Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/06/20


Area Forecast Discussion
National Weather Service Bismarck ND
832 PM CDT Sun Apr 5 2020 .UPDATE... Issued at 832 PM CDT Sun Apr 5 2020 Latest summary of radar sites across the region continue to show isolated showers south central through the James River Valley. Harvey had a brief period of mixed precipitation, rain/snow per Carrington BUFKIT sounding and surface observation. Will continue to see this trend over south central and the James River Valley through 06z as mentioned in the previous discussion. Threat for thunderstorms appears to remain in South Dakota, but will watch for any changes. For now, will maintain showers without a mention of thunder in the gridded forecast. Stratus/fog forecast remains on track this evening (beginning around 04z) and through Monday morning. It is possible the stratus will linger over the James River Valley well into Monday afternoon per RAP13 925mb relative humidity field. UPDATE Issued at 556 PM CDT Sun Apr 5 2020 Latest water vapor satellite imagery shows southwest flow aloft with an initial 700mb shortwave trough now sliding through the northern James River Valley. Surface observations and radar reflectivities over this area show clouds are based between 9000ft and 11,000ft above ground level, and no precipitation has reached the surface; cloud bases just a tad too high. Looking farther upstream, clouds are developing along with increasing radar reflectivities over south central as a few more mid and upper level shortwaves approach this evening. SPC has a general thunderstorm outlook/non- severe across south central and the James River Valley tonight. Surface low associated with a shortwave in southwest South Dakota will scoot into north central South Dakota by 06z Monday. Comparing current surface based cape and most unstable cape from SPC mesoanalysis to the NAM/GFS, both seem to capture the 100-500J/Kg of cape across western South Dakota. The NAM takes this area of instability up to and over our border by around 06z, about 200 J/Kg. The GFS dampens/washes the cape out to less than 100 J/kg along and south of our border by 06z. Low level lapse rates appear meager at this time and are forecast to continue through the evening, however mid level lapse rates remain sufficient at 7.5C/Km. The HRRR simulated composite reflectivity is the most aggressive in generating the highest reflectivities compared to the remaining high resolution guidance; however there is agreement that some precipitation will develop south central and into the James River Valley now through 06z Monday. Based on current radar trends agree with this scenario, and will expand current PoPs to account for this. Will hold off on thunder mention with this update and monitor the upstream radar trends and observations before adding thunder to the grids. Stratus and fog as mentioned from the previous discussion continues to have support from the high resolution guidance and BUFKIT soundings. Continued easterly flow/upslope will result in stratus/fog to form north central this evening, then expand south overnight. && .SHORT TERM...(This evening through Monday) Issued at 246 PM CDT Sun Apr 5 2020 Patchy to areas of fog are again featured for tonight, forming mainly after midnight and slowly burning off Monday. A cool low layer will be over run by warmer temperatures aloft favoring fog formation. There may be a small risk of some patching freezing drizzle late tonight across the James river valley but have not included this yet. few showers will continue across teh James River Valley this evening then end. On Monday, mainly cloudy skies are expected. Increasing southerly winds and moisture will crate some instability, and a few thunderstorms are possible across teh south late Monday into Monday evening. .LONG TERM...(Monday night through Sunday) Issued at 246 PM CDT Sun Apr 5 2020 It will be mild and breezy Tuesday, with highs in the lower 60s across much of southwest and south central North Dakota, and the 50s elsewhere. So by Tuesday evening much of the new snow from this past week will be well on its way to melting. A cold front will pass through Wednesday, and it will be breezy to windy and blustery, with highs just into the lower 40s. However not much in the way of precipitation is expected in the extended. Wednesday, Thursday and Friday expected to be dry, with some chances for light snow Saturday and Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 556 PM CDT Sun Apr 5 2020 Stratus and fog will develop across the northern terminals this evening, 04z-06z Monday, then expand south and east overnight, reaching KDIK/KBIS/KJMS 09z-12z. Expect IFR to LIFR cigs, and vsbys ranging from MVFR to VLIFR, especially at KMOT/KDIK. Improvement to VFR conditions are forecast at KXWA/KDIK by 18z, however cigs at the remaining terminals remain in MVFR/IFR status. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KS SHORT TERM...waa LONG TERM...waa AVIATION...KS
Area Forecast Discussion
National Weather Service Louisville KY
857 PM EDT Sun Apr 5 2020 .Forecast Update... Issued at 856 PM EDT Sun Apr 5 2020 Bumped winds a little stronger over the next few hours to match current conditions and cleared skies just a little. Also, added around a 10% chance of precip in the northern half of our area. The HRRR has been hinting at some light showers forming south of Louisville and moving east expanding as they move into the Bluegrass. Currently, watching light returns over southern Indiana in Orange and Washington Counties. If anything more forms tonight, it will be very light and isolated in nature. Not expecting much. && .Short Term...(This evening through Monday) Issued at 250 PM EDT Sun Apr 5 2020 Surface high pressure centered over Lake Michigan this afternoon will drift east through Monday. Aloft, weak ridging over the eastern 2/3 of the country will combine with the surface ridge to result in clear to partly cloudy skies for much of the forecast area over the next 24 hours. The main exception to this will be areas north of the Ohio River, where low clouds persisted much of the day today. With a weak surface pressure gradient associated with the Lake Michigan high, the low cloudiness will slowly erode rather than quickly move out. Even there, however, Monday looks to see more sun than today. Temperatures will bottom out from 45 to 50 tonight, and in the lower 70s for highs Monday. Those highs will be a pleasant warm-up for southern Indiana, where the clouds held temperatures into the upper 50s for many today. Elsewhere, Monday`s highs will be at or just above today`s maximums, all of which are 5-10 degrees above seasonal norms. .Long Term...(Monday night through Sunday) Issued at 245 PM EDT Sun Apr 5 2020 Unsettled weather looks to start the long term as an upper level shortwave over the northern Great Plains dives SE towards the Ohio Valley. SW winds at the sfc will allow for ample warm Gulf moisture to be funneled into the region, causing dewpoints to rise in the upper 50s to low 60s, with afternoon highs forecast to climb into the mid 70s. Current soundings show relatively steep mid-level lapse rates (7-8 deg C/km), decent instability (1000-1500 J/kgK, along with long hodographs, implying that organized convection may certainly develop. However, this will largely depend on how much we can destabilize throughout the day, so have decided to continue with model blend of PoPs at this time. Another round of showers/storms looks to impact the region late Wednesday night into Thursday morning ahead of a strong cold front. Given the current instability and shear values in place, wouldn`t be surprised if a few of these storms became severe ahead of the line. By Thursday evening, the aforementioned cold front will have exited the region. While a few post-frontal showers may linger in its wake, expect mostly dry conditions and cooler temps to prevail heading into the weekend. A frost/freeze threat may even develop Friday through Sunday morning as overnight lows fall into the 30s. && .Aviation...(00Z TAF Issuance) Issued at 731 PM EDT Sun Apr 5 2020 A weak upper wave and pool of deeper moisture near STL this evening will move to the east and may bring lower clouds and perhaps a small shower or two to southern Indiana and north central Kentucky between midnight and dawn. Down south at BWG clouds should be fewer but that will leave the door open for some light fog to form. Morning low clouds should become VFR over the course of the day tomorrow through lifting and possibly scattering. Winds will be light through the period with surface high pressure in the region. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...KDW Short Term...JBS Long Term...SSC Aviation...13
Area Forecast Discussion
National Weather Service Marquette MI
630 PM EDT Sun Apr 5 2020 .SHORT TERM...(This evening through Monday) Issued at 411 PM EDT SUN APR 5 2020 WV imagery and RAP analysis indicated a mid/upper level trough off the northern CA coast and a broad ridge over the southeastern CONUS resulting in anticyclonic westerly flow through the northern Plains and northern Great lakes. An upstream shortwave trough was moving into western North Dakota. At the surface, high pressure centered over Lake Michigan that has brought sunshine and light winds to the area was slowly moving off to the east. An initial batch or WAA mid/high clouds was sliding through Upper Michigan. Tonight, as the North Dakota moves quickly toward the area, increasing 290k-300k isentropic lift will bring thickening clouds across the area. Some light pcpn may also develop but should not amount to more than a trace or a few hundredths. With the increasing cloud cover, temps should remain mainly above freezing or slowly climb as any pcpn moves in. Since forecast soundings indicate a substantial low level dry layer, evaporative cooling could bring some snow or freezing rain at the onset. Monday, Some lingering WAA/isentropic lift will support the potential for additioinal light rain showers over mainly the east. However, any lift by midday and afternoon will be weak with mainly just sprinkles at the most expected. Temps will rebound into the upper 40s to mid 50s. .LONG TERM...(Monday night through Sunday) Issued at 349 PM EDT SUN APR 5 2020 On the hemispheric scale, not too much change from the past day or so with the above normal temps starting the week becoming near to perhaps slightly blo normal to end the week and into the weekend. Currently, there remains a strong positive height anomaly near Hudson Bay with a weakening ridge across the Pacific that will shift E to the West Coast by the middle of the week. At the same time, troughing remains just off the West Coast and across the Canadian Rockies as well as to the S of Greenland. Over the next few days, ensemble-based forecasts suggest troughing over the West Coast will dig south with a cutoff feature over the desert SW developing, bringing a split flow pattern across the CONUS. Through the middle portion of the week, the Canadian Rockies trough shifts E over the Great Lakes region as a few shortwaves pass over the region bringing a few separate chances for precipitation. Late this week, the cutoff feature shifts E over the southern CONUS and congeals with E CONUS troughing. Heading into this upcoming weekend and into next week, medium range ensembles suggest ridging to persist across the Pacific and develop across the Atlantic. In between, troughing will develop across the central CONUS persisting through the week. Monday night into Tuesday begins with rising heights as a mid-level ridge builds northward. This building ridge is cut short as models suggest a shortwave will approach from the west. Ahead of this wave and an associated sfc trof, isentropic ascent and moisture flux convergence increase as -SHRA develops in the morning across the W and shifting E into the afternoon. Model Q-vector conv suggests that the best forcing remains across the northern half of the UP, though the 12Z GFS brings this forcing across all the UP. Synoptically speaking, still looks like 0.25 to potentially 0.5 inches of rain is possible across Upper Michigan. There is some potential for increased amounts locally in any thunderstorms that develop. GFS still suggests up to 500J/kg of MUCAPE to move into the UP, mainly along the WI-MI state line. NAM has consistently not rendered this solution. Quick look at soundings show this CAPE would be based well off the sfc, closer to 3-5kft...with some positive area still there to overcome. Looks to dry out quickly Tuesday night before the next trough in the line approaches Wednesday evening into Tuesday. This is also the trough that looks to change the above normal temperature trend back towards normal to slightly blo normal. The associated cold front with this trough moves into western UP Wednesday evening as models suggest q vector conv and associated -shra begins on either side of 21Z Wed. As this trof moves through, sfc pres begins to deepen which increases forcing and the instability. Look for an increase in winds through the night on Wednesday and maintaining through Thursday evening. A quick fall in heights, increasing CAA, and colder temperatures aloft will allow the boundary layer to mix quite well with gusts over 30mph appearing likely, esp along the Lake Superior shoreline. Gusts approaching 40 mph are also possible across the eastern half of the UP along Lake Superior and across the Keweenaw. With 850mb temps falling to near -10C, probably won`t see any lake- effect shra/shsn, but drizzle/flurries seem possible. At any rate, it will be gloomy and feel chilly after this week`s warmer temps with plenty of wind and lake-effect clouds around. With the colder air aloft and some CAA still around into Friday, seems likely the UP will be keeping the clouds and maybe some flurries/drizzle around. On Saturday, models suggest another wave to move across Upper Michigan bringing another chance for showers. The EC looks much more impressive than the GFS/GEM at this time, but they all show some showers across the CWA at some point. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 630 PM EDT SUN APR 5 2020 VFR conditions will continue through the forecast period. However, there may be some light rain or snow showers at KCMX and KSAW overnight into Monday. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 411 PM EDT SUN APR 5 2020 Expect light winds of 15 kts or less across Lake Superior through tonight as high pres lingers over the area. Easterly winds will increase to 20 knots Mon as a low pres trough approaches from the west. East to southeast wind gusts could increase up to 25kt over the east and north central parts of the lake on Tue as the gradient tightens ahead of the trough. The next big increase in winds will occur late Wed into Thu as a cold front moves through the area and west winds increase to 20-25 knots late Wed into Wed evening and then become northwest gales of 35-40 knots late Wed night into Thu, strongest over the east half of the lake. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...JAW AVIATION...07 MARINE...JLB
Area Forecast Discussion
National Weather Service Pocatello ID
406 PM MDT Sun Apr 5 2020 .UPDATE... Updated forecast to include isolated thunderstorms with small hail possible across southern Idaho. Radar this afternoon showing convection across the Magic Valley moving northeastward. High resolution models show some thunderstorm potential continuing into the early evening hours. 13 && .PREV DISCUSSION... /issued 204 PM MDT Sun Apr 5 2020/ SHORT TERM...Tonight through Tuesday night. Upper low continues to slowly push into central California tonight through Monday. Southwest flow aloft spreads moisture across East Idaho for continued threat of mainly showers tonight and early Monday. Snow levels stay above valley floors, keeping near a high of 7000-7500 ft across a broad swath of the southeast half of the region overnight. Instability increases during the day Monday, with storms strong enough to support at least small hail and gusty winds. An isolated storm may become stronger, but widespread threat for severe storms is not expected at this time. Northern stream trough pushes moisture east late Monday into early Tuesday, but proximity to advancing low could keep precipitation threat going in the southern portions of the region into Tuesday. Otherwise the trend will be for drier conditions for the rest of the region. DMH LONG TERM...WEDNESDAY THROUGH NEXT SUNDAY... Model agreement remains excellent in moderate high pressure providing mostly sunny skies and a taste of spring for Wed through most of Fri. High temps are forecast to rise about 5-10 degrees above climatological norms, especially in the eastern Magic Valley, Snake Plain, and Raft River region, topping out in the 60s in these areas and generally 50s elsewhere. Our official, NBM-led forecast has come down a degree to two compared to yesterday, and still leads the pack by several degrees compared to projections off of some of it`s individual input models such as the GFS and ECMWF. However, it still lies near some decent clustering in the ensembles, particularly the EC, so it appears reasonable. By Fri afternoon, model agreement diverges, and forecast confidence drops off. The Canadian maintains more pronounced high pressure ridging, while the EC starts to wrap a shortwave trough around a closed low in central Canada, brushing at least our eastern highlands with a few showers. The GFS has more of a NW flow moisture signature, also generating a few showers. All 3 of the core long-range models generally feature a wetter picture for the weekend as SE Idaho resides along the western fringes of a Central-Eastern US longwave trough, but there really isn`t any agreement in the details. For now we carry a low- confidence chance of showers both days, along with slightly cooler temps. Assuming adequate lift, the mild temps may help generate enough instability to support some thunderstorms during this period, but did not add thunder to the forecast this far in advance, especially considering the poor model agreement. - KSmith AVIATION... A closed low pressure center near the CA coast will continue to provide unsettled weather and rounds of rain/snow showers. Used the 12z HREF ensemble suite and RAP to try to time out periods of predominant -SHRA, and blanketed VCSH everywhere else through the end of the TAF period. Model-projected lifted indices of -1 to -3 C may support a few thunderstorms this afternoon through 02-03z, especially the further south you go, so added VCTS to KBYI/KPIH/KIDA. Cigs/vsbys should generally remain VFR at these terminals as well as KSUN, except perhaps under a heavier shower/storm (temporarily reduced cigs). Cooler temps may support a changeover to snow Mon morning at KDIJ with possible IFR vsbys and MVFR cigs. MOS and NBM guidance is pretty messy with regard to winds this afternoon into tonight, and the hourly HRRR guidance is convectively contaminated by simulated thunderstorm outflows that may not even materialize, so our forecast confidence in the winds included in the TAF is pretty low everywhere but KSUN, especially for direction. Looking ahead to Mon afternoon, slightly better instability may support a few more thunderstorms, so already introduced VCTS in the longer KSUN TAF. Winds should be slightly stronger Mon afternoon, generally out of the SW. - KSmith && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$