saturday before better mixing takes over. .LONG TERM...(Saturday night through Friday) Issued at 252 PM CDT Fri Jul 20 2018 Overall, models continue to support a cooling trend after the middle of next week as the mean wind in the boundary layer contributes to a more Canadian air mass regime. For the ladder part of the weekend, and into early next week, the anomalous upper low, which is currently located across the western Great Lakes, will drift southward and weaken over the next few days. This will keep deep tropical moisture limited to the far south in the extended period. The mean upper flow will also become stronger and westerly early next week as a storm system moves across southern Canada. Although PWATs do increase slightly as another weak cold front moves across the region Monday, most of the energy with this system will remain in Canada. Thus, any rainfall will be isolated or scattered in nature and no robust updrafts for strong storms. A more potent short wave, and a stronger jet streak, will move across the Upper Midwest the middle of next week. Instability will remain weak as another front passes through the region. However, with better jet energy, any thunderstorms could be capable of producing strong wind gusts. The end of next week can be characterized as cooler than normal as the mean upper flow remains northwest. This will likely mean highs near 80 and lows in the 60s. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1104 PM CDT Fri Jul 20 2018 Main concern now is how extensive does stratus get tonight. Beginning to see the first signs of this stratus showing up to the northeast of Mille Lacs. RAP/HRRR continue to show this stratus working toward southwest MN. NAM soundings are certainly moist in the low levels, but that moisture is relatively shallow, so it`s hard to say how widespread the stratus will become. At either rate, LAV continues to show best IFR/MVFR probs at AXN/STC/RWF, though MSP and MKT could get in on the fun as well. No rain Saturday, with morning stratus slowly lifting through the morning. Looks like cloudiest skies will be over MN, with mainly sunny skies over WI. KMSP...Still potential for 1k to 1.5k ft cigs to impact the airport between 10z and 16z Sat morning. Will have to watch how stratus to the northeast of Mille Lacs Lake evolves. /OUTLOOK FOR KMSP/ Sun...VFR. Wind NE 5-10 kts. Mon...VFR. Slight chc -TSRA. Wind vrbl becoming NW 5-10 kts. Tue...VFR. Wind W 5 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...BORGHOFF LONG TERM...JLT AVIATION...MPG
Area Forecast Discussion
National Weather Service Tucson AZ
900 PM MST Fri Jul 20 2018 .SYNOPSIS...Isolated to scattered thunderstorms will continue this tonight and again Saturday afternoon and evening. Then high pressure will strengthen over the region late this weekend into early next week resulting very little storm activity and much warmer temperatures. High temperatures Monday into Wednesday will be much warmer than normal and likely reaching record levels at some locations. && .DISCUSSION...Thunderstorms brought some quarter size hail to parts of Sierra Vista and Corona De Tucson this afternoon. The thunderstorm activity had diminished this evening, but another round of storms will be possible tonight. Latest radar and satellite imagery suggested that this next round was already starting to flare up across Cochise and Graham counties. The steering flow was from the east which will track storms westward toward the lower deserts tonight. Latest HRRR also supported the notion of more showers and thunderstorms overnight. Current forecast already conveyed this scenario of nighttime storms, so no updates necessary this evening. && .AVIATION...Valid through 22/06. ISOLD to SCT TSRA will continue well into this evening and potentially through 21/10Z before with cloud bases 8-10k ft AGL. Some clearing expected after 21/12Z then ISOLD-SCT TSRA After an active thunderstorm day for parts of southeast Arizona, especially around Sierra Vista and Corona De Tucson where several reports of quarter size hail were received.will redevelop again after 21/19Z east and south of KTUS. Outside of strong and erratic TSRA outflows, surface winds remain below 12 kts through the period. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Isolated to Scattered thunderstorms will continue into the overnight hours then fire up again east and south of Tucson Saturday afternoon, although they should be fewer in number. Upper level high pressure will build over the region significantly suppressing thunderstorms Sunday through Tuesday so they will be tough to come by at all outside of the White Mountains although dewpoints will remain at respectable levels. However, this high will bring near or record level heat to the area Monday through at least Tuesday. Later in the week the high shifts to the west allowing monsoon moisture to begin returning to the area. Winds typically light for mid-summer with the exception of strong gusty winds near thunderstorms. && .PREV DISCUSSION...On Saturday, we will gradually begin to transition to a less favorable thunderstorm environment thanks to upper level high pressure that will build westward from Texas this weekend. Still expecting some storms Saturday, just fewer in number and more limited to higher terrain east and south of Tucson. Also may end up with a fair amount of cloud cover through the morning which would hinder development. Sunday the high approaches and settles overhead Monday through Tuesday. Sunday there will be very limited convection then Monday and Tuesday will not likely see much of any development thanks to the subsidence and mid-level warming. That said, that warming will impact our temperatures significantly. Heights and temperatures 700mb and above are forecast to be at or above the 99th percentile for this time of year which translates to hot temperatures Monday, Tuesday and possibly Wednesday. Unlike June when dewpoints are typical very low they will be higher this event which will make it feel warmer yet. We already have an Heat Warning in effect and that looks great. There is some question for Wednesday as it will depend on how fast the monsoon moisture returns over the area behind the departing high. At a later time we may need to expand the warning into Wednesday at least for western parts of the area. By the end of the week temperatures should return to "normal" with moisture providing for some storms once again. && .TWC WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning from 10 AM Monday to 8 PM MST Tuesday for AZZ501>509. && $$ Visit us on Facebook...Twitter...YouTube...and at