Forecast guidance continues to suggest that cold ARCTIC air gets within close proximity to CA on Feb 6th, however the latest 0Z GFS now suggests that High Pressure shunts the bulk of the frigid airmass to the east, sparing CA from the brunt of a potential HARD FREEZE. Let’s hope that this new solution sticks. We do not need more ARCTIC air visiting CA, in light of the fact that many Ag commodities are now blooming and/or sprouting much earlier this season. The ARCTIC airmass carried little moisture, so good riddance, stay away.
While the continuous, virtually non-stop rains into western Canada, the longer term outlook is trending less robust in the rainfall department each day for most of CA (except the far NW coastal region), with some minor variations, keeping the Mork rain/no rain line near Monterey Bay NE toward the Tuolumne River basin on its most southern excursion. Since this is the peak of the rainy season, this is not the best scenario outlook by the GFS.
If the dry pattern for CENCAL holds thru the end of the GFS Fantasyland Forecast realm, it will put most CA much further behind in the Drought situation (especially CEN/SOCAL!). Looking and searching for a wet pattern into the GFS Fantasyland offers little, and just when we begin to believe that there might be something big on the horizon, poof…it’s gone in the next model run…or the next day.
The suggestion by the GFS of a return of 582dm High Pressure toward the end of the Fantasyland realm is disheartening, because if verified, it would produce another very warm spell for a parched region with SJV temps depicted with mid to upper 70°’s for 3 days, which may once again break records!
Mon, Feb 3rd With the trough axis in the Great Basin and High Pressure offshore the NNW flow pattern continues with a frosty morning and then fair skies with SJV temps in the 50°’s in the north and 60°’s in the south. Moisture traveling over the dirty ridge allows some cloudiness to reach toward CA. Stronger radiational cooling allows for overnight frost at most SJV Ag Stations.
Tue, Feb 4th Morning Frost at most Ag Stations. Fair Skies. The RRR High Pressure ridge axis is positioned near 140W providing CA with a cool/dry NW flow pattern, while a moist flow aims toward the PACNW with warm rains which reach inland overnight, with partly cloudy skies over CENCAL, as temps remain close to persistence by a few degrees over CENCAL, with frost again overnight.
Wed, Feb 5th Clear skies allow for lower morning temps to provide more frost in the morning. The RRR High Pressure ridge shifts west as a REX configured High over Low pattern develops near the Dateline, with allows for cold air to descent into western Canada and the PACNW. The strong NW flow pattern over CA keeps most of the frigid-40°C ARCTIC airmass into the northern Rockies of MT, with the ARCTIC cold front stretched across WA, eastern OR into northern UT. This is dangerously close to CA! Max temps maintain into the upper 50°’s to lower 60°’s, with overnight mins slightly warmed due to increased cloud coverage.
Thu, Feb 6th While the RRR High Pressure ridge still is connected to a very large High Pressure cell over western Siberia, the Bering Sea and Western Alaska, the frigid ARCTIC airmass over the northern Rockies begins to modify and is held at bay by High Pressure over CA. While the cool/dry NW flow aloft cools somewhat, the bulk of the ARCTIC airmass is shunted eastward into the Rockies which spares CA from the detriment of the frigid temps that were previously expected. This is a new twist from the 0Z GFS and has caused a complete re-write of the forecast which was ready to go. Glad we waited until the 0Z model arrived.
Fri, Feb 7th The latest charts show the main RRR High Pressure ridge retrogrades westward to the Dateline, while an intense 510dm Low Pressure storm dives southward from Alaska into the GOA. Weak High Pressure also rebuilds offshore west of CA, with the cool/dry NW flow continuing to cross CA with subtropical moisture reaching into NORCAL and portions of CENCAL. The southern extent of rainfall lays somewhere over the northern SJV.
Sat, Feb 8th The large GOA storm system covers most of the GOA with the south flank of the trough continuing to drag a long-fetched Atmospheric River (AR) into the PACNW and the far NW portion of NORCAL with heavy rains. Partly cloudy skies reach into CENCAL. The frontal boundary stalls over NW CA overnight producing heavy accumulations of rainfall.
Sun, Feb 9th The trailing end of the AR continues to flow into NORCAL and gradually tapers off, while CENCAL remains dry with partly cloudy skies.
Days 8-16, Long Range into Fantasyland Outlook; Day 8 begins;
Mon, Feb 10th shows the RRR High Pressure offshore CA, with a longwave trough extending from western Canada SW toward Hawaii carrying an intensifying Atmospheric River (AR) with heavy precip into Vancouver and the WA coast. The NW flow pattern over CA brings occasional clouds.
Tue, Feb 11th shows intense heavy rains pounding the SW Canada Coast and the PACNW with torrential rains supplies by the rich PWAT AR moisture originating from Hawaii. Partly cloudy skies reach into NORCAL.
Wed, Feb 12th shows little change in the synoptic pattern with a long-fetched SW flow reaching the Dateline extending into SW Canada and the PACNW and NORCAL down to the north Bay, SAC and Tahoe, with partly cloudy skies for CENCAL. Overnight the RRR High Pressure ridge rebuilds offshore and over CA with 576dm heights over SOCAL, as a weak frontal boundary passes thru CENCAL with a few possible showers.
Thu, Feb 13th shows rebuilding High Pressure offshore west of CA, with the storm track shifting northward into the Alaskan panhandle…still connected to the long-fetched AR originating from near Hawaii. The GOA Low Pressure shifts closer to the Aleutians. Overnight as skies clear over the WCONUS, the High Pressure ridge axis moves onshore.
Fri, Feb 14th Valentine’s Day shows the RRR High Pressure ridge with 576dm heights dominates CA and the West Coast, with the storm track continuing the non-stop heavy rains into the western Canadian coastline which occasionally brush the Olympic peninsula.
Sat, Feb 15th shows a dramatic increase in the RRR High Pressure ridge with a warm 582dm circulation forming over CEN/SOCAL, with rapidly increasing temps for the region, while the AR flowing into Western Canada weakens.
Sun, Feb 16th shows increased amplification of the upper level Rossby waves, as the RRR High Pressure ridge with 582dm heights remains over CEN/SOCAL producing a heat wave and the northern extension pushes northward into the Yukon. The Hudson Bay Low Pressure intensifies, and now we have a pattern that appears very similar to most of January!
Mon, Feb 17th shows slight weakening of the WCONUS RRR High Pressure ridge as a shortwave trough approaches 140W as winds aloft over CA veer to the SW. Moisture begins to flow into the Olympic region from the trough pattern, while CA remains warm and dry.
Tue, Feb 18th shows the High Pressure ridge shifting inland into the Great Basin with the weak trough moving onshore into the PACNW and NORCAL, with some moderate rains reaching as far south as Cape Mendocino and partly cloudy skies extend throughout most of NORCAL. CENCAL remains, warm/dry.
Wed, Feb 19th shows flow High Pressure and a westerly zonal-type flow pattern over the PACNW carrying occasional surges of moisture inland, brushing portions of far NW CA while CENCAL remains fair/warm and dry.
Station New Record Old Record__
Campo 20° 22° set in 1975
Day 1 – 5 QPF:
At 12Z (9am) Monday thru the period Friday night (Saturday @4am) shows;
Mon shows a few lingering showers possible along the far NW coastal region as well as into the SW coastal region with <0.1 inch.
Tue shows a dramatic drying trend, with much less spotty rainfall over CA, with a few sprinkles over the SOCAL higher terrain.
Wed shows increased shower activity centered around the Bay region with up to 0.2 inch, and with >0.1 inch from SLO to Merced to the San Joaquin, Merced, Tuolumne, Stanislaus River basins westward across SAC to near Clear Lake.
Thu shows a concentration of precip along the Central Coast region with up to 0.5 inch into the San Lucia’s and also into the higher terrain of SOCAL. With up to 0.2 inch for the Sierra from the northern San Joaquin River basin northward to the Feather River basin, and >0.1 inch from Mendocino Co to Alturas southward thru the Great Valley from near Colusa southward thru the SJV and Southern Sierra into the coastal region of SOCAL.
Fri shows only a few sprinkles/showers >0.1 inch over the Sierra from Tahoe to Isabella, and into some of the higher terrain of SW CA, otherwise most of CA is DRY!
5DAY ACCUMULATION CHART:
Days 6 & 7 QPF thru next Sat/Sun shows heavy precip for portions of NORCAL with up to 4+ inches for the NW coastal region, up to 2 inches for the northern Sierra, up to 1 inch for the Bay region with diminishing amts to the south, with most of CENCAL with 0.25 inch or less. No rain south of Modesto to the San Joaquin River basin.
16-Day QPF estimates (from the 12Z GFS) for;
Days 1-8 shows heavy rains forecast for the NW Coastal region with a target focal point of 4.6 inches for Eureka, with rapidly diminishing amts to the south and east, with most of the SJV and SOCAL remaining DRY.
Days 9-16 shows light to moderate rainfall over portions of NORCAL down to the North Bay to Blue Cyn, with up to 0.5 inch for the far NW Coastal region and down to 0.1 inch for the Bay region to Tahoe, and most of CENCAL south of Gilroy to Modesto staying DRY into all of SOCAL being abundantly DRY.
Monday’s 12Z 9am GFS 384hr, 16Day QPF Chart, showing up to 3 inches for the far NW Coastal region of Del Norte Co, with rapidly diminishing amts to the south, with the primary rain/no rain cut-off near the Monterey Bay region eastward into the Tuolumne River basin. SOCAL remains mostly DRY
Monday’s 0Z 9pm GFS 384hr, 16Day QPF Chart, showing slightly higher QPF’s for NORCAL as compared to the morning 12Z model, with up to 4-5 inches suggested for the NW Coastal region, with rapidly diminishing amt to the south with the primary Mork rain no/rain cut-off line remaining nearly in the same position over the Monterey Bay region to the Tuolumne River basin very similar to the morning 12Z model. SOCAL remains the same as the morning model, with mostly DRY conditions.
Water Vapor 4KM Image of the West Coast Monday, February 3rd, 2014, shows yesterday’s storm system moving into NM with the outline of High Pressure offshore west of CA appearing. Dry air on a NW flow pattern is advecting into CA.
Visible Satellite Image of the CA Monday, February 3rd, 2014, shows most of the Great Valley is clear except in the South Valley region and along the Eastside foothills with some cumulus buildup. The Sierra/Tehachapi are shrouded in cloudiness. The NW flow pattern has disrupted the offshore stratus deck.
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Atmospherics Group International
Dan Gudgel Steve Johnson