Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/16/18

Area Forecast Discussion
National Weather Service Bismarck ND
1021 PM CDT Wed Aug 15 2018 .UPDATE... Issued at 959 PM CDT Wed Aug 15 2018 Little change with this update. The main challenge for tonight will be determining potential smoke impacts, especially to surface visibility on Thursday. It may be the case where smoke is quite thick aloft, while weak low level flow trajectories remain unfavorable to advect significant near surface smoke into western and central North Dakota. However, this is somewhat uncertain. UPDATE Issued at 640 PM CDT Wed Aug 15 2018 Did trend towards the lower edge of forecast guidance for low temperatures tonight given the dry airmass in place despite the weak return flow that is forecast. Widespread low temperatures in the lower 50s are forecast, closer to the bias corrected statistical guidance. Also added a mention of smoke to much of the west and the north for Thursday as the thick shield of smoke across north central Montana into Saskatchewan and Alberta may continue to propagate east-southeast downstream of the upper level ridge axis. This is depicted in the experimental HRRR and RAP smoke guidance. && .SHORT TERM...(This evening through Thursday) Issued at 303 PM CDT Wed Aug 15 2018 Water vapor imagery shows an upper-level low spinning over western SD this afternoon. Shower and thunderstorm activity associated with this low has stayed well off to our south, with surface high pressure and sunny skies entrenched over ND. With the high sliding off to the east tonight and warmer temperatures this afternoon, tonight should not be as cool as the previous two. The upper low will slowly drift eastward into Thursday as the next upper-level ridge begins to build over MT/WY. Gradual height rises will allow for slightly warmer temperatures on Thursday, with highs in the mid 80s to lower 90s. GOES-16 visible imagery shows widespread smoke over southern Alberta into southwest Saskatchewan. Some of this smoke may be transported into northern ND on Thursday, which is supported by the 12Z HRRR/RAP Smoke Models. Confidence is not high enough to add a smoke mention to the forecast at this time, but will continue to monitor. .LONG TERM...(Thursday night through Wednesday) Issued at 303 PM CDT Wed Aug 15 2018 The upper-level ridge will slide over the Northern Plains Thursday night into Friday. Some of the guidance is hinting at a weak disturbance moving through on Friday, but it`s tough to find low- level forcing/moisture to support any precipitation. A shortwave trough is forecast to move onto the Pacific Northwest coast on Friday, reaching the Northern Plains by Saturday evening while interacting with a northern stream trough and attendant surface cold front. This will give our area the best chance for widespread precipitation we have seen in quite some time, mostly from Saturday evening into Sunday afternoon. More than enough instability (around 2000 J/kg) will be in place for thunderstorms Saturday evening, and a few storms may become strong (Note: GFS surface dewpoints have consistently been too low - on the order of 10F - and therefore, its instability analysis is an outlier and should be ignored). Shear looks very limited though, so severe weather is not anticipated at this time. As for temperatures, trended toward the warmer side of guidance for both Friday and Saturday highs. With the cold front just making its way into western ND Saturday afternoon, think Saturday may actually be the warmest day for central parts of the state. However, Sunday will be much cooler as Canadian air begins to filter in behind the front. In addition, cloud cover may help in keeping temperatures down on Sunday. Cooler weather looks to continue through early next week as we remain under northwest flow aloft. Both the GFS and ECMWF resolve a disturbance or two passing through the region Monday through Wednesday, but there are timing and amplitude differences. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 959 PM CDT Wed Aug 15 2018 Smoke may increase across western and central North Dakota on Thursday, and introduced a smoke mention to the KISN/KDIK/KMOT TAFs for now. There is some uncertainty on how far south the smoke will reach and how low visibility may become. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...PA SHORT TERM...Hollan LONG TERM...Hollan AVIATION...PA
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
733 PM EDT Wed Aug 15 2018 .AVIATION... Arc of isolated showers lifting northward through Detroit terminals is along the 800-700mb warm front extension and deeper moisture axis. Showers will lift into an area of stronger midlevel subsidence and high static stability between 6.0 and 9.0 kft agl. Expectations are for this shower activity to dissipate this evening. Southeast Michigan will then see placement within a greater warm conveyor that will be east of a midlevel low pressure system lifting toward the state. Secondary moisture advection and strong convergence associated to low pressure system will impact the area for much of Thursday. Will likely see an increase in shower and thunderstorm activity after 10Z Thursday morning and persist in an isolated to scattered coverage through the early to middle afternoon. For now will just include shower mention and leave thunderstorms out of the forecast. Moderate potential will exist for some periods of IFR cig heights at the Detroit terminals between 10-18Z. For DTW...Best chance of heavy rain looks to be around 14-18Z though models have been shifting this window around. Thunderstorms are possible but not high enough confidence to include in the taf. .DTW THRESHOLD PROBABILITIES... * Low for thunderstorm through Thursday. * Medium for cigs aob 5000 feet 06-12z, high after 12z. && .PREV DISCUSSION... Issued at 346 PM EDT Wed Aug 15 2018 DISCUSSION... Upper-level ridging and dry conditions in the low to mid-levels (as noted by low RH 65% and mid RH 30% in the 12Z DTX sounding) have allowed dry conditions to persist throughout the morning and afternoon. High cirrus will continue to fill in throughout the evening, ahead of an approaching shortwave trough, with overcast low- level stratus filling in overnight as the low and mid-levels saturate. Attention will then turn to rain and thunderstorm chances which are expected to take place throughout Thursday as a shortwave trough and adjoining surface low pressure system pushes northeast across the CWA. Increased southwest gradient flow will usher in subtropical moisture into the region as noted by the latest 12Z GFS20 run, where PW values range between 1.80 - 2.00 inches between Thu 06 - 12Z. Latest NAM12 and RAP model suites also support PW values in this range, which would be near-record to record values according to the SPC sounding climatology page for DTX. Latest 12Z suites show axis of greatest moisture transport and leading edge of the LLJ to push into Ohio and perhaps the southern Metro region of Michigan between 06-12Z, which will be an area to focus on for initial heavy showers and thunderstorm development. Rain and thunderstorm chances will then expand across the CWA Thursday afternoon into the evening as low pressure pushes northeast across the state. In terms of coverage...Not expecting widespread coverage, but instead scattered as low pressure spins up showers and storms throughout the day. Copious amounts of moisture will remain in place as PW holds between 1.80 - 2.00 inches, which will translate to heavy downpours for showers and storms that develop. Due to sporadic coverage, went with 40 - 60 PoPs for bulk of the day. Severe weather threat remains low as CAPE, lapse rates, and bulk shear are lackluster. As the low pushes northeast Thursday night into Friday morning, northwest flow around the low will drag in a dry slot which will briefly diminish rain chances late Thursday into early Friday morning, especially closer to the Metro region as it will be further removed from the low. Rain and low thunder chances again increase late Friday morning into the afternoon as a PV anomaly over northern Illinois weakens and pushes northeast into SE MI. Otherwise, Friday will feel quite muggy as dewpoints rise into the mid to upper 60s, with temperatures capped in the lower 80s for a high. Rain chances are expected to end Friday afternoon into evening as the low moves into New England, allowing high pressure to settle in across the area from the north. A dry period from Saturday through Monday looks likely as heights slowly build aloft and weak high pressure fills in at the surface. Highs near normal and light winds will result in pleasant conditions for outdoor activities, though dew points in the lower 60s will keep a mugginess in the air. Next chance for precipitation comes late Monday into Tuesday. A potent shortwave trough is progged to track from the Rockies through the mid-Mississippi Valley and lift into the Great Lakes by early Tuesday. A second trough is advertised to dig in from the Canadian Prairie provinces later on Tuesday. Model guidance continues to diverge on the strength and positioning of the resultant surface feature. The ECMWF is still hinting at a sub-1000 mb surface low developing and tracking northeast through Lower Michigan while the GFS is currently advertising an elongated area of weaker low pressure tracking just east of us - still with plenty of precipitation on its western flank. Will continue to monitor trends in the interaction of these upper troughs, but for now Southeast Michigan can expect a decent chance of rainfall late Monday and through the day Tuesday. Highs will remain near normal, though potentially a few degrees cooler on Tuesday due to precipitation and cloud cover. High pressure will begin to build in on Wednesday and bring the return of quiet weather. MARINE... Stalled frontal boundary remains over northern Lake Huron this afternoon producing light winds over much of the lake. A low pressure system will be tracking northeast tonight and Thursday passing over the eastern Lakes late Thursday. Showers and thunderstorms will accompany the low tonight through Thursday night. Southerly winds ahead of the low and south of the trough, will become northerly across much of Lake Huron as the trough settles southward tonight. Winds will become northerly by Friday behind the low as it exits east but should remain below 20 knots keeping waves in check. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....CB DISCUSSION...AM/TF MARINE.......BT You can obtain your latest National Weather Service forecasts online at
National Weather Service Jackson KY
1019 PM EDT Wed Aug 15 2018 .UPDATE... Issued at 1019 PM EDT WED AUG 15 2018 As expected, upstream convection has weakened as the outflow has outrun the better radar returns. Based on present trends and latest hi-res model output, rest of the night is shaping up to be dry. Still lots of thinness in the clouds out there, so valley fog should develop as we head through the night, especially with dewpoint depressions already near zero in the valleys. UPDATE Issued at 757 PM EDT WED AUG 15 2018 Last of the showers starting to pull out of eastern Kentucky and dissipate as anticipated. This will provide a lull into the overnight hours. Clouds have thinned out quite a bit this evening and should allow some form of valley fog to develop overnight. Thus, will include that with this update. We are watching a line of storms crossing into central Kentucky, but this line should weaken as it tries to push east and outruns the better instability axis to our west. UPDATE Issued at 507 PM EDT WED AUG 15 2018 Updated to bring pops farther to the east as we have had shower activity along the trough axis shifting east across the area this evening. This should only affect the area over the next few hours before it dissipates or moves on out of the area. Quieter weather will be seen overnight and may look to add some valley fog pending the resulting cloud cover after the current activity moves out. Future update will tackle this potential. && .SHORT TERM...(This evening through Thursday night) Issued at 414 PM EDT WED AUG 15 2018 The current surface map shows high pressure moving off to the east through this evening. This has brought in southerly flow, leading to the development of a line of showers in central Kentucky early this afternoon that have progressed into eastern Kentucky. There is the possibility of a few thunderstorms through this evening as well, but instability is limited. Currently the line looks to be breaking up somewhat, but lightning has been detected near the Tennessee border. An upper level shortwave trough as well as a surface cold front will advance towards the Ohio Valley Thursday. This will bring likely chances of showers and also the potential for thunderstorms for all of eastern Kentucky. With the potential for heavy rainfall, there is a risk for flash flooding Thursday into Friday. Utilized the CONSShort and the HRRR as a baseline, along with current radar trends, for PoPs into this evening. Models are in good agreement with the overall pattern for the system Thursday into Friday. Stuck with the Blend`s timing and progression for this system. High temperatures will be in the mid to upper 80s and low temps will generally be around 70. .LONG TERM...(Friday through Wednesday) Issued at 401 PM EDT WED AUG 15 2018 The extended forecast begins on Friday with an active pattern expected with a chance of rainfall expected nearly everyday of the extended. On Friday, the day will begin with an approaching upper wave as a weakened surface cold front pushes southeast through the area. Increased moisture flow with high pressure to the east and southerly flow in place, will expect showers and thunderstorms to develop for the day Friday. Model soundings suggest a bit higher storm motion winds so any flood threat will result from training thunderstorm cells. With lingering high pressure over the southeastern CONUS the southern end of the front will stall over eastern Kentucky keeping the boundary over the eastern portion of the state through the weekend. Along with this setup, numerous disturbances will track across This combined with ample moisture everyday will keep the chance for precip in the area through the weekend. Depending on storm motion and the potential for training storms will drive the potential for flooding. Heading into Monday and Tuesday, another feature will follow behind the front from the weekend with once again again, good southerly flow and decent instability developing each afternoon. This is expected to be another situation with good afternoon convection once again bringing the chance for some heavy rainfall each afternoon. Overall, an active and wet period is expected through nearly the entire extended forecast period.&& .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 211 PM EDT WED AUG 15 2018 A line of showers in central Kentucky has progressed into the Cumberland Basin early this afternoon. It will make its way northeast across the Commonwealth through this evening and affect most TAF sites. However, SJS is not expected to be affected by these showers today. A few embedded thunderstorms are a possibility this afternoon/evening, but confidence is low in the amount of instability available. Therefore, have left mention of thunder out of the TAFs at this time. Winds will generally be 5 knots or less out of the south. However, winds will begin to increase with the approach of a cold front tomorrow afternoon. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 211 PM EDT WED AUG 15 2018 A line of showers in central Kentucky has progressed into the Cumberland Basin early this afternoon. It will make its way northeast across the Commonwealth through this evening and affect most TAF sites. However, SJS is not expected to be affected by these showers today. A few embedded thunderstorms are a possibility this afternoon/evening, but confidence is low in the amount of instability available. Therefore, have left mention of thunder out of the TAFs at this time. Winds will generally be 5 knots or less out of the south. However, winds will begin to increase with the approach of a cold front tomorrow afternoon. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...CGAL LONG TERM...SHALLENBERGER AVIATION...KAS
Area Forecast Discussion
National Weather Service Louisville KY
1103 PM EDT Wed Aug 15 2018 .Forecast Update... Issued at 1100 PM EDT Wed Aug 15 2018 Already seeing a second round of showers/storms forming as 30-40 knot low-level jet is cranking at the PAH/VWX/LVX VAD wind profiles. Decided to go ahead and fire up a small area Flash Flood Watch for the overnight...based partly on where the earlier rains fell as well as where the HRRR and 00Z NAM and ARW place new convection overnight. Issued at 1010 PM EDT Wed Aug 15 2018 Portions of southern Indiana and north central Kentucky received 0.5 to 1.5 inches of rain from storms this evening. The main forecast concern overnight is additional rainfall depicted by the NAM/HRRR. With PWATs rising to just over 2 inches and a good LLJ tonight through tomorrow morning, anticipate showers with embedded storms overnight to put down a good amount of rainfall likely in the same axis that received a good soaking this evening. Debated with surrounding offices on a Flash Flood Watch overnight but could not come to a consensus. Decided to pass along to the midnight shift that will evaluate 0Z data and determine our FF risk for the rest of tonight through tomorrow. && .Short Term...(This evening through Thursday) Issued at 305 PM EDT Wed Aug 15 2018 ...Get your umbrellas ready...very wet period ahead... Well...Lots of clouds keeping temps down today with upper low over Show Me State. Ahead of this system, there is a warm sector with dew points in the lower 70s. Currently, there is scattered shra and isolated tsra over S IN while we await for new convective development from NW TN to SW KY. This will spread into our area late this afternoon from strong sfc heating. Strong warm air advection pattern is setting up later today with low level jet of 30-40 kts. This will set up excellent efficient isentropic lift across area after 00z especially late evening into overnight. This will yield a high POP widespread rain event with isolated tsra with locally heavy rainfall, especially west of I-65. PWATs will increase to 1.75 to as high as 1.9 inches with the isentropic lift, so there will be pockets of heavy rain. The ground is fairly dry so not even thinking of any headlines at this juncture. However, locally embedded high efficiency convection could cause some isolated issues. The Weather Story messaging will keep talking about potential for locally heavy rainfall. High temp Thursday will be below normal with so much cloud cover. Lower 80s seems prudent especially west of I-65. .Long Term...(Thursday night through Wednesday) Issued at 300 PM EDT Wed Aug 15 2018 ...Multiple episodes of showers and storms to continue through the extended period, with a possible break on Sunday... Thursday night and Friday... As an initial shortwave trough aloft moves to our east Thursday night, a deeper trough will swing southeast through the mid and upper MS Valley. Residual showers and storms associated with the initial trough may move away or become fewer in number Friday evening. However, forcing ahead of the approaching trough combined with a continued moist air mass and suggestion of steepening mid- level lapse rates should allow for additional convection to form somewhere over the lower OH Valley (probably initially west of our area), then move east into at least parts of central KY and south- central IN late Thursday night/Friday morning. This activity could last into the daytime Friday, with any outflow boundaries dictating where additional cells may develop Friday afternoon and evening. These storms should produce high rainfall rates, so coupled with earlier rains and if cells repeat over the same areas, localized flood concerns could occur. Highs Friday will be in the lower and mid 80s, depending on amount of cloud cover. Friday night through Sunday... During this period, the trough aloft will move east and weaken but may be unable to create a "clean sweep" of the moisture and precip chances to our east. A weak surface boundary will work its way slowly south across the lower OH Valley Friday night and Saturday. Model soundings show that at least marginal to perhaps moderate instability will remain over much of the forecast area through at least Saturday. While areal coverage of precip will diminish, isolated to scattered showers and storms are still possible during the forecast period, especially over central KY. The frontal location suggests that precip chances may end over south-central IN Saturday night and Sunday, but with still a chance for isolated cells Sunday over central KY. Expect high temps Saturday and Sunday to range through the 80s. Monday through Wednesday... Yet another significant shortwave is forecast to dig southeast across the central U.S. Monday with southwest flow aloft developing over the OH Valley. Besides renewed instability, this system actually could have some deep-layered shear associated with it for some strong convection, at least to our west over parts of the mid MS and lower OH Valleys on Monday. Storms would then work into our forecast area late Monday/Monday night and could linger or redevelop under the upper trough on Tuesday. If the current forecast holds, drier, less humid air would spread into our area Tuesday night and Wednesday. && .Aviation...(00Z TAF Issuance) Issued at 805 PM EDT Wed Aug 15 2018 The main TAF concern will be multiple rounds of showers and storms as multiple upper level disturbances pass through the region ahead of an upper trough. SDF will be affected within the next hour with strong t-storms with gusts to 50+ mph possible and IFR conditions. After this storm passes SDF should see mainly showers with a few rumbles of thunder for the rest of the night like HNB. Showers and storms will be slow to arrive at BWG/LEX late tonight into tomorrow morning. Look for more rounds of showers and storms to affect all TAF sites throughout the day tomorrow. In addition, SSW winds of 8- 12kts will gust to around 18-22 kts tomorrow afternoon/evening. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...Flash Flood Watch through Thursday afternoon for INZ077>079-084- 089>092. KY...Flash Flood Watch through Thursday afternoon for KYZ023>025- 028>033. && $$ Update...RJS/AMS Short Term...JDG Long Term....TWF Aviation...AMS
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1102 PM CDT Wed Aug 15 2018 .UPDATE... Issued at 1055 PM CDT Wed Aug 15 2018 Updated to include 06z aviation discussion below. && .SHORT TERM...(This evening through Thursday) Issued at 412 PM CDT Wed Aug 15 2018 We have seen scattered thunderstorms develop this afternoon on the remnants of the cold front that moved into southern MN yesterday. Thunderstorms have basically been confined to where surface dewpoints have stayed up near or above the 70 degree mark. RAP analysis shows areas with 70 degree dewpoints have managed to develop 1500-2000 j/kg of MLCAPE. Given the weak surface flow, this zone of higher moisture/instability will not move much, which means the showers we are seeing develop this afternoon will basically stay where they are, along and south of a Mankato to Eau Claire line. For tonight, winds will be calm, which means we will have to chase radiational fog once again. The couple of factors that will drive the fog is the extent of cloud cover we see from the wave currently moving along the SD/Neb border, with the other being whether or not we have enough time to hit our cross-over temps. Looking at dewpoints this afternoon, cross-over temps will range from the upper 50s in central MN to the upper 60s from south central MN into central WI. CAMS and MOS guidance really favoring south central MN up into western WI and across central up into northeast MN as having the biggest threat for seeing fog. For now, have patchy/areas of fog mention in the grids, but would not be at all surprised if we ended up with a dense fog advisory for parts of the area tonight. Thursday, the upper low currently in SoDak will scoot across IA, so the greatest coverage in precip is expected to our south. However, with weak low level flow, we won`t see much of a change in the surface dewpoint pattern, which means where we are see scattered showers today will have the threat of a repeat performance Thursday. .LONG TERM...(Thursday night through Wednesday) Issued at 412 PM CDT Wed Aug 15 2018 The long term still features one good hope for widespread beneficial rains Sunday and Monday. We`ll also get a couple of more opportunities to touch 90 for a high Friday and Saturday, with highs falling back into the 70s with the rain and clouds Sunday and Monday. We`ll see northwest flow briefly behind this wave, with highs remaining around 80 as skies clear out going into the middle of next week. Only change to the forecast Friday and Saturday was to go above blended guidance for highs. As we have seen since the weekend, as the ground continues to dry out, we are getting more and more efficient at warming up on these mostly sunny days, which Friday and Saturday will certainly be. In fact, Friday and Saturday will offer the Twin Cities two more chances at hitting 90. Currently, MSP sits at 18 90+ days this summer. If we were to push the count to 20, it would be the first time we topped 20 90+ days in a summer since 2012 when we had 31. For Sunday and Monday, models appear to be honing in on a solution of bringing us our most significant rains on a more widespread basis since the 3rd and 4th. Where uncertainty comes in is this still looks to feature the phasing of a southern stream system with the northern stream, which this far out is always tricky to pin down the exact details on. At the moment, it is looking like the northern stream will be sending a cold front across NoDak Saturday, with rain moving into west central MN Saturday night. Sunday, an upper circulation coming out of the central Rockies will be moving across Iowa before getting swept into the northern stream Monday over the Great Lakes. As this wave is moving across IA, it will be deepening, with deformation to the northwest of the low strengthening. It`s the fgen associated with the deformation that will help force a prolonged light precip event across our area on Monday. Our PoPs could certainly be higher, though we`ve seen several for sure rain events 5 days out evaporate to almost nothing by the day of this month, so we were alright with sticking with the high chance/low likely pops SuperBlend gave us, even though what we are seeing now would suggest we could be higher with pops. Behind this system, we`ll see northwest flow develop, which will give us sun and mild temperatures Tuesday and Wednesday before we start warming again at the end of next week. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1055 PM CDT Wed Aug 15 2018 Mainly VFR conditions expected throughout this TAF set though there is decent potential for pre-dawn fog in eastern MN through western WI. Winds will likely go calm in these areas along with little to no dewpoint depressions, especially near spots which received rainfall. Have included/maintained fog mention for MSP southward and eastward with much lower chances west and north of MSP. No precipitation expected at any of the TAF sites. KMSP...Some potential for MVFR fog around time of the morning push but, at this point, am not expecting fog to reduce visibility less than 5SM. Upper level ceilings then expected through the middle portion of the day tomorrow before scattering out late. /OUTLOOK FOR KMSP/ Fri...VFR. Wind NW 5 kts. Sat...VFR. Wind S 5 kts. Sun...Chc -SHRA/-TSRA/MVFR afternoon on. Wind S 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ UPDATE...JPC SHORT TERM...MPG LONG TERM...MPG AVIATION...JPC
Area Forecast Discussion
National Weather Service Raleigh NC
947 PM EDT Wed Aug 15 2018 .SYNOPSIS... An upper-level ridge will extend into the region through Thursday, resulting in warmer weather with limited rain chances. A cold front will approach the region over the weekend resulting in a return to unsettled weather. && .NEAR TERM /TONIGHT/... As of 945 PM Wednesday... 00Z upr air data indicate a ridge at 500 mb has closed off over VA this evening. A weak shear axis stretching west to east over cntl NC separates this high from a pair of parent sub-tropical ridges centered over srn TX and Bermuda, respectively. A higher level/shallow perturbation, centered in WV satellite data over sern TN/nwrn GA, will drift esewd across the srn Appalachians and into w- cntl SC/ern GA by Thu morning. Given how shallow this feature is and that it will be moving into a region otherwise dominated by weak mid- upr level height rises, no appreciable lift or impact is expected ahead of this feature, aside from perhaps some enhancement of cirrus already streaming across the Carolinas. At the surface, a trough stretching from ern NC swwd across cntl SC and s-cntl GA was again analyzed as a (quasi-stationary) front at 22Z because of the 7-10 degree dewpoint difference across it, though it has again become less apparent in surface observational data since that time owing to both nocturnal surface dewpoint recovery and the inland retreat of the sea breeze. The boundary was analyzed as a warm front from cntl GA nwwd across cntl TN and w-cntl KY, where it intersected composite outflow/ongoing convection. Low level convergence along the front and nearby outflow --in the same areas as last evening, from the NC srn Piedmont enewd across the Sandhills and srn-cntl Coastal Plain-- and amidst ~1000-1500 J/kg of MLCAPE per 00Z RAOB data at MHX (1000 J/kg) and CHS (1900 J/kg), will favor continued isolated to widely scattered shower development until around midnight, after which time nocturnal cooling and related weakening CAPE and strengthening CINH should become too great to overcome, in the absence of any larger-scale support for lift. Considerable high cloudiness may keep temperatures from reaching full radiational cooling potential and likewise limit fog development. However, recent HRRR runs and the 21Z SREF both favor the Sandhills and Coastal Plain for any such fog or low stratus development early Thu morning; which seems reasonable given that will be where moisture/convergence will be maximized near the front once again. Lows are expected to range from mid-upr 60s over the nrn Piedmont to lwr 70s along and southeast of the front. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 315 PM Wednesday... Bermuda high pressure will gradually build westward into the SE US Thu and Thu night. The rising mid/upper level heights and associated subsidence will limit convective development. Still, a persistent low level trough may provide enough of a focus for moisture to pool to permit an isolated shower or two to develop. This threat appears greatest across our southern counties. Overall, most locations will remain dry. The subsidence aloft will warm the atmosphere, leading to afternoon temperatures a couple of degrees warmer than this afternoon. This will yield high temperatures in the low and mid 90s. With sfc dewpoints in the upper 60s to around 70, heat indices will be well into the 90s, approaching 100 degrees across portions of the Sandhills and Coastal Plain. Isolated convection will dissipate with loss of heating, leaving in their wake partly cloudy skies. Dewpoints will be inching upward as the low level flow gradually increases from the south. Overnight temperatures, in turn, will be a tad warmer, ranging between 70-75. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... As of 210 PM Wednesday... After a few days of relatively quiet and inactive weather, the weather pattern will become increasingly unsettled into the weekend. The upper-level ridge across the sub-tropical Atlantic shifts south slightly as troughing over the upper Midwest on Friday shifts east. A positively tilted, sheared upper trough will extend from the Northeast down across the Appalachians on Saturday and then shift toward the coast on Sunday. An associated cold front stretching from the New England States into the OH valley on Saturday will drop into the Mid-Atlantic on Sunday. Convection should be widely scattered on Friday but as the upper-level trough approaches on Saturday and shifts overhead on Sunday, the pattern will support greater than typical chances of mainly afternoon and evening showers and thunderstorms over the weekend. The flow aloft strengthens on Saturday with 0-6km bulk shear values ranging near 20kts which could support stronger and more organized storms. Additionally, precipitable water values will approach 2 inches on Saturday and increase further on Sunday, supporting convection with locally heavy rain. Max temperatures should be the greatest on Friday with more limited storm and cloud coverage with morning low-level thickness values in the 1415-1420m range with highs ranging from 89 to 94. Highs will relax into the 87 to 92 range on Saturday and the 85 to 90 range on Sunday with morning lows in the 68 to 75 range each day. A transient short wave ridge arrives on Monday in between the departing trough off the coast and an approaching trough across the mid-Mississippi Valley. In addition, the stalled front near the NC/VA border should lift north which should result in more widely scattered convection. As the upper-trough sharpens and the associated cold front approaches late Tuesday into Wednesday, shower and thunderstorm chances will once again increase. Highs will range in the upper 80s to lower 90s with lows within a few degrees of 70 each day. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... As of 810 PM Wednesday... VFR conditions are highly likely at all locations through at least 07z tonight. Showers will continue near FAY for another hour or so (until 01z or 02z), and RWI may see a brief sprinkle during this time, but VFR conditions should be maintained. After 07z, areas along and east of a weak surface trough may see a period of MVFR vsbys in light fog, with FAY and RWI the most likely to be prevailing MVFR 08z-13z. VFR conditions will then return at all locations, and persist through the end of the TAF valid period. FAY and perhaps RWI may see another quick shower late Thu (20z-00z). Looking beyond 00z Fri, apart from a chance of MVFR fog 08z-13z Fri morning, VFR conditions will likely hold through Fri, although there will be a better chance of showers/storms Fri afternoon as compared to today/Thu. The shower/storm chance will extend through Fri night and Sat, with possible sub-VFR conditions, including early-morning fog Sat. Greater-than-usual shower/storm coverage is expected Sat through Mon, with a higher risk of sub-VFR conditions, as deep moisture returns to the area. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Blaes NEAR TERM...MWS SHORT TERM...WSS LONG TERM...Blaes AVIATION...Hartfield
Area Forecast Discussion
National Weather Service Tucson AZ
131 PM MST Wed Aug 15 2018 .SYNOPSIS...A moist atmosphere will result in scattered to numerous showers with embedded thunderstorms through Thursday along with cooler temperatures. A fairly typical monsoon pattern is expected this weekend into early next week with temperatures near to slightly above normal. && .DISCUSSION...It;s quite moist out there today with PWAT values ranging from 1.25 inches for eastern areas to 1.75 inches across the western deserts. Latest visible satellite imagery shows the leftover MCV from convection overnight over western Pima County pushing northward. Meanwhile, there a mid/upper level inverted trough is also present across southwest Arizona as well. On the eastern flank of the inverted trough we`ve seen considerable shower activity primarily across far eastern Pima County into western Cochise County. While the showers have been persistent most locales have seen less than 0.25" over the last 6 hours with just some isolated higher amounts. The atmosphere is largely worked over and thus limiting surface based convection across the Tucson Metro area, but the same can`t be said closer to the international border of Santa Cruz and Cochise counties where showers and thunderstorms have been developing over the past couple of hours. Latest runs of the HRRR and the 15Z UOFA WRF-RR seem to have the best handle on what is a complex situation across the region. We expect that the shower activity across eastern Pima County will generally decrease this afternoon but renewed scattered shower and thunderstorm development will continue especially south and east of Tucson. The main concern today given the very moist atmosphere is heavy rainfall and flooding issues, especially for areas that got hit with heavier rain last night. Shower activity should generally diminish this evening through the overnight but with this much moisture we do tend to lose some of the diurnal characteristics of the precipitation. A similar setup is on the table for Thursday with deep moisture remaining across southeast Arizona but with very weak southerly flow as the mid level high is just east of the area. Much will depend on how much solar insolation there is on Thursday but the potential will once again exist for scattered to numerous thunderstorms with locally heavy rain. The storms may tend to favor the higher terrain given the slow steering flow. Thereafter, deep moisture will remain on Friday as the flow becomes a bit more northeasterly. The mid/upper level high will reconsolidate to our northwest this weekend with a northeasterly flow persisting Saturday. There is some indication that moisture will be lessening as early as Saturday but in particular on Sunday. While this won`t shut the monsoon down, it will keep the best chances of precipitation from Tucson south and eastward. By early next week, the mid/upper level high will setup across northern New Mexico into Arizona with a more easterly steering flow. Perhaps some increased moisture around Monday and Tuesday but then a possible downward trend in activity as the high shifts more overhead. Still lots of uncertainty that far out with the bottomline being some thunderstorm chances everyday in at least portions of southeast Arizona through the forecast period. Temperatures will be below normal through Thursday before warming up and being near to even slightly above normal levels Friday into early next week. && .AVIATION...Valid through 17/00Z. Isolated to scattered -SHRA/-TSRA will continue through the evening hours just east of KTUS and to the south along the international border. Storms will start to dissipate around 16/04Z. Isolated to scattered -SHRA/-TSRA will again be possible tomorrow afternoon from Tucson eastward. Brief MVFR conditions possible with the -TSRA, otherwise SCT-BKN cloud bases generally 8-12k ft AGL this evening and tomorrow afternoon. Tonight expect SCT-BKN clouds AOA 20k ft AGL from leftover debris clouds. Outside of thunderstorm gusts, expect SFC winds mainly less than 12 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...The pattern is favorable for scattered showers and thunderstorms into this weekend, but there are hints of drier conditions by Sunday. Near or slightly below normal temperatures will continue through the forecast period. 20-ft winds will be terrain driven at less than 15 mph, except for in and around thunderstorms where strong outflows may occur. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ PUBLIC...Lader AVIATION/FIRE WEATHER...Hardin Visit us on Facebook...Twitter...YouTube...and at