Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/26/18

Area Forecast Discussion
National Weather Service Green Bay WI
617 PM CST Sun Feb 25 2018 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Monday Issued at 236 PM CST Sun Feb 25 2018 The latest RAP analysis and satellite/radar imagery show a potent low pressure system moving northeast over northern Ontario. Low clouds continue to wrap around the low and across northern WI, though the light snow and flurries ended early this afternoon. A few lower visibilities continue over north-central WI though, due to blowing snow. Clouds have been gradually retreating northward through the day, with most areas south of highway 29 seeing clearing skies. Winds have also gradually diminished after peaking early this morning, and this trend should continue through the night. Secondary wind gust max, as depicted by progged soundings, hasnt quite materialized early this afternoon. So with coordination from MKX, will let the advisory expire at 3 pm. As high pressure over the Ohio Valley builds north, cloud trends is the main forecast concern. Tonight...As low pressure continues to lift off to northeast Canada, high pressure centered over the Ohio Valley will gradually build into the region. The gusty winds will continue to diminish as the pressure gradient slackens and nocturnal cooling sets in. Clouds will be a bit more stubborn, with an area of clouds over the WI/MN border expected to move into central WI early this evening. Thereafter, clouds are expected to to retreat northward relatively quickly. Will have enough winds in the boundary layer so decoupling is not anticipated, and so went with the best performing guidance for lows. Temps falling into the mid- teens north to the mid 20s south. Monday...High pressure will continue to dominate our weather. Under plenty of sunshine, south winds will push highs into the upper 30s to mid 40s across the region. .LONG TERM...Monday Night Through Sunday Issued at 236 PM CST Sun Feb 25 2018 A weak cold front will slowly move through the forecast area on Tuesday and Tuesday night, then slide southeast of the region on Wednesday. The front may generate some light rain and snow over mainly the southeast half of the forecast area Tuesday evening, with dry conditions returning by Wednesday. Temperatures are expected to warm well into the 40s ahead of the front on Tuesday, then settle back into the upper 30s and lower 40s on Wednesday. A sharp upper trof crossing the central Rockies will induce cyclogenesis near the Texas/Oklahoma Panhandles during the midweek period. This low (and the associated deepening upper trof/low) is expected to track northeast along the stalled frontal boundary toward Chicago/southern Lake Michigan late Wednesday night into Thursday morning, then get shunted east through the northern Ohio Valley. The GFS continues to be farther north with the sfc/upper lows, and brings the potential for heavy snow into central and east central WI (similar to the 00z ECMWF), while the 12z ECMWF is farther south and keeps the heavy snow to our south. Surface/ 925/850 mb temperatures and low-level thicknesses support mainly snow, with some mixed precipitation in parts of east central WI early in the event. The GFS continues to show some potential for strong northeast to north winds, and possible Gales on Lake Michigan Thursday and Thursday night. Will continue to mention this system in the HWO, but with significant model differences, will hold off on any specific details at this time. Quiet weather is expected to return as high pressure arrives Friday into Saturday. Precipitation may develop as the high shifts east on Sunday. Seasonal temperatures are anticipated over the weekend. && .AVIATION...for 00Z TAF Issuance Issued at 555 PM CST Sun Feb 25 2018 MVFR cigs may drift over parts of north central and central Wisconsin this evening, otherwise vfr conditions will prevail this evening along with diminishing west to southwest winds. VFR will continue into Monday as high pressure drifts across the mid section of the country. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......Kieckbusch AVIATION.......TDH
Area Forecast Discussion
National Weather Service Wilmington NC
731 PM EST Sun Feb 25 2018 .SYNOPSIS... A cold front will move offshore early Monday, pushing the record warm temperatures out to sea. High pressure will build across the central Appalachians behind the front, then will move off the Virginia coast Tuesday night. A warm front will lift north across the area Wednesday. Strong low pressure will push a cold front across the area Thursday night. && .NEAR TERM /THROUGH MONDAY/... As of 730 PM Sunday...Although the actual surface cold front is still back across central Virginia and the mountains of North Carolina, a prefrontal trough and wind shift has reached the coast of the Carolinas. This boundary helped develop shallow convection this afternoon where RAP 0-hour forecasts showed surface-based CAPE values of 300-500 J/kg in spots. The potential for convection has ended with the loss of daytime heating, and in fact it looks like we`re entering a lull for rainfall chances for the rest of the evening. Precip chances will ramp back up from southwest to northeast late tonight as a wave of low pressure develops across Alabama and Georgia. Backing wind directions across the 850-700 mb layer should begin to cause an increase in isentropic lift which should trigger the development of rain late tonight. The bulk of this lift should reach the area after daybreak where measurable precipitation chances remain near 90 percent for Monday. Changes with this forecast update include adjustments to sky cover forecasts to show a couple hours of clearing skies this evening, minor downward tweaks to forecast low temperatures given this unexpected brief window for radiational cooling, and minor edits to wind speeds and directions. Discussion from 300 PM follows... Another record breaking day going down in the books for both FLO and ILM. An 88 year old record maximum temperature broken at ILM this afternoon by reaching 82 deg. FLO had no problem demolishing the 79 degrees set last year, currently at 83 and climbing. The ocean cooled air at the Myrtles is making it difficult for CRE to reach record values this afternoon. The pre-frontal trough crossing I-95, will merge with the sea- breeze convergence line from 4pm-6pm, off the coast by very early evening. Low-level winds of 20-30 kt, and a strong cap of dry air aloft, will prevent hazardous weather this afternoon and tonight, but gusts in stronger showers to 35 mph cannot be ruled out entirely. Cool water and diurnal cooling will kill this line quickly off the coast after 6 pm. This may leave a quiet overnight period, with little forcing, until weak upper support arrives into daybreak, and the onset of low-level over-running gears up. The front should already be through SE NC and NE SC by daybreak Monday, and maximums Monday, holding below 70 in most if not all locations through the day. Isentropic lift strengthens on Monday, co-joined with elevated PWAT values exceeding 1.5 inches, so expecting a good little soaking Monday. Yes there may be periods of non-rain Monday, but latest QPF best-fit line, gives us about 1/3 inch average across NE SC and SE NC, most of it Monday, a little more Monday night. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...Cold front to the southeast will be moving away from the area as the period begins. Front will be followed by surface high building in from the north. Lingering low level moisture may lead to some areas of light rain or drizzle for the first few hours of the period. However, cooler and much drier air starts spreading in from the north-northeast as early as midnight. Remainder of the period will be dry with flat pattern aloft trending toward subtle ridging as the 5h Gulf of Mexico ridge expands north. Forecast soundings show mid- level subsidence starting to increase as early as daybreak Tue and peaking in strength early Wed morning. There will be upper level moisture moving across the top of the ridge late Tue and Tue night, ahead of a system moving across the southern MS Valley. This will result in increasing high clouds late Tue and Tue night. Despite the increase in high cloud rainfall before the end of the period is unlikely. Forecast soundings show no appreciable moisture below 15k ft as well as strong downward motion. Temperatures above normal will continue through the period. Lows each night will dip into the mid 40s for most areas. Only exception could be Tue night in spots that typically run colder on good radiational cooling nights. Right now it appears that increasing high clouds Tue night will prevent strong radiational cooling, but if clouds are slower to develop or thinner, the typical cold spots could drop into the mid 30s. Highs Tue will be in the low to mid 60s accompanied by abundant sunshine. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 300 PM Sunday...Wednesday looks unsettled as a warm front is slated to lift through. However despite widespread cloud cover and rain chances the prospects for QPF appear low due to WNW downsloping mid level flow. On Thursday we wind up in the narrow warm sector of the occluded system crossing the southern Great Lakes. Low level wind fields will be rather strong so given ample sunshine some instability should develop. Will add isolated thunder to the forecast especially as the front looks a little faster and may arrive not long after peak heating. Thursday night into Friday will be quite breezy in the well-mixed CAA regime (especially Friday when insolation will deepen the mixing). All weekend will find cutoff/occluded cyclone well off the Delmarva. The resulting NE surface flow will bring seasonable to slightly cool temps. Some wrap- around moisture may make it this far south in the form of low cloudiness from time to time. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... As of 00Z...Terminals are VFR this evening. Showers are occurring along a surface boundary which is currently moving offshore of KILM, and -RA is occurring north of KLBT. VFR expected through 11-12Z. Some patchy BR/IFR stratus is possible overnight across the area, but will not indicate in TAFs attm due to light patchy nature of rain today. A cold front will move through the terminals overnight but wind speeds will remain very light. MVFR will become more likely tomorrow morning as rain increases. Winds will be northeast through the day, except at KCRE/KMYR where northeast winds will become southeast by late morning. Winds will then become northeast as a surface low passes. By the end of the TAF period IFR cigs likely at all terminals, except for MVFR at KFLO. Extended Outlook...Becoming VFR overnight Mon. VFR Tue. Periods of MVFR/SHRA Wed-Thu. VFR Fri. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 730 PM Sunday...Although the actual surface cold front remains back across the mountains of western North Carolina extending into central Virginia, a prefrontal trough reached the coast late this afternoon with a shift to northwest winds. Stronger wind speeds ended with the arrival of this trough, and the `exercise caution` headline has been dropped. We`re in for lighter wind speeds for the overnight period ahead of the front, generally 10 knots or less. Isolated showers this evening may increase in coverage late tonight as a wave of low pressure developing across Georgia begins to pull moisture back across the region from the south. Changes with this update include dropping the `exercise caution` headline, adjusting wave height forecasts downward tonight through Monday morning, and minor adjustments to wind speed and direction based on the latest HRRR/RAP forecast models. Discussion from 300 PM follows... 0-20 NM are considerably more challenging than 24 hours ago, as wind-waves have erupted across the waters, in response to blustery SW wind. Outer water approaching 5 ft at this time, 3-4 feet inshore, and 4-5 seconds wave periods will become the dominant energy, making for higher wave- steepness. An `Exercise Caution` flag is flying for all waters, for 5 ft waves offshore, and SW gusts to 20 kt common. No TSTMS expected but a line of showers make rake the inshore waters after 6 pm, spurring gusty and erratic winds briefly early this evening. Winds will ease overnight as the front nears, shifting to north in the pre-dawn hours, before daybreak all marine zones. Winds to become perhaps E 15 KT Monday afternoon, but NE winds will ram up notably, heading into Monday night. SHORT TERM/MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 300 PM Sunday...Cold front will be south of the area as the period begins with northeast surge setting up. Northeast flow late Mon night and early Tue will be 20 to 25 kt with gusts in excess of 30 kt likely. Surge will be of short duration but seas building to 7 ft in the vicinity of Frying Pan Shoals are likely. A short duration SCA will likely be needed Mon night into Tue. Gradient starts to relax on Tue with speeds decreasing in the afternoon. Northeast flow continues into Tue night before the high starts to sag south, veering winds to easterly early Wed as the center of the high slips off the NC coast. Seas start falling late Tue afternoon and may be as low as 2 to 3 ft by the end of the period. LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 300 PM Sunday...Light southerly flow with a warm front lifting through the area. Following its passage winds will turn to SW and start increasing on Thursday. While wind speeds will remain below thresholds it looks like some advisory-worthy 6ft seas are possible. Cold frontal passage will lead to a sharp turn to the NW and no appreciable decrease in wind speeds. If anything the range of gusts may open up. Advisory may be maintained for at least part of Friday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...MJC/TRA SHORT TERM...JDW LONG TERM...MBB AVIATION...MRR
Area Forecast Discussion
National Weather Service Jacksonville FL
721 PM EST Sun Feb 25 2018 .UPDATE...Radar shows a few showers ongoing from JAX area to SSI along sea breeze and outflows...activity will gradually diminish next few hours...then partly cloudy skies. HRRR and SREF focusing on western half of forecast area for areas of dense fog after midnight. Will continue areas of dense fog western counties of ne FL...more patchy in nature further E to St. Johns River. Another mild night with low temps in the lower-mid 60s. && .AVIATION...VFR conditions expected tonight and Mon. May have patchy fog affect KGNV and KVQQ sites 08z-12z. && .MARINE...No changes planned in next CWF issuance. High pressure will build SE of area early Monday. A cold front will slide across the area waters Monday afternoon and evening. High pressure will build to the North on Tuesday, then to the Northeast Tuesday night, as the front lifts back to the North as a warm front. High pressure will be to the East then Southeast Wednesday into Wednesday night. A strong cold front is expected to pass Southeast across the region Thursday night, with high pressure building to the West on Friday. Rip Currents: A low risk is expected Monday. && .PRELIMINARY POINT TEMPS/POPS... AMG 63 78 57 70 / 20 60 30 10 SSI 64 77 60 65 / 30 30 40 10 JAX 64 83 63 71 / 20 20 30 10 SGJ 66 84 64 71 / 10 10 20 20 GNV 63 83 64 75 / 10 10 20 10 OCF 63 84 65 79 / 10 10 20 10 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. && $$ Wolf/Hess/Peterson
National Weather Service Jackson KY
948 PM EST Sun Feb 25 2018 .UPDATE... Issued at 945 PM EST SUN FEB 25 2018 A boundary remains stalled out to the south of the area. A mid level disturbance is expected to interact with the boundary with at least one sfc wave of low pressure developing and moving along the boundary. The deepest moisture and lift should remain south of the area later tonight and into early on Monday. The models still vary in how far north measurable light rain will reach, but the consensus is that the highest chance for measurable precipitation will be along the TN and VA border counties from Whitley and Bell through Harlan and into Letcher. Locations further north and west will be closer to surface high pressure gradually building into the area and should not experience more than mid level clouds. Some slight adjustments have been made to pops prior to 6Z or 1 AM. The latest HRRR as well as 18Z and 0Z NAM as well as 12Z and 18Z GFS guidance and radar trends suggest that light rain should not reach the KY/TN/VA tri state area until after 6Z. Measurable pops have generally been held to along and south of KY Highway 80 with an area of possible sprinkles in a narrow stripe further north. Likely pops from southeast Whitley County through Bell and into Harlan County. Rainfall there should be light, generally a tenth of an inch or less. && .SHORT TERM...(This evening through Monday night) Issued at 240 PM EST SUN FEB 25 2018 19z sfc analysis shows just about all of eastern Kentucky now in the wake of a departing cold front. This front is taking the lower clouds east along with it as high pressure bubbles in from the west. The relaxing of the pressure gradient from this high`s approach has lightened the winds, though they are still cold advecting - generally from the northwest. Temperatures currently vary from the low 50s northwest to the upper 50s southeast while dewpoints range from low 40s west to the lower 50s in the east. The models are in good agreement aloft through the short term portion of the forecast. They all depict broad southwest flow continuing over the area between strong ridging above Florida and troughing north of the Great Lakes down to the Southern Rockies. The tail of the northern trough will weaken and head into the Ohio Valley later tonight into Monday morning. From this, a weakening batch of energy and slight height falls pass through eastern Kentucky during the day Monday. Following this, ridging and gently rising heights will move over the area into Tuesday morning. Given the model similarities will favor a blended solution with an emphasis on the details from the higher resolution NAM12 and HRRR in the near term. Sensible weather will feature mainly just high clouds around this evening and overnight as high pressure builds into the area. However, one last wave along the past frontal boundary will move through the Southern Appalachians tonight brushing far southeastern parts of the CWA with a decent chance of rain showers. Otherwise, all will be quiet through eastern Kentucky with relatively mild overnight lows on tap in the upper 30s north to mid 40s south. Monday will be a nice day under high pressure with plenty of sunshine and temperatures climbing into the mid to upper 50s. As the high pressure area moves east Monday night, a night of good radiation cooling will likely set up a moderately large ridge to valley temperature split with the hilltops in the mid 30s and most sheltered valleys falling into the upper 20s. Also, look for valley fog to develop late at night and possibly be thick near the rivers and larger bodies of water. Used the CONSShort and ShortBlend as the starting point for all the grids through Tuesday morning. Did make some significant changes to the valley locations for lows on Tuesday and also some point specific temps tonight and Monday. As for PoPs, limited the measurable rainfall to just the far southeast tonight and only for a window of time from 06 to 12z - narrower in areal and temporal extent than the blends. .LONG TERM...(Tuesday through Sunday) Issued at 316 PM EST SUN FEB 25 2018 There is good model agreement with the evolution of the mean flow during the upcoming week and fairly good agreement with the main weather makers for our area. With surface high pressure slipping to our east at the start of the forecast period, and weak upper ridging over the area, we`ll have a warm dry day on Tuesday. On Wednesday an upper level trough will be moving out of the southwest U.S. as a surface low develops in the southern plains. A leading short wave trough will bring showers to the area on Wednesday. A more significant round of showers will occur Wednesday night into Thursday as the southern stream trough begins interacting with some northern stream energy and develops into a closed upper low. The associated surface low will deepen from Wednesday into Thursday as it moves into the northern OH Valley-southern Great Lakes area. There is model agreement that the axis of heaviest rains from Wednesday into Thursday will fall south of Kentucky, but the southern part of the forecast area could still see significant rains, especially Wednesday night into Thursday. The current forecast calls for 1.5 to 2 inches in the southern part of the forecast area from Wednesday into Thursday, so this will need to be watched. It is possible some local high water issues could develop by Thursday. Temperatures will be well above normal for the first part of the forecast period, but colder air will spill into the area by Friday with more normal temperatures for the start of next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) ISSUED AT 740 PM EST SUN FEB 25 2018 VFR conditions will prevail through the period for all the TAF sites. An increase in mid level clouds is expected from south to north between 3Z and 9Z, though some MVFR cigs and possibly vis is probable from 5Z to as late as 16Z or 17Z nearer to the VA and TN borders as a surface wave passes through eastern Tennessee tonight into early on Monday. Winds will generally be light and variable through the period as high pressure gradually settles over the area, especially after the surface low moves toward the eastern seaboard. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GREIF LONG TERM...SBH AVIATION...JP
Area Forecast Discussion
National Weather Service Marquette MI
640 PM EST Sun Feb 25 2018 .SHORT TERM...(This evening through Monday) Issued at 406 PM EST SUN FEB 25 2018 WV imagery and RAP analysis indicated a broad mid/upper level trough through the central CONUS with and a vigorous shortwave lifting ne through nrn Ontario to near James Bay. At the surface, a 984 mb low was located just sw of James Bay resulting in a tight pressure gradient through the nrn Great Lakes. w or wsw winds have gusted to around into the 50-55 mph range at KCMX and mainly from 40-45 mph over much of west and n cntrl Upper Michigan bringing plenty of drifting snow. Otherwise, the cyclonic wrly flow and lingering low level moisture has kept skies mostly cloudy over the rest of the cwa. Tonight, models suggest that the strong winds will gradually diminish into this evening. So, the 00z wind advisory expiration looks on track. However, winds will remain strong enough overnight to maintain mixing with temps only falling to around 20 even with some clearing. Monday, with a transition to a more zonal patter, mild Pacific air will spread into the region on sw low level flow WAA. Under sunny skies, with 900 mb temps to around -3C, temps should climb into the lower 40s over the west, toward the higher end of guidance. .LONG TERM...(Monday night through Sunday) Issued at 257 PM EST SUN FEB 25 2018 Overall, the weather looks to remain fairly quiet through the extended across Upper Michigan as zonal flow dominates the upper- level pattern through the middle of the week. Later this week, the northern and southern streams of a longwave trough will phase across the Middle Mississippi Valley and allow for a deepening surface trough to track across the far lower Great Lakes region. There is still quite a bit of uncertainty in how for north precipitation will get with this system, but right now it looks like Upper Michigan will be right on the edge of it. Temperatures wise, we`re not looking at any sharp, dramatic cool downs, with temperatures remaining mostly above normal for this time of year. Tuesday through Wednesday: As previous mentioned, flow will remain predominately zonal through this time period; however, a weak shortwave will drop south Tuesday night into Wednesday pushing a weak cold front through the region. Ahead of this front, on Tuesday return flow will allow temperatures to warm into the 40s across much of the area. As the front makes its way south across Upper Michigan we could see some snow/rain showers associated with this front across the south central and east, but this will highly depend on how far north mid-level moisture can return prior to the arrival of the shortwave. Behind the front, temperatures will cool down, but with the cold air advection not being terribly impressive we`re not looking at a sharp/dramatic cool down. As high pressure takes over expect ample sunshine and drier weather on Wednesday. Thursday through next weekend: As the above mentioned longwave trough becomes better organized across the Middle Mississippi Valley and the main surface low tracks across the lower Great Lakes region, cloud cover will increase through the day on Thursday. Right now uncertainties still exist in how much moisture will be able to return this far north. Given the strength of the Hudson Bay high during this time period and the amount of drier air being pulled southward on the north and west side of the surface low, not terribly excited about our precipitation changes with this system on Thursday. Therefore, lean towards the ECMWF/Canadian solutions, which favor a further south track for the system precipitation, and did at least lower PoPs across the northern half of our CWA. For collaboration sake, did opt to maintain at least chance wording across the south half. Even if we don`t see any precipitation from this system, the increasing pressure gradient should at least allow for breezy conditions across much of the area. As winds become northerly on the backside of the system Thursday night into Friday expect lake effect clouds and perhaps some very light wintry precipitation across the north wind snow belts. Right now 850mb temperatures are only progged to be around -8C to -10C so it may be a stretch to even get any snow out of the lake effect clouds at times. On Friday, high pressure will start to dominate and allow any lingering precipitation to come to diminish. Next weekend upper-level ridging will dominant and allow for the dry weather to continue. Towards the end of next weekend, another system is progged to eject out of the intermountain west. Per usual model solutions diverge significantly in the track/speed/timing of this next system, especially considering it appears we may have an omega block-like pattern slowly evolving across the CONUS. This would favor the slower solutions, such as the ECMWF/Canadian. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 640 PM EST SUN FEB 25 2018 As low pres over James Bay continues to lift farther to the ne, MVFR cigs at KIWD/KCMX/KSAW will lift and/or scatter out tonight. At KCMX, IFR vis from ongoing -shsn and blsn due to winds gusting above 30kt will improve this evening as winds gradually diminish. VFR conditions will prevail at all terminals on Mon. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 406 PM EST SUN FEB 25 2018 As low pressure continues to lift northward to James Bay westerly gales to 45 knots with some storm force gusts will diminish this evening and end after midnight over the east. Monday through the middle of next week, winds in the 20 to 30 knot range early Monday and again Monday night will gradually weaken to less than 15 knots by Wednesday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Wind Advisory until 7 PM EST this evening for MIZ001>005-084. Lake Superior... Gale Warning until 1 AM EST Monday for LSZ266-267. Gale Warning until 10 PM EST /9 PM CST/ this evening for LSZ162- 263>265. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...Ritzman AVIATION...Rolfson MARINE...JLB
Area Forecast Discussion
National Weather Service Blacksburg VA
918 PM EST Sun Feb 25 2018 .SYNOPSIS... A cold front from Lake Ontario to central Mississippi will move southeast tonight, stalling briefly over Virginia and Tennessee, before moving across the southeast United States on Monday. High pressure follows the front and will over the Mid Atlantic States on Monday night and Tuesday. A deep low pressure system will track into the Ohio Valley on Thursday and push a strong cold front through the area Thursday night and Friday. && .NEAR TERM /THROUGH MONDAY/... As of 918 PM EST Sunday... Cold front moves southeast through the region tonight into Monday. Adjusted temperatures and pops for this evening into tonight. Slowed the arrival time of rain in the southwest closer to NAM and HRRR. Also, extended the north edge of rain overnight into Monday morning. Lowered low temperatures in the west a few degrees overnight. As of 625 PM EST Sunday... Made some minor adjustments in temperatures for this evening utilizing the latest surface obs, their trends and shaped towards GLAMP. In general, lower temperatures in the west to capture drop this evening into tonight. Overnight low temperatures expected to be from the mid 30s in the northwest mountains to lower 50s in piedmont. More adjustments later tonight. As of 300 PM EST Sunday... 500MB flow remains southwest tonight and Monday which will limit/slow down southern advance of cooler and drier air. Southwest Virginia, southeast West Virginia, and northwest North Carolina stay in broad upper diffluence until Monday afternoon. At the same time weak pieces of short wave energy track through the area from the southwest. 12km NAM showed good insentropic lift tonight in the 800- 600MB layer over southern Virginia and northern North Carolina, especially after midnight. The surface front extended from near Pittsburgh to Nashville this afternoon. The surface and 850 MB front stall around the Virginia/North Carolina border this evening, then slowly move south throughout the day Monday. Winds turn to the northwest and north Monday behind the front. Areal coverage of showers will continue to diminish this afternoon, then fill back in between 00Z/7PM and 06Z/1AM. SOme differences in the guidance with northern extent of precipitation, with the NAM and HRRR as far north as Lewisburg and Hot Springs. Clouds and precipitation Monday morning will hold back on heating and with much of the region on the north side of the front, plan on lowering maximum temperatures. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 310 PM EST Sunday... Surface cold front hanging around just south of the NC border on Monday then shifts southward essentially as a wedge front early Monday evening. This will lead to rapid clearing and drying as large surface ridge associated with cooler low-level air mass than experienced recently builds into the VA Highlands into central WV. Good radiational cooling and 850mb temperatures within a couple degrees of zero supports lows in the upper 20s to middle/upper 30s. Will still need to watch for overnight mist or fog with radiation inversion setting in, winds trending calm, and wet ground from a couple days worth of rain, though confidence isn`t high enough to place in the forecast. Quiet and rather pleasant Tuesday on tap as high pressure progresses east late in the day, though a bit cooler temps in the 50s than experienced recently. Tuesday night will feature clear skies initially, but then increased isentropic lift from the southwest will force greater/lowering cloud cover ahead of a warm front. Will show limited chances for rain - slight/low chance - mostly west of I- 77 into the pre-dawn Wednesday hours, but best chance of rain is Wednesday. Timing of the cloud cover suggests that areas north/east of I-77 stands a fair shot at seeing lows around sunrise, and somewhat earlier on the other side of I-77. Elongated west-east warm front, associated with a potent southern- stream shortwave trough way back into the southern Rockies/Plains region, then begins to spread northward. I say begin, because unlike yesterday, it`s not clear in the 12z NWP suite exactly how far north the warm front gets. The NAM`s position is the southern outlier - roughly along I-40 in NC - while the GFS is the furthest northeast, closer to the Route 460 corridor. The ECMWF and GEM are somewhere in between. Model-generated QPF also falls on the cooler side of the frontal zone, which if is the case would favor a slower frontal position. All that said, did opt to sharpen PoPs/QPF some across the forecast area Wed/Wed night, showing Likely to Categorical from roughly give-or-take southwest of the Roanoke River with better proximity to the warm front, with chance north. It`s not until the after-midnight period when it`s generally agreed upon that the warm front begins to move northward where the best chance of rain areawide occurs. Regardless, this is likely to be the start of a rather active period, with warm-frontal QPF values between a quarter to three- quarters of an inch, wetter further south. More will fall on Thursday. In terms of temps, undercut MOS by several degrees on the highs - only showing 50s areawide with overcast skies and rain ahead of the warm front. Also left lows falling maybe a couple degrees from daytime highs with the best push of warm advection overnight and continued clouds/rain. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 310 PM EST Sunday... Though there are still some rather significant details to pin down mostly on the mesoscale, confidence continues to increase that Thursday and part of Friday should be an active period of weather. In mid-levels a powerful southern-stream trough phases with northern- stream energy, evolving into a closed off upper low Thursday that makes slow east progress. Initial surface low in the central Plains Wednesday night moves northward and looks to occlude, while a secondary low then develops along the warm front in the Tennessee Valley and moves northeast across the central Appalachians into New England Thursday-Thursday night. This should bring warm sector rains to the region on Thursday, infused by PWAT values between 1.25-1.5". Depending on how quickly we can get into the warm sector will determine if thunder is possible for parts of or all of the region Thursday, but there is strong diffluence aloft indicated in the global models as well as rather strong vertical wind shear. Since it`ll likely be raining Wednesday into Thursday, did take a look at the MMEFS for some of our river gages, and based on NAEFS and GEFS QPF input they do show some conditional rises on some of the rivers between Thursday and Friday. Northwest winds also appear to become at least quite breezy Thursday night into Friday. 12z MEX-based MOS wind speeds for many of our MOS forecast points are between 30 and 38 knots, a pretty impressive signal considering it is still Day- 5/Day-6. Did raise wind speeds up Thursday night-Friday based on those MOS signals and favorable pressure rises. Nonetheless, will need to continue to carefully monitor the late-week period. Temperatures will also begin to cool towards more seasonal levels Friday into the weekend. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... As of 630 PM EST Monday... Cold front continue moving southeast this evening becoming stalled near the Virginia/ North Carolina border tonight. Scattered light MVFR showers are possible along the front but overall conditions remained VFR. Rain fill back in over southern Virginia and northern North Carolina tonight, mainly after 03Z/10PM as a low tracks along the front. High confidence of widespread MVFR to IFR ceilings in the foothills and mountains after midnight. Winds turn to the northwest and north behind the front. Lower confidence how extensive fog will be tonight and Monday morning. Expecting MVFR fog where there is rain. MVFR to IFR conditions will continue for Monday morning. Light northerly winds are expected for Monday. Confidence is medium on cigs/vsbys/winds through the fcst pd. Extended: Sub-VFR conditions may extend through Monday night as the front sinks south. High pressure builds over the region into Tuesday which should bring drier conditions and VFR, at least temporarily. By late Wednesday into Thursday rain and MVFR to IFR ceilings will return to the region. A strong cold front crosses the region Thursday night with much colder air and strong gusty winds behind the front Thursday night and Friday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS/KK SHORT TERM...AL LONG TERM...AL AVIATION...AMS/KK
Area Forecast Discussion
National Weather Service Shreveport LA
926 PM CST Sun Feb 25 2018 .UPDATE... Strong positively tilted upper level trough axis is currently residing across Eastern Kansas and pulling out of the OK/TX Pnhdl region of the country late this evening. Lift in association with this trough axis is confined to our southern and eastern zones, in association with the large rain shield across these same locations. The back edge of this rain shield continues to make slow but steady progress eastward across the Lower Toledo Bend Country of Deep East Texas into portions of Central and Northeast Louisiana. Extrapolating the eastward progression of this rain shield over time puts the back edge of rain only across our extreme southeast parishes near or shortly after midnight. With drier mid level air rapidly infiltrating our region from the west with the arrival of the trough, have removed pops for the remainder of the night for all but our southeast third where pops are still categorical in nature. Satellite imagery via the GOES 16 Nighttime Microphysics Channel shows the clearing line of cloud cover trying to move further towards the Interstate 30 Corridor of Northeast Texas into Southwest Arkansas but I`m having my doubts about just how much further south and east the clearing line will make it. In fact, 00z progs have this cloud cover possibly beginning to retrograde back to the north and west overnight. Also getting a little concerned with the development of fog overnight across our southern and western most zones with the latest HRRR output showing this possibility the best. For this reason, have added fog to the grids across our southern and western most zones. Other changes included hourly temp/dewpoint and sky grids to mimic current and forecast hourly changes. Update out shortly...13. && .PREV DISCUSSION... /issued 616 PM CST Sun Feb 25 2018/ AVIATION... For the ArkLaTex, IFR for KLFK with MVFR/VFR everywhere else as a large area of showers extends from KLFK to near KELD and points SE. This area of showers will continue to move E this evening and should push E of KMLU by 06Z. Light NE winds will keep cigs/vsby issues IFR, but skies should lift and clear from NE to SE 12Z- 18Z. Climb winds are NE only to about 2kft and quickly veer to SE then SW by 4kft. Speeds increase from 20-80KT into flight levels. Outlook is for dry weather for Monday and half of Tuesday. /24/ && .PRELIMINARY POINT TEMPS/POPS... SHV 45 69 50 68 / 10 10 10 70 MLU 48 69 47 70 / 90 10 10 60 DEQ 41 68 43 64 / 10 0 10 60 TXK 43 68 46 65 / 10 10 10 70 ELD 43 69 44 67 / 10 10 10 60 TYR 49 70 50 67 / 10 10 10 70 GGG 47 70 50 67 / 10 10 10 70 LFK 51 72 54 72 / 20 10 10 70 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...None. LA...None. OK...None. TX...None. && $$ 24/13