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

Area Forecast Discussion...UPDATED
National Weather Service Lubbock TX
624 PM CST Thu Dec 15 2016 .UPDATE... Quick update to expand low clouds north more aggressively this evening and also to insert fog mention for all but our far NW counties. Regional METARs, webcams and IR low cloud imagery confirm the themes of the HRRR and RAP regarding a bullish northward surge of very low stratus with lowering visibilities. Will monitor trends for a possible dense fog advisory later this evening. && .PREV DISCUSSION... /issued 552 PM CST Thu Dec 15 2016/ AVIATION... Conditions are likely to fall to IFR by 8-10 PM at LBB and PVW, and closer to midnight at CDS. Upstream observations at SWW and BPG already show MVFR-IFR CIGs on very moist southerly winds, and this will expand north through the evening likely accompanied by some fog at times. VFR should resume toward daybreak as winds veer more SW, before ramping up to windy levels from the WSW after 12 PM. An AWW for 30+ knot winds may be issued for LBB as soon as the onset of these winds is more clear. PREV DISCUSSION... /issued 313 PM CST Thu Dec 15 2016/ SHORT TERM... Low clouds have been slow to burn off from west to east but were finally making slow progress eroding this afternoon. This has impacted temperatures and wind speeds this afternoon with areas under the cloud cover not warming up as fast as forecast and areas that have cleared seeing wind speeds increase a bit higher than previously thought. Forecast for tonight is once again challenging as the coarser model resolutions do not show low clouds returning while all of the high-resolution models (RAP, HRRR, TTU WRF) have some hints of another round of low clouds tomorrow morning. Will keep low clouds in the forecast but uncertainty remains high on when the clouds will dissipate. 18Z RAP indicates that the clouds should clear out earlier in the day Friday as southwest wind develops in the morning pulling in drier air from the southwest. Friday also has it`s share of forecast concerns as well, mainly the potential for high wind warning speeds as well as the potential for fire weather concerns. Timing will be critical tomorrow for both these elements. Models are showing a batch of fairly thick high clouds that will be across the area by sunrise Friday. These will be slow to move east but will clear the northwestern counties of the forecast area by mid-day. Clearing skies will help to deepen the boundary layer while also helping to mix stronger wind speeds aloft down to the surface. Lee surface trough gradient will also tighten through the day as wind speeds through the depth of the atmosphere increase with the passage of a weak shortwave. Models have the strongest 850 hPa wind speeds just north of the forecast area but close enough that we could see sustained speeds at or above high wind warning criteria across much of the Caprock. Uncertainty remains high enough that we will keep the high wind watch in place in hopes that the incoming shifts can possibly narrow down both the timing and aerial coverage needed for a possible warning. As for the Rolling Plains, wind speeds will likely be lower as cloud cover will keep mixing to a minimum until late in the afternoon. Narrower window for daytime mixing could mean that there is a pretty sharp gradient in wind speeds from west to east across the area. Southwest to westerly wind direction will provide good downslope warming potential and we will see high temperatures in the mid to upper 70s across the area. Unfortunately the strong wind speeds also means areas of blowing dust across the Caprock as well. See the fire weather discussion below for more details in how the forecast for tomorrow will impact fire weather concerns. LONG TERM... The one thing that is for certain on Saturday is that a strong cold front will push through, it will be windy, and it will get cold. Models still seem to be a bit slow on the fropa with the ECMWF being the closest to what is expected with the front being south of the FA by the mid to late afternoon. Temps will drop off sharply after the fropa with our northern zones dropping below freezing around or just after noon with the rest of the FA being below freezing by the early evening. A tight surface pressure gradient along and behind the cold front will allow for winds to be in the 20-25 mph range during the day. Winds will gradually decrease overnight Saturday into Sunday morning, but winds will still be in the 10-15 mph range while temps are in the teens and single digits allowing wind chill values to dip below zero. What continues to be the forecast issue for Saturday is precipitation. There should be low level and some mid level (mostly lower mid level) moisture that will be present mainly across our northern zones during part of the day. Frontogenetic forcing will be more than enough to provide enough lift for possibility rain to fall in the late morning before turning to snow in the early afternoon. The window of opportunity will be fairly short lived to see precipitation, and what precip we can see will be light at best. Flurries will be possible across the southern half of the FA as there should be enough low level moisture available during the fropa to squeeze out a few flakes. Sunday will be a cold day with morning lows dipping into the single digits to the low teens while highs will struggle to get into the upper 20s/low 30s. Monday may not be much better as lows will still be near 10 degrees and highs will only be in the mid to upper 30s. Beyond Monday the only clear part of the forecast is that we will warm up gradually. Models have been inconsistent to say the least with the evolving pattern into mid week. The GFS still has high hopes that a low will develop somewhere across northwestern Mexico which may or may not make it to West Texas. The ECMWF meanwhile has decided to keep the low offshore in the Pacific and have a rather benign pattern before pushing a cold front into the region by next Thursday. Consulting the in-house dart board model yielded a scattered plot emphasizing the unknown. For now the forecast for next week will reflect the superblend for a middle of the road solution. Aldrich FIRE WEATHER... Critical fire weather conditions remain iffy at best across the caprock due to two major concerns. The first is the timing on when wind speeds will increase. Second is minimum RH values are not expected to meet the length of time at or below 15 percent criteria. We are still expecting strong southwest to westerly wind speeds to develop in the afternoon tomorrow across all of the Caprock. Speeds will start to increase around noon, peak around 4 pm, and then start to decrease slowly after that. This will help to mix the atmosphere enough that moisture levels will potentially rise a bit in the afternoon as well. Current forecast has minimum afternoon RH values briefly falling to near 14 percent across the central South Plains for one hour before starting to climb while the rest of the South Plains and all of the Rolling Plains keeps minimum RH values above 15 percent in the same time frame. This does not meet the criteria for critical conditions. Texas Forest Service data show that energy release components are near normal for this time of year and fuel moisture levels are not in the critical range either. However, ample time for fuels to cure and strong winds should help drop fuel moisture levels in grasses in the strong winds. At the very least, elevated fire weather conditions will develop but will hold off issuing a Red Flag Watch for now. Jordan && .LUB WATCHES/WARNINGS/ADVISORIES... High Wind Watch Friday afternoon for TXZ021>024-027>029-033-034. && $$ 93
Area Forecast Discussion
National Weather Service Medford OR
243 PM PST Thu Dec 15 2016 .SHORT TERM...Tonight through Sunday...A cold and relatively dry air mass will move into the forecast area behind a front stretched from Northern California into Eastern Oregon. A wave has developed along the front which has slowed its movement, but latest satellite trends and HRRR model output suggest the front and precipitation over Eastern Siskiyou and Modoc Counties will shove east quickly tonight. Some moderate to heavy precipitation has fallen in these areas and more rain is expected this evening, so an Areal Flood Watch continues for Eastern Sikiyou and Modoc Counties through the evening. As the precipitation moves out of Modoc County, cold air will briefly meet up with the lingering precipitation, and a few inches of snow is possible there later tonight. A shortwave moving in from the northwest and some lingering moisture prompted us to keep a slight chance of mainly snow showers in for much of the area tonight, though little to no accumulation is expected with any snow. Near-freezing to freezing temperatures will affect the entire forecast area tonight, which could quickly freeze any lingering water on roadways, so travelers should be aware of the potential for ice on roadways. West side areas will likely take most of the night to reach freezing, and there is slight potential for freezing fog though conditions suggest low clouds instead of fog at this point. At the coast, with lows expected to be in the low 30s, a Frost Advisory at NPWMFR has been maintained for that area. Tomorrow night, clearing skies and light winds, along with 850mb temperatures around -7C over Medford (which is about the coldest 5% for this time of year) will likely yield the coldest night of the next several. Fresh snowpack will help East Side temperatures dip well below zero in favored locations like Chemult. West of the Cascades, barring any widespread freezing fog forming early in the night, temperatures will dip to the upper teens to low 20s. Residents should take precautions to mitigate any impacts this cold weather might have. Cold nights are expected through Sunday night at least. .LONG TERM...Monday through Thursday...After a brief break in the precipitation over the weekend, the storm track will become active again next week. The models are in good agreement that two significant frontal system will affect our area next week, and while there are some differences in timing and strength, the differences are not significant enough to worry about at this time. System number one may bring rain to the north coast as early as Monday, but all areas should see some precipitation Monday night and Tuesday. Snow levels will surge ahead of this system, so while precipitation may start as snow in the colder east side locations, it will likely be rain over all but the higher mountains most of the time. There will be a break Wednesday, then system two arrives Thursday. Snow levels will be a little lower ahead of this system, so much of what falls from the Cascades east will be snow with rain on the west side. Models are consistent in showing cooler air moving in Friday with lowering snow levels and continued precipitation. This may result in some impacts from snow at lower elevations from Friday into next weekend. While this is beyond the current forecast window, that will be right in the heart of the Christmas travel window, so it`s worth keeping an eye on if you plan to travel through southern Oregon or northern California for Christmas. -Wright && .AVIATION...15/18Z TAF CYCLE...Low clouds will be stubborn in many areas today, but should gradually lift to MVFR and local VFR at the terminals this afternoon as a front moves off to the east. Far eastern areas in Lake and Modoc counties will see rain with reduced CIGs/VIS as the front crosses the area, then conditions will worsen briefly tonight as rain changes to snow before ending. At the terminals tonight, clouds will likely lower and BR/FZFG will re-form reducing conditions to IFR or LIFR. There is even a slight chance of a brief snow shower at the terminals tonight. -Wright && .MARINE...Updated 845 AM PST Thursday 15 December 2016...Offshore high pressure will build west of the waters today with light to moderate north winds. A mix of wind waves and fresh south swell will keep waters choppy, but below small craft advisory levels over much of the area today. However, borderline small craft conditions are possible in the southern outer waters late this afternoon and evening. Calmer conditions are expected Friday into next weekend. A cold front may bring strong south winds and seas early next week followed by a very high and very long period swell. -Petrucelli/Wright && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Frost Advisory from 2 AM to 9 AM PST Friday for ORZ021-022. Frost Advisory from 1 AM to 9 AM PST Saturday for ORZ021-022. Freeze Watch from late Friday night through Saturday morning for ORZ021-022. CA...Flood Watch until 6 PM PST this evening for CAZ081>083. Flood Watch until 10 PM PST this evening for CAZ084-085. Pacific Coastal Waters...Small Craft Advisory for hazardous seas from 1 AM to 10 AM PST Friday for PZZ356-370-376. $$ NSK/TRW/TRW