Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/30/20

Area Forecast Discussion
National Weather Service Boston/Norton MA
957 PM EDT Thu Oct 29 2020 .SYNOPSIS... The remnants of Zeta will bring a soaking rain into this evening along with strong winds near the coast. Rain will change to snow overnight into Friday morning from north to south, even across all of RI into southeast Massachusetts. 1 to 3 inches of snowfall is expected. The storm moves out Friday afternoon. High pressure returns this weekend with dry but chilly weather Saturday, followed by milder conditions Sunday. Early next week will feature dry but colder than normal weather. && .NEAR TERM /UNTIL 10 AM FRIDAY MORNING/... 10 pm update... Precipitation rates have come down a bit over western MA as a slot of dry air has filtered in ahead of the next round of precipitation. HRRR model which has a good handle on the current rainfall is leaning towards less precipitation than expected for the western half of MA through 06UTC. Thus, decided to bring rainfall totals down by about half for this for the 00Z-06Z UTC time frame. Otherwise the previous forecast remains on track. Previous Discussion... Remnant of Zeta now over MD and continuing to move rapidly ENE to south of New England this evening. Some mid level dry air north of the system and as a result seeing the rain shield becoming fragmented over NJ into NYC. Thus may see rain intensity slacken here for a time. However tropical moisture aloft and remnant mid level low associated with Zeta will produce periods of moderate to heavy rain into this evening, then slackening off 00z-03z west to east as remnant low exits east. A chilly rain with temps in the 40s and NE winds increasing as Zeta passes to the south and 1020+ high builds into Quebec, squeezing the pressure gradient. NE winds increase noticeably after 00z with gusts up to 50 mph across Cape Cod and the Islands. Included Block Island in the wind advisory given G50 mph seems likely. Given trees remain fully to partially leaved across this region, low risk for down branches and isolated power outages. && .SHORT TERM /10 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... 425 pm update... *** Accumulating Snow Likely Inland & into the Boston- Providence-Hartford corridor *** Overnight and Friday morning... As remnants of Zeta move offshore, cold air begins to advect on backside across New England, with column cooling from top down. Rainfall intensity decreases later this evening but then picks up again overnight as vigorous closed low over the southern MS Valley advects northeast toward the region. As the cold air deepens rain changes to snow, first across north-northwest MA around midnight and then the rain-snow advances southward into the Boston-Providence- Hartford line toward daybreak. This is when models show mid level banding developing as mid/upper level jet approaches from the southwest. Model qpf has trended upward a bit from previous run which seems reasonable given strong jet dynamics. HREF now showing low prob of up to 1 inch per hour snowfall rates from about 12z-16z across northern portions of CT/RI and MA including the city of Boston. This seems reasonable given the strong mid level banding signature. Initially snow will melt especially on paved surface given current ground temps are in the upper 40s and lower 50s across the area. However impressive cold air advection Friday morning when snow is falling, with all model guidance showing 925 mb temps down to -4C to -5C across northern MA and quickly advecting southward into CT and RI. This will also support a coastal front developing with good cold air drainage down the coastal plain into eastern MA and RI with snow eventually accumulating on all surfaces. The limiting factor for snow accumulations is initially melting snow on the front end and a short duration of moderate to heavy snow, mainly 11z-16z. So while our snow forecast of 1-3" will likely fall short of advisory threshold (widespread 3+"), the combination of roads becoming snow covered during the morning commute, vsby lowering to 1/4 mile at times in heavy snow and the season`s first snowfall, is sufficient support for a winter weather advisory to increase public awareness. In addition, wet roads initially combined with temps falling below freezing Friday morning (interior MA, northern CT into NW RI) may fall into the upper 20s), may yield icy spots as well. Thus likes like a slippery and slow morning commute. Highest snow totals on non paved surfaces. Will have to watch if 3+ inch amounts become more likely, especially on trees, as the heavy/wet quality of the snow combined with trees partially to fully leaved, would increase the risk for down tree branches and possibly isolated power outages. Also next shift may have to expand winter weather advisory eastward into all of eastern MA including Boston if confidence increases on accumulating snow. For the Cape and Islands, precip likely remains all rain other than perhaps ending as a brief period of light snow around midday. Upper air pattern is progressive so precip ends west to east late morning into the early afternoon. Breaks of sunshine possible late from west to east as well. Although not much of a temp recover given strong low level CAA. It remains very windy on Cape Cod and the Islands with NNE winds gusting up to 50 mph. Coastal flooding... Astronomical tides are rather low which will likely preclude any flooding. A surge of 1-2 ft is expected Fri but likely need a surge of 2 to 2.5 ft for minor flooding. Minor splashover is the worst case scenario along east coastal MA. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... 425 pm update... Highlights * A bit of a roller coaster temperature wise in the extended. Much colder than normal Friday night into Saturday morning. Temperatures trend upward through the weekend. This is followed by another shot of cold air early next week. Temperatures trend upward again mid to late in the week. * Light precipitation chances Sunday into Monday. Friday night through Saturday... A trough will initially be over southern New England Friday evening, while a ridge is building over the Northern Plains/Upper Mississippi River Valley. The trough will lift offshore into Saturday morning. The ridge will build into the central Great Lakes/Ontario. The ridge will build over New England on Saturday and offshore by Sunday morning. High pressure will build into the eastern Great Lakes into Saturday morning. The high remains over the region on Saturday before building into the maritimes Saturday night into Sunday morning. High pressure will bring clear skies and really relax the pressure gradient over the region heading into Saturday morning. Aloft -5 to roughly -10 degree Celsius 850 hPa air will advect in due to northerly flow aloft. This in combination with the light winds will result in very strong radiational cooling. Have knocked down the low temperatures toward the 10th percentile of guidance. This results in lows in the teens to low 20s across much of the interior. The coastal plain will see readings range from the mid 20s to the mid 30s. Some spots are still in the growing season, so may need Freeze Warnings in future forecast updates. Temperatures trending upward Saturday and Saturday night. The highs shifts to the east of the region. This will shift winds aloft to a southwesterly direction, which will advect milder air into the region. Still will be colder than normal for this time of year, but dry with highs generally in the 40s on Saturday. Saturday night through Monday night... The ridge builds offshore on Saturday night into Sunday morning, while a trough digs into the central Great Lakes. The trough will continue digging as it moves into the eastern Great Lakes/New England late on Sunday through Monday. At the surface southern New England will remain within the warm sector ahead of a deepening low over Ontario/Quebec late on Saturday through Sunday. The cold front associated with the low will swing through late on Sunday into Monday ushering in another blast of cold air. Throughout this window it appears there could be some light precipitation across the region. Best chance of any appreciable precipitation is over southeast MA late on Sunday into early Monday associated with the cold front passage. This is a result of an influx of PWATs increasing to around 1 due to southwesterly flow. Ptype is expected to be all rain. Though there may be some light snow on Monday into Monday night as things are winding down. Much colder air coming in wake of the front. Will see 850 hPa temperatures falling to roughly -8 to -13 degrees Celsius on Monday into Monday night. High temperatures change from near seasonable temperatures on Sunday (generally the 50s) into the 30s and 40s on Monday. Low temperatures bottoming out on Monday night into Tuesday with readings in the teens and 20s, but the coastal plain will see readings in the upper 20s to low 30s. Tuesday and Wednesday... Drier weather returns Tuesday and Wednesday as high pressure builds in. Still another cold day on tap for Tuesday with northwesterly cold air advection aloft. Temperatures topping out in the 30s to mid 40s. Does appear there will be a significant warm up for mid to late in the week as flow becomes southwesterly advecting much warmer air in. Temperatures rebound into the 50s for Wednesday. May see widespread low to mid 60 degree readings for highs on Thursday/Friday. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00Z update... Tonight... Widespread IFR with embedded LIFR conditions tonight with periods of moderate to heavy rain. Changeover from rain to snow overnight beginning around 9UTC for western terminals and expanding to the eastern terminals and south coast by 12 UTC. Snow may be heavy at times bringing visibilities down to 1/2 mile or less. All rain for the Cape and Islands where there will be gusty winds up to 45 knots out of the northeast. Friday... IFR conditions will gradually improve to MVFR during the early to mid afternoon and eventually VFR by late afternoon as rain and snow showers taper off. Gusty winds will wind down gradually over the same time period before high pressure and light winds settle over the region Friday night into Saturday. KBOS TAF...High confidence in TAF trends. Uncertainty in exact timing. Heavy snow at times possible 10z-16z. Snowfall 1-3 inches possible, highest amounts non paved surfaces. KBDL TAF...high confidence in TAF trends. Uncertainty in exact timing. Heavy snow at times 09z-15z. Snowfall 1-3 inches possible, highest amounts non paved surfaces. Outlook /Friday Night through Tuesday/... Friday Night: VFR. Breezy. Saturday: VFR. Saturday Night: Mainly VFR, with local MVFR possible. Breezy. Sunday: Mainly VFR, with areas MVFR possible. Windy with local gusts up to 30 kt. Chance SHRA. Sunday Night: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA. Monday: VFR. Windy with local gusts up to 30 kt. Monday Night: VFR. Windy with local gusts up to 30 kt. Slight chance SHSN. Tuesday: VFR. Breezy. && .MARINE... 425 pm update... Gale warnings for all waters. NE winds 25-35 kt tonight into Fri morning, except G45 kt across the outer waters from Cape Cod to Block Island. Winds slowly decrease Fri afternoon. Outlook /Friday Night through Tuesday/... Friday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 12 ft. Saturday: Winds less than 25 kt. Areas of rough seas. Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Chance of rain showers. Sunday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 9 ft. Chance of rain showers. Monday: Strong winds with local gusts up to 30 kt. Rough seas up to 10 ft. Slight chance of rain showers. Monday Night: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Rough seas up to 10 ft. Chance of rain showers, slight chance of snow showers. Tuesday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory from 4 AM to noon EDT Friday for CTZ002>004. MA...Wind Advisory until 2 PM EDT Friday for MAZ022>024. Winter Weather Advisory from 4 AM to noon EDT Friday for MAZ002>005-008>012-026. RI...Wind Advisory until 2 PM EDT Friday for RIZ008. Winter Weather Advisory from 4 AM to noon EDT Friday for RIZ001. MARINE...Gale Warning until 4 PM EDT Friday for ANZ232. Gale Warning until 2 PM EDT Friday for ANZ233>235-237. Gale Warning until 11 AM EDT Friday for ANZ230-236. Gale Warning until 2 PM EDT Friday for ANZ231-250-251. Gale Warning until 6 PM EDT Friday for ANZ254>256. && $$ SYNOPSIS...Nocera/BL NEAR TERM...KJC/RM SHORT TERM...Nocera LONG TERM...BL AVIATION...BL/RM MARINE...Nocera/BL
Area Forecast Discussion
National Weather Service Des Moines IA
1001 PM CDT Thu Oct 29 2020 .UPDATE... Issued at 1001 PM CDT Thu Oct 29 2020 Little change to forecast though have brought slight PoPs a bit farther south across the far north. Subjective H850 analysis shows weak wave digging southeast with warm air advection driven light snow over the Dakotas now; some echoes showing up in southern MN and far northern Iowa, but airmass remains dry. As the night progresses, the column will saturate over the north. Cloud depth not very deep and perhaps some light snow/flurries overnight. HRRR soundings at KMCW continue to show small potential for light freezing mist with loss of ice introduction, but with a small dry layer near the surface, impacts should be limited if any. None the less will pass along to overnight shift. /rev && .DISCUSSION.../Tonight through Thursday/ Issued at 259 PM CDT Thu Oct 29 2020 The primary weather themes include mainly dry conditions through the entire period, gradual warming to end the week, somewhat windy conditions this weekend, and above normal temperatures Tue-Thu. There will be minimal hope of appreciable moisture return with our weather influenced by dry northwest upper level flow through tomorrow, and only a brief flip to southwest ahead of the weekend long wave trough passage. This will be followed by a transition back to dry northwest flow before either zonal flow or minor ridging takes hold into the middle of next week. The immediate concern overnight will be the fate of the current stratus central and east, and possibly a very small area of light precip toward the MN border. With the surface ridging approaching, do not expect full clearing until the warm front passes and/or washes out later Friday, and there may even be a few patches of fog overnight in the meantime. Mainly thermodynamic lift 3km and below may brush light precip across the far northeast. Have kept type frozen/snow, but light freezing rain cannot be ruled out as some soundings suggest insufficient moisture depth for ice introduction. Moisture is so suspect that it could very well remain dry this far south as well. By Saturday, our attention will turn toward the long wave trough passage with increasing warmth and southerly flow ahead. Temps should be well through the 50s with breezy south winds. Phased thermodynamic and kinematic lift peaks across our area Saturday morning into midday, but there won`t be sufficient moisture for precip at any level. Strong subsidence than follows into Sunday morning with brisk NW winds expected overnight Saturday through at least Sunday morning. Winds may gust to 30+kts at times on both the warm and cool side of the frontal passage. Looking ahead to next week, warming will commence in earnest with highs back into the 50s Monday after the Sunday cool down. This will be followed by either zonal flow, or weak ridging depending on solution, but regardless will favor weak but prolonged southerly low level flow, boosting highs in the 60s for consecutive days to end the period. All models suggest at least a central/southern Plains short wave passage by Thursday, but deterministic and ensemble solutions differ with regard to the degree of long wave phasing. The vast majority of solutions keep things dry by Day 7 regardless of how things play out, either due to the lack of moisture and/or forcing. && .AVIATION.../For the 00Z TAFS through 00Z Friday evening/ Issued at 619 PM CDT Thu Oct 29 2020 Main focus will be lingering MVFR cigs north this evening. Statocu that developed southeast/east should slowly dissipate aft sunset with MVFR becoming VFR north with time. Otherwise, light winds in place thorugh period with gradual swing to southeast flow between 06 to 12z. Small risk of brief precipitation near KMCW around 12z, otherwise dry entire period. /rev && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...REV DISCUSSION...Small AVIATION...REV
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
949 PM EDT Thu Oct 29 2020 .SYNOPSIS... Drier air will begin to filter into the area behind Zeta starting tonight. A couple shots of cool Canadian air will support below normal temperatures with possible frost/freeze conditions this weekend into early next week. Temperatures start to rebound by the middle of next week, while most locations remain mostly dry through the seven days. && .NEAR TERM /THROUGH FRIDAY/... Evening Update...A line of showers has formed ahead of a llvl convg zone across the ern zones. The line has slowed as it has become parallel with the upper pattern. There are decent rainfall rates, however, the line as a whole is weakening with loss of lift. Don/t envision any hydro issues across the ern zones as that area received the least precip with the remnants of TC Zeta...but will keep an eye on area streams, esp arnd Meck Co over the next couple hrs. The wind adv areas still look good as the LATEST RAP shows a h85 temp gradient developing ahead of the upper trof axis. Decent CAA will aide in bringing stg gusts to the sfc and a few trees may be downed due to moist antecedent conds thru the overnight, mainly abv 3500 ft. 800 PM Update...Issued a wind advisory for NE GA and the wrn NC mtns. Strong forcing from an upper low and some measure of llvl CAA will enable gusts in the 35-40 kt range. Due to the recent heavy rainfall, it/s possible a few trees may be blown down. 730 PM Update...Shower activity continues across the Upstate and srn NC this evening. These cells are moving quickly NE in a strongly sheared environ and have been mixing down winds on the order of 35 kts. Expect these showers to continue across the ern Piedmont over the next few hrs and due to highly moist soils, a few weak trees and limbs could be blown down underneath the stronger downdrafts. 500 PM Update...Starting to see a few cells pop up across NE GA and the western Upstate. The activity is remaining fairly shallow and short-lived for now, but with sfc convg increasing in moderate sbCAPE and a deeply sheared environ...will watch for possible stg development thru the next update. As of 250 PM EDT Thursday: We are now in the calm after the storm so to speak as Zeta has exited the area with breezy and warm conditions in its wake. In fact, we are nearing daily record highs with temperatures near 80 across much of the area. The unseasonably warm and humid weather won`t last! A closed upper low over the lower Mississippi River Valley will merge with the polar jet over Appalachians tonight before pushing offshore into Friday. A weakening front with the closed low will pass through the region from the west this evening with little fanfare other than to maintain some breezy westerly winds at times and perhaps some isolated showers and a thunderstorm or two focused southeast of I-85. A secondary, more pronounced cold front will wrap in behind the departing trough, ushering in much colder air on gusty northwest winds. In fact, strong cold air advection and a tightening surface pressure gradient that becomes orientated more northwest to southeast may support advisory level wind gusts across high mountain elevations tonight. Given the recent rain there is at least some potential for additional downed trees or powerlines for this area. In collaboration with neighbors have held off on a wind advisory for now, but will pass along the potential need to the next shift. Upslope clouds and some shower activity is likely behind the front near the TN border. Overnight lows in the mid 40s to mid 50s will be a good 10 to 15 degree drop off this mornings lows with the dry and gusty conditions making it feel even cooler. Cold air advection will continue into Friday and support only about a 10 degree warm up over the morning lows despite good insolation, with highs in the mid 50s to mid 60s. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... As of 2:30pm EDT Thursday: Saturday and Sunday will be notably cooler with area well behind major cold front, with large dome of high pressure over the eastern CONUS and northerly cold advection just coming to an end Saturday morning. As high pressure moves eastward on Saturday, winds become more northeasterly and brief wedge flow conditions are expected for Saturday night/Sunday, with consequent overcast skies and a slight chance for a little rain or drizzle. Some areas of frost or freeze are possible Saturday morning in higher terrain areas and the foothills, with more widespread frost/freeze possible Sunday night. Temperatures look like they will be 5 to 10 degrees below normal Saturday and Sunday, and this will be a drop of 10 to 20 degrees from levels seen today (Thursday). Currently, only a few of the highest elevation locations are forecast to drop below freezing Saturday morning, and will hold off on a Freeze Watch for the moment. Next front begins to affect northwest parts of the CWA late on Sunday, which should disrupt the CAD as winds become northwesterly. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 2:30pm EDT Thursday: Monday morning may be the coldest point so far this season, with freezing temperatures forecast for all of the higher elevations, and frost possible elsewhere, though frost may be mitigated by wind. Tuesday morning may be slightly colder due to lighter winds, with a better chance for frost all areas. Cold air is courtesy of a synoptic front that passes through late Sunday/early Monday which is associated with a progressive long wave trough. This will usher in much dryer and cooler air for Monday and Tuesday, with moisture beginning to recover on Wednesday. Dewpoints Monday and Tuesday will be in the 20s. Dry air mass provides little chance for any rain, with mostly clear skies through Thursday. Temperatures slowly warm from Tuesday afternoon onward, but Monday and Tuesday look to be 5 to 10 degrees below seasonal normal. Strongest winds of the period are with the FROPA Sunday night/ Monday morning, with highest winds over higher elevations at 10 to 20 mph. These northerly winds combined with cold/dry advection will produce some wind chill down into the teens at the highest elevations in exposed locations. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... At KCLT and elsewhere: A few showers are crossing the SC and srn NC areas this evening. These will approach CLT arnd 00z and may mix down stg gusts and bring MVFR/IFR restrictions...have VCSH for now as confidence is low on track and duration of these cells. After this activity clears east arnd 03z...the fcst will become VFR all TAF sites with winds remaining fairly stg and gusty at times overnight and into the daytime period. Winds will veer...generally going from sw/ly to nw/ly thru the period. Outlook: General VFR conds will prevail through the next few days although diurnal restrictive cigs/vsbys are possible across the mountains and foothills each morning. Confidence Table... 01-07Z 07-13Z 13-19Z 19-00Z KCLT High 99% High 100% High 100% High 100% KGSP High 92% High 100% High 100% High 100% KAVL High 100% Med 72% Med 68% Med 61% KHKY High 100% High 91% Med 76% High 100% KGMU High 100% High 92% High 100% High 100% KAND High 100% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...Wind Advisory until 4 AM EDT Friday for GAZ010-017. NC...Wind Advisory until noon EDT Friday for NCZ033-048>053-058-059- 062-063. SC...None. && $$ SYNOPSIS...CAC NEAR TERM...Munroe/SBK SHORT TERM...WJM LONG TERM...WJM AVIATION...SBK
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
840 PM CDT Thu Oct 29 2020 .UPDATE... Updated for evening discussion. && .DISCUSSION... Despite strong low level subsidence in the cold air advection regime, sufficient overall ascent remains with the advancing thermal trough to support the persistent low cloud cover in the shallow moist layer near 850 mb this evening. RAP and HRRR show the low level thermal trough moving through most of the area after midnight and taking the majority of the cloud cover with it as subsidence becomes dominant. Residual cloud cover will remain in the east around sunrise, but clearing will ensue shortly thereafter./GG/ Prior discussion below: Tonight into Tomorrow: A much cooler day has prevailed across the region with temperatures 15 to 20 degrees cooler than this time yesterday. This all comes as a front moved through the region earlier today and an upper trough moved across the region. Cold air advection has been in full swing today, and despite the sunshine, temperatures have been in the upper 50s and lower 60s today. A chilly night is expected, but some cloud cover moving across the region may help keep conditions better than they otherwise might be. Temperatures tonight will be in the lower 40s. Another cool day is expected tomorrow with highs ranging from the upper 50s in the north to the lower 60s in the south. Northerly winds will continue tomorrow but overall wind gusts should not be as strong as they were today. Dry weather will continue Friday./28/ Saturday through Thursday: Dry weather looks to persist this weekend through the middle of next week, with generally high agreement among model guidance for the overall pattern through that time. Between departing high pressure and the next cold front, max temps on Saturday should rebound to near 70 degrees across the area. Then heading into Sunday, a digging upper-level shortwave trough and attendant surface low over the Great Lakes trough will usher a cold front through our forecast area. Timing of the front`s arrival means cold air advection may not establish fully until the afternoon - after temps have a chance to warm up during the day. Stuck with a general consensus blend of guidance for the day until the finer details come into focus. In the wake of the front though, Sunday night through Monday night especially will be cooler. As post- frontal surface high pressure settles over the Deep South, nighttime cooling will have a chance to overachieve with radiational cooling. While no freezing temperatures are currently anticipated, frost development across looks increasingly likely across much of the forecast area Monday night into Tuesday morning. Added patchy frost to the forecast for Monday night as lows fall into the lower to mid-30s with light winds and clear skies. Did not include in the Hazardous Weather Outlook text or graphics at this time, but will likely need at least "Limited" threat area going forward to capture the frost potential. /NF/ && .AVIATION... 00Z TAF discussion: MVFR ceilings this evening, mainly north of Interstate 20, will diminish from the west after midnight. VFR conditions will prevail for the remainder of the period./GG/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 43 60 41 69 / 3 0 0 0 Meridian 45 60 42 70 / 0 0 0 0 Vicksburg 43 61 41 69 / 1 0 0 0 Hattiesburg 44 63 42 71 / 0 0 0 0 Natchez 43 62 41 69 / 0 0 0 0 Greenville 40 57 39 65 / 3 0 0 0 Greenwood 40 59 40 68 / 7 0 0 0 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$
Area Forecast Discussion
National Weather Service Marquette MI
633 PM EDT Thu Oct 29 2020 .SHORT TERM...(This evening through Friday) Issued at 353 PM EDT THU OCT 29 2020 Latest RAP analysis and GOES Satellite show troughing that extends from the Hudson Bay, down into the northern CONUS. With the cold front passing last night, sfc ridging of 1025mb is currently over the northern plains that will gradually shift towards the Upper Great Lakes Region by later this evening. Until then, north to northeast winds will be the driving force for some flurries or light lake-effect snow showers this afternoon. There were some areas of freezing drizzle from this morning. I don`t really expect to see much in the way of freezing drizzle this afternoon cannot completely rule it out but as a precaution, did include it in the grids with temps not rebounding from this morning. Winds will continue to ease and relax throughout the evening and overnight and any precip chances should be ending as well. With latest guidance, did end up penciling in some slight chc PoPs over the Keweenaw with a few webcams from Copper Harbor to near Houghton were showing light flurries. Clouds should be breaking up and clearing by Friday morning, setting up for a dry Friday with a mix of sun and clouds. Temperatures this afternoon have not really risen much since this morning with the clouds wanting to hang around. Did not mess with the temps for the rest of the day as I think the forecast is relatively on track. Lows tonight will again be mostly in the 20s with a few upper teens over the interior. If clouds do break earlier than anticipated, then lows could fall further but not really confident at this point as clouds and moisture look to keep temperatures from dropping too much. Even with some sunshine Friday, don`t think temperatures will warm too much as compared to today with highs again in the 30s. .LONG TERM...(Friday night through Thursday) Issued at 350 PM EDT THU OCT 29 2020 Weak upper level ridging will begin to take place by Friday night over the CWA allowing for moderated temperatures during the overnight period into Saturday. 700mb temperatures warm close to the 0 degree Celsius mark by late Saturday, which should mix down to the surface and allow afternoon highs to be near seasonal averages of the mid to upper 40s, with the southernmost inland areas reaching 50 degrees. The main weather system to affect the region will approach from the west Saturday night. This weather event looks to have multiple impacts as strong winds and lake effect snow showers will take place between Saturday night and Sunday afternoon. Medium range guidance has been in good agreement on the location and placement of the lake effect areas and strong winds the past few days. Gale force winds will be likely across the waters of Lake Superior along with shoreline erosion becoming possible during the strongest part of the weather system evolution. 700mb temperatures will decrease rapidly from near the 0 degree Celsius mark Saturday afternoon to near -15 to -18 degrees Celsius by Sunday evening. Overall, snow showers will increase in coverage from west to east early Sunday morning once the changeover in the lowest elevations from rain to snow occurs. Initial thoughts are for the heaviest lake effect snow to occur on the western half of the CWA, and then transition to the eastern half of the CWA for midday Sunday through the afternoon. The GFS has the slowest propagation of the weather event, thus the higher snow totals are forecast based off that model. The remaining medium range guidance has the weather event being more progressive, and inhibiting snow accumulation totals. Timing differences are still in place regarding an approaching shortwave disturbance on Monday arriving on the northern borders of the CWA potentially bringing a rain/snow mix to some of the areas. This shortwave will not have all that much of an impact in comparison to the weekend system. Upper level ridging then begins to take hold over the area as temperatures moderate nicely back to seasonal averages, with several areas likely eclipsing 50 degrees by the mid to late portion of next week before the next weather system approaches the area the following weekend. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 633 PM EDT THU OCT 29 2020 MVFR cigs are ongoing at all terminals and should remain at MVFR for the rest of the evening. All sites will go VFR later tonight, first at IWD and last at SAW. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 353 PM EDT THU OCT 29 2020 Winds will continue to ease through Friday with winds generally below 20 knots. This will last through Saturday morning and then attention will turn to Saturday afternoon into Sunday. Confidence his high, regarding the potential for high-end gales Saturday afternoon into Sunday. Winds will increase from the south with speeds up to 40 knots over the east half while the west half has winds up to 30 knots with some gale force gusts to 35 knots possible. Winds will transition to the northwest gales across the entire lake early Sunday morning through Sunday afternoon. Winds will be between 40-45 knots across the west half with possible storm force gusts between 50-55 knots across the east half. Waves will reach between 14-20 ft on Sunday. With the high confidence in this occurring, have posted a Gale Watch for west half and far east, and a Storm Watch for north central and east. Winds will diminish below 20 knots by Monday morning and will continue under 20 knots into Tuesday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Watch from Saturday morning through Sunday afternoon for LSZ251-267. Gale Watch from Saturday morning through Sunday morning for LSZ249-250-266. Storm Watch from Sunday morning through Sunday afternoon for LSZ243>245-248>250-264>266. Gale Watch from Saturday evening through Sunday afternoon for LSZ162-240>242-263. Gale Watch from Saturday evening through Sunday morning for LSZ243>245-264-265. Lake Michigan... None. && $$ SHORT TERM...JH LONG TERM...BW AVIATION...07 MARINE...JH/DR
National Weather Service Raleigh NC
930 PM EDT Thu Oct 29 2020 .SYNOPSIS... A surface area of low pressure and associated cold front will sweep across the region tonight. Canadian high pressure will follow for Friday and Saturday. && .NEAR TERM /THROUGH TONIGHT/... As of 930 PM Thursday... Winds continue to diminish with the departure of Zeta off the Mid Atlantic coast, although a fairly tight MSLP gradient persists over the region with surface low pressure centered over extreme NW NC / SW VA, a frontal zone extending from this low ENE to Zeta, a cold front extending south through GA, and large dense high pressure covering the Central Plains, so the risk of periodic gusts to 15-30 mph will hold tonight. MLCAPE of 500-1000 J/kg persists within the warm sector over the central and eastern Carolinas, and while the loss of heating should allow this to trend down a bit over the next few hours with rather low mid level lapse rates, the falling heights aloft and strengthening DPVA should help support increasing convection becoming more organized and growing upscale as it tracks rapidly NE. Damaging straight line winds attending bowing segments remain the primary threat given 40-45 kts at 925 mb, although some rotating cells cannot be ruled out. Have largely followed the timing of the last few HRRR runs, marching a convective line across the CWA over the next several hours, with a lingering threat of scattered showers and storms over the N and NE CWA overnight with the arrival of the potent mid level shortwave trough and upper divergence max within the associated right jet entrance region. Expect the surface low to track roughly eastward along the NC/VA border tonight, with weak surface troughing trailing back to the SW, and the actual synoptic front not pushing through until shortly before daybreak. Expect lows from the low 50s NW to low 60s far E. -GIH Earlier discussion from 350 PM: Wind gusts continue to diminish across cntl NC this afternoon; and all wind headlines will be cancelled with the 4 PM forecast package. A period of shortwave ridging aloft and subsident and stable conditions has expanded across NC this afternoon, between Zeta and a closed mid-upr level low over nwrn MS. That low will become an open wave trough while lifting and accelerating newd across the srn Appalachians and srn middle Atlantic through 12Z Fri, with preceding 50-100 meter 500 mb height falls and maximized QG forcing for ascent centered over cntl NC at 06Z Fri. At the surface, the remnants of Zeta, centered over srn MD at 19Z, will continue rapidly enewd and offshore the middle Atlantic through early this evening. A cold front was analyzed from Zeta wswwd across wrn VA and cntl WV, to a 999 mb low over ern KY. A trailing cold front was analyzed from that low sswwd across wrn GA and the cntl FL panhandle. The low will develop slowly ewd across the frontal segment across wrn and cntl VA through early tonight, while the trailing cold front continues ewd across GA and the Carolinas, including across cntl NC between approximately 03-07Z Fri. While wind gusts will generally weaken with both nocturnal cooling and the departure of the strongest flow accompanying Zeta, gusts between 20-35 mph will be possible at least intermittently overnight, in both swly flow ahead of, and nwly flow behind, the aforementioned cold front. Visible satellite imagery and regional radar data depict deepening cumulus and widely scattered showers along the cold front from ern TN swd across w-cntl GA this afternoon. The models indicate continued deepening and development will occur across GA and the wrn Carolinas through 00Z Fri. That convection will subsequently overspread cntl NC, while probably organizing into a broken line along the front. While the overall severe threat will remain only marginal owing to weak lapse rates and instability, the latter characterized by SBCAPE of generally less than 750 J/kg, the presence of strong vertical wind shear supplied by a 100 kt, swly 500 mb jet will maintain a conditional risk of locally strong/damaging surface wind gusts up to 45 kts or perhaps an isolated tornado, mainly along and east of a line from AFP to RDU to HNZ. Occasionally gusty surface winds will then continue behind the cold front overnight-early Fri, as much cooler and drier air surges, in nwly flow, across the region, with lows mostly in the 50s. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... As of 205 PM Thursday... The surface low will shift off the mid-Atlantic coast Friday morning as the upper shortwave exits northeast of the area. A cold front will be east of the area by early Friday in the wake of the departing surface low off the mid-Atlantic coast. High temperatures on Friday could be a bit tricky, but generally expect low 60s NW to upper 60s SE. Strong northwesterly flow will advect some cooler, drier air into the area, though the better CAA will occur Friday night as high pressure builds into the northeast and ridges into NC. With clear skies overnight but continued breezy conditions, expect lows Friday night in the mid 30s NW to mid 40s SE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 251 PM Thursday... Surface high pressure moving across the Northeast on Saturday will result in a cool and dry Halloween in Central NC. Highs will be below average in the mid 50s to lower 60s with lows in the 40s. A strong deep mid-level trough will move across the area Sunday afternoon and evening bringing below average temperatures. Models continue to show a slight chance of precipitation across the area with QPF between a trace and hundredth of an inch. Before the front moves across the region, temperatures will be warmer than Saturday with highs in the low 60s in the NW and Low 70s in the SE. As the high pressure builds across the southern central plains and moves east, it will bring the coldest temperatures of the season so far this season. Sunday night the NW Piedmont will see temperatures in the low 30s while the Coastal Plain will see upper 30s/ low 40s. The strong SW winds will keep frost from developing Sunday night/Monday morning. Highs Monday will be in the low to mid 50s, which is 15-20 degrees below normal. Monday night winds will be calmer due to high pressure overhead and clear skies will help make this the coldest night of the forecast period. Monday night temperatures across the entire area will be in the low to mid 30s resulting in some patchy frost, especially in the NW Piedmont. As the high pressure moves NE along the coast, temperatures will still be well below normal but will be in the upper 50s and low 60s. Wednesday and Thursday high temperatures will remain slightly below normal in the upper 60s and low 70s, with lows 40s. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... As of 740 PM Thursday... A complex weather pattern remains for the 00z TAF period. Post- tropical cyclone Zeta has already raced offshore into the Atlantic Ocean. Winds have relaxed a tad, but are still between 10 and 20 knots out of the south and southwest. There is some uncertainty on the direction and speed of the wind. In addition, expecting a period of low-level wind shear overnight-early Friday as winds remain strong around 35 knots. Currently, a weak area of low pressure exists over far northeastern Tennessee, with a trailing cold front extending into western NC and into Georgia. This cold front will track through during the overnight hours. Ahead of the front, expecting rain showers over the Triad, with a brief period of MVFR ceilings. Further east, expecting a line of showers and thunderstorms developing between 02-04Z at RDU, 04-06Z at FAY, and 05-07Z at RWI, with IFR/MVFR conditions. These storms should quickly race east onto the Coastal Plain shortly after 08Z, with some lingering showers at RWI till 09Z. Winds will shift to be out of the northwest after 13Z and remain gusty between 20 and 25 knots during the day with VFR taking over. Outlook: A couple of areas of high pressure will maintain mainly VFR conditions through early-mid next week, interrupted briefly by a chance of showers and MVFR conditions along a passing cold front on Sunday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Kren NEAR TERM...Hartfield/MWS SHORT TERM...KC LONG TERM...CC AVIATION...Kren/MWS