Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/12/17

Area Forecast Discussion
National Weather Service La Crosse WI
551 PM CST Wed Jan 11 2017 .UPDATE... Issued at 551 PM CST Wed Jan 11 2017 Per recent trends/reports, have made a couple of small tweaks to the forecast the next hour or two, featuring a farther north expansion of precip into southern Juneau/Adams Counties. Modest axis of FGEN forcing is the culprit but should exit the next hour or two at the latest, with dual pol radar data supporting RAP/HRRR trends of a sleet/snow mix on the northern fringe and mainly just rain/freezing rain over Grant County with a distinct lack of cloud ice. Farther to the north, seeing some lingering flurries and even just plain ice crystals here at the office (notice the neat drop in correlation coefficient on radar products - kinda cool!). Will likely be able to let the winter weather advisory go early, with reports of only minor accumulation down across Grant County, but will of course watch trends for a little while. We will be closely watching the next fast-moving low amplitude shortwave working through western Nebraska currently. That feature will rapidly zip east toward our area later tonight with another tightening FGEN response aloft. The question is the degree/ placment of that forcing as well as the degree of residual dry air below 10kft. 18Z runs of the NAM/GFS/RGEM and 12Z GGEM strongly hint at a narrow band of accumulating snowfall bisecting the CWA after midnight, mainly along or south of the I-90 corridor. Starting to see a nice flare-up of reflectivity across western Nebraska the past hour or so, suggestive that these model runs have some validity, with even the HRRR starting to fall in line with that idea. Want to get another hour or to of upstream obs under our belt before jumping in full throttle, but there is a risk we will see a narrow band of perhaps 1-2" of snow accumulation later tonight. && .SHORT TERM...(Tonight thru Thursday night) Issued at 248 PM CST Wed Jan 11 2017 Main fcst concerns this period are -SN chance overnight tonight, colder/below normal temperatures thru the period. Data analysis at 18z had high pressure centered over the Dakotas with trough/front from Lk MI across SE WI into southern IA. Shortwave slipping by to the north produced a band of snow across parts of central MN/northern WI this morning, with this band quickly exiting into NE WI as of 18z. Another shortwave moving across IA was producing another round of mid/upper level lift across north/east IA into southern WI. Radar reflectivity increasing across NE IA into southern WI, but sfc obs and model soundings indicating little if any precip reaching the ground those areas yet as 900-700mb dry layer proving difficult to overcome. Elsewhere, some flurries across much of SE MN into central WI between the 2 waves/rounds of lift. No issues noted with 11.12z model initializations. Solutions quite similar as the IA shortwave exits quickly this evening then another bundle of energy out of the western troughing approaches/quickly passes later tonight. Good agreement on the next shortwave (northern stream this time) to drop toward Lk Superior Thu, opening the door for an arctic high to settle into the Upper Midwest for later Thu into Fri. Short-term fcst confidence is good this cycle. For the short-term: winter weather advisory for the SE end of the fcst area extended to 03z earlier today, to better match up with neighboring headlines. Confidence for the advisory does remain on the lower side for an advisory, however lower level thermal profiles continue to indicate precip in/near Grant Co. WI late this afternoon into very early this evening would be -FZRA/sleet. Road surfaces are cold enough for glazing to occur rather quickly, thus will continue with the advisory as issued. If precip ends up more spotty than expected, may be able to cancel it early. Next wave into the area later this evening/overnight quickly spreads another round of upper level PV advection/divergence and some mid level thermo-dynamic lift across the area, with upward motion maximized across the -15C level. Trended toward a blend of the higher guidance -SN chances overnight. Blends well with neighboring grids but given model signal may end up on the low side for a low QPF event and a tenth or 2 of snowfall over mainly the central/south parts of the fcst area. Forcing/lift any -SN quickly exits by sunrise Thu with attention turning NW as arctic high pressure builds SE across the northern plains Thu then into the Upper Midwest Thu night. Even with some sunshine Thu, consensus highs mostly in the 10F to 20F range looking good. The high ends up centered over MN by 12z Fri, with ridging SE toward lower MI. Resurgence of 925-850mb cold advection spreads across the area tonight with an even stronger shot later Thu/Thu night. 925mb temps in the -12c to -18c range at 12z Fri. This with what should be clear/mostly clear skies at least Thu evening, over the fresh snow cover (especially across the NE 2/3 of the fcst area) and light winds near/under the high/ridge axis. Favored colder of guidance lows Thu night, especially across the NE 1/3 of the fcst area. Would not be surprised to see some Fri morning lows around -20F in the colder parts of the counties along/northeast of I-94 . .LONG TERM...(Friday through Wednesday) Issued at 248 PM CST Wed Jan 11 2017 For Friday thru Saturday night: main fcst concerns this period are a small -SN chance Fri afternoon/night and temperatures. Model runs of 11.12z remain in good agreement for hgts to rise Fri then another piece of energy out of the western Conus trough to approach/move across the region later Fri/Fri night. Reasonable agreement for broad W-NW flow over the north-central Conus for Sat/Sat night. Fri thru Sat night fcst confidence is good. Rising hgts and retreating arctic high pressure allows low level warm advection to return across the area by Fri afternoon. An increase of clouds later Fri morning/afternoon ahead of the approaching shortwave will temper Fri highs, but most highs in the 5F to 15F range are looking to be a 20F to 25F diurnal swing off the morning lows. Forcing/lift with this next wave on the weaker side and mainly mid/upper level. Airmass will be quite cold, with dendritic growth zone on the relatively low side (700-600mb). Will not take much to squeeze out some flurries or a little -SN. Small - SN chances across mainly the south half of the fcst area Fri afternoon/evening look good for now. Clouds and the warmer 9325- 850mb temps to keep lows closer to normal Fri night. Warmer start, some continued low level warm advection and sunshine should allow Sat high to approach normal for mid Jan. Another high settles over the area for Sat night, with light winds and what should be clear/mostly clear skies, favorable for strong radiational cooling over the deeper/fresher snow cover. Consensus lows around zero to 10F above reasonable, even with 850mb temps approaching 0C by 12z Sun. For Sunday thru Wednesday (days 4 to 7): main fcst concerns this period include precip chances/types from Sun night into Tue, temperatures thru the period. Medium range model runs of 11.00z/11.12z in decent agreement Sun as a mid level low would move across the southwest Conus and hgts gradually rise over the Upper Midwest. Differences then begin to increase for Mon/Tue on the northern-southern stream interaction and eventual evolution of the southwest Conus low as it would lift toward/into the mid/upper MS valley. Plenty of between model and run- to-run phasing or not differences among the models. Loose consensus for some form of mid level troughing to linger over mid/upper MS valley/great lakes Wed. Fcst confidence average Sun, then below average for Mon-Wed. Slowly rising hgts aloft on Sun and retreating high pressure brings at least weak low level warm advection to the area, with Sunday`s highs returning to near normal. Low level warm advection would continue/increase Sun night into Tue, ahead of the SW Conus low/ troughing as it would migrate into the plains then toward/into the region. Moisture increases as well thru the period, along with precip chances. Lower level thermal profiles would indicate precip as snow/wintry mix Sun night, transitioning to mainly rain by Mon night/Tue, then back to mainly light snow Tue night/Wed. Again, plenty of warming/timing/strength detail differences in the day 5-7 period, contingent on when and how much northern-southern stream phasing does or does not occur. Will continue with the model/ ensemble consensus for early next week until a tighter model consensus develops and confidence increases. For now, consensus highs 5F to 10F above normal for Mon-Wed look rather well trended. However, consensus lows Sun thru Tue night lows looking as much as 5F to 10F too cool with what would be thickening lower clouds, persistent low level warm advection and the potential of precip. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 551 PM CST Wed Jan 11 2017 Conditions at LSE/RST have improved to mainly VFR the past few hours and should hold there, with some lingering flurries possible at times the next couple of hours (actually getting just plain ice crystals falling here at the office currently). Thereafter, we will have to closely watch a fast-moving system approaching after midnight. The latest trends suggest a window of snow is possible with this feature, with some accumulation possible, though confidence even at this closer range is still lower than average. For now have included an MVFR mention at both sites, but it is possible that a period of snow accumulation occurs, especially between 07Z and 12Z. Worst case scenario would be about an inch at LSE. Clouds should thin quickly through late morning/early afternoon Thursday, with widespread VFR conditions as high pressure noses into the area. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Winter Weather Advisory until 9 PM CST this evening for WIZ061. MN...None. IA...None. && $$ UPDATE...Lawrence SHORT TERM...RRS LONG TERM....RRS AVIATION...Lawrence
Area Forecast Discussion
National Weather Service Bismarck ND
757 PM CST Wed Jan 11 2017 .UPDATE... Issued at 757 PM CST Wed Jan 11 2017 The inherited forecast remains on track this evening. Attention turns to the overnight when pressure rises and increasing gradient forcing will ramp up winds. Low pressure currently over central Saskatchewan. As forecast, southwest winds are on the increase over the Northern Plains as the low approaches from the north. Across eastern Alberta and far western SK, gusts to around 40KTs are being observed on the back side of the low. Current headlines will continue, but will closely monitor upstream obs for possible upgrading. && .SHORT TERM...(This evening through Thursday) Issued at 246 PM CST Wed Jan 11 2017 Dangerous wind chills through Thursday and the potential for near blizzard conditions tonight through Thursday morning highlight the short term forecast. An arctic surge will overtake western and central North Dakota tonight through Thursday, with a two fold threat of dangerous wind chills and significant blowing snow. A 9mb/3hr pressure rise bubble associated with the surge is forecast by the 12-18 UTC GFS/NAM to approach northwest North Dakota around 07 UTC and propagate into the Red River Valley by midday Thursday. The biggest source of uncertainty with this surge regarding winds are low level lapse rates and mixing depth. The 12 UTC GFS/ECMWF depict the strongest winds and the greatest mixing depth and low level lapse rates. The 17-19 UTC RAP show a lesser wind potential, and is the middle ground above the 12 and 18 UTC NAM which show the shallowest mixing depths and weakest lapse rates. Did trend above the NAM given the strong isallobaric forcing with widespread gusts of 30-40 kts, the strongest being across the north central where near blizzard conditions are possible. However, should Canadian observations show the higher gust potential of the ECMWF/GFS, wind gusts in excess of 45 kts may be possible and true ground blizzard conditions could result. However, another source of uncertainty for true blizzard conditions is how fast the surge is expected to move through the are. Thus, issued a Winter Weather Advisory for all of northwest and central North Dakota tonight through Thursday morning for blowing snow coupled with dangerous wind chills to -40. This will have to be closely monitored should an expansion into southwest North Dakota become necessary or a possible upgrade to a Blizzard Warning based on upstream observations which is not out of the question. .LONG TERM...(Thursday night through Wednesday) Issued at 246 PM CST Wed Jan 11 2017 Dangerous wind chills Thursday night and Friday morning with a potential warm up into early next week highlight the extended forecast. Dangerous wind chills near -40 are possible Thursday night into Friday. However, the 12 UTC global models continue the trend of exiting the arctic high more rapidly into Minnesota Friday morning. Thus, a warming trend in return flow is possible late Thursday night into Friday morning after a quick temperature drop off Thursday evening. Thereafter, potential split upper level flow transitioning to zonal next week supports a possible recovery to near to above normal temperatures. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 757 PM CST Wed Jan 11 2017 A strong Alberta Clipper will move across the area later tonight. Southwest winds will strengthen ahead of the clipper this evening, eventually shifting out of the northwest with gusts to 40 kts possible. IFR/LIFR reductions in visibility due to blowing snow are expected tonight into Thursday morning, with conditions improving Thursday afternoon. && .BIS WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 3 AM CST /2 AM MST/ to noon CST /11 AM MST/ Thursday for NDZ004-005-012-013-019>023-025-034>037. Wind Chill Advisory until 3 AM CST /2 AM MST/ Thursday for NDZ004-005-012-013-019>023-025-034>037. Wind Chill Advisory until noon CST /11 AM MST/ Thursday for NDZ017-018-031>033-040>045. Winter Weather Advisory from 1 AM to noon CST Thursday for NDZ001>003-009>011. Wind Chill Advisory until 1 AM CST Thursday for NDZ001>003- 009>011. Winter Weather Advisory from 5 AM to noon CST Thursday for NDZ046>048-050-051. Wind Chill Advisory until 5 AM CST Thursday for NDZ046>048-050- 051. && $$ UPDATE...NH AVIATION...NH
Area Forecast Discussion
National Weather Service Columbia SC
1009 PM EST Wed Jan 11 2017 .SYNOPSIS... Upper high building to our south will provide fair and warm conditions through Friday. A backdoor front will move into the region Saturday and provide a slight chance of showers through early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Model time-height sections suggest stratus developing late tonight and possibly fog. Boundary layer mixing may limit fog. The HRRR shows fog mainly in the coastal plain. SREF fog probabilities are higher in the east section. The LAMP guidance indicates fog. We included fog in the forecast late tonight although low cloudiness may be more common. Cloudiness should help hold up temperatures. Expect lows in the upper 40s to around 50. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... Fair and warm conditions expected, as upper high builds just to our south, and surface high axis remains to our S and E, providing a warm low-level flow out of the S/SW. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Not many changes to the extended forecast. Upper high center to remain to our south while northern stream upper trough swings east across the northern tier of states, bringing down another cold front. Models indicate the front will initially make slow progress southward as its encountering a WSW upper flow nearly parallel to it, but eventually it oozes down the eastern seaboard as a backdoor front as the parent high behind it shifts into the NE US. This will lead to lower temps, and possibly some showers mainly Friday night into Saturday. At this time, shower chance appears minimal with only weak isentropic lift and not much upper energy. Weak low-level wedge appears could gradually erode as another boundary shifts SE and appears to back door either into our region or possibly remain just to our NE. Uncertainty on specifics, but it appears slight chance pops at best and generally above normal temps Mon/Tue, with more significant moisture moving into the area Wed as an upper trough amplifies deep into the Southern Plains. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... VFR conditions expected through the early evening. Restrictions expected during the early morning through sunrise hours. High pressure ridge across southern GA continues allowing moist southerly flow over the area as a cold front pushes northward into the Ohio Valley. Main concern for the period remains potential for fog and stratus from the early morning through mid morning hours. Have remained with MVFR conditions at all TAF sites...with TEMPO LIFR conditions at fog prone AGS/OGB. Inversion will mix out by mid morning with conditions returning to VFR by 15z and remaining so through the end of the period. Winds will generally be south-southwesterly at 8 knots or less through the forecast period. EXTENDED AVIATION OUTLOOK...Restrictions possible during the late night/early morning hours each day. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$ SYNOPSIS...99 NEAR TERM...99 SHORT TERM...99 LONG TERM...99 AVIATION...99
Area Forecast Discussion
National Weather Service Charleston SC
938 PM EST Wed Jan 11 2017 .SYNOPSIS... High pressure will remain over the western Atlantic through early next week before a cold front potentially impacts the area. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... As of 935 PM: Interesting to see bands of wavy reflectivity from KCLX and KCAE radars. Based on the movement, or growth, of the bands and very low values of correlation coefficient, it appears to be chaff. Sfc observations indicate that winds over land have lowered to near calm, dewpoint depressions have closed to one to two degrees. It appears that fog will develop across the region by midnight. Patchy areas near the coast could see visibilities less than a mile around dawn. I will update the forecast to make small changes to the placement and timing of the fog. Otherwise, the current forecast appears in good shape. As of 640 PM: Observations across the forecast area generally indicate that dewpoints ranged from the mid 50s to near 60 degrees. Forecast low temperatures range from the near 50 inland to the low 50s across KCHS and KSAV. It is interesting to see the HRRR indicating a developing thin ribbon of low values of sfc condensation pressure deficits over the cooler shelf waters between 23Z to 0Z. Winds over the waters are forecast to remain light from the SE, slowly advecting the moist layer inland. A recent pilot boat reported patchy fog over the harbor and off the coast. Based on the higher dewpoints, forecast decreasing winds, and thin high clouds it appears that fog will gradually thicken during the pre dawn hours. I will update the forecast to increase the mention of fog over the land and over the waters. Otherwise, the current forecast appears on track. Afternoon radar shows some showers offshore associated with the weak coastal trough. The showers will diminish this evening as the trough dissipates. Otherwise, surface high pressure centered offshore will keep the area dry tonight. The combination of mostly clear skies, light to calm winds, and dew points in the lower 50s could lead to fog development tonight. The SREF indicating the best probabilities for fog along and west of I-95. We have areas of fog in these locations and patchy fog elsewhere. This may need to be adjusted based on the observational trends in the upcoming hours. Lows should range from the upper 40s to lower 50s. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... Thursday and Friday: The area will remain along the western edge of Atlantic high pressure at the sfc while a large mid-lvl ridge of high pressure expands over Florida and eventually much of the Southeast/Deep South into early weekend. The pattern will result in dry, but well above normal temps for this time of year. Partly to mostly sunny conditions along with a light westerly wind aloft will help temps approach the mid 70s on Thursday, then mid to upper 70s on Friday. Given these temps, there is a potential of a record setting high Friday afternoon at the CHS airport (78 degrees). Overnight lows will remain mild, in the low/mid 50s Thursday and Friday nights, but fair radiational cooling along with light/calm winds could produce some patchy fog late each night to around daybreak. Saturday: High pressure will wedge southward along the Eastern Seaboard while a broad ridge of high pressure persists aloft. The pattern should support slightly cooler conditions as a light northeast wind prevails. Afternoon high temps will still be above normal, ranging in the upper 60s north to lower 70s south. A few showers could also drift onshore, mainly along coastal locations of Southeast Georgia where moisture is drawn from the Atlantic. However, rainfall accumulation will likely be low. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... A deep layered ridge will remain the dominant feature during the extended period, maintaining above normal temperatures. Rain chances increase Tuesday into Wednesday as a cold front approaches the area. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... As of 640 PM: Observations across the forecast area generally indicate that dewpoints ranged from the mid 50s to near 60 degrees. Forecast low temperatures range from the near 50 inland to the low 50s across KCHS and KSAV. It is interesting to see the HRRR indicating a developing thin ribbon of low values of sfc condensation pressure deficits over the cooler shelf waters between 23Z to 0Z. Winds over the waters are forecast to remain light from the SE, slowly advecting the moist layer inland. However, 2m winds over the terminals will remain around 5 kts through most of this evening. However, as winds decouple and weaken after midnight, fog should easily develop under thin high clouds. By the pre dawn hours, the visibility is expected to fall to at least IFR values, possibility accompanied by VLIFR level stratus. Conditions will gradually improve after sunrise, returning to VFR by 14Z. Afterwards, fair weather with developing south winds between 5 to 10 kts. Extended Aviation Outlook: VFR conditions should generally prevail through the weekend. However, flight restrictions will be possible at either terminal Thursday and Friday mornings due to low clouds and/or fog. && .MARINE... Atlantic high pressure will dominate the coastal waters through early Friday, resulting in winds no higher than 10 kt and seas generally ranging between 2-4 ft. High pressure will then build from the north this weekend, supporting a slight enhancement to the pressure gradient and weak cold air advection within a northerly flow. In general, north/northeast winds will peak around 15 kt, highest in northern South Carolina waters on Saturday. Seas will also build to 3-5 ft, highest in offshore Georgia waters on Saturday. Conditions should gradually improve on Sunday as the pressure gradient slackens over coastal waters early next week. There is a low probability of sea fog developing through late week as light southerly flow helps dewpoints approach 60 degrees over cooler nearshore waters. && .TIDES/COASTAL FLOODING... Due to the a perigean full moon tide cycle, tidal waters may approach 7 ft MLLW along the SC coast each morning through Saturday. For GA, conditions should favor the tidal waters remaining below Advisory levels. Otherwise, it is possible that SC coast could see Coastal Flood Advisories during the morning high tide. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...NED SHORT TERM... LONG TERM...JRL AVIATION...NED MARINE... TIDES/COASTAL FLOODING...NED
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
627 PM CST Wed Jan 11 2017 .AVIATION... 00 UTC TAF Cycle Concerns---Return of MVFR stratus during the overnight hours. Possible FROPA in the DFW extended. For the Metroplex TAF sites---Gusty south winds should subside through the evening hours with gusts falling below 20 knots around 0200 UTC Thursday. The main challenge will be the onset of MVFR stratus expected to develop later this evening and into the overnight hours. Overall low level moisture parameters look to be more conducive for widespread MVFR stratus and I`ll prevail these conditions through mid-morning Thursday. There is a LOW potential for some IFR ceilings, but similar to last night, low level winds should remain strong enough to support low level mixing. VFR will return briefly Thursday afternoon with breezy winds. Speeds should not be as strong Thursday afternoon, but some gusts to near 20 to 22 knots still appear plausible. With the additional low level moisture, there will be a risk for some isolated showers, but the better probability looks to be just east and south of the Metroplex TAF sites. For now, will keep TAFs precipitation-free and monitor trends in model output. The forecast becomes a bit trickier during the extended portion of the DFW TAF as MVFR stratus is expected to surge back towards the west and north. Most models keep the cold front further to the north in KS/OK, but the latest NAM plows the front southward through DFW by 06 UTC. For now, will wait on the latest suite of 00 UTC model output, but if the NAM solution is to verify, rain/storm chances coupled with MVFR to possibly IFR ceilings and north winds will be more likely. For now, will keep DFW terminals in south flow with MVFR ceilings. For the Waco TAF site---VFR will continue over the next several hours as gusty south winds subside. MVFR stratus is expected to develop quickly and should impact the Waco TAF site around midnight. There is a chance for IFR stratus, but winds should remain elevated enough to largely mitigate this potential. MVFR stratus will likely prevail through 00 UTC Friday with south to southwest winds. There will also be a risk for some rain showers, but right now, this potential seems a little too low to include in the TAF at this time. 24-Bain && .PREV DISCUSSION... /ISSUED 334 PM CST Wed Jan 11 2017/ It`s been yet another day featuring highly anomalous warmth and strong southwesterly winds today. We`re within a whisper of another record high temperature at DFW (83 in 1911), with the record appearing safe at Waco (84 in 1905). Sustained wind speeds near and east of the I-35 corridor have been in the 25-30 mph range this afternoon, with gusts approaching 40 mph at times. RAP analysis depicts 35-45 kts of flow remains in place at 925 mb, and momentum transfer will continue for the next few hours resulting in wind advisory-criteria winds being met across portions of our CWA, effectively along and east of I-35 through 6 PM. Tonight, moisture will continue to migrate northward, with an axis of 1"+ PWATs creeping across our easternmost counties. Some warm advection-facilitated showers will be possible here, but coverage should be spotty at best. Low clouds will also develop within this zone, but elevated winds in the 25-35 kt range atop the cooling boundary layer should significantly curtail any widespread fog development. It`s conceivable some patchy fog may develop across our southwestern zones where the low-level flow will remain weaker, but confidence in this was too low to warrant inclusion in the gridded forecast. As additional moisture arrives on Thursday, isolated showers and perhaps an embedded thunderstorm will be possible as the morning stratus deck slowly mixes out. Widespread storms are not in the cards, however, as a stout capping inversion at around 800 mb-- reinforced by southwesterly winds aloft--will remain in place. As a result, precipitation chances on Thursday appear very low, and will only be advertising 20% PoPs across most of the region. By late Thursday morning our next cold front, which is currently plunging southward towards the Oklahoma/Kansas border, should be spilling across the Red River into our far northwestern counties. As has been the case all winter, these shallow arctic intrusions, characterized by frontal inversion depths of 1 kft or less, have been well handled by the NAM. This case appears no different. As a result, we`ve actually closely followed the NAM and high- resolution output for this forecast regarding frontal timing Thursday and into Friday. The air behind this front won`t be tremendously cold, but lows will likely fall into the upper 30s across the northwest Thursday night. Thursday night and through Saturday... As a subtle shortwave approaches and warm advection increases down low, showers and a few storms will begin to blossom along and north of this front, which should be stalling around a Comanche to Waxahachie to Sulphur Springs line (potentially even a bit farther south). Lift won`t be overly strong at this point, so we`ll cap PoPs at 60% across the north and western counties with chances decreasing precipitously south of I-20 during this time frame. QPF amounts should overall be pretty light, generally in the half inch to one inch range with some locally higher amounts in thunderstorms. Saturday night into Sunday morning... This period may actually feature a brief lull in activity as a deep upper-level low begins to eject eastward towards Chihuahua Mexico. Increasing southerly flow should help send the stalled front north of the Red River, leaving us with just slight chance to chance PoPs. Sunday afternoon through Monday night... This period looks to feature the highest potential for widespread heavy rainfall, thunderstorms, and flooding concerns. The model consensus ejects the aformentioned upper low into the Texas Panhandle which will ultimately result in the eastward advancement of a cold front through North and Central Texas. Widespread showers and storms will be developing into a very moisture-rich airmass, characterized by PWATs near 3 standard deviations above normal and respectably deep warm cloud layers around 10 kft. The severe weather potential during this time still appears low, but is certainly non-zero. The limiting factor continues to be a lack of appreciable instability, but we will need to monitor this closely as this dynamic system will offer up plentiful wind shear, especially in the lowest 3 km. Precipitation may be slower to clear out than previously anticipated with broad troughing lagging well behind the front. As a result, shower and storm chances may linger into Tuesday across our region. Carlaw && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 63 77 53 61 49 / 10 20 30 40 50 Waco 63 76 63 73 55 / 10 20 30 30 30 Paris 63 75 55 66 53 / 20 30 40 50 50 Denton 60 73 46 54 45 / 10 20 40 50 60 McKinney 63 73 51 60 48 / 10 20 40 40 50 Dallas 65 78 56 62 51 / 10 20 30 40 40 Terrell 64 76 58 70 55 / 20 30 30 30 40 Corsicana 65 77 63 75 59 / 20 20 20 30 30 Temple 64 77 63 75 58 / 20 20 30 30 30 Mineral Wells 57 72 48 55 42 / 10 20 40 50 60 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 24/58
Area Forecast Discussion
National Weather Service Green Bay WI
919 PM CST Wed Jan 11 2017 New Information added to update section .UPDATE... Issued at 912 PM CST Wed Jan 11 2017 The winter weather advisory has been allowed to expire, and any lingering snow should end in Manitowoc county by 10 pm. Had snowfall totals of 4 to 6 inches from Oshkosh to Chilton to Manitowoc, with snowfall rates briefly exceeding 2 inches an hour at times. Have reworked the pops for late tonight into Thursday morning to account for another possible band of snow over the southeast half of the forecast area. Raised pops to likely southeast of a line from Waupaca to Sturgeon Bay. Only forecasting accums of an inch or less for now, but locally higher totals are possible, as tonight`s event clearly illustrated. UPDATE Issued at 452 PM CST Wed Jan 11 2017 Radar, observers and web cams indicate snow, sleet and possibly some freezing rain occurring southeast of a line from Wautoma to Appleton to Kewaunee. RAP model had a good handle on pcpn trends associated with the pcpn band, which was being generated due to mid-level frontogenetic forcing and the LFQ of a 140 kt upper level jet. Models show this band quickly exiting by mid-evening. Expect snow/sleet accumulations of 1 to 3 inches, with a light glaze of ice also possible. Hazardous travel conditions warrant the issuance of a winter weather advisory til 9 pm. && .SHORT TERM...Tonight and Thursday Issued at 304 PM CST Wed Jan 11 2017 Next 12 hours continues to be active as various upper jet features working with a baroclinc zone over the region. Early this afternoon, RRQ dynamics with an upper jet with the 700 mb fgen region over northern Wisconsin is loosening its grip. Radars show a diminishing trend with visibilities improving early this afternoon. Advisory ending by 3 pm looks good. Next focus is redevelopment of precipitation this afternoon and into this evening over the southeast half of the state. This precipitation is associated with a surface wave riding along the surface front which at 19z extended from Kansas City to Milwaukee to northern Lower Michigan. The surface low is expected to be aided by the LFQ region of another upper jet. The GFS is producing 0.25 inches of qpf from 21z-00z this afternoon east of the Fox river while the NAM is producing slightly less. The short range RAP and HRRR were also producing a narrow 0.25 inches for this same area and time period. Forecast soundings were suggesting snow but mixed with sleet at times. Freezing rain is also possible toward southern Manitowoc county. Area radars were showing increasing returns the southeast third of the state including northeast iowa, but little ground truth so far. If this mixed precipitation can get its act going, will be impacting east central Wisconsin during the late afternoon and early evening commute. Since this is in the development phase, will continue with higher end pops and keep the sps running for this potential. But a short term advisory for EC WI not off the table yet. Will keep chc pops going Thursday morning until the weak 850 mb trough with baroclinic zone departs the area. Otherwise drier colder air on westerly winds will work into the region later Thursday. .LONG TERM...Thursday Night Through Wednesday Issued at 304 PM CST Wed Jan 11 2017 The medium range models show a quieter pattern developing later this week, when a closed upper low moves across the southwest conus, leading to split flow across the majority of the lower 48. This southwest upper low may impact our region around the early or middle of next week. Prior to this, forecast will largely revolve around temps and minor precip chances. Will put more weight into the ecmwf for this forecast. Thursday night through Saturday...Will see clear skies for Thursday night, but arctic high pressure will be building towards the area, with cold advection continuing through the evening. Northwest winds will be especially breezy during this time, though they will lighten up some late. As temps fall through the single digits and teens below zero, wind chills will drop into the 20s below zero over central and north-central WI overnight into Friday morning. A wind chill advisory will likely be needed. Continued very cold on Friday with mid and high clouds increasing ahead of weak shortwave energy. This shortwave could bring a light snowfall to central and northeast WI on Friday night. QPF is relatively meager so perhaps a dusting is possible. That snow will pull out late Friday night, and arctic high pressure will return for Saturday, with temps returning into the 20s. Rest of the forecast...High pressure will continue to stick around on Sunday and Monday morning, with near normal temps. Then will be watching the upper low lifting northeast out of the Central Plains for Monday afternoon into Wednesday. Temperatures will be warm enough ahead of the system for a wintry mix, so too early to estimate potential snowfall/ice accumulations. && .AVIATION...for 00Z TAF Issuance Issued at 541 PM CST Wed Jan 11 2017 Main focus will be on the southeast portion of the forecast area, where a band of mixed pcpn will affect the region through mid- evening, and another band of snow is expected to redevelop late tonight into mid-morning Thursday. MVFR/IFR conditions are expected during both of these periods, especially at the ATW and MTW TAF sites. Farther northwest, anticipate mainly VFR conditions, though there are some MVFR ceilings drifting down off Lake Superior that will impact far north central WI, and could eventually push into RHI. Will keep an eye on this during the evening. Otherwise, clearing is expected across most of the region during the late morning and afternoon on Thursday. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE.........Kieckbusch SHORT TERM.....TDH LONG TERM......MPC AVIATION.......Kieckbusch
Area Forecast Discussion
National Weather Service Huntsville AL
907 PM CST Wed Jan 11 2017 .NEAR TERM...(Tonight) Issued at 707 PM CST Wed Jan 11 2017 Area radars indicate batch of drizzle and possibly light rain moving northeast into west central AL. The latest HRRR depicts this area moving across north central and northeast AL into southern TN between 01-04Z. I have updated the weather grids to include patchy drizzle along with the slight chance of light rain. No other changes needed at this time. .SHORT TERM...(Thursday through Friday night) Issued at 334 PM CST Wed Jan 11 2017 Little if any change in the overall synoptic pattern is anticipated during the remainder of the short term period, as the subtropical ridge is forecast to strengthen and drift northward along the Florida peninsula and into southern GA while a 500-mb trough pivots southeastward along the Pacific coast. To our north, a potent vort max within the base of the Canadian trough will dig southeastward over Saskatchewan/Manitoba tonight allowing a surge of colder arctic air to invade the northern Plains early tomorrow morning. This airmass will rapidly expand and overtake the Canadian airmass currently in place north of the cold front, with the front expected to accelerate southeastward Thursday afternoon -- extending from northeastern KY to western TN by 00Z Friday. Although low-level flow will tend to diminish and veer tomorrow afternoon as this occurs, temperatures should warm to near record levels in the u60s-m70s based on low temps expected tonight. The current forecast has the record high of 72 (in 2013) being tied at HSV (record corrected from previous AFD), and it should be a close call as well for MSL where the record high is 75 (in 1916). Isolated showers will remain a possibility for the region once again tomorrow, but expected coverage only warrants a 20 POP. Most short term guidance is in agreement that the cold front will continue drifting very slowly southward and slowly lose definition on Thursday night and Friday, as the subtropical ridge to our south strengthens and the boundary becomes increasingly parallel to winds aloft. Although the wind shift associated with the front may push into nw Alabama and southern TN early Friday morning, the coldest air will remain immediately to our north/west -- with only a few degrees of cooling noted in the northern zones. It appears as if warm advection atop the shallow cool airmass will support a broad region of postfrontal rain extending from northern AR into eastern KY on Thursday night, with an increasing coverage of showers expected for our area before sunrise Friday as low-level convergence increases in the vicinity of the approaching boundary. The amount of shower activity will likely peak on Friday, before the Pacific coast mid- level trough ultimately forces the front to return northward early Saturday morning. In addition to the showers, light winds in the vicinity of the dissipating front will be favorable for patchy mist/fog for an extended period from Thursday night-Friday night. .LONG TERM...(Saturday through Tuesday) Issued at 334 PM CST Wed Jan 11 2017 An upper level ridge extending northward from a strong area of high pressure over the Gulf of Mexico will continue to remain in place over the Tennessee Valley on Saturday. This will keep a weak boundary north of the area. Models vary, but keep it somewhere between Kentucky and north central Tennessee. Models continue to show some weak isentropic lift extending southward from this feature into Southern Middle Tennessee. This combined with abundant low level moisture could produce a few showers in this area (maybe down to the Tennessee River). However, a very strong cap produced by the warm temperatures advected east via southwesterly/westerly flow above 850 mb should keep shower coverage isolated to widely scattered and thunderstorms out of the forecast. Some models (such as the ECMWF) keep this boundary further south through the Nashville area into northwestern Georgia. Think this may be a bit too far south, given persistent low level southerly flow and the strength of the upper level ridge over the Gulf. Thus, forecast reflects lower pops overall than model blends/ECMWF. Expect a break from precipitation chances Saturday night through Sunday night, as the boundary moves further north. Temperatures through Sunday should reach the 63 to 68 degree range, with 925 mb temperatures progged to reach the 11 to 14 degree range. Lows in the lower 50s look reasonable as well. Unfortunately, we will not see much of a break from mostly cloudy conditions though. By Sunday night into Monday morning, models continue to quickly move a 1005 mb surface low (with a strong upper low associated with it) northeast into the Upper Midwest. Some models develop a fairly decent shortwave ahead of this feature over Arkansas/Missouri by Monday morning and hint at a secondary warm front developing east of I-65. Ridging will be weakening in response by then. Included isolated to scattered showers in the forecast on Monday due to the possible warm front, which lifts northeast in the evening. Better forcing and wind energy begins to move into northern Alabama and Southern Middle Tennessee by Tuesday night into Wednesday with the latest model runs with a developing cold front. This will make for breezy conditions on Tuesday with southerly winds 10 to 15 mph with gusts to 25 mph. Wind advisory may be needed on Tuesday/Tuesday night as winds at 925 mb strengthen to around 45 knots. Elevated CAPE develops by Tuesday night. Expect even more widespread elevated and surface based CAPE to develop on Wednesday, as the front moves into Mississippi. This could produce some strong storms as well, with enough shear, helicity and forcing forecast ahead of this front over the Tennessee Valley. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 448 PM CST Wed Jan 11 2017 South flow will gust to ~20kt at times tonight, especially this evening. Ceilings of ~025agl (MVFR) will redevelop by around 03Z due to the moist south flow. Ceilings could lower into the 010-015agl range by 07Z and last through Thursday morning. A spotty shower cannot be ruled out, but the probability is too low to include at this time. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...17 SHORT TERM...70/DD LONG TERM...KTW AVIATION...17 For more information please visit our website at
Area Forecast Discussion
National Weather Service Norman OK
821 PM CST Wed Jan 11 2017 .DISCUSSION... The front is moving more quickly than realized earlier during the afternoon. Although a bit slow, the HRRR continues to have a good forecast, and now it brings the cold front through Oklahoma City about 1 AM. Forecast grids were updated with this wind shift timing. Additionally, temperatures in the lower 20s are now entering the southern half of Kansas on 10-15 kt and gusty north winds. Hourly temperatures were accelerated downward, and early Thursday morning minimum temperatures were lowered noticeably in northern Oklahoma. Upper teens are expected along the northwest Oklahoma border by Thursday morning. Forecasts for the Friday freezing rain event remain unchanged. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 29 45 30 31 / 0 0 40 60 Hobart OK 33 47 29 31 / 0 0 30 50 Wichita Falls TX 46 50 35 39 / 0 0 40 60 Gage OK 21 41 24 29 / 0 0 10 50 Ponca City OK 22 41 28 30 / 0 0 20 60 Durant OK 64 66 41 55 / 10 20 50 60 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...Winter Storm Watch from Friday morning through late Saturday night for OKZ004>030-033>036-038. TX...None. && $$ 09/23
Area Forecast Discussion
National Weather Service Raleigh NC
850 PM EST Wed Jan 11 2017 .SYNOPSIS... High pressure over the western Atlantic will extend westward across the area through early Friday. A backdoor cold front will enter the state from the north late Friday, and push through the area to our south Friday night. && .NEAR TERM /THROUGH TONIGHT/... AS OF 850 PM WEDNESDAY... The biggest forecast problem tonight is the extent of fog and shallow stratus. The latest surface analysis shows the western Atlantic ridge extending narrowly to the WSW across the Carolinas, with a cold front well to our NW, stretching from the Great Lakes to OK. While the light surface flow is out of the SE/S/SW over central NC, a residual weak stable pool is holding over the western and central Carolinas, where cooler surface temps but higher dewpoints are favoring development of patchy fog and even more patchy stratus. The steady stream of high clouds over the area is likely to persist overnight, which will somewhat limit the surface radiational cooling, making fog development less certain. RAP analyses and area/upstream 00z soundings also show comparatively dry air just aloft, noted at 925 mb, with no low level moisture transport indicated tonight on the latest model runs. So if the breeze stays up just enough tonight to keep the low levels a bit stirred, then a widespread fog/stratus event would be unlikely. Have opted to keep fog coverage as patchy. Skies should remain mostly cloudy tonight, regardless of stratus development as high clouds pass overhead. Current dewpoints are sitting in the mid 40s to mid 50s, and these are unlikely to vary much overnight, representing the probable floor of temps tonight. Expect a minor drop from current readings, with overall lows well above normal, in the mid 40s to lower 50s. -GIH && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 245 PM WEDNESDAY... Very little change expected in our weather pattern. Abundant low level moisture will maintain areas of fog and low clouds early Thursday morning. While extensive cloudiness will persist, a few breaks in the overcast skies, especially across the southeast half, in conjunction with a warm sly breeze gusting between 20 and 25 mph should permit temperatures to soar above 60 degrees by lunchtime along and east of highway 1, with afternoon high temperatures ranging from the lower 60s NW to around 70 SE. While a stray shower cannot be ruled out, probability of getting wet too low to mention in the forecast at this time. A mid level s/w projected to cross our region late Thu-Thu night. While no sensible weather expected with this feature, wly flow on the back side of the trough will advect a drier air mass into the mid levels of the atmosphere. This may lead to some partial clearing in the lower half of the atmosphere. This partial clearing may promote a the potential for another round of fog to develop late Thursday night. Another mild night expected with overnight temperatures in the upper 40s-lower 50s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... As of 159 PM Wednesday... The upper level high, centered over FL, will gradually weaken Friday and Saturday. Meanwhile, upper level flow over NC will gradually transition from west-southwesterly, to westerly, to northwesterly. At the surface, high pressure over the Carolinas will weaken Friday and a backdoor cold front will subsequently slide south into Central NC Friday night and Saturday. The models still show a weak CAD wedge setting up over western portions of the area on Saturday in the wake of the front. The wedge may linger as the front retreats back northward late Saturday into Sunday. Weak disturbances in the west- northwest flow aloft may result in some light rain/drizzle across the west an north, which would act to reinforce the wedge for a while longer. Do not expect any p-type issues or significant rainfall accumulations at this time. Skies will likely remain cloudy, especially where the wedge remains in place, from Saturday onward. The upper level ridge will briefly build back over the southeast U.S. Sunday night/Monday. As the next weather system to impact the region develops over the Midwest. It is quite possible a remnant wedge could linger in the Triad and points west through early next week and erode late Tuesday/Tuesday night as the next frontal system approaches the region. Flow aloft will become increasingly more meridional as the ridge builds over the southeast U.S. and the trough deepens over the Midwest. The resultant south- southwest flow between the two will increase moisture advection ahead of the front and increase precipitation chances from west to east mid-week. Temperatures: Highs Friday will be well above normal, mid 60s north to low 70s south. With the backdoor front and wedge setting up, expect much lower highs (but near normal) for Saturday, mid 40s northeast to low 50s south. Lows generally in the upper 30s to mid 40s. Expect moderating temps again Sunday through Wednesday, more uncertain in the vicinity of the wedge as they will depend on if/when it erodes. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... AS OF 650 PM WEDNESDAY... 24 Hour TAF period: Conditions already starting to deteriorate across the area. KRWI has already gone down to IFR levels and is expected to remain there or go down to LIFR overnight. All other sites will have an opportunity to go down to IFR/LIFR levels as well in the form of patchy dense fog. This will likely initiate between 3-6z and remain there through sunrise. Also of concern overnight is some borderline low level wind shear, particularly at the Triad sites where 35 kt shear at 2000 feet could be experienced. Also have included in the KRDU TAF for 30 kts at 2000 feet. Some light drizzle may move through overnight but of no real consequence. On Thursday afternoon, ceilings are expected to begin lifting and once they do a mixed layer will develop that could cause wind gusts up to 25-30 kts across the forecast area. Long term: A fairly moist pattern will lead to the chance of fog and low clouds each morning for the next several days. In addition a small chance for rain early Thursday morning and a frontal zone that will linger near the area through the weekend could cause some adverse aviation conditions. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield SHORT TERM...WSS LONG TERM...KC AVIATION...Ellis
Area Forecast Discussion
National Weather Service Blacksburg VA
854 PM EST Wed Jan 11 2017 .SYNOPSIS... A weak warm front to the northwest of the area will continue to lift north and weaken overnight. Warmer southwest flow behind this boundary will increase later tonight and continue into Thursday. Another cold front will approach the region from the north by Thursday night, before spilling south through the area Friday into Friday night. && .NEAR TERM /THROUGH THURSDAY/... As of 845 PM EST Wednesday... Patchy earlier rainfall in advance of a warm front passing to the west has exited the region this evening leaving a varying degree of residual cloud cover in place. Latest evening soundings show quite a bit more moisture than last night but most forcing overnight looks to stay to the north/west of the region. Thus have removed most lingering measurable rain chances overnight with focus more on spotty drizzle along with areas/patchy fog pending just how much of the strong jet aloft can mix down. Latest short term guidance also showing less cloudiness across the east overnight, so appears this likely the region that could see more fog and eventually some stratus. Otherwise mainly cloudy and a bit gusty at elevation under the southwest jet aloft. Expect temps to remain about steady for a while longer with some quick drops where clouds thin before slowly rising later as warm advection deepens from above. Did lower some spots espcly valleys where have dropped off into the 30s, and below previous forecast lows, with most likely to stay in the 40s overnight. Previous discussion as of 320 PM EST Wednesday... Low pressure will move from the Midwest this afternoon into eastern Canada tonight into Thursday and an upper ridge builds across the Southeast States. The frontal boundary will stall this afternoon and return fairly quickly as a warm front tonight. Rain associated with the front will lift north this afternoon into evening back across the northern parts of the CWA. The warm frontal associated rainfall will then drift north into northern VA/WV overnight. For pops initially started with blend of HRRR and HiResW-arw-east and trended towards the Nam for tonight into Thursday. Considerable cloudiness will persist with the low level waa pattern and the cool moist ground. Deep low-level moisture across the area will result in patches of drizzle and fog especially from the Shenandoah Valley southwest into the New River Valley. Low temperatures tonight will range from around 40 degrees in the northern mountains to near 50 degrees in the far western mountains. Our region will be in the southern stream of a split flow regime on Thursday, with a large cutoff low over the southwest and flat ridging over the Southeast. This will keep us in a mild and moist pattern with cold air bottled up well to our north. With a weak baroclinic zone just off to our west, isolated to scattered rain showers are possible west of the Blue Ridge Thursday. High temperatures Thursday will vary from the mid 50s in the mountains to the lower 60s in the Piedmont. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... AS OF 334 PM EST Wednesday... Cold front enters the mountains Thursday night. Best low level convergence stays across the Central Appalachians and points west, so will stay with drier scenario per model blend east of the Blue Ridge with high chance to low likely over Southeast WV to the Clinch River Valley of Southwest Virginia. With front crossing the Blue Ridge late, should see temperatures stay relatively steady Thursday night and mild, with lows actually expected to be warmer than what are normal high temperatures are for mid-January, in the upper 40s to lower 50s. We may see some record warm low temperatures broken. Friday, the front slides southeast to NC with a wave of low pressure tracking along it from leading to an increase in chances of rain. Should be a cooler day as wind flow turns more northwest yet light, with cloudy skies. However, temperatures starting out in the upper 40s to lower 50s may surge up enough about 5 to 15 degrees before it rains, especially in the piedmont to have highs range from the lower 50s out in WV to mid 60s southside VA to the NC foothills. Could see a bust if the front is slower or faster and less or more rain occurs than forecast. Friday night-Saturday becomes tricky in terms of strength of high as cold air damming sets up lee of the Appalachians. The 1046 high over the Great Lakes Friday evening, crosses to New England by Saturday morning slightly weakening. Low pressure over the TN valley starts to lift northward bringing overrunning setup across the area with best coverage across WV and the Alleghany Highlands Friday night into early Saturday. Setup is such that cooler northeast to east flow will send temperatures to around freezing overnight Friday night into Saturday especially along the Blue Ridge north of Floyd/Roanoke/Bent Mountain, northwest to the Alleghanys in Craig County north to Bath. Warm nose aloft suggests more a freezing rain vs rain scenario though further north column may cool enough for sleet. At the moment too early for any headlines but will highlight in the HWO icing threat for the Blue Ridge and Alleghanys late Friday night into Saturday. Rest of the forecast area will see rain with best chances across the mountains. Temperatures Saturday southwest of the wedge will warm into the lower 50s, i.e. Chilhowie and Richlands, while most stay in the 40s, except cooler across the Blue Ridge north of Roanoke and the eastern slopes of the Alleghanys north of New Castle, VA. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... .AS OF 334 PM EST Wednesday... Amplified southern stream to take shape Sunday into next week with 2- 3 systems moving from the desert SW northward/northeastward to the upper MS Valley. Will start to see the cold air damming setup weaken by Sunday with frontal boundary over us weakening. Will still be on the cloudier side at times, but at the moment Monday looks like the driest day with highs in the 50s. Will see frontal boundary approach midweek with southwest flow increasing aloft keeping temperatures well above normal. Will see some showers scattered around Tuesday with better chance Wed-Wed night as the front tracks west of the Appalachians. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... As of 555 PM EST Wednesday... Overall outside of the exiting rain/drizzle near KLWB, conditions have briefly improved to VFR for early this evening. However a warm front will lift north across the region tonight resulting in another round of strong southwest winds aloft as the jet increases to around 50 kts overnight. This will again result in areas of low level wind shear espcly this evening so included a LLWS mention in most spots excluding KBLF where should see stronger surface winds. As the front moves north of the region a moist air mass will be left in place over some snow covered ground tonight into Thursday morning. Expect widespread fog and drizzle to develop as a result with attendant IFR-LIFR conditions at most TAF sites by midnight, then continuing through the remainder of the night. Latest ensemble HREF has the most widespread dense fog developing out east so expecting the lower vsbys and cigs to take shape there where more snow remains. Look for cigs and vsbys to rise Thursday morning with most locations returning to VFR during the afternoon. Winds will remain light in most areas overnight as the jet aloft skims across the top of the inversion and perhaps mixes down along the ridges from time to time. Southwest winds should increase as deeper warm air arrives Thursday with speeds at 10 to 20 kts including gusts perhaps to 30 kts Thursday afternoon. Medium to low confidence in ceilings, visibilities and winds through the valid TAF period. Extended Aviation Discussion... Little to no improvement is expected through the period. A backdoor frontal system will work its way south into the region Friday into Saturday, maintaining the threat for additional sub- VFR in low cigs along with light rain and/or drizzle. Unsettled weather will continue into Sunday with some slow improvement in conditions as high pressure wedges in from the north, but likely still MVFR cigs at best. Southerly flow will develop Monday ahead of a frontal system in the Central Plains with periods of MVFR possible mainly west where a few showers may occur. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH/KK SHORT TERM...WP LONG TERM...WP AVIATION...JH/KK/RAB
Area Forecast Discussion
National Weather Service Topeka KS
530 PM CST Wed Jan 11 2017 ...AVIATION UPDATE... .SHORT TERM...(This evening through Thursday) Issued at 317 PM CST Wed Jan 11 2017 Strong cold front was moving south through northeast Kansas this afternoon. Temperatures were down into the mid 20s at 3 pm this afternoon across the northwest part of the forecast area. The front should continue to move south through the area early this evening. Strong cold advection as shallow arctic airmass spreads across northeast Kansas tonight and Thursday. The weather should be dry but much colder tonight and Thursday with highs only reaching mid 20s to lower 30s on Thursday which is optimistic given the strength of the cold advection. The shallow and cold airmass will set the stage for serious forecast problems this weekend. .LONG TERM...(Thursday night through Wednesday) Issued at 317 PM CST Wed Jan 11 2017 Friday through Saturday, the intense upper low will be digging southeast off the southern CA coast, the upper low will then move east across northwest Mexico. Moisture at 850mb will begin to be transported northward from TX across western OK, then northeast across southeast KS. Increasing isentropic lift will cause freezing rain or freezing drizzle to develop northward from southern KS into the extreme southeast counties during the late afternoon hours. Low- level CAA may keep the northern edge of the freezing drizzle south of I-70 through the Friday night but I think some patchy light freezing drizzle may develop north of I-70 after midnight. The light freezing rain may continue on and off through the day Saturday southeast of I-35, with patchy freezing drizzle north across the remainder of the CWA. Ice accumulations of 0.1 to 0.2" may be possible across the southeast counties of the CWA. Ice accumulations will only be a trace up to 0.1" across the remainder of the CWA. Highs on Saturday will be in the 28 to 32 degree range. Saturday night through Sunday night, the upper low across northern Mexico will lift northeast into southwest KS. Deep gulf moisture will advect northward into KS while the shallow cold air remains in place. Temperatures will only drop off into the mid 20s but heavier precipitation will develop in the form of freezing rain which will continue through the day on Sunday. QPF across the CWA will be over an inch with up to 1.8" in some locations across the western and central counties. Given 850mb temperatures 5 to 9 deg C, there will be no sleet and ice accumulations across much of the CWA will range from 0.25" to 0.5". The GFS tries to warm temperatures into the mid to upper 30s through the day Sunday but the ECMWF keeps highs in the mid 20s to lower 30s. Given the northeast winds ahead of the sfc low in northwest OK, I`m going more with the ECMWF solution. There could be some major damage across the CWA due to ice accumulations. The surface low will gradually lift northeast into south central KS. Surface winds will advect warmer air northward ahead of the surface low across the eastern half of the CWA, and temperatures may slowly warm through the 30s and possible to near 40 by 12Z. The western counties of the CWA will probably remain under northeast and northerly surface winds which will keep temperatures at or slightly below freezing. Another 1 to 1.5 inches of QPF could occur across north central KS which could add 0.25" or 0.5" of ice accumulations. This will cause major damage to trees and powerlines across north central KS through Sunday night. Monday, the heavier precip should shift northeast of the CWA through the morning hours. Highs may reach to near 60 degrees across the southeast counties of the CWA during the morning hours, as the surface low moves northeast up the KS turnpike. The north central counties may change over to rain as temperatures slowly warm into the mid 30s. Given the total amount of QPF through the weekend into Monday, there could be some minor flooding of small stem streams and rivers. Monday night into Tuesday morning the upper low will lift northeast into IA and the wrap around moisture may turn to sleet and snow across the northern counties of the CWA. Any snow accumulations will be under 1 inch. Highs on Monday will be in the morning and temperatures will fall through the 40s into the 30s. && .AVIATION...(For the 00Z TAFS through 00Z Friday) Issued at 530 PM CST Wed Jan 11 2017 The RAP and NAM continue to show MVFR CIGS impacting northeast KS including TOP and FOE. It`s hard to see the stratus so I am not sure how far west it could spread. At this point, models keep the lower CIGS just east of MHK. So will take a wait and see approach to the low clouds for MHK. Forecast soundings suggest the clouds will hang on through mid morning before scattering out. Aside from the MVFR CIGS, no significant weather is expected through Thursday due to dry air in mid levels and no real strong forcing. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Johnson LONG TERM...Gargan AVIATION...Wolters