Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/11/24


Area Forecast Discussion
National Weather Service Columbia SC
1002 PM EDT Wed Apr 10 2024 .SYNOPSIS... Rain will spread into the area tonight with isolated thunderstorms possible. Thursday morning, severe thunderstorms are possible embedded within widespread rain which may be heavy at times. Gusty winds will increase from the south this evening and are likely to continue Thursday and Friday. Drier, warmer weather fills in behind the front for the upcoming weekend and early next week. && .NEAR TERM /THROUGH THURSDAY/... An upper level trough will swing into the Southeast as the associated surface low moves quickly across the Deep South. Convection from Wednesday`s MCS will shift eastward tonight into Thursday morning. The strongest convection may stay to the south of the forecast area with the system`s rain shield bringing widespread rain to most of the area. Strong low level winds and a tightening surface pressure gradient will lead to windy conditions Thursday morning. Gusts will pick up early Thursday with gusts to 35 to 40 mph possible, so we have issued at Wind Advisory starting at 12z Thursday morning. The heavy rain threat appears lower than previously expected. Over the last several runs the HRRR has consistently shown lower QPF amounts for the Midlands while keeping the deeper convection and higher rain totals south of the forecast area. This sort of trend along with radar showing thunderstorms along the FL panhandle is a typical situation that leads to lower rain amounts for the FA. Limited surface based instability will hinder convective updrafts and severe potential through the near term with sbCAPE values at most around a hundred J/kg. Damaging winds associated with the convection will be the biggest threat. 50 to 60 kt winds just 1 km up could mix down even in deeper shower/shallow thunderstorms. Given the weak instability the tornado threat is limited but a brief tornado can not be ruled out. Later Thursday morning, the back end of showers and storms should work into the forecast area. A prominent dry slot is shows up on satellite and radar for the system currently moving across the south, so we do expect a period of dry conditions early Thursday afternoon. When the upper trough moves through, it will bring another quick shot of moisture and daytime heating may generate a few diurnally driven showers before the main front moves through and alters the airmass. Highs on Thursday should be in the 70s, with upper 70s possible across the CSRA given that we clear out by the afternoon hours. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... Upper trough is forecast to be nearly overhead at the beginning of the short term as is a surface front stemming south from a low over the Great Lakes area. Winds at 850 mb are expected to be on the stronger side as the upper trough passes through, which will likely lead to gusty winds continuing for a few hours at the beginning of the short term. As the axis of the trough shifts overhead, a relative lull in the winds can be expected for a few hours. Then, the trough axis shifts eastward through the day on Friday. At the surface, the low pressure system drifts off to the northeast while a surface high begins to build into the region, keeping the pressure gradient relatively tight. This along with the winds behind the upper trough axis will likely lead to another day with gusty winds, but as gusty as Thursday. That said, NBM is showing a greater than 50% chance of gusts exceeding 30 mph in the afternoon on Friday. In addition, there could be some lingering light showers overnight Thursday as the upper trough moves through the region. Temperatures on Friday are forecast to be near average. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Generally quiet weather is expected for the long term as an upper ridge begins to build overhead and surface high pressure slowly drifts across the region. As a result, dry conditions are anticipated through midweek with temperatures warming into the mid 80s to begin the week ahead. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... Generally VFR conditions expected through 04-06z then deteriorating cigs as prefrontal rain moves into the region from the southwest. Latest runs of the HRRR are trending toward lower rain amounts and keeping the heaviest rains and storms south of the terminals so future updates may reflect improved conditions but expect MVFR and eventually IFR cigs to develop during the 06z-10z time frame. Some MVFR/IFR cigs in the rainfall possible but if trends continue will need to adjust to more optimistic vsbys Thursday morning time frame. Cold front will move through the region Thursday afternoon. Ahead of the front winds should be from the southeast around 10 knots through 06z then increase to 10 to 15 knots during the predawn hours as low pressure to the west deepens. Strongest wind gusts are expected in the late morning through afternoon hours with winds shifting to the south and eventually southwest behind the front with speeds around 15 knots and gusts to 30 knots possible. Cigs should improve behind the front after 16z-18z back to VFR. EXTENDED AVIATION OUTLOOK...Strong and gusty winds continuing through Friday. VFR conditions return for the upcoming weekend. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...Wind Advisory from 8 AM to 8 PM EDT Thursday for SCZ016-018- 020>022-025>031-035-037-038-041-115-116-135>137. GA...Wind Advisory from 8 AM to 8 PM EDT Thursday for GAZ040- 063>065-077. && $$
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1020 PM EDT Wed Apr 10 2024 .SYNOPSIS... Showers and scattered thunderstorms, some with potentially heavy rainfall, can be expected ahead of a cold front approaching from the west tonight and Thursday. Very windy conditions develop Friday. Dry and warm weather return for the weekend into early next week. && .NEAR TERM /THROUGH THURSDAY/... Evening Update...The fcst is in pretty good shape this evening. Did make some downward adj/s to PoPs across the NC mtns and fthills over the next few hrs as the upstream system is taking it/s time saturating the column over the nrn zones. Still expect more moderate rain to move in overnight and produce a good amt of rain thru Thu across the BR escarpment due to enhanced mech lift and a few rounds of convective activity arnd daybreak thru mid-day. The 00z HRRR has backed off the the non-escarpment precip and actually looks a little low with arnd a quarter to half inch storm total thru the day Thu. For now have not made sigfnt changes to QPF and will let the mid shift make any needed adj/s with the full fcst package. As of 300 PM EDT Wednesday: Rain has lifted north this afternoon, and is mainly confined to northern North Carolina. Widespread cloud cover remains in place, with the thickest clouds noted across the western two-thirds of the forecast area. A brief lull in rain is expected this afternoon and early this evening. Highs this afternoon should climb into the mid to low to mid 70s east of the mountains thanks to 850 mb SW`ly flow. Highs across the mountain valleys should climb into the upper 60s to lower 70s, with the mid 50s to mid 60s across the higher elevations. Cloud cover and rain chances ramp up again this evening into Thursday as a low pressure system approaches out of the west. Have high-end chance to likely PoPs across the western zones around midnight tonight, with likely to categorical PoPs across the entire forecast area by daybreak Thursday. Lows tonight will end up around 15-18 degrees above climo thanks to both cloud cover and rain limiting radiational cooling. Southerly winds will gradually increase this evening into tonight, becoming gusty, as the cold front associated with the low pressure system approaches out of the west. Gusty winds will linger throughout the day Thursday as the front tracks across the western Carolinas and northeast Georgia. Wind gusts should remain below Wind Advisory criteria across most locations, although higher elevations along the NC/TN border and the western North Carolina mountains may see gusts near advisory level. Widespread rain will linger through the morning hours before gradually tapering off from west to east Thursday afternoon. Embedded thunderstorms may develop early Thursday morning into Thursday afternoon thanks to both MUCAPE and SBCAPE ranging from 500- 1000 J/kg and 0-6 km bulk shear values ranging from 50-60 kts. SPC has a Marginal Risk for severe storms on Thursday, and this seems well placed as isolated strong to severe storms will be possible Thursday morning into Thursday afternoon ahead of and along the cold front. However, the overall threat continues to look low for now. Scattered showers may redevelop behind the main line of convection associated with the cold front thanks to wrap around moisture from the low pressure system. With both the HRRR and NAMNest depicting this, have chance to likely PoPs through the end of the near term. Latest QPF guidance has come in lower than previous runs, showing 2- 3" along and near the Blue Ridge Escarpment and 0.5-1.0" elsewhere. Locally higher amounts are possible, especially along the southern Blue Ridge Escarpment, where rainfall totals near 4" are possible. WPC has a Marginal Risk for Excessive Rainfall in place across the western Carolinas and northeast Georgia for Thursday, so isolated flooding cannot be ruled out (especially for locations along and near the southern Blue Ridge Escarpment). Luckily, temps will remain warm enough behind the front for all liquid precip. Highs on Thursday should be similar to today`s but may be limited somewhat by cloud cover and rain. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 230 PM Wednesday: The short-term period begins as a 500mb, negatively tilted shortwave trough axis moves over the region from the south and west. Current CAM guidance suggests that the primary axis of heavy rain and storms will have moved well east of the I-77 corridor by the time the period starts, and it is true that convective complexes tend to outrun the responsible storm as well as the guidance forecasting it. PoPs will therefore be rapidly trending down Thursday night, with isolated to scattered shower activity associated with the upper-level trough lingering into the early overnight hours. A few residual upslope showers may develop along the TN state line in the stout westerly flow through Friday morning, but the primary story will be the strong pressure-gradient winds behind the trough through Friday. At this juncture, the overall meteorological setup looks favorable for widespread 30-40mph gusts during peak mixing Friday afternoon as the attendant surface low deepens to near 980mb over Ontario and strong 50-75kt mid-level winds interact with a very deep (5-6kft) mixed layer across the forecast area. Wind Advisory gust criteria is >45mph and guidance continues to suggest that some areas may reach this threshold, especially across the higher elevations of the foothills and mountains, where the ground level is closer to the stronger winds aloft and mixing will be most effective at bringing a portion of those winds to the surface. Wind gusts exceeding 50mph are not out of the question at elevations greater than 4500-5000 feet from mid-morning Friday into the early overnight hours. However, we are still four forecast periods out and blend guidance typically overestimates the gust potential. Therefore, we will highlight this potential threat in the HWO for now and reevaluate our confidence in Advisory criteria for the next package. While winds will be strong behind the departed frontal system, they will predominantly be westerly, not northwesterly, and therefore the source region advecting into the area will be from the central Plains, not Canada. Therefore, we will cool down on Friday, but modestly so, with downsloping likely to mitigate CAA east of the mountains, where high temperatures will only be a few degrees below normal. Across the mountains the effects of lower thicknesses underneath the longwave trough and CAA will be a bit more pronounced. Therefore, highs are expected to top out 7-9 degrees below normal. An embedded shortwave trough will deepen the longwave trough extending from the southern Appalachians north into Canada Friday night and the longwave trough axis will quickly propagate east to the Atlantic Coast by Saturday morning. Thicknesses will increase during the day on Saturday as low-amplitude ridging builds east from the Plains and surface high pressure propagates underneath the inflection point along the Gulf Coast. Therefore, winds will remain gusty as our area is still within a weakened pressure gradient and mid-level winds remain strong in the NW flow aloft behind the trough axis, but peak gusts will be lower than those on Friday and well below Advisory criteria. Nevertheless, RH values may bottom out in the lower to mid-20s Saturday afternoon and combined with the remnant gusty winds fire weather may be a concern. Temperatures will quickly rebound on Saturday, with highs 3-5 degrees above normal area wide. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 230 PM Wednesday: The extended period looks to be mostly quiet and warm across the forecast area as upper-level ridging gradually amplifies into the middle of next week in response to a strong closed low ejecting out of the southern Rockies. This system will not directly impact our area through the period, but its upstream effects will result in high temperatures reaching the lower 80s in the mountain valleys and the mid-80s points east Monday through Wednesday, which is 8-12 degrees above normal. Low temperatures will be 12-15 degrees above normal each night, and may not drop out of the 60s for much of the Piedmont Tuesday and Wednesday nights as dewpoints slowly increase through the work week. A backdoor cold front will struggle to reach our area Monday and some of the guidance squeezes out a bit of moisture along the front, so a slight chance of upslope showers cannot be ruled out across the mountains and possibly the NW Piedmont Tuesday into Wednesday. The proximity of the front will increase cloud cover, especially overnight each day, limiting radiational cooling. Otherwise, the forecast looks dry. Early in the period, RH values bottom out in the upper 20s on Sunday and Monday with wind gusts of 15-20mph possible each day. Therefore, fire weather may be a concern. However, with increasing moisture, afternoon RH values looks to bottom out in the mid- to upper 30s Tuesday and Wednesday so fire weather concerns will diminish as the work week progresses. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... At KCLT and elsewhere: An active TAF set in store with a vigorous low pressure system tracking up the TN Valley pulling a cold front across the Carolinas and NE GA. The first concern will be se/ly gusty winds which develop ahead of the cold front arnd TAF issuance or a couple hrs later. Winds will remain elevated with low-moderate gusts as they begin to veer and become sw/ly by the early afternoon. A strong llvl jet will traverses the area overnight and this will lead to LLWS at 2 Kft due to speed changes on the order of 40-50 kts beg after sunrise lasting thru noon or the early afternoon. Still expect a chance of thunder as the main convg line passes east, which will generally occur during a 3-4 hr window arnd sunrise thru late morning. CIGs will also drop to IFR before midnight across most terminals and stay down, before lifting or scattering to MVFR/VFR by the early to mid afternoon. Outlook: Gusty winds will linger Thursday night into Friday, with the strongest winds expected on Friday. VFR conditions persist Friday into the weekend as high pressure builds across the terminals. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...AR/SBK SHORT TERM...JMP LONG TERM...JMP AVIATION...SBK
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1129 PM EDT Wed Apr 10 2024 .SYNOPSIS... A series of waves will cross the region through the end of the work week with increasing humidity, cloud cover, and showers escalating to widespread rainfall. While some places will be mild and humid, others toward the Gulf of Maine are likely to remain cool and humid with onshore flow. In any case, a ripening and melting snowpack combined with rain will lead to river and stream rises, with a chance for minor flooding. A passing cold front on Friday will introduce gusty winds, potentially strong along the coast. Winds remain gusty heading into the weekend with scattered showers. && .NEAR TERM /UNTIL 7 AM THURSDAY MORNING/... Update...Rain largely moving out of the area at this hour and I have adjusted PoP accordingly. We will maintain WAA over the low level cold dome...and this should result in drizzle breaking out over time tonight. At this time this is mainly closer to the mtns...or very near the coast...but I think expansion is likely as the night goes on. I will continue to show a elevation assisted pattern to the drizzle coverage. Previous discussion...Little change expected in the near term portion of the forecast. Latest radar imagery this afternoon continues to indicate showers advancing into our forecast area from southwest to northeast. The back edge as of 18Z was over northeastern Pennsylvania. This coverage is more robust than the latest HRRR solution. In any case, showers will be predominantly confined to southern portions of the forecast area overnight as the precipitation slides south. There will be some patchy drizzle and fog overnight with a raw southeast wind coming in off the Gulf of Maine. Overnight low temperatures will be fairly uniform tonight, ranging from the upper 30s in the north to the lower 40s in the south. && .SHORT TERM /7 AM THURSDAY MORNING THROUGH FRIDAY/... On Thursday, a backdoor cold front will begin to turn northward as a warm front. While the day will start out with relatively low pops, the chance for showers will increase during the day as a moist southerly gradient increases over the region as low pressure tracks well to our west. Patchy drizzle and fog can be expected once again with winds off the Gulf of Maine and plenty of low level moisture in place. Afternoon high temperatures will reach the 50s over southern New Hampshire and the Connecticut River Valley with chilly 40s elsewhere. A moist low level jet will enter the region Thursday night. Scattered showers with patchy drizzle will switch to an all out steady moderate rain over the region. Patchy fog will continue during this period with temperatures bottoming out in the 40s. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... High Impact Weather Potential: * Minor river flooding likely on Friday with overland flooding possible as well. * Strong southerly winds will near advisory levels along the coast Friday. Gusty west winds continue into Saturday but not likely to necessitate headlines. --Pattern and Summary-- +NAO will allow for a progressive pattern across North America through the long term forecast period. A longwave trough across the central portion of the CONUS today will deepen as it pushes east into the eastern United States Friday/Saturday with heights slowly building in its wake by Sunday into early next week as west- northwest flow remains over the region. Beyond this...troughing over the southwestern United States will eject north and east with building downstream heights and the potential arrival of shortwave energy over the northeastern United States by the end of this forecast period Wednesday. The most impactful weather of the period looks to be as the period opens on Friday as rainfall and snowmelt combine for a flood threat. A gradual moderating trend is expected through the long term with high temperatures below normal for Friday...warming to a bit above normal by the middle of next week. --Daily Details-- Friday: Deep southerly flow continues through the day ahead of low pressure over the Great Lakes with a 1.5" PWAT plume overhead but rapidly pushing east ahead of triple point & associated surface cold front. Best forcing for ascent will be early in the day until frontal passage...with afternoon precipitation becoming showery in the moist...cyclonic post-frontal flow. The high PWAT airmass and good mid level forcing should allow for moderate rainfall rates through the morning...which will bring our greatest potential for overland flooding. See hydro section below for more details on the flood potential. Winds: Southerly winds at H9 reach 75-80kts with warm advection scenario allowing for only pretty shallow mixing. This suggests a 35-40kt gust potential along the coast which nears our wind advisory criteria. The flow trajectory suggests some downslope potential across far northern NH and western ME as well. Mid morning-mid afternoon appears to be the best potential for the strongest gusts. Temperatures: Temps at H8 will be at or above 10C to start the day...settling back to +3-5C by late afternoon in the post frontal airmass. Highs will be determined mostly by mixing and any breaks in the clouds which appear most likely across southern NH. Here...expect highs to push into the middle 60s...with 50s to the north and east of this...and coastal communities likely stuck no higher than about 50 given the onshore flow. Saturday/Sunday: Cold advection continues Friday night into Saturday with the longwave trough axis overhead. Moist...cyclonic flow and decent lapse rates below H7 suggest showery conditions to continue on Saturday with precipitation increasingly taking the form of snow in the mountains. The airmass dries significantly pushing into Sunday which will allow for a drier...and somewhat warmer day...particularly south of the mountains where highs may near 60F as T9s rebound above +7C. We/ll have to watch a northern stream wave that the model consensus pushes just south of our area Sunday evening/Sunday night which may prolong the unsettled weather. Monday/Tuesday: A weak high pressure ridge axis arrives for the beginning of the week...which combined with a dry airmass /PWATS around 0.25"/ should allow for a quiet start to the week with some questions on how much temperatures moderate as the GFS/GEFS advertises a bit more of a northerly component to the low and mid level flow the the ECMWF/EC-EPS more northwesterly. Will follow temperatures above seasonal norms...with 50s in the mountains and 60s elsewhere. Wednesday: By the middle of next week...there is strong agreement on low pressure in the western Great Lakes with warm advection ongoing over our area with moisture also increasing. There is some spread among the various guidance members as to the arrival of a warm front and associated precipitation chances. At this range...mentioning the chance for showers is prudent though at this range...ensemble signals suggest a relatively light rainfall event which would not be a significant flood concern. This increase in clouds and associated shower chances will mean somewhat lower high temperatures to end the forecast period...but likely remaining above normal. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... Short Term...MVFR conditions will continue through the evening hours with ceilings occasionally falling to IFR in showers and patchy fog. Overnight, more widespread IFR conditions can be expected with a few pockets of LIFR in low clouds. Similar conditions will continue on Thursday with widespread IFR conditions in low ceiling with drizzle and fog at times in addition to the showers. Thursday night will continue to have IFR conditions in moderate rain with patchy fog and localized LIFR conditions. Long Term...LIFR CIGS/VSBYS with rain and fog along with gusty /20G30kt/ south-southeasterly winds for the morning Friday with improving conditions arriving from southwest to northeast through the day. Showery conditions with occasional MVFR restrictions will persist under moderate winds from the west for Saturday. VFR conditions are expected to dominate Sunday-Monday with westerly winds continuing. && .MARINE... Short Term...Moist southeast winds will continue tonight and Thursday over the coastal waters. Areas of drizzle and fog will reduce visibilities in addition to scattered showers. The gradient increases Thursday night over the region as low pressure tracks well to our west. Seas will continue to build as well. Long Term...Southerly gales likely Friday/Friday evening as strong low pressure moves through the Great Lakes region and north of New England. Gusty west winds continue through Saturday with SCA conditions continuing. Winds/waves will subside for Sunday and Monday as weak high pressure builds towards the region. && .HYDROLOGY... A flood watch is in effect for the snow covered portions of the Western Maine Mountains and Northern New Hampshire. The rain through Thursday will act to compress, warm, and ripen the snowpack, but the heavier rain Friday morning will be the catalyst for flooding. The combination of strong winds and high dew points (50s) over an isothermal snowpack will lead to rapid melt with expectations up to 4” SWE loss. Complete melt-out below 2,000 ft is likely, particularly on S/SE facing slopes. The flood risk will be focused Friday morning as moderate to heavy rainfall pushes through ahead of a cold front. The current QPF forecast is for 1 to 3 inches in the mountains, less on the north facing slopes. However, the PWATs are 2-3SD above normal, and with a moisture feed to the Gulf we should be prepared for locally higher amounts. Melt combined with saturated antecedent conditions sets up ideal conditions for potential flash flooding and moderate river flooding in the Upper Merrimack (Pemi), Saco, Androscoggin, and Kennebec basins. Small streams draining in the steep terrain could experience flash flooding. This melt will route downstream, causing potential flooding impacts on low elevation rivers as well. Outside of the snow covered areas, locally heavy rainfall may elicit poor drainage and nuisance flooding in urban areas, especially if heavier rainfall totals materialize. && .TIDES/COASTAL FLOODING... Very high astronomical tides will continue tonight with the tide in Portland at 11.4` (MLLW). A southeasterly flow off the Gulf of Maine will allow for a modest storm surge tonight, will allow Portland to reach its 12 foot flood stage. Hampton should come in around its 11 foot flood stage as well. High astronomical tides will continue through the end of this week, albeit, lowering with time. Future coastal flooding this week will rely on whether or not significant storm systems will line up with the higher of the high tide cycle which currently is the overnight hours this week. .GYX WATCHES/WARNINGS/ADVISORIES... ME...Flood Watch from late Thursday night through Friday afternoon for MEZ007>009-012>014. Coastal Flood Advisory from midnight tonight to 3 AM EDT Thursday for MEZ023-024. NH...Flood Watch from late Thursday night through Friday afternoon for NHZ001>005. Coastal Flood Advisory from midnight tonight to 3 AM EDT Thursday for NHZ014. MARINE...Gale Warning from 5 AM to 11 PM EDT Friday for ANZ150>154. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Flood Watch from late Thursday night through Friday afternoon for MEZ007>009-012>014. Coastal Flood Advisory until 3 AM EDT Thursday for MEZ023-024. NH...Flood Watch from late Thursday night through Friday afternoon for NHZ001>005. Coastal Flood Advisory until 3 AM EDT Thursday for NHZ014. MARINE...Gale Warning from 5 AM to 11 PM EDT Friday for ANZ150>154. && $$ NEAR TERM...Legro
Area Forecast Discussion
National Weather Service Indianapolis IN
1004 PM EDT Wed Apr 10 2024 .KEY MESSAGES... - Rain Tonight and Thursday; Cool - Minor Flooding possible - Rainfall in the next 48 hours will may prolong ongoing river flooding at a minimum, and lead to some renewed lowland flooding along main stem rivers. - Active weather pattern continues into next week with numerous chances for rain and storms. - Above normal temperatures in the 70s Sunday into most of next week. && .FORECAST UPDATE... Issued at 1002 PM EDT Wed Apr 10 2024 Periods of light/moderate rain overnight will contain embedded heavier rates and possibly briefly training showers as was seen earlier this evening in both Knox and Morgan/Johnson Counties. Isolated areas of ponding of low-lying areas and minor flooding can be expected tonight...especially if any organized rain manages to maintain itself over the smaller region that had picked up 1.00-2.00 inches last night between Brown County and Rush County. Greatest chances of heavier additional rainfall should be over western and possibly northern counties where isentropic lift along approaching system`s warm frontal zone will be focused. 12-hr rainfall through dawn Thursday should be 1,00-1.50 inches for most locations...with embedded areas surpassing 2.00 inches. Easterly flow around 10KT to be maintained overnight as circulation approaches from the SSW. Readings in mainly the 55-60F range amid the moist environment to hold or perhaps drop slightly with lows in the 50s. Fog development is possible in any slackening in rainfall rates, although sustained winds should be high enough to prevent major visibility deterioration. Previous Mesoscale Discussion follows... Broad area of rain continues to lift across Central Indiana this evening. Some pockets of moderate to heavy rain is located within a corridor of Sullivan county to Marion county, where more robust collision and coalescence is taking place to parcels and allowing for larger more efficient hydrometeors to reach the surface. This area is also still seeing isentropic ascent to parcels through a moist column, further aiding in the efficiency to the steady rainfall. Surface OBS indicating some reduced VSBY within the steadier rain along and south of the I-70 corridor. Satellite imagery is indicating some cooling to cloud tops along the Ohio River and lifting north, while underneath radar reflectivity has some pockets of convection that has developed. && .SHORT TERM (This evening through Thursday)... Issued at 300 PM EDT Wed Apr 10 2024 Synopsis: Surface analysis this afternoon shows a frontal boundary stretching from north of Richmond to Columbus and then south of Vincennes. Surface high pressure was found over Lake Huron and Lake Erie. Cool easterly surface flow was in place across much of the forecast area and dew points across northern Central Indiana were in the 40s, while the southern half of the forecast areas had recovered with dew points in the mid 50s. Radar mosaics show an area of showers over southwest Indiana and west Central KY pushing northeast within the flow aloft. Aloft, water vapor imagery showed a deep upper trough over the southern plains states. This was resulting in moist southwest flow streaming northeast into the Ohio Valley. The upper trough was producing much stronger storms over LA and Arkansas. Tonight... The upper trough over the southern plains is expected to push northeast, becoming negatively tilted in the process. Forcing dynamics ahead of the system are suggested to push in to the Ohio Valley and Central Indiana as the evening progresses. The lingering lower level boundary will act as an area of lower level convergence while the forcing provided aloft provides additional lift. Isentropic surfaces also remain in play. The 300K GFS Isentropic surface shows some lift surging into the area this evening and specific humidities are over 6 g/kg. Forecast soundings also show a saturated column through much of the night across Central Indiana with pwats over 1.3 inches. Finally, HRRR shows a shield of rain showers expected to develop and surge into Central Indiana this evening and early overnight. CAPE is limited with this feature, but given the warm and moist air and lapse rates that are marginal unstable, a stray embedded thunderstorm cannot be ruled out. Thus expect the main precipitation to be rain showers. Given the clouds, precipitation and steady easterly flow, nearly steady state or slightly cooling temps toward wet bulbs will be expected. Expect lows in the lower to middle 50s. Thursday... Models show the negatively tilted upper trough slowly swinging through Indiana and the Ohio Valley through the day. The mid levels keep a saturated trough in place over Central Indiana through the day, as the surface low is expected to quickly push east of the state. This will allow the winds to become northwesterly. The associated tight pressure gradient across the area will allow for gusty winds of 20-30 mph also. Strong lower level cyclonic flow will also remain in place, allowing for the development of scattered wrap around rain showers. Forecast soundings are not as saturated on Thursday as they were previously, as dry air begins to intrude into the system, however still plenty of lower level moisture will still remain present. Pwats on Thursday start over 1 inch and by late afternoon fall to around 0.75. HRRR suggests scattered showers through the day, gradually diminishing by late afternoon. Thus will again use high pops on Thursday for scattered rain showers, with lessening pops through the afternoon as dry air intrudes from the northwest. Given the expected clouds, rain, and cold air advection, little temperature movement will be expected through the day. Look for high temperatures only a few degrees warmer than the previous lows, in the middle to lower 50s. && .LONG TERM (Thursday night through Wednesday)... Issued at 300 PM EDT Wed Apr 10 2024 An active pattern continues through the end of the work week and into next week with numerous chances for rainfall and storms; however temperatures remain largely above normal for this time of year through the period. .Thursday night and Friday... A strengthening surface low, aided by phasing jet energy aloft, tracks NE through the state Thursday then slowly away to the northeast into Quebec on Friday. Guidance is in great agreement with a strong upper wave diving SE into the state behind the departing low Thursday night into Friday morning, keeping the chance for convective showers around. By 12z Friday, a negatively tilted upper trough axis is right on top of the state with Indiana in the left exit region of an 110kt jet streak over IL and MO. Steepening low and mid level lapse rates from CAA on the backside of the surface low in addition to saturated low levels and 20-30 kt 0-1km and 0-3km shear will result in an environment conducive for convective showers late Thursday night into the first half of the day on Friday. With such a strong 35-45 kt low level jet overhead and steep low level lapse, expect breezy conditions during this time as well with frequent gusts over 40 mph likely. Higher wind gusts are also possible in any convective shower as well. Would not be surprised to see small hail or graupel as well with the strongest showers as freezing levels lower to around 3,000 ft by Friday morning. Drying trend expected through the daytime hours Friday as higher pressure and much drier air advect into the region. Friday will likely be the coolest day over the next week with afternoon highs struggling to even reach the 60 degree mark. .This Weekend into Next Week... An extended period of well above average temperatures and storm chances arrives this weekend and persists into next week. Ridging at the surface and aloft will expand into the Ohio Valley for the weekend. Ridge axis remains over the Plains through Monday placing Indiana with an upper level northwesterly flow pattern. Longer range guidance does show the potential for waves of energy within the NW flow to bring storm chances Late Sunday night and then again on Monday night. This is a classic late Spring to early summertime pattern with southerly flow and a warm, humid airmass at the surface with waves of energy flowing NW to SE along the jet. Unfortunately, guidance does not handle the smaller details such as timing and placement of these waves of energy very well. While high confidence exists in well above average temperatures in the 70s (and maybe 80s!) next week, lower confidence exists on storm track, timing, and location. Will have to watch where the upper level storm track sets up, which will determine where these potential clusters of storms set up and track. Some guidance has these storm clusters pushing into Indiana, while others keep the storms further north. For now keeping only 20-30 POPs in the Sunday - Monday forecast and will adjust up or down in future forecast packages as timing and location become clearer. This will not be a wash out type event, so expect most of these days to remain dry before and after the storms. Not ruling out the threat for a strong to potentially severe storm associated with these thunderstorm complexes. Upper ridging shifts eastward mid week with numerous stronger storm systems moving through the Plains. This places Indiana within a warm, southwest flow pattern within the warm sector of storm systems to the west. While much warmer, above normal temperatures continue, the threat for more storms remains in the forecast. At the moment, the current storm track looks to remain west of the Ohio Valley midweek as dying frontal systems and associated storms push into the region. There are some hints in the guidance that the storm track does move further east over the Ohio Valley by late week bringing more frequent and widespread chances for rain and storms, but confidence this far out on details remains low. For now, high confidence exists in a much warmer weather pattern with periodic to daily chances for storms. Do not expect any particular day to be a washout this weekend into the first half of next week; however will keep a close eye on the weather pattern later next week for potential repeated rounds of heavy rain and storms. Lower confidence exists with timing and placement of daily threats for storms. It is too early to talk about the severe or flooding threat with storms mid to late next week, however not ruling out the possibility. && .AVIATION (00Z TAF Issuance)... Issued at 755 PM EDT Wed Apr 10 2024 Impacts: - IFR/possible LIFR ceilings to prevail through at least 18Z Thursday...although MVFR at KLAF to begin period - Mainly IFR/MVFR visibility into THursday morning...with low-IFR/ brief LIFR possible in heavier rain - Isolated non-severe TSRA are possible overnight, with best chances at KBMG Discussion: A storm system centered over the Lower Mississippo Valley early this evening will intensify while lifting towards the Midwest tonight... before crossing the region Thursday morning. Scattered to widespread light to moderate rain showers will fall under mainly IFR ceilings tonight, with generally IFR/MVFR visibility lowered in heavier rains and any subsequent fog formation. Non-severe TSRA are possible tonight, but chances too low outside of KBMG to include in TAF. Winds will remain sustained around 10 knots overnight from easterly directions...except more norhteast at KLAF. Wind directions will change through the early Thursday timeframe as the surface circulation crosses the region. Gustier northwest flow will then advance across the region from west to east Thursday afternoon behind the deepening, departing system...with gusts to at least 20- 30KT after 18Z Thursday. Kept VCSH for Thursday with low confidence on location and timing for the few to scattered showers that will accompany the passing system, although periods of steadier rain will certainly be possible. Conditions should improve quickly from IFR to VFR during the afternoon for KLAF/KHUF...and probably towards sundown at KIND/KBMG. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ UPDATE...AGM SHORT TERM...Puma LONG TERM...CM AVIATION...AGM
Area Forecast Discussion
National Weather Service San Francisco CA
522 PM PDT Wed Apr 10 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 212 PM PDT Wed Apr 10 2024 Our warming trend is well underway across the Bay Area and Central Coast and will continue tomorrow and potentially into Friday. The latest forecast has a delayed onset of rain showers with locations across the North Bay being impacted first late Friday afternoon and evening. Rain and embedded thunderstorm chances spill southward late Friday and into the day on Saturday. The better thunderstorm risk will be confined to the offshore waters, though coastal areas of Santa Cruz and Monterey have a low potential for a rumble of thunder or two. It`ll turn sharply colder this weekend with rebounding temperatures next week. && .SHORT TERM... (This evening through Thursday) Issued at 212 PM PDT Wed Apr 10 2024 As discussed earlier, the potential for fog/low stratus across the coastal areas has increased a bit more tonight into Thursday morning. As T-Td spreads diminish, mostly clear skies (except some passing high clouds) and reduced surface-925mb flow will encourage a bit more in the way of fog. If high clouds are really dense, then fog may struggle to develop. Speaking of struggling, HREF guidance yesterday didn`t appear to capture the evolution of this morning`s fog and appears to offer low probabilities for tonight. However, forecast soundings from afternoon RAP guidance, along with some of the NBM guidance support inclusion of patchy fog with visibilities of 2-4 miles across the North Bay, parts of the SF Peninsula, and across a good portion of the Central Coast. Guidance indicates that areas across Monterey Bay will stand the best chance (around a 30-40% chance) to see visibility slip below 1 mile. Visibility reductions may be observed as far inland as the Salinas Valley, but given the shallow nature of saturation (less than 1000 feet), it`s probable that any nocturnal drainage flows will keep the boundary layer sufficiently mixed to curb the dense fog potential. Given that the chance for visibility to fall below 1 mile is confined to a small area, dense fog headlines are not anticipated. Motorists are still urged to exercise caution when commuting late tonight into early Thursday morning as sudden changes in visibility may occur. With the shallow nature of the marine layer, fog and low clouds should dissipate by mid-morning Thursday, though will linger through the early afternoon hours offshore. As advertised earlier this week, Thursday will be one of the warmest days we`ve seen since last Fall. Record high temperatures are safe, but we`ll continue to see a minor heat risk for most of the area. This means that those sensitive to the heat (elderly and infants) may succumb to heat-related illnesses. We encourage individuals across the area (especially interior locales such as the Santa Clara Valley, Salinas Valley, and San Benito County) to hydrate adequately with water and take breaks in the shade if working outside. Never leave children or pets unattended in vehicles. High temperatures are forecast to range between the mid to upper 50s along the coast to upper 70s to even mid-80s across interior sections. There`s still a bit more spread in the max temperature forecast along coastal sections. The marine layer isn`t overly deep and so I do anticipate mixing will erode any low clouds/fog prior to peak heating. However, if areas stay socked in with clouds/fog, highs along the coast may struggle to get out of the mid 50s. && .LONG TERM... (Friday through next Tuesday) Issued at 212 PM PDT Wed Apr 10 2024 Friday Onward....Some noteworthy alterations were made to the PoP/QPF grids. Thanks to EKA, STO, HNX, and EKA for the coordination. This entire week, model guidance has slowed the progression of the upper trough that will be responsible for our wetter and cooler conditions this weekend. Blended guidance rain amount probabilities have trended lower and with some of the higher resolution NWP now available, it seems prudent to update PoP/QPF to match our IDSS messaging. These alterations result in rain chances being confined to areas across extreme northern portions of the North Bay during the daylight hours on Friday. While a stray shower or two (or sprinkles/drizzle) cannot be ruled out for locations farther south, however, confidence is increasing that most locales will remain rain-free. While cloud cover will inhibit heating, I did adjust temperatures upward closer to the 75th percentile of the NBM on Friday afternoon which means most areas away from the coast will see high temperatures in the upper 60s to low 70s. Forcing for ascent increase late Friday into Saturday as our main upper storm system arrives. Upslope flow across the higher terrain (Santa Cruz Mountains, Santa Lucia Range, and Mayacamas) will promote some orographically enhanced precipitation, but the primary band of showers may not enter parts of the North Bay until closer to 10pm Friday night. Rain chances peak during the pre- dawn hours on Saturday with values averaging between 60 and 80 percent. As the upper low attempts to scoot eastward through the day on Saturday, this feature will slow down and the 500mb low forecast may reside across the northern portions of our marine zones during the afternoon hours on Saturday. This will encourage additional onshore flow on Saturday and thus additional rounds of precipitation. With widespread cloud cover and rain, Saturday will not be an ideal day for outdoor activities and temperatures will remain in the 40s and 50s which will be quite the change from the middle portion of the week. The unidirectional flow through the troposphere will promote training of convective cells and rain bands over a given area, thereby increasing the potential for minor flooding. The greatest potential for excessive rainfall, as highlighted by the Weather Prediction Center, appears that it`ll reside across the Big Sur coastline, however, any robust convective cell over a more urbanized area may promote minor flooding. As it pertains to the potential for thunderstorms, forecast instability values from deterministic guidance suggest that the greater risk resides across the offshore marine areas. Some instability does build on Saturday afternoon, however, it`s quite meager. In fact, the potential for CAPE values over 100 J/KG are around 30%. This translates to a low potential for a rumble of thunder or two on Saturday afternoon. Chances for CAPE values over 100 J/kg are closer to 60% across the marine zones. 700-500mb lapse rates do steepen around 7.5 C/km offshore and so there remains some potential for waterspouts (beyond 40-50 miles from the Central Coast). Snow levels do appear that they`ll fall down sufficiently such that a few snow flakes or very light snow showers unfold across central and southern portions of the Santa Lucias. At this time, measurable snowfall is not expected. With the slower progression of the upper low, 20-40 PoPs linger through the day on Sunday. With the upper low traversing the region, the cooler pocket of air aloft will shift overhead during peak surface heating across southern Monterey/San Benito counties. As such, lapse rates steepen Sunday afternoon across southern Monterey and San Benito counties and I`ve inserted just a 20% chance for isolated storms here. Severe weather is not expected, but storms may be efficient at producing larger quantities of hail. Heading into next week, we`ll see mid-level ridging set up across the region which should limit the opportunities for precipitation. Temperatures will rebound and we will be well on our way to near or above normal warmth. && .AVIATION... (00Z TAFS) Issued at 520 PM PDT Wed Apr 10 2024 VFR with some high clouds across the area. Winds vary in direction but mostly onshore flow with moderate to breezy speeds. Expect winds to become light overnight. With the strong ridge and compressed marine layer, expect another round of some low visibility and low clouds early Thursday morning for most terminals. Moderate confidence on ceiling heights but expect a mix of MVFR, IFR, and LIFR conditions starting near 12-14Z. VFR will return after 18Z with mostly clear skies. Vicinity of SFO...Currently VFR with breezy N/NW flow before diminishing overnight. Confidence is increasing that the terminal will see a reduction of flight category tomorrow morning to MVFR. Winds will be breezy with speeds up to 15-16 knots out of the west again tomorrow afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Currently VFR with moderate northwesterly flow. Winds will diminish overnight which will allow for some lower visibility and ceilings causing a mix of IFR to LIFR conditions overnight with KMRY seeing low ceilings near 07Z and 13Z for KSNS. && .MARINE... (Tonight through next Tuesday) Issued at 520 PM PDT Wed Apr 10 2024 High pressure over the Eastern Pacific Ocean will dominate the forecast through tomorrow, allowing for fair weather and fresh to strong northerly breezes to prevail over the coastal waters. Long period northwesterly swell will continue to build through the waters through today before beginning its abating trend tomorrow. Friday, a deep upper-level low will bring renewed chances for rain, gusty winds, thunderstorms, and hazardous seas to the coastal waters through the weekend. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 PM Thursday to 9 AM PDT Friday for Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 9 AM PDT Friday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Bain LONG TERM....Bain AVIATION...SO MARINE...SO Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea
Area Forecast Discussion
National Weather Service Nashville TN
854 PM CDT Wed Apr 10 2024 ...New UPDATE... .UPDATE... Issued at 854 PM CDT Wed Apr 10 2024 Relatively quiet evening thus far with showers clearing out of the area for now. Will begin to see an additional wave of showers and thunderstorms move into the area mainly after midnight, bringing and additional half inch to inch of rain. This evening`s sounding shows hardly any CAPE with weak lapse rates, but a PWAT at 1.23". There does not appear to be any major concerns heading into the overnight hours. Could see a few thunderstorms in the fix that could lead to heavy rainfall, otherwise any strong/severe weather does not look likely. Pressure gradient will increase overnight and tomorrow ahead of a low pressure system moving through the area, likely kicking winds up overnight and through much of the day tomorrow. Some areas may flirt with Wind Advisory criteria, but overall most should remain below 40 mph gusts. Best chance to see gusts close to that would be across the Cumberland Plateau. Have adjusted PoPs and temps over the next 36 hours given latest thinking, otherwise rest of the forecast is on track and will be updated in full here in a few hours. && .SHORT TERM... (Rest of today through Thursday) Issued at 1200 PM CDT Wed Apr 10 2024 Chances of showers with isolated to scattered thunderstorms will be possible across mid state region through Thursday afternoon as surface frontal system now based across southern MS River Valley Region pushes northeastward and associated upper level low digs across southern MS River Valley Region northeastward into mid state region by morning hours on Thursday before pushing northeastward also. Leaned toward latest HRRR model solution for rainfall coverage across our area through at least the evening hours tonight. Total rainfall amounts this afternoon through Thursday will generally range 0.50" - 1.0." A strong thunderstorm here or there can not be ruled out, but stronger convection should generally remain well to our south. Lows tonight will mainly be in the 50s with highs on Thursday mainly mid 60s to lower 70s. && .LONG TERM... (Thursday Night through next Wednesday) Issued at 1200 PM CDT Wed Apr 10 2024 Shower and thunderstorm chances will diminish west to east across our area as Thursday evening progresses, with maybe some lingering showers across northern portions of Upper Cumberland Region after midnight Thursday and possibly lasting through the day on Friday as continued weak shortwave passages aloft occur across this area. Otherwise dry conditions will prevail through Monday afternoon per prevalence of surface and generally a pattern of building upper level ridging influences. Showers and thunderstorm chances will return to our area as Monday afternoon into next Wednesday afternoon progresses, as southerly low level atmospheric flow becomes increasing established across our region as a large synoptic frontal system takes shape across most of eastern half of CONUS and southwesterly upper level flow becomes increasingly progressive. After lows Thursday night generally around seasonal normal values spanning the mid to upper 40s with highs on Friday remaining a few degrees below seasonal normal values mainly spanning the 60s, a significant warm air advection pattern will begin to develop resulting overnight lows through first part of next work week mainly in the 60s with afternoon high values mainly in the low to mid 80s, upper 70s to around 80 Cumberland Plateau Region. && .AVIATION... (00Z TAFS) Issued at 611 PM CDT Wed Apr 10 2024 Light showers will diminish this evening and we will get a break in the rain for several hours. Our next line of scattered rain will move in after 05z and a few isolated thunderstorms will also be possible. Showers will linger during the morning with another line of showers and thunderstorms developing from west to east after 14z. Cigs will rise into VFR levels for a time this evening but will return to MVFR overnight and will continue at MVFR into tomorrow. IFR/LIFR will be possible with any thunderstorms. Things dry out from west to east after 22z. Breezy southerly winds gusting up to 25 knots, the strongest winds will be tomorrow morning into the afternoon. && .PRELIMINARY POINT TEMPS/POPS... Nashville 60 70 48 68 / 100 100 30 10 Clarksville 57 67 47 67 / 100 100 30 10 Crossville 57 67 43 59 / 80 100 40 10 Columbia 56 67 46 67 / 100 90 30 10 Cookeville 59 68 46 61 / 80 100 40 10 Jamestown 58 69 43 59 / 80 100 50 20 Lawrenceburg 58 66 46 67 / 90 90 30 10 Murfreesboro 59 69 46 67 / 100 100 30 10 Waverly 53 65 46 67 / 90 90 20 10 && .OHX WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE.......Adcock SHORT TERM...JB Wright LONG TERM....JB Wright AVIATION.....Mueller
Area Forecast Discussion
National Weather Service Pocatello ID
300 PM MDT Wed Apr 10 2024 .SHORT TERM...Today through Thursday Night. Early afternoon satellite imagery shows a broad H5 ridge of high pressure over the WRN CONUS which will continue to lead to warm and dry conditions across CNTRL and ERN Idaho through Thursday. Highs in the 40s/50s/60s today will increase around 5-10 degrees for Thursday to the 50s/60s/70s as the ridge axis shifts directly overhead. 15-20 kt 700 mb winds today supporting gusts to around 15-25 mph will increase later in the day Thursday and through the overnight hours Friday to around 20 to 35 kts supporting wind gusts to around 20-35 mph, especially in the mountains. Conditions will continue to remain dry through Thursday evening as increased cloud cover builds in out of the west as shallow moisture moves atop the ridge. This will support some isolated shower chances primarily in the higher terrain Thursday night as conditions remain predominantly dry. MacKay .LONG TERM...Friday through next Wednesday. Well...for better or for worse...the long-term portion of the forecast continues to feature a whole massive pile of active wx for southeast Idaho. Over the last few days we`ve been discussing a couple different potential scenarios for the evolution of our next main trough/low pressure storm system for this weekend...hold that thought, we`ll look at that momentarily. One thing that has remained quite consistent in the forecast from model run to model run for a couple days now though has been Friday, featuring a weak, initial shortwave trough riding up the front/leading edge of the main approaching trough. This feature...barely detectable in height analysis and weakening with time...is negatively tilted, which can be a synoptic red flag for potential strong to severe t-storms. Despite the weakening nature of the shortwave, it should still provide some broad ascent, and every mid-range to long- range model IS in fact generating at least some isolated shower/t-storm activity coincident with diurnal heating Friday afternoon. A first look at NBM-projected SBCAPE (which we honestly haven`t evaluated extensively yet but is based on multi-model, ensemble-based, calibrated guidance) suggests a marginal but adequate 200-400 J/kg SBCAPE (instability to support updrafts and storm strength), while the NAMNest (which is often a bit overzealous or at least falls near the upper-end of the guidance envelope) advertises as much as 400- 900 J/kg SBCAPE...with a sounding near Burley hinting at 30-35kts of both effective and 0-6km deep-layer bulk shear as well as very strong low-level lapse rates. Bottom line...while we`ll need to continue to evaluate the potential for strong t-storms as more guidance comes in...Fri looks convective, with otherwise continued south flow ahead of the main approaching trough continuing to support warm temps averaging 15 degrees above normal for mid-April (highs in the mid-60s to mid-70s for nearly all population centers). Okay...now the main event. A main approaching trough of low pressure will manufacture a solid-looking closed low along the coast of CA by Sat. 500mb height cluster analysis Sat continues to hint at the two possible scenarios we`ve been watching for this low, with two clusters (about 45% of the ensemble membership) supporting a slightly stronger/more anomalous closed low quite disconnected from the remnant nrn branch of the trough that will progress inland slower and bring a later pattern change to SE Idaho, and two clusters (about 55% of the ensemble membership) supporting a slightly more intact and progressive overall trough (even with a closed low still advertised as the srn branch) that brings cooler, wetter conditions inland to SE Idaho as much as 36-48 hours earlier. These ensemble percentages almost sound like a flip-flop from this time yesterday when the first scenario was more strongly favored, but we note that ALL clusters have trended toward a much more similar timing/position solution for the closed low compared to the differences we saw 24-48 hours ago...ALL keeping the low well the SW of our CWA. Thus, confidence continues to increase (and is now pretty high) that temps Sat will end up remaining warm and almost identical to Fri with southerly flow in place. Also, despite a first chance of precip Fri, upper-level support associated with the low might remain far enough SW of our region that Sat may end up leaning mostly dry for most of our forecast area, and NBM PoPs have slowly been decreasing in line with this conceptual expectation. Moving forward to Sun, we see the same two scenarios, with the clusters supporting a more intact overall trough and slightly weaker closed low behaving more progressively with a trough axis near or already over SE Idaho (60% support), and the clusters supporting a slightly stronger closed low as the main player lagging back over central CA (40% support) leading to YET ANOTHER very warm day, although perhaps with an increasing trend in shower potential. The more progressive solution would cool temps (and slow mid-elevation snowmelt) by Sun with increasing showers, while the delayed solution would support another warmer, drier day with continued snowmelt...thus some potential implications here extending to the flood forecast for the Portneuf River (more on that in the HYDROLOGY section below). Interestingly, the 12z deterministic model suite seems to be leaning toward the slower solution, despite the ensemble percentages just mentioned. Thus, confidence remains low on whether Sun will side with spring, or side with a pattern change toward cooler, wetter wx. Whether our pattern change arrives in earnest by Sun, or by Mon, all models advertise yet another organized closed low pressure system dropping out of Canada toward nrn Idaho, with cluster analysis suggesting uncertainty in how quickly this system arrives. At this time, it doesn`t look like there will be much of any chance for a break (MAYBE Mon night?), with NBM guidance and all long-range models showing widespread rain/snow across the region on Tue. High temps will have already started cooling Mon, but we take another 10 degree hit by Tue with highs only in the 40s to near 50. By this time the western half of the nation is firmly enveloped in massive long-wave troughing, and there are some indications that Tue`s low either slows down and lingers in our area, or is replaced by yet another deepening low in the region, either of which would keep cooler, wetter wx going into Wed and likely beyond. We note that deterministic models have some wildly conflicting solutions by mid- week as far as details are concerned, but chances are pretty high in that cooler, wetter, unsettled wx dominating for most of next week. By the way, breezy conditions...first out of the south Fri/Sat and then more out of the west thereafter...are expected each day throughout the forecast, although so far holding below advisory criteria. - KSmith && .AVIATION...For the 18Z TAFS through 18Z Thursday. A ridge of high pressure has finally taken hold across the nrn Rockies and will reign as the dominant synoptic wx enforcer both today and Thu, supporting high forecast confidence in dry, mostly sunny/clear, VFR conditions for all terminals. Modest winds checking in at 10kts or less today may trend just a touch higher out of the WSW for Thursday, and sfc conditions will remain too dry for any fog or low stratus concerns. We do carry some passing high clouds in the TAFs over much of the period (generally FEW180) based largely on the HRRR (which tends to pick up on high-level cirrus the best and even perhaps over-advertises these shields) but with some hints of support from upstream satellite observations over the PacNW too. That said, no real impact is expected for aviation for the next 48 hours, and there is perhaps a 40% chance that SKC will be favored over much in the way of high clouds. Looking ahead, an approaching shortwave trough will more noticeably increase winds by Friday afternoon and support at least isolated showers and thunderstorms for some terminals. - KSmith && .HYDROLOGY... As has been discussed for several days now, the Portneuf River continues to be our only river of concern for flooding at this early stage of our spring flood season, with very warm temps averaging 15 degrees above normal by Fri and Sat supporting increasing snowmelt, especially at mid-elevations in the basin. Our latest collaborated forecast with the Northwest River Forecast Center continues to bring the river back into minor flood stage in the Pocatello area by early Friday morning, and then to moderate flood stage by early Sunday morning. This potential crest above moderate flood stage has PERHAPS trended SLIGHTLY higher in the forecast over the past 48 hours...increasing from about 10.0 feet to about 10.3 feet...but otherwise no significant changes or trends are noted, and resultant impacts should be approximately the same with lowland flooding along the river, flooding into Sacajawea Park and other trailheads in western Pocatello, and significant flooding of agricultural land in the Blackrock area and also down in Inkom near the confluence of the Portneuf River and Marsh Creek. A FLOOD WARNING remains in effect until further notice. A bit further upriver near Lava Hot Springs, the forecast for the Portneuf River at Topaz continues to carry bankfull conditions (action stage) with the river perhaps getting close to that minor flood threshold. As discussed in the LONG TERM section above, the evolution of this weekend`s approaching low pressure system will have SOME impact on the river forecast...the more progressive solution with the low arriving by Sun will bring cooler temps earlier slowing snowmelt, while the delayed solution with the low arriving Mon will extend snowmelt and may eventually support SLIGHTLY heavier QPF, although overall QPF amounts in either scenario look pretty modest at this juncture (with no response on the ECMWF Extreme Forecast Index for QPF amounts), thus runoff from snowmelt continues to be the driving factor. Cooler and wetter wx is expected next week, and it`s uncertain exactly how this will affect the river forecast as cooler temps will slow snowmelt, but actively falling QPF could keep river flows up. Stay tuned. REMEMBER... despite recent warm air temps...the water in all of our rivers, creeks, and streams largely originates from melting mountain snow and is dangerously cold this time of year. Be especially careful to keep children away from the water. - KSmith && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$
Area Forecast Discussion
National Weather Service Tallahassee FL
1106 PM EDT Wed Apr 10 2024 ...New UPDATE, MARINE, HYDROLOGY... ...ADDITIONAL ROUNDS OF STORMS EXPECTED OVERNIGHT INTO TOMORROW MORNING WITH SEVERE WEATHER AND MORE FLASH FLOODING POSSIBLE... .UPDATE... Issued at 1054 PM EDT Wed Apr 10 2024 The main updates to tonight`s forecast were adjusting hourly rain chances and corresponding wx grids to account for the latest trends. Widespread rain (heavy at times) with embedded thunder is ongoing across much of the Tri-State area. This activity has flourished ahead of an energetic upper cyclone traversing the MS Valley while aided by a robust low-level jet and localized mesoscale lows amidst an anomalously moist airmass. The most prominent impact the past several hrs has been flooding for parts of the FL Panhandle into SE AL & SW GA where Flash Flood Warnings are currently in effect. Multiple ambient weather stations have reported amounts of 3+ inches and some reports of flooding from Panama City, Dothan, and Rehobeth. Secondary impacts are strong/gusty winds away from thunderstorms with a myriad of 40+ gusts being common dating back to the afternoon, especially along the coast. A Wind Advisory remains in effect for most of the service area until tomorrow afternoon. Additional convection is evident just to our west and SW ahead of the cyclone`s attendant cold front, particularly over the Gulf where storms are more potent. The latter will be monitored closely for a secondary severe-weather threat round as it approaches the coast and spreads inland in a northeastward fashion during the overnight hrs. Our FL counties appear to be more vulnerable than locations northward. Damaging gusts and tornadoes remain the primary threats. Additional rainfall is a concern for areas already affected from the 1st/ongoing round, though the FL Big Bend looks to be in the crosshairs for potential flooding. A Flood Watch remains in effect nearly areawide until tomorrow afternoon. Please be sure to have ways to be awoken by any warnings tonight. && .NEAR TERM... (Through Thursday) Issued at 149 PM EDT Wed Apr 10 2024 Near: A large mid-upper trough will continue progressing across the southeast with an attendant surface low currently situated over western MS. This low should begin occluding to the northeast through the remainder of today. Southeasterly flow is persisting and will continue through the duration of the event advecting deep moisture across the area. As the low occludes, a cold front will extend into the CWA and serve as the primary forcing mechanism for storms beginning this afternoon lasting through tomorrow afternoon. Two rounds of severe are possible with this setup with the first being the QLCS propagating toward our area and the second occurring Thursday morning through the afternoon. For the first part of this system beginning momentarily, the low- level jet will continue strengthening as the upper trough amplifies with 850mb winds reaching 70+kts. This will increase bulk shear substantially across the area with values reaching 60-70kts out of the west-southwest. Notably large looping hodographs are evident across the area with high SRH nearing 400m2s2, perhaps higher locally if surface winds remain out of the southeast. The main caveat with this setup is instability with MLCAPE values seemingly struggling to reach 500J/kg as a result of cooler midlevels. Sine cloud breaks are evident, indicating that instability could rebound somewhat ahead of the line. Regardless, a high-shear low-CAPE event appears likely as low-level streamwiseness of the hodographs (0-3km) is quite textbook, resulting in a tornado threat for the majority of the area despite meager buoyancy. A couple strong tornadoes (EF-2+) are also possible across our SE AL and FL Panhandle counties. A damaging wind threat is also likely given the strong low-level wind field with this system. Storms will then dissipate as a brief lull in the LLJ takes place before ramping up once again with 850mb winds in excess of 70kts as the cold front traverses the area early tomorrow morning. Storms will then reinvigorate along the cold front, perhaps maintaining semi-discrete features as westerly effective shear in excess of 55kts overspreads the region. It appears that a frontal feature will be lifting over the FL Panhandle and Big Bend as the MCS to the north dissipates, resulting in instability increasing with MLCAPE reaching around 1000-1500J/kg and SRH reaching around 400m2s2. This is indicative of an increasing tornado threat, some possibly strong (EF-2+), with a particular emphasis for our westernmost FL Panhandle counties west of the Apalachicola River. A damaging wind threat and perhaps some hail is also possible as lapse rates steepen with a push of cooler air aloft steepening lapse rates. A failure mode exists with the second round of storms. If the antecedent convection to the north over our SE AL and SW GA counties produce stronger outflow than forecast, the air farther south may stabilize enough inland to inhibit convection substantially. Regardless, an all-hazards threat exists across all of our counties this afternoon through tomorrow afternoon, especially for our SE AL and FL Panhandle counties. WPC currently has all of our SE AL counties, portions of our SW GA counties, FL Panhandle counties, and portions of our inland FL Big Bend counties outlined in a Moderate Risk (3/4) for excessive rainfall with nearly all of our CWA outlined in a Slight Risk (2/4) for excessive rainfall, excluding the easternmost FL Big Bend. More on this below in the Hydrology section. Overnight lows will drop into the mid to upper 60s with highs tomorrow in the upper 70s to low 80s. && .SHORT TERM... (Thursday night through Friday night) Issued at 149 PM EDT Wed Apr 10 2024 Cold front and upper low exits eastward Thursday night with surface high pressure translating from east Texas into southern Alabama by Friday night. Decreasing clouds are on tap Thursday night with sunshine plentiful Friday. Highs will be in the mid/upper 70s Friday and lows in the upper 40s to lower 50s each morning. && .LONG TERM... (Saturday through Tuesday) Issued at 149 PM EDT Wed Apr 10 2024 Surface high pressure slides off the east coast this weekend while mid level ridging builds across the eastern third of the US in response to an upper low racing over the desert southwest at the beginning of the next work week. Mid level flow will remain mostly from the northwest, despite a mid level trough moving across the midwest. The strength of the ridge will deflect the trough to the north leaving fairly tranquil conditions in the extended. High temperatures will reach for the mid/upper 80s early next week and lows will bottom into the mid/upper 50s. && .AVIATION... (00Z TAFS) Issued at 742 PM EDT Wed Apr 10 2024 Poor flying conds to continue for much of this TAF period thanks to widespread SHRA/TSRA with embedded heavy rain, gusty winds, and low cigs/vsbys (IFR-MVFR). Evening radar has the bulk of the convection affecting ECP/DHN/ABY. Another round of storms is expected overnight into the morning hrs and looks to pose a severe threat from west to east ahead of a front. Used the latest HRRR to help time the onset of +TSRA via tempo groups. Weather improves tmrw after FROPA, but gusty west winds are expected. && .MARINE... Issued at 1054 PM EDT Wed Apr 10 2024 Boating conditions deteriorate overnight ahead of a strong frontal system poised to sweep through the waters. Maritime convection associated with this activity will continue to pose a strong wind, and waterspout threat. Southerly gales, especially gusts, are still expected away from thunderstorms followed by a sharp wind shift out of the southwest to westerly in the front`s wake late tomorrow morning to about midday. Winds should be at or near advisory levels on Thursday despite improved weather while seas aim to subside even more slowly. Favorable conditions arrive on Friday as lighter northerly breezes develop in response to high pressure building in. && .FIRE WEATHER... Issued at 149 PM EDT Wed Apr 10 2024 Storms are expected to exit the area by tomorrow afternoon leaving a wetting rain behind. Following the passage of a cold front, transport winds 25-30mph out of the west will overspread the region tomorrow with mixing heights reaching up to 5000ft. This will yield high to very high dispersions areawide tomorrow afternoon. High dispersions areawide are also possible on Friday as elevated transport winds persist out of the northwest. MinRH will drop to around 40-60% tomorrow afternoon with 30-50% possible Friday. Otherwise, there are no fire concerns at this time. && .HYDROLOGY... Issued at 1054 PM EDT Wed Apr 10 2024 Minor to moderate riverine flooding is now forecast for the Choctawhatchee, Pea, Chipola, Flint, Apalachicola, and Ochlockonee basins. River Flood Warnings were issued this evening where confidence is highest based on observed rainfall dating back to earlier this afternoon. More Flood Warnings are likely tomorrow morning based on what additional amounts accumulate overnight. For coastal flooding, a Coastal Flood Warning remains in effect from Wakulla County eastward to Dixie County. The tide around 4 am ET Thursday morning is not quite aligned with the peak surge, so with it being a bit offset, water levels may not get quite as high as possible, but the strong winds behind the squall line will be sufficient to produce enough surge combined with a higher high tide around 2 pm ET to produce water levels of 2 to 4 feet above normally dry ground within the warning area. A coastal flood advisory has been issued for areas in Franklin County where water levels should be slightly less. && .SPOTTER INFORMATION STATEMENT... Spotter activation is requested. Spotters should safely report significant weather conditions and/or damage by calling the office or tweeting us @NWSTallahassee. && .PRELIMINARY POINT TEMPS/POPS... Tallahassee 66 80 54 77 / 90 80 0 0 Panama City 66 74 58 74 / 90 20 0 0 Dothan 65 75 51 74 / 100 10 0 0 Albany 66 78 52 74 / 100 60 0 0 Valdosta 68 81 54 76 / 90 90 0 0 Cross City 66 77 55 77 / 90 90 0 0 Apalachicola 67 74 59 72 / 90 60 0 0 && .TAE WATCHES/WARNINGS/ADVISORIES... FL...Flood Watch through Thursday afternoon for FLZ007>019-026>028- 108-112-114-115-118-127-128. Wind Advisory until 2 PM EDT /1 PM CDT/ Thursday for FLZ011-013- 016>019-026. Wind Advisory until 11 AM EDT /10 AM CDT/ Thursday for FLZ007>010-012-014-015-027-108-112-114-115-118-127. Wind Advisory from 2 AM to 2 PM EDT Thursday for FLZ028-029-034- 128-134. High Rip Current Risk through late Friday night for FLZ108-112- 114-115. High Surf Advisory until 5 AM EDT /4 AM CDT/ Friday for FLZ108- 112-114. Coastal Flood Advisory until 8 PM EDT Thursday for FLZ115. High Surf Advisory from 2 AM to 2 PM EDT Thursday for FLZ115. Coastal Flood Warning until 8 PM EDT Thursday for FLZ118-127-128- 134. GA...Flood Watch through Thursday afternoon for GAZ120>131-142>148- 155>161. Wind Advisory until 2 PM EDT Thursday for GAZ123-125-127>131- 142>148-155>161. AL...Flood Watch through Thursday afternoon for ALZ065>069. Wind Advisory until 1 PM CDT Thursday for ALZ068-069. GM...Gale Warning until 3 PM EDT Thursday for GMZ730-755-765-775. Gale Warning until 10 AM CDT Thursday for GMZ750-752-770-772. && $$ UPDATE...IG3 NEAR TERM...Worster SHORT TERM...Scholl LONG TERM....Scholl AVIATION...IG3 MARINE...Scholl/IG3 FIRE WEATHER...Worster HYDROLOGY...Godsey/Merrifield/IG3