Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/13/18

Area Forecast Discussion
National Weather Service La Crosse WI
530 PM CST Mon Nov 12 2018 .SHORT TERM...(This evening through Wednesday night) Issued at 144 PM CST Mon Nov 12 2018 An upper level trough and embedded short wave trough moving south across the region this afternoon will drop south of the area tonight. This will push the remaining snow showers and flurries out of the area late this afternoon and do not plan to carry any mention of precipitation into tonight. The concern then becomes when will the clouds break up. Water vapor satellite shows decent subsidence in the wake of the upper level trough but visible satellite and observations indicate the clouds are holding on back across Minnesota into North Dakota, although there are some holes developing. Both the 12.12Z NAM and 12.17Z RAP hold a lot of moisture over the area at 925 mb through the evening. The NAM then pushes this out to the east as low level ridging builds in the west/southwest. The RAP is slower to push it out and suggest it may take into Tuesday after sunrise before it exits the region. However, looking at forecast soundings from the RAP, it does not show the moisture getting trapped underneath the inversion, so for now, will continue with the trend of the clouds clearing overnight but did slow it down some from the previous forecast. The ridge axis will slide southeast of the area Tuesday night allowing southwest flow to set up over the region. This will allow warmer air to start returning to the region with highs Wednesday to be above 32 for the entire area with a few spots topping the 40 degree mark. .LONG TERM...(Thursday through Monday) Issued at 144 PM CST Mon Nov 12 2018 The next chances for any precipitation look to be from Thursday night through Friday night. Northwest flow aloft looks to be setting up over the Upper Midwest for late in the week which will allow some short wave troughs to move across the region. These waves will push a cold front into the region with one area of low pressure expected to move by the area to the north Thursday night that could bring some light precipitation to parts of northern Wisconsin. Another area of low pressure could then develop along the front farther south and move across Iowa into Illinois Friday and Friday night possibly bring some precipitation to the southern parts of the area. Thursday looks to be the warmest day this week ahead of the cold front with highs reaching 30s and 40s. Cooler air behind the front will push highs back into the 20s and 30s for the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 530 PM CST Mon Nov 12 2018 The widespread stratus that has plagued the area for the past few days finally has a back edge just northwest of the area. Per current trends, it appears mainly VFR stratus (with a few possible breaks) will hang tight through the evening and early overnight hours, with erosion from the west occurring roughly around 07Z for RST and 09Z for LSE, though would expect some adjustment to those times as we go into the evening and peruse the latest satellite data. Ceilings could briefly slip to MVFR at RST, though that should be temporary, with high pressure building into the region and (hopefully) ensuring a return to clearer conditions into Tuesday. Winds will remain from the northwest either side of 10 knots tonight, gradually shifting westerly Tuesday afternoon. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...04 LONG TERM...04 AVIATION...Lawrence
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
536 PM CST Mon Nov 12 2018 .DISCUSSION...Updated for latest aviation discussion below. && .AVIATION...Increasing winds and lowering cloud decks are expected through much of the next 24 hours due to the passage of a cold front. KBRO Doppler radar shows light precipitation beginning to stream northeast out of neighboring Mexico, and the HRRR model suggests this will continue through late Tuesday afternoon. Pure VFR will be difficult to find through the next 24 hours. && .PREV DISCUSSION... /issued 246 PM CST Mon Nov 12 2018/ SHORT TERM (Tonight through Tuesday Night): The highly advertised strong cold front is currently making it`s way through the northern Ranchlands of Deep South Texas, at least at the time of this discussion. The front will continue to slide southward through the afternoon and evening. You will likely know when the front moves through as winds increase dramatically. Ahead of the front, some light and scattered drizzle/shower activity has developed. We had a few thundershowers earlier across Hidalgo and Kenedy Counties, however, much of the convection resides offshore this afternoon. Overall, models showed some QPF, but nothing to write home about. For sure the biggest story will be the winds and cool down behind the frontal boundary. Winds will be the strongest along the coast, however, as high pressure moves southward even inland locations will experience gusty conditions. Decided to extend the advisory west for all of coastal counties and issued SPS this AM to cover the I69C corridor. The highest wind gusts without a doubt will be right along the coast. In fact, Padre Island may experience some gusts close to 50 mph at times. With the increase in winds and dramatic drop in temps there comes some problems with wind chill values. Tuesday AM expect most areas to experience wind chills in the lower 30s, perhaps briefly lower. This of course brings higher concern for exposure. Temperatures on Tuesday do not get out of the 40s across the eastern CWFA. That said, if we are able to clear out the Ranchlands may break 50 degrees. Regardless temperatures will remain well below average. In fact, overnight lows Tuesday night and into Wednesday will be near freezing for much of the interior. LONG TERM (Wednesday through Monday): Freezing to near freezing temperatures Wednesday morning will quickly warm into the 40s by mid morning. Mostly sunny to partly cloudy skies will prevail Wednesday as surface high pressure settles across deep south Texas. High temperatures Wednesday will be in the 50s with light to moderate northwest to north winds. The combination of light winds and clear skies should provide good radiational cooling conditions Wednesday night. Low temperatures Wednesday night are expected to be about the same as Tuesday night, with lows in the 30s. Another freeze watch may be needed for Wednesday night as some locations may drop to around freezing Thursday morning. Record low temperatures for Thursday morning at Brownsville is 28 degrees and 38 degrees at McAllen. Also, wind chill values may still reach advisory criteria for a few hours Thursday morning as winds may remain around 5 mph or so. Surface high pressure across the area on Thursday will gradually move east Friday into Saturday. Temperatures will slowly modify over time, allowing for a modest warming trend. High temperatures will generally warm into the 60s on Thursday and the 70s Friday and Saturday. Moisture will begin to increase and pool across the region Saturday night as another front pushes south. Reinforcing high pressure may arrive for next Sunday or Monday. MARINE: (Tonight through Tuesday Night): Conditions are already on the decline across the marine zones. Buoy 42020 is already hitting Small Craft Advisory criteria. Given this, decided to go ahead and start the Gale Warning now as just up stream Gale conditions are being realized. Gale force winds and very hazardous seas are expected through Tuesday evening. Can`t rule out SCA conditions continuing through the overnight Tuesday through the end of the period. Simply put, extremely hazardous boating conditions through the short term can be expected for both the Laguna Madre and adjacent Gulf waters of Deep South Texas. Wednesday through Saturday: Strong north winds and elevated seas will support Small Craft Advisory conditions on Wednesday. Marine conditions quickly improve Wednesday night into Thursday as winds and seas steadily decrease as high pressure spreads over the area. && .BRO WATCHES/WARNINGS/ADVISORIES... TX...Wind Advisory until 6 PM CST Tuesday for TXZ251-254>257-351. Freeze Watch from late Tuesday night through Wednesday morning for TXZ248>254-353. GM...Gale Warning until 6 PM CST Tuesday for GMZ130-132-135-150-155- 170-175. && $$ This product is also available on the web at: HTTP://WEATHER.GOV/RGV
Area Forecast Discussion
National Weather Service Grand Rapids MI
1001 PM EST Mon Nov 12 2018 LATEST UPDATE... Update .SYNOPSIS... Issued at 252 PM EST Mon Nov 12 2018 An area of low pressure will track northeastward through the Central Appalachians tonight. This system will spread light snow into much of Southern Lower Michigan. This area of snow will diminish later at night but a colder airmass will be drawn down from the north for Tuesday and that should lead to lake effect snow showers mainly along the coast. High pressure moves in for Wednesday which will support dry conditions. && .UPDATE... Issued at 1000 PM EST Mon Nov 12 2018 Forecast is on track, with no planned changes to the ongoing headline. Synoptic snow is moving through at this time with accumulations that should be on the order of an inch or two at most. Flake size has been small and road surface temperatures are still slightly above freezing along and south of I-96. The synoptic snow should wind down between 1am and 4am, so we are looking at 3-6 more hours of light snow. Lake effect snows will continue to affect the lakeshore with a marked increase in intensity around 4am. Heavier snow is expected along the lakeshore south of Holland between 4am and noon Tuesday. The RAP shows strong convergence between 1000-900mb during much of that time. Travel along I-96 south of Holland and on I-94 west of Paw Paw late tonight and Tuesday morning will feature very low visibility at times due to heavier snow. && .DISCUSSION...(This evening through next Monday) Issued at 252 PM EST Mon Nov 12 2018 The main challenge in the period deals with the potential impacts tonight and whether headlines are needed. Models are in relative agreement in showing a band of synoptic snow arriving this evening from the southwest. Any accumulations from this area of snow should remain to the southeast of a Grand Rapids to Alma line. Mid level FGEN coupled with deep moisture through the DGZ does support the potential for minor accumulations. To start the temperatures this evening will be a little above freezing and values are not forecasted to fall below freezing until closer to midnight. Thus we are not thinking headlines are needed before midnight as most roads should remain wet. This area of snow moves out closer to midnight and that is when the lake effect snow risk rises. Based on a mainly north northwesterly flow it does look like the area south of Holland will see a potential for more impactful impacts. The snow showers should persist through the morning commute. With temperature predicted to fall several degrees below freezing later tonight a risk for an icy commute looks likely to happen. Thus we will issue a winter weather advisory for Allegan and Van Buren counties. These snow showers do move inland Tuesday morning. They are forecasted to weaken as they we will not issue any winter headlines east of the initial headline. That being said...there is potential for localized slick spots away from the lakeshore on Tuesday. Guidance shows high pressure moving for Wednesday so we are looking at a dry day. Subsidence and an airmass favoring less in the way of lake effect clouds will allow for a decent amount of sunshine. Another southern stream storm system could clip parts of Southern Lower Michigan mainly Thursday night with some snow/rain. Less in the way of cold air moves in behind this system so we are not expecting a repeat of tonights lake effect snow showers. The next storm system that may lead to impacts is show to move in on Saturday with snow. There is some lift and deeper moisture shown with this weak storm that tracks eastward through the state. Thus an increased risk for impacts exists. Temperatures will fall steadily behind this departing system for Saturday night into Sunday. Based on the forecasted winds behind this system the lake effect impacts could be aimed toward the southern end of Lake MI Saturday night into Sunday. We will need to monitor this closely in the coming days. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 725 PM EST Mon Nov 12 2018 Snow is beginning to spread into southern portions of the state at 00z. The snow will reduce visibilities into the 3-5sm range at TAF sites to the south and east of KGRR with 1-2sm visibilities for a time as well. Ceilings will be widespread MVFR through the night. The snow will taper off after 08z or so from west to east, but lake effect snow will begin to push in off of Lake Michigan after that time. The lake effect snow showers will be most prominent at KMKG and KAZO during the 12z to 18z time frame. On Tuesday, the MVFR ceilings in the morning lift to VFR late in the afternoon. Winds will be northerly tonight shifting to the northwest on Tuesday. && .MARINE... Issued at 252 PM EST Mon Nov 12 2018 The strengthening northerly flow on the backside of the departing low pressure system will support increasing northerly winds tonight. That coupled with cold air advection will generate larger waves out on the lake. Thus the small craft advisory will be allowed to continue for tonight through Tuesday night. With the arrival of high pressure for Wednesday...the winds will be weakening and shifting during that time. && .HYDROLOGY... Issued at 952 AM EST Mon Nov 12 2018 Rivers are mostly above normal for this time of year, though they are below bank full and levels are steady or falling. Most of the precipitation we will get over the next week will be frozen and fairly low-moisture, so rivers will continue to fall. Despite the cold weather, freeze-up ice jams are not a concern, as water temperatures in the main-stem rivers are still well above freezing. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 11 AM EST Tuesday for MIZ064-071. LM...Small Craft Advisory until 7 AM EST Wednesday for LMZ844>849. && $$ UPDATE...Duke SYNOPSIS...MJS DISCUSSION...MJS AVIATION...Duke HYDROLOGY...63 MARINE...MJS
Area Forecast Discussion
National Weather Service Lincoln IL
856 PM CST Mon Nov 12 2018 .UPDATE... Issued at 845 PM CST Mon Nov 12 2018 ILX radar indicates the main band of frontogenetical forcing was shifting southeast along the I-72 corridor this evening. This lines up well with the latest RAP forecast in taking the better area of lift to the southeast with time this evening. Snowfall amounts have generally been trace amounts across the far north to a half inch to 1 inch across central into east central IL. We expect the main area of lift to push into far southeast IL late tonight and then east out of our area during the early morning hours. Forecast soundings continue to suggest a loss of ice crystals as deep layer moisture decreases with time late tonight, especially along and southeast of the I-70 corridor. In addition, time-height cross sections indicate some weak lift lingers in the low to mid levels of the atmosphere which may bring about a brief period of snow which will mix with or change over freezing drizzle before the precipitation moves off to our east by Tuesday morning. Further north, much colder air will filter southeast into the region with early morning lows dropping into the low to mid teens with wind chills in the single digits. Tuesday should be quiet with sunshine and temperatures well below normal for the middle of November as highs struggle to reach 30 degrees (normal highs for Nov 13th should be in the low to mid 50s). The current forecast has a good handle on the forecast for the remainder of the evening and overnight hours. As a result, no ZFP update is needed at this time. && .SHORT TERM...(This evening through Tuesday) ISSUED AT 304 PM CST Mon Nov 12 2018 A surface cold front has pushed south of the Ohio River with temperatures leveled off since late morning today, poised to drop sharply overnight as cold air to the northwest continues to push into the area. Meanwhile, bands of weak frontogenetical forcing aloft continue over central IL producing light snow over most areas from I-72 northward, which should be shifting southeastward through the late evening. South of I-72, a mix of rain and snow looks likely this afternoon, with mostly rain south of I-70. This evening into the early morning hours, some mix of freezing drizzle and snow is possible mainly south of I-70 as temperature continue to cool off but cloud ice crystals diminish as moisture depth decreases. Ground temperatures are still slightly above freezing with air temperatures hovering near the freezing mark limiting accumulations so far, however heavier snowfall rates and cooling temperatures should allow accumulations to start this afternoon and continue into the evening. Expecting around 1 inch throughout the I-72 corridor which looks to be the best combination of cooler temperatures and heavier snowfall rates, with lesser amounts to the north and south, generally little or no accumulation most areas northwest of the Illinois River and south of I-70. Lows tonight are expected to reach 15 in Galesburg ranging up to 26 in Lawrenceville. Wind chill temperatures by morning should range from lower single digits northwest of the Illinois River to the teens south of I-70. Breezy, cold, and clear conditions are expected Tuesday as northwest winds 10-15 mph combine with highs in the upper 20s and lower 30s, as the current weather system moves off to the east. Wind chill temperatures will be in the teens to low 20s or lower through the day. .LONG TERM...(Tuesday night through Monday) ISSUED AT 304 PM CST Mon Nov 12 2018 The upper level trough over the intermountain west looks to slowly progress eastward and close off over the southern Plain midweek, eventually developing precipitation associated with a deformation zone as it merges with the main large scale trough over the northeastern U.S. Progression of this feature will still be subject to some timing and track adjustments, however models are in relatively good agreement with the 12Z cycle that this precip should target areas from around I-72 southeastward early Thursday morning into Thursday night, possibly as far northwestward as the Illinois River. Temperatures will be cool enough for snow or a mix of rain and snow over the area. Light amounts to perhaps a couple inches are possible depending on timing of the system and whether snow falls in the day or nighttime. Expect highs mainly in the 30s and lows in the 20s Wednesday night through Thursday night, after one more cold night Tuesday night with temperatures dropping into the upper teens most areas. Another cold front looks to push across the area from the northwest over the weekend, bringing a period of light rain or snow, as well as dropping temperatures again, from highs in the 40s Friday, back down to the 30s Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 522 PM CST Mon Nov 12 2018 The weather system producing the snow across the TAF sites early this evening is expected to push off to our east late this evening with the snow ending and the IFR/MVFR cigs becoming VFR from northwest to southeast in the 00z-05z time frame. Vsbys will occasionally lower to 3/4sm in snow for a few hours early this evening, especially in DEC and CMI before conditions start to rapidly improve in those areas. VFR conditions will prevail on Tuesday. Northwest winds are expected during this forecast period at speeds of from 10 to 15 kts. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Smith SHORT TERM...37 LONG TERM...37 AVIATION...Smith
Area Forecast Discussion
National Weather Service Northern Indiana
647 PM EST Mon Nov 12 2018 .SYNOPSIS... Issued at 307 PM EST Mon Nov 12 2018 Light snow will spread across most of the region this evening with up to an inch of accumulation in many areas by daybreak. More concentrated snow amounts are expected closer to Lake Michigan where 2 to 4 inches of lake effect snow may fall with locally higher amounts possible through Tuesday afternoon. Below normal temperatures will continue this week into the upcoming weekend. There is another chance for rain or snow Thursday afternoon and evening. && .SHORT TERM...(This Evening through Tuesday) Issued at 307 PM EST Mon Nov 12 2018 Area of precipitation continues to expand from across NW parts of our area southwest into IL and MO. Have been seeing periodic reports of drizzle or light rain and expect this to expand through the remainder of the afternoon. As we get towards evening, falling temperatures will allow more of a mixture and eventually transition to all snow. While it may start to accumulate on grassy areas, will need to wait till closer to 6Z for at/below freezing temps to let road impacts start. Main axis of concentrated precip seems to be favoring more NW (which seems on track considering blossoming area over the NW) where cross sections show good isentropic lift and alignment of omega. These do stay below favorable snow growth zones which will limit flake size and accumulation potential. Have increased pops further NW late afternoon into tonight but for now not increased QPF a lot. By evening, may be a dusting or so in grassy areas with up to an inch of snow across the area during the evening as large area of light snow moves through in response to deepening low pressure to the east of the area. Locally higher pockets of accums will occur as noted by several upstream sites occasionally dropping to 1/4-1/2 SM. Greater amounts will occur from formation of mesobanding this evening and then lake effect across Berrien and LaPorte county later tonight into Tuesday. After collaboration with GRR, opted to hoist Winter Weather Advisory for Berrien county from 5Z tonight through 15Z to cover greatest impacts during morning rush hour as 1-3" of snow may have fallen by this point to make for slick spots. While no other areas will be included in headlines, the lighter snow amounts may raise havoc as well as melting and re- freezing of snow occurs and causes patchy black ice. Snow showers will continue into Tuesday morning before tapering off. Another inch or 2 is possible with NW alignment of lake effect across Berrien and La Porte counties as well as somewhat inland. By afternoon majority of snow will come to an end. && .LONG TERM...(Tuesday Night through Monday) Issued at 307 PM EST Mon Nov 12 2018 Piece of energy from departing shortwave will quickly cut-off Tuesday night over Texas, ejecting northeast into Kentucky by Thursday night. While much of the energy will be transfered to rapid cyclogenesis on the east coast a period of wrap-around/deformation precipitation will expand across the northern Ohio Valley and back into portions of the area mainly Thursday night. Specifics remain to be determined, but much like today an area of light mixed precip should arrive Thurs afternoon and then quickly transition to all snow Tuesday night with potential for around a quarter inch or so of QPF. Despite some mesoband potential, thermal profiles not stellar for good accumulation potential with ratios of less than 10:1 possible. Some chance for lake effect will move in for the weekend, but lack of better moisture will likely limit anything substantial. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 636 PM EST Mon Nov 12 2018 Conditions will continue to deteriorate this evening as light snow spreads across the area. VFR will drop to MVFR early this evening with pockets of IFR at times within heavier areas of snow. Should see improvement in visibility toward 06z as fast moving system departs and synoptic snow diminishes. Quick transition to lake effect snow expected for overnight and first part of Tuesday. As always, difficult to nail down band location and timing at KSBN. Models still have some differences on band orientation but favored HRRR model in depicting potential restrictions at KSBN near daybreak with a shore parallel band coming south. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...Winter Weather Advisory from midnight tonight to 11 AM EST Tuesday for MIZ077. OH...NONE. LM...Small Craft Advisory until 4 AM EST Wednesday for LMZ043-046. && $$ SYNOPSIS...Lashley SHORT TERM...Fisher LONG TERM...Fisher AVIATION...Lashley Visit us at Follow us on Facebook...Twitter...and YouTube at:
National Weather Service Jackson KY
948 PM EST Mon Nov 12 2018 .UPDATE... Issued at 946 PM EST MON NOV 12 2018 Rain is starting to fill back in across the northern portion of the CWA, and latest radar trends show a slight uptick of radar returns elsewhere that would support rain continuing to fill in over the remainder of the CWA as well. Made some minor adjustments to the pop forecast, but otherwise, the forecast seems to be in good shape. Also loaded in the latest observations for temps and winds to make sure the near term grids were on track with the current conditions. Reworked a portion of the overnight diurnal curve as well based on the current temperature trends. All updates have been published and sent to NDFD/web. Another refresh of the temps and winds, along with a resent of the forecast package will be done once the obs are available just after 10pm. UPDATE Issued at 557 PM EST MON NOV 12 2018 Some dry air has moved into the region behind an exiting cold front, cutting off the precip across much of eastern Kentucky from west to east. Precip is expected to fill back in overnight as a secondary boundary moves eastward through the region, but even this should remain quite light and could be patchy in some locations. Given the considerable downward trend in pops late this afternoon/early this afternoon, redid the pops through this time period to better reflect the current radar trends as well as the latest high-res models. Kept likely pops in for the late night/early morning as this second system moves through, but since some of the Hi-res models are showing some patchy coverage, did not feel confident enough to go categorical. Also loaded in the latest observations for the temps and winds to make sure the near term grids were on track with the current conditions. This resulted in some minor updates to the overnight diurnal curve as well, though did not make any changes to the overnight low temperature for now. All updates have been published and sent to NDFD/web. A new forecast package was also sent out to reflect these changes. && .SHORT TERM...(This evening through Tuesday night) Issued at 335 PM EST MON NOV 12 2018 20z sfc analysis shows low pressure coming out of the northern Gulf riding northeast south of Kentucky as a cold front approaches from the northwest. This system has pushed a chilly rain shield into eastern Kentucky today steadily moving north out of Tennessee. The clouds and rain have kept temperatures from climbing much today with mid afternoon readings in the upper 30s north to the low 40s in the south. Dewpoints are in lock step with the temperatures for the south and in the mid 30s north. Winds, meanwhile, are light and generally from the northeast to east. The models remains in decent agreement aloft through the short term portion of the forecast. They all depict the continued evolution of the troughing over the Southern Plains as it remains unphased with the northern stream and proceeds to cut off over the lower Mississippi Valley by Wednesday morning. Meanwhile the northern stream trough works quickly east through the Great Lakes with minimal height falls across Kentucky, but an ample stream of energy from the southern closing off trough will ride overhead in fast southwest flow. A few periods of stronger upper level divergence can be expected during the short term - especially this afternoon and late tonight - as a strengthening 300mb jet streak develops southwest to northeast across the Ohio Valley. Given the good agreement and steady trends have favored a model blend but with a strong lean toward the higher resolution NAM12 and HRRR for details. Sensible weather will feature chilly rains - of some significance in the south - running through the evening and into the overnight. The duration will lead to some healthy totals of an inch or so in the far south to around a quarter of an inch in the northwest. This will be the main weather from this particular system that had much promise last week for bringing the area some early season snow. As such, cold air will now trail the rain`s departure Tuesday allowing it to stay liquid as it ends for most places, though some mix of wintry weather will be possible at the highest points in the southeast for Tuesday evening. Most likely this will be just some flakes but limited ice crystals in the column could produce pockets freezing rain - though measurable chances are very small so have kept it out of the grids and zones for now. A very cold night follows into Wednesday morning with lows down in the mid to upper 20s from the arriving Canadian high pressure system and its CAA. Again started the grids with the CONSShort and ShortBlend ones with some minor adjustments to point temperatures through the period. As for PoPs, beefed them up through the overnight period and held them up in the higher terrain of the far east Tuesday afternoon and evening. .LONG TERM...(Wednesday through Monday) Issued at 310 PM EST MON NOV 12 2018 A shortwave trough will push across east Kentucky Wednesday night and Thursday, bringing another round of wet weather to the area. Temperatures on Wednesday will struggle to reach 40 as clouds increase ahead of the approaching system. How much temperatures cool into Wednesday night will be the biggest question mark impacting this forecast package. Temperatures will likely fall to around freezing during the evening hours as precipitation starts to spread in from the south. A strong warm nose aloft will be present supporting mainly liquid through the event. Thus, the question will reside around surface temperatures. Its possible valley locations could decouple into Wednesday evening, allowing them better potential to start off at or below freezing. The better shot for freezing rain may be from the Cumberland plateau, northward into central and northern Kentucky. Southeast Kentucky may stay just above freezing, but again, this will be a complex temperatures forecast and early wet bulbing could help to push the surface temperatures cooler at the onset of this event. For now, main threat appears to the freezing rain as the warm nose aloft will prevent much snow or sleet. Will introduce the freezing rain threat into the HWO this afternoon as the primary threat. As we head into the overnight and Thursday morning hours, temperatures will start to warm as we see latent heating with the falling rain and warm air advection developing with the warm sector of the system. A cold front will then sweep across the area Thursday afternoon/evening, bringing a cool surge of air back into the region. This may allow lingering rain showers to mix with and change over to snow. Fortunately, the better lift will be departing as the colder air arrives, so limited precipitation rates and warmer ground should limit any potential snow accumulations. Upper level pattern will become more zonal as the shortwave trough departs by Friday. With surface ridging spreading across the area, quiet weather will be seen from Friday through Saturday night. Uncertainty increases by late next weekend as a clipper type system could impact the area by late Sunday or Sunday night. However, models are all over the place with various scenarios, so stayed very close to the blended model guidance this afternoon. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 723 PM EST MON NOV 12 2018 After a cold front and associated rain moved through this afternoon, some dry slotting has now taken hold, with only isolated to scattered showers present across much of eastern KY. A secondary system will move through later tonight, with rain expected to spread across the TAF sites once again. This rain should be light, but may still drop VIS to MVFR at times. Tried to time out onset of rain and associated impacts for each TAF site. CIGS are currently variable across the CWA, with some sites reporting below airport mins, and others, like SYM who are MVFR to VFR. As such, expect CIGS to fluctuate somewhat overnight, but the general trend should be towards LIFR or IFR, especially as the second wave of moisture moves in. Rain will taper off after daybreak Tuesday as this system moves east of the state, allowing a much drier airmass to take hold from the west. This will quickly cut off rain chances, though MVFR clouds may stick around through much of the day. Winds will generally remain light and variable overnight, becoming north between 5 and 10 knots through the day Tuesday. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...GREIF LONG TERM...KAS AVIATION...JMW
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
828 PM CST Mon Nov 12 2018 .UPDATE... Issued at 817 PM CST Mon Nov 12 2018 The back edge of the snow is lingering longer than expected. While the snow is pretty light, it is accumulating. We picked up about a .2 inch here at the forecast office in Weldon Spring since 00Z. The RAP keeps insisting that the low level frontogenesis will continue to push southeast of the I-70 corridor down into southeast Missouri over the next hour or two, and there is a general decreasing trend on radar and a slow southeast movement to the back edge of the snow. Am therefore leaving the northern portion of the winter weather advisory as is with the expectation that this trend will continue. However, there is plenty of frontogenesis lingering over southeast Missouri into the overnight hours. With that in mind, have extended the advisory for our southeast Missouri counties until 200 AM. Carney && .SHORT TERM... (Through Late Tuesday Afternoon) Issued at 227 PM CST Mon Nov 12 2018 System to exit region late tonight. In the meantime, ongoing snow will persist, gradually tapering off from west to east. Model soundings, especially over portions of southeast Missouri and southwestern Illinois, still indicating loss of ice crystals aloft, so could still see some very light drizzle/freezing drizzle, in this area with a light glazing possible. Storm total snowfall of 1 to 2 inches with locally higher amounts still looks good for forecast area by the time this comes to an end. Kept Winter Weather Advisory going til 9 pm. As for low temperatures, they will be in the teens to low 20s. On Tuesday, sunny skies return to the region. Despite this, temperatures will remain below normal with highs only in the upper 20s to low 30s. Byrd .LONG TERM... (Tuesday Night through Next Monday) Issued at 227 PM CST Mon Nov 12 2018 (Tuesday Night - Wednesday) Very cold night is in store on Tuesday night as ridge of arctic high pressure remains anchored across the bi-state area. Combination of a clear sky and a light/variable wind should promote nearly ideal conditions for radiational cooling. There could also be just enough snow cover across parts of south-central Missouri to help cool temperatures another few degrees if these locations can manage to keep a sufficiently deep snow cover through the day on Tuesday. Regardless, most of the arctic airmass itself is cold enough to yield low temperatures in the teens areawide. Leaned at or below the cooler MET guidance for lows across parts of south-central and southeast Missouri and near model consensus for the rest of the CWA. While temperatures are expected to moderate slightly on Wednesday into the mid to upper 30s, this is still about 20 degrees below normal for the date. (Wednesday Night - Thursday) All eyes for the Wednesday night and Thursday time period will be on mid/upper level cutoff low that forms near the Arklatex region. As alluded to yesterday, these cutoff lows are typically very difficult to forecast in terms of both track and timing. Compared to yesterday, there is however more confidence in this system impacting the CWA with the potential for significant snowfall (3+ inches). However, even a slight shift in when the cutoff low ejects out and its eventual track could have very large ramifications on sensible weather output. Currently, based on the track of this upcoming system, it appears that portions of southeast Missouri and southwest Illinois would have the highest chances at seeing the most snowfall. While there are still some concerns about precipitation type, it does appear that the dry/cold antecedent conditions associated with the previous arctic air mass and dynamic cooling should yield mostly snow wherever the deformation zone moves through. Speaking of the track of the system, model consensus of the 850-hPa low tracks is roughly from KMEM late Wednesday night into the lower Ohio Valley late on Thursday. Previous research (Browne and Younkin - 1970) has shown the heaviest snow axis to be approximately 90 nautical miles (~105 miles) to the left of the track of the 850-hPa low. Given the strength of this system and the fact that it continues to deepen into the day on Thursday, this may be a case where the heaviest axis of snow is just a bit further to the northwest (say closer to 120-130 miles). This would favor the heaviest snow axis in the CWA roughly from KFAM to just northwest of KSLO. An early look at NWP soundings show a classic heavy signature with maximum lift centered in a saturated dendritic growth zone (-12 to - 18C). Elevated instability is also noted in this same layer very late Wednesday night into Thursday morning as isentropes fold over or decrease with height. Below the ice crystal growth zone, there is a deep isothermal layer around -5C from the surface to near 700 hPa which suggests dendrites would tend to aggregate. To top it all off, wind speeds are fairly light throughout the column to prevent fracturing of snowflakes. In summation, snow-to-liquid ratios may be fairly high (above 12:1) which would help to increase snowfall totals. (Thursday Night - Next Monday) Behind this next system, northwest flow aloft will establish itself. A cold front is still expected to move through the region on Friday night into early Saturday. Temperatures should reach into the upper 40s on Friday ahead of the cold front. While this likely will be the warmest day of the extended, those highs would still be some 5-10 degrees below normal. Slightly cooler weather is then favored behind the aforementioned cold front for this upcoming weekend as another strong surface high settles into the region. Forecast high temperatures this weekend should be mainly in the 30s before a slight moderation occurs next Monday as high pressure settles into the lower Mississippi Valley with southerly return flow returning to the bi-state area. Gosselin && .AVIATION... (For the 00z TAFs through 00z Tuesday Evening) Issued at 525 PM CST Mon Nov 12 2018 The storm system moving across the region is winding down at this time. Most locations are already reporting VFR visibility with a few patches of left over MVFR. Visibility should continue to improve through the evening, though MVFR ceilings will likely persist for several more hours from central into eastern Missouri and southwest/south central Illinois. There will also be some lingering light snow/flurries or possibly some patchy freezing drizzle. The clouds should lift across the area from northwest to southeast through the late evening into the early overnight hours, and then scatter out before sunrise Tuesday. VFR flight conditions are expected thereafter. SPECIFICS FOR KSTL: Think accumulating snow is mostly over for the St. Louis area. However, occasional light snow or flurries, and perhaps a brief period of freezing drizzle is still likely into the early evening hours. MVFR flight conditions with cigs below 2000 feet are likely to prevail for the rest of the evening. Latest radar trends may indicate a little increase in the snow intensity over what is in the TAF, so MVFR visibility for the first hour may need to be extended. The precipitation is still expected to end by mid evening, and flight conditions should improve to VFR overnight. VFR conditions are expected to prevail thereafter. Carney && .PRELIMINARY POINT TEMPS/POPS... Saint Louis 20 30 20 38 / 80 0 0 0 Quincy 15 28 17 39 / 5 0 0 0 Columbia 15 30 15 39 / 30 0 0 0 Jefferson City 17 31 14 39 / 60 0 0 0 Salem 24 31 19 38 / 90 0 0 0 Farmington 20 30 16 37 / 90 0 0 0 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...Winter Weather Advisory until 2 AM CST Tuesday for Crawford MO- Iron MO-Madison MO-Reynolds MO-Saint Francois MO-Sainte Genevieve MO-Washington MO. Winter Weather Advisory until 9 PM CST this evening for Boone MO- Callaway MO-Cole MO-Franklin MO-Gasconade MO-Jefferson MO- Lincoln MO-Moniteau MO-Montgomery MO-Osage MO-Saint Charles MO-Saint Louis City MO-Saint Louis MO-Warren MO. IL...Winter Weather Advisory until 2 AM CST Tuesday for Randolph IL. Winter Weather Advisory until 9 PM CST this evening for Calhoun IL-Jersey IL-Madison IL-Monroe IL-Saint Clair IL. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Medford OR
806 PM PST Mon Nov 12 2018 .DISCUSSION...Current satellite imagery is showing some high cirrus clouds moving over southern Oregon and northern California from west to east. Overall, the airmass will be persistent to what occurred last night, and temperatures will be very similar to what occurred last night across the area. The only question will be whether or not the cirrus clouds will move slow enough to keep temperatures a bit warmer than last night. Have dropped temperatures a little bit tonight from the day shift, but not as low as they were last night due to these clouds. Otherwise, the forecast is on track, and am not making changes. -Schaaf && .MARINE...Updated 800 PM PST Monday 12 November 2018...Southerly winds will continue through Wednesday as a weak front approaches. This front will very slowly move into the area and thus sub-advisory south winds and seas continue through Tuesday. The front finally moves onshore Wednesday, and we`re not expecting any significant impacts to the coastal waters until late Wednesday night or Thursday morning when a steep westerly swell around 10 feet moves in behind the front. A thermal trough and northerly winds develop Wednesday night into Thursday. Steep combined seas are possible on Thursday due to a combination of west swell and wind seas. Small craft advisory level winds are also possible on Thursday, mainly south of Cape Blanco in the waters beyond 10 nm from shore. Steep seas and areas of gusty northerly winds may persist into Friday as the thermal trough remains in place along the coast. -CC/Keene && .PREV DISCUSSION... /Issued 405 PM PST Mon Nov 12 2018/ DISCUSSION...A high pressure ridge is in place today bringing warm daytime temperatures and dry conditions. A weak front will approach the area tonight and Tuesday, then weaken further as it moves inland on Wednesday. There is only a slight chance for light rain along the coast. Elsewhere expect dry weather to continue and the front will only bring some clouds into the area Wedensday. Of note, ahead of the front expect southerly winds to develop over the area Tuesday. This may result in some patchy smoke moving into the area from fires to the south. Current high resolution forecasts from the HRRR indicate smoke expected to move into Siskiyou and Modoc counties during the day Tuesday, then patchy smoke or haze may spread into portions of southern Oregon Tuesday afternoon and Tuesday evening. Winds become more westerly on Wednesday though so any smoke that moves into the area may shift east on Wednesday. Behind the front, a high pressure ridge will rebuild over the region Thursday into the weekend. This will bring continued warm daytime temperatures and dry weather to the area through at least Sunday. AVIATION...For the 13/00Z TAFs...VFR will prevail across the forecast area, outside of the Umpqua Basin, for the next 24 hours. Shallow moisture in the Umpqua Valley will likely bring local IFR/LIFR ceilings/visibility back to Roseburg again late tonight/Tuesday morning. These IFR/LIFR conditions will improve to VFR by late Tuesday morning. Keene/Spilde FIRE WEATHER...Conditions will remain critically dry through Wednesday morning, then improve. But, humidities will not be high and no rain is expected over the next 7 to 8 days, through Tuesday. East to southeast winds have decreased today. They will increase slightly at inland locations tonight and continue at 5 to 15 mph into early Tuesday morning, while southerly winds develop at the coast and continue into Tuesday evening. These weak to moderate wind speeds will not reach Red Flag Warning criteria, but relative humidity recoveries both tonight and Tuesday night will be poor to moderate again over the higher terrain across the region. Recoveries will be worst in Siskiyou County. The improvement in conditions on Wednesday will be due to a very weak front that will bring a slight chance of very light rain to the coast then pass through the area late Tuesday in Wednesday. Despite the improvement, conditions will still be drier than normal. Mild and dry weather will persist through the forecast period, with light east winds returning Wednesday night. East winds will continue through the weekend. Strength of winds later in the week through early next week is uncertain, but they are unlikely to be as strong as during this past weekend`s episode. The pattern may finally change and bring a chance of rain beyond day 7. -DW && .MFR WATCHES/WARNINGS/ADVISORIES... OR...None. CA...None. Pacific Coastal Waters...None. $$
Area Forecast Discussion
National Weather Service Paducah KY
554 PM CST Mon Nov 12 2018 .UPDATE... Issued at 553 PM CST Mon Nov 12 2018 Updated aviation discussion for 00Z TAFs. && .SHORT TERM...(Tonight through Wednesday) Issued at 227 PM CST Mon Nov 12 2018 Initial reports out of southeast Missouri (mainly Butler and Carter counties), indicate some sleet falling in the narrow precipitation band moving into southwest Illinois. Surface temperatures are in the lower 40s with surface dewpoints in 25 to 30 degree range. The RAP soundings and cross sections through this area suggest a saturated sub-freezing layer above 800 mb with a drier layer below 800 mb. Ice crystal and snow aggregation above 800 mb is allowing precipitation to fall through a sub-freezing layer near 2kft agl (with some loss in size of due to evaporation). Some sleet development is occurring in the lowest 2kft over southeast Missouri. As boundary layer saturates and wet bulb values increase, some of the precipitation will change over to rain during the evening. As the evening progresses, we will a loss of moisture from the dendritic snow growth layer, leading toward a combination of sleet, then freezing rain through midnight over southeast Missouri and southwest Illinois. The best lift moves east of southeast Missouri and southwest Illinois prior to midnight, reducing any substantial lift through the moist layer. With surface temperatures and road temperatures expected to be in the upper 30s to lower 40s, most of the wintry precipitation should run off as liquid through at least 9 pm over southeast Missouri and southwest Illinois. Subfreezing temperatures will moving southeast from the foothills of southeast Missouri and into southwest Illinois beginning around 10 pm CST, working toward the Ohio River and the Confluence of the Mississippi and Ohio River by 3 am CST. By the time the sub-freezing temperatures move south of the Ohio, nearly all of the precipitation will be gone from the WFO PAH forecast area. Will update the Special Weather Statement and Hazardous Weather Outlook this afternoon to reflect a better timing and coverage area of the wintry precipitation for later this afternoon and tonight. .LONG TERM...(Wednesday Night through Monday) Issued at 227 PM CST Mon Nov 12 2018 Fairly high confidence in a storm system moving through Mid week. Timing and the amount of Precipitation as well as type still remain a little in question. One thing is consistent and that is a low over the southwest will lift northeast into the lower Ohio Valley. This has been persistent over the last several days. The exact path and timing has been in question but the model solution continue to close the gap on the solution and timing. The latest model runs show the GFS has slowed a bit bringing it closer to the ECMWF/Canadian solutions. The exact path still remains in question with the GFS taking a sudden shift to the east as it enters our cwa. In contrast the ECMWF takes it right through the center of the forecast area. The path of the Canadian is a little in between with the path of the low. We will likely start out with a wintry mix Wednesday night and slowly change over to mainly snow. Temperatures will warm during the day Thursday to the upper 30s to lower 40s. This will change any thing that falls over to liquid/rain. Thursday night as temperatures begin to fall the rain will likely change back over to snow. However it should also be departing the area with little additional impact. The main impact would likely be the morning commute Thursday morning as temperatures will still remain below freezing. This could result in hazardous driving conditions...especially on any untreated roads as well as any bridges or overpasses. The area should dry out Friday and into the weekend. However we will be in a northwest flow aloft with a weak cold front set to move through Saturday. So we could see some precipitation. However the forecast sounding indicate a very dry air mass over the area. So anything that does fall will have little if any impact. As we head into next week a surface high will be moving through the gulf states and finally return a warmer southerly flow to the area. There is another perturbations in the northwest flow Sunday into Sunday night but again forecast soundings have a very dry air mass over the region so little impact expected then as well. We will encounter a little warmer temperatures toward the end of the week with high well into the 40s and approaching 50 in some locations. This will still be below normal temperatures. Normals range from the middle 50s for highs and the middle 30s for lows and should not reach those values. && .AVIATION... Issued at 553 PM CST Mon Nov 12 2018 Scattered to numerous light rain showers will continue across the region through the evening. Some of the rain may be mixed with light snow or light sleet at times, especially over portions of southeast Missouri and southern Illinois as temperatures cool. The loss of ice nucleation around midnight will transition remaining precipitation to drizzle. While not included in the current TAF forecast, there remains a small chance of freezing drizzle after midnight as temperatures drop below the freezing mark. Primarily VFR ceilings will lower to MVFR through the evening and hold there through Tuesday morning. A gradual west-to-east improvement to VFR is expected from mid morning through early afternoon with partial clearing. Prevailing north winds around 10 knots will gust to 20 knots at times. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ UPDATE...RyanP SHORT TERM...Smith LONG TERM...KH AVIATION...RyanP
Area Forecast Discussion
National Weather Service Blacksburg VA
659 PM EST Mon Nov 12 2018 .SYNOPSIS... Low pressure from the Gulf will track over the region tonight, reaching the New England coast Tuesday. Meanwhile, a cold front entering the Ohio Valley will move east and stall along the coast Tuesday night. Low pressure will develop along the front over the southeast United States Wednesday night and track through the Mid Atlantic region Thursday. && .NEAR TERM /THROUGH TUESDAY/... As of 642 PM EST Monday...Falling into an in-situ wedge, a shield of steady moderate to at times heavy stratiform rains continue to advance across the eastern two-thirds of the forecast area. Other than potentially at Boone where radar may be underestimating somewhat, hourly rain rates from mesonet and ASOS sites have been almost half as much as what surrounding radar accumulations are indicating, a consequence of overestimation from bright banding. Most of these hourly accumulations have been to the tune of a quarter to at most a third of an inch. Look for rains to continue to progress east/northeast as the evening progresses, with a general decrease in ongoing rains from west to east through 04z/11 PM. As reflected in the HRRR and some of the 18z forecast guidance, next round of steady light to moderate rains should progress into areas along/east of Highway 29 into the overnight hrs, while areas further west, from the Blue Ridge westward, should see more intermittent light rains at worst. These trends already reflected well in the forecast. As of this writing, already starting to see a turn made toward gradual rises along gaged points on the Dan River, but still well below action stage levels. A continued gradual rise can be expected on most main stem rivers, though the Dan is at risk of experiencing the greatest forecast rises. Will continue to monitor. Otherwise, have used a blend of most raw 2m temperatures into the going forecast to essentially show temperatures showing little up-or-down trend through midnight, before warm advection induces a slow rise in most locales overnight. Previous discussion from 232 PM Monday follows... The wedge of cooler air remains over the area and has strengthens some due to adiabatic (easterly upslope) and diabatic (evaporative) cooling processes. Unfortunately, temperatures will not make it out of the 40s with some mountain valleys remaining in the 30s. The big ticket item for today will be how much rain the area will see into tonight. With warm moisture air advecting over the wedge, strong isentropic lift and channel vorticity will result in around an inch of rain along and south of the VA/NC border this afternoon. Along the highway 460 corridor, a half to three- quarters /0.50-0.75/ of an inches is expected. A range of a quarter to a half /0.25-0.50/ of an inch is possible across the Greenbrier Valley to the Alleghany Highlands. The wedge may still be in play this evening and will erode once a surface low develops over the coastal piedmont of North Carolina and tracks to the Virginia coast overnight. PWATS increase to 2-3 standard deviations above normal this evening as the original disturbance brings Gulf moisture, then adds a strong fetch from the Atlantic. Heavy rain potential remains over the northwest North Carolina and Southside Virginia this evening with another inch of rain is possible. Amounts taper overnight heading west to a half to three-quarters /0.50-0.75/ of an inches towards the Blue Ridge and a quarter to a half /0.25-0.50/ of an inch across the Bluefield area and southeastern West Virginia. The moderate to heavy rain will move east of the area through the early morning hours as the low quickly races northeast of the area. If 2-3 inches or more of rain falls over the area, areal flooding of creeks and streams is possible, river flooding is likely to follow within 12-24 hours along the Dan River, maybe the Roanoke River. Rainfall rates and amounts will determine if areal flood warnings are warranted this evening. The main area of concern will be along the VA-NC border. The surface low tracks off the Delmarva Coast Tuesday morning. A weak cold front will then slide across the region, bring additional light rain showers to the area. Rain will taper off from west to east in the afternoon as the front moves to the coast. Overcast skies will likely remain through the day with high temperatures recovering into the mid to upper 40s across the mountains and lower 50s east. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 245 PM EST Monday... Tuesday evening the far southwest portion of the area will be receiving the tail end of the exiting line of showers associated with the departing cold front. Western Greenbrier County will start to experience northwest upslope flow, residual moisture and falling temperatures to yield some isolated snow showers. Both regions of light precipitation are expected to end by midnight. Dry high pressure will make a brief visit to the area Wednesday morning. By the afternoon, light precipitation will start to overspread this high pressure from the south. This precipitation, in the form of light rain, will primarily only impact the Northern Mountains of North Carolina through sunset. Wednesday night into Thursday, precipitation will continue to overspread the area on the eastern flanks of an area of low pressure moving eastward through the mid-Mississippi River Valley. A strong, deep, southeast fetch of moisture off the Atlantic will develop. This moisture will only help to enhance the nose of high pressure east of the crest of the Blue Ridge, helping to keep surface temperatures on the cool to cold side, all while bringing a nose of warmer air over the region not too far off the surface. The result will be about an 18 hour period where a decent portion of the forecast area will be receiving freezing rain to at least some accretion. Highest amounts are expected to be along and near the crest of the Blue Ridge thanks to enhanced precipitation totals here where the effect of a southeast upslope flow will maximize precipitation totals. Given how far out in time this event still is, will be using a fairly conservative 33% ice versus WPC QPF totals. Even doing this results in some storm total ice amounts at or a little above the quarter-inch threshold in the aforementioned favored areas, with at least a few hundredths of an inch for a vast majority of the forecast area save parts of Southside Virginia and north central North Carolina, and far southwest Virginia towards Richlands. This trend upward in ice totals matches well with the trend offered by WPC as reflected in their most recent 3-day ice accretion totals. While we are forecasting for the early part of Thursday rain versus freezing rain, sleet could also be falling over parts of the area currently forecast for freezing rain. To keep the forecast simple that far out, we try not to offer more than one winter weather type at a time in the forecast, but either freezing or snow. With the warm nose in place, freezing rain, where warranted, is the better choice of the two. However, as we get closer to the date in question, and sleet looks more probable where freezing rain currently is forecast, this alteration would lower the currently forecast ice accretion totals. By Thursday afternoon, the entire region looks warm enough for plain rain, albeit a cold rain. Thursday night, the parent upper low is expected to be moving along the Mason Dixon line, bring its associated trough axis and cold front through our region. This transition will shunt the warm nose to our east as cold air advection streams into the area on progressively gusty northwest winds. This will result in a transition to scattered rain/snow showers across mainly western sections of the area. During this portion of the forecast low temperatures will average around normal. However, high temperatures will be about 10 degrees below normal on Wednesday, and about 15-20 degrees below normal. Forecast confidence is moderate on the general transition of the weather patterns during this portion of the forecast. However, confidence regarding the specific precipitation types and amounts Wednesday night into early Thursday are still in question and likely will flucuation between now and then. What is of high confidence is some type of wintry mix other than just rain versus snow is expected during this time period, raising the flag for the strong potential for a Winter Weather headline for portions of the area. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 1230 PM EST Monday... Friday morning an upper low will be making headway eastward through the Upper Ohio River Valley with its associated trough axis extending southward into a portion of our forecast area. A timing challenge within the models exists to pinpoint just where this axis will be at the start of the day. However, the general trend of the day will be for any lingering precipitation in the east from the Thursday/Thursday Night system to be exiting the region, or to dissipate thanks to increasing northwest, downsloping, winds across the eastern parts of the area. Across the west, these same gusty northwest winds will allow for a period of upslope scattered snow/rain showers across portions of southeast West Virginia. Heading into and through the weekend, a general northwest flow pattern will continue across the area, but but with notably weaker speeds. Very isolated lingering rain/snow showers will be possible across parts of southeast West Virginia Friday night through Sunday. Sunday night into Monday models vary as to the degree which a cold front will impact our region. Our latest forecast will reflect a consensus of the guidance which yields isolated rain/snow showers from roughly the Blue Ridge and points west Sunday night and isolated rain showers across the southeastern sections of the area on Monday. Temperatures during this portion of the forecast are not expected to show a lot of variation, although there will be a slightly trend lower by the second half of the weekend post-cold front. Readings on average will be just a few degrees below normal. Forecast confidence is highest on Friday, at moderate confidence, and trends downhill heading into Monday. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 659 PM EST Monday... Aviators can expect poor flight conditions through early Tuesday morning due to sub-VFR ceilings/visbys, mountain obstruction and areas of wind shear above wedge inversion around 3000 feet. Steady, at times heavy rain with mist producing visbys commonly in the 2-5 SM range will continue to progress across the eastern two thirds of the airspace. As initial frontal wave low moves northeast, this rain should begin to decrease in intensity from west to east through about 04z, though fog/mist and low ceilings (IFR to LIFR at times) likely to persist until early Tuesday morning. Winds mainly northeast at 3-8 kts, though increasing southerly low-level jet and directional shear through the 925-700 mb level indicates potential for wind shear in the Piedmont/foothills for late evening and overnight. Already some instances of light/moderate shear being reported in PIREPs across the Piedmont of central/southern NC. Should see MVFR-IFR ceilings continuing into Tuesday morning as the next weak wave of low pressure brings renewed chances for MVFR-VFR rains. Looks like areas along/east of the Blue Ridge stand the greatest potential for rain through mid-afternoon. While winds likely tend variable for the first part of Tuesday, as this secondary wave exits, look for a wind shift to northwest late in the TAF period to around 4-8 kts. Forecast confidence is high on poor flight conditions and categories, but is moderate to low on timing category changes. Extended Discussion... Look for ceilings to trend VFR from the Blue Ridge eastward thanks to downsloping winds overnight, but lingering sub-VFR ceilings along with intermittent upslope snow showers possible between KBLF-KLWB. Another area of low pressure develops along the front on Wednesday and brings deep moisture back into the Mid Atlantic region later Wednesday into Thursday. Sub-VFR possible in rain and areas of wintry mix Wednesday night into early Thursday espcly across the mountains. This storm system is expected to exit the region by Friday with conditions returning to VFR with the exception of residual upslope snow showers on the western slopes of the central Appalachians. Forecast confidence above average Tuesday and average Wednesday through Friday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RCS NEAR TERM...AL/RCS SHORT TERM...DS LONG TERM...DS AVIATION...AL/RCS
Area Forecast Discussion
National Weather Service Sacramento CA
225 PM PST Mon Nov 12 2018 .SYNOPSIS... Dry weather continues with cool nights and near to above normal high temperatures through the week. Diminishing winds ease critical fire weather conditions this week, but widespread smoke from the Camp Fire will continue to impact the area. && .DISCUSSION... Ridge axis along the coast shifts inland tonight as a weakening trof moves into the mean ridge position. High cloudiness forecast to drift inland over Norcal on Tue, exiting the area on Wed. The cloud cover will likely not impact min temps significantly as the dry air mass will result in strong radiational cooling. Also does not appear the smoke layer is having too much of an impact especially as it shifts gradually overnight with the downslope/drainage winds. RHs recovered very well from MYV-MOD and with similar conditions expected this coming night from last night, expect some dew/frost may form in this area again by Tue morning. Otherwise the dry air mass will preclude widespread heavy dew/frost, although there is some moisture in the ground from local watering. Persistent upper ridging over Norcal will result in light/lighter winds over Norcal and limited mixing heights (1 kft - 1.5 kft), due to the time of the year, will tend to keep persistent smoke over a large portion of the CWA for the next couple of days. Satellite indicates some improvement on the east side of the CWA with the help of downslope flow overnight. But during the day, with light winds, upslope flow may carry some smoke back to the east again through evening. Smoke may also spread towards RDD per the HRRR smoke loop through this evening. With no major changes in the wx pattern during the short term, little change expected in the forecast. Smoke might help to keep temperatures cooler the next couple of days, otherwise they will continue to run above normal, especially in the far Nrn portion of the CWA where they are less impacted by smoke. High temps will be in the 60s to mid 70s for the Central Valley, with mostly 50s to 60s for the foothills and mountains. Cold overnight temperatures are expected mainly over the Central Sacramento Valley southward, with lows in the 30s to low 40s. Lows will be in the teens to mid 20s across mountain basin locations. JHM && .EXTENDED DISCUSSION (Friday THROUGH Monday) Broad upper ridge forecast to continue across the region later in the week maintaining dry weather with mild days and cool nights, and no strong wind events are expected. Forecast guidance is indicating the possibility of a pattern change as an upper trough approaches the area early next week. Big question is will the cut-off low approaching the region next week bring any chance of rain to Norcal. 12/12z GFS weaker and farther south than the 12/00z ECMWF Mon/Tue next week, and the 12/12z ECMWF following suit, but also showing a Nrn stream trof bringing precip to Norcal next Tue. These differences yield low confidence in model solutions at this time. JHM && .AVIATION... Widespread MVFR likely the next 24 hours across the entire Sacramento Valley with local IFR for the southern terminals due to smoke from the Butte County wildfire. Northerly winds under 10 knots. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$