Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/14/18

National Weather Service Kansas City/Pleasant Hill MO
721 PM CST Sat Jan 13 2018 .Discussion... Issued at 719 PM CST SAT JAN 13 2018 Surface ridge in place over the forecast area keeping things chilly this Saturday afternoon. This ridge will shift east with time, which will get some southerly winds moving into the area through the overnight period. This warm air advection should start a moistening process that will get the atmosphere primed for some light snow to form once a shortwave trough moves into the area from the northern High Plains. In the mid levels northwest flow continues to dominate the area, as it has most of this winter. Radar echoes and IR imagery indicates an area of light snow over western South Dakota and NW Nebraska. The mid level ascent associated with this area of light snow will make its way into northeast Kansas and west Central Missouri later tonight. Timing of this wave is a bit in question still, with the NAM/GFS indicating snow starting in the area after midnight, lasting through mid morning Sunday. The HRRR has been fairly consistent with bringing the wave and precipitation into the area a couple hours earlier than the NAM. Will need to watch this carefully, but the early indication of the HRRR might have some difficulties considering the dry low levels that any snow will have to compete with before saturation. Moisture will be limited and the duration of lift will be rather short, relegated to around 3-5 hours, therefore QPF for this Sunday morning system will be very light, on the order of around .05" across the advisory area. Snow ratios around 15 to 20:1 will yield amounts around an inch, with some areas perhaps seeing 1-2 inches before the quick hitting system moves out of the area by Sunday afternoon. A second round of snow will move into the area Sunday night into Monday morning. While this system isn`t expected to bring much in the way of new snow, it may be a bit more widespread with accumulations. In the mid levels another weak shortwave trough will glide through the area from the north/northwest. A surface and low level ridge will plow through the area, bringing stiff northerly winds. Mid level frontogenesis will bring a second quick hitting period of snow Sunday night into Monday morning. Once again, considering the moisture limitations and short duration of snow, only expecting around an inch to 2 inches with this round of Monday morning snow. All told with these two systems we can expect roughly 1 to 3 inches of snow across most of the area, with the western half of the CWA seeing slightly more snow than the eastern half. Winds remaining in the 10 to 20 mph range with very cold air moving in behind the low level cold front will bring wind chills down to around 15 to 25 below across far northern Missouri and down to around 15 below along the I-70/MO River corridor Monday night into Tuesday morning. The middle part of next week looks to be dry as high pressure settles into the low levels. This ridge will keep temperatures cool for Tuesday and Wednesday. By Thursday mid level ridging moves into the area, with some western low level troughing, which will bring a warm up into the Thursday/Friday time period. Expect Thursday to finally reach above freezing, with Friday being perhaps 5 to 10 degrees above normal. A closed low in the mid levels should veer south of the forecast area on Friday, but there is a potential for some clouds and maybe a low chance for some light rain across the far southern CWA as this system passes to the south. A more significant system is possible toward next weekend, as models continue to show a trough coming on shore and eventually ejecting into the plains. Timing/location/intensity of this trough is very much in the air, so will forego details this far out, but it`s a system that bears some watching as we go through next week. && .Aviation...(For the 00Z TAFS through 00Z Sunday Evening) Issued at 513 PM CST SAT JAN 13 2018 The main impact through the forecast period will be in the form of light snow during the overnight hours through early Sunday morning. Initial overhead precip prior to 06Z should evaporate given existing dry lower levels. This will eventually be overcome with precip making its way to the surface shortly after 06Z, while increasing in coverage near 09Z - 10Z. Ceiling heights will degrade to MVFR during this time, with IFR visibilities also possible Sunday morning. Conditions will gradually improve by the late morning. A secondary round of snowfall is then possible Sunday night. && .EAX WATCHES/WARNINGS/ADVISORIES... KS...Winter Weather Advisory from midnight tonight to noon CST Sunday for KSZ025-057-060-103>105. MO...Winter Weather Advisory from midnight tonight to noon CST Sunday for MOZ028-029-037-043-053. && $$ Discussion...Leighton Aviation...Welsh
Area Forecast Discussion
National Weather Service Hastings NE
702 PM CST Sat Jan 13 2018 .UPDATE... Issued at 654 PM CST Sat Jan 13 2018 Adjusted the snow totals ever so slightly mainly just sliding the 1-2" and 2" snow band about 10-15 miles southwest based on current radar trends and the HRRR being slightly further southwest. The most likely location for the slightly higher 2" or just a little bit over 2" band by late tonight should run from around Hastings and Grand Island to around Hebron. UPDATE Issued at 537 PM CST Sat Jan 13 2018 Forecast seems reasonably on track for the snow this evening. Am considering sliding the snowband slightly further southwest based on the trends in the HRRR model and actual snow band location as it`s beginning to form now over the sandhills. Any shifting of the snow band further southwest would probably be rather minor at only a 10 to 15 mile shift. Will continue to watch radar trends and make possible adjustments to our snow forecast as we head through the evening. Overall the 1-2 inches in the primary band through the heart of our forecast area from northwest to southeast looks good with some isolated 3 inch amounts possible. A south wind at 5 to 15 mph averaging around 10 mph is light enough to not have much of an impact. && .SHORT TERM...(This evening through Sunday) Issued at 246 PM CST Sat Jan 13 2018 Forecast is still mainly on track with a few nudges made. I increased POPS and snow amounts a bit as there seems to be increasing agreement in short term models. We could even see a few three inch reports, but this depends on where the mid-level jet streak axis winds up being with the associated low-amplitude wave. The bulk of any snow should be late evening and early overnight. Lows tonight will be in the 11-14 range early and will rise overnight as anticipated as a warm front approaches. Our quick break from the cold still on track for Sunday with highs in the mid 30s to lower 40s, but I went a bit more pessimistic for highs and with with CONSshort. .LONG TERM...(Sunday night through Saturday) Issued at 246 PM CST Sat Jan 13 2018 Arctic air make another return with more snow possible with the cold push, with possibly some brief sleet in transition from rain to snow. Snow amounts do not look like a whole lot, but wind chills could be pushing -30 Monday morning. Wind chills look like they will be in the -15 to -20 range Tuesday morning. Another modest warmup is on the way toward the end of the long term. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday) Issued at 537 PM CST Sat Jan 13 2018 The main concern will be the accumulating snow with most of it falling this evening/tonight between 7pm and 2am. Visibility will likely bounce around as the snow intensity varies but should range from around 1/2 mile up to around 3SM through most of the event. Ceilings will also fall with the snow into at least low end MVFR and possibly into IFR range at times. Everything improves as the snow ends and we near dawn. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ UPDATE...Wesely SHORT TERM...Heinlein LONG TERM...Heinlein AVIATION...Wesely
Area Forecast Discussion
National Weather Service Paducah KY
730 PM CST Sat Jan 13 2018 .UPDATE... Issued at 730 PM CST Sat Jan 13 2018 For now, am not planning on changing our low temperature forecast. Some guidance, especially the RAP and CMC suggest below zero numbers over snow cover. Tough call with dew points still 9 to 14 degrees many areas, coupled with 800mb moisture and associated mid clouds moving ESE across the area. Best course of action is no action at this point. We did have to raise hourly temps through 08z as we are not falling as fast as forecast. However should we have a late night period of mostly clear, then we could achieve our going lows. CN UPDATE Issued at 521 PM CST Sat Jan 13 2018 Aviation update. && .SHORT TERM...(Tonight through Monday night) Issued at 253 PM CST Sat Jan 13 2018 First question is just how cold will we get tonight? Some guidance has us mostly clear to partly cloudy, with others bringing in more clouds, but with all showing light to calm winds. Any areas with snow cover along with clear skies for any time will see a big drop in temperatures. This makes tonight`s low challenging. In areas with less snow cover and the better chance of more clouds, basically west of the Mississippi River, went with lows from 5 to 14 degrees. For the rest of our area, went with lows from around zero to near 5 above zero. On Sunday, a weak upper level trof may allow some light snow/flurries to skirt the Ozark foothills of Missouri Sunday morning, but the main effect will be increasing clouds from the west. Approaching low pressure will shift our winds to the south through the day Sunday. Temperatures will still only reach the middle to upper 20s for highs, but the south winds Sunday night will keep temperatures up, with lows in the lower 20s. The approaching low will give our northern counties a chance of light snow Sunday night, but the main show will be Monday into Monday night. As the low slides to our north, the associated cold front will spread light snow across our region from the northwest through the day Monday. The best chances will be across southern Illinois, southwest Indiana and northwest Kentucky Monday afternoon, and across west Kentucky Monday evening. Any lingering chances will be confined to our southeast counties late Monday night. Overall, models show the front moving through fairly quickly, which should help keep snow amounts less than yesterday`s event. At this time, expected snowfall amounts are in the 1 to 2 inch range across our northern half of counties, to a half an inch to an inch in west Kentucky. Southern portions of southeast Missouri may see only a few tenths. High temperatures Monday will be in the 30s, and our southern counties may see a rain/snow mix for a few hours in the afternoon with temperatures above freezing, thus lowering snow amounts. Colder air will be quickly filtering in behind the front. Lows Monday night will drop back into the single digits for most of the region. Wind chills will be potentially dropping into the zero to fifteen below zero range. .LONG TERM...(Tuesday through Saturday) Issued at 253 PM CST Sat Jan 13 2018 In the wake of a clipper system, skies are expected to clear temporarily, but a scattered to broken stratocumulus deck will probably reform by Tue afternoon mainly over the Evansville Tri- State region. These clouds should linger through at least Wed morning as a mid level trof axis moves into TN. Another frigid airmass will sweep into the PAH forecast area behind the front on northwesterly winds. By Wed afternoon, the center of Arctic high pressure will be in our vicinity. As a result, with snow on the ground, highs Tue and Wed will be in the teens and lower 20s, with lows in the single digits to mid teens. The coldest morning will be Wed, with negative single digit lows east of the MS River. These numbers, which we are fairly confident about, are before wind chill calculations are applied. An wind chill advisory should eventually be issued for wind chills Tue and Wed morning ranging from -15 northeast to -5 southwest. Some moderation in temps/dewpoints should be seen by Thu afternoon, as temps may rise above freezing over southeastern MO and parts of western KY/southern IL under brief ridging or quasi-zonal flow aloft. By then, southerly low level winds are forecast to start up on the backside of the surface high. The medium range models have understandably had a bit of difficulty with the position/evolution/timing of a tight low pressure system that may develop in the Gulf Coast region by late in the week. However, this system may not affect us at all. Increased moisture transport from the Gulf does look pretty likely by Sat ahead of a large trof developing across the Rockies and central Plains. While the warmup continues, there will be increased cloudiness and perhaps some light rain showers on Day 7 (Sat, with a chance of a wintry mix early. && .AVIATION... Issued at 521 PM CST Sat Jan 13 2018 VFR conditions tonight through Sunday. Occasional mid clouds are forecast. Light north winds will gradually become south, southeast tonight through Sunday. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ SHORT TERM...RST LONG TERM...DB
Area Forecast Discussion
National Weather Service Raleigh NC
740 PM EST Sat Jan 13 2018 .SYNOPSIS... Chilly high pressure will build into the Carolinas through the rest of the weekend. This high will retreat to our northeast Monday, bringing more seasonable temperatures on Tuesday. A strong upper level trough and associated cold front will cross the region Tuesday night through Wednesday night. && .NEAR TERM /THROUGH TONIGHT/... As of 740 PM Saturday... Stratocumulus layer is thinning as it tries to spread south and west concurrent with the dry surface ridge oozing down the Atlantic seaboard. Have made some tweaks to current coverage and trend towards clear by sunrise per forecast soundings off the HRRR and RAP. Dew points are running a couple of degrees below forecast, so some minor tweaks there. Otherwise...steady as she goes. Previous Discussion: A complication has popped up for this evening`s forecast. The surface trough is currently moving SE of the forecast area, with periodically gusty NW winds and falling dewpoints in its wake. Meanwhile, another low level boundary, evident on high-res visible satellite imagery, extends from south central VA along the Roanoke River basin southeastward to the central Outer Banks, pushing toward the S and SW. Stratocu lingers both ahead of and behind this feature, within a diffuse front and zone of weak low level convergence evident at 900-850 mb, and we`re even seeing some spotty light rain and drizzle at Ahoskie in the last hour. This moisture is trapped beneath a growing subsidence inversion aloft and near the top of a well-mixed surface-based layer, and with weak flow through that layer, it`s lacking any opportunity to disperse horizontally, too. The GFS has been consistently showing this deck of clouds pushing SSW into central NC through this evening, and now the recent HRRR runs depict it as well, even showing deep enough moisture for a little precip at the ground over the NE Piedmont around mid evening. And based on the HRRR forecast soundings, with little to no ice in the cloud and with falling surface wet bulbs as colder air rushes in, whatever falls may transition from patchy drizzle to patchy freezing drizzle in some areas. In any case, anything that might make it to the ground would be extremely light and short-lived. Have added a brief period of patchy drizzle along this feature from now through mid evening from the NE CWA southwestward through the central Piedmont. Otherwise, expect partly to mostly cloudy skies over the N and E CWA through evening, trending toward gradual clearing overnight as drier air is entrained in the low levels. Lows 20-26, with some teens likely in the normally colder areas. -GIH && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... As of 240 PM Saturday... The weakening mid level shear axis will be heading to our east Sun morning, as the cold surface high noses in from the N. The column is projected to be stable and quite dry, and expect plenty of sunshine Sun. Taking the 925 mb parcel down to the surface dry adiabatically yields highs of 33-41, very close to the earlier forecast and statistical guidance. A slug of moisture aloft and weak mid level DPVA arrives late Sun night from the SW, so expect a few high clouds to streak into the area from the SW overnight. Lows 14-20. -GIH && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 230 PM Saturday... A initially strongly positively-tilted, and similarly strongly meridional trough aloft, will pivot across the MS Valley Mon-Tue, then to the East Coast while assuming a neutral tilt, by Wed-Thu. Forecast details in the Tuesday night to Wednesday period continue to evolve with latest model guidance. At the surface, increasingly modified Arctic high pressure will be in the place from Atlantic Canada to the sern US early next week, while an occluding clipper low will have migrated to the Great Lakes through Tue. Along the trailing Arctic front, an initially flat, triple point wave will meanwhile develop from the mid MS Valley to the cntl Appalachians through Tue. A warm front preceding the triple point is expected to cross cntl NC Mon night, but not manifest as a noticeable increase in surface temperatures until diurnal heating on Tue. The Arctic boundary is then forecast to collapse east of the Appalachians and across cntl NC Tue night, with following Arctic high pressure that will build into, and modify over, the sern US through the end of the week. Strong jet dynamics and deep layer frontogenesis accompanying the upper jet/front and related low level frontal zone should be sufficient to support at least a light precipitation event over cntl NC Tue night-Wed. That precipitation would likely fall in the form of light rain or rain mixed with snow early Tue night, since temperatures will have warmed considerably, into the upr 40s to lwr 50s for most Tue afternoon; and the models are typically too quick in surging cold air masses east of the cntl Appalachians of VA/NC. However, partial thickness values and boundary layer temperatures are both forecast to become supportive of a west to east changeover to snow late Tue night into Wednesday. If the trough aloft is weaker and more positively-tilted as it approaches NC, then a light rain, to inconsequential snow event would result. Temperatures are expected to otherwise turn colder by Wed, before moderating to around or slightly above seasonal normals by the end of the week. && .AVIATION /00z SUNDAY THROUGH FRIDAY/... As of 620 PM Saturday... 24-Hour TAF Period: High confidence VFR conditions will persist through the TAF period as high pressure builds into the area. Some mid clouds around 5 KFT will pass over KRWI and possibly KFAY and KRDU, otherwise some lingering high clouds are expected into tonight. Some drizzle may occur with the mid-clouds, but conditions should remain VFR. Northwesterly winds will remain in the 5-10 kt range overnight, but will vary from northwesterly to north- northeasterly. -KC Looking ahead: Chilly high pressure will extend into the region through Mon, with VFR conditions. Next chance for sub-VFR conditions will arrive Tue into Wed as a potent upper level trough slowly crosses the region. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield/mlm SHORT TERM...Hartfield LONG TERM...MWS/Franklin AVIATION...Hartfield/KC