Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/09/19

Area Forecast Discussion
National Weather Service Bismarck ND
938 PM CDT Thu Aug 8 2019 .UPDATE... Issued at 933 PM CDT Thu Aug 8 2019 Decided to add severe wording to the forecast for Friday afternoon and evening. Although some uncertainty on cloud cover impeding the convection Friday morning, will mention teh severe threat by late afternoon as there will be time to clear the clouds a bit by then. Otherwise for tonight, followed teh HRRR pop trends as some convection already moving into southeast Montana. this will move into western North Dakota by midnight or shortly after. UPDATE Issued at 654 PM CDT Thu Aug 8 2019 Latest satellite loops show mid level convective debris across the northwest into the north central with no precipitation at this time so appears to be exhausted. The next focus will be a few showers across southeast Montana that will likely also fade into teh evening. Will need to wait for the nocturnal low level jet to form for any further thunderstorm development, and that should be after midnight. Current forecast looks ok. && .SHORT TERM...(This evening through Friday) Issued at 225 PM CDT Thu Aug 8 2019 Forecast highlights in the short term period will be a chance for some overnight convection after sunset west into central, followed by a risk for severe weather Friday afternoon/evening southwest and south central. Currently over the Northern Plains, northwest flow aloft with upper level ridging across the crest of the Rockies and a deep upper level low over far northern Ontario. Ridge of sfc high pressure from central ND southeast into eastern SD slowly developing eastward this afternoon. Embedded impulse moving southeast within the flow contributed to some mid level clouds and elevated showers across southern Saskatchewan and approaching northwest North Dakota. Will keep a low POP in there for a few hours this aft though doubt much will even reach the ground. Increasing low/mid level moisture tonight as return flow develops across the western half of North Dakota as the sfc ridge moves east into the far eastern Dakotas. Nocturnal low level jet coupled with a few hundred J/KG of MUCAPE should trigger showers and a few elevated thunderstorms scattered about, mainly north of I94 and along to west of Highway 83 after sunset. High res models seem to be in decent agreement with this scenario. Warm air and moisture advection continues/spreads across western and central North Dakota on Friday (sfc Tds in the low/mid 60s) as a low pressure trough develops across western SD north-northwest into far eastern Montana. MUCAPE is expected to reach 1-2 J/KG, though there remains some uncertainty on this depending on the coverage of morning convection/cloud cover. Latest guidance in fair agreement with a mid level shortwave positioned around the Big Horn Mtns/southeast MT around 12Z Friday, then moving east- northeast across southwest and south central North Dakota Friday morning/afternoon. Timing of the wave would suggest earlier height falls/CIN erosion leading to an earlier start of storms early to mid afternoon. Storm severity will depend on how much we destabilize ahead of the wave, so AM cloud cover and/or if we can clear in the afternoon will be critical. Storm potential decreases as we progress through Friday evening with any storms expected to move more into South Dakota and far southeastern North Dakota. Decent shear will be present (0-6 KM shear @ 30-40 KTS) so if instability can increase would expect discrete storms initially given flow is at 90 degrees of the sfc trough, then morphing into clusters as they move away. Large hail will be the main threat, and will be limited by rather weak projected mid level lapse rates. A small window for a weak tornado will be present given low level shear profiles as well. Again, much depends on how much we can destabilize. Will mention severe potential in social media, HWO, and state forecast. For now left out of the grids. .LONG TERM...(Friday night through Thursday) Issued at 225 PM CDT Thu Aug 8 2019 Active/cool weather pattern continues across the region through the long term period. The extended period will be highlighted by a strong short wave trough ejecting eastward across the Northern Plains Sunday through Monday. Widespread showers and thunderstorms are expected to spread east across western and central North Dakota Sunday afternoon through Monday morning, bringing widespread rainfall amounts of over one inch, some areas up to 2 inches. Instability and shear appear sufficient for severe storms, though too much uncertainty remains at this time. Quasi-zonal active flow continues through at least the middle of next week. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 654 PM CDT Thu Aug 8 2019 Hazards to aviation this period will be scattered thunderstorms that are expected to develop late tonight west, then become more numerous Friday afternoon across central North Dakota. At this time will not mention more than VCTS in TAFs due to uncertainty. Otherwise VFR. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...WAA SHORT TERM...NH LONG TERM...NH AVIATION...WAA
Area Forecast Discussion
National Weather Service Denver/Boulder CO
911 PM MDT Thu Aug 8 2019 .UPDATE... Issued at 911 PM MDT Thu Aug 8 2019 The main area of thunderstorms has moved east of the area already, a couple hours ahead of schedule. There is still a little area of convection which appears to be tied to some kind of band, perhaps the tail end of a jet streak, that will move from south of Denver toward the ESE for a couple more hours. There`s still a couple storms back around Eagle that could move along I-70 through midnight as well. Otherwise, there should be pretty good clearing overnight. That brings the possibility of some stratus or fog for a couple hours around sunrise. The HRRR continues to hint at a pool of nearly saturated air just north of Denver around sunrise, with a little north wind. My best guess would be a little patch of stratus for a few hours, but low confidence in exactly what will develop if anything. && .SHORT TERM...(This evening through Friday) Issued at 323 PM MDT Thu Aug 8 2019 Showers with moderate rain at times have developed over the foothills and Palmer Divide over the past couple hours. This thunderstorm activity should progress across northeast Colorado through the early evening. Up to this point, updraft strength has been modest, but more CAPE may be available over the far eastern zones, which could cause storms to strengthen later this evening. Moderate rain will be the main threat for the next hour or two, but then large hail may begin to develop later this evening to the east of a Fort Morgan to Limon line. Wind gusts of 40 to 50 MPH will also accompany the thunderstorm activity. After the evening storms move out, gradually decreasing cloudiness is expected. For Friday morning, cross sections have been showing westerly flow and some drying at lower and mid levels across northeast Colorado. The latest runs of the NAM are also backing off on the amount of shower activity Friday afternoon. It is hard to remove all of the Pops from the forecast, so will keep scattered to likely showers in the forecast for now. The highest coverage of showers should be over Park County and the Palmer Divide. .LONG TERM...(Friday night through Thursday) Issued at 323 PM MDT Thu Aug 8 2019 For Friday evening, it appears the best low level moisture and convergence associated with a weak lee trough will be pushing east across the plains. The best chance of storms, and certainly the strongest storms, during the evening would be along and east of a line from Sterling to Akron to Kiowa. That`s where MLCAPE is advertised to range between 1500 and 2500 J/kg. Therefore, some heavy rainers, wet microbursts, and marginal severe hail expected from the stronger storms there. Those storms will be decreasing and coming to an end during the late evening hours as the airmass stabilizes. The NAM was still trying to generate late night storms as another wave of moisture arrives from the southwest, but as long as the airmass gets worked over in the afternoon that threat should be minimized. For the weekend, we`ll see a return of deeper moisture from the southwest, with 700-500 mb specific humidity levels rising to 6 g/kg or more. This, along with persistent but weak QG forcing, will support higher shower and thunderstorm coverage each afternoon and evening. There should be some drying by Monday, but there`s still a wave noted that may sneak through the ridge to delay the drying. That drying should finally show up by Tuesday. We can`t be sure about how much, but at this time it looks like enough to have lower storm coverage and slightly warmer temperatures for Tuesday through Thursday. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 911 PM MDT Thu Aug 8 2019 Scattered thunderstorms are expected to remain south and southeast of the Denver area through 06z. Areas of IFR ceilings are expected near Denver from about 10z to 14z, though it`s uncertain whether this will directly affect the terminals. After that, VFR conditions are expected through Friday. Scattered thunderstorms will develop after 21z with the main impact a couple of wind shifts with gusts to 30 knots. && .HYDROLOGY... Issued at 323 PM MDT Thu Aug 8 2019 Scattered thunderstorms have been developing, mainly over the foothills and Palmer Divide. Occasionally moderate rain has been falling from the storms, which have been moving in a west- northwest direction. Precipitable water values have decreased a little bit from this morning and are currently betweeen 1 inch and 1.20 inches. Moderate rain will continue to be a threat through the evening, but as long as storms keep moving, hydrologic problems are not expected. Coverage of showers Friday afternoon is now forecast to be less than this afternoon due to an increase in westerly flow bringing some low level drying across the plains. No hydrology problems are expected Friday. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Gimmestad SHORT TERM...Dankers LONG TERM...Barjenbruch AVIATION...Gimmestad HYDROLOGY...Dankers
Area Forecast Discussion
National Weather Service Gray ME
927 PM EDT Thu Aug 8 2019 .SYNOPSIS... Scattered showers and thunderstorms will continue across the area through tonight ahead of a cold front approaching from the lower Great Lakes. The front will sweep through the area overnight followed by drier air and seasonable temperatures through the upcoming weekend. We`ll also see isolated mountain showers but otherwise dry weather is expected as an area of high pressure builds by to our south through Sunday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 920 PM Update...A few minor adjustments to the going forecast based on latest trends in observational data. Showers and thunderstorms are pushing off to the east...generally from the NH Seacoast northward to central ME. These will continue to move away. Will keep some low PoPs in overnight, however as an approaching short wave trough may allow for additional isolated showers and thunderstorms. One such batch of cells across north-central VT will weaken and move across Coos County NH through about 11 pm. Otherwise, plenty of valley fog is expected as well as in areas that had downpours today. Locally dense fog on the Midcoast of ME should persist overnight. 525 PM Update...Have updated the forecast for mainly minor changes in PoPs and wx this evening based on latest trends in radar imagery and latest HRRR guidance. Line of storms continues to move eastward in the vicinity of ALB NY with more isolated cells out front it across southern VT. At this time we believe our overall threat for severe weather is low. However, with the approach of the short wave trough to the west forcing for ascent and deep layer shear should improve soon. Therefore we cannot rule out an isolated strong to severe storm or two through about 2 or 3z. Previously... GOES water vapor imagery showed the lead shortwave impulse had exited all but northern and eastern sections of the forecast area. Scattered convection continued across the area at moment with coverage increasing the past few hours in response to heating. The second impulse and associated cold front were over the lower Great Lakes preceded by a a broken line of convection stretching from Ontario province southward across upstate New York into northern Pennsylvania. Through early evening we`ll continue to see scattered convection across the area. The squall line presently upstream over upstate New York will race east with CAMS suggesting it`ll begin to fall apart with loss of daytime heating as it reaches the Connecticut valley. Current motion suggests that a weakening area of broken convection will reach the Connecticut valley towards 00z. The primary threat would be a few strong wind gusts across the Connecticut valley before the activity quickly tapers to scattered showers and isolated thunder as it moves further east. With the exception of a few lingering showers across the mountains behind the surface front...a partly cloudy night with patchy fog developing. Lows will range from the upper 50s to mid 60s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... On Friday the westerly post frontal flow will quickly drop dew points into the comfortable range. Cyclonic flow and a series of passing impulses should produce clouds and scattered showers/isolated thunder across the higher terrain both Friday and Friday night. Highs should range from 70s in the mountains to lower 80s elsewhere. Lows Friday night will be in the 50s with a few upper 40s across the normally cooler mountain valleys. && .LONG TERM /SATURDAY THROUGH THURSDAY/... The extended forecast starts off with a closed 500 mb low over Quebec Saturday morning. This feature will migrate over northern Maine Saturday afternoon and will steepen lapse rates leading to convective showers Saturday afternoon. The best coverage of showers will be in the mountains and eastern zones. Weak ridging will move in on Sunday leading to a mainly dry day. The new work week starts off with a cold front crossing the region on Monday that will bring a returned chance of precipitation. After this front upper level flow will become more zonal with a fast moving low pressure system ejecting out of the Great Lakes. There is consensus that this low will track across southern New England bringing the best chance of rain to southern areas. However, the timing of this feature varies on the order of 24 hours. The CMC is the fastest bringing precipitation in Tuesday morning followed by the ECMWF that brings in precipitation Tuesday night. The GFS is the slowest bringing this system across southern New England Wednesday morning and also keeps most of the precipitation to our south. I have gone with gone with a multi model consensus that yields chance PoPs for Tuesday into Wednesday morning. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Short Term /through Friday night/...Sct MVFR in shra/tsra with lcl IFR in stratus and fog. VFR Fri and Fri night with sct MVFR in mtn -shra and isold -tsra. Lcl IFR btw 09 and 12z Sat in valley stratus and fog. Long Term...Restrictions are possible Saturday in convective showers. IFR is expected Sunday as weak ridging moves in. && .MARINE... Short Term /through Friday night/...Marginal SCA conditions for seas in southerly flow through late tonight. Winds will shift offshore Fri and seas will diminish. Long Term...Winds and seas will remain below SCA thresholds. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory for hazardous seas until 5 AM EDT Friday for ANZ150-152-154. && $$ SYNOPSIS... NEAR TERM...Ekster SHORT TERM...Schwibs LONG TERM...Schroeter AVIATION... MARINE...
Area Forecast Discussion
National Weather Service North Platte NE
623 PM CDT Thu Aug 8 2019 .SHORT TERM...(This evening through Friday night) Issued at 153 PM CDT Thu Aug 8 2019 Thunderstorm chances tonight are a blend of the RAP, HRRR, HREF, NAMdng and model consensus shifted north about 50 miles. This places a 50 percent chance of thunderstorms across the Sandhills which lines up with radar and satellite trends showing a disturbance aimed at that region. Sfc analysis shows a weak frontal boundary from roughly KCDR-KTIF-KBBW for sfc focus. The deep layer shear is quite strong with winds of 40-50kts in the 400-300mb level and high values of SBCAPE around 4000 J/KG should support a few briefly severe storms capable of large hail and wind damage. Winds at 500mb are weak at just 20 kts. Precipitable water increases to around 1.50 inches supporting a locally heavy rainfall threat. The models are fairly quiet Friday afternoon with just an isolated strong storm or two forming on the Cheyenne divide in Nebraska. The models show this activity dropping due-south into Colorado. Just an isolated POP is in place across parts of wrn and ncntl Nebraska. The the area of concern for storm development might be northwest Nebraska and swrn SD where the NAM and HREF show a dryline bulge developing late in the afternoon. .LONG TERM...(Saturday through Thursday) Issued at 153 PM CDT Thu Aug 8 2019 The SREF and GFS ensemble output continue to show a subtropical disturbance crossing Nebraska Saturday night. The deterministic models such as the NAM, GFS, GEM and ECM show the same but the precip location varies from nrn KS to Nebraska. Precipitable water will be very high for this event approaching 2.00 inches across wrn Nebraska which would certainly support heavy rainfall depending on the track of the upper level support. The forecast is for a 40-50 percent rain chance and later forecasts may include the mention of locally heavy rainfall. The flow aloft orients more southwest to northeast Saturday and beyond as the subtropical ridge across NM-TX migrates east toward LA- AR. At the same time, an upper level low moves into the Pacific Northwest. The models show the deep subtropical moisture being shunted south and east of Nebraska Monday or Tuesday and this should draw drier and cooler air south from Canada. The model consensus is in good agreement showing dew points falling into the 50s to around 60 Tuesday. One or more significant rain events is possible Sunday and Monday before the atmosphere dries out. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 623 PM CDT Thu Aug 8 2019 Scattered thunderstorms with significant reductions in visibility continue early the evening across portions of west central Nebraska. The activity is shown to be largely diurnally driven, so most of the activity should be over by 06z tonight. That being said, the latest HRRR is developing a complex across northwest Nebraska and carries it through KVTN after sunrise. Not sure about this, but with the numerous outflow boundaries across the Sandhills it cannot be discounted. We will monitor and update if needed. Otherwise, expect a increase in wind speeds after 13z at KVTN. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Jacobs
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
944 PM CDT Thu Aug 8 2019 .UPDATE... Issued at 943 PM CDT Thu Aug 8 2019 Stationary front over northern Missouri into west central Illinois will drift southward tonight. Latest satellite imagery is showing some cloud development along the front, and CAMS output continues to shows some development where the RAP has weak low level moisture convergence along the front. Will keep a slight chance of showers and thunderstorms going because of these factors. Otherwise, going lows looked good based on temperature trends. Britt && .SHORT TERM... (Through Late Friday Night) Issued at 236 PM CDT Thu Aug 8 2019 The MCS across SW Missouri continues to decay and drift to the SE, and there are no signs that any precip associated with the MCS will move into our CWA. Cirrus associated with the MCS will continue to thin and move out, setting the stage for a pleasant evening. As we turn to the overnight hours, attention shifts to a weak cold front that is currently situated near the Missouri/Iowa border. This front, which is associated with a surface low that has now moved off into the eastern Great Lakes, is moving very slowly to the south. The front is forecast to continue to slowly drift south into tomorrow morning and this may serve as a focus for shower or storm development as it moves through our area. A few of the CAMs support this idea, but with limited instability and weak frontal forcing, I don`t expected more than weak, isolated showers or storms, if they form at all. By tomorrow morning, the front will likely have reached roughly the I-70 corridor. At that time, there is some consensus in the synoptic models showing a weak shortwave dropping south through the NW flow aloft. This wave, coupled with the front and increasing diurnal instability, may be enough to force more scattered showers and storms late tomorrow morning and into the afternoon as the front continues to drift south. However, yet another MCS is forecast to develop over eastern KS tomorrow morning, which may result in more cirrus over portions of the CWA, limiting both instability and precip chances. Showers and storms that do manage to form will then likely diminish into the overnight hours as the front moves out and instability wanes. BSH .LONG TERM... (Saturday through Next Thursday) Issued at 236 PM CDT Thu Aug 8 2019 A surface high will build into the region on Saturday, keeping the mid-Mississippi Valley mostly dry despite some signal for a weak shortwave passing the region. A sharper wave is expected to build into the region on Sunday, providing the best chance for precipitation across the region over the weekend. While moisture remains similar to Saturday with dry upper levels and moist lower levels, there is a chance for precip on Sunday due to the consistency and proximity of the propagating disturbance coupled with the surface high moving out of the area. As the weekend closes the upper ridge begins to flatten, bringing the region into a quasi-zonal pattern. After the end of the weekend the models continue to diverge in the timing of short waves and smaller scale disturbances flowing along the ridge. Confidence in the timing of these disturbances is low, however the occurrence of these disturbances over the course of the week is expected. Each disturbance will bring the chance for showers and thunderstorms, however the lack of model consensus limits our ability to narrow in on timing of these waves of precipitation. This keeps a slight chance of precipitation in the forecast through the end of the period. MRM && .AVIATION... (For the 00z TAFs through 00z Friday Evening) Issued at 728 PM CDT Thu Aug 8 2019 Mainly dry and VFR conditions are expected during the period. A cold front currently located over northern Missouri will slowly move south across the area through tomorrow. Isolated showers and thunderstorms will be possible along the front, though coverage will be too limited to include in any of the TAFs for now. Surface winds will remain light. SPECIFICS FOR KSTL: Mainly dry and VFR conditions are expected through the period. A cold front will move slowly south through the terminal. There will be a slight chance of thunderstorms late tonight into early Friday at the terminal, but coverage will be too limited to include in the TAF for now. Surface winds will remain light. Britt && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Nashville TN
940 PM CDT Thu Aug 8 2019 .DISCUSSION... Per regional radar mosiac imagery and short range model consensus, pushed back any chances of shwrs/tstms until after midnight. Shwrs and tstms will move in from the west as the overnight hrs progress with a chance of shwrs/tstms expected for locations generally around and west of I-65 corridor shortly after sunrise Fri morning. A slight chance of shwrs/tstms will be possible for locations to the east overnight, expect for the Cumberland Plateau Region, which should remain dry. Also mentioned patchy fog developing after midnight, especially Cumberland Plateau Region. Tweaked hrly temp, dewpoint, and wind speed/direction grids. Current temps generally in line with current overnight forecasted low temp values. Latest HRRR and NAMNest model runs showing more of a sct nature to shwrs/tstms thru the morning into the early afternoon hrs, with numerous shwrs and sct tstms during the afternoon hrs on on Fri across mainly cntrl portions of mid state region. Made adjustments accordingly. Although areal QPF values not that significant, with model sounding runs depicting PWAT values, especially latest NAM, around 2 inches, some strong thunderstorms could be possible, especially across southern portions of mid state region. WPC Day 2 Excessive Rainfall Outlook placing locations generally along and just west of the Cumberland Plateau Region in a slight risk for excessive rainfall for Fri afternoon. Also made some minor changes to Fri night showing chances of shwrs/tstms slowly decreasing from mid state northwest portions as the evening hrs progress with patchy fog developing late evening and overnight. Made a minor tweak to sky conditions on Tue across southwestern portions of mid state region to emphasize ptcldy skies throughout day. Remainder of the forecast continues to be on track. && .AVIATION... 00Z TAF DISCUSSION. Quiet conditions expected this evening and overnight, with fog again in the forecast tonight into the early morning. MVFR fog will be possible at all TAF sites, but IFR or even LIFR fog may occur at KCSV/KCKV as well. Chances for showers and a few thunderstorms will move in during the morning hours after sunrise from west to east, with more coverage possible during the afternoon. Have VC mention due to low confidence on exact timing for terminals. Winds should be westerly around 5 to 10 knots during the day. && .PRELIMINARY POINT TEMPS/POPS... Nashville 75 87 70 89 69 / 20 50 30 20 10 Clarksville 72 85 65 87 66 / 20 50 20 20 10 Crossville 66 83 66 84 64 / 10 40 40 20 10 Columbia 73 86 70 88 68 / 20 50 30 30 10 Lawrenceburg 72 86 70 87 68 / 20 50 40 30 10 Waverly 74 85 68 88 68 / 30 50 20 20 10 && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......31 AVIATION........Barnwell
Area Forecast Discussion
National Weather Service Paducah KY
1020 PM CDT Thu Aug 8 2019 .UPDATE... Issued at 1019 PM CDT Thu Aug 8 2019 Very minor adjustments to weather, PoPs, temperatures, dewpoints, and winds to reflect slight spatial adjustments to account for the path of the southeastward movement of MCS along the AR/MO/KY/TN border to the south and the transition of a weak east- west oriented surface boundary and trough axis along and just north of the WFO PAH forecast area. Given first period cloud trends, added a brief period mention of fog in those areas not directly impacted by cloud cover from the MCS further to the south and west. The NAM-WRF ARW and NMM versions appear to have the best depiction of the movement of the minor weather systems through the area through Friday. The NAMNest, HRRR, and RAP CAM Guidance also have some reasonable depiction on timing and placement of convection and other sensible weather elements and were incorporated in the update. UPDATE Issued at 424 PM CDT Thu Aug 8 2019 Updated Aviation discussion for 00Z TAF Issuance. && .SHORT TERM...(Tonight through Saturday night) Issued at 303 PM CDT Thu Aug 8 2019 After a rain-free night over most of the forecast area, the chances for isolated (north) to scattered (south) thunderstorms will be with us for the day Friday as a weak cold front eases south into the region. Models are not as keen as yesterday with the possibility of a weak disturbance aloft interacting with the front, and many of the SPC CAMs now keep much of the region dry tomorrow. Therefore, needed to lower POPs across the board. Bulk shear remains meager, and low level convergence along sfc front looks weak at best. Thus, even with CAPES possibly in the 2000-3000 J/KG range, we are not anticipating a very high severe storm potential. Heavy downpours within a high PWAT environment appear more likely with any thunderstorm. It may take awhile for the weak surface front to clear the region Friday evening, and therefore will need to keep slight chc POPs in the forecast early in the evening. Saturday is expected to be rain-free as the front manages to sink south of the region before stalling and washing out. Was hoping to get a day of less humid air across the entire area Saturday, but as I kind of expected, the lower dew point air will lag the actual surface front. Thus, it is likely that only about the northern half or so of the region will get into the noticeably less humid air. Should stay quite muggy elsewhere with temps approaching 90 degrees. .LONG TERM...(Sunday through Thursday) Issued at 303 PM CDT Thu Aug 8 2019 The main story will be a cold front that will cross our region by mid week. Ahead of the front, one of the hottest air masses of the season will affect our region Monday into Tuesday. The very moist and unstable air mass will be ripe for convection, which would provide localized relief from the triple digit heat indices. Following the front, a northeast wind flow of warm and dry air will arrive for later Wed into Thursday. The models are forecasting 850 mb temps from 21 to 24 Celsius on Monday into Tuesday, which is about as high as they`ve been all summer. A few thunderstorms cannot be ruled out as early as Sunday in association with the heat and humidity. Weak northwest flow around an upper-level high over the southern Plains/lower Mississippi Valley could easily contain an mcv or other weak disturbance that would provide a trigger. However, for the most part Sunday into Monday appear rain-free. Dew points in the upper 70s will contribute to afternoon heat indices over 100, especially on Monday. The chance of storms appears highest on Tuesday, when a cold front will move southeast into the middle Mississippi Valley. Even if the front is slower than forecast, a mesoscale convective system could easily make its way across our area in the very favorable air mass. This has occurred several times this summer, but confidence in this case will not be high until the cam models cover that time range. Wednesday will be a transition day toward somewhat lower temps and dew points as the front finishes crossing our region. The difference in temps and dew points will be more noticeable Thursday, when high pressure over the Great Lakes brings a northeast wind flow. && .AVIATION... Issued at 430 PM CDT Thu Aug 8 2019 While downstream cloud debris may alter a repeat of last night, mos data does suggest another night of low cloud/fog is possible. Have therefore fine tuned inherited IFR-MVFR vsbys in fog patches late tonight-early tmrw, lifting to MVFR or low VFR bases tmrw. Also included daytime heating vicinity mention of storms as a weak boundary nudges into the forecast picture, mainly for KCGI/KPAH, per short res modeling. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ UPDATE...Smith
Area Forecast Discussion
National Weather Service Pueblo CO
858 PM MDT Thu Aug 8 2019 .UPDATE... Issued at 853 PM MDT Thu Aug 8 2019 Dropped Flash Flood Watch for the eastern mountains, but left the I-25 watch in place until midnight. Confidence is rather low we`ll see much additional convection, though at least a couple runs of the HRRR take storms currently near the Palmer Divide south through El Paso County toward midnight and beyond. Not sold on this scenario, but with dewpoints in the upper 50s to mid 60s along I-25, won`t take much to set off convection. && .SHORT TERM...(This evening through Friday) Issued at 255 PM MDT Thu Aug 8 2019 ...Active Monsoonal Weather Pattern Continues into Tomorrow... Current water vapor imagery and upper air analysis is indicating generally weak southwest flow aloft across the region, with the center of a large upper level high across southeast New Mexico and into the west central Texas. Water vapor imagery is indicating the monsoonal moisture plume across the Rockies, with PWATS of 1 to 1.5 inches (120-170 percent of normal) across the area this afternoon. SPC meso analysis is indicating mu capes ranging up to 1000 j/kg over the higher terrain, and between 1500 to 2000 j/kg across the southeast Plain, with effective shear of 20-40kts (strongest across the northern Front Range. With the ample moisture in place and several more hours of heating, expecting to see storms continuing to develop across the higher terrain through the late afternoon, with storms spreading east and intensifying as they move into a more unstable environment across the adjacent plains. With the moist easterly upslope keeping dew pts in the mid 50s to mid 60s across the Plains, storms will be efficient rain makers, with heavy rain and the potential for flash flooding remaining high through the evening hours. Also with the rich moisture and just enough shear in place, still can`t rule out some one or two severe storms across the Plains, with hail up to size of half dollars and and strong outflow winds up to 70 mph possible through the evening. Storms look to congeal into an MCS across the far southeast Plains which moves into southwestern Kansas and Oklahoma Panhandle later tonight. Similar pattern expected for Friday though the plains may take a little longer to destabilize. Another disturbance embedded within the monsoon plume will ride up from the southwest and fire off another round of thunderstorms across the mountains during the afternoon. With plenty of moisture in the atmosphere, locally heavy rainfall will be the primary threat, though with CAPEs running around 1500-2000 J/kg and deep layer shears around 30-40 kts, some embedded severe storms will also be possible with large hail and damaging winds possible. With discrepancies in the models regarding storm coverage (GFS keeps majority of the activity across southern areas while NAM12 is more generous with QPF and storm coverage across all of the mountains) will hold off on any Flash Flood Watches at this point. But certainly it will be another active day across southern CO and burn scars and urban areas will be most vulnerable to flash flooding once again. .LONG TERM...(Friday night through Thursday) Issued at 255 PM MDT Thu Aug 8 2019 ...Active thunderstorm monsoon weather pattern continues for Friday night through Monday... Good fetch of monsoon moisture remains over the area Friday night though there are some substantial differences in the models on how much QPF will occur across southern Colorado through the evening. NAM paints a wet picture over the southeast mountains during the evening with thunderstorms forming over the southeast mountains with the potential for heavy rainfall and flash flooding for burn scars. GFS and EC point to more of a Raton Mesa/far southeast CO MCS track. Given synoptic forcing over the front is in this area...the latter solution looks reasonable, but with dew points in the 50s and lower 60s still banked up across the southeast mountains and plains can`t really rule out the potential for isolated heavy rainfall across the southeast mountains either. Bottom line, we will still be at risk for localized flash flooding particularly on burn scars. Given the uncertainties on how widespread the threat will be, and exact location will hold off on issuing a new Flash Flood Watch for Friday evening. Activity should pull eastward during the overnight hours with the possibility of some lingering showers over the mountains through morning within embedded monsoon plume. Saturday and Sunday look similarly active with precipitable waters remaining around .75 in the west to 1.5 in the east. Still under the parade of embedded shortwaves within the monsoon plume and with dew points maintaining in the 50s across the plains and deep layer shears around 30kts, heavy rainfall, flash flooding and a marginal severe thunderstorm threat may persist into the weekend. The focus for thunderstorms across the plains may shift northward for Sunday according to some of the models but with lingering low level moisture over the area, these details are difficult to have much confidence in this far out. The fuel will still be in place though. Both EC and GFS suggest a stronger disturbance will move across the area on Monday, so another similarly active day looks probable. By Tuesday drier air may work in behind this system as flow aloft becomes more westerly. The upper ridge pumps again bringing another influx of monsoon moisture by late week. -KT && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 255 PM MDT Thu Aug 8 2019 While VFR cigs/vis will be predominant at the TAF sites through the evening, scattered to numerous showers and thunderstorms could cause brief MVFR cigs/vis with TSRA. All three TAF sites will carry a tempo group for TSRA through 01z at KCOS and KALS and through 03z at KPUB. Erratic gusty outflow winds will be possible near thunderstorms. Isolated GR along with gusts to 60 kts will be possible with any embedded severe thunderstorms through 01z and further updates may be needed should these approach the TAF sites. Thunderstorms will simmer down overnight with VFR conditions and light winds. Another round of thunderstorms will be possible Friday afternoon with the chance for MVFR cigs/vis and locally heavy rainfall. && .PUB WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 11 PM MDT this evening for COZ084>088. && $$ UPDATE...PETERSEN SHORT TERM...MW LONG TERM...KT AVIATION...MW
Area Forecast Discussion
National Weather Service Riverton WY
227 PM MDT Thu Aug 8 2019 .SHORT TERM...(This evening through Friday) Issued at 225 PM MDT Thu Aug 8 2019 Scattered thunderstorms are popping now that is 20Z, just as the HRRR had promised. The trend today will be for convection to move off the higher terrain and onto the lower elevations, and at the same time, the majority of the storm cells will migrate southwest to northeast across the CWA. The strongest storm cells today are expected to be across Johnson and Eastern Natrona Counties where the highest cape is already in place where capes are already up to 1300 J/K. The vort max that will be rotating clockwise around the high centered over New Mexico and Texas will provide the extra source of lift this afternoon. As it will take the better part of tonight for the vort max to rotate on through, lingering showers are expected to persist through tonight until about 10Z Friday. The thunderstorms that form will likely produce more widespread heavier rainfall than what occurred yesterday with the higher PWATs. On Friday, the ridge extending from the aforementioned high will rebuild, while the vort max exits the area. This will result in warmer and drier conditions Friday along with only a small chance of afternoon thunderstorms in Northwest Wyoming and the Northern Big Horn Mtns. .LONG TERM...(Friday night through Thursday) Issued at 225 PM MDT Thu Aug 8 2019 The upper ridge will build back into the region Friday night and bring a drier pattern across much of the state. Models are keeping most of the moisture across northern Wyoming for Saturday and Sunday as the low tracks eastward along the Montana/Canada border. A front associated with the low will push through the region Sunday for a return of widespread gusty winds and low humidities, especially across the south. Drier weather is expected through the middle of the work week, with even diurnal convection at a minimum, mainly over the northern mountains. High temperatures throughout the week will be in the upper 70s and low to mid 80s in the west, with the central basins and southern regions in the upper 80s and low 90s at times. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 225 PM MDT Thu Aug 8 2019 Scattered to numerous showers and thunderstorms will continue to develop across most of western and central WY for the rest of this afternoon through mid evening with VCTS necessary at all locations through the afternoon. Any thunderstorms will likely produce variably gusty winds. The weather system sparking most showers and thunderstorms will still be in the vicinity overnight, so have kept VCSH going for most locations through at least 06z Friday, with northern locations such as COD/WRL needing showers through most of the night. Drier weather is expected Friday with along with a small chance of showers and thunderstorms in far Northwest Wyoming. && .FIRE WEATHER... Issued AT 225 PM MDT Thu Aug 8 2019 Showers and thunderstorms will continue to increase in coverage through the evening with a mainly northeasterly motion. The thunderstorms will last into the late evening and then redevelop mid day Friday. The rain showers will continue overnight across the northwest and north. The main threat with any thunderstorms will be variably gusty winds. The humidity will drop 20 to 25 percent. Winds will be mainly below 15 mph, becoming light and variable overnight. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Lipson LONG TERM...Swanson AVIATION...Lipson FIRE WEATHER...Swanson
Area Forecast Discussion
National Weather Service Blacksburg VA
1014 PM EDT Thu Aug 8 2019 .SYNOPSIS... A cold front extends from the eastern Great Lakes into the Ohio Valley. This front is expected to move through the Virginias tonight and Friday, and into the Carolinas by Saturday. Scattered showers and thunderstorms are expected with the frontal passage. && .NEAR TERM /THROUGH FRIDAY/... As of 1005 PM EDT Thursday... Cluster of showers and thunderstorms in central West Virginia will continue to move east-southeast. Outflow from the storms will prolong convection through early morning, but the eastern end of this cluster will weaken as it moves south and east, similar to the trends during the evening. The marginal risk remains in place through 12Z/8AM in the Greenbrier Valley. Made adjustments to the placement of the highest probability of precipitation for overnight based on the latest radar trends. Between this cluster and high clouds spilling across the southern Appalachians, the sky was mostly clear. Have lowered minimum temperatures a couple of degrees and have maintained fog in the typical mountain valleys with little cloud cover. Deep west winds will dominate the environment ahead of the front as it crosses the area Friday. This westerly flow should limit showers and thunderstorms activity to the mountains, mainly western slopes, throughout much of the day. As mixing decreases late in the afternoon and evening across the foothills and piedmont counties, the approaching front with increasing thermodynamic support may generate scattered storms there. Temperatures tonight favor the seasonal norms. Compressional warming ahead of the front and downslope of the Blue Ridge should give an extra added boost to the temperature Friday with temperatures testing the lower 90s east of the Blue Ridge. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 235 AM EDT Thursday... Friday evening a cold front will continue its trek southeast trough the region. Lingering showers and storms are expected across mainly the far western, and also the far eastern sections of the region. The west is a area to watch because of the position of the front, and subsequent northwest flow, upslope conditions across this part of the area. Central sections are not favored given they will be in the heart of the northwest, downslope flow off the crest of the Blue Ridge. The east is an area to watch, but not as much as the west, as the impacts of the downsloping will be limited and this will be an area to watch for a weak lee side trough to coincide with the position of the exiting front. Through the weekend, dryer and cooler air will enter the region as surface high pressure settles overhead. aloft, a weak shortwave trough will cross the region during the peak heating of the day. Precipitation will be limited to some isolated showers and storms near and along the crest of the Blue Ridge Saturday afternoon, roughly from Floyd, VA southwest into the Northern Mountains of North Carolina. No precipitation is forecast Saturday night through Sunday night. Temperatures will trend cooler through Sunday with readings around or slightly below normal. Near, or slightly above normal, temperatures are forecast Monday. Confidence in this portion of the forecast is moderate to high. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 330 PM EDT WEDNESDAY... During this portion of the forecast, the persistent upper level ridge over the Ohio and Tennessee Valleys will break down in response to a shortwave trough crossing the Upper Mississippi Valley/Great Lakes region. This transition will take place between Monday and Wednesday, with the a weak upper level trough positioned over the East Coast by Thursday. Precipitation chances during this period are expected to be maximized Tuesday afternoon in the west as an associated cold front approaches the area, and then one Wednesday afternoon and evening as this front crosses the area. Coverage of lingering precipitation over the region on Thursday is questionable given the variations in the guidance solutions regarding the extent the front is able to head south of the region. A large push south would mean little to no residual precipitation with less of a push south meaning a better coverage of lingering showers and storms on Thursday. Our forecast will reflect a blended average of the various solutions, thus placing isolated to scattered coverage over parts of the area. Coverage of precipitation prior to the approach of the front on Monday is expected to be limited to differential heating across the mountains, especially those areas near the crest of the Blue Ridge, near and southwest of Floyd, VA, southwest into the Northern Mountains of NC. Temperatures during this portion of the forecast are expected to trend milder Monday through Wednesday. While high temperatures are expected to be a few degrees above normal each day, the low temperatures are expected to trend milder each day, with readings around 10 degrees above normal by Wednesday morning. For Thursday, high temperatures expected to be a few degrees below normal with low temperatures a few degrees above normal. Confidence in this portion of the forecast is on the low side of moderate. The biggest challenge is the timing and impacts of the cold front, and then its impacts when/if it departs our region far enough to exit the precipitation completely or not by Thursday. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... As of 750 PM EDT Thursday... Widespread VFR this evening. A surface front over the Ohio Valley has triggered a broken line segment of showers/storms from northern West Virginia into central Indiana. These thunderstorms are expected to move into WV this evening. HREF and HRRR guidance have these thunderstorms getting close to KLWB after 03Z/11pm and potentially as late as 06Z/2AM. Fog may develop in the mountain valleys again tonight, perhaps impacting KLWB and KBCB before daybreak Friday morning, but at the same time there may be enough debris cloudiness from storms in WV that may inhibit fog formation altogether. Any morning fog will dissipate by 13Z/9AM followed by VFR conditions for the rest of the day outside of scattered showers and thunderstorms along the front. Visibility will lower to MVFR with any heavy rain. Winds will be gusty behind the front in the afternoon with gusts out of the west to northwest up to 20 knots. Confidence is above average for ceiling and wind. Confidence is average for any lower visibility due to fog. .Extended Aviation Discussion... The front moves south of the Mid Atlantic region during the weekend which will result in dry, VFR weather for both Saturday and Sunday. Thunderstorm chances and associated MVFR ceilings and visibility return for Monday and especially later Tuesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PM NEAR TERM...AMS/PM SHORT TERM...DS LONG TERM...DS AVIATION...AMS/PM