Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/22/23

Area Forecast Discussion
National Weather Service La Crosse WI
508 PM CST Sat Jan 21 2023 .DISCUSSION...(Tonight through Saturday) Issued at 210 PM CST Sat Jan 21 2023 Key Messages: - Light snow chances across the south tonight, perhaps freezing drizzle - Relatively mild temps persist for the new week with small snow chances * LIGHT SNOW CHANCES SOUTH TONIGHT: minor accumulations possible, freezing drizzle? Upper level shortwave trough currently across the southern plains is on track to move northeast across parts of IA/northern IL tonight. Decent slug of 700:300 mb QG convergence with this feature, although brunt of it currently pegged to hold south of the local forecast area. Some weak 600 mb Fgen does manage to setup across parts of northeast IA/southwest WI tonight per the RAP. Broad isentropic upglide along the 285:295 K sfcs also painted by the RAP across southern parts of the forecast area tonight. While missing out on the heart of the shortwave`s lift, this meager lift could be enough for light pcpn chance. CAMS and the deterministic model runs all suggest light QPF across parts of the NE IA/SW WI tonight, with support from the GEFS/EC ensemble members. If pcpn does stretch this far north, saturation could play a role in what falls. RAP/HRRR/NAM12 Bufkit soundings all show a dry layer roughly from 700:850 mb this evening. Eventually this saturates overnight, but at least initially there would be questions of ice in the cloud and/or if the near sfc saturation would be deep enough to support drizzle production (freezing drizzle in this case). When it does switch over to snow, COBB output at KDBQ in the NAM and GFS suggest up to 1" would be possible...looking more like a few tenths north of there. Have increased pcpn chances for portions of NE IA/SW WI tonight, moreso for the overnight hours. Added some freezing drizzle potential in the evening, then snow overnight with accums generally under 1/2 inch. * NEW WEEK OUTLOOK: staying somewhat mild with small snow chances The GFS and EC suggest more northwesterly flow a loft for most of the new week. Not a big push of colder air with the bend in the flow, at least initially, and temps look to hover at or above the late January normals for much of the new week. As we approach the weekend though, the GFS and EC start to shove colder air southward from Canada...with decent consensus in the models` ensemble members. 6-10 and 8-14 day CPC temp outlooks also suggest below normal temperatures loom on the horizon. So - perhaps one more week with relatively mild temps before a taste of winter cold returns. As for precipitation chances, a few shortwave troughs could drop through the Upper Mississippi River valley. One may slide across the north late Mon afternoon/night. The GFS is the more robust model with pcpn chances, but only minor QPF. NAM shows a bit while the EC keeps the bulk of any pcpn to the north. Will add some light snow chances north of I-94 for now. Another shortwave could come Tue night with both the EC and GFS spinning a ripple across northern parts of the region. A stronger and more impactful storm sits farther south, and continues to be trended to stay there (skirting the local forecast area). The next shortwave could track across the region Friday with most of the EC and GEFS members pointing to some chances for light snow. The same ensemble members disagree on how much snow would/could fall. Another shortwave then looks to take aim on the region over the weekend. All in all, some spotty light snow chances for the start, with the models trending a bit more active for the second half. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 508 PM CST Sat Jan 21 2023 Widespread IFR/LIFR stratus will likely prevail into Sunday. Areas of fog are also expected to develop this evening and persist into Sunday morning. Some potential for dense fog with visibility reduced to 1/4 mile exists, especially at KRST, but trends in fog development will be monitored this evening. Very patchy light freezing drizzle also could not be completely ruled out overnight, especially at KLSE, but confidence in occurrence is low. Slow improvement is possible by Sunday afternoon, although with the surface ridge holding just west of the region, confidence in more substantial clearing is very low through the daytime on Sunday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ DISCUSSION...Rieck AVIATION...JM
Area Forecast Discussion
National Weather Service Boston/Norton MA
1033 PM EST Sat Jan 21 2023 .SYNOPSIS... Dry and seasonable weather prevails into Sunday morning. A strong coastal storm impacts the region late Sunday into Monday, with heavy rain, gusty winds, possible coastal flooding and accumulating snow for northwest Massachusetts. Drier on Tuesday, but the active pattern continues as another system moves in for late Wednesday into Thursday with snow and mixed precipitation changing to rain. Mainly dry and seasonably cold conditions follow for Friday into next Saturday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... 1015 PM Update... Shallow moisture remains trapped beneath the subsidence inversion. The vast majority of guidance is handling this moisture very poorly. The only exception is the RAP relative humidity at 925 hPa looks very good compared to the latest obs. Have utilized this as a proxy for what will occur overnight. Really am not anticipating much of a change with overcast in place other than perhaps along the MA/NH border as there really is not much to kick this moisture out. With this in mind have increased temps to the 75th percentile of guidance for overnight as it is going to be very difficult to radiate. The only exception is across northern MA/NH border where temps may be able to drop with clearing skies. In this area have lowered to the 30th percentile of guidance as it looks reasonable, but still may be mitigated a bit by cloudiness. Rest of the forecast looks good at this point. 645 PM update... Stubborn shallow moisture trapped below the low level inversion has resulted in widespread strato-cu across SNE. Clearing noted across far NE MA northward through SE NH and Maine but this clearing not advancing southward. None of the guidance is handling these lower clouds very well. HRRR soundings do show some erosion of the shallow moisture 04-06z which would support clearing but confidence is low as subsidence inversion remains in place overnight as high pres builds across the region. Cloud cover will have a significant impact on low temps as any clearing would allow temps to fall into the teens, but 20s if clouds persist. We blended some of the milder raw guidance to raise temps a bit, but overall confidence is low. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/... Sunday will be an quiet day on the whole, as precipitation looks to hold off until late evening into the overnight hours. The mid level ridge early will help keep things dry, with at least partly cloud skies. We should see more sun through the high clouds than we saw today which, together with warm southwesterly flow, will help temperatures moderate, reaching the upper 30s in the high elevations and upper 40s along the southeast coast. The approaching storm system looks to be another mixed precipitation inside runner event as a surface low over the Carolinas deepens to sub-1000 mb off the mid-Atlantic coast and passes over Cape Cod. At the mid levels the positively tilted trough crosses southern New England mid day Monday, before which we should see the bulk of the precipitation fall. We`ve got plenty of moisture to work with as that SW flow taps into a 0.75-1.25" PWAT plume. This again looks to be a high elevation snow/low elevation rain event. The NAM3k is the only guidance currently advertising a 850 mb warm nose that would spell appreciable freezing rain with this event so have opted for a mainly snow/rain forecast at this point. A Winter Storm Watch is in effect for the northern slopes of the Berkshires which stands the best chance of seeing 7 inches of snow, but confidence is not high enough to go with a warning at this point. EPS ensemble guidance does have a 70-80% chance of 6+ inches but GEFS isn`t nearly as excited about the prospect. A winter Weather Advisory is in effect for Worcester Hills and southern Berkshires where 2 to 5 inches is more likely. This is another event where it is prudent to look at the positive snow depth change guidance more than the 10:1 snowfall accumulation guidance given marginal temperatures. As the low lifts northeast colder air is pulled in so everyone may get some light snow showers later in the day on Monday before things taper off. Strong, potentially damaging winds are looking like less of an issue given an offshore track of the low level jet and a fairly inverted sounding profile. However, we will have gusty N/NE winds on Monday morning, especially over the waters. This, in conjunction with high astronomical tides will give us a period of some minor coastal flooding along the MA east coast; coastal flood headlines will likely be needed for the Monday afternoon high tide. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Highlights * Dry and blustery Tue * Another storm brings snow and mixed precipitation changing to rain late Wed into Thu. Strong winds possible near the coast early Thu * Mainly dry and seasonable Fri/Sat Monday night into Tuesday... Upper trough moves to the east Mon evening with ridging building in behind it then a fast moving low amplitude trough follows for Tue. Any lingering rain/snow showers will exit SE New Eng Mon evening, then clearing develops overnight. Expect mainly dry weather with a mix of clouds and sun Tue. Just a low risk for a few flurries or snow showers over the Berkshires as the trough swings through. Temps will average slightly above normal with highs ranging from mid 30s higher terrain to lower 40s in the coastal plain. Decent pressure gradient Tue will support blustery W winds, gusting to 25-35 mph at times. Wednesday into Thursday... Active pattern continues with another southern stream system lifting NE from southern Plains. As has been the case all winter, consensus of the guidance favors an inland track with the primary low, while a secondary low tracks across SNE so will likely be dealing with a snow to rain scenario. However, high pres to the N across Quebec at the onset of moisture will provide antecedent cold air for precip to begin as snow across much of SNE Wed afternoon before changing to rain from south to north Wed night. 850 mb temps around -4 to -6C at the onset Wed afternoon then warm nose quickly lifts north Wed night. Still too early for specific snow accum but minor accum possible down to the coastal plain before changing to rain. The highest totals will likely be across interior northern MA. GEFS/EPS ensembles show fairly high probs of 3+ inches with low to moderate probs of 6+ inches across far northern MA. The storm lifts out during Thu so expect improving conditions by Thu afternoon. There could be some wind issues near the coast sometime late Wed night or Thu morning as a robust southerly low level jet is forecast to develop across SE New Eng. Coastal flood threat is marginal at this time. The high tide of concern will be the early Thu morning (225 AM) tide which is 10.33 ft at Boston which is fairly low. Would need about a 2 ft surge for minor flooding and this will depend on getting a period of strong E/SE winds at high tide which is highly uncertain. Winds will be shifting to S/SW by Thu morning. Friday into Saturday... Looks mainly dry and seasonably cold Fri behind the departing storm. Then low confidence forecast for Sat as there is considerable spread among the guidance. Followed NBM for now. && .AVIATION /04Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 00z TAF update... Tonight... MVFR cigs should trend to VFR 04-06z as clouds scatter out but confidence is low to moderate at best as there is uncertainty if shallow moisture erodes below the subsidence inversion. Winds light and variable with the high overhead. Sunday... Dry and VFR becoming MVFR by 00z in light rain or snow/mix for northwest MA. Light SSW winds to start, then increasing 15-20 kts late in the day across Cape Cod and islands. Sunday night... IFR. Light to moderate RA for most but SN possible for a time at BDL/BAF/ORH. NE winds 10 kt gusting to 20 kt toward 12Z; 25-30 kt for the Cape and islands. KBOS TAF...Low to moderate confidence in TAF due to uncertainty in MVFR cigs scattering out. KBDL TAF...Low to moderate confidence in TAF due to uncertainty in MVFR cigs scattering out. Outlook /Monday Night through Thursday/... Tuesday Night: VFR. Windy with local gusts up to 30 kt. Wednesday: Mainly VFR, with local IFR possible. Breezy. Chance SN, chance RA. Wednesday Night: MVFR/IFR conditions possible. Strong winds with gusts up to 40 kt. RA, SN. Thursday: Mainly VFR, with local IFR possible. Strong winds with gusts up to 40 kt. Chance RA, slight chance SN. Thursday Night: VFR. Windy with gusts up to 35 kt. Friday: Breezy. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Saturday night through Sunday night...High Confidence. Sat night...1020 mb high builds over SNE, with light winds, dry weather and good vsby. SE swells continue to erode. Sunday...1020 mb high moves offshore, with SSW winds developing, and increasing 15-20 kt in the afternoon. Dry weather and good vsby, but rain possible toward 00z Monday. Sunday night...Rain overnight. Light SE winds become gusty out of the NE, gusting 25 to 30 kts with 3-5 ft. Outlook /Monday Night through Thursday/... Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Wednesday: Winds less than 25 kt. Chance of rain. Wednesday Night: Moderate risk for gale force winds with gusts up to 40 kt. Areas of rough seas. Rain. Thursday: Moderate risk for gale force winds with local gusts up to 45 kt. Rough seas up to 11 ft. Chance of rain. Thursday Night: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 11 ft. Friday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. && .TIDES/COASTAL FLOODING... * Minor coastal flooding possible midday Monday High Tide We are watching the late Monday morning/early afternoon high tide for widespread minor coastal flooding along the eastern MA coast, Cape, and Nantucket. Although the strongest winds aren`t expected to reach the surface, winds will nevertheless be gusty and combined with very high astro tides coastal flooding is possible. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Winter Storm Watch from Sunday evening through Monday afternoon for MAZ002-008. Winter Weather Advisory from 7 PM Sunday to 4 PM EST Monday for MAZ003-004-009-026. RI...None. MARINE...None. && $$ SYNOPSIS...KJC/BW NEAR TERM...KJC/BL/BW SHORT TERM...BW LONG TERM...KJC AVIATION...KJC/BW MARINE...KJC/BW TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Charleston SC
907 PM EST Sat Jan 21 2023 .SYNOPSIS... A low pressure system will produce unsettled weather from tonight until a cold front crosses the area late Sunday night. High pressure will then briefly return before another low pressure system impacts the region midweek. High pressure is expected late week into the weekend. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... The forecast is on track. Rain is slowly expanding across the area this evening as forcing for ascent intensifies. Rain has been pretty very light so far with RAP soundings and the 22/00z KCHS raob highlighting still fairly dry sub-cloud layer. This will steadily change overnight as the column moistens and forcing intensifies. Pops near 100% look good. Temperatures should hold steady through the night as diabatic cooling weakens due to a steady moistening of the column and may actually rise a bit across the far south and along the coast as a coastal front approaches. Lows were nudged down in a few spots given observed temperatures at 22/02z. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/... Sunday will be the most active day of the short term period. A warm front will continue lifting into the region, while a wave of low pressure develops and rides along the front. Rainfall will be ongoing Sunday morning with additional showers and embedded thunderstorms expected through the day. There could be somewhat of a lull in the early afternoon before the next batch of rain with a trailing cold front comes through. Rain chances will decrease overnight with shower activity expected to be all offshore by daybreak Monday. Latest rainfall totals Sunday through Sunday night are forecast to average 0.75-1.25 inches, though some locally higher amounts are possible. The area is highlighted under a Marginal Risk in the Excessive Rainfall Outlook, however given the relatively dry antecedent conditions, the flood threat will largely be limited. There is concern for decent rainfall rates around the time of high tide (occurring ~815 AM) which would exacerbate conditions in low- lying and urban areas along the coast. Poor mid level lapse rates and weak instability will keep severe threat low, but wind fields could support a couple stronger storms with damaging wind gusts if more instability is realized. Much of the area is encompassed in a Marginal risk for severe weather in the SPC Day 2 outlook. Lake Winds: Gusty west winds are expected to develop behind the cold front late Sunday night through Monday morning. A Lake Wind Advisory will likely be needed. Drier and cooler air will move in behind the front as high pressure builds over the region for Monday and Tuesday. Winds will remain a bit gusty through much of Monday before subsiding as the pressure gradient eases. No other weather concerns are expected. High temperatures will generally be in the upper 50s to around 60. Low temperatures Monday night will range from around freezing/32F inland to upper 30s/around 40 closer to the coast. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... A mid level low and associated surface reflection will lift out of the Southern Plains Tuesday night and track towards the East Coast on Wednesday, bringing the next chance of rain to the area. Dynamics and wind fields could support stronger storms, but the instability will again be the question. In addition, it will get quite breezy. A Lake Wind Advisory will be possible. Dry and quiet weather is then expected Thursday through the end of the week as high pressure returns. Temperatures will be warmest on Wednesday, then fall to around or below normal behind the cold front. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... KCHS/KJZI/KSAV: Conditions will deteriorate overnight as rain spreads in from the west and southwest. A steady rain will dominate all terminals by late evening which will linger into Sunday morning before a break occurs. Widespread IFR conditions are likely overnight with cigs dropping to LIFR closer to daybreak. The risk for LLWS will increase for all terminals by late morning into the afternoon as wind fields increase ahead of an approaching cold front. Extended Aviation Outlook: Flight restrictions are likely into Sunday night as low pressure tracks across the region bringing showers and even a possible rumble of thunder. Sunday into early Monday morning low level winds continue to tighten with LLWS possible. VFR will then prevail on Monday and most of Tuesday. Another round of flight restrictions will be possible on Wednesday. && .MARINE... Tonight: A northeast surge will persist across most local waters early, topping out in the 15-20 kt range. A few gusts up to 25 knots will be possible heading into early evening while the pressure gradient is slightly enhanced. However, expect the pressure gradient to decrease through the overnight period as low pressure passes across the area late. Wind speeds should decrease to 10-15 kt at this time while winds flip to east, then southeast heading into daybreak. Seas will average between 2-4 ft, largest across offshore Georgia waters and northern South Carolina waters off the Charleston County coast. Sunday through Thursday: Low pressure will pass across the region Sunday into Sunday night. Southerly winds will increase ahead of this system and Small Craft Advisories have been hoisted for the Charleston county and outer Georgia waters. It is possible they will need to be expanded to include the remaining waters as well. Winds will turn westerly and remain elevated following passage of a cold front overnight. Small Craft Advisory conditions will likely persist through most of the day Monday before subsiding as the pressure gradient eases. There is an outside chance for gale force wind gusts Sunday night into Monday morning, mainly across the Charleston county waters and outer Georgia waters as well, however confidence in duration/frequency is not high enough to hoist any Watches at this time. No additional marine concerns expected until Wednesday when the next system impacts the area. Another round of Small Craft Advisories are likely for most, if not all, waters. && .TIDES/COASTAL FLOODING... Sunday morning high tide (~8:15 am): The astronomical high tide is 6.31 ft MLLW at Charleston, meaning we would need to see a departure of around 0.7 ft to reach 7.0 ft MLLW and produce minor coastal flooding. Northeast winds will prevail through tonight, which should be quite favorable and drive the tidal departure sufficiently high. Also of note, an area of low pressure is expected approach and reach the coastline of the forecast area by around the time of high tide. Guidance is a bit varied on how high the tide will get, but there remains a potential levels will reach moderate flood stage (7.5 ft MLLW) in the Charleston Harbor. For Fort Pulaski, the astronomical tide is 8.23 ft MLLW and probabilitistic guidance indicates there is a really solid chance the observed tide will peak at or above minor flood stage (9.5 ft MLLW). A Coastal Flood Advisory will likely be needed for Charleston and Colleton Counties and possibly for the far southern South Carolina and Georgia coasts. Decent rainfall rates are expected around the time of high tide which would exacerbate any ongoing saltwater flooding issues. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory from noon Sunday to 7 PM EST Monday for AMZ350-374. && $$
Area Forecast Discussion
National Weather Service Duluth MN
949 PM CST Sat Jan 21 2023 .DISCUSSION...(This evening through Friday) Issued at 432 PM CST Sat Jan 21 2023 Summary...Cloud cover clearing this evening may lead to a cold night for parts of the area, but otherwise lingering clouds to keep us murky and moderated overnight. Our next chance of snow is Monday as a clipper moves through the area. Additional clippers may bring more snow chances during the work week. We may get some colder weather next weekend as colder air moves into the region. A steep inversion is making the cloud forecast tricky this afternoon, with the Day Snow-Fog RGB satellite imagery showing the western edge of the IFR stratus over most of the area this afternoon quite clearly. The RAP appears to be getting a handle on this stratus deck, which is trapped beneath a strong inversion at the surface, extending to around 925mb according to the MPX and INL soundings from this morning. The RAP continues the slow eastward progression of the west edge of the 925mb moisture/clearing line up until mid evening before stalling and re-developing overnight. Wherever it clears out this evening, the temperature is likely to drop into the single digits, with teens where the cloud cover remains. Have played a more pessimistic cloud forecast for now, but anticipate needing to update this evening as the boundary layer settles back down after sunset. Fog may re-develop, but anticipate it becoming stratus rather than poor visibilities. On Sunday a ridge axis slides into the area, and assuming this stratus layer does not expand extensively overnight, we should clear out for at least parts of the area during the morning, with some welcome sunshine for the area. A clipper moves through the area beginning late Sunday night, bringing light snow to the area for Monday before pulling out Monday evening. The forcing is best for a short period of time during the morning, followed by cold air advection showers behind it. The f-gen band does not look very impressive, so am not expecting a lot of snow out of this, so while I have raised pops for this shortwave, have kept the QPF on the low side, producing less than an inch of snow through the period. Tuesday through Thursday we will be in northwest flow with a series of weak clippers moving through the upper level flow. Model agreement on these clippers is very poor, and so the model blends have given us an effectively dry forecast through the middle part of the week. However, experience shows that with each of those clippers we are likely to get at least some flurries, if not a quick dusting. For now have added in some small chance pops to some of those periods, but we are going to have to wait and see how these develop before making a more definitive call. These are going to be dependent upon the behavior of a stronger system that will affect the southern CONUS in this time frame as well. We will also be very similar in temperatures to what we have this weekend, with highs generally in the 20s and lows in the single digits and teens, depending on cloud cover. A stronger trough axis is showing up that the deterministic models seem to be latching onto in a more consistent way but the ensembles are showing mainly broad troughing in this time range, so it is probably too soon to latch onto this, and have left the blended, slight chance pops here as is. There is a consistent signal for a shot of colder air behind this system, and we may have some sub-zero overnight lows next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 541 PM CST Sat Jan 21 2023 Clearing is occurring over north-central Minnesota and is likely to bring VFR conditions to INL/BRD at least through mid this evening. Thinking remains for fog to develop again under a lowering inversion that continues to trap near-surface moisture each night and result in IFR stratus cigs and patchy fog lowering vis at area terminals. Stratus scours out and lifts to MVFR and fog dissipates towards 18z. && .MARINE... Issued at 946 PM CST Sat Jan 21 2023 Southwest wind gusts remain generally between 10 to 20 knots tonight and Sunday before increasing again Sunday night into Monday as a shortwave brings snow chances into the area. Winds turn to the northwest Monday night before diminishing again. Small Craft Advisories may be needed for much of the Nearshore waters Sunday night through Monday night. && .PRELIMINARY POINT TEMPS/POPS... DLH 12 24 11 29 / 0 0 10 20 INL 3 21 12 29 / 0 0 40 30 BRD 7 21 10 32 / 0 0 0 20 HYR 13 24 8 29 / 0 0 0 30 ASX 15 26 12 29 / 0 0 0 30 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. LS...None. && $$ DISCUSSION...LE AVIATION...NLY MARINE...NLY
Area Forecast Discussion
National Weather Service Quad Cities IA IL
808 PM CST Sat Jan 21 2023 .UPDATE... Issued at 805 PM CST Sat Jan 21 2023 Snow is on track, moving northeast with primarily visibility and impacts shown on Iowa DOT of light snow, although some images suggest it`s quite dendritic in nature at times, likely in the higher reflectivity areas. For now, it`s covering our south 1/2 and about to begin snowing in the Quad Cities as of 8 PM. Thus far, the visibility reductions to the north of I-80 in our western areas seem more to do with fog than snow. No major changes to the forecast at this time. ERVIN && .SYNOPSIS... Issued at 210 PM CST Sat Jan 21 2023 An interesting day was seen, with persistent low clouds and fog through much of the morning and into the early afternoon. Along with the stratus/fog, we observed very fine ice crystals falling all morning. This has lead to a dusting of snow on the ground, which coupled with the freezing fog/mist from the morning, led to a few slick spots. We are still seeing light radar returns from these falling crystals, but this is fading away. While all of this is happening, locations along and south of Highway 34 in our forecast area have been mostly clear through the day thus far. Given much of the area has been socked in clouds, temperatures didn`t warm as much as initially expected. Much of the area remains in the mid to upper 20s, with our south in the low to mid 30s. Winds remain light and variable as well, which helped keep us blanketed in the fog through much of the morning. && .SHORT TERM...(This evening through Sunday) Issued at 210 PM CST Sat Jan 21 2023 This evening and through the night, a weak low pressure system will pass through the area, bringing some light snow. Snow is forecast to move in between 6PM to Midnight, and last through tomorrow morning for most. Short-term guidance is in general agreement for a widespread 1-2" event, with less than an inch currently expected in our northwest. We are slowly trending lighter on precipitation totals. Thus, we may see this decrease a little more. Some may not even see snow in the northwest, but given a deep layer of saturation, some light accumulations cannot be ruled out. Thus, we have increased PoPs slightly. Guidance indicates the best lift moving through the area tonight, which would bring the heaviest snowfall rates. This generally looks to be around the midnight hour. As we approach sunrise, forcing weakens and we will be left with light snow. Heaviest axis of snow falls along a line from Fairfield IA through the Quad Cities. Although, NBM 90th percentiles doesnt show 3" anywhere in the area, we will stick with that as the high- end snow amount, as some localized areas may see close to that. Best chances to see up to 3" is in our western counties between the Highway 34 and Interstate 80 Corridors. Fortunately, we won`t be dealing with gusty winds with this system. Winds are actually forecast to be light and variable, which will make measuring the snow easier and also cut back on any blowing snow potential. Temperatures aren`t expected to drop much tonight, as a dense cloud canopy will help hold the "heat" in. With similar conditions in place tonight, we have the potential to see some patchy dense fog again tonight. Tomorrow, we will continue to see some lingering light snow and flurries as the system exits. Much of guidance holds the precipitation in the area until around noon, then slowly moving it out. At this point tomorrow, the snow will be fairly light and not much accumulation will be expected. Bulk of snow accumulation will be tonight into the early AM tomorrow. Temperatures tomorrow will range from the upper 20s in our northwest to the mid 30s in the southeast. .LONG TERM...(Sunday night through Saturday) Issued at 210 PM CST Sat Jan 21 2023 Key Messages: - Midweek system brings a chance for snow for portions of the area. - Fairly seasonable temps. Details: Sunday night and Monday Uncertainty with extent of any clearing of stratus during this period. HRRR experimental ceiling plots along with RAP13 and NAMNest are all quite bullish with low cloudiness for much of this period. HREF ensemble mean low cloud cover does support partial clearing possible with 40-60 percent cloud cover by 12z Monday while NBM probs are 20-40 percent. However, given the time of year, likelihood of light snow cover on the ground, and models showing weak surface ridging building in by Monday it seems like a good setup for the moisture to get trapped beneath the increasing subsidence inversion. As a result, I`ve started trending upward on sky cover and nudging up Mins Sunday night while leaving Max T alone for Monday for now. Tuesday through Thursday Medium range models continue to support a storm system ejecting from the Southwest, reaching the Tennessee and Ohio Valleys midweek then lifting into the Mid-Atlantic. Still some differences noted in the track, but enough cold air exists on the north side of the storm track for snow. The track will be critical in determining how much of our area sees snow late Tuesday night through Wednesday, and potential amounts. At this juncture the preponderance of the deterministic and ensemble guidance would favor the main deformation band and heaviest amounts south of our area, but again model changes should be anticipated as the main energy is still offshore in the Pacific Northwest this afternoon and will get better sampled over the next 24 hrs. The ECMWF deterministic and 30-50 percent of ensemble membership have trended deeper and further southwest with a northern stream wave digging behind the departing mid-week system. As a result, it maintains some light snow through Thursday where currently the forecast is dry. Being still many days out and also a rather recent slower/southwest shift from the EC on the wave, I`ve opted to stay with the drier NBM for now but will need to keep tabs on these trends for potentially needing to add PoPs for Thursday. Friday and Saturday Forecast is for dry and seasonably cooler conditions. However, may have to watch for some precipitation chances, as the flow pattern aloft seems to favor semi-zonal per mean of ensembles and deterministic models, which could shuttle several disturbances eastward ahead of a potentially western CONUS trough. Temps likely to remain seasonable. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 514 PM CST Sat Jan 21 2023 Light winds, light snow, and fog will provide poor flying weather through mid morning Sunday. The snow should quickly spread over the entire area this evening, between 00z and 04z. Amounts will not be too much, only an inch or two, but the fog and snow will likely bring low visibility for an extended time overnight, through mid morning, when winds will switch the to the northwest, but only at 5 kts or so. I`ll keep TAFs pessimistic on any improvement in cigs, but will allow visibility to move into the 2-4sm range Sunday morning. ERVIN && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ UPDATE...Ervin SYNOPSIS...Gunkel SHORT TERM...Gunkel LONG TERM...McClure AVIATION...Ervin
Area Forecast Discussion
National Weather Service Indianapolis IN
929 PM EST Sat Jan 21 2023 .Forecast Update... Issued at 929 PM EST Sat Jan 21 2023 GOES-16 Night Fog product and obs were indicating the clearing has moved all the way north to near the Interstate 70 corridor, so had to adjust cloud cover down further north as well as temperatures. In fact, after coordinating with adjacent offices, lowered overnight lows in this area as temperatures were at or near previous forecasted lows. The clear skies over south central Indiana will be very short-lived, however as clouds ahead of the Plains system will quickly swoop in from the west. 295K Isentropic analysis continues to advertise impressive upglide overspreading central Indiana from west to east overnight, ahead of the Plains system. Condensation pressure deficits less than 30 millibars correlate nicely with a saturated column and they will spread west to east across central Indiana overnight. With this in mind, will likely see snow develop over the Wabash Valley and spread quickly eastward 06z-12z. Look for a dusting or more by daybreak with the bulk of the snow accumulation after 12z Sunday. && .Short Term...(This evening through Sunday) Issued at 300 PM EST Sat Jan 21 2023 - Snow arriving late tonight - Snow ends Sunday morning; Clouds remain through Sunday afternoon Surface analysis late this morning shows a broad area of high pressure stretching from West Virginia and Ohio, across Indiana to southern Illinois. A weak ridge axis over Central Illinois stretching toward Iowa and the upper Mississippi Valley was noted as Satellite shows clearing to the west of this axis. Clouds across Kentucky have finally been showing some south to north erosion, with a clearing line approaching the Ohio River. Aloft a ridge axis had moved east of Indiana and was found over Ontario and Ohio. An upper low was seen within water vapor imagery over SW KS and the OK panhandle, along with a broad associated trough stretching from the northern plains to New Mexico. Radar mosaics show snow and rain ahead of the low over KS and eastern OK. Tonight through Mid Day Sunday... ...Light Snow Expected Late Tonight... ...Snow covered surfaces possible late tonight and early Sunday... Early this evening, some brief clearing will be possible over southern parts of Central Indiana as the cloud erosion to the south continues to make progress north. This may be the initial story this evening, but changes will arrive overnight. The upper trough and low are suggested to push toward Indiana and the Ohio Valley overnight. Ample forcing aloft will allow for precipitation ahead of the wave. 295K Isentropic surfaces show flow nearly directly rising in on the surface...allowing for strong lift. Specific humidity of near 4 g/kg are suggested to arrive by 09Z before departing to the east by 15Z. As the isentropic lift departs by late Sunday morning, The upper trough will still be over Indiana with a poorly organized surface low over Central Kentucky. This may result in some additional snow lingering across the area early in the afternoon wrapping around the system. However there remains some uncertainty as to how impactful that will be as some dry air is shown wrapping into the system within the middle levels. Thus overall best forcing and lift should arrive in the area after 10Z and persist through 15Z and this will be the best window for snowfall. HRRR appears on board with this timing. Forecast soundings show good saturation within the mid and lower levels as these features pass with pwats near 0.3-0.4. Inches. Although the soundings remain below freezing, indicating snow, saturation is mainly within the 0 to -10 degree zone rather than the dendritic growth zone. Overall, confidence is high for snow late tonight and ending on Sunday morning due to good forcing features with light amounts due to limited moisture, quick moving isentropic lift and limited saturation within the DGZ. Ongoing amounts of 1-2 inches of accumulation with isolated higher amounts appear reasonable. The most favorable area for snow will be along and south of a HUF-MIE line due to best moisture proximity. Will use highest pops here with lesser pops to the NW. Given evaporational cooling, lows in the mid to upper 20s will be reasonable. Sunday afternoon... Previously mentioned isentropic lift is lost by mid to late afternoon as the system departs east. Isentropic surfaces show subsidence as winds across Indiana become northwesterly in the wake of the front. Forecast soundings at that time once again shows trapped lower level moisture beneath a weak inversion amid cyclonic lower level flow. Thus will trend mainly cloudy skies. Cold air advection will be ongoing, thus little in the way of rising temperatures will be expected and will trend highs to only the lower 30s. && .Long Term...(Sunday night through Saturday) Issued at 302 PM EST Sat Jan 21 2023 Sunday Night through Tuesday.. Any accumulating light snow from the late weekend`s rather weak system should have tapered off by 00z Sunday evening...although lingering flurries cannot be ruled out as the supporting trough axis slides east across the region through the evening. Minor impacts are possible from wet surfaces re-freezing as air temperatures slowly drop below 32F and into the upper 20s by dawn Monday. More of the above-normal-temperature pattern we have grown accustomed to so far this January will resume during the early workweek, albeit more seasonable than past weeks. A broadening southern stream upper ridge will prevail over much of the eastern two-thirds of the CONUS, promoting subsidence and dry conditions. West-southwesterly breezes around surface high pressure near the Smoky Mountains...will keep overnights mixed with lows 25-30F, and afternoon highs slowly moderating from the upper 30s to low 40s for most locations. At least a couple periods of partly to mostly clear skies are expected through PM hours Monday and AM hours Tuesday... with high clouds likely increasing from southwest to northeast by late Tuesday. Tuesday Night through Wednesday night... Confidence is continuing to increase in a significant mid-latitude winter storm system developing through the mid-week as a southern- stream wave continues its eastward progression across Texas and eventually into Indiana...meanwhile deepening surface low pressure as it tracks up the lower Mississippi Valley and eventually up the Ohio Valley while occluding around the Wednesday timeframe. The supporting trough`s slight positive tilt will encourage an overall split precipitation shield, with the northwestern/cold-conveyor type section poised to cross central Indiana. Precipitation types across the CWA would likely be free of sleet or freezing rain with forecast soundings not suggesting any organized elevated warm layer on this northwestern side of the progressing system. Ensembles are suggesting rain to be more likely towards the Ohio River for the main slug of precipitation near the daytime hours Wednesday, yet so far it appears snow would be favored across at least the northwestern half of the region. A rain/snow mix is possible across the well as initial rain changing to snow as low-levels become colder through the event...yet further forecast updates will refine these details. A potentially limiting factor for any accumulating snowfall would be lack of established sub-freezing air at the surface, although temperatures would likely be close enough to 32F that any moderate or better snowfall rates would result in accumulation. Forecast Skew-Ts do suggest a saturated profile is possible for much/all of the DGZ when the heaviest portions of the precip shield cross the region. All snow should taper off around the Wednesday night timeframe as the system continues towards the Northeastern US. Thursday through Saturday... The second half of the long term will feature a pattern change back towards seasonable mid-winter cold as a broad upper trough envelops the eastern two-thirds of the country behind the storm system`s slow departure through the Northeast and into southeastern Canada. Broad cyclonic flow will prevail near, if not centered over Indiana, promoting scattered flurries. Light coatings from better organized snow showers are certainly possible under any passing, embedded vort maxs...which so far appears most likely around the Friday timeframe. Considerable cloudiness should facilitate diurnal spreads around 10- 15 degrees, with highs in the 30s and lows around 20-25F...making for perhaps the first tandem of days with seasonable temperatures since the third week of December. The predominate broad upper trough will be more of a southern-stream feature, with sub-normal cold temperatures likely held well to the northwest of the region... through at least Saturday. The normal max/min for Indianapolis through the long term are the lowest values of the year, 36/20. && .Aviation...(00Z TAF Issuance) Issued at 641 PM EST Sat Jan 21 2023 Impacts: - MVFR flying conditions expected to deteriorate to IFR and worse in snow after 10z Discussion: Overrunning ahead of a Plains trough will bring snow showers and deteriorating flying conditions to the terminals toward daybreak and through Sunday morning. Winds will be less than 10 knots and switch from SE to E toward morning and then NW Sunday afternoon. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Update...MK Short Term...Puma Long Term...AGM Aviation...MK
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
924 PM CST Sat Jan 21 2023 ...UPDATE... .SYNOPSIS... Issued at 245 PM CST Sat Jan 21 2023 Key Messages: -Lingering light snow across southwest into central Nebraska will exit the area by late this afternoon. -Temperatures remain near to below normal into next week, with light snow chances midweek and into the weekend. && .UPDATE... Issued at 923 PM CST Sat Jan 21 2023 A forecast update is in place for patchy fog across parts of the panhandle and extends the fog in time across ncntl Nebraska until 18z Sunday. The RAP model shows dry air moving in aloft and this should trigger fog as suggested by the HREF. The update uses the short term model blend. && .SHORT TERM...(This evening through Sunday night) Issued at 245 PM CST Sat Jan 21 2023 Currently, light snow continues across portions of southwest into central Nebraska, likely driven by an approaching subtle northern stream H7 trough interacting with a southern stream H7 low centered over south central Kansas. This light snow will end quickly over the next couple of hours from north to south, as the northern stream trough axis continues to push across the area. Little to no accumulation is anticipated. For tonight and tomorrow, expect partially clearing skies overnight, as subsidence increases aloft in the wake of a departing upper level low. For areas that do see clearing tonight, expect efficient radiational cooling again amid the persistent deep snowpack and light winds. Lows tonight fall to around 10 degrees where clearing occurs, and warmer where clouds persist. This efficient cooling will also lead to the potential for some patchy fog, especially across north central Nebraska. Confidence wanes with southwestward extent, though temperatures rising to near/just above freezing in some locales may enhance the potential for patchy fog above any snowmelt. This will need to be monitored, and further expansion in fog mention may be needed. Surface ridging spills into the Upper Midwest into tomorrow afternoon, with highs locally remaining near steady in the upper 20s to low 30s. Aloft, an upper low begins to drop southward across the Intermountain West. At the same time, a northern stream trough begins to dive southeast out of Canada. This will drag a cold front into the area tomorrow night along with increasing cloud cover from west to east. Some weak CAA behind this frontal boundary will help to offset the increasing cloudiness somewhat, and lows fall into the upper single digits to low teens. .LONG TERM...(Monday through Saturday) Issued at 245 PM CST Sat Jan 21 2023 Ensemble and deterministic guidance continues to trend towards a common solution with respect to precipitation potential on Monday. A noted southwestward shift in the southern stream upper low has been observed in much of the guidance suite over the last few model cycles. As a consequence, precipitation chances have also shifted westward, largely into portions of the western Panhandle and eastern WY/CO. A consensus is growing for the entirety of western Nebraska to stay dry as the best forcing remains well to our west. With this in mind, will keep a flurry mention in place west of HWY 61, though even this could potential be on the more aggressive side. Regardless, little to no accumulation is expected with the passage of this system Monday. The upper level regime remains active into the middle of next week, as northwest flow aloft establishes across much of the western CONUS. This will lead to the passage of at least a few different shortwaves in the mean flow aloft, with lingering light snow chances midweek into the weekend. Of note, guidance drags a cold front through the area Tuesday evening, as a surface low dives across the Dakotas. On Wednesday, some guidance is beginning to suggest steeping low and mid-level lapse rates in the postfrontal environment. This looks to lead to a threat for some snow showers (possibly convectively enhanced?) Wednesday afternoon amid diurnal heating. This will need to be monitored going forward, with the potential for impacts should confidence in any convective snow showers were to grow. Additional light snow chances continue into the weekend as guidance continues to paint shortwaves diving into the central CONUS. Confidence remains low with respect to any one system beyond midweek, and trends will continue to be monitored. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 545 PM CST Sat Jan 21 2023 Watching some weakening snow showers pushing southeast out of the Sandhills to approach the LBF terminal. Expect the weakening trend with this activity to continue, however, have added a tempo mention of light snow to account for potential of MVFR visibility restriction due to -SN. Attention then turns to fog potential mainly for north central Nebraska. VTN will likely fall on the west edge of the expected fog coverage so will keep prevailing MVFR with tempo mention of LIFR visibility. Confidence in this is low so will plan to monitor and amend as needed. After sunrise Sunday, expect a return to VFR conditions under mostly sunny skies. && .LBF WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...CDC SYNOPSIS...Brown SHORT TERM...Brown LONG TERM...Brown AVIATION...NMJ
Area Forecast Discussion
National Weather Service Louisville KY
957 PM EST Sat Jan 21 2023 .Forecast Update... Issued at 955 PM EST Sat Jan 21 2023 At this hour, nighttime microphysics satellite imagery reveals high clouds streaming across the region in advance of a disturbance moving in from the central and southern Plains. With cloud bases remaining high, temperatures have been able to cool into the low-to- mid 30s across the region, with a few upper 20s being observed in the typical cool spots. As we head through the overnight hours, temperatures should remain fairly steady along and north of the Bluegrass/Western KY Parkways, with slight warming expected to take place across southern KY. Precipitation will overspread the region from southwest to northeast between 3 and 7 a.m. EST tomorrow morning. Was hoping for some high- resolution model convergence with respect to precipitation types tomorrow; alas, the HRRR remains obstinate with its stronger/cooler solution, while the hi-res NAM continues with a weaker/warmer system. In general, have continued with a solution somewhere in between these two, with the best chances for accumulating snow north of the Ohio River, and a messy mix of mainly rain with some snow expected along the river. Most of central KY is still expected to see all rain. Have slightly tweaked snowfall amounts tomorrow morning in this update, adding a few tenths across our northernmost row of southern IN counties where a few hours of efficient snowfall rates are possible between 12-15Z tomorrow. Still think amounts on average will range from a dusting to an inch. Updated products have been sent out, with no major changes in the near term. && .Short Term...(Tonight through Sunday evening) Issued at 330 PM EST Sat Jan 21 2023 Upper ridging and surface high pressure, currently moving off to the east, are going to keep skies mostly clear through the evening hours, but this nice weather won`t last long. Early tonight, cirrus ahead of an approaching low pressure system will begin moving from west to east across the region. Shortly after midnight, rain showers will begin moving from central Tennessee into south central Kentucky. Then over the next few hours, showers will build in from the west, covering southern Indiana and central Kentucky by around 12z. Temperatures will remain at or above freezing at many location across the CWA, but a few locations in southern Indiana and the northern Bluegrass region of Kentucky will likely slip below freezing for a short period of time. This could cause a few area residents to see the slightest amount of ice on a metal handrail or vehicle during the rainfall. Most however will not see this, and with ground temperatures above freezing, issues aren`t expected. Tomorrow during the early dawn hours into the first few hours of the day, some of our communities, many across southern Indiana, will likely see snow mixed in with the rain showers, but again with the warm ground temperatures, impacts are expected to be minimal. Model soundings across most models are keeping the DGZ fairly dry and the low levels near freezing. This is expected to keep snow ratios low (3-7 to 1 range). By 15-16z, believe rain will be the dominant precip type across the CWA. Current thinking has around a dusting to around half of an inch over our southern Indiana counties. Higher amounts are expected to the northwest in Indianapolis` CWA. Rain will begin to end along the western edge of the CWA during the early afternoon hours. Rain showers will continue tapering off into eastern Kentucky during the evening hours. High temperatures will range from the upper 30s near Madison, Indiana to the upper 40s in Clinton County, Kentucky in southern Kentucky. With temperatures in sounding profiles so close to freezing, A few degree shift cooler and increased forcing from the upper jet could make higher snowfall amounts possible, so the forecast will be monitored and updated if needed. && .Long Term...(After midnight Sunday night through Saturday) Issued at 300 PM EST Sat Jan 21 2023 ...A Couple of Chances for Light Snow Accumulations... Sunday Night - Monday... A storm system will continue pushing off to the NE Sunday night into Monday morning, however low level moisture confined mainly to the 1000-850mb layer will continue to linger. A couple of complicating factors with the depth of the moisture and the low level thermal profile leads to low confidence in exact p-type during this stretch. In fact, will likely see varying p-types between snow showers when moisture is deeper and up to the bottom of the DGZ, and periods of drizzle or small ice pellets when moisture is shallower. There is even a chance for some very light freezing drizzle/rain in our eastern CWA if surface temps stay below freezing and saturation doesn`t extend deep enough into the cold. Overall, confidence is low in the exact low level thermal and moisture profile, so like the idea of advertising a few p-types during this time like previous shift. Any accums of whatever p-type would be light, but something to watch for minor impacts Monday morning anywhere surface temps stay at or below freezing. This would be most likely across NE portions of the CWA. The rest of Monday should be drying out with perhaps an improvement in the lingering stratus deck. Will keep an optimistic forecast for seeing some afternoon sun going, with the caveat that stratus decks love to linger this time of year. If we do get rid of the cloud deck, temps should be able to climb to the lower 40s for most. Eastern spots will likely stay in the upper 30s. Monday Night - Tuesday... Surface high pressure, and progressive low amplitude ridging will briefly control our weather Monday night/Tuesday. This will be a dry stretch with cold overnight lows in the 20s, and Tuesday afternoon highs warming notably into the 45 to 50 degree range. Tuesday Night - Thursday... Deep moisture from an approaching upstream system quickly overspreads our region by Tuesday night. Although temperatures will likely be running around 40 degrees at this time, wet bulb temperatures look to be in the low to mid 30s once the near surface dry layer is overcome. There is some question to just how favorable the low level temperature profile will be, along with surface wet- bulb temps at or just above freezing. Reasonable scenario for a snow event across our northern CWA would be a fairly short-lived and wet snow Tuesday night, before changing to mostly rain as the warm layer aloft wins out thanks to LLJ increase toward dawn Wednesday. Like what we have going now with some light accums across our north, but under what some of the 10:1 ensemble plumes (Grand ensemble) deterministic model snow outputs are showing. All of that said, the ultimate track of the intensifying surface low could place a heavier snow band across our northern CWA where heavier rates would promote better chances for accumulation and a prolonged favorable thermal profile. There will very likely be a tight snowfall gradient somewhere either across our northern CWA or displaced farther to the north out of our area of concern. Will continue to monitor trends, but something to watch for the southern Indiana counties that are not out of the woods for a more significant snowfall. Think it is more probable at this point that the heavier snow band ends up more over central IN, but overall spread in ensembles continues to yield lower confidence for a day 4- 5 event. As we get into Wednesday, the surface low looks to track across the CWA, with a strong low level jet overspreading the area. If there is a rain/snow line over our area, all indications are that the warm layer associated with the LLJ will win out and keep p-type all rain across the area by that point. Will continue categorical pops with temps climbing into the 40s for most. SE CWA could get into the low to mid 50s thanks to a tight temperature gradient. The surface low will pass to our NE by Wednesday night, with temperatures quickly falling again behind the front, and low level lapse rates steepening. At some point, the thermal profile will likely become favorable for a lingering wintry mix Wednesday night into Thursday morning. Thursday Night - Saturday... We may try to briefly dry out Thursday night through Friday morning, however a quick-hitting clipper system could dive into the region for later Friday. Could be a rain to snow type of event, but model solutions diverge and overall confidence is low at this time. && .Aviation...(00Z TAF Issuance) Issued at 645 PM EST Sat Jan 21 2023 Discussion: A storm system is expected to cross the Ohio Valley late tonight and into the day on Sunday. Precipitation types will be varied across regional terminals, with rain expected at LEX/BWG, snow expected at HNB, and a rain/snow mix possible at SDF, though latest guidance has trended toward more rain at SDF. Ceilings will begin to drop from southwest to northeast after 06Z tonight, with all sites expected to drop to IFR/LIFR levels by Sunday morning. Once ceilings drop, only modest recovery (IFR, maybe low-end MVFR ceilings) is expected after 18Z Sunday. Precipitation will bring reductions in visibility, with the greatest reductions expected at HNB where p-type will mainly be snow. Although visibilities could drop to MVFR/IFR levels, think that CIGs will be the primary driver of flight categories over the coming forecast period. Precipitation is expected to taper between 18-21Z Sunday, though lingering scattered rain/snow showers are possible into Sunday night and Monday morning. Confidence: Medium in ceilings; Medium in precip type at HNB, LEX, BWG; Low-Medium in precip type at SDF; Low-Medium in visibilities. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...CSG Short Term...KDW Long Term...BJS Aviation...CSG
Area Forecast Discussion
National Weather Service Raleigh NC
921 PM EST Sat Jan 21 2023 .SYNOPSIS... High pressure will drift across and offshore the Mid-Atlantic tonight, ahead of a frontal system that will cross the region Sunday and Sunday night. High pressure will follow for Monday and Tuesday. && .NEAR TERM /THROUGH TONIGHT/... As of 900 PM Saturday... Current analysis shows the forecast is on track, with only minor tweaks needed for the evening update. Rain is still expected to develop across the southern Piedmont in the next few hours, and spread northeast overnight across the region as isentropic ascent increases across the area. Only light rain is expected tonight, with heavier rain possible tomorrow as a plume of Gulf moisture moves across the Carolinas. Please see the previous discussion below for additional details. Previous discussion from 225 PM Saturday: A positively tilted, multi- lobed trough axis, evident in WV imagery and 500mb RAP analysis, is positioned from Manitoba through the southwest CONUS with a long fetch of enhanced southwesterly from NW Mexico into the Mid- Atlantic. At the surface, broad high pressure has filtered into the OH Valley this afternoon promoting dry and seasonable northerly surface flow through central NC. High clouds will persist over a majority of the area today within the mid/upper jet directing upper level moisture from upstream showers/storms over southern MS/AL, although thinning with northern extent. Conditions will rapidly deteriorate as the upper trough shifts into the Mid-MS Valley and upper divergences aloft promotes large scale ascent over the Mid-Atlantic and Southeast CONUS. Light to moderate rain will start to move into the southern Piedmont and Sandhills around 06z then spreading into the Triad and Triangle around 10z at the nose of the deeper moisture transport where enhanced moist isentropic ascent and a mid-level FGEN band spreads northeast. Although it will be a raw and cold at the onset of precipitation, a prevalent warm nose will be sufficiently strong to melt any frozen hydrometeors and surface temperatures in the mid 30s to low 40s will keep any frozen ptype concerns confined to the higher elevations of NC/VA. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 220 PM Saturday... An approaching storm system will lead to cold air damming and a raw, rainy, and chilly day on Sunday. The surface high pressure will continue to press offshore, but will have deposited a stable and chilly air mass over central NC. Rain will overspread the region with the timing relatively the same as the previous forecast cycle... between 12z and 15z Sunday. Temperatures are forecast to be above freezing when the rain develops, but the rain will lead to temperatures in the 30s and 40s all day Sunday. Surface low pressure is forecast to push from the Gulf Coast NE toward the eastern TN Valley region and weaken by 12z, with redevelopment near the coast of SC. This will become the primary low pressure as it tracks along the coast of SC/NC during Sunday afternoon. It is a Miller B type scenario; however, as the primary low fills leading to warming temps aloft ensuring an all rain event for our region. The main mid/upper level low will push from the Midwest through the Great Lakes Sunday and Sunday night. All this leads to rain, possibly in a couple of waves according to most model forecasts (one early in the day, the other later in the day). QFP should be generous, especially in the areas in the Drought in the south and east portions of central NC. Look for storm totals of 1.50-1.75" Slightly lower totals of 0.75-1.25" are likely further NW. Rain will continue into the evening, finally tapering to areas of light rain and drizzle between 06z and 12z/Mon. After highs in the upper 30s NW ranging into the mid 50s SE, temperatures will cool back into the mid 30s NW ranging into the lower 40s SE by Monday morning as the steadier rain ends. The thunder threat appears very limited inland, and for now will continue to keep it out of the forecast. For Sunday night into Monday, the weak surface flow within the CAD dome will mean a lingering risk of fog, drizzle, and some light rain well into Sunday night. A drying forecast is expected Monday as the cold front shifts offshore and strong CAA and DAA arrive (with a good downslope component during the afternoon). Expect gusty NW winds at 15-25 mph with gusts to 30-35 mph Monday afternoon. Variably cloudy to partly sunny skies will lead to highs in the upper 40s to upper 50s NW to SE. High pressure will then move over the region for Monday night. The clear skies and diminishing winds will allow temperatures to drop below freezing Monday night, slightly below normal. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 340 PM Saturday... Wet and mild Wednesday, between otherwise seasonable and dry conditions. Tue-Wed night: A vigorous mid/upper-level low over the Southwest at the start of the forecast period is forecast to deamplify from the srn Plains and lwr MS Valley newd across the OH Valley through Wed night. At the surface, high pressure initially over the Carolinas will drift offshore ahead of a surface cyclone that will organize and occlude from srn TX to the OH Valley and a secondary/triple point low that will develop along a retreating warm front in the lee of the srn Appalachians. For cntl NC, the sensible weather related to this pattern will feature near to slightly above average temperatures and dry conditions Tue-Tue night, then rain developing ewd, while becoming more showery in character, Wed-Wed night. Widespread low clouds and light morning rain, into a residually-dry continental airmass deposited by the aforementioned surface high, will favor in-situ cold air damming and temperatures in the 40s over the wrn NC Piedmont and Foothills Wed-Wed night, while warm frontal passage through the rest of NC will result in warming into the 50s-60s. Despite strong poleward moisture transport, including lwr 60s F surface dewpoints into cntl-ern NC, weak lapse rates aloft over the warm sector will likely yield only pockets of very weak instability. As such, the threat of thunder and/or severe weather appears low at this time. Thu-Sat: On the nrn rim of a broad sub-tropical ridge from the Bahamas to the Caribbean, and downstream of ridging forecast to amplify across the ern N. Pacific and Gulf of Alaska, a broad trough will encompass much of the CONUS east of the Rockies. While uncertainties exist with amplitude and timing of individual shortwaves within that pattern, dominant surface high pressure will extend across the srn US, including the Carolinas, and favor seasonable and dry conditions through at least Fri. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... As of 646 PM Saturday... There is high confidence in VFR conditions to start the TAF period. However, light to moderate rain and associated MVFR/IFR CIGs will spread from the southwest to northeast early Sunday morning through Sunday night. CIGs are expected to drop to LIFR at all terminals by mid afternoon Sunday as additional rounds of light/moderate rain progress from west to east across central NC. Additionally, strong winds (30 to 40 kts) just above the sfc will promote potential low- end LLWS conditions at KRWI early Sunday afternoon. Otherwise, sfc winds will generally remain enerly before turning nwrly late in the TAF period. Occasional gusts of 15 to 20 kts may be possible at KFAY and KRWI early to mid Sunday afternoon. Looking beyond 00z Monday, rounds of light/moderate rain will continue over central NC before shifting east and offshore early Monday morning. VFR conditions return Monday afternoon as high pressure begins to filter in from the TN Valley. Another storm system will bring a good chance of sub-VFR conditions late Tuesday night and Wednesday. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...Swiggett/JJT SHORT TERM...Badgett LONG TERM...MWS AVIATION...Luchetti/Swiggett