Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/03/19

National Weather Service Albany NY
1022 PM EDT Tue Apr 2 2019 .SYNOPSIS... A storm system traveling offshore the Eastern Seaboard will bring some clouds tonight, along with spotty light rain or snow across portions of western New England. Windy conditions will develop behind the departing storm for Wednesday afternoon and evening. The next chance of widespread precipitation looks to be on Friday, as a frontal boundary brings some rain and snow to the area. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 1015 PM EDT...Regional radar depicts bands of precipitation, mainly rain, extending from southwest to northeast just off the mid-Atlantic seaboard. Another smaller and weaker band was across Long Island and southern Connecticut. Per the 00Z model hires model suite, question just how far west this light precip shield gets as trends are now a little further eastward. We will ever so slightly nudge the PoP/Wx grids a bit further east as we will continue to monitor trends closely overnight. Under considerable cloud coverage, temperatures have been slow to decline as we will slow down the nocturnal descent but keep overnight lows in place per latest runs of the LAV/LAMP. Otherwise, minor tweaks to the hourly grids per observations. Prev Disc...High pressure is now located well southeast of Nova Scotia and continues to depart away from the area. Meanwhile, low pressure off the coast of eastern North Carolina continues to intensity and deepen. Although the bulk of the clouds ahead of this strengthening storm are still over the mid- Atlantic states, mid and high level clouds are steadily increasing over the area. Most locations should be mostly cloudy by later this evening with overcast skies expected through the duration of the overnight hours. With the developing gradient and fairly decent mixing in place (as usual this time of year thanks to the strong solar insolation and lack of moist vegetation), southerly winds have been gusty this afternoon, especially in north- south oriented valleys, such as the Hudson Valley. Winds have been gusts 20-30 mph at times. These winds will start to diminish this evening as nocturnal effects takes over and winds should be fairly light for the overnight hours. The low pressure looks to track northward offshore the mid- Atlantic states for tonight and should be just southeast of southern New England by daybreak Wednesday. Latest model guidance, including the 3km HRRR show this storm being a bit too far south/east to have much of an impact on our weather. Will continue slight to low chc POPs across western New England, but it looks like only far southeastern Litchfield County could be brushed with a few hour period of light rain for late tonight. If the storm does track a little further west than anticipated, then perhaps some light rain (mixed with wet snowflakes at the highest terrain) could also impact the Berkshires and southern VT, but any amounts look very light. With the clouds, temps won`t be as chilly for tonight. Overnight lows look to fall into the mid 20s to mid 30s, with the coldest temps over the Adirondacks. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Coastal storm offshore of eastern New England will be departing during the day on Wednesday as it continues to deepen. Meanwhile, a northern stream shortwave and associated surface frontal boundary will be moving from the Great Lakes towards the Northeast for Wednesday as well. There won`t be much moisture with this feature, but cannot rule out a few sprinkles or light rain showers across the Adirondacks as it passes through the areas during the late morning through early afternoon hours, but any rainfall looks just a few hundredths at best. Behind this frontal boundary, westerly winds will strengthen aloft and colder air aloft will quickly move into the region. 12z model soundings suggest this could allow for a period of deep mixing on Wednesday, with mixing as deep as 700-750 hpa. This will allow for very gusty winds to reach the surface, especially across areas that channel westerly flow such as the Mohawk Valley, Capital Region and Berkshires. Winds also look strong across high terrain areas of southern Vermont, the Adirondacks and Catskills. Winds will be 15 to 25 mph with gusts of 30 to 50 mph at times for the mid-afternoon through the evening hours. Based on this, have issued a Wind Advisory for much of the area from 2 PM through 10 PM Wednesday. High temps should reach the 40s across the higher terrain and 50s for valley areas. Strong winds should start to diminish late Wednesday evening, especially after midnight. Still, enough of a surface gradient will remain in place to keep winds breezy through the overnight hours. Overnight lows will fall into the 20s to mid 30s for the area with skies becoming fairly clear. On Thursday into Thursday night, high pressure will be building towards the area from the Great Lakes. The high still will be far enough away that during peak heating on Thursday, some breezy conditions (gusts up to 25 mph) will still be possible. Otherwise, it will remain dry and fairly sunny on Thursday. Some clouds may start to return towards the area by Thursday night as the next storm system rapidly approaches from the southwest. Temps look seasonable with highs in the 40s to low 50s for Thursday and lows in the 20s and 30s for Thursday night. && .LONG TERM /FRIDAY THROUGH TUESDAY/... After a system brings rain and rain/snow to the higher terrain during the day Friday into Friday night, uncertainty increases heading into the new week. While the pattern turns more active and chances for precipitation increases, the timing, track and intensity of various shortwaves remains uncertain. Users should continue to check back for updates as we fine tune the forecast over the coming days. We start the long term on Friday with a near 1035hPa high sliding eastward into New England with a weak, open shortwave progressing northeastward out of the Ohio Valley. Strong subsidence and abundant mid-level dry air from our departing high pressure suggests that precipitation should be slow to push into eastern NY/western New England. Therefore, we continue to favor the ECMWF solution which has consistently shown a slower start the past fews runs. A slower onset also means that our chances for any wintry mix during the cooler morning hours has lowered. The ridge axis gradually crosses through our region during the day Friday resulting in thickening clouds and eventually warm air advection driven precipitation, especially by the afternoon. Despite warming aloft, we favored the cooler temperature guidance for Friday. With our high anchored off the coast of New England, southeasterly winds should lead to a cooler/marine influenced air mass over region. Plus, low dew points in the 20s to low 30s combined with increasing showers should cool the column down adiabatically via wet-bulbing processes. Expect highs to only reach into the upper 30s to mid 40s which is about 10 degrees below normal for early April. As our system`s warm front reaches into the mid-Hudson Valley and southern New England Friday night, a 45-50kt low-mid level jet in its warm sector should result in increased moisture transport and better chances for widespread and steadier periods of rain over our region. We also notice hints in the latest model guidance of a secondary low developing along the boundary which also would provide focus for enhanced precipitation. Total QPF by 12z Saturday looks to range 0.25 - 0.75" with localized higher amounts in the southern Adirondacks and Greens which we commonly see in these southwest flow regimes. The northern extent of our warm front remains uncertain but if it only reaches into the Capital District which the GFS and ECMWF both suggest, then the Adirondacks, Upper Hudson Valley and Greens could change to rain/snow or even all wet snow overnight. The current forecast reflects this thinking. Our system exits by Saturday morning with high pressure from the Great Lakes taking control of the region. For now, the ECMWF and GFS both favor a mostly pleasant weekend as upper level ridging increases (more so on the ECMWF than the GFS) for eastern NY and western New England with seasonable temperatures in the 50s to possible nearing 60 on Sunday. However, we will be monitoring a few shortwaves in the Central Plains which look to head eastward as we start the new work week. Lots of uncertainty in exact timing and placement but the pattern does look to turn more active so we followed suite from the previous forecast and showed chance POPs starting Sunday night through Wednesday. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... Intensifying coastal storm just off the outer banks of North Carolina will continue to track northeast. Expansive cloud shield, VFR, will persist through the overnight period. Winds will generally be around 10kts or less overnight. As this storm tracks quickly northeast, increasing pressure gradient will result with wind magnitude increases during the daylight hours Wednesday. Frequent gusts at or above 30kts are expected from the west-northwest direction. Otherwise, VFR with respect to CIGS/VIS. Outlook... Wednesday Night: Moderate Operational Impact. Windy. NO SIG WX. Thursday: Low Operational Impact. Breezy. NO SIG WX. Thursday Night: No Operational Impact. NO SIG WX. Friday: High Operational Impact. Likely RA. Friday Night: High Operational Impact. Likely SHRA...RA. Saturday: No Operational Impact. NO SIG WX. Saturday Night: No Operational Impact. NO SIG WX. Sunday: Moderate Operational Impact. Chance of SHRA. && .FIRE WEATHER... Gusty Winds and Low RH over the Next Few Days... A storm system will track off the eastern seaboard tonight and early Wednesday. Most of the precipitation with this storm will remain east of the area. A cold front will then pass through the region Wednesday afternoon bringing windy conditions into Wednesday evening. Breezy conditions will also be in place for Thursday with continued dry weather. After a dry afternoon today, the RH will recover to 70-90 percent tonight, highest across the SW Adirondacks and across western New England. RH values will lower to 20 to 30 percent on Wednesday afternoon and again on Thursday afternoon. Southerly winds will be 10 to 20 mph with some gusts up to 25 mph through this evening. Winds will become light/variable tonight through mid morning Wednesday. Winds will then become west to northwest, and rapidly increase Wednesday afternoon to 15-30 mph, with gusts of 35-55 mph. Winds will diminish somewhat after midnight Wednesday night, but some gusts up to 25 mph will continue through the day on Thursday. Some light rain or wet snow is possible tonight across portions of western New England, but amounts will be fairly negligible. Also, a few sprinkles are possible with a cold front for Wednesday afternoon, mainly impacting northern areas, but amounts will generally be only a few hundredths at most. Dry weather is then anticipated for Wednesday night through Thursday. The next chance for widespread precipitation will be Friday (as rain or a rain/snow mix) as a frontal boundary approaches from the west. && .HYDROLOGY... Other than some possible light rain/snow across western New England tonight, generally dry weather is expected through Thursday. Although daytime temperatures will be a little milder than recent days, overnight lows still looks to below freezing for much of the area for the next few nights. This should allow for a diurnal melting pattern of the snowpack that continues to be in place over the high terrain. The next chance for widespread precipitation looks to be Friday, with some rain and snow thanks to a frontal boundary. Some rises are possible due to the expected precipitation, but at this point, runoff looks limited enough to keep rivers and streams within their banks. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...Wind Advisory from 2 PM to 10 PM EDT Wednesday for NYZ032-033- 038>043-047>054-058-061-063-082>084. MA...Wind Advisory from 2 PM to 10 PM EDT Wednesday for MAZ001-025. VT...Wind Advisory from 2 PM to 10 PM EDT Wednesday for VTZ013>015. && $$ SYNOPSIS...Frugis NEAR TERM...Frugis/BGM SHORT TERM...Frugis LONG TERM...Speciale AVIATION...BGM FIRE WEATHER...Frugis HYDROLOGY...Frugis
Area Forecast Discussion
National Weather Service Grand Forks ND
1002 PM CDT Tue Apr 2 2019 .UPDATE... Issued at 1001 PM CDT Tue Apr 2 2019 Area radars show the one remaining area of showers is moving thru central ND headed for SE ND. Observations reveal mostly snow showers. This area of precipitation is moving SE and will need to adjust pops for this into SE ND. Eventually they should fall apart...but water vapor shows they be part of a weak short wave with the center in north central ND moving into NE ND. && .SHORT TERM...(This afternoon through Wednesday) Issued at 327 PM CDT Tue Apr 2 2019 Cold front has passed through our CWA, however steep low level lapse rates combined with lingering forcing aloft has supported isolated to scattered shower development. Better mid level lapse rates are shown on RAP analysis in northwest MN, where moderate to heavy pockets are quickly passing. Most snow is melting on contact, and duration is brief enough that only a dusting or 0.5" at the most would be anticipated. Stronger pressure rises and good mixing (with localized enhancement from showers) is resulting in win gusts around 40 mph and we couldn`t rule out a few gusts to 50 mph before stabilization/decoupling around sunset. These winds and more intense showers are resulting in visibilities being reduced as low as 1/4 mile for brief periods, but considering short duration only Special Weather Statement was issued. Most activity should end with loss of daytime heating. Quieter weather tonight through Wednesday as Canadian high pressure passes over our CWA. There could be a few lingering flurries through early Wednesday morning in our far northeast (Lake of the Woods county) where guidance holds onto a light precip signal. Lows will be in the upper teens/lower 20s, while highs Wed should get to the mid-upper 30s most locations (lower 40s south). .LONG TERM...(Wednesday night through Tuesday) Issued at 327 PM CDT Tue Apr 2 2019 Thursday-Sunday night: Westerly flow followed by shortwave ridging Friday, followed by deeper southwest flow late Friday into Saturday will result in increasing WAA. Overnight lows are likely to be above freezing during these periods for most of our area , especially Friday night and Saturday night. Highs will increase substantially with many locations possibly into the 50s or even 60s in the southern Red River Valley Saturday. Regarding precipitation in these periods: Shortwave trough passage Thursday-Thursday night may bring brief light precip, but most forcing splits around our CWA and there is a limited window for moisture advection. Much less confidence in system Saturday-Sunday night ands there is large spread run-run between deterministic/ensemble guidance on evolution of system. Latest runs of ECMWF and GFS have completely flipped from previous runs with ECMWF strong strong upper low causing issues in our area, while GFS will well south. Previous two runs were the complete opposite. There is still potential for instability building north Friday night-Saturday night with LLJ/WAA possibly supporting isolated thunderstorms in our south, but even then if southerly track happens showers become less likely (much less thunder). Will need to monitor as this could be a stronger system, but no confidence in if this will be a problem for us. Monday-Tuesday: Progressive pattern is depicted with consensus favoring temps above normal (highs upper 40s-50s, lows near to above freezing). Quick moving shortwaves may bring precip chances, but probably similar to events today or Thursday this week (fast and light). && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 705 PM CDT Tue Apr 2 2019 Expecting the gusty NW winds to diminish quickly early evening and be much lower thru the night into Wednesday as high pressure moves overhead. Scattered high based CU still around but less coverage after dark and into Wednesday. && .HYDROLOGY... Issued at 327 PM CDT Tue Apr 2 2019 Snow melt and runoff continue to drive a general increase in water levels for most locations along the mainstem Red River and its tributaries across the southern Red River Valley. The only exceptions to this are Wahpeton and Sabin which are seeing gradual declines in water levels. However, both of these locations are expected to remain in Moderate flood stage through much of this week. Ice jamming continues to impact the Sheyenne river, especially in the Mapleton area where an ice jam was reported just north of town. This is causing rapid water level rise into Minor flood stage and could lead to Moderate flooding if the ice jamming persists into tonight. All other river forecast points forecasts generally remain unchanged with Major flooding still expected in the Fargo area by the weekend/early next week. Ice jamming in the tributaries and in area ditches is slowing down run off for now, but with increasing temperatures forecast for the second half of the week snow melt and run off is expected to accelerate. As mentioned, the ice jamming in the smaller tributaries and ditches continues to cause areas of overland flooding in the southern Valley. Overall conditions have not changed much in the past 24 hours with the exception of parts of far southeast North Dakota where a few county roads have been impacted from minor overland flooding. These conditions will likely linger through the rest of the week before prolonged above-freezing temperatures help alleviate ice jamming/plugging and allow for better runoff. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Riddle SHORT TERM...DJR LONG TERM...DJR AVIATION...Riddle HYDROLOGY...AM
Area Forecast Discussion
National Weather Service Gray ME
1126 PM EDT Tue Apr 2 2019 .SYNOPSIS... Low pressure tracking offshore will bring some light snow and rain mainly to coastal areas tonight. This will end tomorrow with many areas warming into the 50s before a cold front blows in Wednesday afternoon. Gusty winds can be expected behind the front Wednesday afternoon. Cool temperatures can be expected Thursday and Friday with the next wave bringing some light precipitation Friday night. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 1120 PM Update...Backed off a little bit more on snow amounts late tonight based on trends in latest guidance. Otherwise no significant changes. Could be some decent windy rain/snow squalls later Wed afternoon to keep an eye on with the northern stream wave and associated cold front as well. 940 PM Update...Little change to the going forecast other than to incorporate the last 3 runs of the HRRR into the PoP/QPF forecast for later tonight through Wedensday morning. The HRRR has shown very good run to run consistency late this afternoon and evening with the western edge of precip shield basically just brushing southeastern NH and the coast of ME. Have continued with forecast of 1.5" snow or less most areas on coastal plain, with a little more (2-3") on the Midcoast. Have also sharpened up the western edge and pushed it a bit further east. Western zones should remain dry overnight. 650 PM Update...High clouds continue to filter into the region as coastal storm strengthens off the NC coast. No major forecast changes at this time. Continue to watch trends in mesoscale model guidance for any significant shifts in the western edge of precip shield later tonight and tomorrow morning. So far, the HRRR has been pretty steady run after run with solutions that closely resemble our current forecast. Not buying into the 18z 3KM NAM at this time with it`s western solution being on the western edge of the guidance envelope. Will certainly watch trends throughout the evening, however. The only change to the forecast was to tighten up the PoP/QPF gradient across interior zones late tonight and tomorrow morning as the western edge should be pretty sharp. Previously... Sfc low coming together off the coast of N Carolina this afternoon as srn steam 500 MB wave interacts with convection along stalled from in the area. This system will shift NE along the coast tonight and phase with nrn stream late tonight early Wed. This will occur too far to our S and E to avoid any major impacts, but one concern will some snow or mixed rain/snow around the morning commute. thinking is that intense snow banding will stay offshore, which will allow a warmer boundary lyr, and only occnl moderate intensity snow, to produce a mix or some short periods of snow, with mostly accums of an inch or less, which will likely not accumulate on the roads as well as grassy or snow-covered areas. Up to two inches is possible at elevations above 1000 feet, but mainly where QPF is over 0.2" which will likely limit these areas to the ME coastal plain and srn foothills as well as interior parts of srn NH. Lows range from 25-30 in the N, to the low 30s in the south. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... Wed will start off with that snow or rain, or mix, but temps will warm quickly after sunrise, so much of any precip will turn to rain by 8-9 AM or so, and will likely end during the morning as well. The second impact of this storm will be strong gust winds in the afternoon, as low pressure deepens over er the maritimes, and sfc high builds in on its helps from the west, creating strong pressure gradient from the sfc up through about 700 MB. While sustained will be closer to 20 mph, strong gusts in the 40-50 mph are possible, especially across the southern half of NH and SW ME, and a briefly lining of the sfc to mid-lvl flow will allow deep mixing. The downslope will help push afternoon temps in the 50s across a large part of the area, and this quickly melt any snow in the area. The mtns will see highs in the 40s. The winds diminish around or after sunset, but it will still be breezy Wed night with lows ranging from the low 20s in the N to around 30 near the coast. Some upslope SHSN will be possible as well. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Expect cool conditions Thursday and Friday in the post-frontal air mass with high pressure building into the area. The next wave will arrive from the southwest Friday night and will be our next chance of precipitation. It`s still unclear how much precipitation will fall with this, as this will be dependent on how much moisture can get pulled into the wave before it moves by as well as the evolution of the low level features. It could begin as some light snow for much of the northern half of the area, though temperatures will be borderline for accumulation outside the mountains. Beyond this expect high pressure to again build through the area this weekend with near normal becoming slightly above normal. Models not in great agreement on the broader pattern evolution for next week yet. General consensus is a northern stream ridge over central Canada with a southern stream trough crossing the US toward New England. The degree to which some of this trough gets cut off over the southern United States will play a big role in determining the timing of any shots of precipitation for our area. At this point, we are looking at a chance of rain Monday through Wednesday. Although it is unlikely to rain that entire time, it`s just too early to be able to narrow down when the best chances will be as there remains considerable disagreement on those finer details within the models. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... Short Term...Expect MVFR, with some tempo IFR late tonight into Wed morning in RA or SN, with improvement to VFR midday. West winds will gust to around 40 KT at times Wed afternoon, at all but KHIE. Winds subside Wed evening with VFR thru the night. Long Term...VFR expected through Friday. Rain and interior/mountain snow move in Friday night with IFR conditions likely. Clearing begins again on Saturday. && .MARINE... Short Term...Gales have been issued for Wed afternoon into Wed night as strong W flow develops behind a departing low moving thru the maritimes. Long Term...Post frontal winds continue through Thursday before finally dropping below advisory levels Thursday night. It will be relatively tranquil through the rest of the week as high pressure moves in. The frontal system arriving on Friday will briefly increase winds, but should remain below advisory levels. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Wind Advisory from noon to 7 PM EDT Wednesday for MEZ018-019- 023-024. NH...Wind Advisory from noon to 7 PM EDT Wednesday for NHZ005>015. MARINE...Gale Warning from noon to 10 PM EDT Wednesday for ANZ151-153. Gale Warning from noon Wednesday to 10 AM EDT Thursday for ANZ150-152-154. && $$ NEAR TERM...Ekster SHORT TERM...Cempa LONG TERM...Kimble
Area Forecast Discussion
National Weather Service San Francisco Bay Area
432 PM PDT Tue Apr 2 2019 .SYNOPSIS...Lingering light rain showers may persist into early Wednesday morning. Unsettled weather conditions are then likely to persist through the remainder of the week with renewed chances of rainfall likely by Thursday becoming more widespread Friday and Friday night. Temperatures are likely to remain near seasonal averages through the forecast period. && of 02:28 PM PDT Tuesday...A mix of clouds, rain showers, and sun this afternoon as a weak frontal boundary moved inland across the region. Rainfall amounts during the past 12 hours or so have ranged from trace amounts to a few hundredths of an inch for most locations while portions of the Santa Cruz Mountains reported upwards of around 0.50". Look for a few lingering showers to persist into the evening and even into early Wednesday morning. However, rain showers will again be light and not amount to much more than a few hundredths to a tenth of an inch through the night. A week ridge will shift over the region on Wednesday with a brief break in precipitation possible during the afternoon and evening hours. By Thursday, the next round of rain will begin to move in from the west as another frontal boundary approaches. A more robust frontal system is forecast to tap into a deeper plume of moisture and advect into the central California coast Friday into Saturday. This system will bring widespread rainfall to the region, first beginning in the North Bay sometime on Friday and then across the remainder of the region Friday night into Saturday. PWAT values are forecast to exceed 1.00" as the system advects inland which would potentially result in a weak atmospheric river at landfall. However, this system will move rather quickly across the region and limit overall impacts (such as flooding concerns). While the models do differ on timing and exact trajectory, the ensemble members suggest a decent rainfall event across much of the region from Friday into Saturday. Thus, look for adjustments to the forecast in the coming days. Overall, rainfall will be greatest in the North Bay with the potential for 1.00"-2.50", 1.00"-1.50" for Santa Cruz County, and 0.25"-0.75" for most other areas. Cannot rule out higher totals in some of the coastal ranges and lesser amounts in the rain shadowed valleys. Showers may linger into Saturday in wake of the exiting system. Drying conditions are then expected to develop south of San Francisco by Sunday with the potential for ongoing precipitation across the northern portion of the state into early next week. Overall, temperatures through the forecast period will remain near seasonal averages with a moist, zonal flow. && .AVIATION...As of 04:32 PM PDT Tuesday...for 00Z TAFs. MVFR cigs to prevail through much of the period with patchy IFR cigs possible overnight. The HRRR and the WRF show scattered showers in the vicinity through tomorrow afternoon, although by then shower chances will be minimal. Cigs should begin to lift back to VFR by tomorrow afternoon. SW to W winds into tonight before winds turn back out of the SE overnight. Vicinity of KSFO...MVFR cigs to continue through tomorrow morning with brief periods of borderline VFR conditions possible late this afternoon. Cigs right now between 1500-3500 ft AGL. Guidance shows MVFR cigs prevailing overnight. VFR conditions expected by tomorrow afternoon. SW to W winds becoming SE to variable tonight. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...Borderline MVFR/VFR ceilings to continue into this evening before MVFR conditions are expected to settle in overnight. W to SW winds becoming more southerly overnight. && of 02:15 PM PDT Tuesday...Light southwest to west winds overnight will become more southerly during the day on Wednesday. Winds will then gradually strengthen on Thursday and Friday ahead of the next approaching system, becoming gusty at times. A new northwest swell will arrive on Friday and build into the weekend. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...None. $$ PUBLIC FORECAST: RGass AVIATION: AS MARINE: Rowe Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Sacramento CA
312 PM PDT Tue Apr 2 2019 .SYNOPSIS... Unsettled weather this week as several weather systems impact Northern California. The late-week system will likely be the strongest with periods of heavy precipitation, gusty winds, and lower snow levels. && .DISCUSSION... A weakly negative-tilted trough is currently swinging through the region which has fostered the development of widely scattered showers. Most of these have fired within an axis of instability over the northern San Joaquin Valley eastward toward the terrain. The 21Z RAP objective analysis indicates some residual instability exists along I-5 up toward Redding. However, there have been fewer breaks in the clouds which has tempered the convective potential. Any of these cells should quickly weaken after dark given the loss of heating. Toward the Sierra, a Winter Weather Advisory remains in effect through midnight for elevations 6,500 feet and above. The S-band radar shows snow levels have generally meandered between 6,500 and 7,000 feet today. Any residual snow showers should wind down overnight. On Wednesday, while most of the region will be dry, the northern mountains can expect passing showers throughout the day. One limiting factor is the mid/upper-level ridge building across the state which should keep the activity disorganized. Gradually the focus will shift to the early Thursday system which is likely a quick hitter. Total precipitation amounts will be light across the region with highest Valley numbers near Redding where 0.25 to 0.50 inches is possible. Local terrain effects will bolster numbers to near an inch in foothill and mountain locales. Not expecting any travel concerns with 2 to 4 inches of snow in the forecast with snow levels around 6,000 to 6,500 feet. In advance of the high-end "Weak" Atmospheric River slated to push onshore Friday morning, southerly winds will really begin to pick up the prior afternoon. This is particularly the case over the northern Sacramento Valley with wind gusts potentially reaching 35 to 40 mph in the evening to overnight hours. On Friday morning, the initial bands of warm advection rainfall moves inland with activity really picking up around the early afternoon over mountain and foothill locations. Models currently advertise the heaviest snowfall from the just after noon into the overnight hours with snow levels roughly around 6,000 feet. This will likely lead to hazardous mountain travel. Snowfall amounts of 1 to 2 feet are possible during the duration of the late season winter storm. Activity should turn more showery by Saturday morning. ~BRO && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday) The weekend forecast remains up in the air given continued differences among deterministic and ensemble guidance. Run-to-run differences remain an issue for the more reliable models which diminishes confidence in the forecast. At this point, expect scattered showers on Saturday with the better focus across the interior mountain ranges. While Sunday initially appeared dry, the GFS and ECMWF vary in evolving pattern. The upper ridge shown by the 12Z GFS is stronger and forces the storm track closer to the California/Oregon border for Sunday into early next week. Meanwhile, the 12Z ECMWF depicts an offshore system strong enough to flatten the ridge supporting an increase in precipitation to conclude the weekend and into Monday. Details will likely continue to waver given the fluctuating model guidance. At this point, favored precipitation over the northern zones during this period while keeping the I-80 corridor mostly dry. ~BRO && .AVIATION... Line of showers/scattered storms with numerous cloud flashes/pulses and isolated cloud-to-ground strikes will be moving across the Nrn San Joaquin and Srn Sac Vly and into the Sierra foothills and lower mountain elevations through 00z. Widespread MVFR-IFR conditions expected along this line. Elsewhere, widespread MVFR with areas IFR, especially over mountains, through Wed morning. Freezing level near 7000-8000 ft AMSL with snow level down to around 6500 ft AMSL. Areas of Sly wind gusts up to 25 kts in the Central Vly til 03z Wed, and gusts up to 35 kts over mountains into Wed morning. && .STO WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until midnight PDT tonight for West Slope Northern Sierra Nevada. && $$