Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/16/20

Area Forecast Discussion
National Weather Service Columbia SC
739 PM EDT Thu Oct 15 2020 .SYNOPSIS... Low level moisture will interact with a cold front moving through the region with chances of showers this evening through Friday. High pressure along with cool and dry conditions will be over the region Friday night through the weekend. Dry weather will continue through the middle of next week. && .NEAR TERM /UNTIL 7 AM FRIDAY MORNING/... Upper impulse in a SW flow aloft, with a weak surface trough over the region enhanced by a sea breeze, with shallow moisture, providing scattered showers and isolated thunderstorms this evening. Overnight, as surface pressure falls across the region in advance of an approaching 500 hPa trough digging into the OH valley, a weak closed surface low is forecast to develop across the upstate, with a weak surface front (manifested mainly as a moisture gradient/wind shift) dragging to its south across the CSRA. This then looks to move into the rest of the CWA between 06z and 10z overnight. Ahead of it, scattered showers will develop within a decently moist environment (PWs 1.4-1.6") and move through the region, exiting northeast around or after 12z. Lows should stay in the mid 60s across the forecast area. && .SHORT TERM /7 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... Upper trough will be moving through the eastern portions of the U.S. on Friday. This will help to push an initial cold front into the area early Friday morning, with lingering scattered showers still possible across mainly central and northern portions of the forecast area. Winds will turn from westerly to more northwesterly through the day. A second stronger cold front will then move through late in the day on Friday, finally drying the entire forecast area out and ushering in the colder airmass for the start of the weekend. Behind the second front, winds turn more northerly with cold advection taking hold. Temperatures through the day Friday will not be as warm in most areas, especially the western cwa, but should still climb into the low to middle 70s. Areas further east where the front will be slower to get too will be able to climb into the lower 80s before the fropa. Significant cool down will occur Friday night through Saturday both Friday and Saturday nights in the mid 40s to around 50. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Forecast will remain dry through the longer term period. Moisture return across the eastern cwa late in the period could lead to an isolated shower or two across the eastern counties, but confidence remains low and have gone dry. Temperatures will be slightly below normal Sunday then return to near normal for Monday through Thursday. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Mid level short wave trough evident over south central Ga toward the lower Savannah river area triggering showers near OGB early this evening where instability has been moderate near surface trough. Mid level capping has limited degree of convection although locally heavy rain has fallen just east of the OGB terminal. Conditions should improve at OGB over the next hour or so with mainly mid level ceilings expected to persist. Pressure ridge offshore overnight with weak surface extending from southeast Ga into the Midlands SC. A cold front will be approaching from the Upstate tonight and should be moving through the area around daybreak. Showers currently near OGB should lift to the northeast as short wave moves northeast. Other showers in the Piedmont and east-central GA should remain mainly west of the terminals. A few showers may develop ahead of the front late tonight but CAM models suggest scattered and mainly focused to the north of the CAE/CUB terminals. Expect strato-cu as the front approaches possibly lowering to MVFR or IFR but lamp and HRRR have trended higher. Visibility should stay up with mixing in the boundary layer. Winds will shift to northwest behind the front with mainly mid level ceilings after 18z. Winds may increase to around 10 knots. EXTENDED AVIATION OUTLOOK...No restrictions expected ad dry air advects into the area. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$
Area Forecast Discussion
National Weather Service Marquette MI
741 PM EDT Thu Oct 15 2020 .SHORT TERM...(This evening through Friday) Issued at 330 PM EDT THU OCT 15 2020 Latest RAP analysis, and GOES Satellite show that closed surface low of 991mb that moved through the UP last night is now south of the James Bay, continuing to move east-northeast away from the region. As tradition being on the back side of a deepening low pressure is that blustery west-northwest winds will continue through the day but slowly diminishing from west to east as the low continues to move away. Lakeshore Flood Advisory will drop off this evening for Alger and Luce Counties as wind and waves should be weaker than earlier today. Mid to upper level analysis still shows an upper level low over northern Canada, which will continue to be a nuisance as this will continue to bring shortwaves to the region. Latest guidance is now showing a weak shortwave moving through Friday, contradicting previous runs of being dry Friday. Another chance for some lake- effect rain or snow showers is possible again with caa taking control heading into the weekend so for those looking for a warmup, doesn`t look likely anytime soon. As this surface low continues to move east-northeast away from Upper Michigan, clouds will hang around thanks to upslope winds from Lake Superior and with caa having a stronghold over the area, most Lake- effect precip will fall in the form of snow over the west-northwest wind belt zones later this afternoon and into tonight with convergence from the land breeze will help aid this, especially east of Marquette. Could end up with some light accumulations across the higher terrain and over the Keweenaw as well. Any accumulations should remain under an inch. Lake-effect looks to hang on, at least according to the NAM and GFS. Drier air will continue to work into the area with high pressure off to the west over the Northern Plains. Heights won`t rise much and barely any waa will work in as the caa hangs on. Hi-res guidance is trying to hint at a weak shortwave for Friday which might trigger light precipitation. There isn`t good forcing or fgen but since given this cooler pattern were in, might be safe to add slight chance PoPs for the daytime. With the winds continuing to decrease throughout today and tonight, will hang onto the Lakeshore Flood Advisory out east since waves take a little bit longer to subside. Winds will become more of a pure westerly direction but will not be as breezy as previous days. Temperatures this afternoon will not rise much, if not at all, just with those northwest winds and lake-effect bands will keep highs pretty much where they are now. Did tweak a few spots a degree or two lower from fcst this morning. Lows tonight will be chilly with mostly 30s with 20s in the interior with help from winds relaxing a bit overnight. Not much rebound for Friday with 850mb temps around -7C, resulting in upper 30s over the west and higher terrain and 40s east and along Lake Michigan. .LONG TERM...(Friday night through Thursday) Issued at 338 PM EDT THU OCT 15 2020 An active weekend still looks to be in the works, as guidance continues to highlight the northeast track of a fall storm through the Upper Great Lakes Saturday afternoon into Sunday. This system looks similar to other recent storms, with strong southerly winds preceding strong northwesterly winds, with widespread precip. The difference is that this storm will already have some cold air in place ahead of it, so some snow is expected. On the backside of this system, a period of lake effect is looking likely into the middle of next week, with some shortwave support embedded within developing zonal flow. Beginning Friday night, the tail end of a shortwave moving through the base of long wave troughing will exit east, giving way to clearing skies for much of the region. The exception looks to be the west wind belts where some lake induced cloud cover and some showers looks to linger through the night. Where skies clear up, light winds will allow for overnight lows to sink into the 20s and the high teens in the traditional cold spots. Attention then turns to the approaching storm. Low pressure developing in the lee of the Montana Rockies will sink southeast into the Dakotas before pivoting toward the northeast through the Upper Great Lakes Saturday night. Strong WAA/isentropic lift ahead of this system will allow precip to spread over the region Saturday afternoon into the evening. Model soundings and wetbulb zero height values indicate precip early in the west half, particularly the higher terrain, could start off as snow. As WAA increases though, all precip should switch over to rain across the forecast area by late afternoon. With high temps topping out in the upper 30s to low 40s, it looks to be a sloppy and dreary kind of afternoon. Models are consistent with a break in the precip, or transition to drizzle/flurries overnight Sat/early Sun as the region dry slots along the southern side of the low. Along the west side of the low, strong CAA will surge cold air south into region, allowing for wrap around precip to switch back over to snow overnight Saturday. Given lake-850mb delta temps of ~16C, lake enhancement is likely within the northwest wind belts of western Upper Michigan. In terms of snow accumulations, an inch or two isn`t out of the question in the west Saturday morning before the warmer air arrives. If this ends up being the setup, I suspect a period in the west where some roads could be sloppy as the snow melts through the day. Another aspect of this storm are the winds. Tightening pressure gradient looks to result in pressure drops of 3-5mb per 3 hours, which will increase southerly winds on Saturday. As the system transits through, increasing CAA and just as sharp pressure rises are anticipated, resulting in strong northwesterly winds. To add to this, some isallobaric wind increases could be realized as the wind becomes perpendicular to the pressure gradient. Overall, expect a blustery winds Saturday through early Sunday, especially by Lake Michigan. The southerly winds off Lake Michigan and the Bay Saturday night could exceed 40kts and a gale watch has been issued for the nearshore waters and the open lake zones for Lake Michigan. These winds will help build large waves and cause lakeshore flooding and beach erosion concerns for the shorelines of Delta and Schoolcraft counties. Following this storm, 850mb temps look to bottom out in the -7 to - 10C range. With these delta Ts, along with low directional shear, lake effect snow showers are looking likely for the northwest wind belts early Sunday. The pattern looks to become more zonal by Sunday afternoon, resulting in westerly flow generally through the early part of next week. A few shortwaves embedded within this flow Sunday night and on Monday could help reinforce any ongoing lake effect. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 737 PM EDT THU OCT 15 2020 VFR conditions should prevail at all terminals through the TAF period. The only exception might be KCMX where an isolated lake effect snow shower moving over the site late tonight/early Friday could briefly lower conditions to MVFR. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 330 PM EDT THU OCT 15 2020 Winds will continue to diminish through the rest of the afternoon, heading into Friday. Current Gales will drop off this afternoon but still could have a few gale force gusts to 35 kts through early evening before winds drop to under 20 kts by Friday morning. With a weak shortwave moving through Friday, winds will be between 15-25 kts from the west then dropping back under 20 kts Friday night into Saturday morning. Then attention turns to next system for Saturday into Sunday. A strong fall storm is progged to transit Lake Superior Saturday afternoon and evening. Current guidance consensus brings the low northeast through the western half of Lake Superior. As the low approaches, southerly gales to 40 knots are anticipated in the eastern half of Lake Superior. Some higher platforms could experience higher gusts given the 45-50knot LLJ that is progged to coincidentally migrate through. These winds could build significant waves upwards of 10ft on the north end of our US forecast zones and into Canadian waters. As the low transits up Lake Superior, winds will become northwesterly gales to 35 knots, mainly in the central and eastern portions of the lake. For the time being, issued a gale watch for the north-central and eastern portions of Lake Superior to account for both the southeast and northwest gale events. Following this event, winds will continue to trend downward beginning Sunday and by Monday, return to westerlies near 20kts lake-wide. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Watch from Saturday afternoon through late Saturday night for LSZ244-245-264>267. Lake Michigan... Gale Watch from Saturday morning through late Saturday night for LMZ221-248-250. && $$ SHORT TERM...JH LONG TERM...JP AVIATION...Voss MARINE...JH/JP
National Weather Service Raleigh NC
959 PM EDT Thu Oct 15 2020 .SYNOPSIS... A cold front will approach from the west tonight and cross central NC early Friday. Canadian high pressure will follow and build across the middle Atlantic later Friday through Saturday, then offshore on Sunday. && .NEAR TERM /THROUGH TONIGHT/... As of 955 PM Thursday... Cntl NC will remain in swly flow aloft tonight, downstream of a broad trough centered across cntl NOAM and anchored by a deep vortex (516 dm at 500 mb) over srn NU. Within that broad trough, a shortwave will amplify into the mid-South and mid MS Valley through 12Z fri, well upstream of cntl NC. More influential for cntl NC will likely be a preceding mid level trough evident in 00Z/16th 500-700 mb upr air and regional VWP data over the Savannah Basin this evening, which is forecast to lift newd across the Carolinas with associated ~30 meter mid level height falls, forcing for ascent, and mid level moist axis. At the surface, a cold front was analyzed at 01Z from cntl PA swwd near the WV/VA state line, far ern TN, n-cntl AL, the lwr MS Valley, and and sern TX; and this boundary will cross the Appalachians and move across the NC Foothills and nwrn Piedmont late tonight. East of the Appalachians this evening, a surface trough and elongated area of low pressure stretched from e-cntl GA, w-cntl SC, and wrn NC, in a zone of related mass/moisture convergence. That pre-frontal low is forecast to develop newd across w-cntl NC between 06-12Z Fri, the last 2-3 hours of which will be characterized by a merger of the approaching front with the pre-frontal trough/low over the nwrn NC Piedmont. Although earlier convection over both the Upstate and e-cntl SC has been weakening during the past few hours, the models continue to suggest additional convection will re-develop along the pre-frontal trough, across the srn and wrn NC Piedmont, by around 06Z. That convection, amidst increasing but still weak instability, should then become increasingly-influenced by low level frontogenesis and mesoscale forcing for ascent as the cold front merges with the low/trough Fri morning, beneath the larger scale ascent and moistening provided by the mid level trough lifting out of the Savannah Basin. The result will be scattered to numerous showers, and isolated storms, overspreading the wrn half of cntl NC and focused between the Triad and Triangle, Fri morning. Rainfall amounts around a quarter inch may be locally maximized around one half inch from near HFF to BUY and former IGX, if training of cells occur where recent HRRR runs suggest. It will otherwise remain mild in the 60s, in light sly to swly flow overnight, with post-frontal CAA likely to send temps into the mid-upr 50s late over the wrn Piedmont, including the Triad. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... As of 225 PM Thursday... A strong cold front will move into central NC early Friday morning and quickly advance through the area by Friday afternoon. A low is expected to develop along the front, over the Carolinas and then be pushed east and offshore with the front. Meanwhile aloft, the upper trough will become negatively tilted as a shortwave swings through the base over the mid-Atlantic. There is still fairly high confidence that a line of showers will move through the area ahead of the front through early afternoon, with the possibility of some thunder in the afternoon. The best PVA aloft will move over the area later Friday eve/night. Also, 925mb and 850mb frontogenesis will be maximized over central NC in the aft/eve immediately behind the front. As a result, some post-frontal light rain will be possible through the evening/midnight, before completely drying out Friday night as the s/w lifts away from the area. Cool high pressure will then build into central NC Friday night. For temperatures, given the current timing of the front moving through the area by Friday afternoon, expect a non-diurnal temperature trend during the day, with temperatures falling behind the front. As a result, the "low" temperature Friday morning may actually be higher than the temperature during the afternoon, especially over the western and northern Piedmont. Highs will range from upper 50s NW to around 70 degrees SE, but as mentioned previously, many of the "highs" will occur during the morning hours. Lows Friday night will drop into the upper 30s NW to mid 40s SE, with the potential for some mid 30s in the usual cool spots. However, the extent of the cooling will hinge on how quickly the skies clear out. Winds will generally remain 5-10 kts through the night with some lingering gusts in the possible in the Coastal Plain. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 330 PM Thursday... Cool surface high pressure will settle into the area from the north on Saturday and Sunday, resulting in dry weather and a taste of autumn. Saturday will be the chilliest day, with high temperatures only in the upper-50s to mid-60s, or about 10 degrees below normal. While thicknesses will be on the rise Saturday night, this should be when the center of the high is most directly overhead, and winds will be lighter. Thus Sunday morning should be slightly cooler than Saturday morning for central NC as a whole, with lows in the upper- 30s NW to lower-40s SE. This could result in some patchy frost, mainly in the northern Piedmont. Highs will increase on Sunday to mid-60s to lower-70s as more easterly return flow results from the high lifting away to the NE. Confidence has increased for the weather pattern next week, with both the GFS and ECMWF coming into much better agreement that an upper ridge will be anchored over the Southeast US. This will keep any fronts well NW of central NC, resulting in mostly sunny skies and minimal precipitation. However, easterly/southeasterly return flow will result in gradually increasing moisture through the week, with dew points in the 60s by Tuesday through Thursday. This combined with weak instability may still result in a slight chance of showers during the afternoon and evening from Tuesday through Thursday, with the best chance across the Coastal Plain. Highs will be near normal through the week, in the 70s, with lows increasing from mid-40s/lower-50s at the beginning of the week to the upper- 50s/lower-60s by the end of the period. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... As of 800 PM Thursday... Initially dry, VFR conditions this evening will yield to scattered showers and the development of MVFR to IFR ceilings late tonight- early Fri, ahead of and along a strong cold front, and abrupt wind shift from swly to nnwly, that will cross cntl NC TAF sites from nw to se; between 08-09Z at INT and GSO and 13-15Z at RWI and FAY. While ceilings are expected to lift to low VFR at INT and GSO prior to 18Z Fri, post-frontal light rain and MVFR-IFR ceilings will linger through most of Fri at RDU, FAY, and particularly RWI, before then clearing by around the end of the 00Z TAF period. Outlook: VFR conditions are expected through early next week, as Canadian high pressure builds across and offshore the middle Atlantic through that time. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...KC LONG TERM...Danco AVIATION...MWS