Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/18/16

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
1001 PM CST Sat Dec 17 2016 .DISCUSSION...made a number of changes this evening to cover the expected surge of modified arctic air with the impressively tight temperature gradient...from which the front has dropped readings some 20 to 30 degrees in just two to three hours as it passed through; most recently austin/bergstrom which crashed from 66 to 45 between 7 and 9 pm. More importantly are the winds associated with the surge. In all areas of south central Texas, a 2 to 3 (or more) hour period of sustained 30 to 35 with gusts 40 to 45 mph come with the temperature crash and with gradient not slackening any as the front reaches Deep South Texas see no reason for the same result in all areas...only at slightly different times. So, have added segmented wind advisories to handle the best expected frontal time which is in line with the HRRR and about an hour faster than the latest NAM/GFS which puts the wind surge into the northern ranchlands (SR 285) around 2 AM, the Upper Valley/Rio Grande Plains by 3 AM, and Hidalgo/Starr between 3 and 4 AM. For timing, added a two hour buffer even though actual surge likely to last around 3 hours. For all of the ranchlands/upper Valley counties the advisories end between 7 and 9 AM. Filled in the rest of Cameron/Willacy into the prior wind advisory as guidance and analogs suggest that locations along/east of US 77/IH 69E will see similar longer duration winds/gusts as the just expanded that advisory and kept times as is (4 AM to 3 PM). Otherwise...made a few minor downward tweaks to temperatures/dewpoints late tonight/early Sunday. With speedier front expect even Brownsville to already be well down into the 50s by 6 AM and probably the upper 40s by 8 or 9 AM. A more north/northwest wind direction will follow and should crash temperatures all the way to the coast pretty soon after, and now have 40s there by 9 AM as well. Wind chill temperature drop a fraction as well but more importantly hit the 30s not too far after sunset even for the Valley. Advisory levels (25 ranch/30 valley) should hold off until after sunset so current timing of the worst of the cold looks on track. 52/BSG && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 49 53 40 46 / 30 40 30 30 BROWNSVILLE 48 51 39 45 / 30 40 20 30 HARLINGEN 45 47 37 45 / 30 30 20 20 MCALLEN 45 45 39 44 / 30 20 0 10 RIO GRANDE CITY 45 47 38 45 / 30 30 0 10 SOUTH PADRE ISLAND 52 57 45 49 / 40 50 40 40 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...Wind Advisory from 2 AM to 7 AM CST Sunday for TXZ248>250. Wind Chill Advisory from midnight Sunday night to 10 AM CST Monday for TXZ248>257. Wind Advisory from 4 AM to 3 PM CST Sunday for TXZ251-254>257. Wind Advisory from 3 AM to 9 AM CST Sunday for TXZ252-253. GM...Gale Warning from 3 AM to 6 PM CST Sunday 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 Dodge City KS
557 PM CST Sat Dec 17 2016 ...Updated for aviation discussion... .SHORT TERM...(Today and tonight) Issued at 222 AM CST Sat Dec 17 2016 Mesoscale models and even global models still show the potential for winter weather across southwest Kansas today. The Arctic airmass continues to sink southward early this morning with temperatures dropping each hour. Thus, a non diurnal temperature curve is expected with the highest temperatures already observed. For pop arrangement, relied more on the more reliable ARW. This model shows a mesoscale band moving through from Colorado and eventually into Kansas. QPF from the model is on the light side, however, snow ratios will be high (20 to 1) given the very cold airmass in place. Snow should be over and east of the forecast district by tonight. For amounts, forecast amounts are in the 1-2" range. The HRRR does show higher amounts, but this model can be overly aggressive at times. The 1-2" amounts also match the ECMWF, which tends to be more correct, than say the GFS. For the advisory, will continue as is. The winter weather advisory mentions snow amounts, blowing snow, and the low wind chills for today and tomorrow. Other than the already mentioned plummeting temperatures through the day, the next item to mention is lows for tonight. Since start out cold in the first place, think a cooler solution is the way to go. Have values ranged from -2 to -8 across the forecast district. .LONG TERM...(Sunday through Friday) Issued at 222 AM CST Sat Dec 17 2016 The extended period is largely dry with moderating temperatures. The synoptic wave causing short term weather will move east of the area. Upper level flow will continue westerly to northwesterly through next week. Low level downslope flow will strengthen and allow temperatures to moderate and be not so cold. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 555 PM CST Sat Dec 17 2016 An upper level disturbance will move away from western Kansas this evening as surface high pressure builds in. Winds will become light this evening from the northwest and gradually change to the southwest by morning. && .PRELIMINARY POINT TEMPS/POPS... DDC -9 20 3 32 / 10 0 0 0 GCK -11 21 1 34 / 0 0 0 0 EHA -6 22 5 38 / 10 0 0 0 LBL -8 21 2 36 / 10 0 0 0 HYS -9 20 4 33 / 10 0 0 0 P28 -4 18 2 32 / 20 0 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 PM CST /5 PM MST/ this evening for KSZ030-043>045-061>063. Wind Chill Warning until 10 AM CST /9 AM MST/ Sunday for KSZ030- 043>045-061>063. Winter Weather Advisory until 10 AM CST Sunday for KSZ031-046- 064>066-074>081-084>090. && $$ SHORT TERM...Sugden LONG TERM...Sugden AVIATION...Finch
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
610 PM EST Sat Dec 17 2016 .AVIATION... Weak shortwave will ripple northeast along the next re-enforcing shot of colder air this evening. This will bring a period of -sn kptk north with a mix of -fzdz/pl possible for the I-94 terminals in the 00z-03z period before a change to -shsn. The transition from any -fzdz to pl to sn will be relatively quick as wedge of low level cold air deepens steadily early this evening. Will bring mvfr/ifr conditions with this activity and maintain mvfr cigs into Sunday as lake effect stratus eventually replaces cloud shield associated with synoptic forcing. For DTW...Still a chance of -fzdz for an hour or two to start the forecast period, but expect a steady transition to -pl and then -sn. Generally expect mvfr conditions with periods of ifr during periods of precipitation. //DTW Threshold Probabilities... * High for cigs aob 5kft through into Sunday. * Medium confidence in precip type starting as light freezing drizzle 00z-01z and transition to -pl and -sn in the 01z-03z time frame. && .PREV DISCUSSION... Issued at 246 PM EST Sat Dec 17 2016 DISCUSSION... Widespread virga prevalent at press time with sporadic obs of freezing drizzle mixed in. Temperatures remain firmly in the 20z making any non-freezing liquid precip difficult to come by this evening except perhaps the furthest south and east portions of the area. Packet of shortwave energy noted on WV imagery over IL and IN this afternoon with some associated more robust returns immediately in advance. Given current temperature obs, this will set the stage for one more round of either light freezing rain or snow pellets south and east of the glacial ridge. HRRR output suggests light freezing rain, as opposed to freezing drizzle, given sufficient saturation this go around. However, inspection of the sounding suggests that while weak WAA will produce a warm nose aloft, melting will likely be minimal given peak temp of only 1.7C at at elevation over 3000 feet. Thus, the expectation until passage of the mid-level shortwave around 22z will be for an expansion of flurries or light snow showers across the NW CWA and snow pellets or pockets of light fzra to the south and east of the ridge line. Focus then shifts to tonight. Another packet of energy emerging from the southern plains will rapidly propagate northeast along the east flank of the upper trough approaching the northern Great Lakes. Mid- level forcing will be better organized as the jet overhead strengthens to 180kts and tilts the resident elevated front producing a band of fgen augmented by larger scale height falls. However, dry northwest flow will increasingly infiltrate beneath the frontal zone as it tilts, increasing confidence in a high pop/low qpf scenario for tonight. Ptype expected to be all snow with 1 to 1.5" possible in the Saginaw Valley and/or Thumb. Half inch or less elsewhere. Forecast focus for Sunday and Monday will be temps and wind chill as thermal trough settles overhead. Highs Sunday may touch 20 in some spots as flow backs to westerly and Lake Michigan modification is maximized. Continued backing flow as 1047mb anticyclone settles south of the state will eliminate modification processes Sunday night, but gradient will likely still be such that decoupling will be difficult to come by. As such, remained conservative with temperatures generally just slightly below zero and maintained a gradient wind supportive of wind chills approaching wind chill advisory criteria through the night and into early Monday morning. Still potential for further lowering of temps depending on clouds, etc...particularly across the southwest CWA where cold air will leak around the lakes. Very cold surface temps and continued residence in the back end of the thermal trough will make it difficult to rebound south of the I-94 corridor where highs will struggle to 10. Further north, most places should touch 15 degrees or so. Wind chill below zero through Monday and Monday night. Low pressure passing to the north of the Great Lakes region on Tuesday will allow a southerly flow to promote a warming trend for Lower Michigan into the middle of the week. Next chance for precipitation across Michigan comes in the Wednesday/Thursday timeframe as low pressure develops ahead of a shortwave trough dropping south from Alberta. High pressure then builds into the region to end the week with temperatures near seasonal values. MARINE... a weak area of low pressure will lift northward through the Ohio River Valley this evening. Arctic air surging into central Great Lakes tonight will result in a round of northwest gales over much of the Lake Huron basin tonight. Winds will decrease Sunday afternoon, but still may top around 30 knots Sunday Night into Monday as strong high pressure tracks through the northern Ohio valley, leading to winds shifting to the west and then southwest. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Gale Warning from 10 PM this evening to 10 AM EST Sunday FOR LHZ362- 363-441-442-462>464. Small Craft Advisory from 10 PM this evening to 3 PM EST Sunday FOR LHZ421-443. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....DG DISCUSSION...JVC/JD MARINE.......CB You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion...corrected
National Weather Service Quad Cities IA IL
545 PM CST Sat Dec 17 2016 ...00z AVIATION UPDATE... .SYNOPSIS... Issued at 148 PM CST Sat Dec 17 2016 An arctic cold front surged into eastern Iowa during the early afternoon hours, accompanied by an area of light to moderate snow. A northwest wind was gusting around 25 mph, creating blowing and drifting snow over parts of eastern Iowa, and dropping visibilities around a half mile at times. Early afternoon temperatures were in the teens over eastern Iowa, and in the upper teens to low 20s in western Illinois. Some freezing drizzle was also creating slick roads over far northeast Missouri into west central Illinois. && .SHORT TERM...(This Evening through Sunday) ISSUED AT 148 PM CST Sat Dec 17 2016 The short term period remains focused on the ongoing winter weather and bitterly cold temperatures, and headline considerations tonight through Sunday. Comparing various models with radar trends, the 12km WRF and nested WRF along with the RAP have a good handle on the current weather. Am expecting moderate snow bands to continue feeding into the area and gradually spreading east across the forecast area through the evening. Model blend QPF and snow ratios of 15-20:1 by tonight should yield a broad area of 2 to 3 inches of snow. Would not be surprised to see an isolated 4 inch amount given the deep saturation in the dendritic layer, although these will be difficult conditions to get an accurate snow measurement and we will also see some crystal fragmentation with the strong winds. Visibilities below a half mile in snow and blowing snow, and drifting, will create very hazardous travel conditions this afternoon and tonight. Not planning any changes to the headlines at this time with a winter weather advisory for the entire area through midnight. Conditions in open areas will be worse than what it appears in town, and travel will be very tricky through tonight with blowing snow lingering even after the snow intensity diminishes. Have expanded the wind chill warning one more tier of counties to the south, with lowest wind chills of 30 to 38 below expected early Sunday morning. The rest of the area is under a wind chill advisory for lowest wind chills of 20 to near 30 below. Additional modifications to the headlines will be likely with later shifts, as advisory criteria wind chills are expected to persist through Sunday afternoon across the north. High temperatures Sunday will range from about 4 above zero in the far south, to 7 below in the far north. .LONG TERM...(Sunday Night through Saturday) ISSUED AT 148 PM CST Sat Dec 17 2016 Bitter cold temperatures will continue one more night followed by moderating temperatures. Arctic high pressure will be over the area at sunset Sunday and then move into the Great Lakes after midnight. Temperatures should plummet during the evening with lows occurring 8 PM to midnight before rising after midnight. The combination of temperatures and the light wind suggest headlines for wind chill may be needed Sunday night into Monday morning. Quiet and dry conditions will be seen Monday through Tuesday as temperatures moderate and approach normal. Tuesday night on... The quiet and dry conditions will continue Tuesday night as a storm system moves through the northern Plains. Temperatures should be close to normal. Wednesday through Thursday morning a weak clipper type system will move through the Midwest. The model consensus has slight chance to chance pops over the northern two thirds of the area for mainly light snow. The possibility does exist that the storm system may track further north than what the models currently indicate. If that occurs, then much of the area would end up being dry. The exception may be the highway 20 corridor where there would still be a threat of light snow. Thursday afternoon through Friday night the model consensus has dry conditions as yet another high moves through the Midwest. Temperatures should be around or slightly warmer than normal. Attention then turns to the holiday weekend. The overall flow pattern across the northern hemisphere is favorable for the development of a storm system next weekend, and, the global models are developing such a storm system across the continent. HOWEVER, there are differences between the GFS/DGEX/ECMWF/CMC global on how this storm develops and tracks. The energy for this potential storm system is currently over Siberia. How this energy moves across the Pacific next week and interacts with additional energy dropping out of the arctic will be factors in how this storm system eventually develops across North America. The GFS brings a light snow event with the leading disturbance and has the main storm system tracking just to the south and east of the area. The DGEX has a light snow event with the leading disturbance and has the main storm system passing well to the south and east of the area. The ECMWF has a light snow event with the first disturbance and then sideswipes the area with the main storm system. The CMC global has a light to possibly moderate snow event with the main system passing well to the south and east of the area. As a result of these differences, the model consensus currently has slight chance to chance pops Saturday and Saturday night. CAUTIONARY should/can expect each model run to change, possibly significantly, for much of next week regarding the development of this potential storm system. && .AVIATION...(For the 00Z TAFS through 00Z Sunday Evening) ISSUED AT 536 PM CST Sat Dec 17 2016 Worst of the conditions expected at MLI and BRL through mid evening where band of moderate snow and gusty NW winds will result in IFR to LIFR conditions. Meanwhile, light snow and blowing snow will result in mainly MVFR conditions at CID and DBQ although pockets of IFR conditions possible through mid evening. Late this evening and overnight expect improvement to VFR conditions, however some pockets of blowing snow and brief reduction in visibility will remain possible through the early morning before winds slowly subside. Anticipate VFR conditions Sunday with NW winds 10-15 kts diminishing below 10 kts and shifting to W/SW during the afternoon, as high pressure passes to our south. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...Winter Weather Advisory until midnight CST tonight for Benton- Buchanan-Cedar-Clinton-Delaware-Des Moines-Dubuque-Henry IA- Iowa-Jackson-Jefferson-Johnson-Jones-Keokuk-Lee-Linn-Louisa- Muscatine-Scott-Van Buren-Washington. Wind Chill Warning from 9 PM this evening to noon CST Sunday for Benton-Buchanan-Cedar-Clinton-Delaware-Dubuque-Iowa-Jackson- Johnson-Jones-Linn-Scott. Wind Chill Advisory from 9 PM this evening to noon CST Sunday for Des Moines-Henry IA-Jefferson-Keokuk-Lee-Louisa- Muscatine-Van Buren-Washington. IL...Winter Weather Advisory until midnight CST tonight for Bureau- Carroll-Hancock-Henderson-Henry IL-Jo Daviess-McDonough- Mercer-Putnam-Rock Island-Stephenson-Warren-Whiteside. Wind Chill Advisory from 9 PM this evening to noon CST Sunday for Bureau-Carroll-Hancock-Henderson-Henry IL-Jo Daviess- McDonough-Mercer-Putnam-Rock Island-Stephenson-Warren- Whiteside. MO...Winter Weather Advisory until midnight CST tonight for Clark- Scotland. Wind Chill Advisory from 9 PM this evening to noon CST Sunday for Clark-Scotland. && $$ SYNOPSIS...RP Kinney SHORT TERM...RP Kinney LONG TERM...08 AVIATION...05
Area Forecast Discussion
National Weather Service El Paso TX/Santa Teresa NM
341 PM MST Sat Dec 17 2016 .SYNOPSIS... Strong winter storm is currently barreling through the Borderland with some very strong wind gusts and cooler air. The winds will diminish tonight but cold air from the east will filter in for Sunday and Monday as east winds at the surface develop. Highs both days will run around 10 degrees below normal. The rest of the new week ahead looks to remain dry, with temperatures above normal again Tuesday and Wednesday. Another cold front moves in from the east again for cooler temperatures Thursday and Friday. && .DISCUSSION... Quite a powerful winter storm rolling through today, with the secondary punch of a back door cold front also moving into the area. Interestingly, perhaps the location of the cold dome of air (high pressure) and the orientation of the upper trough, may have tended to induce lee side low development further south over western Texas. This may have led to stronger pressure gradients and thus stronger winds. Pacific cold front moved through this morning and should be assimilating in with the arctic back door cold front. Precipitation should about be over as upper trough now east of the area. Back door cold front through Roswell and Artesia and almost butting up against the Sacramento/Guadalupe Mountains. HRRR shows cold air remains dammed against these mountains through daybreak Sunday, and mid range progs show this remaining true to some degree remainder of Sunday. However some of the cool air will surge west throughout the day, giving the area a chilly day. Remainder of week looks to stay dry. Models do show upper level moisture associated with jet streak developing over the area Sunday night and Monday. For now increased clouds in grid fields but did not put POPS in. Models indicate some baroclinic leaf potential, but for now looks like best lift associated with RRQ of jet remains over northern Mexico. Both GFS/ECMWF in close agreement on handling next Pacific low- keeping well west of the Baja and of not much consequence to us. After a couple of days of warming temperatures, quick moving short wave across the southern Rockies will allow another back door cold front in Wednesday night, for a cooler Thursday and Friday. Significant differences remain between the two models for Christmas Eve/Christmas Day. Far out yet for much confidence, but let`s just say the GFS is hinting at a white Christmas, while the ECMWF shows a mild, seasonable day. && .AVIATION...Valid 18/00Z-19/00Z... Strong Pacific system accompanied by a cold front pushed through the area today thru the area by 21Z. Winds will be W/SW between 30-40G50KTS thru 00Z then NW 20-30G35KTS. Gusts could be stronger near area mountains. Winds becoming Ne 10kts after 09Z. Sky becoming skc- few 040. Mdt to GTR turbc ovr and nr mtns esply E slopes until 03Z. && .FIRE WEATHER... Today a strong Pacific system accompanied by a cold front pushed through the area brining light snow to the Sacramentos mountains, the Gila Region and Silver City. Spotty light rain showers were noted across some of the fire zones. Winds will continue to affect the entire region especially the east-slope areas. As a result blow dust could be an issue in the lower portions of the region. Temperatures will drop by 10 to 15 degrees with the frontal passage and will drop another 5-10 degrees Sunday as cold Arctic air pushes into the area from the east. Temperatures will start to warm up to normal by Tuesday. Friday of next week another Pacific system could bring mountain precipitation. && .PRELIMINARY POINT TEMPS/POPS... El Paso 27 47 28 48 / 0 0 0 0 Sierra Blanca 25 41 23 43 / 0 0 0 0 Las Cruces 23 47 25 48 / 0 0 0 0 Alamogordo 19 45 22 47 / 0 0 0 0 Cloudcroft 12 30 15 33 / 0 0 0 0 Truth or Consequences 22 47 21 47 / 0 0 0 0 Silver City 18 44 22 46 / 0 0 0 0 Deming 18 49 24 50 / 0 0 0 0 Lordsburg 16 50 25 51 / 0 0 0 0 West El Paso Metro 28 47 29 48 / 0 0 0 0 Dell City 16 42 20 45 / 0 0 0 0 Fort Hancock 25 49 26 50 / 0 0 0 0 Loma Linda 20 39 22 42 / 0 0 0 0 Fabens 23 48 24 48 / 0 0 0 0 Santa Teresa 25 47 26 47 / 0 0 0 0 White Sands HQ 25 45 26 47 / 0 0 0 0 Jornada Range 19 47 18 49 / 0 0 0 0 Hatch 20 47 23 49 / 0 0 0 0 Columbus 26 49 27 49 / 0 0 0 0 Orogrande 21 45 24 47 / 0 0 0 0 Mayhill 13 36 14 40 / 0 0 0 0 Mescalero 14 38 16 40 / 0 0 0 0 Timberon 16 35 17 38 / 0 0 0 0 Winston 14 41 13 43 / 0 0 0 0 Hillsboro 20 46 19 48 / 0 0 0 0 Spaceport 22 46 19 47 / 0 0 0 0 Lake Roberts 11 45 14 46 / 0 0 0 0 Hurley 16 44 20 46 / 0 0 0 0 Cliff 18 51 16 49 / 0 0 0 0 Mule Creek 18 48 14 49 / 0 0 0 0 Faywood 20 47 21 48 / 0 0 0 0 Animas 18 53 24 51 / 0 0 0 0 Hachita 17 50 23 49 / 0 0 0 0 Antelope Wells 20 51 23 50 / 0 0 0 0 Cloverdale 23 49 26 47 / 0 0 0 0 && .EPZ WATCHES/WARNINGS/ADVISORIES... NM...High Wind Warning until 6 PM MST this evening for NMZ413>416. Wind Advisory until 6 PM MST this evening for NMZ407-409>412-417. TX...High Wind Warning until 6 PM MST this evening for TXZ419. Wind Advisory until 6 PM MST this evening for TXZ418-420>424. && $$ 99/99/17
Area Forecast Discussion
National Weather Service Lincoln IL
909 PM CST Sat Dec 17 2016 .UPDATE... Issued at 900 PM CST Sat Dec 17 2016 Arctic air continues to spill across central and southeast Illinois this evening on the back side of the system that has impacted the area since yesterday. The vertical column has cooled sufficiently, except across far southeast Illinois, that any precipitation at this point will fall in the form of snow. A band of steadier snow is approaching the Illinois River, but it should not be a significant snow producer. Most locations should see well less than an inch of snow by morning. Going headlines look reasonable and will not be changed at this time. Only minor hourly tweaks were necessary to the overnight forecast. && .SHORT TERM...(This evening through Sunday) ISSUED AT 319 PM CST Sat Dec 17 2016 20z/2pm surface analysis shows frontal boundary well to the south near the Ohio River, while cold N/NW winds prevail across central Illinois. Persistent freezing drizzle that has been ongoing since late yesterday afternoon has finally come to an end across much of the KILX CWA as evidenced by improving visibilities over the past couple of hours. Radar is showing rain showers beginning to develop north of the front, particularly across the SE. Think this trend will continue into the evening, with rain becoming likely along/south of I-70. As temperatures fall below freezing, a light accumulation of ice of less than one-tenth of an inch is likely across this area. Further northwest, a band of deformation zone snow currently across eastern Iowa into northern Missouri will work its way eastward this evening. Based on latest HRRR forecast, it appears snow will begin across the Illinois River Valley between 5pm and 7pm...then further east to the I-55 corridor by mid-evening. The snow band will shift into east-central Illinois toward midnight, but it will likely be diminishing in intensity by then. Total snow accumulations tonight will generally be 1 inch or less...but may reach as much as 2 inches along/northwest of a Macomb to Lacon line. In addition to the snow, gusty northwesterly winds will be transporting bitterly cold air into the region. Low temperatures will range from the single digits below zero along/northwest of the Illinois River to the teens south of I-70. These air temperatures combined with winds gusting to between 20 and 30 mph will create dangerously low wind-chills of 15 below to 25 below zero along/west of a Champaign to Shelbyville line where a Wind Chill Advisory will remain in effect through midday Sunday. Skies will clear early Sunday morning: however, despite a good deal of sunshine, temperatures will not rebound much from morning lows. Afternoon highs will range from around zero along/northwest of the Illinois River to the teens south of I-70. .LONG TERM...(Sunday night through Saturday) ISSUED AT 319 PM CST Sat Dec 17 2016 Arctic high pressure will be centered across central Illinois Sunday night bringing another bitterly cold night with lows several degrees below guidance, especially across our northern counties where an inch or two of fresh snow will be present. If areas further south receives a bit more snow than expected tonight, we may have to lower the early morning lows in those areas as well. With the ridge axis situated right across the forecast area, winds will be light so the wind chills shouldn`t be an issue, at least compared to what we will have over our area Sunday. Temperatures during the day Monday will struggle into the teens to lower 20s as a southerly flow develops with the Arctic high shifting off to our east. The warming trend gets going in earnest Tuesday as the mercury tops out from 30 to 35 degrees as a weak shortwave tracks well to our north during the day and our area under the influence of a southwesterly flow. Another more vigorous shortwave is seen on the models for later Wednesday into Wednesday night but again, moisture quite limited ahead of this disturbance, so POPs will be quite low Wednesday evening, with the better forcing and moisture to our north. Not a lot of cold air behind the wave for Thursday with temperatures cooling a few degrees before we see warmer air return for Friday as upper level ridging builds over the central U.S. in response to a significant trof forecast by the 12z ECMWF and GFS to dig sharply into the southwest U.S. Friday night into Saturday with the potential for rain or snow over our area next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 551 PM CST Sat Dec 17 2016 Pesky storm system will finally pull away from the central Illinois terminals during the 00Z TAF valid time. Gusty northwest winds on the back side of the system will help push much drier/colder air into the area. These winds have improved conditions to MVFR and they should stay there for the most part through the overnight hours. A period or two of light snow is likely tonight before skies clear Sunday morning. Once skies clear, VFR conditions will persist for the duration of the period. && .ILX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 AM CST Sunday for ILZ027>031- 036>038-040>057-061>063-066>068-071>073. Wind Chill Advisory until noon CST Sunday for ILZ027>031-036>038- 040>045-047>054-061. && $$ UPDATE...Bak SHORT TERM...Barnes LONG TERM...Smith AVIATION...Bak
Area Forecast Discussion
National Weather Service Miami FL
802 PM EST Sat Dec 17 2016 .UPDATE... This evenings 18/0000Z sounding showed moistening up to 700 mb, with a capping temperature inversion and dry air aloft. PWATs have climbed up to roughly 1.3 inches, higher than the last couple of nights. Also of note, CAPE has risen to above 1,000 J/KG, indicating weak to moderate instability. Through the night, the HRRR and Hi-Res WRF prog light to occasionally moderate showers from the southeast to northwest. This activity would most likely affect the Atlantic waters and east coast metro through early morning. Have increased PoPs along northeast portions of the CWA, in line with current radar trends, and lowered PoPs over the interior. As the night progresses and the boundary layer decouples, the SREF increases the chance of patchy fog across the western interior and current grids reflect this. Otherwise, the rest of the forecast looks on track. && .PREV DISCUSSION... /issued 655 PM EST Sat Dec 17 2016/ AVIATION... High pressure to the northeast, and a fairly tight pressure gradient over the region, will keep the wind out of the southeast through the TAF period. While it will subside somewhat overnight, it will pick up again at around 15kts in the morning. Also, there may be some isolated showers along the Atlantic coastal areas, which may very briefly affect some of the terminals through the night, and possibly into tomorrow. However, the chances and impacts are too low to include in the TAFs at this time. PREV DISCUSSION... /issued 431 PM EST Sat Dec 17 2016/ DISCUSSION... Latest visible imagery this afternoon showed scattered strato-cu streaming from southeast to northwest across southern Florida. This 17/1200Z MFL sounding from earlier today indicated a modest moist layer extending up through 850 mb with a capping inversion and drier aloft. With low level moisture in place, along with weak convergence, the HRRR and Hi-Res models prog spotty showers to continue over the peninsula through evening. However, any accumulation from this activity will be sparse. Temperatures will eventually wane past sundown but are maxing out in the low 80s along the immediate east coast to mid 80s inland. A high temperature of 85 degrees in Miami tied the old daily record set back in 1965. Tonight, a tight surface high pressure gradient over the region will maintain the breezy southeast winds. The strongest winds should exist along the immediate coastline, where friction from terrain is the least. Further inland, over the interior and Gulf Coast, patchy fog may develop as the temperatures decline towards the dewpoint and the boundary layers decouples. Similar conditions are on tap for tomorrow as upper level high pressure dominates the weather pattern. Expect breezy southeast winds, 10-15 mph, along with passing clouds and a sight chance of light showers. Large scale subsidence associated with the aforementioned high will allow for temperatures to once again reach near record values. Low to mid 80s are forecast along the east coast metro, with mid 80s inland. These values are running anywhere from 5 to 10 degrees above average for mid December. Monday trough mid week, high pressure aloft will begin to weaken. Both maximum and minimum temperatures will decrease by a few degrees each day. Easterly flow will continue to advect moisture in the lower levels of the atmosphere. Thus, the best chance for light shower activity will be along eastern portions of the peninsula. Towards late week, both the the GFS and ECWMF stall a weakening cold front over central Florida. However, this far out, confidence of the eventual placement of this feature is low. MARINE... Surface high pressure, centered over the western Atlantic, will lead to a tightening pressure gradient across the local waters tonight. Southeasterly winds in the Atlantic waters will be around 15-20 kts and 10-15 kts across the Gulf. Seas 1-2ft over the Gulf, occasionally up to 3ft well offshore, and 3-5ft over the Atlantic. May see some periods of steady 20 kt winds with seas up to 5 feet across the Atlantic waters overnight, but for now, prevailing winds look to remain below advisory criteria. Small craft should exercise caution in the Atlantic. Pressure gradient relaxes into next week as high pressure over the region weakens. BEACH FORECAST... Gusty southeasterly winds will continue the risk of rip currents along all Atlantic beaches through tonight. Though winds subside into Sunday, a moderate risk may linger into early next week. && .PRELIMINARY POINT TEMPS/POPS... West Palm Beach 76 85 74 84 / 30 20 20 20 Fort Lauderdale 77 84 75 83 / 20 20 10 10 Miami 76 85 75 84 / 20 20 10 10 Naples 70 86 70 85 / 10 20 10 10 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk until 4 AM EST Sunday for FLZ168-172-173. AM...None. GM...None. && UPDATE...27/JT DISCUSSION...27/JT MARINE...27/JT AVIATION...13 BEACH FORECAST...27/JT
Area Forecast Discussion...UPDATED
National Weather Service Norman OK
908 PM CST Sat Dec 17 2016 .UPDATE... Precipitation and clouds are quickly clearing out of the area. There still may be a few snow flurries around for the next hour or two but the impactful precip has ended so have cancelled the rest of the winter weather advisory. Focus now shifts to the cold temperatures and dangerous wind chills across the area tonight into Sunday morning. Temperatures continue to fall with many locations already around or below 10 degrees across the fa. With the skies clearing faster than forecast and winds beginning to decrease have lowered temperatures at least a couple of degrees everywhere. This has lead to forecasted minimum wind chill values below zero across the entire fa with wind chills around -18 in NW OK. With this in mind will add a few more counties to the wind chill advisory which will put the entire fa except for 3 counties in the advisory. With the wind speeds beginning to decrease across the area, will also cancel the wind advisory for SW OK and W N TX. An isolated gust or two over 40 mph may still occur over the next hour but overall wind gusts will remain below 40 mph. && .PREV DISCUSSION... /issued 546 PM CST Sat Dec 17 2016/ AVIATION... 18/00Z TAFs. Primarily MVFR conditions will continue through 03-05Z time frame across most terminals before becoming VFR thereafter. Brief heavier snow bands will primarily affect KOKC/KOUN/KPNC next couple of hours. Winds will decrease overnight and become light north and northeast after 12Z. PREV DISCUSSION... /issued 146 PM CST Sat Dec 17 2016/ DISCUSSION... The winter weather advisory continues in effect, but changes were made to terminate it at midnight Sunday. Models are quite consistent in taking the upper forcing to the northeast of Oklahoma before that time. Additionally, a wind chill advisory was added for much of Okalhoma from the evening until Sunday morning. Temperatures will continue their fall until sunrise Sunday. Along with the strong north winds, wind chill values will probably reach a minimum of -15 degrees in western Oklahoma before the wind subsides a bit. Values close to -10 degrees are probable in central Oklahoma by sunrise Sunday. Concerning snowfall, the forecast remains quite consistent with amounts mostly under 2 inches in northern Oklahoma and under 1 inch in central Oklahoma. However, since late morning, short-term models have indicated that some banding could occur from southwest into central Oklahoma early this evening. This is separate from the larger synoptic system that will cross central and eastern Kansas and bring snow to northern Oklahoma. IR satellite imagery indicates a zone of cooling cloud tops and the HRRR develops a narrow band of light snow from southwest Oklahoma to central Oklahoma by 5 PM. By 9 PM it is expected to be mostly finished. Still, amounts in this area generally expected to be under 1 inch. The upper system will quickly move northeast of Oklahoma after midnight and the snow is expected to finish by then. Sunday will remain quite cold with the center of the airmass over northern Oklahoma much of the day. Strong warming begins Monday when daytime temperatures are expected to be 10 to 15 degrees above those of Sunday, and Tuesday will see readings 10 to 15 degrees above those of Monday. Temperatures through next week will bounce around climatological normals. There is a front expected Wednesday, but the airmass will cross from the central Rockies, so the downslope component will cause little cooling with its passage here. It is expected to be dry. The ECMWF and GFS differ on the magnitude of an upper trough next weekend. For now, a slight chance for rain or snow is forecast for northern Oklahoma next Saturday. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 4 21 7 34 / 90 0 0 0 Hobart OK 4 20 8 33 / 60 0 0 0 Wichita Falls TX 9 26 10 34 / 30 0 0 0 Gage OK -5 24 5 37 / 10 0 0 0 Ponca City OK 0 18 3 31 / 90 0 0 0 Durant OK 15 30 14 36 / 30 0 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...Wind Chill Advisory until 10 AM CST Sunday for OKZ004>048. TX...Wind Chill Advisory until 10 AM CST Sunday for TXZ083>090. && $$ 25/11
Area Forecast Discussion
National Weather Service Shreveport LA
924 PM CST Sat Dec 17 2016 .UPDATE... To add Tornado Watch 518 to our NE tier of counties/parishes. && .DISCUSSION... The watch goes until 3 am, but unless we have to add some parishes in the next hour or two, we may be done before midnight severe threat wise. The Arctic cold front is generally along and behind the strongest reflectivity from Deep E TX in N central LA and S central AR. Temperatures have been a challenge to keep up with, but HRRR and new NAM have been helpful and we have tweaked lows a bit by daybreak. Also added a sooner start to this evening with a change over possible as I-30 corridor in NE TX and up into SE OK with the current freezing line for a guide. We will likely update again by midnight. /24/ && .PREV DISCUSSION... /issued 530 PM CST Sat Dec 17 2016/ AVIATION... Much talked about cold front as of 00z was located near a TYR...TXK...ADF line and is increasing its southwestward momentum into our terminal airspace this evening. Followed closely the timing of the latest HRRR timing the wind shift and possibilities of convection overnight with the associated boundary. SSW winds ahead of the cold front continue to be sustained near 15kts with gusts as high as 25kts across some terminal locations. Pre cold frontal ceilings are mostly VFR with heights ranging from 4-6kft but directly behind the front...ceilings are near 1kft. Post frontal winds are from the northwest sustained near 15-20kt with gusts as high as 30kts and we have inserted those kind of conditions as well overnight behind the front. Concerning convection...terminals most likely to see -TSRA would include the ELD/SHV and MLU terminals...otherwise...only SHRAs are possible along and a two to three hours in the wake of the initial wind shift line. Should lose lower ceilings towards sunrise most areas and slightly thereafter across our eastern terminal locations with strong N winds continuing under a veil of high cirrus through much of the day on Sunday. 13 PREV DISCUSSION... /issued 421 PM CST Sat Dec 17 2016/ DISCUSSION... Arctic cold front continues to bear down on the region with I-30 in sight as of 22Z this afternoon. The temperature gradient is quite stark on either side of the boundary with freezing temps just northwest of the DFW metroplex while readings ahead of the front are in the mid 70s to near 80 degrees over much of our CWA. Convection has been slow to develop as we have been mired in cloud cover all day with a strong inversion in place. With that in mind, expect thunderstorms to begin developing closer to frontal passage with a line of convection likely forming this evening across south Arkansas down into north Louisiana and possibly deep east Texas where better instability is expected to be present. This is the area of concern for the possibility of severe thunderstorms as we move into this evening. The primary threat still appears to be damaging wind gusts especially if we see a linear complex develop, but hail and isolated tornadoes will remain in play over the area of slight risk outlined above. The front will accelerate overnight and quickly exit the region on Sunday morning with very cold air mass spilling southward across the region. Additionally, very gusty north to northwest winds will create dangerous wind chill readings in the teens and 20s on Sunday while actual temperatures will likely not make it out of the 30s for most of region. A lake wind advisory remains in effect through early Sunday evening with wind gusts of 35 mph or higher possible through the afternoon. The coldest temperatures will occur overnight Sunday into Monday morning and again on Tuesday morning with teens and 20s for lows. This will likely prompt hard freeze warnings for at least part of the region, most likely along and north of the I-30 corridor. Then a more zonal pattern will set up for mid week with a modest warm- up for Wednesday. This will coincide with an upper disturbance in the Gulf of Mexico shifting northeast and may allow for some rain showers to affect our far southeast zones Wednesday night through early Thursday. However, this disturbance will be quickly picked up by our next cold front due to arrive on Thursday and ushered on to the southeast with the cooler and drier air mass holding serve through the remainder of the extended period. /19/ && .PRELIMINARY POINT TEMPS/POPS... SHV 28 38 24 41 / 70 10 0 0 MLU 31 39 23 40 / 90 10 0 0 DEQ 23 34 16 41 / 30 0 0 0 TXK 25 36 20 40 / 40 10 0 0 ELD 26 36 20 39 / 80 10 0 0 TYR 24 34 23 40 / 40 0 0 0 GGG 28 38 23 41 / 40 10 0 0 LFK 34 41 26 45 / 70 10 0 0 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...Lake Wind Advisory until 7 PM CST Sunday for ARZ050-051-059>061- 070>073. LA...Lake Wind Advisory until 7 PM CST Sunday for LAZ001>006-010>014- 017>022. OK...Lake Wind Advisory until 7 PM CST Sunday for OKZ077. TX...Lake Wind Advisory until 7 PM CST Sunday for TXZ096-097-108>112- 124>126-136>138-149>153-165>167. && $$ 24/13/19
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Sunday) Issued at 201 PM CST Sat Dec 17 2016 19Z surface obs show the the arctic high continuing to build south with the center of the ridge over the western Dakotas. Aloft, 19Z water vapor indicates a broad longwave trough over the U.S. with a shortwave lifting out of the Rockies and across western KS. Regional radars depict a band of snow from south central KS through northeast KS. For the late afternoon and evening, the forecast appears to be unfolding as expected. Latest NAM and RAP solutions continue to show the strongest frontogenesis moving though around 21Z. This is when the strongest vertical motion is expected to occur along with the moderate to heavy snowfall. There also remains signs of weakly unstable air or possibly upright instability just above the frontogenetical slope. Given snow ratios easily in the 20:1 range, think there could still be some snowfall rates of 2 in/hr as the band moves through. The last couple runs of the HRRR has backed off on its QPF suggesting the widespread 2 to 4 inch snow amounts appear to be on track. There may still be some locally higher amounts if the convective nature of the snow persists for a few hours. Otherwise snow should taper off as the frontogenesis moves southeast and very dry air continues to advect in from the northwest. There is reasonable agreement among the models that the snow should exit the forecast area around 03Z. Once the snow ends, the main concern quickly shifts to the very cold temperatures and wind chill values. Maybe the only sliver of good news is that winds should diminish through the night. However with skies clearing out and snow on the ground, lows are forecast to be in the 0 to -10 range sunday morning. Even with winds of 5 to 10 MPH, wind chill readings are forecast to be -15 to -20. So will continue with the current headlines. Models show some energy moving across the state Sunday within the longwave trough aloft. But with a very dry airmass over the area (PWs are expected to be less than 0.1), this should only lead to a few high clouds. Don`t expected much of a warm up Sunday with the high sitting over eastern KS. Highs in the teens are likely. .LONG TERM...(Sunday night through Saturday) Issued at 201 PM CST Sat Dec 17 2016 Westerly flow aloft returns over the area in the overnight hours on Monday, but likely too late for this to have much impact on overnight lows given strong initial inversions and some snow cover. Lows still fall to near zero, perhaps a degree or two warmer out west. Wind chills in the -5 to -10 range. Will have to be mindful of potential fog, given some sunshine on Sunday may boost moisture in the low levels, but a bit far out for much certainty at this time on fog. Daytime highs slowly rise through the week with near 40 Tuesday to mid 40s by Friday. Lows rise from teens to twenties in same time period. System crossing the northern Plains Thursday in EC is a little farther south in the GFS and could clip the northern part of the state, but still appears generally dry. Incoming longwave upper trof for the weekend could bring a chance for precipitation on Saturday. GFS splits the energy a bit more and has a slower eastward progression, although as of a week out both the GFS and the EC clear things out for Sunday despite their timing differences. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 537 PM CST Sat Dec 17 2016 The heavier snow has passed east of the terminals. Expect light snow with some blowing snow through the evening hours with MVFR ceilings and visibilities of 1 to 4 miles. After 4Z all terminals should become VFR. VFR conditions will continue through Sunday. && .TOP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 9 PM CST this evening for KSZ008>012-020>024-026-034>040-054>056-058-059. Wind Chill Advisory from 9 PM this evening to noon CST Sunday for KSZ008>012-020>024-026-034>040-054>056-058-059. && $$ SHORT TERM...Wolters LONG TERM...67 AVIATION...Gargan