Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/13/17

Area Forecast Discussion
National Weather Service Grand Forks ND
854 PM CDT Tue Sep 12 2017 .UPDATE... Issued at 854 PM CDT Tue Sep 12 2017 Most of the high resolution models are keeping the FA dry tonight. The latest runs show the echoes moving into central SD and drying up as they move toward our southern FA. For that reason will remove the low pcpn chances we had going across the far south for late tonight. && .SHORT TERM...(This evening through Wednesday) Issued at 235 PM CDT Tue Sep 12 2017 Wind shift moving into the northwestern portion of the FA this afternoon will stall out in a few hours across the northern third of the area. Will continue a slight shower mention in the southern valley overnight as SFC trough in SD with convection ongoing near the Blackhills lifts NE this evening into the overnight. RAP and latest runs of HRRR do show some activity reaching the southern valley near 10 to 12z. Also of some concern will be fog potential overnight with stalled boundary and light winds along this feature. Airmass dewpoints are in the 50s and 60s and with clear skies and light winds patchy fog does appear possible. Will continue to monitor the potential with lows expected to fall into the mid 50s and low 60s, near dewpoint values. Aforementioned boundary will help create a tight baroclinic zone tomorrow afternoon with max temps in the north along the Intl border in the upper 70s compared to across the central valley and areas to the south temps will be pushing near 90 again. The boundary will slowly work southward in the afternoon. .LONG TERM...(Wednesday night through Tuesday) Issued at 235 PM CDT Tue Sep 12 2017 Models are in general agreement for this forecast period. By Wednesday night and Thursday, the weather pattern changes and becomes more unsettled as southwest flow aloft begins to dominate, and an upper level trof digs in the intermountain west. Surface features indicate a relative open Gulf so expect some decent moisture transport ahead of the slow progressing surface system. As the surface system progresses slowly across the northern Plains, more beneficial rain amounts are anticipated, mainly in the one to two inch range. Otherwise, expect much cooler and cloudy conditions to be in place through Monday, with highs mainly in the 60s to near 70. By the end of the period, a slow warming trend will take place, with scattered showers expected. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 618 PM CDT Tue Sep 12 2017 Pretty quiet set of TAFS again. Wind speeds will remain on the lighter side, with just some high level smoke drifting in. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Godon SHORT TERM...JK LONG TERM...Hopkins AVIATION...Godon
Area Forecast Discussion
National Weather Service Sioux Falls SD
1052 PM CDT Tue Sep 12 2017 .UPDATE... Issued at 704 PM CDT Tue Sep 12 2017 Just launched an update for our far western zones in central SD for isolated to low end scattered chance pops for TSRA this evening. There is convection moving slowly eastward in western SD, and some of this may ooze into our far west later this evening. However the NMM and ARW, and HRRR for the most part do not bring it in the James River valley. Not a lot of dynamics are associated with this convection. && .SHORT TERM...(This evening through Wednesday) Issued at 232 PM CDT Tue Sep 12 2017 Quiet weather continues this afternoon as we remain stuck under weak flow aloft. This has resulted in clear skies and temperatures in the 80s at most locations. By this evening, a weak piece of energy sneaks off of the wave currently evident on WV imagery over WY, and slides along the NE/SD border. This could be enough to utilize some very subtle elevated instability originating from the 850-700 mb level. Current thinking is that dry air in the low and mid levels will limit this activity to just sprinkles however. Wednesday looks to be another warm but quiet day across the region as we remain between systems. High temperatures look to be a touch higher than this afternoon with 850mb temps in the low to mid 20s C, resulting in widespread mid 80s to mid 90s. Otherwise, looks for plenty of sunshine and southerly winds to continue. .LONG TERM...(Wednesday night through Tuesday) Issued at 232 PM CDT Tue Sep 12 2017 Strong southerly surface pressure gradient in place on Wednesday night, especially east of the James River, as low pressure deepens a bit over central SD. This should keep temperatures very mild through the night and will lean much closer to the CONSRaw output for morning lows which usually handles the windier nights much better. Will have to watch the Buffalo Ridge area as well with winds possibly turning a bit south southwest and a fairly shallow inversion in place. This pattern is occasionally supportive of stronger winds on the ridge so will go a little higher, but not too high as the wind direction is not quite normal to the Buffalo Ridge. Will have to keep an eye on thunderstorm chances towards central SD late Wednesday night as a weak wave moves through SD. For now chances will remain on the low end. Thursday looks to be warm, breezy and a little humid as a weak boundary drifts into central SD. A very small chance for early morning showers and thunderstorms as the weak wave moves through. By afternoon a boundary in central SD behind this wave does not appear as though it will produce any convection during the day as model soundings are strongly capped and mid and upper level heights are rising behind the exiting wave. Friday late afternoon into Friday night will see a threat for thunderstorms. A surface front will be in place across central SD into northeast SD with the warm sector in place across most of the area. Most of the warm sector looks pretty capped into the evening but locations a little closer to the boundary may see enough heating to break the cap. The area near the boundary is also more in line with the forcing from the upper level wave. Shower and storm motion will likely be easterly so the threat will shift east Friday night. While severe weather should not be a major issue an isolated strong to severe storm will be possible west of Interstate 29 with about 1500 J/kg CAPE and surface to 3 km shear about 30 knots. Saturday a tougher call with some disagreement on timing of the cold front. Will lean towards the slightly slower solutions as the upper level jet is progged to lift northeast which should allow the warm sector to heat out a bit before the cold air settles in. Increased lows a bit everywhere on Friday night with potential for clouds and southerly winds and increase highs a bit in northwest IA and southwest MN along and ahead of the front. Sunday into Tuesday will see cooler air settle in. Looks like the cool down will not be real significant and it should be fairly short lived as a trough of low pressure aloft deepens across the Rockies and an upper level ridge builds into the area. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1045 PM CDT Tue Sep 12 2017 VFR is expected over the 06Z TAF period. One thing to watch for is in the near term. Isolated TSRA continues in central SD near a surface trough axis extending southward from a short wave passing through to the north of this area. There is a chance that some of this skittish convection could reach the KHON TAF site from 08Z and 10Z Wednesday. However due to the isolated nature of this convection and not a high degree of confidence in their eastward movement, left out of the KHON TAF site for now. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ UPDATE...MJ SHORT TERM...Kalin LONG TERM...08 AVIATION...MJ
National Weather Service Jackson KY
1037 PM EDT Tue Sep 12 2017 .UPDATE... Issued at 1037 PM EDT TUE SEP 12 2017 WSR-88D radar continues to display a line of showers that continue to push north and east across the Bluegrass. Therefore, did update POPs to match latest radar trends and still seeing about a quarter of an inch or less storm total precipitation for most locations. The WSR-88D dual pol estimates seem to be doing reasonable based on some of the area gauges. The models seemed to continue to handle the line reasonably but still too fast. Overall preferred leaning toward the HRRR TL for the initial POP grid and manual adjustments there after. This will move out of the region and we will await the post tropical system to progress east. This could bring showers into the Lake Cumberland region toward dawn, but will likely be slow to advance east given the continued downslope flow across the Smokies to the south. Also updated with the latest obs and trends. UPDATE Issued at 750 PM EDT TUE SEP 12 2017 The afternoon surface analysis does show that post tropical system Irma is centered in Middle Tennessee and a area of surface high pressure remains to our north and east. There has been some weak upper level frontogenetical forcing moving northward across portions of central and eastern Kentucky this evening. WSR-88D does show showers developing near this forcing and moving northward. Did adjust the grids to match up with radar trends and short term model data. The one caveat is the models have been a bit too fast moving this north, and therefore made some adjustments to deal with this idea. It does appear that in general these showers will produce a quarter of an inch or less in QPE. Otherwise adjusted SKY, temps, winds, and dews to match latest obs a trends. && .SHORT TERM...(This evening through Wednesday night) Issued at 300 PM EDT TUE SEP 12 2017 The remnants of Irma will continue to bring scattered rain showers to eastern Kentucky the rest of this afternoon through late this evening as they meander about southern Mississippi and lower Tennessee valley regions. The remnants will begin a slow but steady northeastward track late tonight through early Thursday morning. Rain chances will steadily increase on Wednesday, as the center of the circulation moves over the area. The highest chances of showers will be from late Wednesday through early Thursday morning. Rainfall amounts should be low enough as to not cause any issues across eastern Kentucky. Temperatures will continue to run well below normal, with lows the next two nights in the upper 50s expected and highs on Wednesday in the mid to upper 60s expected for most locations. A few spots in our far eastern counties may max out in the low to mid 70s due to slightly less cloud cover there. .LONG TERM...(Thursday through Tuesday) Issued at 414 PM EDT TUE SEP 12 2017 The extratropical remnant of Hurricane Irma, in the form of a mid/upper level low, is expected to be centered over southern OH at the start of the period, with a pool of moisture rotating around it. The moisture will be primarily below the 600 mb level, but still sufficiently deep for light precip. Although amounts will be light, there probably will be enough rain to measure in most locations on Thursday morning. GFS MAV POPs are in the likely category for Thursday, and seem to be a reasonable fit. As the low continues to weaken and slowly move northeast away from our area, the low level moisture will also fade. The last of the precip should dry up in the afternoon or evening on Thursday, and clouds should start to break up. With light winds and only a limited rise in temperature during the day, it would be a good set-up for fog in locations which clear out on Thursday night. Any fog will dissipate on Friday morning as daytime warming kicks in. Forecast soundings show that the warming may support a few light showers in the eastern part of the forecast area on Friday, but convection would be sharply capped around 750 mb. Further west the cap would be even lower and not allow for more than fair weather cu. Mid/upper level ridging building into the area is then expected to bring mostly clear skies from Friday night through the weekend. Early next week, forecast confidence declines as the models fall out of agreement concerning a cold front moving in from the northwest. The ECMWF is the most progressive with the front, the Canadian the least, and the GFS falling in between. It`s initial approach would be from the northwest on Monday. The ECMWF has it moving past us to the southeast by Tuesday. Meanwhile, the other models stall the front and weaken it without a clean passage. Considering the uncertainty, have used a low POP each period Monday through Tuesday. Frontal passage vs. no passage would also have implications for temperatures, and a middle ground will be used. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) ISSUED AT 730 PM EDT TUE SEP 12 2017 The latest surface analysis shows post tropical system Irma centered across Middle Tennessee and high pressure still remains off the the north and east of the Ohio Valley. There is some upper level frontal forcing moving north across central and eastern Kentucky and showers are riding north along and near this mechanism. This could move into SYM and lead to VC showers at JKL, but otherwise not expecting any major issues related to this for most TAF sites. Overall the downslope flow and dry slot will keep CIGs VFR through Wednesday afternoon. The only other question tonight will be if clearing can take place in the east and decoupling of deeper valleys then you could see some patchy fog overnight. The post tropical system will move back as a more typical synoptic upper level low Wednesday. This will lead to increasing chances of showers especially Wednesday afternoon and this will be accompanied by lowering CIGs and VIS to MVFR. Winds will continue to decrease tonight and should stay fairly light through the period. However, some of the heavier showers that develop Wednesday afternoon could mix down stronger low level jet winds leading to isolated higher gusts. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...DJ SHORT TERM...AR LONG TERM...HAL AVIATION...DJ
Area Forecast Discussion
National Weather Service Nashville TN
749 PM CDT Tue Sep 12 2017 .UPDATE... FOR 00Z AVIATION DISCUSSION. && .DISCUSSION... Latest surface analysis places the center of the remains of "Irma" over far northwestern AL. This feature will continue to work slowly northward overnight. Latest model qpf and Hrrr data suggests shower redevelopment later this evening, beginning over western zones and eventually spreading east. Rainfall, however, will be on the light side with amounts averaging around one to two tenths. The slow northward movement of "Irma" will continue over the next few days. Thus, look for clouds to persist with a good chance of light shower activity through Wednesday nt. On Thursday, the remains of "Irma" will begin to spread eastward. So, after a final period of low pops, Thursday night will be partly cloudy and dry. For the near term temps, we will see another 36 hrs of cool weather before a warmup begins. High temps on Wednesday will again be in the 60s but as partial sunshine returns by Thu afternoon, temps will push well into the 70s. In the ext fcst, upper level high pressure to develop over the northern gulf on Friday with ridge amplification into the weekend. The ridge will weaken and drift westward next week, allowing for more of a northerly and westerly upper wind component to emerge. A frontal boundary will then approach. Thus, low shower and tstm chances will return for Monday. For the ext temps, the warming trend will continue on into the extended and will be helped by the aforementioned weekend ridge amplification. High temps over the weekend will reach into the mid to upper 80s west of the Plateau. these warm temps will continue into next week as well. Low temps will also be a few degrees above normal with 60 to 65 degrees expected. && .AVIATION... 00Z TAF DISCUSSION. As the remnants of Irma continue to swirl overhead, expect a trend toward IFR conditions overnight and a continuation of IFR at most terminals during the daylight hours on Wednesday as well. The only exception is expected to be at CSV, where IFR conditions overnight will trend toward MVFR after 15z. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......13 AVIATION........19
Area Forecast Discussion
National Weather Service Raleigh NC
1020 PM EDT Tue Sep 12 2017 .SYNOPSIS... An area of low pressure aloft will drift northeast from the Tennessee Valley into the Ohio Valley through Thursday morning. This will place central NC in a warm air mass with temperatures close to normal for mid September. && .NEAR TERM /THROUGH TONIGHT/... As of 1020 Tuesday... Little change to the near term forecast. As earlier discussed, low level flow has become swly across the southern Piedmont and dewpoints have lowered into the mid 60s at such places as Wadesboro (64 degs at 10 PM) and Albemarle (66 degs). The 00Z RAP appears to have a decent handle on this trend (possibly a little too aggressive); thus, this drier air should begin to infiltrate the Triad and the Triangle areas after midnight, and reach the Virginia border counties by daybreak. Beginning to see areas of fog develop in vicinity of the I-40 corridor, mostly in the Triad region. May see visibilities dip briefly to or below a quarter of a mile prior to the arrival of the drier air mass which should lead to improving visibilities. The same goes for the Triangle where areas of fog may limit the visibility to around a half mile prior to the arrival of the drier air. Currently expect the best potential for patchy dense fog to occur in vicinity of I-85 between the Triad and the VA border, and locations north of the Triangle. Isentropic upglide, as per 00Z 850mb analysis, helping to maintain a few showers along and north of the sfc warm front, stretching from the Triad to near Raleigh to Halifax. This flow expected to veer to a more swly direction overnight. This should place the focus for a few showers to develop over the far northeast Piedmont and far northern coastal plain. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday... IRMA`s remnant low will continue to weaken as it moves northeast through the Ohio Valley on Wednesday, before crossing the central Appalachians late Thursday. Central NC will lie along the far eastern and then southern fringes of IRMA`S remnant cyclonic circulation, with a glancing shot of DCVA supporting isolated to scattered showers late Wednesday/Wednesday night that could potentially linger into the day on Thursday, at least across the northern/northeastern portions of the forecast area. Instability is severely lacking, and thus no is expected. Temperatures will return to more seasonable values with the return of sunshine. Highs ranging from upper 70s NW to mid 80s SE. Lows in the lower to mid 60s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 PM EDT Tuesday... Increasingly sheared remnants of IRMA`S mid/upper level vorticity center will drift northeast and then linger across the Mid-Atlantic region through the weekend as as an upper level ridge over the western GOM builds slowly northeast into the region. Meanwhile, current forecast keeps TC Jose will be over the western Atlantic, though there is still considerably large model spread. Expect dry conditions with near normal temperatures expected to dominate this weekend and early next week. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 800 PM Tuesday... 24 hour TAF period: The Triad terminals will continue to experience LIFR ceilings for at least the next couple of hours. There may be a brief period where ceilings lift and then come back down again but in general expect these conditions through much of the overnight time period. Even if ceilings lift, visibilities could remain low in the form of fog until after daybreak. This pattern of low ceilings and visbys will pan out across the northern TAF sites in some form or another. KFAY is the only site that is expected to only experience MVFR visibilities at worst overnight. Otherwise they will clear out sooner as drier conditions move in from the south. Despite a few showers around precipitation will generally end from south to north overnight as the leftover rainbands from Irma exit the area. Conditions will gradually return to VFR after sunrise and should remain there through the end of the TAF period. Winds will be light and variable overnight and increasing to 5-10 kts out of the southwest on Wednesday. Looking ahead: Rain chances and also the chance for fog/low stratus during the overnight hours will remain in the forecast through Thursday before clearing out for a VFR weekend. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...CBL LONG TERM...CBL AVIATION...Ellis
Area Forecast Discussion
National Weather Service Reno NV
112 PM PDT Tue Sep 12 2017 .SYNOPSIS... Low pressure near the California coast along with above normal moisture will produce good chances for showers and thunderstorms through Wednesday. The first cold front of the Fall season will bring gusty winds Thursday along with another chance for showers or storms. The cold front will bring much cooler temperatures Thursday and Friday, with a modest warm up for the weekend. && .SHORT TERM... Current satellite imagery shows scattered showers and thunderstorms are developing and moving from south to north. For this afternoon and again tomorrow afternoon the ingredients are in place for scattered thunderstorms and localized heavy rain. Computer-modeled vertical profiles of the atmosphere show long skinny CAPE and not a lot of shear both afternoons, which suggests small hail and wetting rains are likely. There is also potential for some stronger/severe thunderstorms. Latest runs of high resolution HRRR model is consistent with this, showing areas of showers along with pockets of stronger cells. Any stronger cells that do develop will have potential for flash flooding (especially in steep terrain or on burn scars), gusty outflow winds 40 to 50 mph, and possibly up to 3/4 inch size hail. For tonight and again tomorrow night, areas of rain are likely to persist overnight, with isolated embedded thunderstorms possible. For Thursday, a cold front will bring westerly winds with peak gusts 25-35 mph in valleys and 35-50 mph along ridges. The relative humidity/wind gust combination doesn`t look too critical, although a few hours of red flag conditions in Mineral County may be possible Thursday afternoon. Showers (especially north of I-80) and a slight chance for thunderstorms (mainly east of highway 95) are also possible with the frontal passage Thursday. JCM .LONG TERM...Friday into next week... Computer guidance continues to show troughiness for Friday into next week. If skies are clear overnight there is potential for frost in colder valleys, so gardeners should check their forecast overnight temperatures and be prepared. Light northerly flow Friday/Friday night will shift to a dry southerly flow Saturday as the next trough approaches. This should lead to a slight warming trend for afternoon temperatures Saturday and Sunday, with highs forecast to be 75-85 in western NV and 65-75 for most Sierra communities. A cold front passage could bring strong gusty winds Sunday night/Monday along with much cooler temperatures early next week (highs could be mainly in the 60s Tuesday). The trough could also bring a chance of showers to the Sierra and northern CA by Monday afternoon, possibly spreading south and east across the eastern Sierra and western NV Monday night/Tuesday. JCM && .AVIATION... There is a 40% chance of thunderstorms at all main terminals (KRNO/KTVL/KTRK/KCXP/KMMH) this afternoon and evening, and then an equal chance again tomorrow. The main threats from these thunderstorms are erratic wind gusts up to 40 kts and heavy rain. Storm coverage and intensity should decrease after 03Z this evening and again tomorrow evening but scattered showers and a few thunderstorms could continue overnight both nights. A cold front passage on Thursday will bring gusty winds and chances for showers and thunderstorms. Thunderstorms on Thursday are not expected to be as strong but erratic wind shifts and brief MVFR conditions will still be possible. JCM && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...