High Pressure dominates with dry conditions and above average temps into Monday, with Tuesday a day of transition. By Wednesday temps could drop by as much as -15° to -20° with showers and/or Thunderstorms. Long range into the Fantasyland realm shows several juicy storm systems targeted for NORCAL, which if verified…could put a small dent into the Drought situation for the important NORCAL reservoirs.
The GFS has flipped into an active mode during the 16 Day period, especially with regards to NORCAL, with impressively high 7-8 inch QPF’s suggested during the 16 Day period. Let us hope that the forecasted high QPF DO VERIFY!!! This storm period could make at least a small dent into the horrific Drought conditions plaguing the important NORCAL reservoirs. The main message for this period is for a return to a zonal-type moist flow pattern with mild, wet wx from coast to coast and the wettest region from SFO to Tahoe receiving significant rains. This could be one of the best storm periods of the Water Year for NORCAL, especially if the suggested cold front stalls out over that region. With so much storm activity during the 16 Day time frame, there is little time between systems to allow for frost, but if clear skies are present and winds are calm there are two opportunities for morning frost into the SJV; 1) on the morning of April 1, and 2) on the morning of April 4th. These potential threats are minimal and most likely transient with a low confidence vote…with minimums at the coldest Ag Stations suggested at 32°. With an active pattern that illustrates several cold core storms to traverse thru CA during the 16 Day period, the most worrisome system is at the end of the Fantasyland Forecast realm…as it is depicted as being extremely cold. We’ll take a close look at the potential for Thunderstorms for Wednesday, during the next scheduled 16 Day forecast on Tuesday night. Thus far at the moment, it’s not very impressive for the SJV, but a closer look is warranted Tuesday. Thunder for NORCAL on Wednesday appears likely.
EL NINO MEDIA HYPE; Please resist the temptation to fall for the media HYPE regarding the forecasted EL NINO development. The next several months are likely to see a deluge of media HYPE regarding the possible/probable development of a warm phase ENSO. While we all hope that next year is a wet Water Year, there is currently no scientific basis at this time from any source that is reliable or credible …that next year will be a flood year or close to it. Here are the facts; there is a 50% chance of El Nino forming by this fall according to reliable and credible sources, however…its strength is highly uncertain. Whether it will be a weak, moderate or possibly strong event is completely unknown at this time by ANYONE! It will not be until September or October at the earliest to determine how the different PAC basin oscillations (including ENSO) will interact. To rely wholly upon a prediction for a warm phase ENSO to base a forecast for next Water Year is completely unwarranted and irresponsible.
Precip Totals past 24hrs include; none
Winter Storm Watch; posted for the Northern Sierra from Tue thru Thu for periods of heavy snowfall of up to 7 to 14 inches above 4.5K and 1 to 2 feet above 6K, accompanied by strong winds of 45mph or higher. This will impact the Sierra from Lassen southward to Donner (I-80), Echo (Hwy 50) and Carson passes.
Hazardous Wx; Thunderstorms possible Wed, Mar 26th for the SJV, Fresno Co northward.
Mon, Mar 24th The main features in the EPAC show a large 534dm Low Pressure storm center in the GOA with an associated trough extending southward which is approaching the West Coast. High Pressure over the West Coast begins to shift eastward into the Great Basin with increasing SW flow aloft over NORCAL. Overnight as the High Pressure ridge continues to migrate eastward the GOA Low Pressure storm pivots NE with the trailing cold front moving into the NORCAL coastline oriented north to south with heavy rains progged by charts for the northern coastal region, with diminishing amts of moisture and dynamic lift south of the North Bay region. While the diminishing frontal boundary reaches into NORCAL, the main trough axis remains offshore producing an increasing cyclonic flow pattern producing a SW flow over CA.
Tue, Mar 25th Confidence regarding this storm event is quite high, as it has been on charts for the past 12Days! However, the QPF’s projected for CENCAL still remain somewhat in question. As the offshore trough pivots NE dynamic lift moves onshore along the CA coastline from the Bay region northward with rainshowers gradually weakening and pulling northward. Cyclonic flow into the West Coast following the cold front brings an additional surge of moisture inland over NORCAL from SFO to Tahoe overnight. The trough axis with additional rainshowers overnight into CENCAL from Tahoe to Kings Canyon and up to 0.2 inch for the SJV north of Fresno.
Wed, Mar 26th A quasi-zonal flow pattern behind the passage of the trough axis continues a moist onshore flow into NORCAL with continued heavy rains ove portions of NORCAL and with diminishing amts over CENCAL. Charts indicate possible Thunderstorms over NOR/CENCAL down to Fresno Co during the afternoon. Then with clearing skies over CENCAL as weak High Pressure moves onshore overnight, however a moist flow continues to bring occasional rainshowers into NORCAL. A secondary cold trough digs southward from the GOA overnight.
Thu, Mar 27th As the new cold trough approaches the PACNW coast, heavy rains spread inland over WA/OR with lighter rainfall reaching into NORCAL. The moist onshore westerly flow pattern continues to bring rainshowers into far NORCAL, from Cape Mendocino eastward into the Northern Sierra, while CENCAL remains partly cloudy and SOCAL stays fair. Overnight the rapidly developing cold front sags southward with heavy rains over NORCAL from Santa Rosa to Tahoe, with partly cloudy skies over most of CENCAL and fair skies over SOCAL. Overnight the cold front stalls over NORCAL.
Fri, Mar 28th The frontal boundary over the NORCAL remains stalled out, with heavy non-stop rains from Vancouver, BC southward to the North Bay region and into the northern Sierra, with showers reaching as far south as Monterey to YNP, and with partly cloudy skies reaching into CENCAL. Overnight the stalled frontal boundary begins to diminish in intensify as the trailing end to the front weakens to the west over the Bay region. Partly cloudy skies maintain over the northern portion of CENCAL while the main trough axis lags behind, further west of the CA coast.
Sat, Mar 29th The remnants of the stalled cold front continue to bring heavy rainfall into a line from SFO into the Tahoe region along a narrowing band of precip. Although the frontal boundary is narrow it does contain a long-fetched Atmospheric River (AR) attachment which originates in the Hawaiian Island region. The far NW portion of CA begins to clear, while clouds increase over CENCAL and fair skies prevail over SOCAL. The trough axis remains stationary off the West Coast with a strong SW flow aloft over CA, which should produce excellent orographic lift for the Sierra. Overnight the stalled frontal boundary remains in place over the Bay region to Tahoe, while the southern portion of the trough begins to swing eastward.
Sun, Mar 30th As the primary trough axis moves closer to the coast the stalled out frontal boundary re-aligns more SW to NE with heavy precip continuing over most of NORCAL, especially near the front which is near the Bay region to Tahoe. Partly cloudy skies increase over CENCAL with showers into the northern SJV. Overnight the stalled frontal boundary finally kicks SE thru CENCAL and into SOCAL with a narrow but strong frontal passage. The main trough axis however, lags behind.
Days 8-16, Long Range into Fantasyland Outlook; Day 8 begins;
Mon, Mar 31st shows the broad trough axis moving thru the West Coast with additional rainshower activity over much of CA with gradual clearing initiating overnight with diminishing showers as High Pressure offshore produces a cool/dry NW flow pattern.
Tue, Apr 1st shows High Pressure moving onshore over the West Coast with another -30°C cold core Low Pressure traveling thru the GOA toward the PACNW region. Overnight as the storm approaches the PACNW, rains reach the WA/OR coast.
Wed, Apr 2nd shows a large -30°C cold core Low Pressure center west of the Columbia River with High Pressure over the Great Basin producing a SW flow aloft over CA while rains continue to spread inland over the PACNW and into NORCAL. Overnight the trough axis approaches the CA coast with a limited amt of moisture moving onshore according to the GFS charts.
Thu, Apr 3rd shows the trough axis moving thru CA with moderate rains spreading across NORCAL down to SFO/Monterey to near YNP with partly cloudy skies southward to Kern Co. Overnight the trough kicks east and is replaced by flat High Pressure with a continuance of Low Pressure remaining over the GOA with another disturbance rotating thru the trough toward the PACNW region.
Fri, Apr 4th shows temporary High Pressure builds over CA, with a new cold trough digging southward at 140W with a SW flow aloft once again forming over NORCAL. While the High Pressure steepens, it also moves eastward into the Great Basin with the approaching trough bringing renewed rains into the PACNW down to central OR.
Sat, Apr 5th shows the High Pressure ridge migrates into the Rockies, while the large trough approaches the West Coast with increasing SW flow aloft and rains approaching the NORCAL coast. Overnight rains spread throughout the PACNW, down to Cape Mendocino, with southerly winds aloft over CEN/SOCAL.
Sun, Apr 6th shows as the main Low Pressure remains into the GOA, the trough axis pivots NE into CA, losing a lot of dynamic strength which is pulled northward into the PACNW which rapidly reduces the strength of the cold front that is moving into NORCAL. Light rains spread southward along the coast to near San Simeon. A secondary disturbance is organizing further west of NORCAL along 40N. Overnight the second disturbance ramps up its moisture field well ahead of the main cold front as it approaches NORCAL.
Mon, Apr 7th shows -34°C cold core Low Pressure storm rapidly approaching the OR coastline. This is a very powerful late winter storm accompanied with dynamic strength and a rapidly intensifying cold front which brings heavy rains into the West Coast as far south as Pt Arena, inland across portions of NORCAL. Overnight the cold core moves toward the Olympic Peninsula with the trailing cold front passing thru NORCAL and into portions of CENCAL then out to sea near San Simeon.
Tue, Apr 8th shows the main trough axis moving thru the West Coast with the parent -34°C cold core near the Olympic Peninsula while the trough moves onshore over CA with the -30°C isotherm passing thru Cape Mendocino. This appears as a very sharp trough axis which is reaching into CA at the end of the GFS Fantasyland Forecast realm. Although the moisture field associated with this system does not appear that impressive, it does indicated the strong possibility of producing Thunderstorms for the SJV. If this disturbance does indeed verify, then the very cold air following it should be carefully monitored for possible morning frost.
Station New Record Old Record__
Los Angeles 58° (Ties) 58° set in 1986, 1978 and 1959 High Min
Burbank 54° (Ties) 54° set in 1996 and 1940 High Min
San Diego 61° 60° set in 1993 High Min
Day 1 – 5 QPF:
At 12Z (9am) Sunday thru the period Thursday night (Friday @4am); showing as much as 3 to 4 inches of precip for the wet spots of the NW coastal region and 1-2 inch for the northern and central Sierra and 0.5 to 1 inch for the Southern Sierra.
7 Day QPF Chart; showing up to 7-8 inches of rainfall into the far NW coastal region near the OR border, with a focal point of 9.6 inches showing near Brookings, OR. Amts over NORCAL diminish up to 4-5 inches of precip from Ft Bragg northward along the North Coast and up to 3-4 inches from Mendocino Co northward along the coast and into the Shasta River basin region and into the wet spots of the Feather River basin with up to 2 inches from near the Russian River basin northward along the coast thru the Shasta River basin, then southward into the Sierra to near YNP, with up to 1 inch from near the Bay region NE into the SAC Valley and then southward into the Southern Sierra to the Kaweah River basin, with up to 0.5 inch for the Delta region and up to 0.25 inch for the SJV and the coastal regions of SOCAL.
16-Day QPF estimates (from the 0Z GFS model) for;
Days 1-7; shows up to 7-8 inches of rainfall into the far NW coastal region near the OR border, with a focal point of 9.6 inches showing near Brookings, OR. Amts over NORCAL diminish up to 4-5 inches of precip from Ft Bragg northward along the North Coast and up to 3-4 inches from Mendocino Co northward along the coast and into the Shasta River basin region and into the wet spots of the Feather River basin with up to 2 inches from near the Russian River basin northward along the coast thru the Shasta River basin, then southward into the Sierra to near YNP, with up to 1 inch from near the Bay region NE into the SAC Valley and then southward into the Southern Sierra to the Kaweah River basin, with up to 0.5 inch for the Delta region and up to0.25 inch for the SJV and the coastal regions of SOCAL.
Days 8-16; shows up to 1 inch for the NW Coastal region and the Shasta and Feather River basin, diminishing to 0.5 inch for the North Bay to Tahoe line, and 0.25 inch from Monterey to Kings Canyon and >0.1 inch for Kern Co into SOCAL.
GFS 384hr, 16Day QPF Chart, depicting up to 5-10 inches of precip for a large section of the West Coast from NORCAL into BC, Canada, with up to 8 inches for the NW CA coastal region, and with up to 7 to 8 inches depicted for the northern Sierra into the Feather, Yuba and American River basins, with up to 7 inches for the Russian River basin. Amts rapidly diminish down to 2 inches from Monterey eastward to YNP. A sharp demarcation line exists over CENCAL with sharply reduced precip amts in the southern portion of the SJV.
Weekly Evapotranspiration rates for the local 7 Counties shows up to 0.94 to 1.24 inches of evaporation for the SJV during the next 7 Days. The Sierra Crest loss is 0.63 inch up to 0.74 inch.
Water Vapor 4KM Image of the West Coast Sunday, March 23rd, 2014, shows High Pressure over CA with a minor weak disturbance offshore of the Central Coast which is providing enough instability for convection to erupt into the Southern Sierra while pulling some high cloudiness over portions of SOCAL. Dry air as depicted by the orange shading covers most of NOR/CENCAL.
Visible Satellite Image of the CA Sunday, March 23rd, 2014, shows some convective buildups along the Southern Sierra Crest region with a few spotty showers in the High Country, but most of the associated precip did not reach the ground as verified by Doppler Radar. A few high clouds are crossing SOCAL, while the remainder of CA is abundantly clear.
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Comments and suggestions always welcome.
Atmospherics Group International
Dan Gudgel Steve Johnson