Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/13/18

Area Forecast Discussion
National Weather Service Burlington VT
911 PM EST Fri Jan 12 2018 .SYNOPSIS... Today`s record warmth will be short-lived as a strong cold front across the St. Lawrence Valley late this afternoon moves steadily southeastward across the region this evening and overnight. Temperatures will very rapidly fall below freezing with passage of the front. Meanwhile, a developing low pressure system will track northeastward along the frontal boundary, bringing heavy mixed wintry precipitation to the region tonight through Saturday morning. Periods of heavy snow and sleet are expected, with localized ice accumulations up to a quarter inch across south-central Vermont. Difficult and icy travel conditions are expected areawide, especially late tonight and Saturday morning. Conditions will trend colder and drier for Sunday and Monday. There is a chance for additional snowfall Tuesday into Wednesday of next week. && .NEAR TERM /THROUGH SATURDAY NIGHT/... As of 911 PM EST Friday...Minor changes to the previous forecast for the late evening update, mainly to attempt to match temperature and ptype trends. I say attempt because I`ve been chasing temps/ptype for the past 3 hours as conditions remain very changeable. Last few runs of the HRRR have a had a good handle on the thermal profile though with the sub-freezing air at the surface-925mb ahead of 850mb but aloft temps are catching up with snow being reported from KSLK westward, sleet at KPBG/KFSO, and still rain eastward. Changeover to snow still looks on track for the northern Champlain Valley in the 1-3AM timeframe, central Vermont a couple hours later, and not until closer to 8AM for southern Vermont. In the hours preceding the snow, a mix of rain, sleet and snow is all possible. Total snow and ice accumulations still appear to be on track, but I expect them to be widely variable by the time the storm wraps up tomorrow afternoon. Previous Discussion...Very dynamic weather pattern in place with near record to record warm temperatures / dewpoints/ and precipitable water values across the North Country this afternoon. High of 61F thus far at BTV, with a few locations 63-64F across wrn VT. In addition to the warm temperatures, dewpoints have reached the mid 50s. Along with gusty south winds and patchy fog, this has quickly eroded almost all of the existing snowpack at lower elevations, with significant loses at higher elevations per webcams (high of 53F at the Mt. Mansfield summit). Additional light to moderate rainfall into this evening and runoff will maintain the threat of river and ice jam flooding through tonight. Flood watch continues thru 12Z Saturday. Please refer to ongoing flood warnings for additional details. Next issue is the moderate to heavy mixed precipitation moving in during tonight. Sfc cold front with an extreme low-level temperature gradient was shifting sewd into the St. Lawrence Valley at 20Z. Temperatures will drop 10-20 deg / 2hr with the frontal passage, and will gradually be transitioning to mixed wintry precipitation by 22Z at KMSS, and by 01-02Z around BTV with N-NW wind shift. We`ll be seeing a "flash freeze" situation tonight, where temperatures dive sharply below freezing and any standing water will quickly freeze on roads and sidewalks. Will make for increasingly icy road sfc conditions from NW-SE as cold air sweeps in, even beneath the falling snow/sleet overnight. We`ve been monitoring the vigorous mid-level shortwave trough across the Tennessee river valley...which will shift newd along the frontal zone during the overnight hours. Excellent warm conveyor belt across nrn FL/GA/SC (1.8" PW values) will contribute to strong moisture advection and lift back across the frontal zone late tonight into Saturday morning, as the frontal zone bisects VT from SW-NE during the predawn hrs. Combined with frontogenetic forcing, should see periods of heavy mixed wintry precipitation, especially 06-15Z Saturday. No changes to the ongoing winter weather headlines, with Winter Storm Warnings across nrn NY into central/nrn VT, and Winter Weather Advisories for Rutland/Windsor/Orange counties. Will see freezing rain of brief duration across nrn NY and the nrn Champlain Vly (1-2 hrs), followed by sleet and snow. Snow will be of longest duration across nrn NY where favorably cold thermal profiles arrive first. Have 6-10" snowfall across nrn NY, with localized amts to 12" possible. Greater mixing with sleet in the Champlain Valley and n- central VT supports 4-8" snow/sleet, with a few spots maybe up to 10" along the intl border area in nwrn VT. South and east of a line from St. Johnsbury to Montpelier to Rutland, looking for more freezing rain (around 0.25" possible) and reduced snow/sleet accumulations of 2-4" with the prolonged icing. May see isolated power outages with the freezing rain across central/s-central VT, but overall ice loading not sufficient for widespread power issues based on current indications. Will also see strong north winds of 15- 30 mph develop across the Champlain Valley with low-level channeling of colder air filtering into the valley overnight. Strongest winds will be near the srn end of Lake Champlain, where valley narrows considerably. As surface frontal wave low pulls away across the Gulf of Maine, we`ll see lingering trowal/comma head snowfall across the Adirondacks and nrn VT through about 16-18Z, before exiting quickly to the north and east. Thus, should see snow winding down by early afternoon with some improvement to travel conditions later in the day along with partial clearing late afternoon into Saturday night. Temperatures will be sharply colder, with lows in the single digits across nrn NY and teens across VT, except low 20s far southeast. Temperatures rise just a few degrees on Saturday, and then we`ll see lows of -5 to -15F Saturday Night, and locally near -20F for Saranac Lake (KSLK). && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 346 PM EST Friday...Strong 1040 mb high pressure will moves slowly across the area Sunday while a weak short wave trof aloft moves by without any fanfare. So Sunday looks to be mostly sunny and quite cold with highs from the lower single numbers in the north to low teens in southeast VT. Mainly clear skies and calm winds Sunday night will allow temps to fall to 10 to 20 below with a few outliers either side of that. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 346 PM EST Friday...A very active long term forecast period is in store with a deepening long wave trof over the CONUS. Models start out in reasonable agreement with the trof closing off as it moves southeast across the great lakes with ridging aloft over our region and high pressure persists at the surface. However, the evolution of the trof and surface low pressure is quite different as it approaches the northeast US Wed-Thu. GFS/CMC has a positive tilt trof with the surface low out to sea east of the mid-Atlantic coast while the ECMWF develops a new closed low off the mid-Atlantic coast and the surface low right up the coast toward New England and into the Gulf of ME. Result is rather low confidence in the Wed-Fri time frame so for now keeping snow showers in the forecast through that period regardless as one way or another the upper trof should bring a chance of precip. Temperatures start out on the cold side Monday with high pressure but return closer to seasonable levels for the rest of the week. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... Through 00Z Sunday...IFR/MVFR through the next 24 hours as steady rain transitions to mixed precipitation and/or all snow as temperatures drop sharply. Winds trending north/northwesterly and modestly gusty from 15 to 25 kts, abating by Saturday afternoon. Higher coverage of snow to occur at northern NY terminals of KMSS and KSLK, with a longer period of mixed precipitation at KPBG and moreso at Vermont terminals before the change to snow later tonight. Steadier snows then taper off by late morning into the afternoon hours on Saturday as CIGS gradually improve. Outlook... Saturday Night: VFR. NO SIG WX. Sunday: VFR. NO SIG WX. Sunday Night: VFR. NO SIG WX. Martin Luther King Jr Day: VFR. NO SIG WX. Monday Night: Mainly VFR, with local MVFR possible. Chance SHSN. Tuesday: Mainly MVFR, with local IFR possible. Chance SHSN. Tuesday Night: Mainly MVFR, with areas VFR possible. Chance SHSN. Wednesday: Mainly MVFR, with areas VFR possible. Chance SN. && .HYDROLOGY... Flood watch has been issued from 12z Today to 12z Saturday for the combination of snow melt, rainfall, and ice jams causing localized flooding on area streams and rivers. The greatest threat for ice jam or main steam flooding includes but not limited to the following rivers: the Ausable, Mad, Missisquoi, and Lamoille Rivers, along with the Otter Creek. Continued concern for isolated ice jams - mainly today into tonight from a 36-48hr period of above freezing temps with max temps into the 50s. River ice breakup will not be widespread, but it appears that the mild temperatures will exist long enough to get some river ice movement across the North Country. Thus, rivers will need to be watched during this time frame. We are anticipating accumulated thawing degree hours between 400-500 by this evening, with temperatures today in the upper 40s to mid 50s, before a cold frontal passage this evening. Preliminary ice thickness reports/estimates indicate most rivers have ice less than a foot thick, with some of the northern waterways having ice perhaps as much as 18 inches thick in spots. As a general rule, river rises of 2-3x the ice thickness is needed to breakup river ice. Given potential QPF 0.50-1.50" and snowpack SWE 2-4 inches, there is certainly some threat of getting river rises on the order of 2-4 feet, with crests most likely this evening. If river ice movement does occur, issues may linger into Saturday, even as temperatures drop back below freezing behind the cold front. Persons with interests along rivers should continue to monitor this developing situation. && .CLIMATE... Record Highs for January 12th: Burlington, VT......55F.....1980. (New Record: 61F so far today) Montpelier,VT.......53F.....2017. St. Johnsbury, VT...54F.....1980. Massena, VT.........50F.....2017. (New Record: 57F so far today) && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Flood Watch until 7 AM EST Saturday for VTZ001>012-016>019. Winter Storm Warning until 4 PM EST Saturday for VTZ001>009- 016>018. Winter Weather Advisory until 4 PM EST Saturday for VTZ010>012- 019. NY...Flood Watch until 7 AM EST Saturday for NYZ026>031-034-035-087. Winter Storm Warning until 4 PM EST Saturday for NYZ026>031- 034-035-087. && $$ SYNOPSIS...Banacos NEAR TERM...Banacos/Lahiff SHORT TERM...Sisson LONG TERM...Sisson AVIATION...JMG HYDROLOGY...Banacos/Hastings/Taber CLIMATE...Banacos
Area Forecast Discussion
National Weather Service State College PA
515 PM EST Fri Jan 12 2018 .SYNOPSIS... A very sharp cold front will push gradually southeast across Central Pennsylvania today and tonight. A developing wave of low pressure on the front will track across southeast Pa late tonight. A deep upper level trough will swing through the region this weekend into the middle of next week, then lift out by the end of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Numerous near-short term forecast POP/weather/temp and precip type grids were heavily weighted twd the latest - 18Z RAP model which concurs nicely with the very sharp sfc cold front extending from near KBFD to just east of KFKL and KPIT at 1930Z. Extremely sharp temp drops of 25+ deg F (from the low 60s to the mid 30s) were occurring within just 2 hours of its passage. As an example...KAGC is currently 62F while KPIT is down to 34F. The front is expected to be just west of the I99/rt 15 corridor north of KIPT around 23Z today. Little change in timing or precip type and its transition to FZRA -> PL and Snow has been made following a multi model blend of high res data and Meso/SREF/GEFS guidance. Snowfall totals were modified only slightly and remain a general 1-2 inches below WPC amounts as it appears there could be a slightly more prolonged period of -fzra and sleet before a changeover to snow this evening across the NW mtns, and tonight elsewhere. Prev Disc for late today through tonight... It`s our understanding that roads crews will not be focused on, since the significant (and in some parts of Western PA - Heavy) rain overnight/this morning, and around an additional 0.50 inch of QPF before the changeover, would be washed off and ineffective in this particular high impact winter weather event. The sharp drop in temp after the cold fropa and continued precip in the form of signif sleet and/or fzra rain across the central valleys, and sleet to several inches or more of snow across the NW mtns late today and tonight, will lead to a CLASSIC FLASH FREEZE case with very hazardous travel conditions developing quickly. Showery/mild weather will remain across much of the Susq Valley for the rest of the day. Deep southerly flow ahead of approaching cold front will continue to flood the region with unseasonably mild air late this afternoon/early this evening, with temps from the upper 50s near the Allegheny front to the mid 60s over the southeast portion of the forecast area. Latest models continue to indicate a ptype changeover to mixed precip across northwest Pa this evening, as low level cold air undercuts deep/moist southerly flow in advance of shortwave lifting up the Appalachians. As surface low tracks across southeast Pa late tonight, confidence is high for a few to several hour period of heavy snow across northwest Pa in association with fgen forcing within thermally direct jet entrance region of a 150+ kt upper jet situated across srn Ontario and Lake Erie. Model Blend and WPC Guidance continues to support a high confidence of 6-9 inches across Warren/Mckean counties, with a few hours of 1 inch/hour rates likely around midnight. The heavy snow will be preceded by a transition from rain to wintry mix which will shift to the southeast with time. The shallow cold air will initially undercut the warm/moist air with a significant icing zone possible over parts of Central PA before changing to snow as cold air deepens through the column. Based on model soundings and WPC guidance, believe fzra will be fairly short-lived with sleet a more predominant ptype before eventual change to snow early Sat morning. A very messy start to the weekend for sure, with a glaze of ice and coating of snow/sleet possible as far southeast as the Lower Susq Valley. Mins temps by morning will likely vary from the single digits across the NW mtns (with wind chills in the single digits below zero) to near 30F in the far SE. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... Expect any lingering light snow/flurries to taper off by late Saturday morning, as upper level shortwave and associated surface low lifts rapidly northeast of PA. An additional coating to 1.5 inches of snow is all that should occur between 12-15Z Saturday, and that will be almost exclusively confined across the mtns North and NE of KIPT. Much colder air will continue to pour into the state on a gusty north-northwest flow in the wake of this system Saturday. SREF plumes indicate very little rise from early AM temps and highs only in the teens over the NW Mtns to low 30s across the southeast counties. Dry, arctic air and low inversion heights should limit lake effect activity to mainly just flurries across the western mountains Saturday afternoon and night. Main concern will be low wchills Sat night. Current indications are for apparent temps close to advisory levels over the northern mountains Sat night. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Saturday night and Sunday will be cold and windy post-storm as strong high pressure builds in from the GLAKS. Monday will start quiet but a clipper spreads light snow into the area Monday night and Tuesday followed by cold and dry conditions into Thursday. Monday night`s clipper could be accompanied by squalls. Pattern may amplify again by next weekend with milder flow ahead of vigorous shortwave and storm ejecting from the Rockies to the Upper Midwest Sat-Sun with strong FROPA possible over PA on Monday. && .AVIATION /22Z FRIDAY THROUGH WEDNESDAY/... Periods of rain along with MVFR to IFR restrictions and gusty south winds are continuing to move into the region with the heaviest bands through the western half of PA. The latest radar is showing some mixed precipitation through at PIT and BFD is a little above freezing. So there will be a changeover to a wintry mix over the next few hours. Precipitation will mix to snow from northwest to southeast this evening. Latest models have the 02Z in the NW to 12Z through the SE. Winds will shift abruptly from south/southeast to northwest with the passage of a strong cold front. LLWS everywhere prior to the cfropa. Low ceilings and reduced visibilities expected to persist overnight and into Saturday as well as gusty N-NW winds, with improving weather for late Saturday. Outlook... Sat...AM rain/low cigs poss east. AM snow/ice poss central/west. Sun...No sig wx expected. Mon...PM light snow poss west. PM low cigs poss east. Tue...Morning snow ending. Becoming VFR south and east, lingering snow showers and restrictions over the mountains. && .HYDROLOGY... A mild surge in temperatures combined with 1-3 inches of rain from Thursday afternoon through late Friday will produce significant rises on rivers and streams with the potential for ice jams and low- lying flooding. Streamflows are currently low, but many waterways are choked with ice. The greatest risk of flooding is in the Watch area over north- central PA where snowmelt will be a contributing factor today. && .CTP WATCHES/WARNINGS/ADVISORIES... Flood Watch through Saturday evening for PAZ004>006-010>012- 017>019-037-041-042-045-046-049>053. Winter Weather Advisory until 10 AM EST Saturday for PAZ012- 017>019-024>027-033-037-041-042-045-046-049>053. Winter Weather Advisory from midnight tonight to 10 AM EST Saturday for PAZ028-034>036-056>059-063>066. Winter Storm Warning until 10 AM EST Saturday for PAZ006-010- 011. Winter Storm Warning until 10 AM EST Saturday for PAZ004-005. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Fitzgerald/Lambert LONG TERM...Ross/DeVoir/RXR AVIATION...Lambert/Ceru HYDROLOGY...
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
916 PM EST Fri Jan 12 2018 .SYNOPSIS... A cold front will sweep east across the area tonight, with gradually drier and colder high pressure settling in from the north through the weekend. Another cold front will cross the region Tuesday through Tuesday night, ushering in even colder air from mid to late next week. && .NEAR TERM /THROUGH SATURDAY/... 900 PM EST Update...No major changes needed to the fcst grids. Light precip still exiting the far ern zones and linger across the NC mtns. Snow showers will begin to develop along the wrn mtns with no sigfnt accums thru the next update. 630 PM EST Update...Made some tweaks to PoPs and temps/tds as the pattern remains quickly progressive. On-going stream flood conds across ern Transylvania County will persist overnight...however no new areas will be under the gun for any hydro concerns. As of 225 PM: Low pressure is approaching the Appalachian chain from the west, along a cold front extending from Quebec to the central Gulf Coast. Preceding this front, a plume of moisture is bringing a broad area of showers to the western Carolinas and Georgia within the warm sector of the system. Up to a couple hundred joules of SBCAPE has developed in our eastern and southern zones, with effective bulk shear of 40 to 50 kt thanks to the very deep trough to our west. Accordingly 0-3km bulk shear is in excess of 100 m2/s2 in some of the same area. We have been anticipating a small severe threat in these portions of our CWFA, and we have not yet written off that possibility late this afternoon. RAP/HRRR suggest as 850mb jet moves over the Piedmont later this afternoon, the more vigorous activity now over SE GA and the SC Midlands will track NE, possibly developing QLCS features. The threat is greatest between 21z and 00z, per HRRR and HREF. In particular, the latest HRRR depicts some streaks of elevated updraft helicity moving through the southern I-77 corridor, which agrees with current radar trends. Lightning has been basically nonexistent within today`s upstream activity so thunder mention is extremely limited in the fcst. Following the departure of the aforementioned precip, low level moisture will linger over the NC mountains for some time. Cold advection will get underway up there in the 00-03z timeframe; while some dynamic forcing will still be in play with the upper low skirting by just to the northwest, the turn to NW winds will be the primary source of lift. Models differ as to how the cold advection affects low-level temperatures; namely the NAM depicts the low levels cooling much more quickly than the layer above the PBL, which leads it to produce a warm nose that the RAP and especially GFS don`t show. Accordingly, the NAM suggests a brief period of wintry mix in some areas instead of a clean rain-snow transition like we would typically see in NW flow. This seems improbable overall, but a brief mention of FZRA was included (per Bourgouin p-type technique) further away from the spine of the mtns, where the warmer air is most likely to still be in place. However this does not result in more than a trace of ice. Overall the moisture is fairly shallow and winds are not particularly impressive despite the strength of the front. Thus snow amounts are not expected to exceed an inch except in the highest elevations of the Smokies. We will issue an SPS to cover the small threat that black ice will occur where roads remain wet as the subfreezing temps return overnight. Gusty winds and falling dewpoints may be enough to dry the roads. With downsloping, mixing and initially moist conditions, most of the Piedmont looks to remain above freezing overnight. The northwest flow snowfall should peak in the early morning, though the setup suggests at least flurries will linger through most of the day in the favored areas. Gusty winds will continue through the day but still look unlikely to reach advisory criteria. Max temps will be at or below freezing in the mountains, and mainly in the 40s in the Piedmont. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As of 235 PM EST Friday: Guidance showing a relatively tranquil yet cold short term Sunday and Monday. Winds will diminish Saturday night as high pressure builds in from the north behind the departing cold front. The high remains ridged into the area from the north on Monday. The air mass associated with the high is cold with lows around 10 degrees below normal both nights. Highs Sunday will be 10 to 15 degrees below normal then rise a few degrees on Monday. Wind chill values will drop to around zero across the higher elevations Saturday night but will be warmer Sunday night with less wind. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 305 PM EST Friday: Guidance in general agreement through the medium range. Upper low over the Great Lakes Monday night opens up and moves east on Tuesday as a short wave digs into the MS Valley. This short wave closes off an upper low and moves it near the VA/NC border Wednesday then to our east Wednesday night. At the surface, ridge of high pressure moves east of the area as a cold front moves toward the spine of the Appalachians Monday night and into the mountains Tuesday. The front moves east of the area Tuesday night but a trough of low pressure forms in the wake of a surface wave developing along the front. This trough forms near the Savannah River Tuesday night and moves north across the area Wednesday. The guidance shows an H85 low forming in the lee of the mountains as well with quite a bit of moisture. The southerly H85 flow develops isentropic lift and some frontogenesis creating enough lift for precip to develop. There could even be some weak instability Wednesday helping kick off shower activity. The temps behind this front are very cold, H85 temps 2 standard deviations below normal on the GEFS mean, which would help the precip change to snow for much of the area. The GEFS mean shows a good chance of precip developing with accumulating snow, generally 2 inches or less, with this system. Since the GFS, GEFS mean, and the ECMWF are all in decent agreement, have gone with low chance PoP for the forecast area Wednesday. Despite the agreement, there is still quite a bit of uncertainty with this forecast as all these elements have to come together at the right time for this scenario to develop. Temps increase Tuesday ahead of the front before falling well below normal for Wednesday behind it. Temps remain well below normal for Thursday with drying conditions as the cold air mass in place. Temps warm to near normal for Friday as the air mass quickly moderates and heights rise. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: Lingering -shra will persist over the terminals with limited restrictions remaining thru 03z. Mainly MVFR CIGS/VSBY outside the NC mtns. Dry air will work in overnight and clouds will begin to scatter out most locales. Good gust potential beginning arnd midnight mtn valleys and near daybreak elsewhere as the p/grad tightens along with some measure of llvl CAA. No sigfnt VSBY concerns are had with sfc winds keeping things mixed. VFR conds will persist thru the day Saturday with only FEW/SCT mid to upper clouds. Outlook: VFR and cold conditions are expected to prevail through early next week. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT Med 73% High 93% High 100% High 100% KGSP High 80% High 100% High 100% High 100% KAVL Med 72% High 92% High 100% High 100% KHKY High 92% High 98% High 100% High 100% KGMU High 93% High 100% High 100% High 100% KAND High 97% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...HG NEAR TERM...SBK/Wimberley SHORT TERM...RWH LONG TERM...RWH AVIATION...SBK
Area Forecast Discussion
National Weather Service Indianapolis IN
950 PM EST Fri Jan 12 2018 .UPDATE... The AVIATION Section has been updated below. && .SYNOPSIS... Issued at 228 PM EST Fri Jan 12 2018 Snow will come to an end this evening across central Indiana as a Low Pressure exits the area. Cold...Arctic high pressure over the upper midwest will then build across Central Indiana and the Ohio valley through the weekend...bringing very cold but dry winter weather. A quick moving Low pressure system is then expected to push in to the Western Great lakes on Sunday night....pushing a cold front across Indiana on Monday. This will bring another round of snow to central Indiana. Yet another arctic will arrive across Central Indiana on Tuesday. This will continue the dry and cold weather for much of the next work week. && .NEAR TERM /Tonight/... Issued at 228 PM EST Fri Jan 12 2018 Surface Analysis early this afternoon shows lows pressure over West Virginia...with a cold front stretching from Western New York...SW along the Appalachian Mountains to NW Georgia. Water Vapor shows an upper low over Western Kentucky...pivoting northeast...still providing southerly flow aloft to Central Indiana. Radar shows snow showers overspreading Central Indiana stretching in a band from Vincennes and Terre Haute east to a Winchester-Greensburg line. Current band across the area suggests a deformation zone like configuration...and accumulating snows will be expected the next several hours as the band slowly edges eastward. Ongoing Snow will continue to impact the evening rush hours. Cold northerly surface flow was in place across Central Indiana...with temps in the middle 20s flowing across the forecast area. GFS and NAM suggest the upper low will continue to slide eastward this afternoon and tonight...and the southerly flow aloft of moisture will be lost as it is diverted to the east. This will bring an end to the precipitation across Central Indiana shortly after 00Z. HRRR is in pretty good agreement wit this...sliding the back edge of the precip to the southeastern counties by 00Z. Forecast soundings show dry air arriving within the column near 00Z and impressive drying and subsidence arriving by 03Z as the flow aloft shifts to the north on the backside of the upper system. Thus will keeps some snow chances through the afternoon and early evening across the area...but best chances will be across the southeast as the system departs. Will try and trend toward a dry forecast by midnight as the dry air previously mentioned will be well in place. Given the ongoing Cold air advection and the fresh snow...will trend lows overnight at or below the forecast builder blend. && .SHORT TERM /Saturday through Monday/... Issued at 228 PM EST Fri Jan 12 2018 Quiet weather will be anticipated on Saturday through Sunday. The GFS and NAM show mainly a cold NW flow...slowly transitioning to westerly through Sunday. Little in the way of upper support will be pushing across the area through Sunday. Meanwhile at the surface...High pressure looks to remain in place across the area...slowly progressing east of Indiana by late Sunday. During this time forecast soundings and time height show a dry column with subsidence...which should be expected given the dry...polar air mass. Thus will trend toward Partly clouds and trend temps at or below the forecast builder blend through Sunday. On Sunday night and Monday...the GFS Shows a strong wave aloft over the Northern Plains poised to push southeast into the Ohio Valley. Models suggest an associated well organized surface low and cold front arriving in Central Indiana on Monday. Return flow on the backside of the departing high should allow some limited moisture return...however given the cold air mass...large amounts of moisture will not be needed for snowfall. Forecast soundings show a saturated column as the cold front approaches and passes on Sunday Night and Monday with excellent saturation within the -10C to -20C layer. Thus confidence is high for an accumulating snow as this system passes...however we would not be surprised to see slight changes to the timing in the next few models runs. Nonetheless will include high pops for snow on Sunday night...particularly after midnight...and on Monday. && .LONG TERM /Monday Night Through Friday/... Issued at 235 PM EST Fri Jan 12 2018 Models are close enough that the model blend initialization was accepted for most items. Much of the long term will be dominated by upper troughing across the eastern USA. The north to northwest flow will allow Arctic air to move into the area. Snow cover refreshed by the Monday system will aid in bringing temperatures down. By the end of the long term, temperatures will moderate as upper flow relaxes and becomes more zonal. Some lingering snow may continue in the east Monday evening. A few lake enhanced snow showers may make it into the far northwest around Tuesday. Otherwise the long term will be dry. && .AVIATION /Discussion for the 13/03Z TAF Update/... Issued at 949 PM EST Fri Jan 12 2018 Update... Increased winds at KIND and extended MVFR conditions through Sat 07Z. Previous Discussion... MVFR conditions with a few lingering snow showers will continue through Sat 03Z. After that, VFR should become the prevailing flight category for the remainder of the TAF period. The main threat will be the strong northerly winds. Sustained speeds will range between 17 to 22 kts with gusts up to 31 kts through Sat 11Z. && .IND WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 10 PM EST this evening for INZ021- 028>031-035>049-051>057-060. Winter Storm Warning until 10 PM EST this evening for INZ061>065- 067>072. && $$ SYNOPSIS...Puma NEAR TERM...Puma SHORT TERM...Puma LONG TERM...50 AVIATION...TDUD
Area Forecast Discussion
National Weather Service Pueblo CO
510 PM MST Fri Jan 12 2018 .UPDATE... Issued at 510 PM MST Fri Jan 12 2018 Updated to end winter weather advisory across the central mountains. && .SHORT TERM...(This evening through Saturday) Issued at 307 PM MST Fri Jan 12 2018 Currently... Front moving across the region at 2 pm this afternoon. Boundary was just south of the US50 corridor and was continuing southward. A line of showers was noted over the plains, mainly from near KLIC southeastward to just north of Holly CO. A few virga/very light rain showers were noted over a few other areas of the plains. Snow showers were noted over the mountains, especially the central mtns and the Pikes Peak region. Rest of today and into tonight... The main band of showers over the plains will continue to move southeast and should be out of the region by sunset. However HRRR shows some other light showers will be possible over most of the region until at least late evening. These showers are not expected to amount to much. Over the central mountains snow showers will last into early evening before dissipating. Gusty winds over the plains will decrease after sunset. Temps tonight will be on the cold side with mainly tens across the plains, with the coldest air over the far eastern plains and the warmest temps (aoa 20F) just east of the southern mtns. San Luis valley will be in the single digits along with most mtn locations. Tomorrow... Temps will be pretty seasonable tomorrow across the region with 40s across all of the plains, with generally partly to mostly sunny skies, with a few more clouds over the plains. It will be dry, with the exception of some snow showers over the northern sections of the central mtns. Winds will be light an diurnally driven over the plains with modest winds over the central mtns. .LONG TERM...(Saturday night through Friday) Issued at 307 PM MST Fri Jan 12 2018 Saturday night-Sunday...Models remain consistent with keeping moderate northwest flow aloft across the region, with another embedded wave translating across the Upper Midwest Saturday night. This wave looks to be too far east to bring any precipitation, though the moderate northwest flow develops lee troughing across the plains, allowing for the the shallow cool airmass across eastern Colorado to scour out from west to east Saturday night. The shallow cool airmass mixes out completely across the eastern plains on Sunday, with highs warming back into the 50s across the lower elevations, and mainly in the 30s and 40s across the higher terrain. Sunday night-Tuesday...Models are coming into better agreement of a stronger wave embedded within the northwest flow aloft translating across the Rockies Sunday night and Monday. Wave sends a strong backdoor cold front across eastern Colorado late Sunday night, which backs up across the eastern Mountains through late Monday morning. Models are indicating some light precipitation spreading from east to west across the eastern plains, with model soundings indicating the potential for light freezing drizzle across the plains early Monday morning, before colder air works into the area with any freezing precipitation quickly changing to light snow and flurries Monday mid morning and afternoon. Some light and fluffy snow accumulations will be possible along and west of the I-25 corridor through the day Monday. Highs in the 30s early Monday morning across the plains will cool through the rest of the morning and afternoon, as easterly upslope flow increases through the day. Further west, dry weather with at to slightly below normal temperatures is expected on Monday, though can`t rule out some light snow and flurries across the Central Mountains, with the northwest orographic flow. Northwest flow aloft moderates Monday night and Tuesday, with any snow/flurries across the mountains diminishing into Monday evening. With the cold airmass in place, overnight lows to be on the chilly side, in the single digits and teens areawide. Dry conditions and moderating temperatures expected for Tuesday. Wednesday-Friday...Some differences in the longer range models continue, though EC and GFS generally agree of another embedded wave digging across the Rockies on Wedensday, though continue to differ on strength of the system. At any rate, system looks to mainly affect the higher terrain along and west of the ContDvd, with blended pops introducing slight chances of snow in the Wednesday and Wednesday night timeframe, with temperatures at to slightly above seasonal levels. Warmer and drier conditions expected on Thursday with short wave ridging across the region, which gives way to increasing southwest flow aloft across the area on Friday, as another progressive system takes aim on the Rockies for Friday and into early next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 307 PM MST Fri Jan 12 2018 VFR conditions are anticipated during the next 24 hours at all 3 taf sites, KPUB, KALS and KCOS. The only exception may be some occnl low cigs this evening at KCOS and guidance products show some low clouds developing between ~03 and ~06 UTC. Gusty winds this afternoon will decrease after sunset. Winds will be light tonight with diurnally driven light winds tomorrow. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...MW SHORT TERM...HODANISH LONG TERM...MW AVIATION...HODANISH
Area Forecast Discussion
National Weather Service San Diego CA
738 PM PST Fri Jan 12 2018 .SYNOPSIS... Areas of dense fog will affect the immediate coast tonight, but is forecast to slowly improve from north to south overnight. High pressure aloft will bring warm and dry weather through the long weekend. Offshore flow will produce areas of gusty northeast winds in foothills and adjacent valleys. Fair weather will continue next week as flow turns back onshore. Late next week a trough of low pressure will bring strong onshore winds to the mountains and deserts Thursday night and Friday, and also our next chance of showers. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... ...Update... The warm up commenced in full force today with highs in the 60s in the mountains, high desert, and immediate coast and well into the 70s to near 80F degrees elsewhere. Lake Elsinore hit 81F degrees. It will warm even further this weekend, especially west of the mountains where 80s are forecast away from the coast. Fog continues to impact portions of the immediate coast, especially San Diego County. Most locales have visibility above 1 mile, but there are patches of 1/4 mile or less visibility. The trend overnight will be for gradual clearing of the fog from north to south as offshore flow spreads to the coast. However, latest HRRR model run shows that clearing may not occur until dawn for the southern San Diego coast. Clearing will occur much sooner across Orange County and northern San Diego County. Have expanded in time the fog/sky grids, following the aforementioned trend. Offshore winds have picked up as expected and are gusty through narrow areas that are typically prone to Santa Anas (through and below passes and along coastal slopes) with gusts in the 30-40 mph range. Models show little increase overnight and winds remaining localized. See previous discussion below for further forecast details. ...Previous Discussion (Issued at 132 PM PST Fri Jan 12 2018)... Areas of dense fog along the immediate coast have been persistent, as reported by much of OC and Camp Pendleton, but patchier in San Diego County. Fog will continue, dense in some areas, along the immediate coast probably through the evening. But an offshore trend in pressure gradients are forecast to push fog away from the coast overnight. High pressure aloft will peak this long weekend and will bring us more fair and warm weather, although with some high clouds to add texture to the sky. An offshore surface pressure gradient sets up this evening and northerly breezes will get started below the Cajon Pass. As the offshore flow evolves Saturday, those winds will push through all mountain passes and foothills into some valleys and continue all day. Top wind gusts should be late morning Saturday and could reach 40+ mph at the most favored locations. Top valley gusts could top 30 mph. These winds diminish somewhat late Saturday and a weaker version will continue through Sunday morning. Temperatures will get a boost from this offshore flow Saturday and Sunday, and will top out in the 80s for inland coastal areas and valleys. As the offshore flow relaxes on the holiday, temps will back off a few degrees in the coastal basin. A shortwave trough is forecast to move through northern California Tuesday, which will increase the onshore flow some and continue the cooling trend each day next week. By Thursday night, a Pacific trough of low pressure sags down the West Coast, promising strong onshore winds mainly for mountains, deserts, and coastal waters. There is also a chance of rain and mountain snow. Right now it doesn`t look super wet, and the best chance appears to be early Friday. && .AVIATION... 130230Z...COAST...SCT-BKN001-002 WITH VIS 1/4 TO 3 MILES ALONG THE IMMEDIATE COAST SPREADING LOCALLY INLAND AND IMPACTING KCRQ...KSAN AND KSNA THROUGH 08Z. AT 02Z...DENSE FOG WITH A VIS OF 1/4 MILE WAS REPORTED AT KCRQ, WHILE THE VIS WAS 3 MILES AT KSAN AND 4 MILES AT KSNA. LOW LEVEL EASTERLY WINDS LATER TONIGHT WILL SLOWLY PUSH THE LOW CLOUDS AND DENSE FOG OFF THE COAST BETWEEN 06Z-12Z SATURDAY. VALLEYS/MOUNTAINS/DESERTS...EAST TO NORTHEAST WIND GUSTS OF 25-35 KT WILL DEVELOP ALONG COASTAL MOUNTAIN SLOPES INTO ADJACENT FOOTHILLS TONIGHT THROUGH SAT MORNING WITH AREAS OF LLWS. SCT-BKN250 WITH UNRESTRICTED VIS THROUGH SAT MORNING. && .MARINE... A MARINE WEATHER STATEMENT HAS BEEN UPDATED FOR DENSE FOG WITH VISIBILITY 1 MILE OR LESS THROUGH LATE TONIGHT. DRY EASTERLY SURFACE FLOW WILL GRADUALLY PUSH THE DENSE FOG FARTHER WEST EARLY SATURDAY MORNING WITH IMPROVING VISIBILITIES. NO OTHER HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH SUNDAY. SEAS WILL INCREASE TO 7-11 FEET MONDAY AND TUESDAY IN THE OUTER WATERS FROM AN INCREASING LONG-PERIOD WNW SWELL. && .BEACHES... ELEVATED SURF AND STRONG RIP CURRENTS SATURDAY AND SUNDAY. EARLY NEXT WEEK A NEW LONG PERIOD WNW SWELL (285 DEGREES AT 18 SECONDS) WILL BRING HIGH SURF OF 6-9FT MONDAY THROUGH WEDNESDAY. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...Gregoria (Update)/MM (Prev Discussion) AVIATION/MARINE...Moede
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Saturday) Issued at 347 PM CST Fri Jan 12 2018 Northwest flow continues aloft over the central and western CONUS behind Thursday`s upper wave. Water vapor and IR imagery show a weak wave moving into the central Plains today with sporadic light radar returns and some trace to very light measured precipitation in snowfall from northwest Kansas into northeast Nebraska. A stronger and more persistent area was just west of the CWA at 20Z though ceiling heights remain above 6000 ft AGL and northeast winds under this layer behind the surface ridge along the Missouri River will continue dry air entrainment into this area into the early evening. NAM, GFS, and ECMWF are consistent with weak mid- level frontogenesis weakening this evening and the RAP and HRRR have been consistent in diminishing precip trends over the next several hours, and a small PoP for measurable amounts should suffice. Weak low-level cold air advection continues through tonight, with cloud cover with the weak wave slowly decreasing into midday Saturday. With cloud cover persisting, have lows a touch warmer than previous forecast, but single digits still expected with apparent temps a few to several degrees below zero. Weak warm-air advection develops Saturday afternoon, though the surface ridge remains to the northeast for another cold day. Mid cloud returns in the afternoon as a weak PV anomaly surges south out of western Canada. .LONG TERM...(Saturday night through Friday) Issued at 347 PM CST Fri Jan 12 2018 Models to differ with the speed and placement of the aforementioned wave, but decent precip chances develop overnight into Sunday morning as a narrow band of saturation moves through. Lapse rates do increase and could support a few hours of light to moderate snow with 1-2" snowfall potential as the column should remain well below freezing for any mixed precip. This wave exits by early Sunday evening, but attention will turn not far to the northwest as a stronger wave comes south-southeast out of the northern Plains with a potent cold front following. Another narrow-in-time precip window moves across the area late Sunday night into midday Monday as strong frontogenesis works through. There are some differences in specifics at this range too, and a stronger west wind around 850mb may be able to bring some mixed precip in at precip onset as well as afternoon temps reach into the 30s, but slightly higher precip/snowfall amounts seem in order for this wave. Monday will likely be another day of early day highs with temps falling into the single digits around sunset and north-northwest winds continuing and Advisory- level wind chills a good possibility from early Monday evening into midday Tuesday. Conditions looking much less concerning for Wednesday into Friday as the upper flow pattern shifts east and west to southwest flow developing. There could be a shortwave passage around Thursday though available moisture would likely be limited. South to southwest surface winds may push temps to above normal levels next Friday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 514 PM CST Fri Jan 12 2018 VFR conditions are expected through the taf period. The wind speeds will become light and variable tomorrow afternoon as a surface ridge slides across the area. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...65 LONG TERM...65 AVIATION...Sanders