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

Area Forecast Discussion
National Weather Service Gaylord MI
1150 PM EDT Fri Aug 17 2018 .UPDATE... Issued at 957 PM EDT Fri Aug 17 2018 Last of the diurnal convection (near and s of W Branch) has faded out over the last hour. Maybe a small shower can still fire for another hour or so, but otherwise we are mostly done with precip for the night. Most recent Rap run does pop a few showers over Saginaw Bay toward morning, perhaps due to converging land breezes. This does not require a mention of shower, at least over land. Have expanded the mention of fog across all of northern MI overnight. Airmass remains plenty soupy (especially in northern lower), and cloud cover is exiting east (though we might have enough smoke overhead to inhibit cooling to some degree). No big changes to temps. && .NEAR TERM...(Through Tonight) Issued at 340 PM EDT Fri Aug 17 2018 ...Showers and Thunderstorms Into the Evening... High Impact Weather Potential: Thunderstorms through early evening. Mostly non-severe, although a stronger storm/updraft could produce hail...along with heavy rain. Pattern Synopsis/Forecast: Slow moving closed low is over Chicago/southern Lake Michigan, associated broad surface low pressure is across far southern Ontario. Showers and some thunderstorms with this system continue across central lower Michigan back into Wisconsin within the associated deformation axis, just skirting our far southern counties. Further north, lots of mid/high cloud cover has spread up into northern lower Michigan, mainly south of M-32. SPC mesoanalysis reveals in excess of 500 J/KG MLCAPE across the southern counties. Some convection is now developing along the differential heating boundary that bisects northern lower MI currently. Strongest updrafts so far (supporting some elevated hail cores in the last hour) have been (of all places) in Benzie/Manistee counties, where the intersection of the Lake Michigan marine boundary has helped. Tonight: Closed mid-level circulation over the Chicago area still expected to open up and advance through lower Michigan through this evening. Band of showers/thunder associated with attending deformation axis will largely stay to our south, clipping the Gladwin/Arenac counties area. Meanwhile to the north, as noted, convection has started along the differential heating boundary that bisects northern lower Michigan and will likely continue to percolate/meander across northern lower Michigan over the next few hours before diminishing this evening. Always tough to know exactly how convection will ultimately unfold. But I suspect the bulk of showers/storms will tend to contract inland and south over the next few hours. Severe weather potential: Relatively light winds aloft, minimal ambient shear, and higher freezing levels suggest a low severe storm threat. But, as we`ve seen, strongest updrafts can support marginally severe hail. And, slow moving/back building updrafts will result in localized heavy rain. Will mention those in the HWO. && .SHORT TERM...(Saturday through Monday) Issued at 340 PM EDT Fri Aug 17 2018 Saturday through Sunday ...Despite the Small Rain Chances Saturday the next Round of Dryness Begins... High Impact Weather Potential...Thunderstorms, but nothing severe expected. Pattern Synopsis/Forecast...Models then begin to show another "wiggle" in the 500 mb height fields for rain to be possible, but it looks a lot less impressive than today`s convection, and yesterday`s convection. Things diminish quickly by the evening and dry out overnight. On Sunday, the high is built into the region, drying out the state. The high continues over the region through the night. Primary Forecast Concerns...Again is the thunder potential on Saturday, Most of the models are pegging the area near M-55 and I-75 as where the convection would occur. While the consensus is in that area, the ECMWF and the GFS have a broader coverage to the convection Saturday. So, there is a lower chance that it will be over portions of N Lower. .LONG TERM...(Monday night through Friday) Issued at 340 PM EDT Fri Aug 17 2018 ...Rain on Monday night/Tuesday then Pretty Much Dry through Friday... Extended (Monday through Friday)...The ridge breaks down Monday, allowing a cold front and the 500 mb low trough to move into the region. It looks like thunder will be possible as the cold front moves into the area Monday night/Tuesday morning. Then the models show a decent band of rain on the north side of the sfc low in a deformation zone producing some rain, possibly heavy at times, as the system move NE through the State. Will continue the cautious optimism as the models are holding onto this feature, but details are still a little less certain. As the GEFS plumes show the mean over GLR just under 0.5", but the GFS model, itself showing 1.4" and is the furtherest outlier. However, the latest ECMWF is also showing over an 1" of rain in Gaylord, as well. So it looks like a good soaker, but not sure about the heavy amounts that the deterministic models are trying to produce. Wednesday through Thursday are dry, then scattered rain on Friday so low chance pops there. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1150 PM EDT Fri Aug 17 2018 Some fog again overnight, otherwise VFR. Still expecting some fog overnight, with similar conditions to last night progged (IFR at times PLN, MVFR MBL/APN, no issues at TVC). Airmass remains muggy, and though some smoke aloft will limit cooling, ground fog is still expected. Additional showers/ storms will fire Saturday afternoon in some interior sections of northern lower MI, but these should be inland from all of the TAF sites. Light northerly breezes. && .MARINE... Issued at 340 PM EDT Fri Aug 17 2018 Lighter winds and waves will continue to dominate over the next few days. No marine headlines anticipated. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LH...NONE. LM...NONE. LS...NONE. && $$ UPDATE...JZ NEAR TERM...BA SHORT TERM...JL LONG TERM...JL AVIATION...JZ MARINE...BA
Area Forecast Discussion
National Weather Service Bismarck ND
949 PM CDT Fri Aug 17 2018 .UPDATE... Issued at 945 PM CDT Fri Aug 17 2018 Did add a mention of fog to the James River Valley tonight into early Saturday morning with greater moisture in place with dewpoints in the lower 60s. Otherwise, little change to the forecast from the previous update. UPDATE Issued at 654 PM CDT Fri Aug 17 2018 Little change with this update. It would appear that smoke will remain for the most part lofted across the area through at least Saturday, with perhaps an increase in near surface smoke possible behind a surface trough and cold front that will enter western North Dakota Saturday afternoon, and continue to propagate east into the evening. This is favored by the 18 UTC experimental HRRR smoke forecast. Smoke impacts to surface temperatures and convection initiation will continue to be evaluated for Saturday. && .SHORT TERM...(This evening through Saturday) Issued at 240 PM CDT Fri Aug 17 2018 The main concerns for the short-term forecast are smoke and increasing chances for showers and thunderstorms Saturday afternoon. Surface observations, webcams, and satellite imagery show a thick veil of smoke covering all of North Dakota this afternoon. The most dense smoke is located aloft - around 10,000 ft above the surface per pilot reports. So while surface visibility has not been reduced below 5 miles by the smoke, the sky has had a partly to mostly cloudy appearance all day, despite few clouds to speak of. In addition, the smoke has kept temperatures as much as 5-10 F below model guidance this afternoon. It is not entirely clear how long the smoke will remain this thick. Conditions look slightly improved upstream across northern MT and southern SK, but recent HRRR and RAP vertically integrated smoke actually increase concentrations tonight into Saturday. Will maintain up to widespread smoke mention through this afternoon, areas of smoke tonight, and patchy smoke Saturday, though adjustments may be needed. Upper-level ridge currently sits over the Northern High Plains. A weak disturbance is forecast to move across southern Saskatchewan into southern Manitoba tonight. A few CAMs and the GFS have been producing some QPF associated with this wave across northwest into north-central North Dakota. However, model soundings show a very dry boundary layer with CCL heights above 10,000 feet. Very low confidence that any precipitation would make it to the ground before evaporating, so will maintain a dry forecast for now. Farther upstream, a deepening upper-level low has made its way into the Pacific Northwest and will continue to propagate eastward toward the Northern Plains on Saturday. Surface cyclogenesis, low-level frontogenesis, and increasing moisture ahead of the upper low should lead to shower and thunderstorm development over the western Dakotas late Saturday afternoon. Instability (1500-2500 MUCAPE) will be sufficient for strong, possibly isolated severe storms, but weak deep layer shear (around 20 kts) will be a limiting factor for severe weather. Meanwhile, a surface cold front attendant to a shortwave trough crossing central Saskatchewan will move southeastward into northwest and north central North Dakota by Saturday evening. Could see isolated to scattered storms along this boundary as well, but stronger storms appear less likely here due to weaker instability. .LONG TERM...(Saturday night through Friday) Issued at 240 PM CDT Fri Aug 17 2018 The southeast-advancing surface cold front will interact with the upper-level low slowly drifting eastward across SD/NE Saturday night into Sunday. This will keep shower and thunderstorm chances in the forecast for all but northwest ND Saturday night, then decreasing to the southeast for Sunday. With cool, Canadian high pressure settling in and a transition to northwest flow aloft, highs will be limited to the 70s Sunday through Tuesday, with widespread lows in the mid to upper 40s. Long-range guidance is in agreement with a shortwave trough moving through the area late Monday. With a stable air mass in place, only showers would be possible, and it`s a slight chance at best. Tuesday and Wednesday look to be dry as an upper-level ridge axis approaches the Northern Plains. Another shortwave trough is then forecast to move through late Wednesday into Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 945 PM CDT Fri Aug 17 2018 Patchy fog may develop across the James River Valley tonight into early Saturday morning where dewpoints are highest across western and central North Dakota, possibly impacting KJMS. Significant, thick lofted smoke will continue across western and central North Dakota into Saturday. Near surface smoke reducing surface visibility may increase from west to east Saturday afternoon and evening behind a surface trough and cold front. Scattered rain showers and thunderstorms will also develop along these surface features Saturday afternoon and into the night. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...PA SHORT TERM...Hollan LONG TERM...Hollan AVIATION...PA
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1158 PM EDT Fri Aug 17 2018 .AVIATION... Wind directions have uniformly turned to the northwest or west in all location which has begun the drying out process of the atmosphere. Plan view progs suggest a slow drying response this evening, increasing now after 06Z. Deep downward motion is forecasted with building surface high pressure. However, subsidence inversion is not overly impressive and some diurnal instability will exist Saturday afternoon. Model trends are now suggesting some greater static stability in the midlevels. Dry conditions anticipated today. .DTW THRESHOLD PROBABILITIES... * Low for cigs aob 5kft overnight, medium Sat afternoon. && .PREV DISCUSSION... Issued at 338 PM EDT Fri Aug 17 2018 DISCUSSION... Extensive cloud cover remains in place over the area as the upper low near Chicago slowly makes its way east. Clearing over northern IN and southwest Lower MI has fostered modest destabilization and subsequently allowed showers and thunderstorms to develop in that area. This activity will spread into the the Detroit Metro area and points south and west into the evening as renewed warm and moist advection lifts into the area and larger scale dynamic forcing increases. In the meantime, mediocre convection will likely continue to flare up at times within areas of enhanced boundary layer convergence. Further north, more organized mesoscale forcing will still pose a threat for locally persistent heavy rain. However, the lack of destabilization to this point, HRRR analysis indicates just a few hundred J/KG MLCAPE, suggests the outcomes indicated by the 12z suite are highly unlikely. Instead, maintained likely to categorical pops and will simply highlight a locally heavy rain threat potentially leading to poor drainage or urban flooding. Little in the way of airmass change between now and Sunday as H850 temps hover in the mid teens within mean troughing regime. Scouring out of today`s moisture will limit convective potential, particularly as mid-level temperatures warm, favoring just diurnal cu-up Sat and Sun aftn as high temps settle in the low 80s with a decent coverage of upper atmosphere smoke worthy of an upward nudge in the sky grid. Midlevel ridging will remain in place on Monday as surface high pressure drifts northeast into New England, allowing for a dry Monday morning and afternoon for our area. Highs near normal in the lower 80s and light southeasterly winds expected. A shortwave currently moving over the Pacific Northwest will make its way into the central Plains by this weekend and interact with additional upper energy dropping in from the Canadian Prairie provinces on Tuesday, resulting in a strengthening mid-latitude cyclone moving into the Great Lakes by late Monday night. Long range guidance has begun to converge on a solution suggesting the center will track through lower Michigan during the day Tuesday. Chance for showers and thunderstorms increases Monday evening and lasts through the day Tuesday. A broad area of high pressure will build back in on Wednesday and maintain influence over the area through the rest of the work week, allowing quiet weather to prevail. The early week system will pull a good amount of cooler and drier air southward from Canada, leading to highs in the mid to upper 70s Tuesday through the end of the week. MARINE... A weak secondary area of low pressure tracking across Lower Michigan will maintain showers and thunderstorms this evening before exiting the region tonight. In its wake, weak high pressure will build across the Great Lakes bring dry weather for the weekend. Light to moderate northerly flow will prevail through the weekend, with peak gusts limited to around 15 knots. HYDROLOGY... A secondary low pressure system moving across Lower Michigan will bring scattered to numerous showers and thunderstorms through this evening. Rainfall amounts will generally range from a quarter to a half of an inch, with locally higher amounts associated with thunderstorms. The flooding threat will be minimal, with ponding of water on roadways and localized minor poor drainage flooding briefly possible where the heaviest rainfall occurs. Outside of an isolated shower Saturday afternoon, the weekend will feature dry weather with weak high pressure building across the region. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....CB DISCUSSION...JVC/TF MARINE.......JD HYDROLOGY....JD You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Glasgow MT
852 PM MDT Fri Aug 17 2018 .DISCUSSION... Previous forecast was generally in good shape. Main changes were to add "patchy smoke" wording in for tomorrow and tomorrow night, and lower/remove the POPs that were in there in/around Roosevelt and northeastern McCone Counties. The experimental HRRR Smoke model continues to suggest smoky/hazy conditions persisting, with upper level winds continuing to direct whatever smoke their is aloft coming from Washington and California towards us. Temperatures got a slight touchup, too, but nothing extraordinary. Avery Previous Discussion... There will be a change in the weather pattern by Saturday as a short-wave upper-level trough moves across the Divide. This pattern will bring a cold front to the area that will generate isolated to scattered general thunderstorms, and rain showers. With winds shifting to the north and diminishing heights, temperatures will trend back closer to normal for Saturday. As the short-wave trough and storms further descend into the Central Prairie, cooler air flows in behind, with temperatures dropping below normal. Expect highs in the mid to upper 70s for Sunday. Templer Previous Discussion for next week: For Monday, current high temperature forecasts show readings into the lower 70s, some 10 degrees below average or so. Thus, northeast Montana can expect a little relief from the above average temperatures late this week that are presently underway. For the middle of next week and beyond, due to the usual increase in model solution spread and associated uncertainties, the forecast was trended toward consensus model blends. This resulted in a gradual uptick in temperatures along with dry weather across the CWA. Maliawco && .AVIATION... VFR conditions are expected. Also hazy conditions are expected at times with patchy smoke across the region from upstream wildfires. It is possible that the smoke could lead to MVFR visibilities at times over area terminals, but prolonged periods of reduced visibility are not currently expected. A change will occur Saturday with a short-wave trough and cold front moving over the Divide. There will be the possibility of isolated to scattered thunderstorms and rain showers. Wind: southerly tonight at 10-15kt becoming VRB. Saturday wind will shift to the north and increase to 10-15kt. && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$
Area Forecast Discussion
National Weather Service Hastings NE
659 PM CDT Fri Aug 17 2018 .SHORT TERM...(This evening through Saturday) Issued at 203 PM CDT Fri Aug 17 2018 Aloft: RAP dynamic tropopause maps and upr-air data show fairly weak flow over the CONUS with the main belt of Westerlies zonal over Canada. Low-amplitude NW was over the Cntrl Plns with a shortwave ridge over the Nrn Rckys and a shortwave trof over the Pac NW. These features will progress E thru tomorrow...with the ridge moving overhead tonight and the trof crosses the Nrn Rckys. Surface: High pres extended from Ontario SW to OK. There was little else to speak of. This high will weaken and slowly creep E of the CWA tomorrow AM. Rest of this afternoon: p-m/sunny. Light winds. Another day of cooler than normal temps. Tonight: M/clear with just a few patches of cirrostratus drifting thru. Probably some patches/areas of fog again toward sunrise. Lows near normal. Very light/calm winds. Sat: Any early fog dissipates by 9 AM. Should be p-m/sunny again. Near normal temps. Light winds. .LONG TERM...(Saturday night through Friday) Issued at 203 PM CDT Fri Aug 17 2018 Aloft: The flow will be progressive thru next Fri. The mdls are in good agreement that the Nrn Rckys trof will deepen as it slides SE...forming a low that will cross Neb/KS Sun. Moderately- amplified NW flow will then develop Mon-Tue as the low moves into the Ern USA. A new low will form over the Pac NW this wknd. This low (or its remnant trof) is fcst to be kicked E Wed and into the Nrn Plns Thu. A shortwave ridge will precede it here on the Cntrl Plns Wed followed by zonal flow the trof will remain N of the rgn. The last 2 runs of the EC/GFS/UKMET/GEM are in good agreement... suggesting above normal confidence. Surface: A stationary front currently extended from the TX Panhandle to MI. Low pres will form on this front over OK Sat night. This low will move NE across the mid MS vly Sun-Mon and into the GtLks Tue. Meanwhile...a Canadian cool front will gradually sink S and merge with the low pres sys...probably crossing the CWA Sun night. Cool sector Mon. High pres arrives Tue. Return flow will develop Wed as the high departs into the OH Vly. Low pres is fcst to form over SD by 12Z/Thu with a developing warm front extending S thru Neb/KS. The warm front will move thru putting the CWA into the warm sector Fri while the low moves E. The associated cool front is currently fcst to remain N of the CWA. This scenario Thu-Fri is a bit shaky and will probably change a bit based on what happens aloft. Temps: The way things look now...much cooler than normal Sun-Tue with widespread 70s with high confidence. Some recovery Wed- Thu...but still a bit below normal. Then near or possibly above normal Fri. Confidence is medium Wed-Fri. Tue is looking like a gem of a day...with low humidity/dwpts in the 50s to near 60. Precip: widespread beneficial rain is probable for much of the CWA...but as always some locations will get more than others. Some localized pockets/swaths of 1.5-2.0" are on the table. Mesoscale details will determine where...including where the deformation zone/comma head precip sets up...and convective elements/ downpours. WPC is highlighting the SE 1/3 of the CWA for the heaviest rainfall. Most of the rain will fall Sunday into Sunday night. Spotty mostly diurnal shwrs could linger into Mon. Instability/shear Sun will be insufficient for svr tstms due to extensive cloudiness and light winds. SREF MLCAPE is fcst to remain below 1000 J/kg and 0-6 km shear will be 10-15 kt. The fcst may not have enough POPs/thunder Tue night thru Thu as warmer air and rich moisture return to the area. Watch for changes as spotty tstms will be possible at times. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 636 PM CDT Fri Aug 17 2018 A few passing clouds are expected overnight with the convection to our west expected to fizzle out well before it reaches the local terminals. With mostly clear skies and light winds expected overnight...could see some patchy BR develop...and maintained some MVFR VSBYS for a few hours overnight to account for this. Otherwise...a weak pressure gradient will remain in place to start the day Saturday...with increasing clouds late in the period ahead of the next disturbance forecast to impact portions of the local area late Saturday night through Sunday. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ SHORT TERM...Kelley LONG TERM...Kelley AVIATION...Rossi
Area Forecast Discussion
National Weather Service Grand Junction CO
536 PM MDT Fri Aug 17 2018 .SHORT TERM...(Tonight through Saturday night) Issued at 330 PM MDT Fri Aug 17 2018 Active weather is expected over eastern Utah and western Colorado from tonight through Saturday night. PWAT values have finally risen to over 1 inch as of today`s morning sounding at GJT with higher values farther south. This increase in moisture content has allowed for numerous showers and thunderstorms to develop throughout much of the higher terrain as expected. Convection will diminish in intensity this evening, but short-term guidance does indicate some instability lingering through the night especially south of US 50. Cloud cover as well as shower activity will likely linger for much of the night. Early on Saturday morning, a shortwave trough will approach from the northwest. A frontal boundary associated with this trough will dive south and eastward through Utah and Colorado, entering the Uinta mountain range just after midnight and exiting to the south of the San Juan Mountains by around 4pm on Saturday afternoon. If this front were only a handful of hours slower, this system would pose a legitimate severe weather threat across the western slope given strong forcing along the front, upper- level support for lift, and stronger wind shear due to an approaching jet streak aloft. However, the missing ingredient tomorrow will be instability, as this trough/front will pass too early in the day to take advantage of peak heating and prefrontal moisture content. That being said, a low-CAPE/high-shear threat (relatively speaking for the western slope) will evolve during the morning hours as this front marches southeastward. CAMs are in excellent agreement on the timing of this system, indicating FROPA in Grand Junction around 8am, Montrose by 10am, and Durango by 1pm or so. The potential for strong, gusty winds along this boundary and briefly heavy rain will still exist, despite lower instability values in the early morning. Farther south, enough heating will occur through late morning to result in a potential severe weather threat from Montrose southward through the San Juan Mountains. CAM guidance indicates anywhere from 1000-1500 j/kg of SBCAPE by noon, with around 25 knots of 0-6 km speed shear at the same time. The threat for stronger thunderstorms will end after the front exits east of the Continental Divide after 4pm. Overall, confidence in both the timing and thunderstorm threats on Saturday is high. As is usually the case with very defined frontal boundaries, dProg/dT analysis of recent HRRR and NAM Nest runs was essential for timing this event. .LONG TERM...(Sunday through Friday) Issued at 330 PM MDT Fri Aug 17 2018 Dry weather works in behind this front for Sunday and Monday as northwesterly flow resumes behind the departing trough. By midweek, high pressure redevelops in the southwestern CONUS and a more typical monsoon flow pattern becomes established. PWAT values in the medium range steadily rise through the period as southwesterly to westerly flow builds over the Four Corners. After a dry start to the week, increasing chances for shower and thunderstorm activity will be the main weather concern by midweek. Another shortwave trough skirts by to the north on Friday evening, but at this time it appears as though this system will have a limited impact on monsoonal flow. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 533 PM MDT Fri Aug 17 2018 Overall VFR conditions will dominate the forecast over the next 24 hours. There are still some passing showers and storms which could impact a few TAF sites through sunset before clearing. Expect early morning showers to move back in from the East...associated with a system passing through. Again isolated to scattered showers and storms are possible through mid to late afternoon. Confidence not high for impacts to specific TAF sites attm so vicinity will have to pass for now. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...MAC LONG TERM...MAC AVIATION...TGJT
Area Forecast Discussion
National Weather Service Grand Rapids MI
1159 PM EDT Fri Aug 17 2018 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 330 PM EDT Fri Aug 17 2018 Low pressure passing across southern Lower Michigan this evening will bring scattered showers and thunderstorms, some containing torrential downpours. The showers will end overnight, then a mainly dry and warm weekend is expected. A significant storm by August standards will pass through the Great Lakes Region Monday night and Tuesday, bringing widespread rain and thunderstorms followed by windy conditions. Dry, cooler, and comfortable late summer weather will follow behind that system for the rest of next week. && .UPDATE... Issued at 1008 PM EDT Fri Aug 17 2018 Showers have all but ended across the forecast area at 1000pm. An isolated shower will remain possible for another hour or two from roughly I-96 to the south, but for the most part expecting dry conditions. Next question will be cloud cover, which is more widespread across the south at this time. The cloud cover in the south is directly related to the upper trough being situated across that area. In general expect clouds to decrease even across the south, at least initially. The concern is that as the cloud associated with the upper trough begin to push south we develop stratus in a cooling but moist boundary layer. Hi-res models are becoming more bullish on low clouds filling in from AZO to LAN and points to the east of that line. Patchy fog is also expected as the surface winds will be light through the night. && .SHORT TERM...(This evening through Sunday night) Issued at 330 PM EDT Fri Aug 17 2018 Combination of the upper low tracking through this evening and very moist air mass with PWATs around 1.7 inches will result in a continuation of showers and tstms with torrential rain. The showers will be very slow movers so a localized flooding risk will exist over the next several hours as diurnal heating cycle peaks. Hard to nail down where best threat of flooding may be, although latest radar trends and HRRR suggest one area along/near I-94 and another from roughly Ionia to Flint. System moving out overnight so showers ending with decreasing clouds from northwest to southeast. The north flow behind the system is rather weak so doubt that the current dew points near 70 will drop off much overnight. That may lead to areas of fog developing again as skies clear, particularly where heavy rain occurs through 10 PM. On Saturday full sun is not expected. The combination of diurnal cumulus clouds and a relatively thick smoke layer aloft should lead to a partly cloudy/hazy sunshine type of day. Isolated afternoon/early evening showers cannot be completely ruled out on Saturday. Less risk of diurnal clouds and isolated showers on Sunday, although some smoke may still be present aloft. .LONG TERM...(Monday through Friday) Issued at 330 PM EDT Fri Aug 17 2018 Confidence continues to increase that a deepening sfc low will be tracking through the area on Monday night and Tuesday. Impacts will be widespread much needed rain then windy conditions as the low pulls away. A severe weather threat may develop Tuesday as the sfc cold front comes through, but timing of things and specifics still uncertain. Deep layer shear of around 35 kts is progged, although amount of instability unclear given expected high coverage of clouds/precip. This will be something to watch in the coming days. Regardless of cold frontal timing, marine impacts should be significant in the strong NW flow and cold advection behind the front Tuesday afternoon and Tuesday night. Weather then turns quiet for mid to late week. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1153 PM EDT Fri Aug 17 2018 A mix of VFR/MVFR conditions at the moment will gradually deteriorate to primarily MVFR during the early morning hours Saturday due to development of low clouds and patchy fog. Some patchy IFR is also possible early Saturday morning due to potential for some locally denser fog and/or low clouds. Conditions will gradually improve to mainly VFR by mid to late Saturday morning as patchy fog dissipates. VFR conditions will then continue at all the terminals Saturday afternoon through Saturday evening. && .MARINE... Issued at 330 PM EDT Fri Aug 17 2018 North-northwest flow over Lk MI looks to be remaining on the lighter side this afternoon, although it could be briefly stronger on Saturday from mid afternoon through early evening resulting a some choppier conditions for a time. Sunday looks like a tranquil day on the lake, and the winds on Monday should be mostly offshore. However hazardous winds are waves are a good bet on Tuesday into Tuesday night as deepening sfc low tracks through. Small Craft Advisories and Beach Hazard Statements will likely be needed, and gales/beach erosion are not out of the question either. && .HYDROLOGY... Issued at 154 PM EDT Fri Aug 17 2018 Rainfall over the past 24 hours...per MRMS with gage correction... has been more widespread than in recent days...with locations south of Grand Rapids showing one tenth of an inch or less. More isolated coverage of rainfall was indicated over northern sections of Central Lower Michigan...with some amounts in excess of one inch. The low amounts to the south and the isolated nature of the heavy rain to the north have produced little to no impact to area river levels. Heavy rain of 4 to 6 inches fell across east central Wisconsin since Thursday morning. Quite a bit of uncertainty as to the expected coverage and location of rainfall this afternoon and evening. Atmosphere has plenty of moisture to work with as precipitable water values in excess of 1.5 inches over most of Lower Michigan. Slow movement of showers and thunderstorms will also aid in producing increased amounts in areas that receive rainfall. Threat for significant impacts to area rivers is highly conditional over the next 48 hours...mainly due to the recent dry conditions. If precipitation can develop over a basin with appreciable areal coverage and persist long enough for significant runoff to develop...river stages could show significant rises. Combination of factors results in a low confidence forecast for river impacts over the next 48 hours. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ UPDATE...Duke SYNOPSIS...Meade SHORT TERM...Meade LONG TERM...Meade AVIATION...Laurens HYDROLOGY...MWS MARINE...Meade
Area Forecast Discussion
National Weather Service Lincoln IL
902 PM CDT Fri Aug 17 2018 .UPDATE... Issued at 901 PM CDT Fri Aug 17 2018 The upper trough axis resides over central IL this evening with surface cold front near I-70. Instability is weakening with the last remaining thunderstorms currently south of I-70, although an isolated shower or thunderstorm is still possible the next few hours to the north. The upper trough and front will continue to progress ESE overnight, with light and variable winds and skies clearing overnight, especially west of I-57. As a result, patchy fog should develop across the area after midnight. Currently, a large variety of depictions of the fog exist among several models, from minimal coverage to fairly widespread. Will therefore continue with patchy coverage. Lows ranging from 65 in Galesburg to 69 in Lawrenceville continue to look good for tonight. Updates sent this evening mainly to remove mention of precipitation over northwestern portions of the area, and continue isolated showers and thunderstorms SE. && .SHORT TERM...(This evening through Saturday) ISSUED AT 324 PM CDT Fri Aug 17 2018 Vigorous upper low currently centered over southwest lower Michigan continues to be the primary weather-maker across central Illinois this afternoon. With upper troughing in place and MLCAPEs analyzed from 1000-1500J/kg, widely scattered thunderstorms have developed...with the most concentrated area setting up along I-70. HRRR has been handling the situation quite well today, so will be following its solution closely in the short-term. As such, will linger chance PoPs along/south of I-70 through mid-evening...with just slight chance PoPs further north across the remainder of the ILX CWA. The showers will be largely diurnally-driven, so am expecting them to completely fade away toward midnight. Skies will clear in the wake of the short-wave trough overnight, particularly across the western half of the CWA. With clear skies, nearly calm winds, and plenty of boundary layer moisture...think patchy fog will once again develop late tonight. Low temperatures will drop into the middle to upper 60s. With the trough axis east of Illinois, synoptic forcing for scattered convection Saturday afternoon will be focused across the Ohio River Valley. While synoptic models such as the GFS/ECMWF hint at a few showers across E/SE Illinois, higher-res models are mostly dry. Will therefore scale back the PoPs for Saturday, with only slight chance PoPs during the afternoon across the far SE. Elsewhere, partly sunny and dry weather will be the rule with highs in the middle 80s. .LONG TERM...(Saturday night through Friday) ISSUED AT 324 PM CDT Fri Aug 17 2018 Short-wave ridging will develop across Illinois on Sunday in advance of the next upper disturbance digging into the central Plains. Given overall subsidence, am expecting mostly sunny and very warm conditions with highs in the middle to upper 80s. All models agree that the Plains wave will track eastward into Illinois on Monday, with only minor timing differences noted. It appears quite a bit of precip will develop along/ahead of a developing warm front late Sunday night into Monday...warranting high chance to likely PoPs at that time. The amount of cloud cover and ongoing convection Monday morning will play a major role in the potential for severe weather later in the the exact extent of destabilization remains unknown. If enough breaks in the overcast can occur and moderate instability develops, would not be surprised to see a round of strong to potentially severe convection develop across central Illinois Monday afternoon and evening as strong upper dynamics traverse the region. Once the early week short-wave passes to the east, northwesterly flow will take hold and temperatures will drop into the 70s for Tuesday and Wednesday. After that, all model solutions are suggesting rapidly rising heights by the end of the week...signaling a return to more typical summertime weather by Friday into next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 633 PM CDT Fri Aug 17 2018 Patchy fog is expected to develop overnight after isolated evening showers diminish this evening. VFR conditions are expected until around 07-09Z then MVFR or worse visibility is expected as fog develops, continuing until 14Z. VFR conditions are then expected the remainder of the TAF forecast period, with scattered cloud cover around 3000 ft AGL. Winds NW less than 10 kts this evening, becoming light and variable overnight, then NE less than 10 kts after 14Z. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...37 SHORT TERM...Barnes LONG TERM...Barnes AVIATION...37
Area Forecast Discussion
National Weather Service Indianapolis IN
1137 PM EDT Fri Aug 17 2018 .UPDATE... The AVIATION Section has been updated below. && .SYNOPSIS... Issued at 225 PM EDT Fri Aug 17 2018 Rain chances will continue tonight as low pressure moves across and exits the area. A few lingering showers will be possible early on Saturday as the low departs. High pressure is expected to build across Central Indiana on Saturday afternoon and Saturday Night. This will bring dry weather for the latter parts of the weekend. Another low pressure system is expected to arrive in the area on Monday and Tuesday. This will bring more rain chances to Central Indiana early next week. That low will depart by mid week...bringing a return to dry weather for the end of the next work week. Look for temperatures to remain at or below seasonal normals over the next week. && .NEAR TERM /Tonight/... Issued at 837 PM EDT Fri Aug 17 2018 Scattered convection continues across the area, as a mid level vorticity lobe and diffuse surface cold front drift south through the area. Expecting a gradual decrease in coverage of shower activity from this point on as heating is lost. However, the presence of the mid and level and surface features suggests the potential for some showers and thunderstorms will linger into the early morning hours of Saturday. Previous discussion follows. Surface analysis early this afternoon shows Low Pressure over Lower Michigan and Northern Indiana. Broad cyclonic flow was in place across the region GOES16 shows a swirling clouds across the region...denoting the circulation. Pop up cumulus clouds were found filling in any clear gaps as convective temperatures were reached. Surface flow was generally southerly or southwesterly and dew points remained in the very moist upper 60s and lower 70s. Radar shows shower development over western central Indiana as convective temperatures were being reached. Models this afternoon suggest a weak short wave embedded within the troughy flow aloft passing across Central Indiana. This combined with some afternoon heating should lead to some scattered showers lasting into the evening hours. Time height sections continue to shows good lift through the late afternoon and past 00Z with good lower level moisture available. Forecast soundings again show favorable lapse rates for afternoon convection. HRRR also suggests shower and storm development this afternoon...continuing into the evening. Thus will trend pops at or above the forecast builder blends with this favorable set-up for rain. Trough axis is expected to pivot southeast across the forecast area overnight...and rain chances should diminish as this axis passes along with the loss if daytime heating. Thus for now...will focus best pops in the 20Z-04Z time frame...trending downward after that. Given the expected clouds and rain...will trend lows at or above the forecast builder blends. && .SHORT TERM /Saturday through Monday/... Issued at 225 PM EDT Fri Aug 17 2018 Models show the trough axis sagging southeast of Central Indiana on Saturday morning as NW flow develops aloft. Forecast soundings respond with a dry column as the GFS shows a good mid level inversion arriving by 12Z. Time heights show subsidence arriving by 15Z. Thus forecast builder willing...will try and trend toward a dry forecast for saturday with decreasing clouds in the wake of the front. With minimal temperature advection in place...will trend highs close to the forecast builder blends. On Saturday night through Sunday night the models clearly show strong high pressure in place across the region...stretching from Ontario...across the Great lakes to the Ohio valley. Forecast soundings again show a dry column and subsidence is depicted within the middle levels. Thus will trend toward a dry forecast here and stick close to the forecast builder temperatures for highs and lows. On Monday the GFS suggests low pressure pushing toward Indiana from the Central Mississippi River valley. Models suggest by mid to late in the day on Monday...a warm front will arrive in Central Indiana ahead of the deepening Low over Illinois. Aloft...the GFS show a favorable upper level trough with ample forcing. Thus will trend toward high pops late in the day as these feature arrive. && .LONG TERM /Monday Night through Friday/... Issued at 330 PM EDT Fri Aug 17 2018 Primary focus of the long term will be early in the period as a low pressure system moves through the Great Lakes. This will necessitate precipitation chances in the first 48 hours or so before a large and somewhat fall-like high pressure system pushes into the region, bringing dry and somewhat cooler weather right on time mid to late week as meteorological summer nears its close. Blended initialization was generally acceptable minus removing some spotty slight chances late in the week. && .AVIATION /Discussion for the 180600Z TAFS/... Issued at 1136 PM EDT Fri Aug 17 2018 Light winds and a humid air mass may lead to the development of IFR ceilings, along with some fog, overnight. Some lingering mid level cloud may work against the low ceilings becoming too widespread. If these lower ceilings form, they will likely into the mid to late morning hours of Saturday. Light winds overnight will become 010-030 degrees at 7-10 kts by midday Saturday. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...Puma NEAR TERM...Puma/JAS SHORT TERM...Puma LONG TERM...Nield AVIATION...JAS
National Weather Service Jackson KY
1055 PM EDT Fri Aug 17 2018 .UPDATE... Issued at 1055 PM EDT FRI AUG 17 2018 Updated the grids mainly to reflect the latest radar trends and aggregate CAMs forecast through the night. This entailed a slower ramp up to likely PoPs after midnight across our southeast counties. Did also add in the latest obs and trends for the T/Td grids. These updated grids have been sent to the NDFD and web servers. Additionally, a freshened set of zones and HWO was issued. UPDATE Issued at 745 PM EDT FRI AUG 17 2018 23z sfc analysis shows a slowly moving cold front and general low pressure off to the northwest of the CWA with a meso high located over the Cumberland Plateau. The bulk of the storms in the region are taking place well to the south in Tennessee while a few scattered ones are trying to develop over central parts of eastern Kentucky taking advantage of the 2000+ J/kg CAPE available for the next couple of hours. Most of the CAMs keep these evening storms limited favoring development later tonight similar to the ones that took off last night. Have nudged the grids in this direction allowing for more in the way of thunderstorms with the convection that develops. Again we will have to watch for excessive rainfall in any locations that see training from these. If a larger scale cluster of storms manages to develop a short fuse flash flood watch may be warranted. For now will maintain the mention of heavy rain in the HWO and social media messaging. Currently, readings are in the mid to upper 70s most places with dewpoints well up there in the low to mid 70s. Winds are mainly from the southwest at 5 to 10 mph. Have also updated the near term T and Td grids per the latest obs and trends. These freshened grids have been sent to the NDFD and web servers. && .SHORT TERM...(This evening through Saturday night) Issued at 435 PM EDT FRI AUG 17 2018 Aloft, long wave trough is found over the upper Midwest with eastern Kentucky under a southwest flow regime. At the surface a series of weak low pressure waves appear along a semi-stationary frontal boundary draped roughly from the Great Lakes southwest to St. Louis, and further southwest to about Oklahoma City. Another upstream cold frontal system is dropping out of the Northern Tier and appears to make it no further south than the Great Lakes Region. The southernmost surface front makes an honest move eastward through the short term and may have enough support aloft from the aforementioned trough to push through our area late Saturday into Saturday night. Regardless our area remains in an unsettled pattern until the frontal zone passes entirely through the Commonwealth. The lull in activity this afternoon is coming to an end as strong diurnal heating is beginning to kick off some isolated activity across our forecast area late this afternoon. The HRRR showed a general and gradual increase in activity through the late afternoon and evening, mainly from the southwest and across the south. Activity continues through the overnight as it appears more organized convection takes shape, similarly to the previous few nights except just a bit futher east each night. This activity appears to take shape as a result of the typical increase in the H850 winds through the overnight period just above the boundary layer. Synoptic setup allows for some pockets of increased convergence in spots as weak but distinct H850 LLJ maxes help in generating the bands of more organized convection. Our area remains in a slight risk for heavy rain with any hydro issues being mainly confined to areas where training cells set up, similarly to the last few days. Temperatures remain generally at or just below normals due to precipitation and additional cloud cover as afternoon highs climb into the low to mid 80s and overnight lows drop into the 60s. .LONG TERM...(Sunday through Friday) Issued at 352 PM EDT FRI AUG 17 2018 The models are in fairly good agreement with the overall pattern for the extended. Weak upper level ridging, formed by an upper level cutoff low located in the Central Plains digging to the southeast, will help bring a brief lull in precipitation for eastern Kentucky late Sunday into early Monday. The cutoff low will evolve into a deep trough and progress across the eastern CONUS through midweek before moving off to the northeast Thursday. Southeastern Kentucky will see chances of showers and thunderstorms Sunday afternoon into the evening as a surface boundary passes to the south of the Commonwealth. A warm front associated with a surface low pressure system in Missouri will set up over Kentucky early Monday. This low pressure system will migrate to the northeast and settle over the Great Lakes by Monday evening, lifting the warm front to the northeast and keep chances of showers and thunderstorms Monday into Tuesday. A cold front will begin progressing through western Kentucky during this time as well. This cold front will move through the Commonwealth, bringing increased chances of showers and thunderstorms through midweek. By Thursday, a surface high pressure will build in over the Ohio Valley, ushering in drier conditions for the end of the work week. High temperatures will generally be in the mid 80s Sunday and Monday with low temps in the upper 60s through Tuesday morning. High temps will cool down to around 80 degrees by midweek with lows temps in the lower 60s Thursday and Friday mornings due to frontal passage. Temperatures will then be on the rise Friday afternoon. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) ISSUED AT 820 PM EDT FRI AUG 17 2018 A few scattered showers and thunderstorms are around this evening but it is generally quiet. Expect convection to redevelop during overnight hours due to some pockets of H850 convergence and with the advancement of a cold front toward the state. Will add thunder into the TAF for the limited activity this evening and that better development later tonight. Ceilings and visibilities will likely lower with convection redeveloping into Saturday morning. The convection chances will taper off from north to south during the day, Saturday, as the cold front drops through the forecast area. Winds will generally be out of the south/southwest around 5 to 10 knots during the daylight hours, but could be higher in stronger showers and thunderstorms. Otherwise, generally light winds are expected overnight. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...RAY LONG TERM...CGAL AVIATION...GREIF