Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/08/20

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
620 PM EST Tue Jan 7 2020 .AVIATION... Passage of right entrance region over southern parts of the area later this evening continues to show some promise for a several hour window of enhanced snow shower activity mainly KPTK south, but will back off timing of TEMPO group to 03z-05z. Main cold front pushes through the area behind this feature with a wind shift from SW to NW. Wind gusts overnight will top 25 knots within CAA behind this front. Cigs are problematic into Wednesday with a general lower VFR deck in place off/on into midday Wednesday with clearing late in the forecast. Winds will also diminish late in the day Wednesday and become basically calm by evening. There will likely be snow flurry activity late tonight into Wednesday morning, but signal for any more significant snow shower activity does not support a mention in the forecast ATTM. For DTW...Concern is brief IFR snow shower later this evening with wind gusts 25 knots or more overnight into the first part of Wed morning as direction veers to WNW. DTW THRESHOLD PROBABILITIES... * High for ceilings aob 5kft later this evening again and late tonight into Wed morning, low confidence by midday Wednesday. && .PREV DISCUSSION... Issued at 333 PM EST Tue Jan 7 2020 DISCUSSION... Latest water vapor imagery shows large upper level low over northern Ontario with deep southwest flow over the Central Great Lakes, resulting in another mild day as temperatures have reached into the upper 30s to lower 40s. Radar activity over Lower Michigan matching up nicely with lead 850-700 MB Theta-E/Specific Humidity (up to 2 g/kg )/pre-frontal trough. This narrowing moisture axis and activity will slide east around 23Z. Additional snow shower activity expected to move in later this evening with the help from Lake Michigan. Quick glancing blow of cold air to track through the Central Great Lakes tomorrow morning, as 850 MB temps around -20 C extend to Saginaw Bay, with -18 C extending toward the Ohio Border. Westerly flow this evening veering around to the unfavorable northwest flow tonight for lake effect, coupled with very dry nature of the Arctic airmass and crashing inversion heights to limit activity to mostly flurries on Wednesday, with a decent amount of sunshine even likely. As the arctic front passes through late this evening, there are still plenty of indications (ARW/Regional GEM) there will be a quick burst of snow along the front. Note the clouds/radar returns near the Quad Cities which may be able to provide the favorable backdrop of 700 MB support/left exit region of the upper level jet (>110 knots), although the bulk of the forcing looks to be tracking just south of the Michigan border through this evening, with the aggressive mid level dry slot then taking hold after midnight over southeast Michigan. Still, various soundings, RAP for instance, do show a brief window of good supersaturation with respect to ice and capes (50+ J/kg) intersecting the DGZ late this evening/around midnight, and still favor localized accumulations of a dusting to 1 inch. As the colder and dry airmass takes hold tonight, the modest cape/supersaturation with respect to ice looks to reside mostly above/colder than -15 C isotherm, and thus probably looking at mostly flurries around Wednesday morning with the dry sub cloud layer around 2 kft. Despite the lack of snow cover in place, the deep/cold airmass should hold maxes in the mid/upper 20s, in line with the latest guidance. Broad longwave troughing over western half of North America Wednesday night, with one piece of upper level energy/surface low pressure tracking through the Midwest on Thursday, and through Lake Superior Thursday evening. A decent Pacific Moisture plume/PW Values up near 0.75 inches to track through southeast Michigan during the evening. The low level moisture advection/isentropic ascent coming over the cold ground should be enough to generate light rain showers, as strong southwest low level jet brings 5-8 C (925 MB dew pts) into southeast Michigan Friday morning. Frontal boundary looks to be stalling out as 500 MB heights rise in response to summer-like upper level ridge (591+ DAM at 500 MB) center building near the Bahamas. Sprawling Bermuda surface high (1040+ MB) will be pumping Atlantic and Gulf of Mexico moisture north on Friday as a strong storm system exits the Four Corners region. Meanwhile, northern stream/arctic airmass will be tracking through the northern Plains, and the race will be on to get to the Great Lakes Region, determining our precip type. With the unusually high moisture content for January standards, even if we do end up on the mild/rainy side (which is looking more likely, supported by 12z Euro and ICON), could have some flood issues with potential 3+ inch total rainfall, followed by some very strong wind as the cold advection/dry slot kicks in on Sunday. MARINE... Passage of a clipper system traveling across the southern Provinces of Canada will allow an Arctic front to travel across the Great Lakes late this evening through late Wednesday morning. Post-frontal northwest flow will hold mixing depths and will tap into stronger winds aloft, allowing 25-30 knot gusts to persist across the open waters and nearshore zones now through Wednesday morning. Strongest winds are expected across northern and central Lake Huron during the mid and late morning hours on Wednesday, where near-gales to low-end gale force winds (around 35 knots) will be possible. Have decided to preclude the issuance of a gale warning at this time as the window to see persistent gale force winds is short. Small craft advisories are in effect for all nearshore zones. Additionally, prolonged northwest flow will activate lake effect snow, especially along the arctic frontal boundary, where snow squalls are expected given the instability in place over the warmer waters relative to the air mass. All of Lake Huron and the Saginaw Bay will have the best chance to see squalls late tonight and overnight, where brief but drastic reductions to visibilities will be expected with squall activity. Snow squall threat and associated winds will diminish by Wednesday afternoon as instability over the lakes decreases, with freezing spray holding through the bulk of Wednesday. A strong warm front is then forecasted to push north into the Great Lakes Thursday morning and afternoon, which will bring the next chance for strong winds across the lakes. Much higher confidence regarding gusts between 35-40 knots across Lake Huron on Thursday given the impressive low-level wind field that moves in. A gale watch remains in effect for Lake Huron. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Advisory from midnight tonight to 4 PM EST Wednesday for MIZ049. Lake Huron...Gale Watch from Thursday morning through Thursday evening for LHZ361>363-441>443-462>464. Small Craft Advisory until 10 AM EST Wednesday for LHZ442-443. Small Craft Advisory until 5 PM EST Wednesday for LHZ421-441. Small Craft Advisory until 10 AM EST Wednesday for LHZ422. Lake St Clair...Small Craft Advisory until 10 AM EST Wednesday for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EST Wednesday for LEZ444. && $$ AVIATION.....DG DISCUSSION...SF MARINE.......AM You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Grand Rapids MI
929 PM EST Tue Jan 7 2020 LATEST UPDATE... Update/Marine .SYNOPSIS... Issued at 307 PM EST Tue Jan 7 2020 -Lake effect snow showers into Wednesday Morning; slick Wednesday morning commute possible -Heavy Rain Threat Thursday Through Saturday Night -Potential travel impacts over the weekend from freezing rain, sleet and snow mainly north && .UPDATE... Issued at 929 PM EST Tue Jan 7 2020 The shortwave that caused the area of snow showers to cross Southwest Michigan between 7 pm and 9 pm is exiting the area now. So there will be a quiet period in terms of snow showers until the arctic front reaches this area. Currently front can be seen as a band of west to east clouds from near GRB to TVC (just south of both at 920 pm actually). There is a band of snow showers on the radar associated with that too. That band will move south and be in our area (I-96) by midnight or so. After that moves through temperatures will fall down into the teens north and lower 20s south. Snow showers will become widespread west of US-131 but due to the shallow depth of the inversion, will not be heavy enough to result in more than 1 to 2 inches of snow. The will likely be some blowing and drifting even so due the gusty northwest winds. Still I do not see this getting nasty enough to put out a headline UPDATE Issued at 645 PM EST Tue Jan 7 2020 The snow showers are already developing, more in line with the NMM than the HRRR so I believe once again the models are underplaying this event. There are two snow shower events actually, the one associated with the cold front (which is what we are seeing now) and the one associated with the real lake effect in the deep cold air. That moves in around midnight and should last until the back edge of the upper jet moves over this area, taking us out of the deep cold air. I did not change our overall forecast, 1 to 2 inches for a max snowfall makes sense given the short duration of the event and the inversion heights only to 5000 ft to 6000 ft over night. That being said, our high res models do suggest the strongest lift centered in the DGZ toward morning, so there could be some decent snow showers around even so. All of this should slowly weaken during the mid to late morning Wednesday as the deep cold air moves out of the area. && .DISCUSSION...(This evening through next Tuesday) Issued at 307 PM EST Tue Jan 7 2020 -Lake effect snow showers into Wednesday Morning; slick Wednesday morning commute possible A brief but sharp cool down occurs tonight into Wednesday. Lake effect snow showers will be on the increase as a result. Inversion lower considerably to around 5K ft from 06z to 18z...which should limit the impacts risk. The DGZ is show to be moist so high pops are warranted. Surface temperatures are projected to fall through the 20s tonight. -Heavy Rain Threat Thursday Through Saturday Night There has been a trend in many of the models towards a warmer scenario. Based on the latest runs...less in the way of snow is expected. With a more northern track of the low along the baroclinic zone...greater amounts of Gulf moisture are projected into the region...becoming very anomalous. At this time...most models are showing several inches of precipitation...which will need to be monitored very closely given the potential impacts. -Potential travel and power outage impacts over the weekend from freezing rain, sleet and snow mainly central and north Tough call this far out how this one will go down. Stay tuned as there is still a fair amount of uncertainty on the storm track. We know the precipitation will be heavy at times. The type of precipitation is the challenge. Looking at trends...the warmer scenario is pushing the main snow risk further north...and could support a band of heavier freezing rain just to the south of the heavier snow area. There are concerning ingredients showing up. Shallow cold air will be advecting in as the main wave will be lifting up through the region. This would raise the risk for a swath of heavier freezing rain somewhere in the CWA. To the north of the elevated warm layer...mainly snow would be expected. The freezing rain risk looks the greatest over central parts of the CWA. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 645 PM EST Tue Jan 7 2020 The snow showers are already developing, more in line with the NMM than the HRRR so I believe once again the models are underplaying this event. I have some IFR conditions in our TAF sites near and west of US-131 tonight and MVFR on the more eastern TAF sites. Even so do not be surprised if briefly we have visibilities going down to near a one mile at times between 03z and 12z at the more western TAF sites. Ceiling should become MVFR by 06z or so as the colder air comes in. With the upper wave that brought in the cold air moving out so quickly Wednesday I believe skies may actually clear or at least become scattered by 21z at most of the TAF sites on Wednesday. It will be breezy tonight into midday Wednesday as the core of the cold air moves in. Winds let up by midday Wednesday as the deeper cold air moves out of the area. && .MARINE... Issued at 929 PM EST Tue Jan 7 2020 We continue to see gale force wind gusts in the near shore and with the passage of the arctic front around midnight, there is a second maximum in the wind, which of course is what is helping to bring in the arctic air. So I (after coordinating with near by offices) extended the gale warning till 9 pm Wednesday. I did not change the coastal flood advisory. That seems fine as is. && .HYDROLOGY... Issued at 307 pM EST Tue Jan 7 2020 All rivers have now fallen below flood stage, although the Grand River at Robinson Township remains very high as gusty west winds are pushing some water back up the river mouth. Attention now turns to the growing possibility of widespread very heavy rain across parts of our area late this week and into this weekend. There has been a very concerning trend among the models in the last 24 hours toward the possibility of incredibly heavy rainfall for our area for this time of year. Guidance is suggesting much of the area (I-96 and southward) could see 2 or even 3 inches of rain in the Friday/Saturday timeframe. Needless to say, with soils saturated and river levels already high, this has the potential to produce more significant river flooding than we`ve seen at any other point in the last year. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Lakeshore Flood Advisory until 11 AM EST Wednesday for MIZ037- 043-050-056-064-071. LM...Gale Warning until 9 AM EST Wednesday for LMZ844>849. && $$ UPDATE...WDM SYNOPSIS...MJS DISCUSSION...MJS AVIATION...WDM HYDROLOGY...AMD MARINE...WDM
Area Forecast Discussion
National Weather Service Lincoln IL
920 PM CST Tue Jan 7 2020 .SYNOPSIS... Issued at 330 PM CST Tue Jan 7 2020 A weak cold front will move southeast through the region tonight before high pressure builds back into area during midday Wednesday. Dry weather is expected to continue across the area through early Thursday. A series of storm systems are then expected to eject northeast across the area from Thursday afternoon through Saturday evening, potentially bringing 2 to 5 inches of rain to central and southeast Illinois from Thursday night through Saturday. This will be followed by a wintry mix with some accumulating snowfall possible for parts of central and especially northwest IL overnight Friday night and Saturday. && .UPDATE... Issued at 915 PM CST Tue Jan 7 2020 A weak cold front passing through Illinois tonight will trigger a wind shift from SW to N-NW. Gusty winds could develop behind the front for at least a few hours after midnight tonight. Gusts back in Iowa are up between 20-25 mph at times. No precipitation will occur with this FROPA due to an abundance of dry air below the cloud bearing layer (10K FT). All radar returns have not resulted in any precip in our area as a result. Cold air filtering into Illinois behind the front will push lows down into the low 20s in our northern counties. The gusty winds will put wind chills into the single digits above zero late tonight and early Wednesday morning. Cool high pressure will settle into the area tomorrow, with north winds shifting to the E and SE by the end of the day. Our coolest highs of the next 7 days will come tomorrow, with readings topping out in the lower 30s north of I-74 to the low 40s south of I-70. The current forecast database has a decent handle on the short- term forecast, and no formal update will be needed this evening. && .SHORT TERM...(This evening through Wednesday) ISSUED AT 330 PM CST Tue Jan 7 2020 Mid afternoon surface map shows 1028 mb high pressure over east Texas and ridging into the mid MS river valley. A cold front was over over central WI/IA/KS and associated with a weak short wave. This feature was spreading broken to overcast mid/high clouds at or above 10k ft over northern 1/3rd of IL including northern CWA. Mostly sunny skies still prevailed over rest of central and se IL at mid afternoon. Breezy west winds 10-18 mph and gusts of 18-25 mph prevailed over central IL, with temps mostly in the low 40s central IL and mid 40s in southeast IL. Cooler upper 30s in cloudier areas of Knox, Stark and Marshall counties with Lacon 38 and Galesburg 39. The cold front will track se thru central IL this evening and southeast IL overnight and should pass thru dry, with flurries possible in northern IL this afternoon/evening. Mid level clouds will decrease later this evening and overnight with fair skies by daybreak Wed. WSW winds diminish early this evening and veer NW behind the cold front overnight. Lows tonight range from upper teens to near 20F northern CWA to the mid 20s in southeast IL. High pressure over the Dakotas settles into the upper MS river valley Wed and ridges across IL, bringing ample sunshine and lighter winds tomorrow. Cooler highs Wed in the mid to upper 30s, ranging from lower 30s north of I-74 to lower 40s in Clay, Richland and Lawrence counties. .LONG TERM...(Wednesday night through Tuesday) ISSUED AT 330 PM CST Tue Jan 7 2020 High pressure ridge exits east over the eastern Great Lakes and mid Atlantic States overnight Wed night with a warm front lifting northward over central IL. Evening lows Wed night in the upper 20s and lower 30s (coolest ne CWA) then slowing rising overnight Wed night with increasing southerly flow. Stronger south winds on Thu bring milder highs in the lower 50s, with some mid 50s over sw CWA and se IL. Most areas should stay dry Thu morning, then see a good chance of light rain showers developing during Thu afternoon in strong warm air advection pattern and cold front approaching nw IL by sunset Thu. 1st wave of widespread rain showers to occur Thu night into Friday as cold front slowly moves into heart of central IL by midday Fri. Mild lows Thu night in the mid to upper 40s, except upper 30s and lower 40s nw of the IL river behind cold front. Mild again on Fri with highs ranging from 45-50 nw of the IL river to the upper 50s/lower 60s in eastern/se IL. 2nd wave of heavier rain showers to eject ne over area Fri night and Saturday as more energy ejects ne from the southern plains toward the southern Great Lakes. Models have trended further nw with heavier qpf and also have lower snowfall amounts with slower changeover to snow overnight Fri night and Sat. The heaviest qpf appears to be Fri night and Sat over central and se IL and between 3-5 inches of rain expected by early Sat evening over se half of CWA (highest se of I-70), with 1.5-3 inches of rain from I-55 nw. Rain to chance to snow over the IL river valley late Fri night and Sat, and changeover to snow as far east as I-55 on Sat, then turning to light snow over rest of central IL Sat evening in deformation zone, while se IL likely stays rain into Sat evening. A couple inches of snow possible late Fri night and Sat along and nw of I-55 with little or no snow accumulations in eastern/se IL. Temps likely slipping during Sat with increasing cold air advection on back side of storm system. Still some model difference with track of heaviest rain and ending during Sat night. Issued ESF for se half of CWA for 3-5 inch rain expected and flooding potential Thu night thru Saturday. This rainfall could reach near or even above our normal January precipitation in just a couple days. Dry weather returns late Sat night and Sunday as weak high pressure settles into the area. Models show a weak northern stream system clipping nw/northern IL Mon while a southern stream system mainly se of the Ohio river. Much of area has little or no qpf on Mon and Mon night. Ecmwf then spread qpf ne over area on Tue while GFS and GEM are dry. Stayed close to consensus/blend for forecast next work week which keeps lows pops in there especially se IL though confidence is low. Cooler highs Sunday in the mid to upper 30s central IL and low to mid 40s southeast IL. Temps moderate into the 40s Mon/Tue with lower 50s in southeast IL. So overall above normal temperatures look to continue across the area into next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 546 PM CST Tue Jan 7 2020 VFR conditions are forecast to continue across the central IL airports through 00Z/6 pm on Wed. Overcast to broken mid/high clouds generally at or above 10k ft will push across all terminal sites this evening, due to a weak shortwave in the upper level flow. Skies will clear out from NW to SE by midnight. A weak cold front over far nw IA into se Nebraska will slide se to the IL river valley by late this evening, and thru DEC and CMI during early overnight. W-SW winds at 5-8KT will veer to the NW after cold FROPA tonight. HRRR is indicating some gusty NW to N winds will develop in the wake of the front, with sustained speeds of 10-14KT and gusts possibly between 20-25kt. Those gusts should subside by morning on Wednesday, as winds shift through the northerly directions to E-SE Wednesday afternoon. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Shimon SYNOPSIS...07 SHORT TERM...07 LONG TERM...07 AVIATION...Shimon
Area Forecast Discussion
National Weather Service North Platte NE
636 PM CST Tue Jan 7 2020 .SHORT TERM...(This evening through Wednesday night) Issued at 242 PM CST Tue Jan 7 2020 A 1032 mb high pressure center will cross North Dakota this evening and be centered across central Minnesota by Wednesday morning. This will drive a cold front southward into the area tonight. The front will stall from southeast to northwest across the area late tonight. Low-level moisture will pool and expect an area of low stratus clouds to develop along and north of the front across the Sandhills and north central Nebraska. Also added some patchy fog as the RAP and HRRR hint at low visibility in spots, mainly across the Sandhills after midnight. The front will attempt to lift northward as a warm front Wednesday. South to southeast low-level flow will keep low-level moisture in place with the potential for low clouds to linger across north central Nebraska most of the day. Have limited highs to mid 30s in that area, with lower and mid 40s across western and southwest Nebraska. .LONG TERM...(Thursday through Tuesday) Issued at 242 PM CST Tue Jan 7 2020 Thursday into Friday a long wave trough will be digging across the western CONUS. This is forecast to dig into the Southern Plains and bring a round of heavy rain and T-Storms to the Mississippi Valley region during the weekend. Still appears that our area may see some light snow Thursday night into Friday as the upper trough passes, but some uncertainty remains here as strong northern stream energy will be approaching at the same time. This could shunt much of the moisture south and east of the area. The NAM and ECMWF are a bit slower with the northern stream and allow for a period of light snow before it arrives. The GFS remains quicker and keeps much of the precipitation southeast of the region. Will increase pops a bit with agreement between the NAM and ECMWF. Regardless only around an inch or so of snow is expect at this time as the northern stream will quickly shut down the snow when as it arrives. Arctic air that dives south into the area Friday behind a cold front, with highs only reach the upper teens across portions of north central Nebraska. Temperatures will moderate some over the weekend, with high temperatures back into the 30s all areas by Sunday. Southwest flow aloft develops during the weekend as another long wave trough digs southward through the Pacific northwest toward the central and southern Rockies. Temperatures will moderate some with highs back into the 30s most areas by Sunday. We are monitoring the potential for some fairly cold air to move south into the region later next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 607 PM CST Tue Jan 7 2020 A weak cold front currently roughly bisects the area from northwest NEB to south central NEB and will become stationary tonight. Otherwise, latest satellite imagery shows passing high clouds across western NEB with lower ceilings, albeit still VFR, across central and eastern SD. Concerns turn to stratus and patchy fog potential. Current thinking is ceilings dropping to MVFR, perhaps even IFR, late this evening across parts of the Sandhills towards central NEB. Patchy fog will then be concerned as well, however, thinking visibility restrictions will be 1/2 mile at worst. While conditions improve early tomorrow, mostly cloudy skies will prevail along with increased southerly winds. Gusts up to 25 mph Wednesday, highest across northern NEB. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Taylor LONG TERM...Taylor AVIATION...ET
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 345 PM CST Tue Jan 7 2020 Overview: Warmer than normal temperatures through Thursday. The forecast becomes more complex for Friday with a potential winter storm/accumulating snow that develops over parts of Nebraska and there is a transition zone to rain/mix near the Kansas/Missouri border. Tonight through Friday: The latest surface analysis shows an area of surface low pressure over Iowa with surface winds veering from the west to northwest and north with a cold frontal passage. The brunt of the cold air will remain well to the east of the area across parts of MN into the Great Lakes, although some cooling is expected for tonight into . Wednesday. A persistent area of clouds has developed with the isentropic lift/h85/h7 warm air advection near ONL into parts of northeast Nebraska. A 40kt low level jet strengthens tonight and continues Wednesday through parts of the Central Plains. We don`t have any precipitation forecast with this feature beyond clouds. RAP RH progs show a band of clouds may persist through tonight with mid clouds displaced a little more northward overnight Southeast surface winds strengthen to 10 to 20kts and gusty Wednesday with high temperatures in the 30s and 40s. A mid-level trough over the Rockies swings eastward Wednesday night. Brisk south flow and patchy clouds should yield warm minimum temperatures Thursday morning. We currently have lows in the lower to mid 30s. Temperatures are forecast to drop below these levels Thursday night by midnight. Something to watch-the record warm minimum are around 35 Thursday. Highs Thursday are expected to top out in the 40s and 50s. The surface low/initial mid level trough swings through Thursday and taps into moisture south of the forecast area. This will be a big weather maker for much of the U.S. to our east into the weekend. Friday...a north to south mid-level trough combined with a strong upper level jet will begin to spread snow from CO/WY into parts of Nebraska and South Dakota. Farther south, rain will re-develop, lifting northward over the front across Kansas and Missouri. There is still decent model disparity in how strong the forcing will be across KS and Nebraska into Iowa and thermal fields/resultant QPF/snow/mix. There is general agreement with a precipitation signal (NAM/EC/CMC/GFS/SREF) for precipitation south of a line from the Platte River to Little Sioux Iowa southward and especially I80 southward. The GEFs plumes have a spread of an inch or 2 to 9 inches of snow. The NAM is the most robust of the deterministic models with snow accumulations Friday afternoon into Friday night, lasting into Saturday morning. The warmer air does make it farther north with the transition in southeast Nebraska and southwest Iowa. The GFS is more all snow and on the lighter end of accumulations. Our current forecast has a couple of inches of light snow. Friday Night through Monday: Surface high pressure builds in for Saturday and have lowered highs to the teens and 20s. Near or below normal temperatures are forecast in the 20s and Thursday Sunday Through Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 539 PM CST Tue Jan 7 2020 VFR conditions will prevail over the region through 00Z Thursday, with cloud bases AOA 8,000 ft and unrestricted visibility. Winds will become gusty out of the east/southeast (15 to 20 kt, gusts 20 to 30 kt) by mid morning Wednesday (15Z) and continue through 00Z Thursday. All of the TAF sites (KOMA, KOFK, and KLNK) will see impacts from the winds. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Zapotocny AVIATION...Albright
Area Forecast Discussion
National Weather Service Reno NV
328 PM PST Tue Jan 7 2020 .SYNOPSIS... A couple of weak weather systems will bring breezes and chances for light snowfall tonight through Thursday. Temperatures will cool to near average. Additional storm systems this weekend into next week could bring increased snow amounts, especially for the Sierra, along with below average temperatures. && .SHORT TERM... The main adjustments in the short term were to hoist a lake wind advisory for Lake Tahoe through tonight and slightly increase snowfall amounts in west-central NV Thursday morning. Winds have picked up (gusts 20-35 mph) this afternoon for many spots across eastern California and extreme western Nevada as low pressure nears the Pac NW coast. The lower valleys of western Nevada have been slower to pick up wind-wise as full mixing has been slower there despite sustained winds around 50 mph over the Sierra ridges. Winds could pick up for more locations along the Sierra Front/Hwy 395 corridor into this evening as a cold front nears the area, with isolated gusts 40-45 mph possible in wind- prone areas as indicated in the latest HRRR guidance. Scattered to numerous snow showers will break out in the northern Sierra into northeast California late this evening and overnight as the aforementioned low pressure moves over northern CA and NV. Snowfall is expected to remain light with only up to around 2 inches expected near the crest. As the system`s cold front is expected to push out ahead of the main forcing tonight, deep forcing (especially east of the Sierra) looks limited with spillover expected to be light and hit or miss into western Nevada with little or no snowfall acccumulation. Although a few snow showers could linger across northeast CA and the northern Sierra Wednesday, minimal additional accumulations are expected. Wednesday night and Thursday morning, attention turns to a bit more potent disturbance set to move over the Sierra in a slider- like fashion. The national blend of models (NBM) continues to indicate a good chance for at least a dusting to 0.5" for many areas across western NV, with probabilities good for an inch or two across far northeast CA (including Surprise Valley) and perhaps 2-4" for the northern/central Sierra near the crest. With all this in mind and the favorable track for at least some accumulating snow in western NV, POP was raised further for Thursday with snow likely in most areas. This could certainly cause issues for the Thursday morning commute in western and west-central NV given the typical traffic volume, especially if the heaviest snow showers hit between 6-8 AM. All we can say is be ready for a slick morning commute Thursday and don`t wait until the last possible minute to leave for work as travel speeds my be significantly affected. Thursday`s wave exits in the afternoon for a rapid shutoff to snow showers. Friday will be another break between systems with dry conditions and temperatures topping out near average. -Snyder .LONG TERM...Friday evening through mid-January... No major changes to the overall forecast thinking in the long term as a large area of low pressure slowly deepens over the west coast through mid-January. The evolution remains a bit chaotic with multiple short waves digging the trough deeper and farther west for about the next 10 days or so. This will most likely allow a decent winter storm into the region...eventually. The first couple waves this week are relatively fast moving, mainly nuisance waves, dropping into the region from the northeast. This angle of attack doesn`t allow for much moisture into the systems and gives them less then ideal orographic potential. Nevertheless these waves will create increased winds (especially along the higher terrain), bring chances for light snow accumulation, and begin to usher in more winter-like temperatures into our region that has been 5-10 degrees above average to start 2020. The next wave is expected Friday night into Saturday with current projections starting to spread snowfall into the Sierra early Saturday morning, so travel over Sierra passes on Friday evening is currently forecast to by dry. Cold air dropping in from the north should keep precipitation in the form of snow at all elevations, but overall amounts are expected to be pretty meager, mainly in the 2-6" range in the Sierra with another possibility of a dusting to half an inch in western Nevada. Chances for stronger storms increase next week as the longwave trough is forecast to continue to deepen and shift west. There remains significant inconsistencies in timing and overall strength of a more significant storm next week, however, we can say there is increasing chances for stronger storms through next week. Currently it looks like there are two time periods of possible for a stronger storm, early next week and again closer to the MLK weekend. -Zach && .AVIATION... Winds have picked up over ridges (gusts 40-50 kts) this afternoon ahead of the next quick moving disturbance, with peak ridge gusts 60-70 kts expected tonight. Valley surface winds have become breezy in northeast CA and into far western NV as well, with peak gusts to around 25 kts expected for terminals through tonight. There is also a 30-40% chance for gusts 30-40 kts in Mono County including KMMH (as indicated in HRRR simulations). While this isn`t a significant winter storm, there is potential for mountain wave turbulence as well as local areas of LLWS through tonight. For NE CA and Tahoe terminals, light snow showers are most likely from 06-12Z tonight into early Wednesday, producing periods of IFR conditions and up to 1" of runway snow accumulation at KTRK-KTVL and possibly a dusting at KSVE. Elsewhere, nothing to a trace amount of snow is expected tonight through Wednesday. Another round of light snow could bring IFR conditions and up to 2" of runway snow accumulation to the Sierra terminals early-mid morning Thursday, with smaller snow amounts (possibly to 1/2" or so) for western NV terminals including KRNO-KCXP-KMEV. There is a chance that higher amounts to an inch or two could fall out into west-central NV including KLOL and KNFL; however, where the heaviest bands of snow will wind up are highly unpredictable at this time with low confidence in the location. -Snyder/MJD && .REV Watches/Warnings/Advisories... NV...Lake Wind Advisory until 4 AM PST Wednesday for Lake Tahoe in NVZ002. CA...Lake Wind Advisory until 4 AM PST Wednesday for Lake Tahoe in CAZ072. && $$ For more information from the National Weather Service visit...