Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/19/17

Area Forecast Discussion
National Weather Service Taunton MA
1026 PM EDT Thu May 18 2017 .SYNOPSIS... After today`s record heat, we may see strong thunderstorms tonight, especially in western New England. A cold front pushing through the region Friday may trigger an isolated shower or storm, mainly south of the Mass Pike. High pressure moves over the region during the weekend bringing dry weather and more seasonable temperatures. A weather system from the Midwest sweeps east Monday with showers. Drier air moves in Tuesday. Another weather system will bring showers on Wednesday and Thursday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 1015 PM Update... Line of strong to severe thunderstorms progressing across central and northeast sections of southern New England. Surface temperatures were remaining in the low to mid 80s across much of eastern MA still at 10 PM, and mid level lapse rates across much of southern New England were running 6.5 to 7+ at 10 PM. Although the line has shown some fragmentation in the last 10 to 15 minutes, a risk for severe wind gusts still persists. The gust front with G30-35 KT has pushed ahead of the deep convection. Hence, we are considering Special Marine Warnings for the NE MA coast as far south as Boston Harbor. We anticipate the activity will begin to settle down by around midnight with a much lower risk of severe. May still have some persistent convection even into the early morning hours with some hint of an instability axis becoming established across CT. Will need to keep an eye on the area later. Have adjusted POPs in accordance with ongoing convection with HRRR guidance for next 3 to 6 hours. Have also made some minor adjustments in temperatures per current trends. 650 PM Update... * Few severe storms still possible tonight in western New England * Most of activity may stay to our north but not confident enough to remove threat in SNE Still seeing temps in 90s across much of SNE this evening after a record-setting day at BDL, BOS, PVD, and a tie at ORH (see below). Winds have become more SW and will begin to diminish around sunset. Our focus remains on the potential for severe storms tonight, especially in western New England. Activity has been focused along axis of higher K-index values from northern PA into central NY and northern New England. This will slowly shift toward our area tonight, as we are already seeing moisture increase on the latest precipitable water analysis. Dewpoints, which dropped into 40s and lower 50s due to mixing, will slowly increase as well. High-res models continue to insist that activity now along NY/PA border west of BGM will reach western New England around 10 pm, then weaken as it heads into eastern MA and RI closer to 2 am. Despite loss of daytime heating, it`s fairly cold aloft (-11C at 500 mb) to help sustain convection. Mid level lapse rates look favorable and 0-6km shear will be increasing over region this evening, so our thinking remains same - that is, we see lines or small clusters of storms tonight with wind damage being main threat. This does not look like a widespread event but one which features a number of strong storms (40 mph gusts) and perhaps a few severe storms capable of producing wind damage. The limiting factor is fact that best synoptic scale forcing associated with short wave seems to stay to our north across northern New England (where storms are lining up now). But we do have subtle height falls over southern New England which may be enough. Once any activity weakens overnight, expect clouds to linger with patchy fog near South Coast. Lows should only drop back into the 60s to around 70. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Cold front drops through region Fri. Enough lingering moisture, instability, and convergence ahead of it to possibly trigger a few showers or even a thunderstorm, especially south of Mass Pike from late morning into mid afternoon. Drier air arrives from NW during day, but many areas will still top out in 80s. Forecast soundings once again show deep mixing, so we should see 20-30 mph gusts at times Fri afternoon. Clear and cooler Fri night with lows falling back into 40s and lower 50s. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Big Picture... Longwave pattern is in transition next week with flow flattening to zonal. A trough then digs over the Eastern USA while a ridge builds along the West Coast. Shortwave scale shows Eastern high pressure in control over the weekend. Upper low pressure over the Southwest USA ejects across the plains to the Great Lakes by Monday, then crosses New England Monday night/Tuesday. Another upper low dives south from Canada and sweeps across New England Wednesday night/Thursday. Models are in fair agreement through Tuesday. Thereafter there are differences in handling of the late week system. Confidence is high for the weekend and early week. Confidence is moderate overall for the late week storm, but with low confidence on details of timing. Details... Saturday-Sunday... High pressure from Canada builds south over New England Saturday with a northwest flow aloft. The high then moves overhead Saturday night and Sunday. Expect dry weather through the weekend. Mid and high level moisture increase during Sunday suggesting increasing cirrus cover and possibly some mid level clouds. Mixing levels look to reach 850 mb. Temps at 850 will be 5-7C both days, which would support max temps in the mid 60s to low 70s. The easterly flow off the water may buffer temps in Eastern Mass, thus expect high 50s and 60s there Saturday, then temps a few degrees warmer Sunday as the flow shifts. Monday... Shortwave over the Great Lakes moves east, driving a cold front through NY/PA during the day and into Western New England during the evening. Increasing south-southwest flow during the early morning as a 40-knot low level jet shifts east. This increases by Monday evening to a 50-knot jet. This flow supplies plenty of moisture with PW values of 1.5 to 1.7 inches. Cross sections show a deep moisture layer most of the day. Sufficient confidence for chance pops after midnight early Monday and likely pops during the day Monday. Convective parameters are marginal at best, but enough chance to mention scattered or widely scattered storms. Cold front crosses the region Monday night between 00Z and 06Z. Drier air moves in during the overnight and should bring clearing skies. Tuesday... Upper shortwave crosses early Tuesday with cooling temps at 500 mb during the day. This should generate diurnal cumulus, but insufficient for showers. Mixing to 800 mb with temps 4-6C...that should support max temps in the 70s. Wednesday-Thursday... The next shortwave sweeps east from the Midwest Wednesday with increasing upper divergence/venting during the afternoon and night. Low confidence on timing of the onset, but expect a chance of showers starting either Wednesday afternoon or at night. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/... 03z TAF Update...Moderate confidence through 06Z due to convection and then high confidence thereafter. SW winds diminish this evening. VFR conditions should persist most areas with localized MVFR/IFR in scattered showers/tstms. The tstms should weaken as they reach RI and the eastern MA coast 04-06z. Main concern continues to be strong wind gusts (40kt) with the tstms, especially those moving across NE MA. Also expecting patchy fog near South Coast, Cape, and Islands with local MVFR/IFR visibilities, which rapidly improve after sunrise Fri. Winds shift to W and then NW during day Fri. VFR outside of isolated showers/storm mainly focused south of Mass Pike thru mid afternoon. VFR Fri night. KBOS TAF...High confidence, including timing of VCTS later tonight. KBDL TAF...High confidence, including timing of VCTS tonight. Outlook /Saturday through Tuesday/... Moderate confidence. Saturday-Sunday... VFR. Diminishing northeast gradient winds Saturday, becoming variable in the afternoon. Light wind Sunday with developing sea breezes along the coasts. Monday... General MVFR cigs/vsbys in rain and fog with areas of IFR possible. South-southwest winds with 2000-foot winds reaching 40-50 knots along the coastal plain...potential for low level wind shear. Tuesday... VFR with west winds gusting to 20 knots. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/... High confidence. SW winds diminish this evening. Seas build on outer waters S and E of Cape Cod where we will issue a Small Craft Advisory through Fri. Cold front drops south across waters Fri, and may trigger an isolated shower or storm through mid afternoon. More importantly, winds shift to W during the morning and then NW in the afternoon. May see brief 20-25kt gusts but not confident enough to expand SCA. Outlook /Saturday through Tuesday/... Moderate confidence. Saturday-Sunday... High pressure moves over the waters Saturday and off to the southeast Sunday. Expect northeast winds Saturday trending to light later in the day and then become southerly on Sunday. Seas less than 5 feet. No headlines expected. Sunday night-Monday... Weather system sweeps east from the Great Lakes. South-southwest winds will increase during Monday. Winds at 2000 feet will increase with speeds of 40-50 knots by afternoon. This may bring a period of 20-25 knot speeds by Monday afternoon. The steady southwest wind may bump seas to around 5 feet on the outer waters and exposed waters such as Rhode Island Sound. Visibility will be low at times in rain and fog. A cold front moves through Monday night, bringing a wind shift from the west and lighter wind. Tuesday... West-northwest winds will bring drier air. Expect speeds less than 20 knots, with seas less than 5 feet. && .CLIMATE... Records were broken in Boston, Providence, and Hartford today and tied at Worcester. Refer to the latest Record Event Reports which were issued earlier. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Air Quality Alert until 11 PM EDT this evening for CTZ002>004. MA...Air Quality Alert until 11 PM EDT this evening for MAZ004>007- 010>023-026. RI...Air Quality Alert until 11 PM EDT this evening for RIZ001>008. MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ235-254>256. && $$ SYNOPSIS...WTB/JWD NEAR TERM...JWD/Thompson SHORT TERM...JWD LONG TERM...WTB AVIATION...WTB/JWD/Thompson MARINE...WTB/JWD CLIMATE...
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1203 AM EDT Fri May 19 2017 .AVIATION... A well, organized trough axis is extending through southwestern Ontario into far southeastern Michigan as of 4Z. This surface feature is the delineator of the main surface cold front. Model data continues to advertise the surface cold front will push from north to south tonight, clearing the Michigan and Ohio stateline between 09-12Z this morning. Very strong signal exists for stratus development in the cold air advection. Satellite trends have been very bullish thus far, with extensive stratus/stratocumulus in place over central and northern Lower Michigan. Stratus will be slow to scatter out, possibly holding on as late as 20Z. //DTW THRESHOLD PROBABILITIES... * High for ceilings below 5kft late tonight through Friday morning. && .PREV DISCUSSION... Issued at 301 PM EDT Thu May 18 2017 DISCUSSION... Wind advisory continues through 8 PM. Center of upper level PV anomaly and surface low now due north of Lake Huron over Ontario late this afternoon. Excellent boundary layer mixing today has yielding wind gusts around 40 knots/45+ mph, along with lowering dew pts into the 50s, as dry mid level air is tapped. It remains highly doubtful any activity (outside of an isolated shower) will be touched off across southeast Michigan except right near the Michigan/Ohio border as the cold front tracks through early this evening. Even with lower dew pts, SBCAPES still around 1500 J/kg near the southern Michigan border, with visible satellite showing decent CU field over northeast Indiana, so a low chance of thunderstorms (slight chance severe) remains until the cold front pushes south of the state. The 12z HIRESW-ARW has come in dry, as well as the muted response and south of the border solution offered up by the 17z HRRR which seems reasonable. Good low level cold advection Tonight, helped out by northerly marine push off Lake Huron, as 925 mb temps lower to around zero over the northern thumb region by 12z Friday. This amount of cold air over the warmer nearshore waters/Saginaw Bay could possibly trigger a few sprinkles, but inversion heights are very low, and likely just looking at low stratus deck which will gradually mix out during the daytime hours. Significant north-south temp gradient advertised over southeast Michigan, with 925 mb temps around 10 C supporting lower 60s south of M-59 to lower 50s degrees across northern Thumb region. Large upper level low over Four Corners region/Central Rockies to lift northeast, with max 6 hr height fall center tracking through/near Minneapolis Saturday Evening. The question is how long will the large high over Ontario/Southern Quebec hold, before the moisture advection/transport overtakes the Central Great Lakes. It is possible showers and thunderstorms arrive during the day on Saturday, especially west of U.S. 23, but more than likely the bulk of the activity will hold off until Saturday night when the low level jet and triple point/occlusion lifts through the State. The area will remain in a large upper level trough through much of the extended forecast period. This brings continued chances of unsettled weather and cooler temps to the area. A cold front will push across on Sunday as the low moves towards the Hudson Bay. Rain is expected to diminish by Sunday evening as drier conditions move in. Cooler air filtering behind the front will keep temps on the cooler side with highs in the 60s for most of the week. MARINE... Southwest flow ahead of an approaching cold front will continue to provide strong gusts over the land through early evening. Gusts up to 35 knots will persist along the immediate shorelines, and also over Saginaw Bay where winds have been locally higher this afternoon due to funneling effects. Small Craft Advisories remain in effect for most nearshore waters, with the exception of Saginaw Bay where a Gale Warning continues until 800 PM. There is also a small chance for thunderstorms to develop in advance of the cold front through early evening, with best potential over Western Lake Erie. Winds will turn north as the front drops south through the region this evening and tonight. Winds will initially be gusty, especially over Lake Huron, then decrease in speed by early Friday morning. The long duration of north winds into Friday will allow wave heights to build in excess of 4 feet over southern Lake Huron. Hence, Small Craft Advisories for the Lake Huron nearshore waters will continue into Friday. HYDROLOGY... Isolated thunderstorms may develop late this afternoon/early this evening toward the Ohio Border. Storms will have the potential to produce brief periods of heavy rainfall if they do develop. The fast motion of the storms will limit rainfall, however, limiting totals to one- quarter of an inch or less. Low pressure lifting across the Upper Midwest will spread showers and thunderstorms into the area late Saturday through Sunday. Total rainfall looks to average in the 0.3 to 0.6 range, with higher totals expected in places where thunderstorms occur. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ421-422- 441>443. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....DRK DISCUSSION...SF/SS MARINE.......HLO HYDROLOGY....HLO You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Quad Cities IA IL
636 PM CDT Thu May 18 2017 ...AVIATION UPDATE... .SYNOPSIS... Issued at 255 PM CDT Thu May 18 2017 Cold front extended from lower MI to central IL and then to low pressure situated in the se corner of CO. Classic severe weather set-up in the Plains with a dry line in west TX with temperatures around 90 and dewpoints in the teens to the west, and readings near 90 with dewpoints near 70 east of the dry line. GOES-16 showed supercells rapidly developing west of Wichita Falls and Lawton moving northeast. In the meantime, a snowstorm was occurringin CO and WY. In the dvn cwa, northerly winds were bringing clouds and cooler temperatures to our northern cwa while it was milder in the south with a west wind, and plenty of sunshine. 2 pm temperatures ranged from 61 at Independence to 82 at Macomb. && .SHORT TERM...(This Evening through Friday) ISSUED AT 255 PM CDT Thu May 18 2017 Forecast focus on showers and thunderstorms returning. Numerous tornadic supercells will be firing across the central/southern Plains and into western MO through this evening. These will eventually congeal into clusters/lines and then spread towards the dvn cwa. The ESRL HRRR and NAMNEST indicate these storms to gradually weaken and stratify out as they get into our sw cwa well after midnight. However, an isolated elevated severe hailer (around 1 inch) is possible in our far south where SPC has a marginal risk. There is at least moderate shear but instability is minimal. These showers and embedded storms will then continue spreading northeast over the remainder of the cwa Friday morning. On Friday afternoon, any scattered showers and isolated storms should gradually diminish and many areas may end up dry, as the forcing weakens. Rainfall amounts averaging around 1/2 inch is expected. Lows tonight will range from the lower 40s along Highway 20 to the mid 50s in extreme northeast MO. Highs on Friday should range from the lower 50s along Highway 20 to the mid 60s in extreme northeast MO. .LONG TERM...(Friday Night through Thursday) ISSUED AT 255 PM CDT Thu May 18 2017 Complex long term scenario, with a slight chance of severe weather and decent rainfall early this weekend, along with a drop in temperatures expected by next week. Friday night into Saturday...Model consensus is in good agreement of showers and thunderstorms across the entire CWA beginning during the Friday night period. Modest instability and shear will also be present, which may help support hail in the stronger storms. Compared to previous runs, all models seem to be converging on the track of the surface low, with a general track from southern Iowa to northeast Iowa during the day. Handling of the warm sector, however, is still subpar likely due to forecast precipitation coverage. The GFS continues to favor a more northern intrusion of the warm sector into our southeastern counties, while others such as the Canadian keep it and associated precipitation south into central Illinois. The Storm Prediction Center has placed our counties along and east of the Mississippi in a marginal risk of severe weather at this time, and will therefore continue to monitor this low confidence situation. Saturday night through Monday afternoon...Showers and thunderstorms will exit the region Saturday night, giving way to a mix of clouds and sunshine for Sunday and much of Monday as high pressure builds across the central Great Plains and lower Mississippi Valley. Temperatures for Sunday will be below normal as cooler air advects behind the departing low, with highs expected to climb into the upper 60s. By Monday we will return to normal as highs climb into the lower 70s. Monday night on...Our next system will impact the CWA Monday night, with showers and thunderstorms expected through the day Tuesday. It`s too early to gage if severe weather will be possible, but at this time forecast instability is low across the region. Further out, most models suggest drier weather making its way into the region by Wednesday and continuing through at least Thursday evening. The GFS is the only outlier with an upper level shortwave moving into the area on Thursday. Look for temperatures to average below to near normal. && .AVIATION...(For the 00Z TAFS through 00Z Friday Evening) ISSUED AT 637 PM CDT Thu May 18 2017 A reinforcing cold front making its way southeast through eastern Iowa was providing a wind shift to more northerly surface winds and a trailing stratocu deck likely to remain just above MVFR thresholds this evening. Winds will veer to the northeast and strengthen overnight as a storm system strengthens in the plains. Elevated showers and thunderstorms are expected late tonight and early Friday morning, which will dissipate to showers by mid morning. This is expected to be followed by lowering ceilings and possible light fog as cooler air moves in from the east-northeast during the day. Will keep conditions MVFR for now, thinking the models may be too pessimistic with their widespread sub 1000 ft, IFR, ceilings over the region in the afternoon. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...Haase SHORT TERM...Haase LONG TERM...Speck AVIATION...Sheets
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
731 PM CDT Thu May 18 2017 .AVIATION... 00 UTC TAFs Concerns---Timing of convection and convective cessation. Any storms that occur at or near TAF sites will have the ability to produce frequent lightning, large hail and strong winds in excess of 30-40 knots. MVFR, possibly IFR ceilings may return tonight with additional chances for convection on Friday afternoon. Otherwise, breezy southerly non-thunderstorm winds will likely continue through the entire TAF period. For the DFW Metroplex TAFs---Convection has been slow to develop across North Texas this afternoon and evening mainly as a result of a stout capping inversion and the lack of large scale ascent. The latest 00 UTC FWD RAOB has indicated that capping has weakened and while this has occurred, large scale ascent has been lacking. As a corridor of better ascent slowly overspreads from the northwest and low level wind flow intensifies, it`s possible that this convection slowly moves towards the east. At this time, think that most operational guidance has been a little overdone in its QPF/simulated refelctivity output. That being said, the latest experimental HRRR and to some degree the latest TTU WRF appear to offer plausible solutions. Strengthening low level flow of around 40 knots around 925mb may fuel the ongoing complex of storms eastward towards the I-35 corridor through midnight. Right now, confidence is a tad on the low side and so for now, I`ll simply go with VCTS for a couple of hours between 0300-0500 UTC. If activity out to the west becomes a bit more robust, amendments to re-introduce TS may be necessary. With the increasing wind field through 0300 UTC coupled with subsidence beneath the anvil, the Metroplex terminals should respond and gust upwards into the 30 to 35 knots. Convective chances should subside through the overnight hours, but we will need to keep tabs on any complexes that attempt to develop to the west. MVFR stratus should flow northward towards Metroplex terminals around 09 UTC, as a strong low level jet persists. Some guidance hints at the potential for IFR ceilings, but the strong winds at and just above the surface should largely mitigate this threat. MVFR stratus below FL020 will likely continue through a majority of the day on Friday as the boundary layer remains moist. Breezy southerly winds with gusts up to near 25-30 knots will also be possible. There may be an outside chance for some showers just before midday, but confidence isn`t very high during this time. For now, will only introduce VCSH until 21 UTC, but we will monitor the potential for inclusion of TS in later issuances. For the Waco TAF site---Breezy southerly winds will continue at the Waco TAF site as the surface pressure gradient remains tight. Similar to the Metroplex, convective chances at Waco will hinge largely on the areal coverage of storms to the west. At this time, will keep VCTS for a few hours this evening and monitor trends. MVFR stratus should return just after midnight and continue through the afternoon. There`s a low threat for some IFR ceilings, but at this time, think that the breezy winds down near the surface may keep the duration very low. 24-Bain && .PREV DISCUSSION... /ISSUED 358 PM CDT Thu May 18 2017/ Afternoon visible satellite imagery shows an extensive cumulus field across North Texas with ongoing severe thunderstorms across western Oklahoma and far northwest Texas. There have been several convective attempts farther south across our western counties, but so far the cap has held. The cu field is showing some signs of becoming more vertical though and with stronger forcing for ascent still expected, we should see scattered severe thunderstorms develop through the early evening. Short term model guidance is still in fairly good agreement with scattered deep convection developing from near Wichita Falls as far south as Killeen. The atmosphere remains strongly unstable with surface based CAPE near 4000 J/kg. Very steep lapse rates and sufficient deep layer wind shear will support supercell storms capable of producing very large hail and damaging winds along with a few tornadoes. Organized clusters of thunderstorms should also develop mature cold pools given the amount of dry air aloft which would enhance the potential for damaging winds. Coverage of thunderstorms still remains the main uncertainty given the cap strength. Initial development across the western counties should be scattered (30-40%) and could occur on any one of a number of localized areas of convergence. One of these extends south of the ongoing supercell thunderstorms west of Wichita Falls. Thunderstorms may tend to increase in coverage as they move east later this evening as the cap continues to erode. After dark, the main area of forcing will begin to shift off to the northeast and areas along and north of I-20 may have the better chance for continued thunderstorms. Long story short, there is the potential for significant severe weather across parts of North Texas, but not all areas are expected to be impacted. Convection should weaken during the overnight hours, although the front/dryline will remain across southwest Texas. Another strong vort max will rotate around the main upper low over New Mexico. This stronger forcing for ascent should help ignite a new round of showers and thunderstorms, most of which will remain to the west of the area. This convection will weaken during the early morning hours on Friday. By Friday afternoon, we should remain fairly unstable and a new round of convection is expected to develop along the front/dryline to the northwest of the area. The potential will remain for severe weather during this time. As the main upper low finally ejects out into the Plains, a cold front will slide southward and rain/storm chances will increase across all of North Texas Friday night into Saturday morning. There will be a threat for severe weather during this time, with damaging winds being the main threat. In addition, there could be some locally heavy rainfall. The cold front should be south of the area on Saturday, although rain and thunderstorm chances will continue, especially south of I-20. We`ll maintain rather high PoPs south of I-20 through the day Saturday with things tapering off by Sunday. The weather pattern will remain active through next week with additional thunderstorm chances Monday through Tuesday night. Dunn && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 73 87 70 80 62 / 60 20 80 40 30 Waco 74 88 72 83 63 / 30 20 50 60 60 Paris 70 82 69 78 59 / 40 10 60 50 30 Denton 72 83 67 78 58 / 60 20 80 40 20 McKinney 71 84 69 79 60 / 50 20 80 40 30 Dallas 74 87 72 81 64 / 50 20 80 50 40 Terrell 73 87 71 81 62 / 30 10 60 50 40 Corsicana 74 89 72 83 64 / 20 10 40 60 60 Temple 74 87 72 84 64 / 30 20 40 60 60 Mineral Wells 70 84 65 77 58 / 60 30 80 40 20 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 24/24
Area Forecast Discussion
National Weather Service Lincoln IL
907 PM CDT Thu May 18 2017 .UPDATE... Issued at 905 PM CDT Thu May 18 2017 A couple of narrow bands of convection have lingered in far eastern Illinois this evening, in the vicinity of a stalled frontal boundary. There has been a general weakening trend over the last couple of hours. Those storms should dissipate over the next hour or so, with dry conditions for several hours and possibly much of the rest of the night. The HRRR is indicating some redevelopment near the front by 09z, mainly between I-70 and I-72. A stronger wave of storms is projected to arrive from the west toward 12z, with a few of those storms possibly strong to severe. Bulk shear and low level helicity north of the warm front appear sufficient for a few strong updrafts, with some strong downburst winds possible as the line advances to the ENE after sunrise tomorrow morning. Have adjusted the PoP, Weather and Sky grids down in coverage over the next 3-5 hours, with gradual increasing PoPs from west to east late tonight. A wide range of temps will exist across central Illinois for low temps, due to the presence of the front. Lows will remain in the low to mid 60s south of the front, with low 50s from Galesburg to Lacon and mid-upper 50s in between. Updated forecast info is already available. && .SHORT TERM...(This evening through Friday) ISSUED AT 300 PM CDT Thu May 18 2017 Showers and a few storms beginning to increase again across the Ohio Valley this afternoon, back into southeast Missouri. Most of the forecast area only seeing scattered clouds at the moment, with a cold front edging into the northwest part of the CWA. Temperatures have reached the mid-upper 80s over a good part of the CWA except northwest of the Illinois River near the front, where Galesburg was still holding in the upper 70s. The front will be settling to around the I-72 corridor by mid to late evening and I-70 overnight, with little movement due to the near parallel flow aloft. Most of the short-range models maintain some isolated showers or storms south of it through the evening. The main threat of rain will be spreading in from the southwest later in the night, as the large upper low over Utah and Colorado digs southward and sends energy northeast out of the Texas panhandle. .LONG TERM...(Friday night through Thursday) ISSUED AT 300 PM CDT Thu May 18 2017 The front doesn`t make a lot of northward progress during the day on Friday, but will surge northward Friday night as a shortwave continues to push northeast. A rather large temperature gradient can be expected, with highs ranging from the 60s from Havana- Bloomington northward to around 80 degrees south of I-70. Plenty of CAPE will be available south of the front, generally at least 2000 J/kg with even higher numbers indicated by the NAM, although this will not be in an area of favorable shear. This should be enough for some strong to severe storms, primarily over areas from about I-72 southward. Some tapering of the rain is expected during the evening, before another widespread rainfall accompanies the approach of the surface low as the upper system moves into the Plains. This will usher in an extended period of precipitable water values of around 1.5 inches, which will persist until the low lifts northwest of Illinois Saturday evening. A fairly widespread 1-2 inches of rain appears likely over the forecast area, with some heavier amounts in the stronger storms. Once this system exits early Sunday, an extended period of cooler conditions is expected for the upcoming week. As the upper low moves north of the Great Lakes, a lobe of energy will drop southward and form a deep trough over the Plains, slowly pushing eastward across the Mississippi valley in the Tuesday night to Wednesday time frame. Some model differences in the longer range with this feature, with the ECMWF slower and further south as an upper low cuts off. However, the precipitation that occurs should mainly be periodic showers, with thunder chances fairly small. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 703 PM CDT Thu May 18 2017 Ongoing convection associated with a stalled frontal boundary are expected to remain clear of the TAF sites for much of the first 12 hours of this TAF period. A wave of storms is projected to arrive near PIA and SPI between 11z-13z. The line of storms will progress eastward across the area tomorrow morning, but with scattered storms possible through mid-day. There should be a break in the rain/storms for at least the first half of the afternoon, before another line of storms progresses eastward across central IL starting near the end of this TAF period. Forecast soundings are showing a stratus deck developing after the line of storms moves through tomorrow morning, with low MVFR and IFR conditions expected. Conditions should improve to MVFR tomorrow afternoon, with VFR conditions possible at times. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Shimon SHORT TERM...Geelhart LONG TERM...Geelhart AVIATION...Shimon
Area Forecast Discussion
National Weather Service Indianapolis IN
1157 PM EDT Thu May 18 2017 .UPDATE... The AVIATION Section has been updated below. && .SYNOPSIS... Issued at 240 PM EDT Thu May 18 2017 A frontal system will interact with instability and increasing moisture and result in showers and thunderstorm chances through Sunday. The best chances will be Saturday night and Sunday, when a cold front will be moving across central Indiana from west to east. High pressure will bring dry weather to the area by Sunday night, but then there will be more thunderstorm chances starting overnight Monday night as an upper system tracks southeast towards the lower Great Lakes and Ohio Valley. Above normal temperatures will persist through the weekend with cooler temperatures in store next week. && .NEAR TERM /Overnight/... Issued at 947 PM EDT Thu May 18 2017 Radar shows Thunderstorms slowly weakening across the two boundaries in central Indiana. The storms across the southern parts of the forecast area have almost dissipated completely...while the northern line continues to slowly wane and move east. Expect this trend to continue as daytime heating continues to be lost and storms continue to slide east along the boundary to the north. For now GOESR show nearly steady state cloudy top temps...but for now not expecting this trend to continue with loss of instability. THus will trend pops lower and progress storms east-southeast over the next few hours. The surface boundary is expected to sink farther south across Central Indiana...and as dynamics approach the area toward daybreak...the HRRR suggests new development along and near the boundary. Thus will return to ramping pops upward after 09Z. Used a blend on Temps...and feel that cooling on the northside of the boundary may be overdone. Points on the warm side of the front should see lows close to persistence. && .SHORT TERM.../Friday through Sunday/ Issued at 240 PM EDT Thu May 18 2017 The main focus for the short term will be on timing and coverage of showers and thunderstorms through Sunday. Models general agree on synoptic pattern and features. So, will accept the blend. An upper low over southern Colorado and northern New Mexico Friday morning will makes it way north and northeastward to northern Minnesota on Sunday as a ridge builds over the eastern states. Meanwhile, a cold front will start off over southern Indiana on Friday but should return north as a warm front Friday night and Saturday. Finally, a cold front will sweep through the area overnight Saturday night into Sunday. Models have an upper wave ejected from the upper low move through the area Friday afternoon from southwest to northeast. Thus, after small morning pops along and south of the front, will keep the good chance afternoon pops from the blend. As the upper waves moves northeast of the area and sun sets, should see a lull in convection Friday evening. However, the upper ridge will move into eastern Indiana and western Ohio Friday overnight and into Saturday and a modest low level jet will set up over west central Indiana. This warrants higher pops overnight Friday night into Saturday. The best combination of moisture and forcing will be Saturday night and Sunday morning as the cold front moves in from the west. In addition, upper jet dynamics will become a factor as the area will be in the right rear quadrant of a 90 plus know 250 millibar jet. The activity will then be ending from west to east behind the front Sunday afternoon. With the front moving through, temperatures should only reach normal highs in the lower and mid 70s per the blend. Prior to that, With the cold front moving through tonight expected to stall over south central Indiana, looks like there will be a decent temperature gradient on Friday, with near normal highs in the lower 70s north of the front and above normal highs in the upper 70s to around 80 south of the front. With the front to the north, prefer above normal highs in the upper 70s and lower 80s. Plenty of instability for thunderstorms through the short term per all the models. Also, Marginal Risks for severe storms from the Storm Prediction Center look reasonable through Day3. && .LONG TERM (Sunday night through Thursday)... Issued at 153 PM EDT Thu May 18 2017 The initialization from Region will be used with rather high confidence. The deterministic models have differences, but arrive at similar temperature and precipitation predictions. This builds confidence in today`s forecast since no matter which model is right, the end result should be about the same. Possible temperature errors are 1-3 degrees, and possible POP errors around 10 percent. && .AVIATION /Discussion for the 190600Z TAFs/... Issued at 1159 PM EDT Thu May 18 2017 VFR Conditions will continue through the overnight. Isolated showers/storms continue to dissipate and weaken as the frontal boundary sags southward across the forecast area. May include a brief mention of VCTS at some of the taf sites based upon radar trends near issuance time to account for this. A decreasing trend is still expected. Some MVFR Conditions are possible on Friday by mid morning as a short wave is expected to push across Central Indiana. Models suggest favorable forcing for precip and MVFR CIGS are expected as the forcing passes and the surface boundaries remain in the area. Time heights show plentiful lower level moisture available. Thus have included a prevailing precipitation event. As forcing departs after 00Z Saturday...a return to VFR conditions is expected. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MK NEAR TERM...Puma SHORT TERM...MK LONG TERM....JK AVIATION...JP
Area Forecast Discussion
National Weather Service Jackson MS
942 PM CDT Thu May 18 2017 .UPDATE... Updated for evening discussion. && .DISCUSSION... The showers and thunderstorms that moved through early this evening have dissipated across our region, and conditions are expected to stay dry overnight. However, with still an abundant amount of moisture left in the atmosphere, some patchy fog can`t be ruled out before first light. Spots east of I-55 will be the main area for developing fog, which shouldn`t come as no surprise since this was the main sector that had isolated showers/storms earlier when that tongue of moisture seeped in from the Gulf. Friday will have another build up of showers and thunderstorms as the day progresses, but unlike today the Delta will not be immune to staying dry. A shift of higher values of preciptable water in the HRRR suggests values above 1.50 inches in the Delta and SE Mississippi. Expect these two regions to be the areas to watch on radar Friday afternoon as isolated pop-up storms come in from the south. /12/ Prior discussion below: Tonight through Friday, A warmer than normal and moist weather pattern will persist over the ArkLaMiss tonight through Friday as a mid level ridge center remains anchored near the southern Atlantic Coast region. The resulting southerly flow will continue to send copious amounts of low level moisture into the forecast area making for rather humid conditions and considerable late night and morning low clouds, including a chance for fog mainly in the Pine Belt region where winds will be lighter. As was the case today, diurnal convective precipitation will develop Friday given plenty of instability and sufficient deep layer moisture, but relative warmth in the mid levels of the atmosphere associated with ridge should help to limit thunder potential. Overall, the potential for any strong to severe storms is very low through tomorrow. High temperatures will once again approach 90 F over much of the area. /EC/ Friday night through Wednesday: On Friday night an active pattern will continue through the Plains as we will be wedged from strong ridging centered over the Southeast Atlantic coast. Rain chances will continue as we push into the weekend. As we move into Saturday instability will be increasing during the day as a wave pushes into the region from the plains. We will be looking at vertical totals in the upper 20s, lapse rate around 7c, ML Capes of 2000 Plus, and some deep layer shear of 20 to 40 knots. The flow will be on the weak side in general according to model soundings. So with this in mind will follow SPC`s marginal risk across the west half with the risk of damaging winds, and some hail up to quarter size. Rain chances will be on the likely side through the weekend. The front is expected to come through on Sunday into Sunday night. There could also be some possible strong storms with the frontal passage, which will bear watching on Sunday into Sunday night. The Euro and its ensembles seem to hang to front up during this period, while the GFS and Canadian as well as their ensembles seem to be more progressive as the upper trough energy lifts into the Upper Mississippi Valley then the Great Lakes by early next week. As we move into early next week we will have a zonal flow and will go to a more diurnal convective pattern. Meanwhile another upper trough will be rotating around the Mid Mississippi Valley to the southern plains which will send a front toward the region. The upper trough axis will rotate into the Mississippi Valley which will push another front into the region for midweek. This system will send a 140 knot jet across north Mississippi. This system may trigger some severe storms and will bear watching with deep layer shear of 40 to 50 knots. The Euro was farther south with the Closed Low./17/ && .AVIATION... 00Z TAF discussion: Convection continues to wind down with lingering storms closest to the GTR vicinity. VFR conditions will prevail until midnight with MVFR/IFR ceilings moving in from the south after midnight. These ceilings will begin rising after sunrise and be VFR by 19/18Z. Convection will be somewhat less on Friday compared to today and mainly confined to the GLH vicinity./26/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 71 89 70 87 / 9 24 8 58 Meridian 68 89 69 88 / 6 18 7 55 Vicksburg 71 89 72 89 / 11 30 9 55 Hattiesburg 69 88 68 87 / 9 26 7 59 Natchez 71 88 71 88 / 11 32 10 59 Greenville 72 88 72 87 / 3 33 10 48 Greenwood 72 88 71 87 / 4 22 9 51 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ 12
National Weather Service Jackson KY
854 PM EDT Thu May 18 2017 .UPDATE... Issued at 854 PM EDT THU MAY 18 2017 The remainder of the evening looks to remain dry, before showers and thunderstorms increase in coverage tonight ahead of a shortwave impulse across lower Tennessee/northern Alabama. Deeper moistening late tonight and Friday morning further support development, although wind fields will remain rather lackluster. Will also have to monitor the potential for fog through early tonight, given crossover temperatures mainly in the mid-upper 60s, before precipitation produces enough mixing to erode this concern. && .SHORT TERM...(This evening through Friday night) Issued at 331 PM EDT THU MAY 18 2017 Convection has increased in coverage in the southern part of the forecast area over the past hour, and is greater in coverage than originally expected. Showers and thunderstorms continue to move northeast. With that in mind have increased thunderstorm coverage from isolated to scattered over the southeast part of the forecast area for the remainder of the afternoon and into the early evening, while continuing with the isolated coverage in the northwest. With the loss of daytime heating the convection should quickly die off this evening. However, while there is considerable model disagreement on redevelopment later tonight some of the latest short range guidance including the HRRR is pointing towards redevelopment in the southeast late tonight and towards dawn. This seems to be related to a subtle short wave trough that will move northeast towards the area late tonight. With this in mind have decided to go with chance probability area wide late tonight, with best chances in the southeast. There is still considerable model disagreement with the extent of convective development on Friday, though it looks like coverage should once again be scattered, but with more of the area affected than this afternoon. Will continue with generally high chance probabilties for showers and thunderstorms area wide on Friday. With more clouds and precipitation tonight through Friday night there will be less of a diurnal temperature range with highs on Friday a little lower than today. .LONG TERM...(Saturday through Thursday) Issued at 354 PM EDT THU MAY 18 2017 A longwave trough pattern will be centered around two upper level lows as they move across the Northern Plains to start out the period at 12Z Saturday. This pair of lows will combine into one system, continuing its slow track to the northeast over the next couple of days, reaching Minnesota by Sunday morning and Ontario by Monday morning. This will push the longwave trough and lowering heights eastward as well, impacting the Ohio Valley through the weekend. The axis of this trough should pass across Kentucky Monday morning as it deamplifies considerably. Models remain in fairly good agreement during the day Monday and into Tuesday, developing another shortwave that will drop south across the Northern Plains and Upper Mississippi Valley during this time, then swing eastward towards the Ohio Valley Tuesday night. Timing starts to diverge at this point as both the GFS and ECMWF push this system across our region to end out the forecast period. This will have an effect on when at to what extent precip associated with this system impacts the region, so relied on model blends to round out this portion of the forecast. At the surface, a low pressure feature will be in place, shifting northeast across the Central Plains and into the Mid/Upper Mississippi Valley during the day Saturday. It will slowly track northeast, reaching the Upper Great Lakes by Sunday morning, and then into Ontario by Monday morning. A cold front will extend southward from this low pressure center, sweeping eastward across the Mississippi Valley Saturday night, then into the western Ohio Valley during the day Sunday. The front is expected to pass eastward across our CWA Sunday night, consistent with previous runs over the last day or two, so confidence in timing is pretty high. That being said, the low will be pulling so far north at this point, the frontal boundary will begin to shear out a bit as it passes over the region, so won`t be quite as strong. The frontal passage will quickly pass off to our east during the day Monday, with high pressure expected to move in across the region through the day Tuesday. The secondary shortwave that develops late in the period will also translate to another surface low developing to our northeast, and ultimately a secondary frontal system that will move across the region Tuesday night into Wednesday. As for sensible weather, a warm front will be located just along and to our north during the day Saturday, with warm moist unstable flow into the region, producing scattered showers and thunderstorms throughout the day and boosting temps back into the mid 80s. The loss of heating overnight will allow many of these showers and thunderstorms to dissipate briefly. However, the incoming cold front will create enough lift to produce more scattered convection moving eastward across the CWA late Sunday night. These showers and thunderstorms will increase in coverage throughout the day Sunday as the cold front continues to near. Still not expecting a whole lot in the way of severe weather with this, though given the super saturated nature of the soundings from the surface all the way through the atmosphere, would be more concerned for heavy rainers and excessive lightning. Once the front passes over Sunday evening/night, llvl winds will make a sharp turn to the NE and temperatures will quickly drop, with substantial dry air moving in a few hours later. This will effectively cut off convective activity and precip all together, so did not include mention of thunder after 12Z Monday. Highs on Sunday will be in the mid and upper 70s based on clouds and rain, but post frontal highs will struggle to reach 70 degrees in some locations by Monday afternoon. Another incoming cold front for Tuesday night will help boost southerly flow and temps during the day Tuesday, but will also lead to another round of showers and potential thunderstorms Tuesday afternoon/Tuesday night. The frontal passage Tuesday night will bring an end to the convection once again, as well as allow for the return of a cooler airmass to round out the forecast period. Highs Wednesday and Thursday will only be in the upper 60s. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) ISSUED AT 854 PM EDT THU MAY 18 2017 Mainly VFR conditions to prevail through Friday afternoon, although shower and thunderstorm coverage will likely be greater beginning tonight into early Friday. Have thus inserted VCTS for all sites from tonight through Friday morning. SYM probably will not see much activity until after daybreak Friday. Held off on prevailing thunder mention at any given terminal based on the pulse nature of these storms and thus their quick-lived nature. May very well see a period of sub-VFR ceilings or visibilities underneath any shower or storm, but this probability also remains too low at this time to include mention. Will monitor the potential for any fog development through this evening and early tonight before incoming precipitation produces enough mixing to erode this threat. Showers and thunderstorms will also be possible later on Friday, but timing/placement remain uncertain depending on how the morning`s activity plays out. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GUSEMAN SHORT TERM...SBH LONG TERM...JMW AVIATION...GUSEMAN
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
920 PM CDT Thu May 18 2017 .UPDATE... Issued at 918 PM CDT Thu May 18 2017 We continue to track convective evolution out to the west this evening. A broken line of thunderstorms exists over eastern KS/eastern OK from earlier convection across the central and southern Plains. A few supercells also have developed ahead of this broken line, mainly north of a surface warm front near the Kansas City metro area. Convective evolution remains a bit uncertain overnight, as many of the CAMs had suggested an organized cold pool would have developed by now. While there have certainly been some bowing structures at times, it appears convection remains fairly disorganized at this time. Nonetheless, an increase in a nocturnal low-level jet is likely underway and should lead to continued thunderstorm development/sustenance over portions of eastern KS and into western MO. While forecast soundings suggest increasing nocturnal, surfaced-based CIN with time over central and eastern MO, think if storms are able to develop a cold pool we may still see some strong/locally damaging wind gusts along with some locally severe hail as the convection moves into central/eastern MO. Have updated the forecast to reflect these latest trends. KD && .SHORT TERM... (Through Late Friday Afternoon) Issued at 333 PM CDT Thu May 18 2017 Main concerns through tomorrow will be the potential for severe thunderstorms. Cold front has become quasi-stationary from near Kansas City to Quincy to Chicago. To the south, there have been a few showers and thunderstorms that have developed across southeast Missouri. There is still potential for thunderstorms to develop farther north near I- 70 late this afternoon into the early evening hours according to the latest runs of the CAMS. This falls in line with the RAP which shows some weak surface moisture convergence south of the front in the 2000-3000 J/kg MLCAPEs. There may be a few storms continue to develop along the front into the early evening hours. Focus for storms will increase later this evening and overnight farther west where severe thunderstorms that are expected to develop over the Central Plains will grow upscale into an MCS per the latest runs of the HRRR and move east across the CWA between 08-14Z. There will be the possibility for a few strong to severe thunderstorms during this time with some large hail and damaging winds. This complex will lift to the northeast by mid morning allowing for dry time from mid morning until early afternoon. If the atmosphere can recover from the morning convection, then a few severe thunderstorms will be possible in the afternoon given MLCAPES between 1500-2000 J/kg and deep layer shear values 40+kts along and south of the warm front. Main focus for severe storms in the afternoon would be along the warm front. Britt .LONG TERM... (Friday Night through Next Thursday) Issued at 333 PM CDT Thu May 18 2017 (Friday Night - Saturday Night) Best chance of convection early in the period will be along/north of the slowly retreating warm front. Some disagreement on how widespread this activity will be with CAMs suggesting isolated- scattered activity while global models seem a bit more bullish. Regardless, favorable environment will exist for strong to severe thunderstorms capable of producing large hail and damaging winds, with a tornado threat for any storms that can travel along the warm front. Another round of storms then looks to move in from western Missouri overnight Friday night. Straight-line winds look like the primary threat with convection expected to be more linear by the time it reaches our CWA. Could Some signs the quasi-linear convective system will weaken as it heads toward the Mississippi River toward daybreak as low-level moisture convergence and instability slowly abates. Will have to also monitor the potential for flash flooding with this round of activity. Thankfully, the ground has gotten a good week to dry out so flash flood guidance is fairly high. Concern would be for any areas that get hit fairly hard tonight through Friday afternoon and then get hit again Friday night. Will continue to monitor this potential, but for now will hold off on a flash flood watch and see how the next ~24 hours evolves. Uncertainty increases on Saturday with respect to convective trends. There will likely be some ongoing convection on Saturday morning as alluded to above. How the morning convection evolves will be important regarding afternoon destabilization and severe potential. Does look like more of a marginal setup however with quite a bit uncertainty with the amount of destabilization. Higher chance for strong/severe storms at the moment look east of the Mississippi River where higher instability will likely reside. Do expect at least another round of showers and storms regardless of severity to form along/ahead of the cold front which will sweep through the bi- state area. (Sunday - Next Thursday) Well-below normal temperatures continue to increase in likelihood in the extended with a deep upper-level trough carving out across the eastern two-thirds of the CONUS. Highs generally will range from the mid 60s to low 70s each day with lows as cool as the mid to upper 40s. Best chance of rain, with a few thunderstorms possible, continues to look like the Monday night through Tuesday timeframe coincident with a closed midlevel circulation moving southeastward into the mid-upper Mississippi Valley and eventually the Ohio Valley. Gosselin && .AVIATION... (For the 00z TAFs through 00z Friday Evening) Issued at 636 PM CDT Thu May 18 2017 Main TAF concern will be convective trends overnight into Friday. While a few storms continue to linger over eastern MO early this evening, think we will see a general lull in thunderstorms from this evening into the early overnight hours. However, a line of showers/storms should approach COU/UIN after 07Z, spreading into the St. Louis metro sites after 08-09Z. These storms will bring lowered vsbys in heavy rain along with locally gusty winds. Showers and a few thunderstorms will likely persist into the day on Friday, but confidence is fairly low on timing/coverage. Outside of any showers/storms on Friday, UIN will reside on the cool side of a warm front which will allow for some MVFR cigs to work in from the north. SPECIFICS FOR KSTL: Main TAF concern will be convection early Friday morning. Think convection may begin to develop near the terminal as early as 7-8Z, but think a more concentrated line of showers/storms is likely to move through between 10-14Z Friday morning. Any storm will likely bring vsbys into the MVFR/IFR range. After the round of convection Friday morning, confidence decreases in convective coverage for Friday afternoon/evening. For now, will keep VCTS out of the forecast for the afternoon until trends are better ascertained. KD && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Midland/Odessa TX
928 PM CDT Thu May 18 2017 .DISCUSSION... Latest sfc analysis shows the dryline slowly retreating up thru the lwr Trans Pecos, w/convection trying to develop along this feature east of the area. However, hi-res models continuing to show convection developing in the Permian Basin after 06Z. We`ve let the RFW and HWW expire, and will do a quick update to remove them from grids and products. We`ll also adjust other parameters as necessary based on latest obs and forecast data. Updates out shortly. && .PREV DISCUSSION... /issued 617 PM CDT Thu May 18 2017/ DISCUSSION... See 00z aviation discussion below. AVIATION... VFR conditions are expected for the next 24 hours. Winds will weaken this evening and become variable. Winds will intensify out of the west late Friday morning. There is a slight chance of thunderstorms tonight for MAF and FST. PREV DISCUSSION... /issued 240 PM CDT Thu May 18 2017/ DISCUSSION... Another hot and windy afternoon underway as the dryline continues eastward across the area. This boundary will waffle back and forth over our region the couple of days bringing chances for rain mainly for the eastern Permian Basin and Lower Trans Pecos. Much of W TX and SE NM has not received appreciable rainfall in over a month and fuels continue to dry. Thus the need for Red Flag Warnings over a large portion of the CWA. Please see the Fire Wx section below for more information. An upper level trough over the Rockies will lift into the Plains in the coming days. Height falls associated with this system will pull the dryline back west tonight to near the I-20 corridor. A shortwave will round the base of the trough overnight helping to increase large scale lift. Thunderstorms are expected to develop along the dryline after midnight and push east. Will follow the HRRR closest with respect to the position of the dryline since it did will Tuesday with a similar situation. Some of these storms will have the potential to be severe given adequate shear and steep lapse rates. Large hail and damaging winds will be the main threat with these storms. The dryline will move east again Friday with much of our area being the in dry air by afternoon. A cold front will head south as the upper trough lifts into the Plains Saturday. A few storms are possible along the boundary Friday night into Saturday mainly over the eastern Permian Basin and Lower Trans Pecos. Much cooler conditions are expected behind the front with below normal temperatures lasting through the weekend. We warm slightly early next week before yet another cold front makes a run at the area on Tuesday. A few more storms are possible with this front as well, but widespread precipitation is not looking likely at this time. FIRE WEATHER... Fuel conditions are pretty primed across the area today with the ERC at the 75th percentile across most of the PB and 90th across the Trans Pecos. Meanwhile critical fire is largely occurring across the area too with single digit RHs across much of the Trans Pecos. Winds are mostly 15-25 mph resulting RFTI of 3-4. RFW will continue until 9 PM CDT/8 PM MDT. Thur fire wx will be a concern again, but winds will probably be just a little less. 85h winds of 20-22kts may end up in a narrow corridor from the Upper Trans Pecos into the ne PB, RH will be no problem. As such most favored area for RF wx will be GDP Mtns/Upper Trans Pecos, possibly Eddy Co.? However fuels across the Trans Pecos including BBNP and SE NM are dry enough keeping Sig Fire Potential at least moderate? For now will issue a fire wx watch for the GDP Mtns for Fri, but could be expanded to included Culberson Co, Eddy County plains, most of the Trans Pecos for tmw as a fuel biased RF could be justified. && .PRELIMINARY POINT TEMPS/POPS... Big Spring 68 91 58 78 / 30 20 20 20 Carlsbad 58 85 52 81 / 10 0 0 0 Dryden 72 94 67 81 / 10 10 30 40 Fort Stockton 66 92 61 81 / 10 10 10 20 Guadalupe Pass 57 76 52 76 / 10 0 0 0 Hobbs 55 83 50 78 / 10 0 10 10 Marfa 55 84 45 81 / 10 0 0 10 Midland Intl Airport 63 92 57 81 / 20 10 10 20 Odessa 65 90 57 80 / 10 10 10 10 Wink 58 89 55 82 / 10 0 10 10 && .MAF WATCHES/WARNINGS/ADVISORIES... NM...Fire Weather Watch from Friday morning through Friday evening for Guadalupe Mountains. TX...Fire Weather Watch from Friday morning through Friday evening for Guadalupe Mountains. && $$ 80/44
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
911 PM CDT Thu May 18 2017 .UPDATE... 9PM CDT GOES IR imagery showed clear skies over the Midsouth, with cirrus approaching from southern plains storms. Temperatures prevailed in the lower 80s, expect over northeast MS, where mid/upper 70s prevailed in a more humid airmass. For the overnight last few runs of the HRRR and the 18Z/00Z NAM models show little to no rain over the Midsouth. HRRR does hint at some storms reaching northeast AR toward 7 AM, a southerly extension of a storm complex lifting across MO. Forecast was recently updated with a reduction in first period rain chances. PWB && .PREV DISCUSSION... /issued 639 PM CDT Thu May 18 2017/ UPDATE... Updated to add 00Z Aviation Discussion. PREV DISCUSSION... /issued 338 PM CDT Thu May 18 2017/ DISCUSSION... Current KNQA radar shows two areas of shower and thunderstorms occurring across the Mid-South. The first being Northeast Arkansas and the second being Northeast Mississippi. Expect this activity to die out around sunset. Expect the rest of the evening to be tranquil. Latest HRRR and NSSL WRF-ARW models show convection that is currently developing across Oklahoma to begin approaching the Eastern Arkansas around or shortly after midnight. Even the 3 KM NAM is indicating that this could happen. Although this model shows the line of convection dying as it pushes into the CWA. The other two models indicate the line may hold together to at least the Mississippi River. A lot will depend on the strength of the line as it pushes across Arkansas as the upper ridge remains fairly strong across the Mid-South. Will go ahead and bump up POPS to likelys across Randolph and Lawrence Counties after midnight. Will also have 40-50 POPS for the rest of Eastern Arkansas and the Missouri Bootheel. Elsewhere, expect stratus to invade the area around sunrise. Whatever convection remains after sunrise will diminish during the morning hours. Redevelopment will begin to occur by the early afternoon hours due to diurnal heating. Any thunderstorms that do develop on Friday will be very isolated to scattered in nature. Otherwise, expect another warm day across the Mid-South with highs in the upper 80s for the most part. Diurnal convection will quickly dissipate during the evening hours. Then all eyes will turn toward another possible line of thunderstorms that will be moving across Arkansas that could bring chances for showers and thunderstorms to Eastern Arkansas after midnight Friday Night into Saturday morning. By Saturday afternoon, expect numerous showers and thunderstorms to be developing across the Mid-South ahead of a cold front. Chances for convection will continue into Saturday Night into Sunday as the cold front pushes through the CWA. As for severe weather chances, can`t rule out strong to severe storms occurring with the convection after midnight tonight across portions of Eastern Arkansas or late Friday Night into Saturday Morning. By Saturday afternoon through the rest of the weekend, chances for strong to severe storms will occur across the entire Mid-South ahead of the cold front. Another cold front will move through the Mid-South on Tuesday and will bring additional chances for showers and thunderstorms. Wednesday will be a cool day across the Mid-South as an upper trof is expected to move through the area. Expect light showers or drizzle to occur with the trof. Highs will be in the upper 60s to lower 70s. KRM && .AVIATION... 00Z TAFs VFR conditions expected for much of tonight. MVFR ceilings are anticipated to develop across the Lower Mississippi Valley and into TAF sites between 10-12Z, with VFR conditions returning towards Friday afternoon. VCTS possible at all sites mainly after 19/18Z. Light south winds will increase to 10-12 kts with a few gusts to around 18 kts on Friday. CJC && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1042 PM CDT Thu May 18 2017 .UPDATE... Issued at 930 PM CDT Thu May 18 2017 Main concern tonight is the convective debris from storms that fired over central Kansas during the afternoon is screaming north and already working into the Twin Cities. This may keep us from having frost issues, with lows tonight likely staying up a couple degrees higher than we had, which would be enough to cut back on the frost potential. At this point, we`ll keep the frost advisory going, but confidence in the frost potential is decreasing. For tomorrow, have slowed the northward push of the rain chances as the 00z NAM has come in line with what most of the hi-res models are showing with rain making up to about Mankato before dry air takes over. Still looks like the big slug of rain comes up after midnight Friday night, with Saturday morning looking rather ugly with rain and temperatures in the 40s. && .SHORT TERM...(This evening through Friday) Issued at 253 PM CDT Thu May 18 2017 The low pressure system that moved through yesterday and last night, is still departing to the east with widespread low clouds in cyclonic circulation on the back side. The clouds have been eroding across northern MN as high pressure across south central Canada pushes in from the north. The eroding cloud trend will continue through tonight, with slow dissipation of the clouds expected across the area. The northerly flow is also bringing some pretty chilly air down from Canada as 850H temps are now flirting with the freezing mark. So, the main concern is for frost tonight and the most susceptible area is across northeast MN and northwest WI, and dipping into west central WI and parts of central MN. Forecast lows indicate cold enough temps for frost across these areas so went ahead and issued a frost advisory. We will have to watch the wind though because with the high well to our north, we may keep a slight breeze in our area tonight, whereas farther north confidence is higher that temperatures will dip. For tomorrow, shortwave energy and low level warm air advection will stream northward through Iowa into southern MN where rain is likely, but with the stout high pressure in place and very dry air from central MN and northward, the precip may not make it that far north. Another cool day with temepratures in the 50s with that cool airmass remaining in place. .LONG TERM...(Friday night through Thursday) Issued at 253 PM CDT Thu May 18 2017 Early afternoon water vapor imagery together Rap13 heights and winds showed a powerful cyclone approaching the TX/OK panhandles. This system will bring widespread rain across the entire region late Friday night into Saturday. This system will be slow to move out, so expect low clouds and a few showers to linger on Saturday. At this point Monday looks dry, but overall expect a cooler more cloudy forecast for the upcoming week with periodic chances for showers and thunderstorms. The threat for severe weather is very low. Saturday will be rainy as a large area of synoptic forcing associated with the height falls from the Upper Level wave lead to rising air, saturation, and rain. This is a large system so feel very confident that most if not all locations have measurable rainfall on Saturday. There are some slight timing differences between the models, and for that reason used 3 hourly precip grids, but increased the 12hr pop grid. Forecast soundings show little in the way of instability except for far southeast MN and western WI, so see this as mainly a light to moderate rain event. Total accumulations of around 0.75 inches can be expected. Wrap around could air advection will lead to cool temperatures on Sunday, and forecast soundings show overcast skies with enough instability atop the boundary layer to produce a few light rain showers, so tried to time increased pops during the heating of the day. Monday will be dry, but another northern stream shortwave will rotate across the region and bring another round of showers. Northerly flow will develop which should bring in some drier air and upper level subsidence for the end of the week. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1045 PM CDT Thu May 18 2017 Only change made to existing TAFs was to remove prob30s for -SHRA at MSP and RWF. 00z NAM has come in similar to what we are seeing with the RAP and HRRR that dry air locally will keep any rain Friday south of the MPX terminal. Main surge of rain Friday night looks to be coming after 06z. KMSP...we may see MVFR cigs and -RA moving in right at the tail end of the TAF, but with the dry air expected to be in place, felt better about taking a slower route to the arrival of both this far out. /OUTLOOK FOR KMSP/ Sat...MVFR/RA with IFR possible. Wind E at 10G20kt. Sun...MVFR. Chc -shra. Wind WNW at 15G25kt. Mon...VFR. Chc MVFR/-shra. Wind NW at 5-10kt. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...Frost Advisory until 8 AM CDT Friday for WIZ014>016-025-027-028. MN...Frost Advisory until 8 AM CDT Friday for MNZ043>045-052-053. && $$ UPDATE...MPG SHORT TERM...SPD LONG TERM...JRB AVIATION...MPG
Area Forecast Discussion...UPDATED
National Weather Service Omaha/Valley NE
726 PM CDT Thu May 18 2017 .UPDATE... Issued at 725 PM CDT Thu May 18 2017 Showers and storms continue to expand northward early this evening. Added some counties in eastern Nebraska to the Flash Flood watch, based on trends of storms to the south moving north. RAP model suggests potential for rain amounts of 1.50 inches or more over parts of southeast Nebraska by daybreak Friday morning. && .SHORT TERM...(Tonight through Sunday) Issued at 307 PM CDT Thu May 18 2017 ...Near-term forecast concerns are heavy rainfall potential across our southern counties tonight into Friday night... A prominent mid-level cyclone was analyzed over the central Rockies as of early afternoon with an associated vorticity lobe and attending jet streak pivoting northeast across the central and southern High Plains. At the surface, 19z analysis depicted an area of low pressure over southwest KS with an accompanying quasi-stationary front stretching northeast into northern MO. The influence of the above-mentioned vorticity lobe and jet streak on a strongly unstable air mass will yield widespread thunderstorm development this afternoon within the warm sector across KS into OK. Increasing moisture flux and warm advection along a nocturnally strengthening LLJ will aid in the northward movement of these storms into our area overnight. Isolated severe weather in the form of marginally severe hail and locally strong wind gusts is possible. However, the primary concern is flooding rainfall given the antecedent near-saturated soil conditions. As a result, we have issued a Flash Flood Watch from tonight into Friday night for several of our counties in southeast NE. We should see a break in the precipitation across much of the area Friday morning as the stronger forcing associated with the lead vorticity maximum lifts into the northern Plains. However, by Friday afternoon into Friday night, the primary mid-level system will shift east into the central Plains, contributing to widespread showers and thunderstorms. Current indications are that the system warm sector will remain to the south of the NE-KS state line with the primary concern again being flooding rainfall. The deep-layer synoptic cyclone will develop northeast into the upper Midwest on Saturday with drier conditions anticipated by afternoon. By Sunday, northwest, downslope flow in the low levels will support a warming trend with highs rising back into the 60s areawide. .LONG TERM...(Sunday night through Thursday) Issued at 307 PM CDT Thu May 18 2017 Latest medium-range guidance is in reasonably good agreement in suggesting that a substantial short-wave trough will track south through the mid MO Valley in the Monday-Tuesday time frame, supporting an increasing chance of showers and thunderstorms. Thereafter, building mid-level heights will signal a drier pattern along with gradually warming temperatures. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 654 PM CDT Thu May 18 2017 MVFR cigs and vsbys developing across the area through 06Z as showers and thunderstorms spread north out of Kansas. Periods of showers with cigs becoming IFR between 06Z and 12Z then continuing through remainder of the forecast period as upper low tracks into the western high plains. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Flash Flood Watch through late Friday night for NEZ050-051- 065>068-078-088>093. IA...None. && $$ UPDATE...Miller SHORT TERM...Mead LONG TERM...Mead AVIATION...Fobert
Area Forecast Discussion
National Weather Service Pueblo CO
743 PM MDT Thu May 18 2017 .UPDATE... Issued at 742 PM MDT Thu May 18 2017 Quick update to the forecast grids for latest obs data and radar trends. Added isolated pops for the southern foothills and I-25 corridor through 11 pm tonight. Moore && .SHORT TERM...(This evening through Friday) Issued at 301 PM MDT Thu May 18 2017 This afternoon, thunderstorms have fired along a boundary in southeast CO and are tracking northeastward. There will continue to be the potential for a couple severe storms over sern CO into this evening, with the main threat being large hail. This evening, the highest chances for pcpn are expected to be found over the central CO mtns, Teller county, Pikes Peak, and the southwest mtns. These areas will see some additional accumulations of snow. The latest run of the HRRR and the 18Z run of the NAM12 are showing decreasing chances of pcpn over El Paso county thru the evening hours, except maybe ovr the Monument Hill area where there could be a couple or a few inches of additional snow accumulation. After midnight, the HRRR and NAM12 show a significant decrease in pcpn chances across all of southeast and south central CO, with only some isolated showers. The GFS continues to show a little more pcpn than the other models, showing continued snowfall in the central mtns thru the night, and some light snow accumulations over Teller county and Pikes Peak, with some light showers over portions of the southeast plains, increasing toward 12Z. The NAM is a bit farther south with the upper low center Fri morning than the GFS. Both the NAM and the GFS show widespread pcpn moving into southeast CO after 12Z, with the GFS being wetter and more widespread than the NAM. At this time, it looks like there could be several inches of snow over the southern Sangre de Cristo mtns beginning Fri morning and thru the day, so will issue a Winter Weather Advisory. It is also possible that the southern I-25 corridor counties could see several inches of snow in the morning hours on Fri, mainly over Huerfano and western Las Animas counties and especially west of the Interstate, as temps are expected to be cold enough for a short period, but impact will probably be low as the roads will probably just be slushy or wet. One other worry is the potential for low temps tonight around freezing. Have decided to issue a Freeze Warning for northern El Paso county, and a Frost Advisory for southern El Paso, Huerfano and western Las Animas counties. .LONG TERM...(Friday night through Thursday) Issued at 301 PM MDT Thu May 18 2017 Friday night and Saturday...Models place a secondary piece of the upper low over the southeast corner of the state Friday evening, with snow for the higher elevations and rain for the lower expected to continue through the evening. As the low pulls off to the e-ne away from Colorado overnight, pcpn chances are forecast to diminish quickly after midnight with unsettled nw flow aloft then settling in. Another cold night on tap for the forecast area Fri night, and additional frost/freeze highlights will likely be needed tomorrow. Otherwise, look for temps to only warm into the 50s and 60s across the area on Sat. Sunday through Thursday...As the system exits the region, long range models continue to keep Colorado under active northwest flow, with multiple shortwaves crossing the region. There will be a nearly constant threat of at least isolated convection over the higher terrain and adjacent plains each day. A cold front dropping south across the eastern plains Mon aftn will produce cooler temps for Tue, then drier air filtering in behind is forecast to keep the cwa dry for Wed. Temps will climb into the 60s to lower 70s each day, but cooler on Tue with 50s and 60s expected. Moore && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 301 PM MDT Thu May 18 2017 At this time is looks like KPUB will mostly see VFR conditions tonight and into Fri morning, however there may be some showers or tstms in the area this evening. Fri morning there will be increasing chances for rain again and ceilings will lower, possibly into the MVFR category by late morning. KCOS will probably see some showers/tstms in the area this evening with periods of MVFR conditions. Chances for pcpn then are expected to decrease or end by late evening with VFR conditions. Chances for pcpn are then expected to increase during the day Fri, but VFR conditions are still expected until toward evening when ceilings are forecast to lower into the MVFR category. KALS is expected to have VFR conditions until around 13Z Fri and then the ceilings are expected to lower into the MVFR or IFR category. There may be some showers/tstms in the vcnty of KALS this evening, and could move into the area again Fri afternoon. && .PUB WATCHES/WARNINGS/ADVISORIES... Frost Advisory from midnight tonight to 9 AM MDT Friday for COZ085-087-088. Winter Weather Advisory until 6 PM MDT Friday for COZ059-063-066- 068-081. Winter Storm Warning until 6 PM MDT Friday for COZ058-060-082. Winter Weather Advisory from 6 AM to 6 PM MDT Friday for COZ074- 075. Winter Weather Advisory until 9 PM MDT this evening for COZ084. Freeze Warning until 11 AM MDT Friday for COZ084. && $$ UPDATE...MOORE SHORT TERM...28 LONG TERM...MOORE AVIATION...28
Area Forecast Discussion
National Weather Service Blacksburg VA
942 PM EDT Thu May 18 2017 .SYNOPSIS... High pressure east of the Carolinas will continue to produce a warm and humid southwest flow of air through tonight. The increasing moisture will result in a threat for widely scattered showers and storms into tonight, especially across the higher terrain. A weak cold front will approach from the northwest Friday, providing a better focus for showers and thunderstorms. && .NEAR TERM /THROUGH FRIDAY/... As of 935 PM EDT Thursday... The forecast update late this evening will account for a dissipation trend of the scattered showers and storms have have been near the VA/NC border. The latest radar trends have been showing a decrease in coverage thanks to loss of heating after sunset, and activity in the east progressing into dryer air. Have also tweaked hourly temperatures and dew points based upon the latest observations and trends into the early morning hours of Saturday. As of 750 PM EDT Thursday... Our forecast has been updated to reflect the better than anticipated coverage of showers and storms east of the crest of the Blue Ridge between rough Hillsville, VA and Prestonville, NC. This activity is expected continue progressing southeast this evening, but coverage will be waning as we lose the heating of the day and the activity moves into a dryer air mass. Other activity was focused across parts of the Northern Mountains of North Carolina, especially over portions of Watauga County. Elsewhere, have downscaled the extend of the anticipate scattered coverage across the mountains, to isolated or no coverage the remainder of this evening. As of 230 PM EDT Thursday... Convection has been slow to develop this afternoon likely due to mixing of dry air aloft and better focus remaining just west of the ridges along a residual trough axis. MLCAPE values also reflect a bit less instability with the best convergence along the southern Blue Ridge where expect more coverage to develop over the next few hours. However guidance remains inconsistent with the latest RAP showing some broken clusters western third, while the HRRR more of a shotgun pattern mountains into early evening. Therefore other than to cut back on pops initially will keep in chances mainly west until just after sunset for now. Initial shearing shortwave will pass well north tonight allowing for a continued weakening of the upper ridge overnight into Friday. May see a few showers linger due to possible outflow and leftover instability into late this evening, and over the far west for late tonight as perhaps another band of convection arrives ahead of an upstream cold front. This shown by a few models so after decreasing pops this evening, will bump back up espcly northwest by daybreak. Otherwise will call it mainly partly cloudy overnight under residual debris clouds including spots of stratus/fog late. Should be quite muggy with dewpoints keeping lows mostly in the 60s except for a few 50s valleys. Still some uncertainty with convective coverage Friday ahead of a slow moving backdoor front approaching from the north under flat flow aloft. Guidance does show a weak shortwave rotating in ahead of the boundary and may coincide with pre-frontal convergence during time of max heating to spark some deeper bands of storms espcly west in the afternoon. This in conjunction with better lapse rates aloft and decent instability without much cap. However flow/shear remains quite weak within a more westerly flow regime that could result in only scattered clusters of shra/tsra as suggested by the SPC-WRF/Nam, with perhaps a more organized area of convection to the northwest closer to the front. Also early clouds along with far western showers could hinder instability for a bit so running with mainly mid/high chance pops with brief likelys mainly southwest sections where late day convergence looks best. Appears temps similar to today pending the degree of insolation with highs mostly 80-85 mountains and mid/upper 80s east with more humidity around. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 230 PM EDT Thursday... A back-door cold front draped from Ohio to northern Virginia will sink south as a weak surface wave moves off the Virginia coast Friday night. This boundary will become stationary over southern Virginia Saturday morning. Some models are agressive with allowing this front to move south during the day Saturday. However, with a heat ridge across the southeast and no jet overhead, it will take some strong diurnal convection along the boundary to help it move south during the day. Strong convection maybe possible during the mid afternoon, but the boundary may not start moving until after sunset Friday evening. Convection likely Saturday afternoon for area outside of the wedge. Mechanisms will be a combination of diurnal heating, orographical and frontal lift. As storms get going in the mid to late afternoon, outflow boundaries will also help initiate convection over North Carolina. Areas inside the wedge could see a showers with a few rumbles of thunder from elevated instabilities. Tricky temperatures forecast Saturday depending on where the wedge stalls. Inside, temperatures will range from the upper 60s to mid 70s. Outside the wedge. temperatures could warm into the upper 70s to mid 80s. The wedge will sit over the area Saturday night into Sunday morning, then erode during the day Sunday as a front moves over the Ohio- Tennessee Valley. The piedmont may not see the wedge erode until late in the afternoon. Showers from the front will enter the mountains during the late afternoon/evening. Some strong storms are possible especially with an eroding wedge boundary. Majority of the showers will enter the mountains after peak heating, therefore limiting the potential of strong storms to just a few. Showers expected to move east of the Blue Ridge after midnight, then east over the coastal piedmont by noon Monday. Jet dynamics and instabilities remain high enough to keep some mention of thunder overnight. Another tricky temperatures forecast for Sunday with wedge eroding and convection coming in late in the afternoon from the next front. Thinking wedge will be gone by mid afternoon allowing temperatures to warm very quickly before frontal showers move in. Sunday afternoon temperatures should warm into the upper 70s to lower 80s. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 240 PM EDT Thursday... The front and rain will clear the area by Monday afternoon. High pressure will bring a brief period of dry weather from Monday afternoon into Tuesday evening. A strong cold front will move across the region Wednesday. A dry slot will grace the area Wednesday night then the upper level portion of the storm will move across the area Thursday. Temperatures will remain close to normal for early next week, then fall below normal to end the week. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... As of 740 PM EDT Thursday... Primarily VFR conditions prevail across the region. A scattered line of thunderstorms existed between roughly KTNB-KHLX-KMTV. Potentially, of the TAF locations, KDAN may be impacted by some of this activity over the next couple of hours. However, the trend should be a weakening on with the loss of daytime heating and the arrival of the precipitation into a dryer airmass. Localized sub-VFR ceilings and visibilities will accompany the heavy showers and storms within this activity. Sub-VFR conditions in the form of patchy fog will impact some of the terminal locations late tonight into early Friday morning. Any sub-VFR conditions will dissipate two or three hours after sunrise. Better threat for greater coverage of afternoon showers/thunderstorms Friday with periodic rounds of sub-VFR possible Friday afternoon/evening as a frontal boundary moves southeast toward the central Appalachians. Low clouds from earlier burn off of fog along with possible convection to the west could result in MVFR cigs through midday Friday mountains. Otherwise wont include any shra/tsra mention on Friday as appears most coverage wont occur until near or after the end of the valid TAF period. Extended Aviation Discussion... The front is forecast to stall across the region into this weekend, with best shower/storm chances over the mountains Saturday afternoon/evening. Coverage should then trend more isolated until late Sunday as this residual boundary lifts out to the northeast ahead of another cold front approaching from the west. This front may then bring another round of deeper convection to the mountains by Sunday evening and over much of the region into Sunday night. Front crosses the region Monday morning with possible residual sub-VFR in the east early on and across the mountains due to upslope flow through much of the day. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/PM NEAR TERM...DS/JH SHORT TERM...RCS LONG TERM...RCS AVIATION...DS/JH/PM
Area Forecast Discussion
National Weather Service Shreveport LA
1000 PM CDT Thu May 18 2017 .DISCUSSION... The evening satellite imagery indicates an extensive area of convective debris spilling E into the region from the ongoing MCS over Srn/Ern OK, as well as sct supercells over Wcntrl TX. Isolated to widely sct convection has increased over the last hour or so over McCurtain County OK as well as the Nrn sections of SW AR, where Srly low level winds just away from the LLJ have increased to 30-40kts ahead of a broadly difluent region over much of OK well ahead of the upper closed low spinning over Wrn CO this evening. Although the earlier progs had suggested MCS development a little later tonight where convection is ongoing attm, the HRRR is also having to play catchup with the Srn most edge of the bow about to enter Nrn Atoka/Pittsburg Counties in SE OK possibly affecting Nrn McCurtain County OK between 04-05Z, should it backbuild farther S. However, the progs do suggest that this convection should continue to build more NE overnight, consistent with embedded shortwave energy also ejecting NE ahead of the closed low. The air mass over this region remains moderately unstable this evening with MLCapes of 2500-3000 J/Kg, with strong capping noted on the 00Z KSHV raob near H700 (and even weak capping noted at FWD) limiting the Swd extent of convection development overnight. Still can`t rule out an isolated svr threat for our far NW counties given the extent of instability and the increasing SSW LLJ, which should help sustain convection through at least a portion of the overnight hours. Have updated the forecast to lower pops a bit over SW AR/extreme NE TX, but did maintain low to mid chance pops across the far NW zones. Also removed pops for much of E TX/N LA/Scntrl AR as the isolated and rogue -SHRA have diminished with the loss of heating. Given the Srly winds staying up overnight, and the extensive convective debris spreading E, with additional low stratus developing/advecting N late, have bumped up min temps slightly with temps only falling into the lower and mid 70s, with the warmer temps confined to portions of E TX/extreme NW LA. Zone update already out...grids will be available shortly. 15 && .PREV DISCUSSION... /issued 712 PM CDT Thu May 18 2017/ AVIATION... For the ArkLaTex, VFR even with vcsh near KLFK for a few hrs. Overnight, Southerly winds will slack gust but keep 5-15KT. Climb winds are S20-30KT and SW30-50KT for flight levels. Expect stratus decks IFR/MVFR 09Z-18Z. A weak system approaching will time well with afternoon heating on Friday for a few terminals with VCTS late this cycle as clouds scatter to VFR. Area outlook remains unsettle into weekend with a stronger system/fropa. /24/ && .PRELIMINARY POINT TEMPS/POPS... SHV 74 88 73 83 / 10 30 20 60 MLU 72 88 72 86 / 10 30 20 50 DEQ 69 85 69 79 / 30 30 50 80 TXK 72 85 71 80 / 20 30 40 70 ELD 72 87 71 82 / 10 30 20 60 TYR 74 89 72 81 / 20 30 40 80 GGG 74 88 72 82 / 10 30 30 70 LFK 73 89 73 85 / 10 30 20 60 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$ 15
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Tonight) Issued at 159 PM CDT Thu May 18 2017 Focus for tonight will be the threat for severe weather across northeast Kansas. This afternoon, a warm front was noted across east central Kansas oriented from east to west. Main concern this afternoon will be if storms begin to develop along this warm front as the HRRR has been depicting in model runs. CAPE near/south of this boundary is over 3000 J/kg with effective bulk shear values of 50 knots. During the afternoon hours, the NAM also shows 0-1 shear along this boundary around 25 knots, with steep mid-level lapse rates. Any discrete storms forming along this boundary will have the potential to quickly become supercellular with the main hazards being large hail, damaging winds, and tornadoes. If storms do form this afternoon, exact details for tonight look more unclear as instability will be weaker and subsidence from storms may act to alleviate severity later tonight. For tonight, storms that are expected to fire up on the dry line located in southwestern Kansas and extending southward into Oklahoma. Models have been fairly consistent in having these storms congeal into a line/bow and move through northeast Kansas this evening. This would bring a main hazard of widespread wind damage across the area, although hail or an embedded spin up tornado cannot be ruled out. Additional development behind this line is possible bringing another round of heavy rain to the area, increasing the potential for flash flooding. This is especially true in areas in north central Kansas that have already seen heavy rainfall totals earlier in the week. With the potential for more developing showers and thunderstorms tomorrow, a flash flood watch has been issued for the entirety of northeast Kansas beginning this afternoon and extending into Saturday morning. .LONG TERM...(Friday through Thursday) Issued at 159 PM CDT Thu May 18 2017 The vast majority of the long term forecast period forecast effort focuses on Friday and Friday night severe/flooding potential, with periods beyond that generally trending toward a model consensus at this time with minimal expected impacts through the remainder of the forecast. For Friday, much of the details will lie in how quickly convection exits the area early Friday morning. Current indications are that it will make a substantial eastward push overnight and exit the region early. If this occurs, it would give much of the forecast area more time to recharge instability as the true warm front surges/mixes back north during the day in advance of a strong upper level trough. Long, clockwise curved hodographs with low LCL/LFC heights and rather steep lapse rates through the cloud- bearing layer all point to another day with widespread severe weather potential. This will include tornado potential across the warm sector, and the most likely this warm sector will include much of eastern Kansas with main uncertainty being in the northwestward extent. There are two potential limiting factors. 1) Early day convection ends late and keeps the boundary layer stable for much of the day, effectively mitigating instability. 2) Storms develop too close to each other, resulting in continued hail and damaging wind potential but limiting overall tornado potential. Regardless, severe storms are possible with some potential for another higher-end episode of severe weather. The other concern will be flash flooding with multiple rounds of thunderstorm again possible over what is likely to be saturated ground conditions with elevated stream levels after tonight`s storms. WPC has the area in a moderate risk for excessive rainfall and for good reason, so have continued the flash flood watch through Friday night. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 636 PM CDT Thu May 18 2017 VFR conditions will occur outside of convection through 07Z. MVFR cigs are expected after 07Z and prior to that with convection. MVFR and ifr vsbys are expected with storms. Showers along with isolated tsra are expected at TOP and FOE from 07Z-12Z then again after 18Z Friday. Also some ifr cigs may move into the MHK area after 19Z. && .TOP WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Saturday morning for KSZ008>012- 020>024-026-034>040-054>056-058-059. && $$ SHORT TERM...Heller LONG TERM...Barjenbruch AVIATION...53