Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/04/17


Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1147 PM EDT Thu Aug 3 2017 .AVIATION... The next round of thunderstorms is lifting into SW Lower Mi in advance of a mid level cold pool associated with an upper low across the western Great Lakes. These storms are expected to undergo at least some slight weakening as they rotate into Se Mi (06Z to 09Z time frame) where the available instability will be less. There is some question as to how much this region of convection will fill in farther north, raising some doubt as to whether or not FNT and MBS will see any convection. An associated cold front will push through around 12Z. Increasing low level moisture will support some MVFR based strato cu. Increasing post frontal mixing depths will result in gusty SSW winds by late Fri morning, persisting through the afternoon. For DTW...The cluster of storms across far Sw Lower Mi and NW Indiana should track across metro Detroit during the first couple hours of the TAF period. Although some weakening is expected, the current radar suggests they will hold together into metro Detroit, arriving around or shortly after TAF issuance. //DTW THRESHOLD PROBABILITIES... * Low in ceilings at or below 5000 ft tonight. Moderate on Friday. * Moderate in thunderstorms early this morning. && .PREV DISCUSSION... Issued at 913 PM EDT Thu Aug 3 2017 UPDATE... A region of mid level subsidence/anticyclonic flow has emerged in the wake of the earlier convection. This will suppress additional convection through the next several hours over most of the forecast area. Additional thunderstorms are located across far ern Wisconsin and Lake Michigan along the lead edge of the mid level cold pool. This convection is expected to track across Se Mi overnight as the upper low rotates across nrn Wisconsin. The latest CAMs continue to suggest this convection will weaken as it head into Se Mi, with some solutions actually suggesting it falling apart completely. This remains very much in line with the thoughts in the earlier forecast discussion. A forecast update was already issued simply to lower the chances of convection through the remainder of the evening. PREV DISCUSSION... Issued at 400 PM EDT Thu Aug 3 2017 DISCUSSION... Hefty convective potential and severe weather remains a concern for the late afternoon through evening. The early to mid afternoon convection has struggled to make the most of surface based CAPE around 2500 J/kg and 100 mb MLCAPE in the 1500-2000 J/kg range mainly due to the lack of a good wind shear profile. Upstream convection over SW lower MI, northern IN, and points west is expected to develop eastward through the warm sector and along the warm front that will be making a stronger northward move as low pressure approaches Lake Michigan. The upper wave and associated stronger wind field aloft will also be moving closer which will provide a modest increase in the wind profile. The RAP component in the hourly mesoanalysis indicates 0-6 km shear near 30 knots will be reachable. Combine that with sfc-3 km helicity in the 100-150 m2/s2 and the CAPE values mentioned above for convection to possibly organize supercell modes through the peak heating cycle. Storms with large hail and damaging wind remain possible over all of SE MI while the I-69 corridor northward will be the primary area affected by the northward moving warm front and supercell/tornado possibilities. Storms developing over the MS valley at press time represent round 2 of storms expected to move through lower MI overnight, along and ahead of the cold front. The 3 km NAM has the most aggressive solution and maintains a broken line of storms through SW lower MI while CAPE remains surface based around 1500 J/kg. It then depicts a weakening trend and some reduction in areal coverage overnight as the band moves through SE MI during the diurnal minimum. Considering the moderate forcing associated with the front/low pressure system and the potential for lingering elevated instability, expect numerous coverage of showers and scattered thunderstorms with not much severe potential. Forecast concerns Friday are limited to gusty southwest wind post front, especially in the dry slot of the system as low level cold advection combines with daytime heating to build the mixed layer. The result will be wind gusts around 30 mph into early evening. This will be followed by the trowal/deformation band of showers projected to rotate through lower MI Friday night with greater coverage toward the Tri Cities and northern Thumb. The system remains progressive enough to exit eastward by Saturday in favor of weak high pressure that will salvage one day of the weekend. The region will remain in longwave troughing to finish the weekend and start off next week as an associated surface low also treks across the Ohio Valley. This will continue to bring chances for unsettled weather as highs remain in the 70 degree range. By Tuesday, conditions will dry out as weak ridging and surface high pressure move in behind the departing low. Temperatures moderate back into the 80s to round of the extended forecast period. MARINE... A warm front will be lifting north over southern Lake Huron this afternoon and evening. Winds vary relative to the front, with modest northeasterly winds on the north side and southerly winds on the south. Unstable airmass with the front will support thunderstorm chances through the evening hours. Low pressure lifting northeast through the western Great Lakes tonight will pull a strong cold front through the eastern Lakes on Friday. Another round of thunderstorms may accompany the front. In addition, winds will increase behind the front while becoming southwesterly with gusts approaching 30 knots. This may necessitate small craft advisories for all nearshore zones. A period of higher west to northwest winds may also accompany the passage of the strong low pressure Friday night and early Saturday. Gusts may reach gale force over much of the Lake Huron Basin during this period. HYDROLOGY... Scattered thunderstorms will continue to develop through the afternoon and evening hours as a warm front lifts north through the area. A second round of storms will then be possible late tonight into Friday morning as a cold front sweeps through the area. Rainfall totals will vary greatly across the region given the scattered nature of any development. Higher amounts in excess of 2 inches will be possible on a localized basis within any heavier thunderstorms in part due to storms moving very slowly. This could result in significant runoff and some flooding, particularly within urbanized and poor drainage areas. The passage of the cold front on Friday will bring an end to the showers and storms. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Gale Watch from late Friday night through Saturday evening for LHZ361>363-462>464. Small Craft Advisory from noon Friday to 6 PM EDT Saturday for LHZ421-422-441>443. Lake St Clair...Small Craft Advisory from noon Friday to midnight EDT Friday night for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory from noon Friday to midnight EDT Friday night for LEZ444. && $$ AVIATION.....SC UPDATE.......SC DISCUSSION...BT/SP MARINE.......DRK HYDROLOGY....DRK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1042 PM EDT Thu Aug 3 2017 .SYNOPSIS... A cold front will move in from the northwest Friday night and become stationary west to east across our region this weekend. Low pressure will move northeast from Texas late Sunday and pull the front northward as a warm front into Monday. As this low pressure moves off the New England coast, the trailing cold front will become stationary again across the region into mid week. The next low pressure system and associated front moves closer to our region later in the week. && .NEAR TERM /THROUGH FRIDAY/... As of 1040 PM EDT: As expected, radars to the southwest are showing diminishing late evening returns on the upstream precipitation over central GA as the activity moves into less unstable air over NE GA. Still cannot rule out a stray shower over the piedmont overnight, but the better moisture through daybreak Friday should pass mainly southeast of our piedmont zones. The current temperature forecast appears on track, with high clouds slowly thinning from the west, but with mid clouds returning from the south late tonight. Otherwise, the upper trough will sharpen during the period, as strong short wave energy progresses across the Great Lakes. This will send a weak front into our area from the west by the end of the day tomorrow. With moist SW flow becoming established east of the frontal boundary through tomorrow afternoon, and the cirrus shield finally shifting east of the area, the models develop some respectable instability across the forecast area Friday afternoon. We should see scattered afternoon convection develop across the usual high terrain spots, while additional convection could fire along cloudy/clear differential heating boundaries near our southern and eastern zones. Additional pre-frontal scattered convection, or even clusters of convection may also move into the area from East TN by the end of the day. Pops will be advertised in the 30-50% range across much of the area, with some high terrain locations near the TN border seeing likely by late afternoon. Forecast max temps fall just short of climo. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... As of 215 PM EDT Thursday: A sfc cold front should push into the NC Mountains Friday evening, and may stall along the Blue Ridge until after daybreak Saturday. From there, the operational models seem to be trending toward pushing the front a little further south into the Midlands by Saturday AFTN, before stalling. convection along/ahead of the front should gradually wane, but PoPs don`t completely cut off, due to the front in the area Friday night. With the front a little to the south, Saturday may be largely dry for most of the area, except for the southern Upstate and Upper Savannah Valley. However, I only blended in the new guidance, so the fcst still features slight CHC to CHC PoP everywhere in the CWFA. A small severe threat may linger Friday evening, as convection may be quasi-organized along the front. But otherwise, there doesn`t look to be enough overlap of bulk shear and high CAPE for severe weather thru Saturday evening. Temps will be near normal Friday night, and slightly below normal Saturday. For Saturday night thru Sunday, upper level flow becomes quasi-zonal with an impulse streaming thru the Central Plains to the mid-MS Valley. This wave will back the lower and mid-level flow atop the CWFA, and bring moisture and instability back into the area. I don`t know if I`d call it a warm front, but in any case, the stalled frontal zone will lift back north slightly by Sunday morning. Models are in good agreement on better instability and more widespread convection across the area. Shear will remain weak, so severe threat should be low. Temps will continue to show less diurnal range than climo due to the unsettled weather. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 155 PM EDT Thursday: The medium range period begins Sunday evening with our west to east oriented stationary front beginning to move north as a warm front. This is in response to low pressure moving northeast from Texas pulling the front north and with a trailing cold front which will approach our region from the northwest late Monday. This scenario will enhance our POPs for late Monday and could result in a few severe storms, especially if some period of solar heating ahead of the approaching cold front occurs. The coverage of strong to severe storms will have much to do with the timing of the front. Models show good moisture advection along and ahead of the frontal zone with Precipitable Water values on the GFS around 2 inches and even above south of I-85. The current ECMWF has the front arriving in time for late Monday solar heating while the GFS has the front arriving early Tuesday. As the low pressure moves to the New England coast Monday night or Tuesday, the front eventually lays out across our area becoming stationary into Wednesday. PWat values remain high and peaking again above 2 inches south of I-85 late Wednesday and Thursday as the next northern wave in the 500mb flow passes just north of the Great Lakes. The high PWats and potential training of convection along the stationary front will present hydro concerns in the upcoming week. Surface dew points across the foothills and piedmont late Monday and again late Wednesday and Thursday will be 70 or above. Max temperatures 2 to 5 degrees below normal and Min Temperatures 2 to 3 degrees above normal due to the extensive cloud cover. On the GFS beyond the current forecast shows a hurricane Sunday morning August 13 between the Bahamas and Bermuda. The trough over the Eastern part of the nation would steer it to go between Bermuda and the Carolinas then away from Eastern Seaboard. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... At KCLT and elsewhere: Another round of fog/low stratus in the mtn valleys around KAVL Fri morning appears possible, although signals are mixed with the RAP rather bullish while the MOS sources much less so. Will feature a fairly solid window of IFR fog and stratus at KAVL given recent history at the site. Otherwise, any showers encroaching from the south overnight should pass mainly by to the southeast of the terminal forecast area. Some models also hint at low stratus for southern and eastern piedmont sections, and will feature SCT010 at KCLT in a nod in that direction, but confidence is too low for restrictions at present. Lower to mid clouds will thicken up through the day on Friday ahead of the approaching front, and convective chances will ramp up from the west during the afternoon hours. PROB30 throughout appears warranted mainly after 17Z west and 18Z east. Winds should generally be southerly, with some low end gusts across the SC sites during the afternoon hours. Outlook: Showers and thunderstorms may continue across the region into Friday night as a cold front moves in from the northwest before stalling over the lower piedmont. Moisture returning over the front may permit convection to return through the late weekend and then conditions will become quite unsettled through the middle of next week. Restrictions will be possible with any showers or thunderstorms and fog and low clouds will be possible each morning around daybreak, mainly in the mtn valleys, but also in areas that receive heavy rainfall the day before. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% Low 29% High 81% High 100% KHKY High 100% High 100% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 98% High 80% 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: www.weather.gov/gsp/aviation && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...HG/JDL SHORT TERM...ARK LONG TERM...DEO AVIATION...HG/JDL
Area Forecast Discussion
National Weather Service Wilmington OH
1019 PM EDT Thu Aug 3 2017 .SYNOPSIS... A cold front will approach the region tonight and move through on Friday. Dry conditions and high pressure will then move into the region for Friday night into Saturday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Surface cold front is currently located across central Illinois this evening and has made good progress over the last couple of hours. Evening showers and thunderstorms triggered by daytime heating have slowly decreased in coverage with this trend forecast to continue. There are some pockets of PV racing northeast ahead of a cutoff low approaching Wisconsin. High res models have been inconsistent with this very early morning precipitation so for the most part have left the area dry. Friday morning between 4 and 6 AM the prefrontal trough will be approaching the area from the west. The upper level support looks promising but with the passage at daybreak the instability is paltry. Even with PWATs around 1.55" high res models only show a thin line Friday morning. The prefrontal trough axis will then push east towards Wilmington between 9 and 11am. The prefrontal then looks to clear the CWA early Friday afternoon. The surface cold front will then push through right behind the trough axis. The latest runs of the HRRR try to reignite convection along the front. The ARW and NMM aren`t this aggressive. Most likely convection will get going across our far eastern CWA border and then continue to push east. Behind the cold front PWATs will plunge to ~0.65" (1 to 2 standardized anomalies below normal for this time of year). Winds will also be breezy with gusts up to 20kts possible (GFS forecast soundings slightly more aggressive with wind gusts than NAM forecast soundings). Temperatures will hold steady and then slowly fall behind the front with clouds being slow to clear. Prev Discussion-> Isolated to scattered showers and thunderstorms will be in place this afternoon and into the early evening hours due to daytime heating and instability. An isolated damaging wind gust cannot be ruled out, however not expecting more than an isolated severe potential. Activity will briefly taper off later this evening, however additional shower and thunderstorm activity will begin to move into the region late in the overnight hours in advance of a cold front. Temperatures will only drop into the middle to upper 60s overnight with some cloud cover through the overnight hours. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... A cold front will move through the forecast area on Friday. Expect the greatest coverage of thunderstorm activity across eastern portions of the area where there will be more daytime heating. This will also be the area that has a higher potential for damaging wind gusts with the storms. Will continue to have severe mention in the hazardous weather outlook. After this feature moves through expect cooler and drier conditions for Friday night. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Surface high pressure will build in across the area through the day on Saturday. This will be accompanied by a cooler and drier airmass with daytime highs five degrees or so below normal, generally in the mid to upper 70s. The surface high will shift off to the east through the day on Sunday and with progressive zonal flow aloft, some embedded mid level energy will push east across the region. There are still some timing differences between the models with these features with the 12Z ECMWF still the fastest bringing pcpn into our area. Will therefore go ahead and allow for chance pops to spread in from the west through the day on Sunday. Instability is pretty marginal so would expect mainly showers with perhaps some embedded thunder. Temperatures on Sunday will be dependent on how fast the clouds and any pcpn moves in but for now will keep highs in the 75 to 80 degree range. A stronger short wave will approach from the west Sunday night into Monday with an associated surface wave riding up through the Ohio Valley. This will lead to increasing chances of pcpn for Sunday night and continuing into Monday. Instability remains fairly negligible Sunday night but is forecast to increase some through the day on Monday. Expect highs on Monday again in the 75 to 80 degree range. We will then remain in a fairly progressive westerly upper level flow pattern through the mid to late part of next week. There are some model differences through mid week with the GFS trying to bring a surface wave up across the Appalachians. This could eventually lead to a chance of showers toward mid week but will trend toward the drier ECMWF at this point. Highs will trend back up into the upper 70s to lower 80s through the end of the period. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Isolated convection has formed thanks to daytime heating this afternoon, but the main show for convection has remained in Indiana towards the better upper level diffluence and divergence. Activity will diminish later this evening as daytime heating is lost. Overnight into Friday morning a potent upper level low will push east towards Michigan. As this happens high res models are trying to show some midlevel energy pulling northeast out in front. Not surprisingly high res models try and develop some light showers after midnight Friday morning and quickly pull them northeast. For now have left the mention of precipitation out of the TAFs until the prefrontal trough arrives later Friday morning given low confidence on location/ occurrence. Friday morning between 5 and 7 AM the prefrontal trough will push towards the OH/ IN state line. Most likely a weak band of showers will be present with this trough axis. Latest runs of the HRRR and RAP are not impressive to say the least. Thunder will be possible as elevated instability remains, but think the chance is low at this time. Friday morning (or before noon) the RAP and HRRR actually have the prefrontal trough approaching KCMH/ KLCK. Behind the prefrontal trough winds will veer to the SSW and the chance of thunder will begin to greatly diminish. The cold front will be right behind the trough axis and usher in much drier air (PWATs falling from ~1.5" to 0.75") and breezy conditions. GFS forecast soundings are indicating wind gusts up to 20kts possible while the NAM is slightly lower (via momentum transfer). The other concern will be MVFR cigs as the upper level low pushes east across Michigan (moisture being trapped underneath the inversion). Overall thinking is that most TAF sites will remain VFR with the exception being the northern TAF sites. Even at the northern TAF sites confidence is only moderate. Friday evening surface high pressure will slowly build in from the west with winds being slower than normal to decouple (due to the pressure gradient). Clouds will also slowly decrease in coverage. OUTLOOK...Showers and isolated thunderstorms are possible Sunday night into Monday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines/Novak NEAR TERM...Haines/Novak SHORT TERM...Novak LONG TERM...JGL AVIATION...Haines
Area Forecast Discussion
National Weather Service Lincoln IL
839 PM CDT Thu Aug 3 2017 .UPDATE... Issued at 839 PM CDT Thu Aug 3 2017 Cold front progressing across central IL this evening is currently aligned from near Jacksonville to Pontiac, moving steadily eastward. Ahead of the front, MLCAPE values up to around 2000 J/KG, and these are steadily diminishing from a peak of 2500-3000 J/KG late this afternoon. As a result, thunderstorm activity is diminishing as well, with severe weather likelihood diminishing. Behind the front, precipitation and thunderstorms ending, with a period of clearing skies moving in. Expect the front to pass I-57 by midnight, and move into Indiana a few hours later. Only minimal updates needed for clearing behind the front this evening. Much cooler and drier air behind the front should result in lows dropping into the mid and upper 50s across central IL, with low 60s south of I-70. && .SHORT TERM...(This evening through Friday) ISSUED AT 259 PM CDT Thu Aug 3 2017 Pre-frontal convection has been tracking across central Illinois this afternoon, aided by surface based CAPE`s reaching 3500 J/kg. The storms are still ahead of the better shear though, and have mainly been responsible for heavy rain and some winds to around 40 mph or so. Main cold front is still back across eastern Iowa into west central Missouri, with a sizable gap in convection along it. In terms of any threat of strong storms, what`s going on now may actually be the main show, as the higher resolution models suggest more of a disorganized line ahead of the front this evening. The NAM and ARW suggest the rain should be done as early as midnight in our CWA, while the HRRR, GFS and RAP linger it a bit longer in the far southeast. In the forecast, rain will be gone from the Illinois River valley by about 10 pm, and will limit any post- midnight rain to areas along and east of I-57. Strong upper low currently over north central Minnesota will swing eastward toward eastern Lake Superior by Friday afternoon. Associated stratocumulus deck is expected to linger across areas northeast of I-74 into the afternoon hours, which should help keep high temperatures down, close to 70 degrees. Some afternoon sunshine further west and a warming air mass behind the main trough will allow for some warmer conditions, but still only in the mid 70s. .LONG TERM...(Friday night through Thursday) ISSUED AT 259 PM CDT Thu Aug 3 2017 Main focus in this period will be with timing of rain trends Saturday night into Monday night, as a strong west-east upper trough near the Canadian border swings southeast toward the mid- Mississippi Valley. The ECMWF and NAM models develop an MCS west of the Mississippi Saturday afternoon and roll it into much of the CWA as early as Saturday evening, associated with a leading shortwave, while the GFS is weaker and keeps us dry most of the night. Didn`t go quite as fast with the rain, but have brought in healthy chance PoP`s in most areas by midnight, with likely PoP`s in the far southwest after midnight Saturday night. As this MCS tracks toward southern Illinois, the northwest CWA will see temperatures kept down a fair amount with a northeast flow, mainly lower 70s for Sunday. Areas further south will see periods of rain and a few storms as the system passes, largely out of the area by late Sunday evening as the cold front exits the area. Beyond that, while the ECMWF would suggest dry conditions with high pressure building eastward, the arrival of the earlier mentioned trough axis would support at least chance PoP`s on Monday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 659 PM CDT Thu Aug 3 2017 A cold front just west of the Illinois River at 00Z will push eastward across central IL through the evening, reaching Indiana shortly after 06Z. A broken line of thunderstorms will accompany the frontal passage as well as some isolated thunderstorms well ahead of the front. Most thunderstorm activity is expected to pass through the central IL terminals by 04Z. A region of low cloud cover will pass over the area Friday morning, promoting a period of MVFR cigs from KPIA-KDEC northeastward starting around 12Z. Conditions expected to return to VFR after 18-20Z. Winds S 6-12 kts this evening, shifting to W-NW behind the cold front this evening, and increasing to around 15 kts with gusts to 25 kts by 18Z. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...37 SHORT TERM...Geelhart LONG TERM...Geelhart AVIATION...37
Area Forecast Discussion
National Weather Service Northern Indiana
1026 PM EDT Thu Aug 3 2017 .SYNOPSIS... Issued at 345 PM EDT Thu Aug 3 2017 Thunderstorms will continue across the area through early tonight ahead of a strong cold front and associated vigorous upper level system. Much cooler weather will arrive Friday with highs only in the 60s over northwest Indiana and the lower 70s over most of northwest Ohio. The cool air will continue over the area through Tuesday with highs in the 70s. && .UPDATE... Issued at 1020 PM EDT Thu Aug 3 2017 Round 1 of storms departing to the east with next batch already on our doorstep with scattered storms in far NW parts of the area, extending back to the southwest. Few strong to locally severe storms were noted earlier back over Illinois but storms have generally congealed and are tracking ENE. Unsure how much more coverage will change in the coming hours with HRRR suggesting more expansion and some intensification possible. Still some bowing segments noted from time to time but one of the better looking ones that passed through Kankakee, IL did little more than around 35 mph winds. Will hold with 50 pops as the storms move through and go with sct wording for the time being with the bulk of the convection moving through in the span of an hour or 2 tops. Other change to grids was to increase winds into tomorrow over land and lake and move up start of small craft advisory and beach hazards a few hours based on faster arrival of winds. && .SHORT TERM...(This Evening through Friday) Issued at 342 PM EDT Thu Aug 3 2017 Storms were continuing to develop upstream over Illinois ahead of an upper level TROF and an associated cold front. Mid afternoon surface based CAPEs had risen above 4000 J/Kg per SPC meso analysis over Central Illinois where storms were becoming better organized. Mid level lapse rates were still quite stable and should limit overall storm development. Expect marginally severe storms with hail to near 1 inch and wind gusts approaching 58 mph mainly west of highway 31 before 10 pm EDT, with activity diminishing overnight. Otherwise, the cold front will move across the area tonight and bring much cooler weather for Friday. Kept highs in the 60s over northwest areas. Will continue the Beach Hazard Statement for Friday given a fall type strong pressure gradient behind the front. && .LONG TERM...(Friday Night through Thursday) Issued at 342 PM EDT Thu Aug 3 2017 Cooler air will continue over the area through early next week with highs in the 70s as northwest flow aloft persists. Occasional upper level disturbances moving through an amplifying upper level TROF will provide chances for showers and storms Sunday and Monday, and possibly again Thursday. High temperatures should recover a few degrees by Wednesday and possibly top 80 degrees. && .AVIATION...(For the 00Z TAFS through 00Z Friday Evening) Issued at 725 PM EDT Thu Aug 3 2017 A lull in showers and thunderstorms occurs early before the cold front comes in perhaps with one more chance of showers and storms. Behind the cold front, expect cooling and subsidence and, with the entrance of a low level jet, a hint at the possibility of stratus clouds enters the mind rather than fog. Models have CIGs dropping to MVFR levels and will go with that thinking for now. Also, with the low level jet nearby, we`ll have to keep an eye on if any LL Shear forms overnight, but will keep it out at this time. Low level jet will remain nearby the region on Friday allowing for gusty winds during the time of diurnal heating. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Beach Hazards Statement from 5 AM CDT Friday through Saturday morning for INZ003. MI...Beach Hazards Statement from 6 AM EDT Friday through Saturday morning for MIZ077. OH...NONE. LM...Small Craft Advisory from 6 AM Friday to 11 AM EDT Saturday for LMZ043-046. && $$ UPDATE...Fisher SYNOPSIS...Skipper/Roller SHORT TERM...Skipper LONG TERM...Skipper AVIATION...Roller Visit us at www.weather.gov/iwx Follow us on Facebook...Twitter...and YouTube at: www.facebook.com/NWSNorthernIndiana www.twitter.com/nwsiwx www.youtube.com/NWSNorthernIndiana
Area Forecast Discussion
National Weather Service San Francisco Bay Area
440 PM PDT Thu Aug 3 2017 .SYNOPSIS...Monsoonal moisture overhead will bring a slight chance for showers and thunderstorms going into tomorrow. Gradual cooling is expected from Friday through the weekend. A weak disturbance will bring another opportunity for showers and thunderstorms over the North Bay Saturday night into Sunday. && .DISCUSSION...As of 12:40 PM PDT Thursday... Monsoonal moisture continues to stream into the southern two thirds of California in a band at 700 to 500MB, bringing a dynamic cloudscape across the region. KMUX radar has picked up on some light radar returns within the primarily weak convective development, but most precipitation occurring will fall as virga due to the relatively drier air mass below the cloud bases/closer to the surface. Most convective development has been limited in vertical development (a proxy of storm cell strength) due to the limited PWAT values and limited instability aloft. PWATs across our forecast area area gradually ticking upward and are around 0.8-1.0", however, more deeper convection does not appear to be occurring until PWATs push above 1.5" to 2.0" (such as the case in SoCal). That said, forecast models indicate there is still enough moisture and instability aloft to include a slight chance of thunderstorms across the area. Both the NAM12 and HRRR short term forecast models are suggesting that the most likely time frame for any thunderstorms will be late this evening through tomorrow morning, focusing around the 3-6am time frame. The latest few HRRR runs focus the bulk of convective development from the Golden Gate southward towards Big Sur during this time frame, however, elevated convection is notoriously difficult to resolve spatially and temporally. Any thunderstorms that do develop will generate only a few lightning strikes before weakening as the convective parameters are still marginal at best. Models show convection potential waning by midday tomorrow. A second opportunity for convection will occur as a small retrograding cut off low reverses course and makes landfall over the North Bay/Northern California coast. This will bring the best chance of the week for thunderstorms, primarily to the aforementioned regions, late Saturday through Sunday morning. Otherwise, temperatures today are running a fair bit cooler farther inland and at higher terrain, while coastal locations are actually a degree or two warmer, primarily due to the higher dew points and overnight minimums from the monsoonal airmass saturating the lower levels. The heat advisory for elevations at or above 750 ft will continue through the remainder of the day and expire this evening as the ridge subsides. The next few days will play out similar to today, with warm but gradual cooling temperatures inland, slightly below normal temperatures along the coast, an increased onshore presence and marginally deepening marine layer, and a continuation of the partly to mostly cloudy skies in the mid to upper level layers with a slight risk of isolated thunderstorms. For those interested, the next few sunsets and sunrises will be extremely photogenic as the low level stratus contrasts with the mid to upper level fractured cumulus. && .AVIATION...as of 4:40 PM PDT Thursday for 00Z Friday TAFs. VFR conditions are expected to prevail at all sites as high clouds associated with monsoonal moisture continue to pass over the region. There remains a slight chance that an isolated shower or even a thunderstorm could develop this evening and overnight, but the odds of it impacting a single site remain slim. Therefore, will continue to withhold from TAFs. Vicinity of KSFO...VFR conditions expected to prevail through the period. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR conditions expected at both KSNS and KMRY. Similar to yesterday, think the chances of seeing any low clouds remain low as the high clouds blanket the region. Will continue to monitor and amend if necessary. && .MARINE...as of 04:25 PM PDT Thursday...Light winds are expected to continue across the coastal waters through the week. There`s a slight chance of thunderstorms for the waters tonight and into tomorrow morning as mid and high level monsoonal moisture continues to sweep over the region. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...Heat Advisory...CAZ507-511-512-517-518 SCA...SF Bay until 11 PM && $$ PUBLIC FORECAST: DRP AVIATION: Rowe MARINE: AS Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, twitter, and youtube at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea
Area Forecast Discussion
National Weather Service Pueblo CO
319 PM MDT Thu Aug 3 2017 .SHORT TERM...(This evening through Friday) Issued at 256 PM MDT Thu Aug 3 2017 Initial upper wave and associated precip dropping south into NM as of 21z, while next weak feature was already forcing an area of tsra along the Front Range from Pikes Peak northward. LAPS and SPC mesoanalysis suggest narrow ribbon of instability is still present along and west of I-25 at mid-afternoon, with CAPES above 1000 J/KG from west of Colorado Springs south to Trinidad. Expect at least weak convection to move southward over the eastern mountains and adjacent plains into the evening, with HRRR suggesting a few stronger storms over the Wets and srn I-25 corridor in the 22z-02z time frame. Main concern the next few hours will be heavy rain on the Junkins/Hayden Pass burn scars, though rather brisk storm motions of 20-30 mph may help limit rainfall amounts somewhat. Plains east of the interstate look fairly stable, and will keep convective chances in the isolated range here. Convection shifts southward and weakens after sunset, with some lingering -shra over the srn mts and along the NM border after 06z. On Friday, warmer and somewhat drier conditions spread across the region as low level southerly flow strengthens by midday, especially across the eastern plains. With best low level moisture suppressed south and west, expect greatest coverage of afternoon convection to sink sw into the San Juans/La Garitas, while remaining higher terrain locations and interior valleys see mainly isolated storms. Interstate 25 corridor will see some isolated spill-over storms late in the afternoon, as higher terrain convection drifts se. Tsra chances over the far sern plains look rather low, though one or two storms could fire along the lee trough just east of I-25 by early evening. Max temps will climb several degf from Thursday`s cool readings, especially over the eastern plains, though most locations will still end up at or slightly below seasonal averages. .LONG TERM...(Friday night through Thursday) Issued at 256 PM MDT Thu Aug 3 2017 Northwest flow will remain over the area resulting in a relatively cool and unsettled extended forecast period. Friday evening most of the thunderstorm activity will be over the mountain areas though a few my drift off into the adjacent plains and may fire along the surface trof axis. Saturday looks like a relatively quiet day across the plains...but moisture and another disturbance will trigger scattered to numerous showers and thunderstorms across the mountains during the afternoon and evening. Saturday night a cold front drops through the plains increasing surface dew points and CAPE values for Sunday afternoon. This could be another potential severe day across the plains as deep layer shears are running around 35-40 kts. Thunderstorms could carry over into Sunday night as an MCS forms north of the frontal boundary. It appears we enter another wet period for much of the following week...as upslope flow keeps low level moisture across the plains, and west to northwest flow aloft sends a series of disturbances across the region. Monday may be pretty stable on the plains given the previous nights convection...but after that CAPE values climb back up to 1000 j/kg or better each afternoon (depending on the day) across the plains. -KT && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 256 PM MDT Thu Aug 3 2017 Scattered -shra/-tsra will impact all taf sites late this afternoon and evening, with brief periods of MVFR cigs/vis under any heavier convection. Precip ends late this evening, then MVFR or brief IFR cigs/vis in stratus/fog become possible at KCOS and KPUB after 10z as low level winds SE winds continue. On Friday, afternoon convection will again develop over the mountains after 18z, with at least a low chance of -tsra at all terminals after 20z. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...PETERSEN LONG TERM...KT AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service Las Vegas NV
702 PM PDT Thu Aug 3 2017 .SYNOPSIS...Much of the Mojave Desert and southern Great Basin will have a chance thunderstorms through this evening. Heavy rain and flash flooding will be possible with storms across the Mojave Desert. Thunderstorm coverage will trend more isolated and shift eastward Friday into the weekend with thunderstorm activity becoming more limited to the higher terrain by Sunday. Temperatures will be a little below normal through the weekend. && .UPDATE...I`ve trimmed the watch back, eliminating the Morongo Valley, the Colorado River Valley south of Bullhead City, and Southern Mohave County this evening. In addition, I extended the remaining areas of the watch through 10z since storms are likely to arrive around the previous expiration time. The rest of the details from the previous update still stand. Will continue to monitor and update as needed. -Wolcott- && .PREV UPDATE...440 PM PDT Thu Aug 3 2017 Convection has struggled somewhat to get going this afternoon across much of the forecast area. Conditions are becoming more favorable for scattered storms (likely developing into broken line segments) to push south/southwest late this afternoon/early this evening across Esmeralda, Nye, Lincoln, northeastern Clark, and northern Mohave Counties. This is due to a combination of ample destabilization from daytime heating as well as a developing cold pool that should help create lift. Current short range guidance and mesoanalysis suggests that the cold pool with push south to around the Clark/Lincoln county line or perhaps to near the Sheep Range north of Las Vegas before dissipating and shearing off the the west. This means that Las Vegas and areas south may not see much activity through the evening. To the south, cloud cover and trailing subsidence behind the vorticity max across San Bernardino County has limited afternoon convection. The Flash Flood Watch has been cancelled for those areas. For the moment I left the Morongo Valley, Lower Colorado River Valley, and southern Mohave Counties in place with a few storms nearing those areas. However, depending on the evolution over the next 2-3 hours, I may cancel those areas early as well. The aforementioned vort lobe will continue to ever so slowly weaken and drift north through tonight, becoming elongated in an east/west fashion in the process. As a result, precipitation is most likely to dissipate from both the north and south, possibly lingering across the central portions of the forecast area through sunrise. The forecast has been updated to account for the details mentioned above. Will continue to monitor and make changes as needed. -Wolcott- && .PREV DISCUSSION... 200 PM PDT Thu Aug 3 2017 .SHORT TERM...Through Friday night. Vort max well defined on satellite over eastern San Bernardino County early this afternoon will continue to move north through this evening while stretching apart or elongated with an east-west orientation. Although weakening, it should still provide some generally lift into the evening hours while the air mass remains quite moist and fairly unstable. Thunderstorm chances will continue in most areas at least through this evening with some overnight showers possible. Indications from most of today`s HRRR runs are t hat the strongest storms will likely be over Mohave County moving westward this afternoon with storms later this afternoon over Lincoln and central Nye Counties moving southward into this evening. How far west and south this activity maintains it`s strength is a big question and most of these model runs are tending to weaken the activity significantly during the evening with any overnight activity pretty weak. It looks like the focus for convection will shift to areas mainly north and east of Las Vegas Friday as the weakening vort max shifts northeast. Somewhat drier and more stable air will start to push into San Bernardino County and maybe southern Inyo County. There will still be enough moisture and instability for a slight chance of thunderstorms in the Las Vegas Valley and along the Colorado River. .LONG TERM...Saturday through Thursday. Models have been consistent past two days in showing a weak disturbance over southern Nevada and northwest Arizona Saturday. Associated dynamics along with plenty of moisture and instability will lead to isolated to scattered thunderstorms across Inyo County, southern Nevada and northwest Arizona. Sunday-Thursday period models still advertising a gradual drying trend with the coverage of thunderstorms becoming less each day, especially Tuesday- Thursday. Temperatures will probably hover at or just below normal over the weekend. As the airmass drys would expect temperatures to rise a few degrees above normal mid-week. && .FIRE WEATHER...Scattered to numerous thunderstorms expected again today, with gradually drying commencing Friday. Over the weekend, storm activity will begin favoring the higher terrain of mainly southern Nevada and Northwest Arizona. Even drier conditions are expected to push in next week, with only isolated thunderstorms expected across the southern Great Basin and higher elevations of Mohave county. Temperatures will be near normal through the period. && .AVIATION...For McCarran...Prevailing south to southeasterly flow will be present for much of the afternoon with best chances for showers and storms in the Las Vegas Valley between 21z-22z and again between 01z-05z. A southerly push after 00z with winds of 10-15 knots and brief gusts near 20-25 knots will be possible through 04z. After this point winds come down to around 8 knots or less remaining out of the south to southwest through Friday afternoon when winds are expected to increase to around 10-15 knots. Development of showers and storms Friday afternoon will be focused across the higher elevations with an isolated storm in the valley not out of the question. For the rest of southern Nevada, northwest Arizona and southeast California...Prevailing south to southwesterly flow between 10-15 knots is expected today. Areas of showers with embedded storms across southeast California, southern Clark, and Mohave counties will continue to slowly drift northward through the afternoon with heavy rain and brief, erratic wind gusts possible. Storms this evening will be focused across the southern Great Basin as they slowly drift southward through around midnight. Otherwise, diurnal wind pattern expected late tonight into early tomorrow with showers and storms focused further north on Friday afternoon. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ SHORT TERM...Harrison AVIATION...Guillet LONG TERM....Pierce For more forecast information...see us on our webpage: http://weather.gov/lasvegas or follow us on Facebook and Twitter