Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/06/17

Area Forecast Discussion
National Weather Service WAKEFIELD VA
955 PM EDT Wed Apr 5 2017 .SYNOPSIS... Strong low pressure moves east from the mid Mississippi Valley tonight into the Great Lakes region. This system will bring strong to severe thunderstorms to the local area late tonight through Thursday morning. Low pressure intensifies while tracking to the northern Mid Atlantic region on Thursday, pushing a strong cold front through the area by afternoon. High pressure builds in through the weekend. && .NEAR TERM /THROUGH THURSDAY/... High confidence for significant severe weather threat early Thursday morning through midday. Widespread damaging winds, large hail, and tornadoes are all possible. Evening Update... Some changes were made mainly to affect timing of severe convection Thursday morning. Earlier showers/tstms over the Southeast are pushing off the Southeast coast this evening, with some showers tracking across NE NC. The airmass has stabilized in the immediate wake of this activity from Ern GA nwd through the central Carolinas and into VA. Meanwhile, intense convection is occurring from Ern AL/Wrn GA nwd through the Tennessee Valleys ahead of the main cold front. The instability to the N (Ohio Valley) is progged to diminish overnight, with instability eventually recovering to the lee of the Appalachians late tonight into early Thursday morning, roughly 08-12Z. The last few runs of the HRRR have delayed the onset of intense convection until after 12z locally and moving off the coast between 16-17z Thursday. Otherwise, expect PoPs of only 20-40% overnight under a mostly cloudy to overcast sky with near steady temperatures from the mid 50s NE to low/mid 60s S. Synoptic Overview: Deep/anomalous upper trough becomes negatively tilted tonight as a strong speed max rounds the base of the trough. The upper low lifts toward the Great Lakes region, with the associated surface low lifting over the Ohio Valley. The warm front over the Carolinas quickly lifts through the area this evening as a strong cold front approaches from the west. Strong height falls ahead of lifting shortwave energy from the Deep South will induce surface cyclogenesis over the Piedmont late tonight/early Thursday morning. Rapid intensification of the surface low will result in winds backing to the southeast underneath a strengthening southwest low level jet. Strong low level moisture flux will result in the advection of a seasonably moisture rich air mass ahead of the developing low and cold front. These features in tandem with impressive forcing for ascent will result in widespread showers and thunderstorms late tonight into early Thursday morning. Following along with hi-res guidance, showers associated with the warm front diminish/push offshore around 05Z, with a lull expected through 08-10Z before the significant weather develops thereafter. A line of showers/thunderstorms approaches from the west, but interacts the mountains late tonight. Once the cold front pushes over the Piedmont and the meso-low develops, expect showers and thunderstorms to develop over the Piedmont, and rapidly push across the local area through mid morning Thursday. Parameters and dynamics favor strong to severe thunderstorms as the line pushes across the area. Additional showers are possible mid to late morning along the cold front, but the severe threat will quickly diminish behind the initial line. The shortwave and cold front quickly push offshore midday Thursday as a dry slot overspreads the region. The surface low continues to deepen, lifting northward into the Northeast. The cold pool aloft and lingering mid level moisture will result in instability driven showers and thunderstorms Thursday afternoon across the area. Mid to upper levels begin to dry out, so not anticipating more than gusty winds and locally heavy rainfall out of the strongest storms. Otherwise, southwest winds increase to 15-25 mph with gusts of 25 to 35 mph (strongest near the coast) Thursday afternoon. Highs Thursday in the upper 60`s to low 70`s. Hazards: Theta-e advection and an elevated mixed layer (currently visible over the Deep South) will lead to steepening mid-level lapse rates and CAPE values of 500-1000 j/kg late tonight. While only marginally unstable, backing in the winds will increase both directional and speed shear. CSTAR SHERBE values greater than 1 and 0-3km EHI greater than 1 support organized convection along the line and the potential for tornadoes. Potential also exists for discrete cells ahead of the line. Shear will favor rotating updrafts and the potential for tornadoes. The line quickly organizes due to the strong shear, with storm motions of 50+ knots overtaking any discrete cells quickly. Then the concern becomes widespread damaging winds with broken line segments. Large hail is also expected as instability exists in the mixed phase layer. Tornado threat continues due to the shear and broken line segments. Wind gusts of 60+ mph are possible across a large part of the region. The great tornado threat will generally be along the triple point low, from central to southeast Virginia (including the Virginia Eastern Shore) to northeast North Carolina. Damaging winds and large hail are more of a concern over the northwest, north and northeast local area. Theta-e rich air mass will favor heavy rainfall, but the fast storm motion will limit overall flooding potential. However, some minor flooding is possible where a comma head might develop near the triple point. Timing: Timing for the greatest severe potential will be Thursday morning through midday, from roughly 6am to noon. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/... Secondary cold front pushes offshore Thursday night, resulting in cooler temps and cloudy conditions. Lows in the low to mid 40`s. Broad cyclonic flow remains over the region Friday as another disturbance rounds the upper low over the Northeast. Have slight chance POPs across the northeast local area for light precip. Sky averages mostly cloudy north to partly cloudy south. Highs Friday only in the mid to upper 50`s. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Long term period will feature dry weather with increasing temps through the period. For Fri night/Sat, a cold front pushes farther offshore with NWly CAA flow over the Mid Atlc leading to high temps Sat only in the upr 50s/lwr 60s. Strong sfc hi pres over the SE states Sat night slides off the SE coast Sun, allowing winds to bcm sly Sun aftn with temps rising into the mid 60s to near 70F. S/SW winds increase Mon under strong WAA, with temps climbing into the mid/upr 70s most areas. Dry also for Tue with south flow ahead of the next approaching cold front...highs again mainly in the mid/upr 70s to near 80F. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... Low pressure over the lower Ohio Valley will move northeast into northern Ohio Thursday morning. A Secondary low will form over western Virginia then move north to absorb into the primary low over New York State in the evening. A trailing cold front will move across the region Thursday afternoon. An overcast sky will prevail through midday Thursday which will lower to MVFR/IFR Thursday morning. Scattered showers and thunderstorms will be possible after Midnight and especially toward dawn. Some thunderstorms will likely be severe near or after daybreak. Gusts to over 50 knots will be possible in thunderstorms from 10 to 16z at the TAF sites. Gusty southwest winds to around 30 knots will occur in the afternoon. There will be partial clearing but there will be a lingering chance for thunderstorms through 00Z Thursday evening. OUTLOOK...Deep low pressure pulls slowly to the northeast with high pressure building into the Mid Atlantic States through the weekend. The high will then move off the coast with dry weather and mainly VFR conditions continuing through Monday. && .MARINE... A complex area of low pres affects the area over the next couple days with strong SCA conditions still forecasted over all wtrs. For tonight, SE flow slowly ramps up to ~15 kt by midnight with a warm front in the vicinity. Meanwhile, seas builds to 4 ft out 20 nm. SCA conditions commence everywhere Thu morng as a triple-point low and associated pres falls occur over VA. S winds Thu morng will shift to SW Thu aftn as the low races off to the N/NE. Strong to severe tstms are psbl until midday Thu with this systm. 15-25 kt winds with gusts to 30 kt continue through Thu night. Expect occasional gusts up to gale force but with this mainly SWly WAA flow ahead of the cold front, maintained inherited SCA headlines, and will re-evaluate tonight. Seas up to 7-8 ft out 20 nm with waves over the Bay up to 4- 5 ft. 20-30 kt west winds into Fri before winds start to decrease Fri night/Sat. Improving marine conditions thereafter into Sun as broad sfc hi pres builds south of the area. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 7 AM Thursday to 7 PM EDT Friday for ANZ633-635>638. Small Craft Advisory from 4 AM Thursday to 7 PM EDT Friday for ANZ630>632-634-650-652-654-656-658. && $$ SYNOPSIS...LKB/SAM NEAR TERM...SAM/LKB/AJZ SHORT TERM...LKB/SAM LONG TERM...MAS AVIATION...LSA MARINE...MAS
Area Forecast Discussion
National Weather Service Bismarck ND
940 PM CDT Wed Apr 5 2017 .UPDATE... Issued at 936 PM CDT Wed Apr 5 2017 No significant changes to the going forecast. Did tweak sky cover just a bit with some mid cloud lingering in the far southwest, and maybe some high clouds pushing into the west after midnight. Updated text products will be sent shortly. UPDATE Issued at 629 PM CDT Wed Apr 5 2017 High pressure over Manitoba will continue to drop southeast tonight, into the eastern Dakotas. This is expected to bring mostly clear skies and light winds to the forecast area. Currently, isolated showers continue to dissipate as they slide south across the area. Previous forecast had a good handle on convection ending shortly after 00 UTC. Considering the location and forecast track of the surface high and the drier dewpoints under the high, we lowered temperatures a little over the eastern half of the CWA. One possible consideration for late tonight will be stratus/fog. RAP and HRRR continue to indicate the potential for a narrow band of stratus/fog along the periphery of the return flow on the west side of the surface high, over southwest ND. Current BUFKIT soundings indicate only a very shallow layer of moisture near the ground. For now will not add a mention of fog/stratus. Text products will be sent shortly. && .SHORT TERM...(This evening through Thursday) Issued at 332 PM CDT Wed Apr 5 2017 Current surface analysis places low over the Ohio River Valley with high along the Saskatchewan/Manitoba border. Upper level analysis places ridge building over the western CONUS, with modest short wave sliding through the northern plains. Isolated to scattered showers have developed over the area in modest cyclonic flow. For the rest of today into tonight...showers will continue through the afternoon, ending in the evening with the loss of daytime heating. A clap of thunder will not remain out of the question. Quiet weather then expected overnight. Quiet weather with warmer temperatures Thursday as ridge works its way towards the area. .LONG TERM...(Friday through Wednesday) Issued at 332 PM CDT Wed Apr 5 2017 Ridge continues to push into the area Friday into early Saturday with temperatures pushing into the mid 60s to mid 70s with dry conditions. Upper flow becomes southwest as ridge axis pushes to the east by mid-day Saturday, with precipitation chances entering the forecast by Saturday evening. For the start of the upcoming week...models are still having trouble placing some key features from run to run and between each other. With that said, the overall pattern suggests a notable drop in temperatures along with precipitation chances throughout the area. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 936 PM CDT Wed Apr 5 2017 Latest iterations of the RAP/HRRR have now almost completely backed off on the fog/stratus in the southwest late tonight. Will pass along to the next shift but no plans at this time for a mention of fog in any of the TAFS Thursday morning. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...TWH SHORT TERM...JJS LONG TERM...JJS AVIATION...TWH
Area Forecast Discussion
National Weather Service Caribou ME
1032 PM EDT Wed Apr 5 2017 .SYNOPSIS... Weak high pressure builds in overnight into early Thursday. An occluded front will cross the area Thursday night. Low pressure will slowly move across the region Friday through Saturday. && .NEAR TERM /THROUGH THURSDAY/... 1030 PM Update: IR satl imagery showed clouds hanging on across the region as light se winds set up. Hrly temps were adjusting using the latest obs which show temps holding in the 30s. A slight dip in temps expected overnight especially across the far n and w. Stayed close to the daycrew`s thinking of some fog and drizzle later on w/the RAP soundings showing this potential. Previous Discussion... A decaying frontal system and associated upper level shortwave have been slowly moving across the forecast area today with progress slowed by a blocking ridge to the east. The biggest net effect has been strong low level moisture advection with low clouds, drizzle and some snow showers towards Aroostook County. This scenario continues to play out tonight as the high to the east further strengthens and expands westward while the front continues to decay. This means the low level moisture will stay trapped under a strong subsidence inversion tonight with clouds, light rain and drizzle, upslope fog, and temperatures falling just a few degrees. There will be some freezing drizzle in northern and western zones...especially above 800 to 1000 feet. This will occur later tonight into Thursday morning. All of the moisture is low sleet seems unlikely. On Thursday morning, the flow will turn southerly as the Canadian Maritimes high retreats. This maritime flow will enrich already saturated low levels and cause even more widespread light rain and drizzle Thursday morning. However, the main event in terms of rain begins later in the afternoon as a powerful shortwave rotates around a closed upper low in the Eastern Great Lakes. Steady, and perhaps heavy rain, will break out after 4 pm. With a strong upper level jet approaching the coast, some upper level instability is possible by evening. Fog will become more widespread in the southern half of the forecast area later in the day with the relatively warm and moist air and high temperatures for the day will be posted in the evening rather than the usual mid-afternoon. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... A vertically stacked surface/upper low across western New England will draw an occluded front across the region Thursday night. An area of rain will cross the region in advance of the occlusion Thursday night, with decreasing rain chances in the wake of the occlusion. The heaviest rain is expected Downeast and across the favored upslope areas of Piscataquis county where rain totals could exceed an inch. Rainfall across northern areas is generally expected to be between three quarters of an inch and an inch. The surface/upper low will then slowly drift northeast across the region Friday through Saturday. Expect showers, most numerous across the north and mountains, to persist Friday through Saturday. Generally expect the showers to remain in the form of rain Friday through Saturday. However, with cooling temperatures aloft, the rain could mix with snow across the north and mountains Friday night. Otherwise, expect mostly cloudy skies across the region Friday through Saturday. Temperatures will be at near normal, to slightly above normal, levels Friday/Saturday. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... The surface/upper low begin to exit across the maritimes Saturday night while high pressure builds east toward the region with decreasing clouds. High pressure crosses the region Sunday. A warm front will lift across the region Monday with mostly cloudy skies north and partly cloudy skies Downeast. Uncertainty then exists Monday night into Tuesday night regarding whether the front remains north of the region keeping the forecast area in the warm sector or whether the front moves back south with more extensive clouds, shower chances and cooler temperatures. A cold front is then expected to cross the region Wednesday with a chance of showers. Temperatures are expected to be at above normal levels Sunday into Monday. Temperatures Tuesday into Wednesday will be dependent on the eventual location of the frontal boundary. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... NEAR TERM: IFR cigs and vis due to drizzle or snow showers will continue into this evening. The low cigs and drizzle continues tonight and location such as FVE and GNR could have freezing drizzle later tonight. Most locations...especially BGR, GNR, BHB and vicinity will be LIFR or VLIFR in fog later tonight. Cigs will lift to IFR later Thursday morning...before decreasing again with moderate to heavy rain by evening. SHORT TERM: IFR/LIFR conditions are expected across the region Thursday night. Occasional MVFR conditions are expected across the region Friday. Occasional MVFR conditions are expected across mostly the north and mountains Saturday. Generally expect VFR conditions across the region Sunday into Monday. && .MARINE... NEAR TERM: Will convert the current SCA to an SCA for hazardous seas. The intracoastal waters will probably fall below criteria for the hazardous seas this evening, but the outer waters seem likely to maintain the SCA until after midnight. After seas and winds diminish later tonight into Thursday morning, conditions will deteriorate with an approaching frontal system later in the day. This system will probably bring a lot of fog with the winds. Have continued to cut wind gusts from guidance due to the stable nature of this frontal system. SHORT TERM: Small craft advisory conditions are expected across the waters Thursday night into Saturday. Visibilities will be reduced in rain and fog Thursday night, with a chance of showers Friday into Saturday morning. && .HYDROLOGY... Currently, NOHRSC maps show 10-20 inches of snow depth and SWE of 3-6 inches for parts of southern Piscataquis and central Penobscot counties. This area could also receive around an inch of rain from Thursday afternoon through Thursday night. Yesterdays river survey covered rivers in this area, and reports that the Piscataquis was largely ice free up to Milo. At this time, it does not appear that ice jam flooding is a major threat for this region but still needs to be monitored as some still resides back on the headwaters of the Piscataquis River. Across the northern Maine rivers, the ice jam flooding threat continues above normal. Rainfall of three quarters of an inch to around an inch is possible across the region Thursday night along with melting snow. This will lead to rising river levels. Warmer temperatures early next week will lead to increased snowmelt and river rises across the north which could cause ice to begin to move. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT Thursday for ANZ050>052. && $$ Near Term...Hewitt Hydrology...Hewitt
Area Forecast Discussion
National Weather Service State College PA
1156 PM EDT Wed Apr 5 2017 .SYNOPSIS... An intense early spring storm will move through the region Thursday. The storm will move up into southern Canada Thursday night and Friday ushering in blustery and colder weather in its wake. Temperatures will begin to moderate Saturday, rising to above normal through the first half of next week. && .NEAR TERM /THROUGH THURSDAY/... Radar beginning to pick up the leading edge of the rain moving into eastern Ohio. The HRRR continues the idea of the chances for rain ramping up over the next 2-4 hours. PWAT vales between 0.5-0.75 of an inch will rise to over one inch after midnight tonight as the broad axis of a southerly 45-55kt LLJ in the 925-850 mb layer slides east across the state. Couple this with increasing/mdt-strong large scale lift, strongly diffluent flow aloft and elevated instability (with a 850 mb lifted index of -1 to -4C) and we`ll see a widespread/steady light to moderate rain, with periods of heavy rain and a few thunderstorms after midnight. Rainfall by 12Z thursday should average between 3-7 tenths of an inch with the greatest amounts occurring over the western mtns. Low temps tonight will vary from the mid 40s up north, to the l50s in the south. && .SHORT TERM /THURSDAY NIGHT/... A very active and changing weather pattern is in store for the short term period as a strong southerly 45-55kt LLJ continues to pump very moist and unstable air across the shallow cooler airmass entrenched to the NE of a warm/developing occluded front over Central PA and the lower/mid Susq Valley Thursday. The near sfc-based LIs do dip negative in the southeast few counties for up to several hours during the afternoon Thursday as they get into the NW edge of the warm sector just to the south of the triple point of this occluding, sub-990 mb sfc low. SPC risk of severe weather on Day2 is Marginal, with the Slight risk area just barely to the south of the Mason-Dixon Line. Storm total rainfall will likely end up in the 1-2 inch range for most of the region, with a low probability for over 2 inches across the NW mtns and perhaps the Lower Susq Valley based on a blend of the SREF and GEFS. These amounts will lead to fairly significant rises on area rivers and streams, but for now MARFC forecasts based on current flows and anticipated QPF bring several points to between caution and FS, with no flooding forecast. The exact location of the QPF max is the biggest question at this point, and the heavy rain will be dictated by the extent and duration of south-north training of heavy SHRA/TSRA. GEFS and MARFC QPF max is painted a little further west than our (and the NAM/SREF) current storm total QPF of 1.75-2 inches across the North Central Mtns and Mid Susq Valley where we think the better and more persistent elevated instability axis will set up and meld into a potential region of nearly stationary 850-700 FGEN for a 6-10 hour period Thursday. The 525dam upper low will be over the Finger Lakes before sunrise Friday. The cold air (and sub-zero 850 mb temps) will rush in from the SW at first due to the occlusion and milder air wrapping around/into the big low. Gusty winds will accompany some of the white stuff as it mixes with the rain showers left after the occluded front passes. The nighttime and dropping temps should allow for a slushy accumulation on the high ground, mainly in the Laurels and far NW. Many folks could see the white stuff falling, but the April sun angle and not-so-marginal temps should limit accums to just the highest elevations, and even then, just in the nighttime/early AM Friday. Some showers will linger Fri night, and an additional coating is possible, mainly in the northern tier. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Upper level low Eastern PA and NY Friday with cold air wrapping in from western PA. Precipitation will be lighter and more intermittent transitioning to more showery in nature and with colder air, mixing in with snow over the north and western mountains. Snow expected in the higher elevations. Western mountain area and Northern tier will see temperatures Friday in the 30s. Warmer to the southeast over the Lower Susq Valley with highs in the upper 40s, hence and precipitation there will remain as rain. Friday night into Saturday the upper low will be sliding east across New England. North to northwest flow across lakes will create some lake enhancement and linger chances for showers across the northern tier of PA and down the Alleghenies thru the Laurel Highlands. Upper level ridge begins to build in Saturday with a warming trend and more sunshine. Afternoon temperatures begin to rebound under the April sun but northwest wind will still give it a chilly feel. By Sunday, the winds slacken and the April sun will make it feel even warmer as temperatures jump into the 60s. A short-wave is progged to pass over the ridge to our north and some clouds may be seen across the northern tier. Next system approaches late Monday with clouds working into the northwest and a possible pre-frontal trough. Some uncertainty with the timing of the cold front with this next system. GFS has a strong cold front moving east across PA on Tuesday where as the ECMWF brings it through Wednesday hence POPs are spread out in the forecast across those periods yet actual period for rain will be more like a 6 hour window. Temps will be notably colder behind the front with at least a mix with snow possible northwest mountains. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... Widespread VFR will continue through 06Z across much of central and southern PA. Between 06Z to 08Z the latest HRRR has the showers enveloping the southern and western TAF sites. Rain will continue to blossom overhead and move northeast across the region via a strong southerly low-level jet of 45-55kts. Included LLWS for all TAF sites overnight through much of Thursday morning as this low-level jet axis slides east across the state. Widespread MVFR with periods of IFR possible, especially at BFD. IFR cigs and vsbys should spread to most TAF sites by mid morning hours Thursday. Near the occluded front (as the cooler air filters in with light sfc wind during the late morning and afternoon hours Thursday) cigs could drop to LIFR/VLIFR (esp across the wrn mtns). The potential for strong convection Thursday is still not clear cut. Most areas may not see a lot of thunder, but widespread showers with periods of heavy rain will prevail, along with gusty winds. MDT and LNS are more in line to see more in the way of thunder (and a low probability for SVR convection) as sfc dewpoints climb into the l-m50s for a few hours during the afternoon hours. As such have VCTS in TAFS. Potential for moderately strong west to southwesterly wind gusts of 30-35 kt later Thursday afternoon and evening, depending on how strong the inversion will be, as a strong jet and dry slot works toward the area. Snow showers will be across the northern and western mountains on Friday, as a very deep low will be just north of the area. Gusty winds will prevail across the entire area. Outlook... Thu...Rain and sct thunderstorms with widespread restrictions. Windy. Fri...Rain/Snow showers NW. Elsewhere rain showers. Widespread restrictions. Windy. Sat...MVFR with sct shrasn early NW. Then no sig wx. Sun...VFR. && .HYDROLOGY... QPF remains in the 1-2 inch range for the tonight-Friday night period, with most of that falling tonight and Thursday. 3hr FFGs in the north are fairly low around 1", while the SE half of the area is very high (about 2-2.5"). Thus, the immediate threat for any minor flooding is in the north, but thunder is less likely there. Have chosen to continue to hold off on any flood watches. The short-term threat looks to be mainly nuisance/poor-drainage flooding over much of the area. The longer term threat is really only on the main stem of the Susq, and still around or less than 50pct to reach flood stages - which would not occur until late Friday or even Saturday. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Dangelo/Lambert LONG TERM...Dangelo/Steinbugl AVIATION...Lambert/Ceru HYDROLOGY...
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1020 PM EDT Wed Apr 5 2017 .SYNOPSIS... A strong cold front crosses our region tonight and moves off the East Coast on Thursday. Expect very windy conditions Thursday into Friday. Temperatures will be much below normal Thursday into the start of the weekend, then milder temperatures return into the first half of next week. && .NEAR TERM /THROUGH THURSDAY/... As of 1000 PM: We remain within the cool airmass created by in-situ cold air damming. Therefore sfc based parcels are still stable and most likely will remain so through the remainder of the evening. Two separate lines of convective activity are present over East TN and central GA, slowly moving into the CWFA over the next hour or so. The HRRR has generally indicated this activity surviving despite the loss of SBCAPE. Aloft, we still anticipate destabilization occurring as a deep upper trough translates overhead later tonight. It is still expected that a band of strong tstms will accompany or precede the front across the area, though they are expected to remain elevated. Effective shear should be enough to support supercells and threats of damaging wind and hail, though tornadoes no longer appear to be the primary threat--assuming the wedge does not erode. RAP progs of sfc theta-E continue to indicate the wedge front will retreat up into the Piedmont overnight, though those progs are a bit overdone at the current time, and with WAA ongoing aloft, erosion is unlikely. SPC downgraded nearly all of our area to Slight Risk on the D1 evening update, which seems reasonable. Revised PoPs focus the chances closer to the convective lines as they pass through overnight. A strong ulvl low builds in quickly aft the squall line bringing a good amount of llvl caa while the sfc p/grad increases sigfnt/ly. Soundings show shallow mixing across the mtns to arnd 50 kts and 40 kts or so non/mtns aft 12z Thu and persisting thru midnight Fri. So...will issue a HW.W for most mtns/fthills and HW.Y across non/mtns. Northwest flow snowfall will begin during the day, perhaps just as flurries until afternoon when profiles cool and ice crystal growth increases. Mins shud be right arnd normal while max temps will remain in the u50s non/mtns and L50s mtn valleys. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 2pm Wednesday: Main cold front will be well east of area and off the coast by Thursday evening with some rain/snow showers continuing with northwesterly upslope enhancement over the Southern Appalachians. Showers over the mountains gradually trail-off through Friday as dry advection proceeds. Snow totals are not expected to be significant, except at the highest elevations where several inches or more may occur. Main issue Thursday night/Friday will be wind potential. Powerful surface low tracks towards the Eastern Great Lakes with 850mb flow Thursday evening over the GSP area of 40 kts with enhancement over the mountains to 50 kts. Diurnal mixing under clear skies should give a surface wind reflection of some concern over all of the area, with the strongest winds and gusts over the elevated terrain. Winds continues all day on Thursday and will begin to trail-off late Friday morning, with some elevated wind potential through Saturday morning. Current high wind watch matches area of expected strongest wind gusts well. Skies will be clearing Thursday night/Friday with cold advection keeping highs on Friday 10 to 15 degrees below seasonal normal, and the coldest temperatures in the forecast Saturday morning, with a freeze or frost likely in the mountains and foothills of Western North Carolina, though continued wind and dry RH will mute the frost possibility in areas not expecting 2m temps below freezing. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 3pm Wednesday: From Saturday evening through Tuesday, weather pattern goes through a transition from northwesterly flow behind departing trough to 500mb ridging, followed by the next upstream system which may bring some showers by next Wednesday. Most of the extended forecast will be clear and dry with seasonally normal to 5 degrees above normal temperatures. EC generally agrees with quiescent forecast Sunday through Tuesday, with a better chance for precip by Wednesday afternoon. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... At KCLT and Elsewhere: A shallow and stable wedge airmass remains over the western Carolinas, encompassing all terminals. Moisture trapped within this airmass should permit widespread low MVFR to IFR cigs developing this evening. Relatively low-impact SHRA/TSRA could develop as well. Overnight, however, a cold front will sweep through. While that front is expected to scour out the restrictions, strong TSRA are expected to develop along it as both midlevel moisture advection and lapse rates increase over the wedge. Though most likely these storms will remain elevated, isolated damaging winds and hail will be possible. TEMPOs reflect the expected timing of the frontally driven TS. Winds shift to NW behind the front at KAVL, but remain generally S of W elsewhere. Expect strong gusts to develop by late morning and continue into Friday. At KCLT, westerly crosswind issues are likely late in the period. Outlook: Winds will remain very gusty thru Friday. Much colder air will continue to spill in behind the front, and may lead to some frost formation in spots Fri morning and especially Sat morning. VFR conditions should last into Monday. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 90% High 93% High 100% High 100% KGSP High 82% High 98% High 100% High 100% KAVL High 80% High 95% High 97% High 90% KHKY Med 72% High 83% High 100% High 100% KGMU Med 65% High 100% High 100% High 100% KAND Med 72% High 100% High 97% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...Wind Advisory from 8 AM Thursday to 8 PM EDT Friday for GAZ010- 017-018-026-028-029. Flash Flood Watch until 2 AM EDT Thursday for GAZ018-026-028- 029. NC...High Wind Warning from 8 AM Thursday to 8 PM EDT Friday for NCZ033-048>050-052-053-064-065-501-503-505-507-509. Wind Advisory from 8 AM Thursday to 8 PM EDT Friday for NCZ035>037-051-056>059-062-063-068>072-082-502-504-506- 508-510. SC...High Wind Warning from 8 AM Thursday to 8 PM EDT Friday for SCZ002-003. Wind Advisory from 8 AM Thursday to 8 PM EDT Friday for SCZ001- 004>014-019. Flash Flood Watch until 2 AM EDT Thursday for SCZ010-011-019. && $$ SYNOPSIS...DEO NEAR TERM...SBK/Wimberley SHORT TERM...WJM LONG TERM...WJM AVIATION...Wimberley
Area Forecast Discussion
National Weather Service Northern Indiana
850 PM EDT Wed Apr 5 2017 .SYNOPSIS... Issued at 749 PM EDT Wed Apr 5 2017 Widespread rain will affect the area tonight with an isolated thunderstorm still possible south of Route 24. As an area of low pressure begins to slowly lift northeast tonight, rain is expected to mix with or change to snow across the area late tonight and Thursday as colder air is drawn into the region with some light snow accumulations possible, especially across extreme northern Indiana, southern lower Michigan, and portions of northwest Ohio. Very windy conditions can be expected late tonight and Thursday with gusts in the 40 to 50 mph range. Some higher gusts near 60 mph are even possible closer to Lake Michigan. Precipitation will diminish in coverage and intensity Thursday night. Low temperatures tonight will ranage from 35 to 40. High temperatures on Thursday will be limited to the upper 30s to lower 40s. && .UPDATE... Issued at 749 PM EDT Wed Apr 5 2017 Any very low threat of severe weather is expected to diminish over the next few hours with lingering risk of any isolated hail through 11 pm primarily along and east of I-69 and along and south of Route 30. Weak elevated instability persists across northeast Indiana/northwest Ohio with potential of surface based storms likely remaining south/southeast of the area. Strongest cores over past hour have been situated at leading edge of drier mid level air punching in from the south, and this dry slot will overspread southeast portions of the area through the early portions of the overnight. Main threat over next 2 to 4 hours would be isolated hail for aforementioned locations due to elevated nature of storms and relatively wet bulb zero heights. Threat for storms will diminish after 04Z, although cannot completely rule out lingering isolated storm across far southeast as weak elevated instability axis begins to wrap back to the northwest across northwest Ohio. Concern for the overnight into Thursday will be on high winds/rain/flood potential/p-types. Deformation banding will tighten overnight with potential of changeover to rain/snow mix during the overnight hours. Big question will be evolution of near sfc wet bulbs which could be somewhat stubborn to drop overnight. Currently not planning any changes to previous forecast with mentions of less than one inch type accums across far northwest. Strength of fgen forcing and TROWAL enhancement overnight could yield period of more substantial precip rates that could be pose some limited impacts if near sfc wet bulbs can be overcome. Best co-location of forcing/instability for any mixed precip banding overnight appears to be across extreme northern Indiana/southwest-portions of south central lower Michigan, and somewhat limited elevated instability should favor of more dominant single banding. Given all above uncertainties, not much confidence in impacts when also considering warm ground temps as mentioned in previous forecast. Will not make any changes to going wind headlines at this time, although confidence in advisory level (near lake high wind warning) winds should increase toward daybreak across western locations. && .SHORT TERM...(This Evening through Thursday Night) Issued at 345 PM EDT Wed Apr 5 2017 Forecast panning out largely as expected. Rain will continue to increase in coverage and intensity through the evening and overnight as deepening upper low moves into the region. Secondary jet streak currently diving into the base of the trough, forcing a more negative tilt by tonight. Strengthening PV anomaly (below 500mb on 1.5 PVU surface) will make a bullseye for our area and coupled upper level jets will align more favorably for our area later this evening. Best 290-295K iSentropic ascent and midlevel deformation/fgen set up to our NW this morning and rain amounts thus far have not been particularly impressive (just a few tenths at most places). Better forcing will shift into our area this evening, along with slightly better elevated instability. Midlevel lapse rates still poor but enough for an efficient response to synoptic forcing. Heaviest rain may actually arrive later tonight as midlevel deformation is maximized just to NW of passing surface cyclone. Still expect storm total QPF near 2 inches across our NW half but flooding threat still appears mainly limited to low-lying/poor drainage areas and minor flooding on area rivers. Note: Several of the 12Z models (including NAM12 and earlier runs of HRRR and RAP) suffered initialization errors related to PW across the southeast but that does not seem to have a significant impact in our region. Model-based QPF largely matches expectations from a physical perspective and is in line with inherited forecast. Still think severe weather potential is very low this evening. Latest models are even further south with northward advancement of warm sector. Midlevel lapse rates are also quite paltry and struggling to get any meaningful MUCAPE into our CWA. Will still watch areas south of US-24 until 10pm for an isolated hail threat but even there the risk appears low. Focus of the event will then transition to snow and wind. Surface low will further deepen tomorrow with a tight gradient in place locally. Strongest winds will be in our northwest where both NAM and GFS show 925mb winds 55-60 kts. However, even outside of that corridor, latest models indicate at least 40 kts at 925mb. Forecast soundings also show a little better mixing potential with slightly colder and drier air in the lower levels. Given this, will go ahead and issue a wind advisory for the entire CWA. A bit more marginal in our SE but it will be close. Going with high wind warning for Berrien and LaPorte counties due to stronger flow aloft and reduced friction off the lake. Highest gusts will be right along the lakeshore. Given these winds and expectation for 12-18 ft waves, beach erosion and some lakeshore flooding/damage is likely. Have therefore upgraded lakeshore flood watch to a warning. Other main concern will be snow showers. Slightly cooler boundary layer temps have raised the chances for snow. Particularly concerned about the 06-12Z period in our NW CWA. Expect a healthy deformation band during this period. Surface wet bulb temps are very marginal but snow rates may be high enough for some brief accumulation on grassy surfaces. If rates are high enough, could see around an inch or two. However, road temps are running very warm and not expecting much impact to morning commute. During the day Thursday, expect April sun will severely limit accumulation even with overcast skies. Wet bulb temps hold in the low-mid 30s so there will be wet snow mixing in during heavier showers but will likely melt quickly. Deformation band weakens and shifts east by Thu night but continued cooling and loss of sun will lead to better chance for accumulation in places that still see precip. An inch or so possible along and east of I-69 but again, warm ground/pavement temps should limit impacts. Only concern will be reduced visibility in heavier snow showers given aforementioned winds but confidence in impact is too low to justify winter weather advisory vs. wind advisory. && .LONG TERM...(Friday through Wednesday) Issued at 345 PM EDT Wed Apr 5 2017 Precip exits by Friday morning and much quieter weather on tap for the weekend. High amplitude ridge will fold over the region with temps climbing back to around 70F by Sun in deep WSW flow/WAA. Next chance of rain and storms arrive late Monday. Quick-hitting nature of cold front will lead to much shorter duration and therefore less rain. && .AVIATION...(For the 00Z TAFS through 00Z Thursday Evening) Issued at 749 PM EDT Wed Apr 5 2017 Strong warm advection associated with maturing synoptic low level cyclonic circulation will continue to support rain and a few embedded thunderstorms the remainder of the evening. Best chance of thunder through 03Z appears to be just south of KFWA but will have to monitor trends for possible brief inclusion. Otherwise, expecting MVFR conditions to give way to IFR cigs overnight behind occluding low with potential of LIFR conditions at KSBN where heavier deformation forced precipitation band is expected to impact. As colder air is drawn southward tonight, concern still exists for precip to mix with or change to snow at times at KSBN after 08Z, although confidence in extent of any accumulations is on the low side and mainly on grassy areas. Winds to ramp up overnight into Thursday morning as deep low pressure begins to depart to the east with gusts to around 40 knots expected through the day Thursday. Cigs are expected to remain in the IFR/lower end MVFR range through much of this forecast period. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Wind Advisory from noon to 10 PM EDT Thursday for INZ006>009-017- 018-025>027-032>034. High Wind Warning from 4 AM to 7 PM CDT Thursday for INZ003. Wind Advisory from 5 AM EDT /4 AM CDT/ to 8 PM EDT /7 PM CDT/ Thursday for INZ004-005-012>016-020-022>024. MI...Wind Advisory from noon to 10 PM EDT Thursday for MIZ080-081. High Wind Warning from 5 AM to 8 PM EDT Thursday for MIZ077. Wind Advisory from 5 AM to 8 PM EDT Thursday for MIZ078-079. OH...Wind Advisory from noon to 10 PM EDT Thursday for OHZ001-002-004- 005-015-016-024-025. LM...Storm Warning from 5 AM to 8 PM EDT Thursday for LMZ043-046. Gale Warning until 5 AM EDT Thursday for LMZ043-046. Gale Warning from 8 PM Thursday to 5 PM EDT Friday for LMZ043- 046. && $$ UPDATE...Marsili SYNOPSIS...Marsili SHORT TERM...AGD LONG TERM...AGD AVIATION...Marsili Visit us at Follow us on Facebook...Twitter...and YouTube at:
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
651 PM CDT Wed Apr 5 2017 .SHORT TERM... 240 PM CDT Through Thursday... The main concern out the gate is increasing rain showers and some storms. We have had some snow mixing in with the rain across north central Illinois this afternoon. Expect some of that to ease as moderate precipitation subsides. Additional heavier showers this afternoon may still allow snow to mix in for these areas though no accums are expected. Expect a blossoming of showers through the afternoon and evening as several lobes of energy translate northeast ahead of the deep and impressive upper low to our southwest. Thunder should generally be confined along and south of I-80 as the instability this far north is much lower. Brief heavy downpours are expected to be the most significant hazard, with some small hail also possible. These showers will continue this evening, mixing with snow in some areas tonight into early Thursday. Localized flooding is possible due to the swollen ground, but the higher concern will be along streams and rivers which are already at high flow levels. Concern will then shift to increasing NE to eventually NNW winds tonight into Thursday. Here are some more specifics and impacts by weather type: Winds: Winds will be the highest concern from an areal coverage perspective, and this will also translate into a significant associated wave growth along the Illinois and Indiana shorelines. A center of low pressure near St. Louis will move into central Indiana by this evening and continue to deepen. North of the deepening low, the pressure gradient will undergo significant tightening, especially late tonight which is when the period of strongest winds will commence. Gusts over 50 mph for some areas, and even to 60 mph near the lake, and waves of 20 ft are very reasonable on Thursday with this setup. Expect winds to ramp up quickly this evening with the peak winds expected in the 4 am to early-mid afternoon time frame, and continuing into the early evening across northwest Indiana given the increased mixed layer depth. The timing and location of the wind advisories and high wind warnings attempt to match this evolution. Wind advisories will go into effect this evening for all our counties along the lake, and then overnight for Newton/Jasper/Benton. High wind warnings than take effect for Cook and Porter/Lake Indiana starting late tonight and continuing through the early-mid afternoon in Cook and through the early evening in Lake/Porter Indiana. Damage from possible fallen trees is a concern given the swollen ground and an extended period of strong sustained winds and locally damaging wind gusts. Wintry precipitation: Latest short term guidance suggests that we remain all rain outside of NC IL through most of the evening and even into the early morning hours for most areas. The area of concern for a burst of heavy snow continues to be east of I-57 across far east Central IL and more so across northwest Indiana. With the warmer conditions currently in place the dynamic cooling associated with heavier precipitation rates is what will be needed to bring the snow (which will be falling at a good clip a few thousand feet above the surface) all the way to the ground. RAP/HRRR forecast soundings still suggest that these processes will most likely setup across NW Indiana, where a burst of heavy snow may still occur. This would largely be on grassy surfaces given the warm pavement temperatures. If it falls at a good enough clip there could be slushy accums on roads too. Most areas in northeast IL will remain rain until late tonight or on Thursday morning when precipitation rates will weakening, so it does not appear to be a big deal outside of this heavier axis, but some snowflakes could certainly mix in tonight into early Thursday. Rain/flooding: As noted above, the ground is rather swollen, so any heavier precipitation rates will lead to ponding of water and a further aggravation of flooding concerns across elevated streams and rivers. An additional 1" of rain remains possible in the shower and isolated storm activity, with locally higher amounts. Precipitation will be much lighter on Thursday with the prime focus being the strong winds. KMD/Lenning && .LONG TERM... 240 PM CDT Thursday night through Wednesday... The surface low will pull away east of the area Thursday night, and while winds will ease, they will still remain elevated into Thursday as the surface low will strengthen further across the eastern Great lakes. Showers will linger Thursday night across northwest Indiana as we remain in cyclonic flow aloft, but moisture will diminish. Height rises Friday will lead to some warming and dry conditions. The surface ridge will shift east Saturday. Upper level ridging will build and southwest flow behind the high will usher in warmer conditions for the weekend. Expect some passing high clouds Saturday and Sunday ahead of another fast moving Pacific upper low. This low that will move from the four corners region early Sunday to the Great Lakes midweek. This will lead to shower and some t-storm chance later Sunday night with the leading shortwaves, and then ahead of this systems cold front sometime Monday or possibly into Tuesday, but there is some disagreement from the mid-range models on timing. Given that, the early to mid week period does favor a chance of showers and possibly some storms before the low pulls away. KMD && .AVIATION... For the 00Z TAFs... Windy conditions dominate throughout the forecast period while off and on rainfall will continue through the evening and most of the overnight hours. Widespread precipitation is in place across much of the midwest associated with an area of low pressure centered over southern Indiana. The back edge of the precipitation stretches west into Iowa and isn`t expected to clear the terminals until the predawn hours at RFD and late morning or early afternoon for the Chicago area terminals. The axis of heaviest rainfall is over Chicago currently reducing vsby to under two miles at times, but this is expected to shift east of the terminals around or shortly after 00Z with vsby improving to 4-7SM rest of the evening and overnight. Also expect ceilings to eventually improve from IFR to low MVFR at some point overnight. Winds remain the main concern for the forecast. Winds are already gusting in excess of 30 kts this evening out of the north. Winds this evening are generally 020-030 and will gradually back to 340- 350 overnight. At any point in the TAF period, there could be sporadic or infrequent gusts 5-10kt higher than indicated in the TAF. Leaned heavily on top of the channel winds from the RAP and LAV guidance for magnitude which have been verifying reasonably well over the past couple hours. Winds are expected to peak mid morning Thursday through mid afternoon with gusts into the high 30 low to 40 kt range, then should taper back down towards the low 30 kt range late afternoon into the evening. BMD && .MARINE... 240 PM CDT... Overall trends appear to be evolving mostly as expected, though winds have been a little slow to increase into the gale category this afternoon. A period of storm force winds still appears very likely starting late tonight and continuing into Thursday evening, though headlines were adjusted just a bit to end the storm warning a little earlier for the Illinois nearshore. Very high wave growth is expected to accompany these winds at the southern end of the long fetch. The two factors responsible for these strong winds are a deepening low moving across Illinois into central Indiana, and an area of high pressure approaching from the northern Plains. The period where both are strongest and in closest proximity, thus producing the tightest pressure gradient across the lake, would be late tonight into mid morning Thursday. After Thursday, quieter conditions prevail for Friday and Saturday as the high pressure moves over the lake itself. There could be another period of strong winds Sunday and Monday but not nearly what we are expecting for tonight and tomorrow, and the mild southerly air would not produce nearly the wave growth or deep mixing as the colder and more dense northerly flow. Lenning && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Wind Advisory...ILZ014 until 4 AM Thursday. High Wind Warning...ILZ014...4 AM Thursday to 4 PM Thursday. Lakeshore Flood Warning...ILZ014...4 AM Thursday to 1 AM Friday. Wind Advisory...ILZ006 until 4 PM Thursday. IN...High Wind Warning...INZ001-INZ002...4 AM Thursday to 7 PM Thursday. Lakeshore Flood Warning...INZ001-INZ002...4 AM Thursday to 1 AM Friday. Wind Advisory...INZ001-INZ002 until 4 AM Thursday. Wind Advisory...INZ010-INZ011-INZ019...4 AM Thursday to 7 PM Thursday. LM...Gale Warning...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777- LMZ779 until 4 AM Thursday. Storm Warning...LMZ740-LMZ741-LMZ742...4 AM Thursday to 4 PM Thursday. Gale Watch...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...7 PM Thursday to 3 PM Friday. Storm Warning...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...4 AM Thursday to 7 PM Thursday. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
928 PM CDT Wed Apr 5 2017 .UPDATE... Issued at 926 PM CDT Wed Apr 5 2017 Showers continue to wrap around the upper low that is lifting eastward into the Ohio Valley. Showers are now confined to far eastern Missouri and Illinois and will move out of the area from west to east during the overnight hours as the upper low continues to move east. Have got a few reports earlier of sleet and wet snow flakes mixed in with the rain which is is to be expected with these early spring upper lows, but latest RAP soundings still looks like overnight precipitation will be mainly rain. It is a windy night as the pressure gradient tightens in response to the surface low deepening as it moves northeast into the eastern Great Lakes overnight. Britt && .SHORT TERM... (Through Late Thursday Afternoon) Issued at 308 PM CDT Wed Apr 5 2017 The synoptic pattern early this afternoon features an impressive mid-latitude cyclone, with an upper-level low seen spinning across portions of southeast IA, and an associated surface low deepening as it moves across eastern MO and southern IL. This strong system will be the main focus of the short term period. The surface low pressure center currently lies somewhere to the northwest of the St. Louis metro area, likely between St. Louis and Hannibal, MO. This cyclone will continue to slowly meander to the east late this afternoon into this evening. To the east/southeast of the cyclone center, latest objective mesoanalysis data showed anywhere from 100-250 J/kg of MLCAPE. This has been enough to support widespread convective shower activity, with a few embedded thunderstorms as well. While convective coverage may still increase later this afternoon as we continue to warm a few degrees, overall I think instability will remain fairly meager, thus limiting the severe threat to areas further south and east. However, still can`t rule out a few storms capable of some small hail through the early evening though given fairly low wet bulb zero heights. Also, given the saturated grounds from the heavier rains last night, a few localized flooding issues will be possible through this evening as well, mainly across IL. The surface low pushes east this evening, allowing a cold front to sweep through the region. Behind this front, winds will really pick up as the pressure gradient tightens on the backside of the departing low center. Gusts of 30-40 mph will be likely, with a few gusts close to Wind Advisory criteria (45 mph) not completely out of the question. It seems the best places for these higher gusts will be across eastern MO into western IL. As the low pushes east, a weakening mid-level deformation band of precipitation on the backside will slide through. All precipitation will have pushed east of the region by Thursday morning. Thursday will be a fairly raw day compared to recent standards, with temperatures struggling in the 50s with breezy northwesterly winds continuing (gusts of 25-35 mph). KD .LONG TERM... (Thursday Night through Next Wednesday) Issued at 308 PM CDT Wed Apr 5 2017 Although the aforementioned low pressure system will have moved away from the area and will be located over the northeastern CONUS tomorrow night, it will continue to influence the upper air pattern across MO/IL as disturbances rotate around its western periphery and expand the coverage of cyclonic flow aloft. At the surface, a high pressure center will move southward from Canada, eventually reaching the shared borders between MO/AR/KS/OK by 12z Friday. Temperatures are expected to fall into the 30s late Thursday night/early Friday morning. Winds will be light but not calm, and transient clouds are expected within the cyclonic flow pattern aloft. Although patchy frost is possible, widespread frost is not expected at this time because the pattern is not favorable for radiational cooling. No precipitation is expected this weekend due to upper ridging, although a developing low pressure system over the northern plains and the resultant tightening pressure gradient may create breezy conditions at times. A disturbance will bring a chance of widespread precipitation to the area early next week, but there is poor agreement between the GFS and ECMWF regarding the location and speed of the shortwave. Kanofsky && .AVIATION... (For the 00z TAFs through 00z Thursday Evening) Issued at 711 PM CDT Wed Apr 5 2017 Scattered showers with low MVFR or IFR conditions are expected this evening. Then ceilings are expected to climb to VFR later this evening and overnight as an upper level storm system moves east of the area. North to northwest winds will remain gusty through the period. SPECIFICS FOR KSTL: Ceilings around 1000FT AGL are expected through mid evening before they slowly climb above 3000FT AGL after 09Z as an upper level storm system moves east of the area. North to northwest winds will gust to between 20-30kts through 00Z. Britt && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Melbourne FL
900 PM EDT Wed Apr 5 2017 .UPDATE... ...Continued Risk for fast-moving strong to severe storms late tonight/early Thursday... Few strong storms developed along boundary interactions early this evening prompted marine warnings. Several reports of winds over 34kts along central Brevard coastline with the highest of 47kts right at KCOF. Most activity has now moved offshore and weakened. Still some lingering showers over treasure coast, which should be mainly gone by zone update time. Temp fcst about on track, but values are holding up over the north where winds do not fall off much, and may need to bump them up. Short range guidance, HRRR model as well as local ARW continue to show timing to be on track for line of strong convection to approach northern areas late at night. Models consistent now for several runs with a window of 2 to 3 hours of heightened storm activity. Still expect far northern areas starting around 5 AM and into central areas between 6 and 7. Pre-frontal line of convection will not cross southern areas until early afternoon. Main threats continue for strong straight line winds under developing mainly unidirectional flow. Short range guidance depict backed near surface winds currently will veer overnight, with 40kt winds not far off the deck. Update SPC outlook now has SLGT RISK area postioned a bit farther south, now north of a line from near MLB to SW Osceola county. Prev Disc... Thursday...Threat for strong/isolated severe storms will end with passage of the convective band. As is typical, the dry air should over spread the area before the cold advection behind the front. This will produce very warm temperatures in the low to mid 80s in breezy westerly flow behind the front as skies clear. && .AVIATION... After earlier convection, VFR through most of night with VCTS late with a 2 hour TEMPO period of TS. Only minor adjustments to prev forecast. && .MARINE... Tonight/Thu...S/SW winds will increase tonight reaching 20-25 knots by morning. Will maintain the Advisory for Winds beginning across the northern waters this evening spreading south to include all the waters by sunrise. Seas will build to 4-5 feet. Isolated storms may push offshore this evening but a better chance for fast moving showers and embedded storms will occur toward sunrise through Thu morning ahead of a strong cold front. A brief period of 6 to 7 foot seas will occur Thu before winds veer West northwest and reduce seas esp nearshore due to limited fetch length. && .CLIMATE... Record highs were broken at all of our climate sites this afternoon (Daytona Beach, Orlando, Melbourne and Vero Beach). && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...Small Craft Advisory for winds from 8 AM Thursday to 4 AM EDT Saturday for Flagler Beach to Volusia-Brevard County Line 0- 20 nm-Sebastian Inlet to Jupiter Inlet 0-20 nm-Sebastian Inlet to Jupiter Inlet 20-60 nm-Volusia-Brevard County Line to Sebastian Inlet 0-20 nm. Small Craft Advisory for winds from 4 AM Thursday to 4 AM EDT Saturday for Volusia-Brevard County Line to Sebastian Inlet 20-60 nm. Small Craft Advisory for winds from midnight tonight to 4 AM EDT Saturday for Flagler Beach to Volusia-Brevard County Line 20-60 nm. && $$ Blottman/Sedlock
Area Forecast Discussion
National Weather Service Norman OK
918 PM CDT Wed Apr 5 2017 .UPDATE... The forecast tonight is in good shape. Only minor tweaks to hourly elements were made. && .DISCUSSION... Patchy frost is possible tonight into early Thursday morning in rural low lying locations mainly across western and northern Oklahoma. Clear skies, light winds, and dry air will allow for good radiational cooling tonight. Current forecast lows in the mid 30s to mid 40s appeared reasonable and were not adjusted. There will be a strong low level inversion developing where ridgetops will be several degrees warmer than valleys. Believe frost formation will be too patchy to justify a Frost Advisory tonight. The developing strong low level inversion as well as warm soil temperatures in the 50s to lower 60s may help to keep lows just above 36F in many locations, preventing frost formation. Products will be updated shortly. MBS && .PREV DISCUSSION... /issued 618 PM CDT Wed Apr 5 2017/ DISCUSSION... AVIATION... /For the 00z TAFs/ VFR conditions will prevail. Mixing will subside shortly and wind speeds will decrease considerably early this evening. Diurnally driven cumulus will diminish early this evening also. Light northwest winds will continue tonight, but could become northeasterly at northern TAF sites during the afternoon. Speeds are expected to remain below 12 knots. PREV DISCUSSION... /issued 449 PM CDT Wed Apr 5 2017/ UPDATE... Added isolated shower mention through early this evening for locations east of I-35. DISCUSSION... A few showers have formed near the Ponca City to Stillwater to Seminole areas in the past hour or so where SBCAPE values up to 300 J/kg are occurring according to latest RAP model analysis. A rumble or two of thunder could occur as well, but did not mention due to low confidence of occurrence. A small cell on the west side of Ponca City produced pea size hail in the last 15 minutes, which is not surprising with very low wet bulb zero heights 4000-5000 ft AGL. This activity should quickly dissipate 6-8 pm with the loss of daytime heating. Products have been updated. MBS PREV DISCUSSION... /issued 332 PM CDT Wed Apr 5 2017/ DISCUSSION... As the departing storm system moves farther away this evening, the pressure gradient will loosen fairly quickly. With the additional loss of daytime mixing, the winds will diminish quickly around sunset. Light winds, clear skies, and cool weather will probably result in scattered areas of frost by early Thursday. Since we expect only patches of light frost, with temperatures mainly at or above 35 degrees F, we have elected not to issue a Frost Advisory. The surface high will continue to shift southeast, causing our winds to switch back around to southerly, and somewhat warmer weather is expected Thursday and Friday. The weekend will be warmer yet, with some moisture return. By late Sunday afternoon, models suggest that we will have sufficient moisture and vertical wind shear to support rather severe thunderstorms. Given how deeply the current cool/dry airmass plunges into the Gulf of Mexico, the moisture return seems a little aggressive. However, it`s not out of the question, so Sunday is a day that will need to be watched closely for changes in severe weather potential. By Monday morning, there will probably be sufficient moisture ahead of a surface cold front (expected to be across east-central to south-central Oklahoma) for more substantial rain chances and rainfall amounts. The atmospheric flow looks favorable for training of showers/storms, so that time period shows some potential for heavy rainfall amounts. It is, however, still five days away, so much can still change that would affect that part of the forecast. It is unclear how far the early-week front will move, so the forecast for Tuesday and Wednesday is of the "low confidence" variety. Saturday will feature breezy, warm, and dry conditions in western Oklahoma and our westernmost counties in Texas. This may result in an elevated risk of wildfires, depending on the state of vegetation at any given location. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 39 68 43 71 / 0 0 0 0 Hobart OK 37 71 43 72 / 0 0 0 0 Wichita Falls TX 41 74 46 76 / 0 0 0 0 Gage OK 35 68 41 74 / 0 0 0 0 Ponca City OK 36 63 39 69 / 0 0 0 0 Durant OK 44 71 45 72 / 0 0 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ 17/12
Area Forecast Discussion
National Weather Service Charleston WV
1025 PM EDT Wed Apr 5 2017 .SYNOPSIS... Strong upper low/frontal system with a severe weather threat this evening and tonight over the western zones. Wrap around rain showers with mountain snow to end the work week. High pressure for the weekend. && .NEAR TERM /THROUGH THURSDAY/... As of 1020PM Wednesday...Updated PoP based on current Radar trends and mesomodel guidance through 08Z. Convection has weakened considerably. Winds could still be gusty, between 40 to 50 mph with the stronger segments. However, storms will continue to weaken as they push east. As of 745PM Wednesday...Forecast remains on track with main line of storms entering our region between 00Z and 01Z. Storms are weakening as it enters drier air, but with that said, we will likely have some issues due to strong winds with this line. As of 6PM Wednesday... Slightly tweaked PoP with the arrival of convection later tonight. The HRRR seams to have a fairly good handle on the current location and progression of the convection and it brings storms into the Ohio Valley just a tad faster than the previous forecast indicated. Have the line entering our border with ILN between 00Z and 01Z and then bring in Cat PoP by 02Z. This is about an hour or so faster than the previous forecast. There is still some concern for possible severe weather for our SE Ohio and KY Counties and we will just have to watch and see how the storms hold together over the next couple hours. Strong winds will be the main threat. As of 200 PM Wednesday... A lobe of warm, moist air nosing into central KY analyzed on mesoscale surface analysis will set the stage for a variety of significant and potentially severe weather this evening into the overnight hours. The greatest likelihood of severe remains toward the western portions of our CWA. As of 18z, a cumulus field has initiated across eastern Kentucky. Favorable wind profiles and high shear continue to support at least a chance of strong to severe thunderstorms - especially in the western half of the CWA. Damaging winds, tornadoes, and hail all continue to be threats. 600-800 J/kg of CAPE developing this afternoon and its concurrence with LL forcing this evening will dictate storm development. The main line of convection accompanying/slightly ahead of the cold front will enter our OH/KY areas between 00-02z this evening. The greatest threat for severe weather will be where instability and high shear intersect with frontal lift. One caveat to the severe potential would be a late frontal arrival with waning instability. Storms will weaken as the line pushes through the mountains around 09z tomorrow morning. During the mid-morning hours, a second area of storms along the front itself may form in the wake of the main line in central WV and has the potential for some gusty winds and graupel. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 315 PM Wednesday... Much cooler, and windy Thursday night into Friday, with upslope snow showers throughout the period. Still looking at light accumulations possible across the higher terrain counties, but concern still remains as to how much will actually accumulate versus melt due to recent warm temperatures. In addition, rather gusty winds will take hold across the area on Thursday night and Friday, with strong llj and tight pressure gradient across the region. May need a wind advisory across the higher terrain counties to account for this, or even a winter weather advisory to account for the snow showers with occasional low vsbys in wind. Will allow future shifts to handle this situation, as current severe weather threat more pressing at this moment. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 315 PM Wednesday... Drying trend takes hold over the weekend as high pressure surface and aloft builds into the region. Will see warming a warming trend as the weekend progresses. Another strong cold front looks to approach early next week, with cooler temperatures behind the front, and showers and thunderstorms. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... As of 750 PM Wednesday... Currently VFR, however a line of showers and thunderstorms has formed out ahead of an approaching cold front and this line will push through the region overnight. Have tried to time out the progression of the line the best as possible and bring IFR conditions into HTS/PKB/CRW based on current movement and speed. However, the convection will likely weaken and IFR conditions may not be met. Most confidence for IFR to occur in thunderstorms is at HTS at this time. For areas further east, not enough confidence to drop forecast to IFR conditions. Conditions will improve after the main line of storms passes with generally MVFR to VFR conditions overnight. Cold front and more showers and low clouds with MVFR conditions moves into the region tomorrow. Winds will become quite gusty with the front with 25 to 35 knots possible late in the TAF period. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z FRIDAY... FORECAST CONFIDENCE: Low to Medium. ALTERNATE SCENARIOS: Convection timing and conditions could vary. Winds tomorrow may be stronger than currently forecast. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE THU 04/06/17 UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11 EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07 CRW CONSISTENCY H H H H M L M L L M M M HTS CONSISTENCY H H M M M M M H H H H L BKW CONSISTENCY H H H H H M L M H H L M EKN CONSISTENCY H H H H H H M L L L M L PKB CONSISTENCY H H H M M M M M M M H M CKB CONSISTENCY H H H H H H L L L H H M AFTER 00Z FRIDAY... IFR possible in wrap around moisture late Thursday through Friday, especially in the mountains with snow Thursday night. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...JMV/JW/MC NEAR TERM...JW/MPK/MC SHORT TERM...SL LONG TERM...SL AVIATION...MPK
Area Forecast Discussion
National Weather Service San Diego CA
150 PM PDT Wed Apr 5 2017 .SYNOPSIS... High pressure aloft will drift east tonight and a Pacific trough will slowly move in from the northwest. Thursday will be another sunny, mild day with areas of morning clouds and fog near the coast. Cooler Friday with a chance for showers Friday night and Saturday with a passing cold front. Weak high pressure will return next week bringing fair and warmer weather. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... A shallow marine layer is in place at the coast today with haze and patchy clouds/fog at the beaches. The marine layer will deepen ever so slowly tonight as the ridge aloft drifts east, a scenario that can produce areas dense fog in a shallow marine layer. The HRRR model projects a few areas of vis less than 1/2 mile near the coast tonight, so there may be some vis restrictions along I-5 and some of the coastal communities tomorrow morning. Over the mountains, the offshore pressure gradients and low level 850 mb flow supported another day blustery east wind gusts of 20-30 mph in the San Diego and Riverside County mountains and passes. Thursday will be another nice day with mostly sunny skies. Increasing onshore flow will result in a few degrees of cooling west of the mountains, but the lower deserts will be a little warmer since the onshore flow won`t make it there until Friday. The disturbance poised to move into the area Friday night and Saturday has moved into the high resolution model window. The models continue to show the system weakening as it moves into a more stable atmosphere down here that is not entirely conducive to significant rains. There is general agreement with a trough sweeping across SoCal Friday night and Saturday, but most of it`s energy will pass by to the north. The 12Z WRFEMS shows a band of moisture with PWATS of 1.15" moving into SoCal, but the upper support is weak. Although there is little in the way of PVA or significant instability, showers are still likely along and ahead of the cold front. The rainfall outlook remains on the low end with 0.05-0.25" west of the mountains. Some areas may only see a passing light shower or a sprinkles, most likely in southern San Diego County. The greatest amounts of 0.25- 0.75" are likely on the west/southwest slopes of the mountains of SBD and RIV counties. Light snow is possible above 7500 feet. The trough will bring gusty onshore winds to the mountains and deserts Friday and Saturday with gusts of 45-55 mph. The trough passes Saturday with dry northwest flow/weak ridging aloft Sunday through Wednesday for seasonal weather through the middle of next week. && .AVIATION... 052015Z...Coast/Valleys...Mostly clear at this time. Low clouds likely to return to the coastal areas 03Z-06Z Thu, spreading up to 10 miles inland by 15Z Thu. Cloud bases likely to be below 1000 ft MSL, and could lift to around 1500 ft MSL by 15Z, although confidence is only moderate. Otherwise, SCT-BKN clouds at/above 20000 ft MSL through Thursday. Mountains/Deserts...SCT-BKN clouds at/above 20000 ft MSL with unrestricted vis will prevail through Thursday. && .MARINE... No hazardous marine weather is expected through Friday. A low pressure trough will bring scattered showers Friday night and Saturday. West-northwest winds gusting 20-30 kt will develop for Saturday afternoon through Sunday night and could be accompanied by combined seas to 10 feet in the outer waters, resulting in conditions hazardous to small craft. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ PUBLIC...Moede AVIATION/MARINE...PG