Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/01/18


Area Forecast Discussion
National Weather Service La Crosse WI
637 PM CDT Fri Aug 31 2018 .SHORT TERM...(This evening through Saturday night) Issued at 238 PM CDT Fri Aug 31 2018 Still lots of unknowns in the forecast but short range models are starting to give a somewhat clearer picture of what is expected to occur. Early this afternoon there was a cold front from extreme northwest Minnesota into North Dakota. A stationary front was parked across central Missouri into northern Kansas. While both of these features will be a player for the area, the front over Missouri is expected to be more relevant as it lifts back north as a warm front. Water vapor satellite showing a weak short wave trough embedded in the mean long wave trough over eastern Montana. This wave will push east tonight and stay to the north while pushing the cold front southeast across Minnesota. Showers and storms already starting to develop across northwest Minnesota ahead of this system and these will drop southeast toward the area this evening. This activity is not expected to be near the area until about the middle of the evening with the best chances expected to be across the north closer to the short wave trough. By late this evening and into the overnight, the front across Missouri will start to lift back to the north into Iowa. However, not sure how far north it will make it as it is currently be held back by ongoing convection just north of it. It may not move much until the low level jet kicks in late this evening. If the front can get back into southern or central Iowa, a round of showers and storms will develop along and north of it as the low level jet runs into the boundary. There is also a short wave trough coming across Nebraska that will provide additional forcing for the showers and storms to develop. Looking at several runs of the RAP and the 31.12Z NAM, the mid level frontogenesis in the 850-700 mb layer looks to be focused right into the southern sections of the forecast area. Expecting to see rapid growth of showers and storms north of this boundary during the late evening into the early overnight with this activity then persisting into Saturday morning before diminishing as the low level jet veers off to the east and weakens. The main threat from this activity will be the heavy rain/flooding potential, see the hydrology section below for more details. Some potential for large hail and damaging winds early in the storm cycle until a transition over to mainly heavy rain occurs overnight. The ML CAPE pool looks to primarily stay along and west of the Mississippi River and into southwest Wisconsin and looks to be in the 1000-2000 J/Kg range. The shear looks to primarily be in the 0-3 km layer and on the order of 20 to 25 knots. The 0-1 km shear will increase as the low level jet forms develops but this doesn`t look to come into play as the storms should be elevated above this layer north of the boundary. This will leave some large hail and damaging winds then as the main threats outside of the heavy rain. The boundary will still be hanging around the area through Saturday night with the continued threat of showers and storms across the southern sections of the area. .LONG TERM...(Sunday through Friday) Issued at 238 PM CDT Fri Aug 31 2018 An active period is expected with a continued heavy rain threat through much of the week. A large mid/upper ridge will remain anchored across the Mid-Atlantic region with west to southwest flow aloft upstream over the Midwest. Various embedded shortwaves will translate through the flow to produce occasional rounds of showers and storms. The atmosphere will remain conducive to heavy rainfall with precipitable water values exceeding 2.0 inches at times, corresponding to +2 to 3 standard anomalies via the NAEFS. Mesoscale details concerning surface boundary/upper wave placement and consequently convective focus are uncertain, especially given the messy surface pattern and potential contamination from storm outflow. However, the overall pattern certainly suggests a heavy rain/flood threat will continue during this time. Not expecting much change in airmass through the week, with highs in the 70s to low 80s. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 637 PM CDT Fri Aug 31 2018 A quiet evening underway out there, and expecting that to continue through at least 06Z with just some passing thicker mid and high clouds at times as winds gradually subside from their earlier gustiness. Still not the clearest picture of how far north showers and storms will develop later tonight, but given the setup and best moisture arriving just south of the area, starting to think LSE and RST may escape much in the way of any showers and storms, though of course will be watching trends closely through the evening. Some increase in moisture later tonight should again allow for some MVFR/IFR stratus to develop, similar to last night, though thinking this will be later given current trends and not sure just how widespread it will be. Nevertheless, whatever forms may stick around longer into Saturday morning (at least) with much weaker wind flow in place as compared to this morning. Any risk for showers and storms for LSE and RST should taper off by mid to late morning, with any stratus likely to gradually scatter out through the afternoon hours. && .HYDROLOGY... Issued at 238 PM CDT Fri Aug 31 2018 Will be issuing a flash flood watch for southwest Wisconsin into northeast Iowa for tonight into Saturday. As noted above, as the boundary lifts back north, rapid development of showers and storms expected late this evening as the low level jet impinges on this boundary. The precipitable water values will increase to around 2 inches near the boundary with warm cloud depths of 4 to 4.5 km. Expecting the storms to be very efficient rain producers and included a band of close to two inches of rainfall centered roughly along the Wisconsin River in southwest Wisconsin and expecting that localized amounts will be higher than this. Some of this rain will fall on areas that are already dealing with saturated ground and flooding from the rain earlier in the week and cannot take much more water. For northeast Iowa into Grant County, the ground is not as saturated but terrain is a concern and this area known for mud slides with heavy rain. For now, will include the areas where confidence is highest for a flash flooding threat but the location of the boundary will have to be closely monitored through the evening for possible adjustments to the watch area. Flooding continues along the Kickapoo River, but for the time being, levels are going down. For more details see the latest flood statement. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Flash Flood Watch from 10 PM CDT this evening through Saturday evening for WIZ053>055-061. MN...None. IA...Flash Flood Watch from 10 PM CDT this evening through Saturday evening for IAZ011-030. && $$ SHORT TERM...04 LONG TERM...JM AVIATION...Lawrence HYDROLOGY...04
Area Forecast Discussion
National Weather Service Hastings NE
857 PM CDT Fri Aug 31 2018 .UPDATE... Issued at 856 PM CDT Fri Aug 31 2018 A few thoughts regarding the rest of tonight (through sunrise): Be prepared to hear/read this a LOT over the next several days, but we are in the midst of a very tricky/challenging weather pattern as far as predicting the "exact" timing and likelihood of rain/thunderstorm activity. Focusing solely on the rest of tonight, the very basic/general story is that there will be a gradual increase in shower/thunderstorm activity as the night goes on, as the coverage of mostly-sub-severe storms continues to increase off to our west over western NE/KS as of this writing. With time, some of this activity will spread east into our coverage area (CWA), with additional "new" storm development possible overhead. As noted by preceding day-shifter, forcing is not particularly strong, but the presence of a series of weak waves moving in from the west should be sufficient to generate at least isolated-to-scattered activity. Did not have the confidence to advertise "likely" 60+ percent rain chances/PoPs into any particular area overnight, but did make some modest 10-20 percent increases in PoPs across especially our northern half versus previous forecast. The vast majority of storms should not be severe tonight, but agree with SPC in maintaining a broad Marginal Risk to account for the possibility of some marginally severe hail and (perhaps to a slightly-lesser extent) wind. Will defer to upcoming night shift to modify the going forecast for Saturday daytime and beyond. && .SHORT TERM...(This evening through Saturday) Issued at 330 PM CDT Fri Aug 31 2018 Aloft: RAP dynamic tropopause animations...aircraft data and WV imagery showed low-amplitude WSW flow over most of the CONUS with the mean longwave trof axis from Sask down thru the Pac NW. There is a small low over Nrn CA/NV. This low will open up as it heads E across NV into UT tonight into tomorrow. This will result in more of a pronounced Wrn trof by 00Z/Sun that will extend from MT to AZ/NM. Surface: A weak low was analyzed over SD with a weak cool front extending WSW thru the Neb panhandle into WY-UT-NV. A sfc trof extended S thru Cntrl Neb into Wrn KS. The low will fill with the front sagging SE into the CWA tonight. This front will be just E and S of the CWA by 00Z/Sun and cont to weaken. Meanwhile...very weak high pres will settle over Neb tomorrow. Rest of this afternoon: Hot. Humid over S-cntrl Neb. The KSU mesonet site near Beloit hit 102F early this afternoon. 100F at Jewell. With this cirrostratus moving thru N-cntrl KS now per IR satellite...those locations probably won`t get any hotter. The atms should remain capped in the wake of this AM`s tstm activity which produced a lot of vivid CG strikes. Tonight: Increasing clds as svrl CAMs and the HRRRX ensemble suggest sct tstms will move thru mainly after 10 PM. SPC has a MRGL risk for svr and it seems reasonable given the MUCAPE from the 09Z SREF is fcst btwn 1500-3000 J/kg. Effective deep lyr shr will be 30-40 kt. While a shortwave trof is not fcst to move thru...the RRQ of an 85 kt jet streak over MN will move over the Cntrl Plns. It will be another warm/muggy night. Sat: Any tstms lingering at dawn should exit the CWA to the E during the AM. With the front bisecting the CWA most of the day...can`t rule out an isolated shwr or two developing at any time...but much of the daytime hrs should be dry. By 4 PM sct tstms should develop with the greatest chance near the front (from N-cntrl KS to near HJH). SREF MLCAPE is fcst btwn 2000-2500 J/kg with effective shear near 40 kt. 0-3 km SRH is fcst 150-200 m2/s2. So while the primary convective mode should be multicell...a supercell or two can`t be ruled out. Temps will drop back to near normal behind the front...but it will still be humid. .LONG TERM...(Saturday night through Friday) Issued at 330 PM CDT Fri Aug 31 2018 Aloft: A longwave trof will remain over the Wrn USA with a subtropical high over the E. Early week will be more amplified with SW flow over the Cntrl Plns. Mid-late week will be more WSW. Multiple low-amplitude shortwave trofs will exit the Wrn trof. Surface: Another weak cool front will move into the CWA Sun. That front will dissipate Mon with a stronger front fcst to arrive Wed. High pres will briefly move in Thu then it`s back to the warm sector Thu-Fri. Temps: Highs will be near or a little cooler than normal. Lows will be warmer than normal. Rain: It could be heavy. WPC has SLGT risk of excessive rainfall Sat and Sun due to potential for repeated tstm development. Sat eve/night could be quite active as sct tstms will be on- going over the SE 1/3 of the CWA. Other storms could be moving in from the W...and other storms could develop over the CWA as the low-lvl jet ascends above the remnants of the weak front. There are no dry periods in the fcst. There will be at least a chance for tstms every day...the way it`s currently looking. Some chances will be better than others...but predictability is low with tstm development tied to low-amplitude shortwave trofs. The last 4 operational EC runs are outputting an average of 2" of rain across the entire CWA over the next 10 days...with potential for some areas E of Hwy 281 to receive as much as 4-6". && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday) Issued at 714 PM CDT Fri Aug 31 2018 General overview: This is going to be a tricky/challenging period with regard to especially the potential and timing of thunderstorms. As for ceiling and visibility, have officially advertised VFR through the period for now, but this is also no guarantee, as at least brief MVFR ceiling and/or visibility could materialize, either associated with convection or perhaps not. Wind-wise, assuming no pronounced thunderstorm-related influences (outflow), sustained speeds should average near/below 10KT the vast majority of the time, with direction generally somewhere between northerly and east-southeasterly. Read on for more element-specific details... Rain/thunderstorm potential: Honestly, the only high-confidence in this forecast is these first 5-6 hours, as both terminals should manage to stay storm-free through then. However, anytime after that, there is JUST enough of a chance for convection in the general area that have decided to blanket the majority of the period with a basic "vicinity thunderstorm" (VCTS) mention. Do not normally like to run with VCTS so many consecutive hours, as there will likely be some "breaks in the action" so to speak. However, these "breaks" are looking difficult to pin down, with various forecast models showing the potential for showers/storms at almost any point between late this evening and late Saturday afternoon. Hopefully later forecasts can better pin down details. It`s also worth noting that there will be at least limited potential for a severe storm with hail/strong winds. Ceiling/visibility: While the majority of models/guidance suggest prevailing VFR, and have advertised as such for these TAFs, there are at least 3 caveats that bear watching: 1) Obviously any localized thunderstorm activity could briefly promote sub-VFR conditions...2) There appears to be at least limited potential for an intermittent low-end MVFR ceiling especially beyond the first 9 hours...3) There could be some light fog potential late tonight into Saturday morning (especially if thunderstorm activity is minimal), and have "hinted" at this with a "6SM BR" mention between 06-15Z. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ UPDATE...Pfannkuch SHORT TERM...Kelley LONG TERM...Kelley AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1103 PM CDT Fri Aug 31 2018 .UPDATE... Short term grids adjusted to match ongoing temperature/moisture/rainfall behavior. Expecting a quiet early morning start to the holiday weekend with coastal showers beginning to fester up once again just before sunrise. As has been the case the past couple of days, early day near coastal showers will move across the first two tier coastal counties before noon...more isolated shower or storm activity may reach further inland once mid to upper 80 F convective temperatures are met. As we travel further into the weekend, an upper level inverted trough moving westward towards the upper Texas coastline will increase areawide rain. Increasing moisture levels will also spike Sunday and Monday`s rainfall probabilities. Some high resolution guidance are becoming more aggressive with their QPF mass fields...particularly on Sunday. Best to have an indoor Plan B in place for any Sunday or Labor Day outdoor activities. 31 && .PREV DISCUSSION... /ISSUED 629 PM CDT Fri Aug 31 2018/ AVIATION... Iso shra should taper off with the loss of heating this evening. The next 24 hours looks fairly similar to the past, so will be going w/ a fcst of persistence: mclear to partly cloudy overnight, scattered shra/tstms developing near the coast toward sunrise, then some developing inland during the day w/ heating. VFR conditions should persist outside of any convection. 47 && PREV DISCUSSION... /ISSUED 358 PM CDT Fri Aug 31 2018/ Overall there has not been nearly as much convection today as the last couple of days. There is still enough moisture along the coast to support at least some isolated storms along the US59/I-69 corridor between Sugar Land and Victoria. Short range model guidance has been decent with resolving this convection. There is also some convection developing along the Harris/Montgomery Co line which the HRRR has also resolved. Going with these trends in the near term forecast look good going forward. The main issues for not having more convection deal with the overall upper level pattern and gradient in higher moisture to the east and along the coast. Upper level analysis shows that the upper level ridge has moved more over the Red River with 500mb temperatures increasing from -7C to -5C. That might not seem like a lot but it does signify more stability aloft and possible subsidence from the ridge. Also noted in upper level analysis is the inverted trough/tropical wave off the Louisiana coast. This should be the system to affect SE Texas Sunday and Monday. The forecast next week is really the story of two tropical waves. The first as noted above will be moving into the area Sunday into Monday. Precipitable water values increase to around 2 to 2.3 inches over the weekend and remain there into Monday. The NAM increases PWAT values closer to 2.5 inches but based on current trends in the GOES 16 PWAT imagery that might be overdone. The NAM also produces quite a bit more rainfall on Monday due to this. This trend in the NAM is something to put away back in our minds but the forecast will lean more on the GFS/ECMWF solutions. Rainfall amounts over the weekend look to be anywhere from 0 to 3 or 4 inches on the high end and those higher totals will be isolated like we saw on Wednesday. Labor day weekend may not be a complete washout but with the trends in the models the odds of a washout look to be going higher. As such we have also increased rain chances for Sunday and Monday based on the higher moisture and the upper level trough/tropical wave moving over the region during this time. Finally there is the tropical wave/invert trough aloft over Hispaniola that has been the subject of future tropical cyclone development in the eastern Gulf by next Monday through Wednesday. Most models are taking this trough/tropical wave towards Louisiana Wednesday and then westward towards SE Texas Thursday into Friday. The track will largely depend upon the strength of the upper level ridge to its north and if that ridge expands west towards the Midwest. This development of the ridge will likely steer the system more on a westward track rather than turning the system north. The main impacts from this system so far should be higher thunderstorm chances. None of the models are showing the development of a tropical system but conditions should be more favorable late next week that this system deserves monitoring through the weekend and early next week. Mainly Gulf waters are well warm to say the least but forecast data differ on 250mb winds which would determine how much shear would affect the system. These kinds of details will need to be watched but still way too soon to speculate on the nature of tropical development with this system. Bottom line is to just keep track of NHC outlooks and monitor forecast trends. 39 MARINE... Generally light to occasionally moderate E/SE winds are expected to prevail through the weekend...and into the first part of next week. This pattern is courtesy of broad high pressure over the east coast and a low pressure system slowly moving across the Northern Plains. However, winds/seas will be higher in and near the scattered storms that are expected to develop over the coastal waters these next few days. The unsettled weather pattern (from weak disturbances embedded withing the easterly flow aloft and deeper Gulf moisture) should remain in place through the forecast cycle. The better rain chances are expected during overnight/early morning hours. 41 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 75 95 75 93 74 / 10 20 10 40 40 Houston (IAH) 76 91 76 89 76 / 10 40 40 60 50 Galveston (GLS) 81 90 80 88 81 / 20 50 60 70 50 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ Discussion...31
Area Forecast Discussion
National Weather Service Lincoln IL
1051 PM CDT Fri Aug 31 2018 .UPDATE... Issued at 835 PM CDT Fri Aug 31 2018 We still have some isolated showers and storms around the forecast area this evening with one area mainly east of I-57 tracking to the north. A second area of weakening showers was over west central IL, and they were tracking to the east. The latest HRRR continues to show a weakening trend with both areas this evening with our attention turning towards west central Iowa on the nose of a 50 kt low level jet and some decent 850 mb moisture transport later this evening which should produce stronger convection overnight to our west, eventually making its way into our area by morning in a weakening state. The outflow boundary from the Iowa MCS will provide a focus for additional thunderstorms to develop tomorrow afternoon. However, the main question is where that will be as models are not exactly depicting one location for storms to develop later tomorrow, although the trend over the past few runs has been hinting at areas to our north. Another very warm and humid day in store for the area, in fact, there will be little change in the forecast into a good portion of next week as an upper level ridge builds west across the Midwest, which would tend to shift the better storm threat further to our west and north with time. This pattern should keep afternoon temperatures well above normal for the first week in September with daytime highs well into the 80s, possibly the low 90s in a few locations, which will drive heat index values into the mid to upper 90s through at least Wednesday. Have made some adjustments to the POPs for the overnight hours along with some tweaks to the early evening temperatures. We should have the updated ZFP out by 9 pm. && .SHORT TERM...(This evening through Saturday) ISSUED AT 313 PM CDT Fri Aug 31 2018 500 mb map dominated by a weak trough over the western coastal states, and a general southwesterly flow pattern from the desert SW into the Great Lakes. Central IL is on the edge of the more progressive flow, and with a high pressure ridge situated along the eastern coast of the CONUS, southerly flow is keeping the warm and humid air moving into the region. That southerly flow and plenty of warm air in the mid levels will keep tonights lows near 70/lower 70s in most areas. The warm the temperatures will continue tomorrow, warming considerably over todays highs, and starting another hot stretch of the forecast, through the weekend and into next week. With temperatures very warm, and plenty of low level moisture, and the ridge axis well off to the east, the boundary layer is vulnerable to the forcing of outflows from surrounding areas. This afternoon, the showers and thunderstorms are confined to the southeast, as well as to the west of the Mississippi River Valley. Minor pops are in place for areas southeast of Interstate 70, and NW of the IL River to cover potential development in those areas...with the northeast getting an assist going into tomorrow from an approaching weak boundary. .LONG TERM...(Saturday night through Friday) ISSUED AT 313 PM CDT Fri Aug 31 2018 Forecast blend having a hard time resolving the approach of a weak boundary and the southerly extent of the showers associated with that boundary, given that Central IL is caught between the more southwesterly flow aloft, and a building upper ridge over the southeastern portion of the country. Low chance pops are more widespread on Sunday, then retreat with the better chances west of I-55. However, until a forecast pattern changes, the region will likely see a lot of chance pops (particularly diurnal enhanced showers/thunderstorms) until the hot and humid boundary layer either moves out, or dries out. After midweek, the chance pops become the norm instead of the exception for just that reason. The same stagnation of pattern also means that the heat is here for the duration of the forecast. And with temps in the upper 80s/low 90s, and dewpoints surging into the low 70s...the nights through next week do not drop below the lower 70s, and the max heat indexes are back in the mid to upper 90s. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1045 PM CDT Fri Aug 31 2018 The main forecast concern will be timing of storms into our northern TAF areas Saturday morning as convection was slowly beginning to develop over west central Iowa late this evening. Outside any thunderstorm, we expect VFR conditions through this forecast period. The CAM models have done a poor job with respect to the isolated convection across east and southeast Illinois this evening as well as with a secondary disturbance which brought in some scattered showers to the west early in the evening. However, with the stronger forcing event starting to occur west of the Missouri River late this evening, thanks to the increasing 850 mb moisture transport/convergence and low level jet, short term high resolution models seem to be handling things well with convection developing across southwest through west central Iowa. It then tracks the storms east and a little north of east overnight with a suttle shift east and then finally southeast as the storms become primarily outflow dominant. This should bring at least VCTS to PIA and BMI in the 12-15z time frame. This outflow boundary will be the key for any redevelopment late in the afternoon, and once again, the favored areas will be PIA and BMI, but again, this far out, will handle with a VCTS during the time frame redevelopment is expected. Otherwise, scattered to broken cumulus will develop again by early afternoon and then quickly dissipate just after sunset. Southeast to south winds tonight at 8 to 13 kts will be south on Saturday at speeds of 10 to 15 kts with a few gusts near 20 kts at times in the afternoon. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Smith SHORT TERM...HJS LONG TERM...HJS AVIATION...Smith
Area Forecast Discussion
National Weather Service Key West FL
946 PM EDT Fri Aug 31 2018 .CURRENTLY... Shower and thunderstorm activity has decreased over the early evening hours. A few showers with embedded thunderstorms can be found in the eastern straits, and showers and storms in the Gulf waters south and west of the lower Keys. The evening Key West sounding again found ample conditional instability with abundant MLCape. Although the PW is still over 2 inches the mid-level RH values are slightly lower than the past several evenings, and lower tropospheric lapse rates are not impressive. Upper level winds have shifted more out of the northwest from northerly earlier, so the lower Keys are no longer under the thick cirrus seen earlier today. However, the upper Keys are still shrouded in cirrus from storms in the Gulf. Easterlies dominate from the surface through 20 kft, indicating the depth of the ridge. .SHORT TERM... Guidance analysis finds the mid-levels continuing to dry slightly, with the RAP indicating RH percentages in the convective layer (700-500mb) dropping into the 40s by Friday afternoon. The relatively drier mid-level air is moving through in advance of the tropical wave expected to traverse the area on Labor Day. Overall MOS guidance does reflect the above with lower precipitation chances (near climo) than previous runs for Friday and Friday night. Additonally, the HRRR and the Key West local WRF are not very bullish on widespread precipitation coverage overnight and tomorrow. The pops currently advertised for the next 24hrs may be slightly overdone, but are in chance category which is probably appropriate. && .MARINE... Gentle to moderate easterly breezes can be expected overnight and Friday morning over Hawk Channel and the Florida Straits, with gentle easterly breezes expected over the Gulf and Florida Bay. Thunderstorm and shower coverage will be isolated. Storms that do develop will be moving towards the west northwest between 15 and 20 knots. Winds in the vicinity of thunderstorms could gust near 25 knots. && .AVIATION... VFR conditions to prevail at both terminals with a few showers in the vicinity this evening. East-southeast winds should settle around 10 knots tonight, becoming gusty again tomorrow. Short term trends and high resolution models suggest a mainly quiet night, with convective coverage perhaps ramping up again by mid-morning. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...Devanas Aviation/Nowcasts....CLR Data Collection......SD Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest
Area Forecast Discussion
National Weather Service Midland/Odessa TX
602 PM CDT Fri Aug 31 2018 .DISCUSSION... See aviation discussion below. && .AVIATION... VFR conditions are expected at the west Texas and southeast New Mexico terminals the next 24 hours under mostly clear skies. Any thunderstorm activity should remain in the mountains. 12 && .PREV DISCUSSION... /issued 308 PM CDT Fri Aug 31 2018/ DISCUSSION...As of 3:00 PM CDT Friday...after I looked at the models I had to rub my eyes a couple of times and find my glasses. Could it be true? Yes...rain and cooler temps are in store for the latter part of the holiday weekend and thru most of the upcoming week! A very nice respite from the interminable heat we have been experiencing for months and months and months. Now on to the fun details! KMAF radar is showing a few storms popping up in the Davis and Guadalupe Mtns...likely due to the intense heating...moisture... and upslope flow. Even though the HRRR doesn`t have a good handle of the current conditions the high resolution NAM Nest CAM model is doing well. Simple Water Vapor RBG imagery shows the ridge centered over North Texas stretching east to the Atlantic. Any storms will dissipate overnight. The long awaited (seems like many months) and welcome pattern change begins this weekend as the westerlies make their way south. Due to the large scale (synoptic) pattern change have mainly followed the ECMWF. On Saturday the ridge center shifts to the NC/VA coast as a trof deepens over the Rockies. It will still be hot on Sat as the H85 thermal ridge edges closer. Slt chc/chc pops will spread slowly east thru Sat night...mainly over the mountains but moving further into the adjacent Plains as lift increases. On Sunday the ridge moves off the mid Atlantic coast as the trof deepens in the Rockies and edges into the Plains. Lift ahead of the trof and subtropical moisture being advected into the area will lead to a chance of thunderstorms across the area. Most...if not all of next week looks wet with high temps in the 80s! The basic pattern will be a trof over the Western US with a ridge over the Eastern US. A continuous feed of deep subtropical moisture and impulses traveling out of Mexico will keep showers/thunderstorms in the forecast thru the week. The ridge starts to build west from the mid Atlantic into the Central Plains by Thursday morning leaving the CWA in a deep moist southeasterly flow. What is interesting to see...and this can change a number of times...is that the ECMWF takes the weak tropical wave that is near Hispaniola into the Gulf of Mexico and moves it west. If this does verify it could add to the deep moisture over the area and enhance the rainfall. The ridge center remains north of the CWA allowing inverted trofs to move west over the CWA for a continuation of the wet weather along with comfortable temps. Bottom line is that it looks like a wet week ahead. Did consider a Flash Flood Watch starting Sunday Night/Labor Day...but as of now it seems like the the heavier rain will occur Tuesday thru Thursday. The overnight shift will review the necessity of a Watch. Will continue with the Special Weather Statement for now. Strobin && .PRELIMINARY POINT TEMPS/POPS... Big Spring 74 97 74 93 / 10 10 10 20 Carlsbad 70 96 68 90 / 10 40 50 40 Dryden 74 98 74 95 / 10 10 0 30 Fort Stockton 71 97 72 91 / 10 10 10 40 Guadalupe Pass 67 89 65 84 / 20 30 50 40 Hobbs 68 91 66 86 / 10 10 50 30 Marfa 60 88 61 84 / 10 20 20 50 Midland Intl Airport 73 97 73 92 / 10 10 10 30 Odessa 73 96 73 91 / 10 10 10 30 Wink 72 99 73 92 / 10 10 30 40 && .MAF WATCHES/WARNINGS/ADVISORIES... NM...None. TX...None. && $$ 84/33
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
731 PM CDT Fri Aug 31 2018 .SHORT TERM...(This evening through Saturday) Issued at 405 PM CDT Fri Aug 31 2018 It`s looking more and more likely that scenario 1 from this mornings discussion will be playing out tonight, which is a split setup with the local area between better upper forcing to the north and better LLJ forcing to the south. This leaves us with very little forcing in between. We see this split setup with the most recent Day1 outlook from the SPC and have started pulling back on PoPs. This afternoon, satellite imagery shows plenty of accas moving across the area with steep mid-level lapse rates and broad waa/isentropic lift. To this point none of this activity has been able to tap into the instability in place (about 3k j/kg of muCAPE) as it is riding above the instability. However, we are seeing a few drops reach the ground from this activity and you can`t rule out one our two storms managing to form out of the accas, so had to spread some 20 pops across much of the area this afternoon as this accas works through, but we aren`t expecting anything widespread or well organized to develop. Where convection has developed just before 3pm was just west of I-29 on the ND/SD border. The HRRR did a decent job in pegging this (though the HRRR was a little late in initiating it), and agree with the HRRR and the other CAMS that this activity will follow the h85- h3 thickness pattern (mean flow) ENE toward DLH, just grazing our northern CWA. This activity will pose the greatest severe risk, with wind and hail being the main threat. Also showing up nicely on satellite is a strong shortwave coming out of Colorado. This wave will move into the central Plains this evening, exciting a strengthening of the LLJ this evening down by Omaha that will move across IA overnight. This should initiate widespread convection with torrential rainfall across Iowa into southern WI. The main question with this LLJ forced activity is how far north does it develop. We are seeing from the HRRR/NMM/ARW that it may sneak up to I-90. So what does that leave us in between? Broad WAA with associated weak isentropic lift. There really isn`t any forcing mechanism that looks to focus activity in the MPX area (unless the Iowa activity makes it to I-90), which means we get isolated to scattered storms depending on where we get enough forcing to break through the cap. In all likelihood, our QPF is way overdone and spreadout with the widespread 3/4ths to 1 inch of QPF east of a STC/MKT line. Instead, we`ll see a few streaks with amounts like this or even better, but it`s tough to pin down where any of those streaks will end up at this point. For Saturday the best moisture transport shifts south, aligning from KC toward Milwaukee, so the precip focus shifts southeast of the MPX area. This will give us a dry day, though with the tropical dewpoints not really leaving the area, it will be muggy and we`ll likely hold on to a bit more cloud cover than we were previously expecting. .LONG TERM...(Saturday night through Friday) Issued at 405 PM CDT Fri Aug 31 2018 The long term period can be characterized by an active and stagnant weather pattern in which a broad trough/zonal pattern across the western CONUS will place us in southwesterly flow which will bring repeat rounds of shortwave energy through the Midwest. Additionally, a frontal boundary will linger, wavering slightly northward and southward with time, across the region which will provide a focus of low level lift with moisture pooling along the front, leading to repeat thunderstorm opportunities. Saturday night and Sunday...this period will start out rather quiet with all of the thunderstorm activity expected in the vicinity of the frontal boundary to our south. There are some differences for the forecast for Sunday, but the GFS is showing a shortwave lifting northeast from Nebraska, leading to showers and storms across our area. The EC keeps most of this activity farther south, more closely tied to the frontal boundary. Pops were raised to the around 50 percent for much of the area Sunday. Sunday night through early next week...A fairly stagnant evolution of the pattern and hence the front across Iowa, southern MN and into WI is expected during this period. Ample moisture and instability will remain pooled along this front which will start out just to our south, but slowly lift northward Monday into Tuesday. Each night will bring more rounds of thunderstorms along the front as the nocturnal low level jet increases. Hence, the WPC has QPF values on the order of 3+ inches over the next 7 days across a fairly widespread area, which is reasonable. There will no doubt be higher amounts on an isolated basis through the period. The guidance does suggest a reprieve comes Wednesday as dry high pressure drops in from our south and pushes the frontal boundary south of the area. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 731 PM CDT Fri Aug 31 2018 Most of the area is indeed in the middle of a split scenario tonight with thunderstorms. There will be storms this evening from northeast into portions of east central MN and adjacent WI, with the best forcing associated with the upper jet across northern MN. Meanwhile there may be storms later tonight from southeast MN into WI associated with the low level jet and warm air advection. In between, just some scattered showers and maybe an isolated storm. Otherwise, MVFR ceilings are possible late tonight in eastern MN into WI, and possibly IFR ceilings as well. KMSP...a few light showers are possible this evening around the airfield, but it is unlikely there will be any thunder tonight within 50 nautical miles, as best forcing remains well north and south of KMSP. Having said that, with some instability and weak warm advection, one cannot completely rule out seeing a brief TS, though we are not really seeing a threat for anything organized impacting the Twin Cities. Also, there should be abundant stratus toward morning with plenty of moisture along the weak boundary. /OUTLOOK FOR KMSP/ Sun...VFR. Chc TSRA. Wind S at 5 kts. Mon...MVFR/IFR with -SHRA/TSRA possible. Wind E at 10G15 kts. TUE...VFR. Chc TSRA. Wind SW 10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...MPG LONG TERM...SPD AVIATION...TDK
Area Forecast Discussion
National Weather Service Tucson AZ
209 PM MST Fri Aug 31 2018 .SYNOPSIS... A brief return to the monsoon can be expected this weekend, with a return of moisture to southern Arizona. The best chances for isolated to scattered showers and thunderstorms can be expected mainly from Tucson eastward to the New Mexico border. && .DISCUSSION... Clear skies this morning led to quick warm up around the region, priming the atmosphere for convective initiation off the Chiricahua Mountains this early this afternoon. This is in line with earlier HRRR and U of A WRF solutions. Looking at satellite imagery, an upper level trough can be seen digging into northern California, with an upper level jetlit swinging around the southern edge moving into western Arizona. This will be the main driver for convective activity through this weekend, as the trough flattens and moves eastward into the Great Basin. This will enhance the southwesterly flow at the lower levels, provide moisture and be the focal point for precipitation Saturday and Sunday. Based on the moisture profiles aloft, the activity should be confined to the southeastern portion of the state. By Tuesday, the precipitation chances dwindle and daytime high temperatures will be in the mid 90s across the lower elevations. && .AVIATION...Valid through 02/00Z. SCT-BKN clouds at 8k-12k ft AGL. Isolated to scattered -TSRA/-SHRA will continue through the evening mainly near the higher terrain and along the International Border from KOLS to KDUG. SWLY/WLY SFC wind at less than 12 kts this evening, except near TSRA where gusty outflows will be possible. More scattered -TSRA/SHRA are expected to develop Saturday morning into the afternoon hours. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...A slight chance of thunderstorms mainly near the mountains and along the International Border through this evening. An increase in shower and thunderstorm coverage will occur this weekend, but some drying is expected again early next week. Expect terrain driven 20-foot winds at less than 15 mph, except brief strong gusts near thunderstorms. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ MJS/JKP Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson