Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/01/17

Area Forecast Discussion
National Weather Service Denver/Boulder CO
700 PM MST Tue Feb 28 2017 .UPDATE... Issued at 650 PM MST Tue Feb 28 2017 Area of snow is moving se across the plains in association with main upper level trough which should exit area by 04z or so. Some fog has developed behind this band of snow where skies have begin to clear. Latest hrrr breaks most of this up in the next few hours so we shall see if that is the case. Meanwhile a mtn wave is fcst to dvlp after midnight and continue through Wed morning. cross-sections from hi-res models show component alopng winds fm 45-55 kts late tonight thru Wed morning. There is some potential for high winds in the normal windy areas fm 09z-15z time period. At this point not sure how widespread it will be so will hold off on a warning for now but have increased winds in the mtns and foothills. && .SHORT TERM...(This evening through Wednesday) Issued at 230 PM MST Tue Feb 28 2017 The main snow band will be moving rapidly across the plains and Palmer Divide this afternoon, ending during the early evening. Have adjusted forecast for earlier ending time with this fast moving trof. Could see a quick inch of snow as the bands moves through. There is still some banded instability showers redeveloping off the foothills across Larimer and Weld counties but most of these will be gone by 7 pm. For the mountains will keep the winter weather advisory going through 5 pm for zone 34 given some improved orographic flow. The flow aloft will be increasing from the northwest overnight. Cross sections showing increase mountain top flow with gusts 40-60 mph possible over mountain passes and exposed east slopes. With the w-nw orographic flow will keep some snow showers going in the mountains. Moisture depth becomes more shallow so don`t see more than a few inches over higher mountains. Behind the trof, stronger nw winds will also develop over the northeast portions of Colorado. Dry and slightly warmer conditions expected on the plains for Wednesday. .LONG TERM...(Wednesday night through Tuesday) Issued at 230 PM MST Tue Feb 28 2017 Northwesterly flow aloft will continue Wednesday night into Thursday as a ridge builds into the southwestern states. Besides a slight chance of snow over the far northern mountains Wednesday night, the airmass will be drying and warming. Temperatures will still likely be slightly below normal for this time of year. The upper ridge will transition over the state Friday then flow aloft will turn southwesterly Saturday as the next system moves onshore over the western US coast. Temperatures will warm above normal readings under mostly clear skies. Readings in the mid 60s to low 70s will be found over the plains with mountains in the mid 30s to mid 40s. A warm, dry and breezy day is expected Sunday as the system nears, resulting in increased fire weather concerns for the plains. The Canadian continues to be the faster model with the system, bringing in precipitation into the area starting Saturday afternoon, whereas the GFS and EC keep it back until Sunday. Model trends have been showing the GFS and EC speeding up slightly, while the GEM is backing off considerably on speed. Will introduce a slight chance of snow for the northern mountains Saturday night after midnight. The trough should pass over the northern Rockies Sunday night with a cold front pushing through soon after. Moisture doesn`t look impressive yet with this system over the state with most of the energy staying north. For now will keep out any mention of precipitation for the plains. A ridge is expected to build back in Monday and Tuesday, a possible impressive one according to the EC. After a cooler Monday following the cold front will have warming and dry conditions for Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 650 PM MST Tue Feb 28 2017 Snow has moved off to the se. There is some potential for fog for the next few hours however as downslope low lvl flow wly develops believe threat should diminish after 04z. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...RPK SHORT TERM...Entrekin LONG TERM...Kriederman AVIATION...RPK
Area Forecast Discussion
National Weather Service Dodge City KS
520 PM CST Tue Feb 28 2017 .UPDATE... Issued at 520 PM CST Tue Feb 28 2017 Reduced pop grids, limiting mention of showers to slight chance through this evening, and even this may be optimistic. Radar is finally showing some light showers developing near Dighton and Hays. Much of this is virga, and latest HRRR runs are quite dry and pessimistic. Otherwise, NW winds will increase for several hours this evening, followed by clearing after midnight. && .SHORT TERM...(This evening through Wednesday) Issued at 216 PM CST Tue Feb 28 2017 A strong push of cold air is anticipated to move through western Kansas this afternoon into this evening bringing strong northerly winds overnight. A few showers may develop along and behind this front late this afternoon into this evening but should dissipate or move out of the area by midnight. Increased cloudiness is expected this evening with clearing after midnight. Mostly clear skies and dry conditions are in store for tomorrow with winds from the northwest. As for temperatures, lows tonight look to range from the lower 20s across west central Kansas to around freezing across south central Kansas. Highs tomorrow are progged to only reach into the low to mid 50s with upper 40s possible across portions of west central Kansas. .LONG TERM...(Wednesday night through Tuesday) Issued at 216 PM CST Tue Feb 28 2017 A dry weather pattern is expected to continue through the long term period with mostly clear to partly cloudy skies. Highs will start out in the 50s Thursday, reaching into the 70s by this weekend. Upper 60s to lower 70s are progged for the early part of next week. Low temperatures dip into the 20s Wednesday and Thursday nights, 30s Friday night, then upper 30s to 40s this weekend into the first part of next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 500 PM CST Tue Feb 28 2017 Expecting VFR through this TAF period. Broken midlevel clouds will persist into this evening. Areas of virga or maybe a sprinkle from these clouds, but kept any mention of precipitation out of the TAFs. A strong cold front will bring strong NW winds this evening, gusting 30-35 kts at times, before relaxing after 06z. After 15z Wed and the onset of excellent mixing, NW winds will increase sharply again at all airports, averaging 25-35 kts. NW winds will begin diminishing after 21z. SKC expected after midnight through Wednesday. && .PRELIMINARY POINT TEMPS/POPS... DDC 28 53 24 57 / 20 0 0 0 GCK 27 51 20 54 / 20 0 0 0 EHA 23 50 24 55 / 20 0 0 0 LBL 26 52 23 58 / 20 0 0 0 HYS 28 50 24 54 / 20 0 0 0 P28 33 56 26 60 / 10 0 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Turner SHORT TERM...Hovorka_42 LONG TERM...Hovorka_42 AVIATION...Turner
Area Forecast Discussion
National Weather Service Quad Cities IA IL
600 PM CST Tue Feb 28 2017 ...00z AVIATION UPDATE... .SYNOPSIS... Issued at 330 PM CST Tue Feb 28 2017 As of 2 PM...1000mb sfc low positioned between Des Moines and Cedar Rapids. To the SE, incredibly mild and moist late February air mass has overspread E Iowa/NW Illinois. Temps are between 65-70 F (dewpoints in the mid/upper 50s) along/south of highway 30. SPC Mesoanalysis displayed 1000-1500 MUCAPE and near 50 kt effective bulk shear over the forecast area, becoming largely sfc-based across SW half of the area. Storms are expected to pop up near or just east of the sfc low close to 3 PM, then spread ENE with time. && .SHORT TERM...(This Evening and tonight) ISSUED AT 330 PM CST Tue Feb 28 2017 Late Afternoon through this Evening: There is a risk for severe thunderstorms along/east of a Sigourney, IA to Galena, IL line. The greatest risk is along and SE of a Kahoka, MO to Geneseo, IL to far SE Whiteside Co. line where the Storm Prediction Center has an enhanced risk. The main threats are damaging winds around 60 mph and hail up to golf ball size. Tornadoes are also possible, especially with the strongest storms which will be supercells. Thunderstorms are forecast to remain scattered, therefore not every location will be impacted by strong or severe storms. Being the last day of February, the synoptic environment is anomalously warm and moist across E Iowa/NW Illinois. Sfc temps and dewpoints in the 60s and upper 50s (respectfully) will push instability into the 1000-2000 J/kg SBCAPE range. The forcing for ascent and shear needed to develop and sustain rotating storms/supercells are present in the form of an approaching sfc low riding along a warm front, and 50 kts of effective deep layer shear. Severe Storm Timing and Risk Areas: LCLs near 500 meters, low LFCs, 30 kts of 0-1 km shear, and SRH near 200 m2/s2 are key ingredients supportive of a tornado risk. One limiting factor, as displayed in forecast hodographs, is marginal directional shear in the lowest 1 km for counties west of the Quad Cities. Forecast storm motion per 850-300mb mean wind and forward propagating Corfidi vectors is WSW to ENE around 50-60 mph. In the counties along and east of the Mississippi R., sfc winds are nearly due south as of the early afternoon and may back to the SSE has convection forms NW of this area. Therefore, the central/east-central counties of the forecast area have the higher risk for tornadic supercells. This is where consecutive runs of the HRRR have been showing a few robust swaths of 2-5 km max updraft helicity from late afternoon supercells it`s developing. The greatest uncertainty with respect to storm coverage, or storms affecting portions of the CWA, is with the secondary round that forms along the cold front after 8-9 PM. The HRRR has consistently been congealing this line to the E/SE of the DVN CWA. Uttech .LONG TERM...(Wednesday Night through Tuesday) ISSUED AT 339 PM CST Tue Feb 28 2017 Wednesday...Upper trof acrs central IA, while main sfc low rolls northeastward acrs lower MI, will drive secondary def zone type precip band acrs the CWA Wed from west-to-east. Dynamical/top-down cooling to produce rain to wet snow switch over as morning progresses especially along and north of the HWY 20 corridor. But same processes to battle diurnal processes and lingering mild boundary layer for awhile, and main be a rain-snow mix or all rain on it`s south flank for awhile. But some signs of heavier snow/ dendritic bursts along and north of HWY 20 and will go with a wet inch to just under 2 inches of snow accum in those far northern areas by Wed evening when the precip pulls out to the east. Less than an inch from HWY 20 on down to HWY 30, with daytime melting and compacting on lingering mild ground temps eating away at true snow. Better snow accum potentail on elevated surfaces. Brisk northwesterly gradient winds of 15 to 25 MPH and gusts to 35 MPH, and highs in most areas in the upper 30s to lower 40s making for a raw day to welcome in March. The far south will make it into the mid 40s with some breaks in the cloud cover. Cool night in the 20s into Thu morning. Thursday and Friday...a weak clipper for a wintry mix of light precip on Thu under broad northwesterlies. then a more organized system utilizing return flow convergence for another mixed precip event Fri night. Saturday and Sunday...Upstream thermal ridge still on track to build east acrs the region over the weekend, with highs in the 50s to low 60s on Sat, warming into the mid to upper 60s on Sunday except north of HWY 30 where it looks cooler. mainly dry until possible light rain system late Sunday into Sunday night. Next Monday and Tuesday...Latest medium range models roll out a large cyclone acrs the Midwest this period, with mild weather and showers/some storms possible on it`s mild side late Mon into Mon night. Cooler with rain possibly changing to snow in the north on Tue. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening) ISSUED AT 547 PM CST Tue Feb 28 2017 Widely scattered to isolated storms acrs the area will decrease or move out of the VCNTY of most of the TAF sites by 03z this evening, with VFR CIGs in between. Then a frontal passage will switch winds to the northwest and increase, but some risk of lowering MVFR cigs behind the front with embedded rain. Convergent bands of wind may also produce areas of MVFR fog despite northwest winds into early Wed morning. Then rain becoming mixed with wet snow from west to east at CID and DBQ(possibly MLI as well) from mid morning into mid afternoon. Strong northwest sfc winds gusting up to 30 KTs for much of the day, and may reduce VSBYs to temporary IFR levels in the falling snow or rain/snow mix bands from late morning into early afternoon. ..12.. && .HYDROLOGY... Issued at 330 PM CST Tue Feb 28 2017 Many area rivers continue to be on the rise due to recent rainfall locally, and routed water from upstream due to both rainfall and snow melt to the north. Additional rainfall amounts from this afternoon through tomorrow morning will range from around a quarter inch, to over three quarters of an inch. The higher amounts will occur under the thunderstorms and be localized. Taking this all into account and the routed water coming from upstream, with somewhat higher confidence have upgraded the river flood watches to warnings for the Mississippi sites at Rock Island, Muscatine, New Boston, and Keithsburg. Additionally, have upgraded Gladstone and Burlington to Major flood stage by early next week. These southern sites river levels become enhanced from flow input/contribution from the Iowa/Cedar Rivers. Have gone with a river flood watch for Fulton and IL City on the Mississippi with lower confidence that they may just reach flood stage or fall just short late in the coming weekend. As for the tributaries, confidence is high enough in the routed water from upstream along with some rainfall tonight, to upgrade the Wapsipinicon River near De Witt to a flood warning. Forecast has it falling just short of moderate flood stage later Thu night, and will have to watch trends of a possible higher crest getting into the moderate category. Rises near or above action stage still expected on portions of the Iowa and Cedar Rivers, with Conesville on the Cedar cresting now above flood stage. Projected rainfall through Wednesday morning may push both Joslin and Moline on the Rock River above action stage Fri into Sat. ..12.. && .CLIMATE... ISSUED AT 330 PM CST Tue Feb 28 2017 Record Highs for today February 28... Moline.........66 in 2016 Cedar Rapids...64 in 1932 Dubuque........62 in 1895 Burlington.....69 in 1932 && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...Uttech SHORT TERM...Uttech LONG TERM...12 AVIATION...12 HYDROLOGY...12 CLIMATE...Uttech
Please see the 00Z aviation forecast discussion below.

AVIATION... VFR conditions will continue through this evening at area TAF sites. We do expect low clouds to redevelop after midnight and will continue to mention MVFR cigs along I-35 beginning 08-09Z. We will see a steady stream of mid and high level moisture overnight and this may disrupt the onset of low clouds. For now, we will stick with the above timing and continue to monitor. Attention will then turn to a cold front set to move through early tomorrow morning. First, a dryline/weak Pacific front will shift winds to a more northwesterly direction at DRT around 06Z, with the I-35 sites becoming west/northwest around 09-10Z. Winds will then increase around 15-16Z at all TAF sites as a surge of high pressure moves into the region. Winds will likely remain gusty through tomorrow afternoon, then begin to diminish around 02/00Z. PREV DISCUSSION... /ISSUED 301 PM CST Tue Feb 28 2017/ SHORT TERM (Tonight through Wednesday)... A mostly dry cold front will shift through the area overnight and early Wednesday morning with only light showers at best along it. Northwest winds and drier air will filter into the region through the afternoon with only high passing clouds remaining. RAP analysis coupled with water vapor imagery channels clearly depicts a longwave trough axis over the Rockies and into the desert southwest. A sharp moisture gradient exists between San Antonio northwestward to San Angelo where dewpoints are in the upper 60s to lower 40s, respectively. As the passage of the trough axis occurs over the next 18 hours, stronger northward momentum will bring the drier and slightly cooler airmass into South-Central Texas. With the strongest forcing well north and nearly parallel mid-level flow, dynamic support will be lacking with the frontal passage early Wednesday morning. Light showers to sprinkles may be all that is mustered (if even that much) along the front as it passes through. Patchy areas of fog could be possible ahead of the front from 4am-9am before it moves through. Low clouds will clear through the late morning with only high passing cirrus remaining intact through the overnight and Thursday morning with continued brisk zonal to weakly SW flow in the mid-levels. LONG TERM (Thursday through Tuesday)... Coldest mornings in a while will occur Thursday and Friday with a few mid and upper 30s in the Hill Country. Rain chances increase going into the weekend as a slow moving and weakening mid- and upper-level system shift over the region. Much drier air will shift into the region by late Wednesday and Thursday morning as dewpoints drop into the upper teens and low 20s. Thankfully, the continued brisk H5-H3 flow over the region will allow for cirrus cloud generation that should help blanket the region and keep low temperatures from fully bottoming out. A few pockets in the Hill Country could still reach down into the mid and upper 30s but no freezing temperatures are currently expected at this time. Thursday highs will be 10 degrees cooler than today. This will bring us to below normal lows but near average highs. By late week, a cut-off mid and upper-level low is expected to shift across west Mexico and slowly move towards central and south Texas over the weekend. Moisture return will start Friday as mid- and upper-level lifting support remains farther west. Best rain and isolated thunderstorm chances remain on Saturday and Sunday as either an ejecting shortwave of energy or the weakening parent low shift over the region. The best moisture availability vs. the strongest forcing does not appear to line up well. Strongest lift looks to occur Saturday but the best moisture return wont occur all the way till Sunday when the forcing is weaker. All told, have a persistent 30-50% rain and thunderstorm chance Saturday through Sunday for central and eastern locations. While isolated pockets of heavy rain may occur on Sunday towards the coastal plains with the deeper moisture, hazardous conditions do not look likely at this time. Models continue to be in poor agreement beyond the weekend and a blend with higher GFS weighting was used for days 6 and 7 forecast. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 62 73 45 67 44 / 10 10 0 0 0 Austin Bergstrom Intl Airport 61 73 43 67 42 / 10 10 0 0 0 New Braunfels Muni Airport 62 75 44 67 44 / 10 10 0 0 - Burnet Muni Airport 55 68 39 63 39 / 10 10 0 0 0 Del Rio Intl Airport 56 78 45 69 45 / - - 0 0 0 Georgetown Muni Airport 58 69 41 65 41 / 10 10 0 0 0 Hondo Muni Airport 59 79 42 69 44 / 10 10 0 0 0 San Marcos Muni Airport 61 74 43 67 43 / 10 10 0 0 - La Grange - Fayette Regional 66 75 43 67 44 / 10 10 0 0 - San Antonio Intl Airport 62 77 45 68 46 / 10 10 0 0 - Stinson Muni Airport 63 78 46 68 47 / 10 10 0 0 - && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Mesoscale/Aviation...24 Synoptic/Grids...LH Public Service/Data Collection...Treadway
Area Forecast Discussion
National Weather Service Grand Forks ND
641 PM CST Tue Feb 28 2017 .UPDATE... Issued at 641 PM CST Tue Feb 28 2017 Only minor tweaks needed with this update, mainly to cloud cover as an area of clearing from roughly Fargo to Fosston to International Falls/Baudette is taking a bit longer to fill in than previously forecast. Other than that, things are in good shape with the first wave of precipitation this evening staying just south and east of the forecast area. As for the next wave late this evening/overnight, timing still looks good for it to begin impacting the far northwest/Devils Lake basin by midnight. Will keep an eye on the latest hi-res guidance as the evening goes on and make any tweaks with later updates. && .SHORT TERM...(This evening through Wednesday) Issued at 231 PM CST Tue Feb 28 2017 Primary concerns for the long term period will be overnight lows and chances for snow in the extreme southeast this evening as well as light snow associated with an upper wave entering the northwestern zones aft midnight. High res models continue to show a band of snow redeveloping across SW MN into NE SD in the late aftn into early evening hours. ECMWF shows a Q-vector maxima push across this region, south of my CWA, in the 00Z to 06Z timeframe...however, both the latest RUC and HRRR keep the band out of the CWA although some very low QPFs do clip SE Otter Tail. Plan on keeping a dry forecast in this region. A weaker wave and associated Q-vector convergence maxima then moves into the Devils Lake region after midnight. RUC/HRRR modeled QPF not impressive with associated precip as it enters NW zones in the 07Z to 09Z timeframe. Will keep highest POPs over the northwest prior to 12Z and more broad spread POPs during the tomorrow period...although QPFs will be negligible in the 12Z to 18Z period. Most snow accumulation expected to be vicinity of DVL. Overnight lows will range from the single digits in the northwest to around 20 in the far southeast. Tomorrow`s highs will range from upper teens northwest to upper 20s in the far southeast. .LONG TERM...(Wednesday night through Tuesday) Issued at 231 PM CST Tue Feb 28 2017 Region initially in NW flow aloft with jet streak dropping through the central Dakotas Wednesday night into Thursday. Associated surface low will drop just to the west of the forecast area. While there is some f-gen forcing on east side of surface low track moisture looks limited with precipitable H20 values less than two tenths of an inch. This should limit snowfall amounts to the far sw fa to a few inches or less at this time. Heights begin rising towards the end of the work week as upper ridging shifts east. Temperatures will respond rising well above average for the weekend. precipitation chances look minimal through this period. The next decent chance for precipitation will be late Sunday into monday with the passage of clipper type system and cold front. Temperatures look closer to average to start the upcoming work week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 641 PM CST Tue Feb 28 2017 VFR conditions to continue initially but gradually lower to MVFR by the second half of the period. Scattered clouds will quickly give way to some high ceilings this evening but should remain VFR, for now. An upper wave will spread an area of light snow into KDVL by 08z and shift eastward through Wednesday morning. Therefore, have included some -SN at KDVL to account for this but left out of the other TAF sites for now as hi-res models do indicate the strength of this area of precipitation weakening as it moves eastward. North winds at 5-10 kts will back slightly to the northwest on Wednesday and increase to 10-15 kts along with MVFR ceilings moving in behind the upper wave and associated area of snowfall. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Lee SHORT TERM...Speicher LONG TERM...Voelker AVIATION...Lee
Area Forecast Discussion
National Weather Service Sioux Falls SD
539 PM CST Tue Feb 28 2017 .SHORT TERM...(This evening through Wednesday) Issued at 301 PM CST Tue Feb 28 2017 The primary concern in the next 24 h is the chance for snow tonight and Wednesday morning. Models are generally in agreement on the overall evolution of the large scale tonight. Later this afternoon and evening a southern stream jet will move from Kansas toward Missouri and Illinois placing the left exit region of the jet across northern Missouri and southern Iowa where a strong warm front is in place. Later this evening, a wave and associated northern stream jet will move into the Dakotas and northern Minnesota. This will put the right entrance region of this jet across eastern South Dakota and southwestern Minnesota. There is a 700 mb thermal gradient also in place although it lacks strong convergence. The NAM, GFS and ECMWF all generally depict convection developing near the surface boundary this afternoon and overnight with light snow developing after sunset across southwestern Minnesota and into northwestern Iowa with a 1 to 2 inches possible along and east of the Buffalo Ridge in Minnesota. However, the RAP and HRRR are much less sold on precipitation developing with the northern stream system. We hypothesize that the model development of convection acts to divert mid level moisture east of the area and limiting the amount of available moisture for snow north of Highway 20 with the northern stream system. Have generally favored this solution with the idea that only areas of light snow will develop tonight with many areas only seeing a dusting to half inch. The best chance for accumulating snow will be east of the Buffalo Ridge where perhaps an inch of snow could fall by Wednesday morning. Otherwise, this jet streak and wave will keep clouds overhead well into tonight. Expect that as the wave begins to move east of the area on Wednesday morning, skies will gradually clear out. There may be some cumulus development on the behind the clouds as the atmosphere is expected to be well mixed. Did consider adding in the chance for an afternoon sprinkle or shower but at this point expect that the cu will not have sufficient depth to get rain or snow to develop. Highs tomorrow will range from the mid 30s near Highway 14 to around 40 in the Missouri Valley. .LONG TERM...(Wednesday night through Tuesday) Issued at 301 PM CST Tue Feb 28 2017 For the long term forecast, the primary impacts will be a chance of snow late Wednesday night and Thursday and then much warmer weather for the weekend. An Alberta Clipper will move southeast across South Dakota and into Iowa on Wednesday night and Thursday. All models show 850 mb frontogenesis in the vicinity of the Minnesota river as the PV anomaly moves southeast across Minnesota. Based upon that, have sided closer to a GFS/ECMWF solution which basically has light snowfall from northeast South Dakota into north central Iowa. This puts southwestern Minnesota on the southern edge of any snowfall. For this reason have kept PoPs generally less than 30 percent with the expectation that most snow will remain closer to the Minnesota River. What is more certain is that after the the wave moves by strong northwest winds will develop first in the Missouri Valley and then gradually move east over much of southeastern South Dakota and northwestern Iowa. Sustained winds of 20-30 mph seem likely in the Missouri Valley with gusts of at least 35 mph. This wave will also bring colder air southward and despite the deeper mixing - highs will be cooler Thursday generally from around 30 in southwestern Minnesota to upper 30s in south central South Dakota. High pressure will move over Thursday night allowing temperatures to cool into the teens. Another wave will move through Friday bringing a warm front with it. This wave is really lacking moisture and its main impact will be to bring a lot of clouds and then much warmer air eastward. Despite more clouds on Friday, increasing southerly flow will bring warmer north with highs in the upper 30s to upper 40s. In the extended, Saturday - Tuesday, there is a lot of model agreement for the weekend as the GEFS, ECMWF and GFS all bring much warmer air over the area. The Canadian bring a cold front through on Saturday which is at least 24 h faster than any other deterministic model and it has been discarded for this forecast. On Saturday, very warm air will move north as winds turn south or even southwest. This will result in rather windy weather like Thursday but temperatures will be 20 degrees warmer with highs in the 50s to lower 60s. Sunday will have less wind but should be event warmer. Currently have highs from the upper 50s to mid 60s but 70 degree is possible as far north as I-90. After Sunday both the ECMWF and GFS bring a front through but the amount of cold air varies with the GFS much colder than the ECMWF. It looks to be cooler than the weekend but still above normal. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 528 PM CST Tue Feb 28 2017 The main concern continues to be low ceilings. MVFR and occasional IFR conditions is expected at all sites through most of the TAF period. A few flurries or very light snow is possible across KFSD and KSUX sites in the overnight hours; but highest snow amounts will fall across southwest Minnesota and northwest Iowa. Gradual improvement in ceilings is expected by Wednesday during the afternoon hours. Strong northwesterly winds of 15 to 20 knots, gusting to 30 knots will be prevailing by late morning through around sunset. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ SHORT TERM...Schumacher LONG TERM...Schumacher AVIATION...Dux/05
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
830 PM CST Tue Feb 28 2017 .UPDATE... Some adjustments to tonight`s convective trends were in order per latest high-resolution guidance of the HRRR, TTU WRF, NAM12, and WRF East models. Latest 01Z LAPS soundings were indicating a strengthening EML south of I-20/I-30 corridors, with lesser inhibition further north, especially north of HWY 380 and particularly the immediate Red River counties. High-res models are much drier than the standard synoptic models, especially across Central TX. I have adjusted for lower chances of initiation from near Decatur to Gainesville just before midnight, as the triple point of the dryline and approaching strong cold front arrive in tandem with stronger large-scale ascent. The HRRR seems to be most aggressive here, but has been consistent with its forecast the past several hours. Looking at thermodynamic analysis, it looks quite reasonable. TTU WRF keeps most discrete activity north of the Red River and toward the Ozarks. If a few storms do develop as the HRRR suggests, then 0-6km bulk shear near 50 knots, strong but veered 15-20 knot 0-1km shear, and very steep lapse rates all suggest storms growing upscale very quickly to strong and severe levels. We`ll be monitoring trends closely as we approach midnight. Main threats appear to be large hail to ping pong ball size and potentially damaging winds if storms can get rooted into the boundary layer. The severe threat will likely shift east of our NE counties by 3-4 am CST with a few showers and elevated, non-severe storms potentially lingering across our southern counties along and east of I-45 with the strong cold front. 05/ && .AVIATION... /ISSUED 704 PM CST Tue Feb 28 2017/ /00Z TAFs/ VFR conditions will prevail. Shift to north flow early Wednesday. Low clouds are now confined to areas east of the I-35 corridor. Although winds near the top of the boundary layer may approach 50 knots later this evening, veering flow should focus much of the moist advection and any MVFR ceilings into East Texas. The 00Z RAOB from Fort Worth shows a capping inversion remains around 850mb, preventing the 1000-1500 J/kg of MLCAPE from being realized. Forcing for ascent will spread across the region this evening, but this will occur as the boundary layer cools. However, as a cold front approaches the Red River around midnight, it may impart sufficient lift for thunderstorms to develop. This activity would potentially impact the Bonham cornerpost, but storms are unlikely to affect Metroplex TAF sites. Any storms would race eastward, and surface winds will veer during the predawn hours. The cold front will arrive before daybreak, and north flow will prevail Wednesday and Wednesday night. 25 && .PREV DISCUSSION... /ISSUED 346 PM CST Tue Feb 28 2017/ A strong capping inversion has held across the region today. The dry line has moved just to east of a Wichita Falls to Junction line as of 3 PM while a cold front extended from northwestern Missouri to southeastern Colorado. We will likely need the cold front and an approaching shortwave to weaken the cap sufficiently for surface based storms tonight. Have kept a 20-30 percent POPs in for areas along and northeast of a Bowie to Palestine line through this evening and 20-30 percent POPs overnight along and east of a Sherman to Lampasas line. With steep lapse rates and strong shear, if the cap were to break, some severe storms would be possible. The cold front will move into the Graham to Bowie areas shortly after midnight and sweep rapidly southeast through all but the southeastern-most zones by daybreak Wednesday. Winds will shift to the west at 10 to 15 mph as the front approaches and then become northwest to north at 15 to 20 mph and some higher gusts with frontal passage. Lows tonight will range from the mid 40s northwest to lower 60s southeast. Winds will be north at 15 to 20 mph Wednesday with some gusts over 25 mph. The combination of the winds and relative humidities in the upper teens to mid 20s, elevated to critical fire weather conditions are expected mainly along and west of the Interstate 35 corridor. Dry weather is expected across the North and Central Texas Wednesday through Friday. Temperatures will be cooler but will be near or slightly above normal through this period except for Wednesday night. Lows Wednesday night will be mostly in the 30s...except near 40 southeast. Southerly winds will return Friday. As a surface trough deepens to our west, expect gusty southerly winds Saturday to advect gulf moisture northward. Low rain chances will start to return by Saturday afternoon and continue Saturday night through Sunday night. A chance of showers and thunderstorms will continue through Tuesday until a cold front pushes through and brings in drier air. 58 && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 53 65 38 64 41 / 10 5 0 0 0 Waco 53 67 36 65 37 / 10 10 0 0 0 Paris 52 63 35 63 39 / 40 10 0 0 0 Denton 49 63 33 64 37 / 20 5 0 0 0 McKinney 52 65 35 64 38 / 20 5 0 0 0 Dallas 52 65 40 65 42 / 20 5 0 0 0 Terrell 54 66 37 64 38 / 20 10 0 0 0 Corsicana 56 68 39 65 40 / 20 10 0 0 0 Temple 55 68 37 65 37 / 10 10 0 0 0 Mineral Wells 49 64 32 65 36 / 5 5 0 0 0 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 25/05
Area Forecast Discussion
National Weather Service Goodland KS
518 PM MST Tue Feb 28 2017 .SHORT TERM...(This evening through Wednesday) Issued at 302 PM MST Tue Feb 28 2017 A lot radar returns most of the day across the far north and northwest portion of the area. Just in the last hour or two, precipitation from those returns is finally reaching the reaching the ground. The Hrrr and Rap are catching reality the best. Basically this means the eastern end of the precipitation dissipates while the western end, roughly along and especially west of the Colorado border will have the best chance of precipitation. Mostly further west, it has or soon will be changing to snow. While further east this precipitation will remain rain or become a rain snow mix. Most of the precipitation will end by or shortly after midnight with precipitation ending over Colorado last. Snowfall amounts look to stay below an inch. Temperatures will be cooler tomorrow with northwest winds of 15 to 30 mph with some gusts up to 35 mph. The affect of this on fire weather conditions will be discussed in that section below. .LONG TERM...(Wednesday night through Tuesday) Issued at 122 PM MST Tue Feb 28 2017 Very dry conditions will persist through the entire extended period, raising concerns for elevated or critical fire weather conditions each day (dependent on winds). Wednesday Night-Thursday: NW flow will still be in place and similar air mass (to Wed) will linger over our CWA, so seasonal temps should continue. Translating to 40s/near 50 for highs and teens to lower 20s for lows. Winds should be lighter as upper level jet transitions east, so RFW is not a consideration at this time (though lower RH could be possible in our south). Friday-Tuesday: Flow shifts to the west Friday then southwest this weekend, with an approaching upper level trough on Sunday night. This trough tracks north with main axis of forcing, and a deep dry air mass in place will keep conditions dry despite increasing lift. Temperatures will be above normal through these periods, with Saturday and Sunday particularly warm. Based on similar warm ups and bias corrections we may see highs approach 80F for some locations. A cold front moves through the region by Monday, but the temps will still be above 60F, and unfortunately this only acts to increase winds an likely result in critical fire weather conditions due to the projected low RH values Monday afternoon. Large scale ridging (ECMWF) or westerly flow (GFS) builds over the western US by Tuesday, and we would see an upward trend in temps again. Despite differences in extended guidance dry and above normal are the answer. I trended temps up from standard blend Sat, Sun, and Tue due to the cool bias of 2m guidance and blend performance during pas warm ups. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 422 PM MST Tue Feb 28 2017 Conditions will remain VFR at GLD through the TAF period with clouds dissipating and skies becoming mostly clear after 09Z. LLWS is possible between 09Z and 13Z as surface winds slacken and winds aloft remain around 40kts. Conditions at MCK will remain VFR through the TAF period with skiesbecoming mostly clear after 09Z. Gusty northwest winds will continue at MCK and GLD for another couple of hours as colder air and areas of light snow move into the central high plains region before mostly dissipating by 06Z. Northwest winds will continue through the night and will become gusty again after about 13Z and will continue to be gusty through the day on Wednesday. && .FIRE WEATHER... Issued at 302 PM MST Tue Feb 28 2017 For Wednesday...much of the southern half of the area will be near 20 percent to a little below that. The lowest relative humidities will be roughly along and south of a line from Wild Horse to Russell Springs to Gove. Winds look to mix down from just under 700 mb. The strongest winds will transition to over the eastern half of this area in the afternoon. After sifting through the data and collaboration it was decided to not issue a Fire Weather Watch. The wording in the HWO was ramped some to be able to communicate these conditions. The overnight shift will need to take another close look at this. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...BULLER LONG TERM...DR AVIATION...LOCKHART FIRE WEATHER...BULLER
Area Forecast Discussion
National Weather Service Green Bay WI
531 PM CST Tue Feb 28 2017 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Wednesday Issued at 240 PM CST Tue Feb 28 2017 The latest rap analysis and satellite/radar imagery show an area of low pressure moving east-northeast over Iowa and a warm front extending east across southern Wisconsin. Showers and thunderstorms developed north of the warm front earlier today and grazed east- central WI. These storms have passed on to the east. Very little precipitation upstream, though some light precip is trying to get going over northeast Iowa. Meanwhile, a cold front is dropping southeast over far northwest Wisconsin and is producing a band of light rain. This band may just clip Vilas county later this afternoon. Fog also been an issue today, with visibilities dropping to a quarter mile or less at times. Looking at area webcams, the fog does not appear to be that hazardous though, so will continue to provide updates using the sps. Finally the next storm system is moving across the Rockies. Complicated weather will impact the region through Wednesday, and forecast concerns revolve around fog through this evening, then snowfall potential late tonight into Wednesday. Tonight...A shortwave trough will intensify as it moves across the Plains while a wave of low pressure travels northeast along the cold front across northern Illinois and lower Michigan. The strongest forcing this evening will reside south of our area closer to the wave of low pressure, but upper divergence will remain overhead which will keep a chance of light precipitation in the forecast. Think chances of precipitation will improve overnight as the shortwave from the Plains draws closer and mid-level fgen increases. Northeast to north winds will gradually draw in colder air through the night, with any precip gradually changing over from a rain snow mix or all rain over to snow from northwest to southeast. Minor accumulations are possible by daybreak mainly west of the lakeshore. In terms of dense fog, should see improvements with the visibilities as northerly winds strengthen and draw in colder/drier air this evening. Will keep a mention of dense fog through midnight across across the east. Wednesday...The snowfall is expected to intensify early in the morning as the deformation zone of a potent shortwave slides into the state. With ample moisture and lift, numerical models have increased precip over parts of central and most of eastern Wisconsin for the morning before precip exits by late in the afternoon. Of particular concern is the possibility of intensifying snows during the morning commute. Snows should peak from about mid-morning through early afternoon before trailing off from northwest to southeast. Increased snow amounts into the 3-5 inch range south of a line from Marshfield to the tip of the Door, which places this area solidly into the advisory range. Some blowing and drifting is possible west of the Fox Valley and Bayshore where where snowfall will be more of a normal type of snow, but the snow should be more of a heavy variety over eastern WI, which should limit the blowing and drifting. Temps will remain relatively steady and range from the lower 20s north to near 30 in the south. .LONG TERM...Wednesday Night Through Tuesday Issued at 240 PM CST Tue Feb 28 2017 Active weather leaves the region Wednesday night into Thursday morning with predominantly northwesterly flow. A couple of shortwaves will ride through the region ahead of an upper level ridge, which could bring in a chance for some snow showers Thursday night and Friday morning. Models differ on the overall chances as the GFS and NAM bring in a brief round of snow showers and the ECMWF remains drier. Differences primarily seem to stem from the amount of available moisture and the amount of dry air at low levels, so lower pops were preferred through the period with only trace to minor accumulations of snow across the area. The upper level ridge will then keep the area drier through most of Friday and Saturday. The only brief chance of snow showers arrives Friday night as another weak shortwave, coupled with low to mid level warm air advection, moves through the region on the backside of the ridge. Snow chances will remain slight once again, as models differ on the amount of low level saturation and warmth, which may keep the area dry. A more zonal flow pattern then establishes itself on Sunday ahead of the next clipper system expected to head towards the region. Current model runs show warm air advection strong enough to ensure that precipitation with this system will fall as rain. Winds could be quite gusty behind this system but this far out the exact path of the system will strongly effect both the wind strength and the precipitation type and chances. && .AVIATION...for 00Z TAF Issuance Issued at 530 PM CST Tue Feb 28 2017 Very poor flight conditions continue across the entire area. There will be some improvement this evening to MVFR as northeast winds increase, however IFR conditions are expected to return late tonight and into Wednesday as a shortwave brings a round of snow to the area. The heaviest snow will be across central and east- central Wisconsin where several inches will fall. conditions will improve through the day on Wednesday from northwest to southeast as the system moves away from the region. && .GRB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 4 AM to 6 PM CST Wednesday for WIZ022-031-035>040-045-048>050-074. && $$ SHORT TERM.....MPC LONG TERM......Uhlmann AVIATION.......Kurimski
Area Forecast Discussion
National Weather Service Huntsville AL
923 PM CST Tue Feb 28 2017 .NEAR TERM...(Rest of tonight) Issued at 923 PM CST Tue Feb 28 2017 Currently it`s dry across the area with low clouds starting to filter in beneath a batch of cirrus. Temps did drop over the last few hours but have warmed back up with current temps in the lower to middle 60s. These should generally stay steady for the rest of the night. We have continued to monitor the evolution of the storms for the overnight and morning hours. It looks like we will stay dry at least through midnight and maybe even slightly later and have updated the POPs accordingly. As we approach 6AM, showers and thunderstorms may be approaching NW AL ahead of the approaching cold front. The environment will have plenty of moisture, decent instability and plenty of wind shear aided by a strong southwesterly low level jet. If storms do form, damaging winds, large hail and tornadoes are all possible. The confidence in the coverage of this is not as high as the previous forecast so have kept the wording at scattered coverage through 6AM. The timing is also slightly uncertain with the hires guidance slightly quicker than the GFS/ECMWF/NAM. With the strong LLJ, we feel a slightly quicker solution is valid. This moves the timing of the storms in NW AL to around 6-9AM. .SHORT TERM...(Wednesday through Thursday) Updated at 923 PM CST Tue Feb 28 2017 As mentioned above, the best timing for the discrete cells ahead of the front looks to be around 6-9AM. After analyzing new model runs on the evening shift, we updated the timing section below to reflect the newest thinking. Then, as the cold front associated with this trough shifts east, the environment is expected to recover from the earlier morning activity out west due to a very strong LLJ and cooling mid-levels as the TN Valley becomes positioned underneath the RR quadrant of the upper level jet streak. A QLCS will develop ahead of this front and rapidly shift east/southeast. For the arrival of this QLCS, anticipating the following: 1) surface dewpoints in the low to mid 60s, 2) a gradual transition to a more linear wind shear profile but still high with between 50-70 kts of deep layer shear, and 300-400 m2/s2 low-level helicity. 3) surface based CAPEs between 500-1500 J/kg (elevated earlier, but cooler lapse rates aloft later). GFS ensembles have shown an upward trend in surface based CAPE especially in the afternoon. 4) SHERBS3 values between 1-1.5. All of these parameters along with some others not mentioned point towards a damaging winds up to 70 MPH and large hail threats with the QLCS that would be moving across the region. QLCS tornadoes may also occur around LEWPs, bookend vortices, and line breaks. The current timing of this QLCS (subject to change based on its upstream evolution): 1) has it arriving across NW AL (just after of with the merging of discrete cells with the line) by 9AM-11PM. 2) north central/I-65 corridor: by 11AM-2PM. 3) northeastern Alabama: 2PM-4PM. Outside of the severe threat, winds will be quite breezy with sustained winds of 15-20 MPH with gusts up to 35 MPH and may need a wind advisory during the day for this. Once the QLCS exits the region, a very rapid cooldown is expected across the TN Valley as the cold front moves southeast. Overnight lows are expected to be much lower in the upper 30s. The daytime highs should rise closer to seasonable on the mid to upper 50s. .LONG TERM...(Thursday night through Monday) Issued at 306 PM CST Tue Feb 28 2017 Amplified flow pattern will persist into the extended period across the lower 48. On Friday, a broad surface high will build briefly across the Tennessee Valley. Given its modified Pacific origins temperatures will remain near climo levels. With the surface high moving quickly to the east, expect a decent warmup for Saturday into Sunday. Expect some increasing clouds during the day on Sunday as strong warm air advection pattern takes shape. Models have trended a touch slower with the next system progged to impact the region Monday into Tuesday. The GFS/GEFS solution is about 12 hours slower than the ECMWF and have taken a middle of the road approach for this model cycle. Depending on the evolution of this system, we may have to monitor the Monday/early Tuesday time frame for potential active weather but it`s still a long ways off with much uncertainty. Trended toward the cooler ended of guidance for Tuesday night. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 510 PM CST Tue Feb 28 2017 Another tricky TAF forecast through the next 24 hours. CIGS may raise temporarily in the next few hours but should quickly fall back to IFR after midnight. Uncertainty still exists on the timing of thunderstorms for Wednesday. There could be a round in the morning but likely that will only impact KMSL and have added an earlier TEMPO group for thunderstorms. Then the cold front comes through with another line of thunderstorms. These storms could be severe and produce damaging winds and large hail. Did not include any severe mention in the TAFs due to timing uncertainty. Winds will also be gusty with the cold front with gusts of 25-30kt with the front and shortly after. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...LN SHORT TERM...SL.77 LONG TERM...15 AVIATION...LN For more information please visit our website at
Area Forecast Discussion
National Weather Service Lincoln IL
845 PM CST Tue Feb 28 2017 .UPDATE... Issued at 844 PM CST Tue Feb 28 2017 A cluster of strong to severe thunderstorms is ongoing south of I-70...while additional cells are developing further west near the Mississippi River ahead of an approaching cold front. The storms across the SE KILX CWA will exit into Indiana over the next 1-2 hours. Meanwhile, the convection further west will congeal into a solid line across the Illinois River Valley...then push eastward across the region through the overnight hours. HRRR has been handling the convective evolution quite nicely over the past several hours, so will follow its solution closely for the immediate short-term. As expecting a line of strong to severe storms to reach the Illinois River by around 9-10pm...the I-55 corridor by 10pm-midnight...then further east to the Indiana border between midnight and 3am. Main severe weather threats will continue to be damaging wind gusts and isolated tornadoes as the line progresses eastward. Other than some minor hourly PoP/temp adjustments, think the current forecast is right on track at this time. && .SHORT TERM...(This evening through Wednesday) ISSUED AT 318 PM CST Tue Feb 28 2017 20z/2pm surface analysis shows 1000mb low over eastern Iowa, with warm front extending southeastward along/just north of the I-74 corridor. MUCAPE values have increased to 1000J/kg while 0-1km bulk shear has been enhanced to 30-35kt near the boundary. Based on these parameters, it appears convection will first initiate near the warm front across the northern KILX CWA within the next hour or two. While these first cells will quickly shift into northern Illinois, additional cells developing within the main instability/shear axis across southwest Illinois will lift into the area by early evening. Any storms that fire late this afternoon into the early evening will be capable of damaging wind gusts in excess of 60mph, large hail greater than quarter-sized, and a few tornadoes. The first round of scattered convection will be relatively short-lived, with the HRRR suggesting it exiting into northern Illinois/Indiana by 02z/8pm. After that, attention will focus further west ahead of an advancing cold front where a squall line will take shape. Models have been struggling with the timing of the late night convection: however, consensus is beginning to point to a slightly earlier solution than the 12z CAMS had initially suggested. Latest HRRR shows a line of storms arriving west of the Illinois River by 04z/10pm...then quickly pushing to the I-70 corridor by 08z/2am. Main threats with these storms will be damaging wind gusts...with the potential for a few tornadoes embedded within the line. Once the overnight line of storms pass, the threat for additional severe weather will come to an end. Windy and much cooler weather will be noted in the wake of the system on Wednesday. Westerly winds will gust to between 25 and 35 mph...while high temperatures only reach the upper 40s and lower 50s. .LONG TERM...(Wednesday night through Tuesday) ISSUED AT 318 PM CST Tue Feb 28 2017 500 mb trough axis to shift across central Illinois Wednesday evening with lingering low chance POPs across our far north and east. Broad cyclonic flow remains over our area on Thursday bringing a mix of clouds and sun along with more seasonably cold temperatures. Highs will be mostly in the 40s. High pressure is then forecast to build east into the region through the end of the week. With our area under a northwest flow, temperatures will remain closer to where they should be into Friday. Several weak, fast moving shortwaves will track southeast into the Midwest late Thursday and again late Friday into Friday night bringing low chance POPs mainly to the north. The upper low/trough shifts well off to our east late in the weekend into early next week allowing upper level ridging to build into the Midwest. This will result in a significant warming trend once again over the center of the nation. However, medium range models still showing a decent amount of spread with respect to our next upper wave forecast into the Northern Plains on Monday and then closing off a deep upper low over the Great Lakes Monday night into Tuesday at least according the the latest ECMWF, while the GFS is quite a bit slower with the evolution of the early week trough, just the opposite from what we saw 12 hours ago. Not a great deal of confidence with the forecast as we head into the second half of the weekend with POPs increasing ahead of the approaching shortwave, especially on Sunday and Monday of next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 603 PM CST Tue Feb 28 2017 Main aviation concern continues to be timing of potential line of strong to severe convection later this evening. High-res models have been consistently showing a broken line of storms developing across eastern Iowa/Missouri over the next couple of hours. Latest radar imagery is already showing the beginning of the line materializing, so confidence is growing concerning specific timing details. Have followed the HRRR solution closely and have therefore sped up the onset by 2-3 hours. Included a TEMPO group for thunder beginning at 04z at KPIA and ending at KCMI by 08z. Once the line passes, winds will veer to the W/SW...then eventually the W/NW. Outside of the storms, VFR ceilings will prevail until late tonight into Wednesday morning as MVFR ceilings spill into the area from the northwest. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Barnes SHORT TERM...Barnes LONG TERM...Smith AVIATION...Barnes
Area Forecast Discussion
National Weather Service Jackson MS
932 PM CST Tue Feb 28 2017 .UPDATE... Updated for evening discussion. && .DISCUSSION... No changes were made to forecast update this evening. Warm advection will once again keep temperatures balmy overnight-- lows only reaching in the mid to upper 60s. Another round of patchy fog in the early morning hours is expected down near Hattiesburg/south of I-84. The 02Z HRRR run still shows the frontal passage into our CWA in the early morning hours (roughly around 14Z for the NE Delta region). As the front progresses southeast, a narrow band of isolated storms becomes more developed before exiting our region in the late evening hours. /12/ Prior discussion below: Tonight and Tomorrow: An upper level trough centered over the Rocky Mountains this afternoon will move eastward through tomorrow, with the trough axis passing our forecast area by tomorrow afternoon. Meanwhile a deepening surface low moving from the Midwest toward the Great Lakes will bring a cold front through the forecast area. Timing for the cold front is to be in southeast Arkansas/northeast Louisiana by 9 AM Wednesday, to the Natchez Trace corridor by around Noon, and finally southeast of Meridian/Hattiesburg by around 7 to 8 PM. A few strong to severe thunderstorms will possibly develop ahead of this cold front early on Wednesday, but think most of this pre-frontal storm activity will be centered north of our forecast area into central Arkansas and northern Mississippi. Mid-level cap will limit storm development farther south. Main threat for any severe weather in our area will be as the front moves through and cap can be overcome with low level forcing. Guidance suggests around 700-1000 J/kg of MLCAPE will be possible just ahead of the cold front, with 50 to 60 kts of 0-6 km shear to help organize storm updrafts. Shear will be mostly parallel to the cold front orientation, so a linear storm mode will be favored. A QLCS with modest instability and decent deep layer shear will primarily pose a hail and damaging wind threat. Greatest low level wind shear should be focused north of our forecast area, but a tornado or two cannot be ruled out with 20 to 30 kts of 0-1 km shear across mainly northern portions of the forecast area. /NF/ Wednesday Night through Monday Night: The cold front will move to the east and south of the area buy early Wednesday evening, with a few showers possible in the southeast ending by mid evening. Strong high pressure ridging will build in overnight, and with strong cold air advection temperatures will fall into the upper 30s and low 40s. Surface high pressure will continue on Thursday with clear skies and highs in the low/mid 60s. The main concern will be the potential for at least some elevated fire weather concerns Thursday afternoon, as Rh`s fall into the upper 20 percent range. The winds will be breezy out of the north early, diminishing through the afternoon hours, as the surface high approaches the area. With the surface high moving over the area Thursday night the winds will become light, thus expect strong radiation cooling to occur. Lows will fall into the mid 30s for much of the area and we could see some patchy areas of frost early on Friday. The High will move across the area and eventually to the east of the area Friday night. Expect another nice day on Friday with highs in the low/mid 60s. With the flow becoming southeasterly on Saturday, highs will climb up to near 70 degrees under sunny skies. Southerly flow will continue on Sunday with increasing moisture and the potential for a few showers in the Southwest later in the day. The GFS/ECMWF diverge in there solution beyond Sunday, with the GFS indicating a more substantial upper ridge Sunday night into Monday, while the ECMWF drags a short wave across the area with showers and thunderstorms. The GFS is much slower with the upper system indicating an increase in shower/thunderstorm potential on Tuesday. Will just go with a blend and show and increase chance for showers/thunderstorms on Monday and Monday night. /15/ && .AVIATION... 00Z TAF discussion: Expect ceilings to lower later this evening in the continued southerly flow pattern...potentially to IFR category in the HBG to MEI area. As a cold front pushes through Wednesday, there will be a broken line of SHRA/TSRA accompanying the front pushing southeast through most sites by late afternoon. This will be followed by VFR conditions. /EC/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 67 77 42 64 / 18 71 11 3 Meridian 66 79 43 65 / 14 70 45 4 Vicksburg 68 76 42 64 / 25 62 8 3 Hattiesburg 67 82 44 66 / 14 59 30 4 Natchez 68 77 44 66 / 20 63 11 3 Greenville 67 73 40 63 / 46 72 7 2 Greenwood 67 74 40 62 / 32 72 7 2 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ 12
National Weather Service Jackson KY
1100 PM EST Tue Feb 28 2017 .UPDATE... Issued at 1100 PM EST TUE FEB 28 2017 Have adjusted the PoP and Wx grids through the rest of the night to incorporate radar trends and latest HRRR. It looks like the bulk of the area will be fairly PoP free through the night with the exception of locations north and west of the Mountain Parkway. Also tweaked near term temps and dewpoints for the latest obs and trends. These have been sent to the NDFD and web servers. A freshened set of zones will be issued, too. UPDATE Issued at 835 PM EST TUE FEB 28 2017 01z sfc analysis shows a deep area of low pressure moving into the Upper Midwest with a warm front well to the north of the area. This has placed east Kentucky in the warm sector of the larger system with very mild conditions under thick clouds, but most of the convection now off to the east and north with the front. To the northwest a large cluster of strong to severe storms is taking shape and the remains of this complex may affect northern parts of the area by dawn, possibly much sooner given the HRRR trends. The area with the best chance for strong to severe storms through the night remains locations north and west of Interstate 64 - closer to the slight risk outlined by SPC through 12z. This is also the locations with the biggest concern for excessive rains and a potential for flash flooding - where the flood watch is in effect through Wednesday afternoon. The rest of the area is covered by a marginal risk overnight with less of a concern for organized strong storms developing through dawn. Have updated the grids with the above thoughts in mind - lowering the PoPs through the rest of the evening and into the overnight while raising them from northwest to southeast towards dawn. Temperatures are quite mild in the low 60s most places and will likely stay near current values or even tick up a degree or two given the strong WAA ahead of the system`s cold front. Dewpoints, meanwhile, are also quite elevated for this time of year - running in the mid to upper 50s, while winds are generally from the south to southwest at 5 to 10 mph with occasional gusts to 15 or so mph. Have adjusted the near term T and Td grids for the current obs and trends. These grids have been sent to the NDFD and web servers. An updated ZFP and HWO were also issued along with a statement on the current flash flood watch for the northern tier of the CWA. && .SHORT TERM...(This evening through Thursday night) Issued at 330 PM EST TUE FEB 28 2017 Showers and a few thunderstorms will move across the area this afternoon through the overnight hours. Precipitation coverage is expected to be less for the overnight hours. Temperatures are not expected to drop off much overnight with warm southerly flow continuing through the overnight hours. Temperatures will soar on Wednesday into the upper 60s to lower 70s across most locations. Precipitation chances will increase again for the day on Wednesday and the severe threat increases during the day on Wednesday as well. The best severe threat will be during the afternoon hours. Damaging winds and flash flooding will be the primary threats, however large hail and isolated tornadoes cannot be ruled out. Went with a flash flood watch across northern portions of the forecast area due to previous rainfall this morning, current rainfall, and additional rainfall expected. Flash flood guidance values are a little lower across this area as well. Even outside of thunderstorm activity on Wednesday model soundings are showing some wind gusts around 30 to 40 mph. The severe threat will exit the area by evening, however some shower activity will linger into the overnight hours. A few snowflakes may mix in across eastern portions of the forecast area. Much cooler air will be in place for the remainder of the short term. Dry conditions are then expected for the day on Thursday before a weak system moves across northern portions of the region Thursday night. Temperatures will be cold enough Thursday night that precipitation will be in the form of snow. .LONG TERM...(Friday through Tuesday) Issued at 330 PM EST TUE FEB 28 2017 Northwest flow aloft with a secondary front moving through the Ohio Valley on Friday. Best moisture and lift to the north of JKL/s FA, so will limit pops to a slight chance of snow showers across the northern counties in the morning. Temperatures will be close to 10 degrees below normal with highs on Friday in the lower and middle 40s. Surface high pressure to build across the region later Friday and off the se US coast Saturday. Southerly low level flow on the backside of re-treating high pressure will develop Saturday. After a cold start temperatures to warm up to highs generally in the lower and middle 50s. Southerly flow with continued waa on Sunday will yield highs around 10 degrees above normal and generally around 60 degrees. Numerical model solution differences exist early next week regarding upper and surface low migrating through the northern Great Lakes/southern Canada. ECMWF soln is much deeper and further south with this feature than GFS. Considering this spread have followed more of a blended solution. With moisture increasing and PW/s near 1.25 inches later Monday ahead of an approaching cold front, have chance pops developing. With surface dewpoints in the upper 50s to near 60 and marginal instability indicated have also included a mention of slight chance of thunder Monday night/early Tuesday. Ahead of the cold front on the warm side of the system temperatures look to warm to highs in the lower and middle 60s Monday. Precipitation chances decrease with the passage of surface cold front Tuesday. Highs on Tuesday fall back closer to normal, in the lower and middle 50s. In the wake of the cold front surface high pressure to offer dry weather for the middle of next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) ISSUED AT 730 PM EST TUE FEB 28 2017 The region is firmly in the warm sector of a large and developing system to our northwest with its warm front lifting well north to the Great Lakes. A strong low level jet will develop overnight ahead of this low. However, the moist and convergent flow aloft will be more focused to the northwest of most of the TAF sites, so mainly dry wx is expected for the bulk of the night - though SYM could see a batch of storms develop and arrive before dawn per the latest HRRR. With the strong low level jet and lighter winds at the sfc LLWS was maintained in all the TAFs - only ending with dawn or the storms` arrival and a better mixing of the winds to the sfc. Meanwhile, look for ceilings to fluctuate between MVFR and low VFR places through the night. The strong cold front from this fairly deep low sweeps east through the Great Lakes and Ohio Valley during the day Wednesday. From this, there is a likelihood of showers and thunderstorms along or just ahead of the main boundary. Models suggest the best timing for this passage will be between 16Z and 20Z. Winds will pick up during the morning from the southwest with gusts to between 25 and 30 kts possible until fropa. After that, the winds will switch more to the west with gusts running in the 20 to 25 kts range. && .JKL WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Wednesday afternoon for KYZ044-050>052- 060-104-106. && $$ UPDATE...GREIF SHORT TERM...ILN LONG TERM...ILN AVIATION...GREIF
Area Forecast Discussion
National Weather Service Louisville KY
956 PM EST Tue Feb 28 2017 .Forecast Update... Issued at 955 PM EST Tuesday Feb 28 2017 Forecast has been updated to include Tornado WATCH 46 which is valid until 500 AM EST. The tornado watch is along and NW of a line from Simpson County to Franklin County Kentucky. Current thinking has not really changed substantially this evening with regards to the overnight convective evolution. The convective allowing models have continue to suggest that convection will continue to develop across SE MO/Far W KY and southern IL this evening. Indeed, convective activity has increased in coverage in this area over the last hour or so. The only questionable convective issue is the ongoing convection across far NE AR. This activity is moving northeast and will move into NW TN and far W KY later tonight. There is the potential that this activity could have an effect on the ongoing convection over SE MO and southern IL. Nonetheless, the majority of the model guidance suggests a cluster of convection, likely severe, will move northeastward across southern IN and far northern KY. Recent ACARS soundings out of SDF show the cap eroding slightly over the last hour. There is a very pronounced elevated mixed layer with very steep lapse rates aloft. Once this cap erodes from west to east, the atmosphere will remain very favorable for severe weather overnight with large hail, damaging winds, and tornadoes being possible. This activity does look to race northeastward and may exit our area around 500 AM EST. However, a secondary convective line along the actual front will be sweeping in from the NW around sunrise which will likely be a damaging wind producer. It is not entirely clear yet if the expected overnight convection will sufficiently overturn the atmosphere as it moves through. There are some hints that it will in some of the latest HRRR runs. So we`ll have to keep an eye on this overnight. In the meantime, it is important for local residents to remain weather aware overnight. It is important to have your severe weather plan in place and have an efficient and reliable way to receive weather warnings overnight. && .Short Term (Now through Wednesday Night)... Issued at 309 PM EST Tue Feb 28 2017 ...ROUNDS OF SEVERE STORMS EXPECTED THROUGH WEDNESDAY... ...NIGHT TIME TORNADOES POSSIBLE... Several rounds of severe storms are expected to impact the region over the next 24 hours. These could be potentially contain significant night time tornadoes along with very large hail and damaging winds. Be sure to have a way to get warnings tonight and have a plan should a tornado warning be issued for your area. Round 1 This Afternoon... Scattered showers and storms continue this afternoon. This looks to be the least significant potential round of storms. The convection from this morning and cloud cover have limited the heating across the region quite a bit. Still some storms have started to strengthen and expect we could see a few more follow suit. With DCAPE values up to 900 J/kg a few damaging wind gusts and marginally severe hail are not out of the question, but most storms are expected to stay below this threshold. These storms are expected to decrease in coverage by 00-01Z with just a few cells thereafter until the next round moves in. Round 2 Late This Evening and Overnight... This is potentially the most significant of the waves of storms. As we go into the early evening hours, soundings show a fairly stout cap developing. However, it looks to erode quickly during the 03-06Z time frame. This is when the low level jet strengthens as well. Effective shear increases to around 60 knots and storm relative helicity values increase to 400+ m2/s2 with plenty of instability. The next round of storms looks to move in between 03-06Z across mainly southern IN and north and west central KY. Large hail, tornadoes, and damaging wind will all be a possibility with these storms. The highest chance for tornadoes will be along and northwest of a line from Ohio county to Henry county in central KY and in southern IN. This is where the highest chance for large hail with supercells is as well. To the south of this line severe weather is possible overnight, though the potential decreases the farther to the south and east you go in central KY. It should be noted that the exact placement of the storms tonight has been waffling a bit in the mesoscale models this afternoon, but with the complex setup this is expected. Anyone in the enhanced to moderate risk in particular should take steps to stay weather aware tonight. These overnight storms do look like they could weaken by the 09-12Z time frame with coverage decreasing. Round 3 Wednesday... The actual cold front will move through on Wednesday. This looks to bring another round of severe weather. These storms look to be more in the form of a broken squall line along and just ahead of the front. Any capping that redevelops after the overnight storms once again is depicted as decreasing as the front approaches. The main concern with the storms along the front will be damaging winds, though some hail and brief tornado spin ups are not out of the question. A bit more questionable is out in front of the line across south central KY where some discrete cells may develop. Should this occur, the tornado and hail potential would be a bit higher, though not as high as expected overnight. This line of storms along the front should move out by mid afternoon with drying weather and colder temps expected in its wake through the overnight hours. Winds do look to be quite gusty out of the northwest behind the front. Sustained winds in the 20-25 mph range are expected with gusts of 30-35 mph. A few gusts up to 40 don`t look completely out of the question. .Long Term (Thursday through Tuesday)... Issued at 222 PM EST Tue Feb 28 2017 The long term looks to be much quieter than the short term period, at least through the weekend. Thursday should be dry and cooler with highs in the upper 40s to lower 50s. A clipper system will drop southeast into the Ohio Valley on Thursday night. This could bring some light precipitation to portions of southern IN and north central KY, mainly north of I-64. A few snowflakes could mix in with this system, but no significant impacts are expected. Behind this system, we will get another push of cooler air with highs topping out in the lower to mid 40s on Friday. The cooler temperatures will be short lived, however, as high pressure builds in and shifts across the region through the weekend. For the beginning of next week, another low pressure system tracking across the upper Midwest will bring a chance for rain as a cold front moves through. There are still significant model differences in timing with this system, so will just go with a blend of pops for now. Have also added in a slight chance for thunderstorms as models do depict at least a bit of instability. && .Aviation (00Z TAF Update)... Issued at 634 PM EST Tue Feb 28 2017 The TAF sites are in a relative lull at this hour as mid level capping holds through the evening hours. MVFR ceilings are noted, and are expected to persist most of the time, until cold frontal passage tomorrow. The mid level inversion should erode after 10 PM EST, where isolated strong and severe storms (some supercells possible/all severe modes) are expected for round 1 of storms. Best window will generally be in the 1 AM EST to 5 AM EST time frame at SDF, Midnight to 4 AM EST time frame at BWG, and 2 AM to 6 AM EST time frame at LEX. At this point, it appears most early activity will be north of the Ohio River, but SDF will have the best shot of the 3 TAF sites to experience a severe storms with the early round. After a brief lull in the pre-dawn hours, a second round of storms is expected shortly after sunrise through early afternoon along and just ahead of a cold front. These storms are expected to be more linear in nature and should pose a significant wind threat, to go along with heavy rain and lightning. In addition, very gusty W or NW winds will follow through a good chunk of Wednesday behind the cold frontal passage. Left the discrete cell passage in a TEMPO overnight, and decided to go prevailing for the second round linear storms since convection will be more widespread. Tried to nail down the best timing for both occurrences, and will amend as necessary. Overall, a dangerous night is expected into Wednesday morning for aviation purposes. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...Flash Flood Watch through Wednesday afternoon for INZ076>079-083- 084-089>092. KY...Flash Flood Watch through Wednesday afternoon for KYZ023>043- 045>049-053>057. && $$ Update............MJ Short Term........EER Long Term.........EER Aviation..........BJS
Area Forecast Discussion
National Weather Service Memphis TN
802 PM CST Tue Feb 28 2017 .UPDATE... Update regarding evolution of evening and overnight severe weather potential. && .DISCUSSION... Scattered supercell thunderstorms across northern Arkansas this evening have been driven by warm advection and increased low level moisture. These storms have shown varying degrees of intensity through the evening. The overall background environment remains quite favorable for severe weather with steep mid level lapse rates along with increasing low level and deep layer shear. In addition...low level winds remain backed near the surface across the forecast area this evening helping to increase helicity with 0-1 km SRH now around 300-400 m2/s2. The main limiting factor through the evening has been lingering capping inversion as noted on 00z soundings from KJAN...KSHV. Latest short-term high resolution model guidance continues to suggest at least scattered convection moving into northeast Arkansas and the Missouri Bootheel over the next hour and spreading into portions of west Tennessee...mainly north of Interstate 40 towards midnight and beyond. A severe weather threat will be possible with any of these storms with all storm hazards possible including damaging winds...large hail...and a few tornadoes. This initial activity should lift northeast out of forecast area later tonight. This severe threat will strongly hinge on the ability of the capping inversion to diminish which is still somewhat uncertain. A secondary focus for convection will be prior to sunrise to the west of the Mississippi River with storms focusing along an approaching cold front. This convection will also be supported by falling mid level heights associated with a mid level shortwave. The development of this convection is much more certain. Considering the degree of background instability and shear along with steep mid level lapse rates should support a greater severe weather potential with this activity. Low level winds may tend to veer late tonight with an increasingly unidirectional deep layer flow. The primary severe threats with this activity will be damaging winds and large hail. This activity will likely be more linear in nature with embedded QLCS rotations. Isolated tornadoes will still be possible with any of these rotations. This activity should spread east of the Mississippi River towards the morning rush hour and across the remainder of the forecast area through early afternoon. Updated grids and forecast products have been sent. Be prepared and ready to act if any warnings are issued tonight or Wednesday for your location. JLH && .PREV DISCUSSION... /issued 359 PM CST Tue Feb 28 2017/ Potentially active severe weather event tonight and early Wednesday, as the Midsouth is on the southern periphery of a more potent severe weather area over the Mid-Mississippi River valley, into the Ohio River valley. For the short term, will need to watch central AR closely, as the HRRR suggests this may be a source region for discrete supercells that may lift into northeast AR toward mid- evening. Hail threat and storm coverage will simultaneously increase overnight, as falling midlevel heights and steepening lapse rates overspread a strongly sheered and unstable airmass. Storms should exit northeast MS by midafternoon, after possibly undergoing a reintensification due to daytime heating. See the latest Hazardous Weather Outlook for area-specific timing and severe weather threats. Dry and cooler air will spread through the Midsouth late Wednesday afternoon and evening, setting the stage for low afternoon daytime humidity levels late in the week. This dry air will remain until more humid maritime air returns late Sunday into the early part of the upcoming work/school week. Low end rain chance prevail until the arrival of a cold front on Tuesday, which bring the region`s best chances of rain beyond tonight and early Wednesday. PWB && .AVIATION... 00z TAFs VFR weather to start again...with best timing of thunderstorms on station bringing conditions down to IFR/MVFR and higher wind gust potential. More than one round of storms is possible...especially at JBR. Outside of storms south to southwest winds will be strong with frequent gusts of 20-28kts. Low level wind shear is also a concern through the night at JBR...MEM and MKL. Cold front to push through late with improving weather...with gusty winds veering west through northwest. Winds will taper off by 02/00z. JAB && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion
National Weather Service Marquette MI
642 PM EST Tue Feb 28 2017 .SHORT TERM...(This evening through Wednesday) Issued at 355 PM EST TUE FEB 28 2017 WV imagery and RAP analysis indicated a mid/upper level trough over the wrn CONUS with several weak shortwaves embedded in the wsw flow toward the nrn Great Lakes. A shortwave and area of 850-700 mb fgen is supporting a band of light snow from cntrl mn into western Lake Superior. Another shortwave to the se and assoc isentropic ascent was producing shra and a few tsra over central Lower Mi. Over Upper Mi, a trough/cold front has moved through wrn Upper Mi into ncntrl Upper Mi, and this trough/front will continue to progress e through the rest of Upper Mi this evening. Tonight, the fgen band should support some light snow over the west and into the east overnight as the colder air moves in. Dry air in mid-levels in ice nucleation region could also support some frdz this evening in the west and especially ncntrl Upper Mi where upslope nne flow will enhance lift. A strengthening gradient between low pres into lower Michigan and high pres over nrn Ontario will result in a stiff nne wind into the region. 850 temps in the -4C to -8C will be marginal for lake enhanced snow but with strong upslope flow some light accumulations of 1 to possibly 2 inches can be expected in the higher terrain of north central and far west Upper Michigan. On Wed, shortwave now in the base of wrn conus trough will be lifting ne into Lower Mi late tonight and then another shortwave from the Central Rockies associated with the mid-level trough axis will follow later in the day on Wed strenghtening the associated sfc low moving through Lower Mi. Mid-level q-vector convergence and fgen associated with the shortwave and the deepening sfc low track could support an inch or two of light snow to southeast portion of the cwa. Some light lake effect could linger over north central cwa with NNE winds and shallow moisture to near 2kft with temps of -11c to - 12c. Otherwise expect only a dusting of system elsewhere. .LONG TERM...(Wednesday night through Tuesday) Issued at 402 PM EST TUE FEB 28 2017 The main weather concerns in the extend forecast will be the potential for light lake effect snow for north to mainly northwest wind snow belts Wednesday night through early Friday morning. Then attention turns to well above normal temperatures for the upcoming weekend. A surface low pressure sytem will continue to slide off to the east of the U.P. Wednesday night through Friday morning. At the same time, high pressure will beging to slide toward the Upper Great Lakes region from the Northern Plains. Aloft, broad troughing will remain in place across the area. The cooler air aloft, associated with the trough, and the north to northwesterly flow off Lake Superior will allow for light to occasionally moderate lake effect snow for the aforementioned snow belts. The best potential for seeing an increas in coverage/intensity of lake effect snow would be Wednesday night into Thursday morning and again Thursday night into Friday morning. This will be due, in large part, to shortwave energy rotating through the area. Generally expecting about 1 to 3 inches in the aforementioned snow belts with locally higher totals approaching 5 inches under any focused banding. The aforementioned high pressure ridge will slide across the area Friday afternoon into Saturday morning, allowing conditions to become fairly calm, with little to no chance of precipitation. Saturday and Sunday the high pressure ridge will shift east of the area as a low pressure system organizes across central Canada, allowing for stronger southerly flow between the two. A warm from is progged to approach/slide thorugh the CWA Saturday night into Sunday morning, which will allow for light precipitatioin to develop across the area. This will be around the same time that a shortwave slides in aloft. At this point, the soundings would indicate mainly rain, with possibly a mix of freezing rain and snow late Satuday night into early Sunday morning. With enough variance in the models have decided to stick with a rain and snow mixture. The upper level ridging increase for Sunday with continued southerly flow. This combination along with clearing skies could allow temperatures to warm as high as the upper 40s to possibly even 50 degrees by Sunday afternoon. Early next week, Monday and Tuesday, models continue to advertise a strong low pressure system sliding through the Upper Great Lakes region; however, there is little agreement on exact placement of the surface low and upper-level features. The GFS takes the low northwest of the area keeping temps warmer with more rain, while the EC take sthe low across the central U.P., allowing for mixed precipitation and colder air. The 12Z Canadian takes the low even farther south and east the EC, across southern lower Michigan, making the system even colder with less precipitation. All of the model disagreement has led to a consensus of the model blends with rain trending toward a rain/snow mixture by Tuesday. Again, little confidence in this portion of the forecast. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 641 PM EST TUE FEB 28 2017 Expect LIFR to IFR conditions to predominate most of the night with some light mixed pcpn changing to sn with the arrival of colder near sfc air on the heels of incrsg nne winds. CMX has the best chc to see some MVFR conditions at times as the llvl nne flow wl present less of an upslope component at that site. The sharper upslope wind at SAW wl hold in the lower cigs/vsbys there longer. Conditions on Wed should improve slowly into the MVFR range at all locations as drier air air moves into the area as well. Expect CMX and IWD to see VFR wx during the aftn. The lower conditions wl linger longer at SAW with a sharper upslope wind component farther fm the dry air source. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 355 PM EST TUE FEB 28 2017 Light winds less than 20 kts to start the day but winds ramp up quickly this aftn to 30-35 kts as low pressure system moves toward western Great Lakes. As the low crosses the central and lower Great Lakes into Wed and a high pressure ridge moves across northern Ontario, expect NE gales 35-40 kts over much of the lake Tonight with gales continuing over eastern sections on Wed morning. Winds will then remain below 30 knots through the rest of the forecast period. Heavy freezing spray is expected tonight into Wed, especially for north central portions of the lake. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Warning until 1 PM EST Wednesday for LSZ265>267. Heavy Freezing Spray Warning from 1 AM to 1 PM EST Wednesday for LSZ263-264. Gale Warning until 7 AM EST Wednesday for LSZ263-264. Lake Michigan... Dense Fog Advisory until 1 AM EST Wednesday for LMZ248-250. && $$ SHORT TERM...Voss LONG TERM...KEC AVIATION...KC MARINE...Voss
Area Forecast Discussion
National Weather Service Nashville TN
944 PM CST Tue Feb 28 2017 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Quick update to try and get better timing for upcoming chances for isolated storms in the northwest, as well as storms ahead of the cold front moving through tomorrow. Latest model runs are trending frontal timing just a bit slower than the previous forecast, so adjusted timing slightly overnight. If additional model guidance comes in slower as well, may have to adjust a bit more to try and get a better handle on timing of severe thunderstorm chances. Short term models like the HRRR, NAM and RUC have slowly been backing off timing of convection in the northwest closer to sunrise, but have indicated that some isolated cells may form in the northwest during the early overnight hours. Still looking like the best timing for severe thunderstorms ahead of the front across the CWA will be from 09Z-15Z in the northwest, 12Z-18Z through the I-65 corridor, and 15Z-21Z in the east. Again, with models slowing the front down a bit, those times may need to be pushed back slightly, and may issue another update later this evening or during the overnight hours. Otherwise just tweaked various elements to match current obs trends. Did raise winds slightly overnight and into the day Wednesday as models are also showing the surface pressure gradient tightening up a bit ahead of the front. This may allow for southerly winds around 20 mph with gusts around 30-35 mph possible overnight through mid morning. After the front passes, strong west/northwest winds around 15-20 mph with gusts around 30 mph will again be possible Wednesday afternoon. && .AVIATION... 00Z TAF DISCUSSION. A strong cold front and a line of storms will move through all three terminals during the taf period. HRRR shows some prefrontal activity near CKV by 03z. The main line of storms was timed out using the HRRR as well. The strongest cells will be capable of producing 50kt gusts at all three terminals. Behind the storms, 15 kt southerly winds will veer to the west. Cigs should improve to VFR behind the front for CKV and BNA. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......Barnwell AVIATION........Reagan
Area Forecast Discussion...UPDATED
National Weather Service Norman OK
806 PM CST Tue Feb 28 2017 .UPDATE... Expanded low chances for storms a bit farther west tonight, to a Ponca City to Waurika line and points eastward. Adjusted hourly surface elements tonight. Allowed the Wind Advisory to expire. && .DISCUSSION... A few severe thunderstorms may form and impact locations east of a Ponca City to Waurika line between 9 pm and 3 am tonight. Not confidence that storms will form at all in the Norman forecast area tonight due to the strength of the low level cap. However, based on latest HRRR model forecasts and the 18 UTC NAM12 and GFS model runs, confidence is slowly growing that a few severe thunderstorms may form and rapidly move east, mainly across the eastern half of Oklahoma, tonight. The latest SPC Day 1 shifted risk areas westward based on this guidance. Only kept rain chances in the 20-30% range due to low confidence of occurrence. If storms were to develop, very strong shear (0-1 km bulk shear around 30 kt and 0-6 km bulk shear 70-80 kt based on nearby RAP13 soundings) would support a few supercells that would move quickly east or northeast around 45 kt. First development could happen near the line mentioned above (Ponca City to Waurika). With steep mid level lapse rates (8-8.5C/km) and wet bulb zero heights around 9000 ft AGL, large hail would be the main concern, which could be very large, near or larger than golf ball size. Damaging winds would be possible if storms were to organize into a cluster or line, but this seems very doubtful as the stronger linear forcing should stay well north and east of Oklahoma. Even the tornado threat would not be zero due to strong low level shear and low LCLs due to abundant low level moisture. Again, not sure if storms will form at all, but if they do, they would have the potential to quickly become severe based on the nearby environment. The Red Flag Warning still remains in effect through 9 pm which seems reasonable due to breezy and dry conditions in parts of western Oklahoma and far western north Texas. Increasing humidity values should allow this product to expire at 9 pm. The Wind Advisory was allowed to expire at 7 pm as surface wind gusts should remain generally below 40 mph away from any possible storms tonight. The cold front will continue to move south tonight, bringing cooler and drier air along with breezy conditions. Products will be updated shortly. MBS && .PREV DISCUSSION... /issued 610 PM CST Tue Feb 28 2017/ DISCUSSION... The 00Z aviation discussion follows.... AVIATION... A deep surface low near KGAG will continue to move east overnight, dragging a cold front across Oklahoma and north Texas. Winds will shift from south to southwest at most sites about two hours before the front arrives, then to west, and finally northwest with the passage of the front. It appears that any showers or thunderstorms that occur with the front will be east of I-35, and will probably not affect any of our TAF sites. Winds will increase for a few hours behind the front, then subside until mid-morning Wednesday. As daytime mixing gets going around 1500Z, winds will increase again (from the north to northwest). Clouds should be above 12,000 ft, and no significant visibility restrictions are anticipated through the period. CmS PREV DISCUSSION... /issued 237 PM CST Tue Feb 28 2017/ DISCUSSION... Broken to overcast mid to high clouds have limited mixing for most locations except for western Oklahoma and adjacent parts of western north Texas. This has resulted in slightly more backed surface winds, higher relative humidity, and cooler temperatures. Therefore, opted to trim back part of the Red Flag Warning. For this evening into tonight, a cold front will pass by from northwest to southeast across the area. A tight pressure gradient will result in gusty northwest winds for 3-4 hours immediately behind the cold front. Some isolated storms will remain possible in the moist sector, primarily across southeast Oklahoma. The HRRR and HRRRX still indicate isolated thunderstorms will be possible across southeast Oklahoma; however, greater coverage is expected to be the east. Northerly winds will remain breezy on Wednesday, which will result in elevated fire weather conditions. Temperatures will be cooler, more seasonable for late February. By Thursday morning, the surface ridge is progged to be centered across the Southern Plains. Consequently, many locations are expected to be near or below freezing. As the ridge shifts eastward, southerly winds will return across the area late Thursday into Friday. This will commence a steady warm-up into next weekend. Southerly winds could become quite gusty by Saturday and Sunday. Also on Sunday, unseasonably warm weather is expected to return across the area. Both the 28/12Z ECMWF and GFS indicate 850 mb temperatures near 19C across western Oklahoma. A cold front is expected to pass by Monday, though there is some uncertainty on the timing of the front. There will be a chance of showers/storms as the front passes by. Cooler weather is expected behind the front on Tuesday. Mahale && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 41 58 31 62 / 10 0 0 0 Hobart OK 38 59 29 62 / 0 0 0 0 Wichita Falls TX 43 61 32 63 / 10 0 0 0 Gage OK 32 55 24 62 / 10 0 0 0 Ponca City OK 37 56 27 61 / 10 0 0 0 Durant OK 47 63 36 63 / 30 10 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...Red Flag Warning until 9 PM CST this evening for OKZ004>006- 009>011-014>016-021-022-033-034-036. TX...Red Flag Warning until 9 PM CST this evening for TXZ083-084-087. && $$ 17/23
Area Forecast Discussion
National Weather Service Blacksburg VA
908 PM EST Tue Feb 28 2017 .SYNOPSIS... A weak warm front will lift slowly northeast into the area tonight before sliding well north of the region Wednesday morning. A strong cold front will then move through the area from the west late Wednesday accompanied by showers and thunderstorms before blustery, and much colder conditions return for the end of the week. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... As of 900 PM EST Tuesday... Weak upper disturbance tracking across the region this evening will exit overnight leaving much of the area in little added forcing despite increasing warm advection aloft. Still appears that spotty showers could hang on until around midnight before guidance shows better subsidence between this feature and the upstream cold front well to the northwest. Therefore will maintain some diminishing pop coverage over the next few hours with highest east-south until the trailing tail of the precip passes to the southeast after midnight. Also trimming back added showers late since the latest HRRR suggests that any upstream precip wont arrive until perhaps early Wednesday. Otherwise winds aloft to also increase as the warm front lifts into and north of the region by daybreak. However leftover stable layer beneath the inversion aloft due to earlier rainfall, looks to be enough to keep the higher speeds up along the highest ridges, with some decoupling likely valleys and out east. This may also result in patches of fog as well in the wake of the rainfall given saturation and warm advection over the cool surface air so included mention. Also bumped down lows after seeing temps fall earlier with cooling due to rainfall. Thus expecting lows mainly in the 50s, except for some 40s mountain valleys before edging up late, and possibly only near 60 southeast where rain has been less. Previous discussion As of 340 PM EST Tuesday... Near zonal flow aloft will begin to buckle and amplify as a strong Pacific-based system shifts eastward off the west coast. Short wave ridging will continue across the eastern U.S. through the day today allowing a warm front, located across the southeast states, to lift northward. This in conjunction with an upper disturbance tracking from the Southern Plains toward the Ohio Valley will continue supporting showers with embedded thunder developing and spreading into the forecast area during the afternoon/evening hours, moving primarily north and east of the area overnight. Expect dewpoints to continue to climb this evening, settling in the middle 50s during the overnight hours. This in conjunction with cloud cover will keep temperatures from falling too much overnight, with a mere 5 to 10 degree fall from Tuesday afternoon highs expected. Winds should moderate enough to limit fog development overnight. A warmup will be well underway on Wednesday, even under mostly cloudy skies to begin the day. Some trends in the models referring to a brief period of dry mid-level air, which may promote a few peaks of sunshine early, but that will likely remain well to the south along the VA/NC border. Moist south- southwest surface winds will continue much of the day ahead of the frontal boundary, with afternoon highs in the 70s (West) and 80s (East) likely. All attention shifts to the encroaching Cold Front Wednesday afternoon. Models have come into better agreement on arrival time, bringing convection into the western portions of the area by 12/1pm before exiting to the east around sunset. Storm mode continues to look primarily linear in stature, with a few models hinting at a small time period of pre-linear convection. With low CAPE values expected due to persistent cloudcover, this doesn`t seem much of a concern at this time. Behind the front, cooler conditions and stronger winds are expected. The SPC has the entire area outlooked for a Slight Risk of Severe Weather on Wednesday, with damaging winds remaining the main threat. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 340 PM EST Tuesday... Looking at windy conditions Thursday morning then some decrease in wind during the afternoon. Temperatures will be cooler and close to early March normals with highs in the 40s west to 50s east. A fast moving northern stream front tracks across Friday with some snow showers expected in the mountains of WV and the Highlands of Va. At the moment there does not appear to much snow accumulations with this system but an inch or so could occur northwest of Lewisburg WV. Winds kick up again behind this system Friday then decrease Friday night as high pressure moves overhead. Highs Friday will be colder ranging from the mid 30s to around 40 west, to mid 40s to lower 50s east. Then temps sink well into the 20s late Friday night, so any plants that have come up, will be dealt a hard freeze. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 340 PM EST Tuesday... Models are differing on the speed of the next system early next week. The 00z/12z EC is faster than the GFS with the Euro having the front through us Monday night, and the GFS not until Tuesday night- Wednesday. WPC and trends favor Euro, so main difference shows less threat of showers as main axis of convergence and lift stay further north with the low and given the flow in the mid levels is more westerly appears any showers will diminish east of the mountains. Will see high pressure move offshore Saturday into Sunday with increasing clouds and chance of showers Monday into Tuesday west of the Blue Ridge with lesser threat east. Expect milder temperatures ahead of the front, then a quick cool down behind the front for Tuesday. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... As of 700 PM EST Tuesday... A weakening cold front continues to inch its way north through the Mid Atlantic region, spurring a wave of showers and thunderstorms southwest to northeast through the forecast area. These showers continue to pull away from KLWB/KBLF, will clear KBCB/KROA by 8pm, with KLYH/KDAN to quickly follow before 10pm or so. As the precipitation clears each area, a rebound in VSBYs and CIGS is expected, ultimately improving conditions back to VFR+ by the early morning hours. Areas of LLWS will occur periodically during the overnight hours, with 850mb wind speeds racing above a psuedo- stable layer at the surface, especially at KLYH/KBLF. Overnight Tuesday into Wednesday, an increase in low level moisture is expected, spurring on short-lived reductions in visibilities in model guidance overnight. With windspeeds maintaining 5-10 KTs, and a stable cloud deck, have opted to keep TAFs BR free, with VSBYs holding steady after the showers clear. A few breaks in the cloud layer after midnight, and this could be proven untrue. Wind speeds pick up mid morning on Wednesday ahead of an encroaching cold front from the west. This front will play host to another round of showers and storms during the afternoon hours, some of which may produce gusty winds and frequent lightning strikes. While confidence is high that TS will be involved, have opted to denote current timing with SHRA due to timing uncertainties. Future updates will correct this. For now, expect a west to east frontal passage toward the end of the TAF period, with precip entering the KLWB/KBLF flight areas by as early as 2pm Wednesday. Winds will back from SW to NW with the precipitation passages. Medium confidence in cigs throughout the TAF valid period. Lower confidence in vsbys throughout the TAF valid period. Medium to high confidence in wind speed/direction throughout the TAF valid period. Extended Aviation Discussion... The aforementioned cold front will continue its journey through the mid Atlantic region late Wednesday evening. This front is expected to exit the region just after 00z on Thursday, followed by a shift into a NW Flow regime with aggravated wind speeds. Expect improving ceilings behind the frontal boundary, with the exception of favored upslope areas (KLWB/KBLF)where upslope clouds and mountain rain or snow showers will persist. Another weak clipper looks to track just north of the region by Friday with possible mountain MVFR due to upslope cloudiness, and possible light precipitation western ridges later Thursday night into Friday. High pressures builds in with VFR expected Friday night into Saturday. && .CLIMATE... As of 330 AM EST Monday... Record warm Mins for March 1 Roanoke.....52 in 1918 Lynchburg...57 in 1910 Danville....51 in 2012 Blacksburg..45 in 1997 Bluefield...56 in 1997 Record highs for March 1 Roanoke.....76 in 1972 Lynchburg...78 in 1918 Danville....80 in 1972 Blacksburg..72 in 1976 Bluefield...78 in 1997 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/JM NEAR TERM...JH/JM SHORT TERM...WP LONG TERM...WP AVIATION...JM CLIMATE...AMS
Area Forecast Discussion
National Weather Service Tulsa OK
835 PM CST Tue Feb 28 2017 .DISCUSSION... Have increased pops across far northeast Oklahoma and for later tonight as a cold front currently across southeast Oklahoma moves into the area. The latest runs of the HRRR are beginning to highlight upscale growth of thunderstorms across northeast Oklahoma as the front moves into the state and a surface low tracks across the area. Also expect to see development southward along the front as it moves across the area overnight. The front is expected to exit the area to the south and east as we approach sunrise on Wednesday. Any of the storms that develop tonight are expected to have the potential become severe with more than adequate shear and instability in place. Tornadoes, very large hail and damaging winds of around 70 mph possible. && .TSA WATCHES/WARNINGS/ADVISORIES... OK...None. AR...None. && $$ SHORT TERM...10