January 22, 2024: Strong Pacific Storm to Impact Arizona Tonight into Wednesday Morning (Part 1)

 Synopsis

This is the first part of a forecast discussion regarding a strong Pacific Storm expected to impact Arizona starting this evening and persisting into Wednesday morning. The first round of moderate to heavy rain is expected to begin this evening and persist into the early morning hours tomorrow. Snow levels will remain above 7000 feet with this storm.


 Current Conditions

Regional visible satellite imagery overlaid with GOES GLM flashes indicates a band of heavy showers moving through far Southern California with a few sporadic lightning strikes just off the coast of San Diego this morning. 


Visible satellite imagery overlaid with GLM flashes courtesy of College of Dupage.


Current SPC 300mb analysis displays a strong jet streak just off the SoCal coast with a region of upper level divergence over far Southern California associated with the left exit region dynamics.

SPC 300mb analysis as of 18:00z.


Current SPC 500mb analysis shows a shortwave trough just off the SoCal coast with a region of PVA (Positive Vorticity Advection) over far Southern California. 


SPC 500mb analysis as of 18:00z.


The 12z NKX (San Diego) observed sounding displayed an impressive veering wind profile with over 200 m^2/s^2 of 0-3km SRH and 56 kts of shear between the surface and 8 km. Thermodynamics were marginal at best with only around an inch of pwat and 150 J/kg of CAPE.


12z NKX sounding courtesy of the SPC.


Meanwhile, partly to mostly cloudy skies across Arizona with some light rain beginning to fall over the lower Colorado River Valley. Clouds and precipitation are expected to increase from west to east throughout the late afternoon into the evening hours across the state.




 Tonight through Tomorrow Morning


Synoptics

Throughout the day today the aforementioned shortwave trough and upper level jet streak off the coast of SoCal will amplify and move east into Arizona. As this occurs, Arizona will be under the influence of PVA and upper level divergence due to left exit region dynamics. 

12z GFS 500mb vorticity for tonight at 11PM MST.


12z GFS 300mb winds for tonight at 11PM MST.

Synoptic scale ascent combined with modest moisture from the Pacific will lead to increasing precipitation chances throughout this evening into tomorrow morning.



What to Expect/Potential Impacts


The first round of precipitation is expected to impact Phoenix and Tucson just after sunset this evening and persisting into the early morning hours tomorrow. All members of our U AZ WRF are in good agreement regarding the timing and intensity but will be showing the 12z WRF-HRRR for this discussion.


12z WRF-HRRR simulated reflectivity at 7:00 PM MST tonight.




Model soundings for both Phoenix and Tucson indicating impressive veering wind profiles and nearly saturated low to mid level thermodynamic profiles by this evening. Meaning that strong synoptic scale ascent will have no problem wringing out the atmosphere of the available water vapor. 


12z KPHX WRF-HRRR sounding for this evening at 5:00 PM MST


12z KTUS WRF-HRRR sounding for this evening at 5:00 PM MST


This first round of precipitation will be primarily stratiform in nature so not expecting much in the way of convection. However, with plenty of synoptic scale ascent a few rogue lightning flashes within some of the heavier rain bands is possible. Rainfall rates will increase throughout the nighttime hours into the early morning hours with CAM solutions suggesting the heaviest precipitation prior to sunrise tomorrow morning. Current CAM solutions also suggest the most intense activity will remain mainly confined to Southeastern AZ (from Tucson southward). 


12z WRF-HRRR simulated reflectivity for tomorrow at 2:00 AM MST.





12z WRF-HRRR simulated reflectivity for tomorrow at 4:00 AM MST.



As mentioned above, rainfall rates will be mainly moderate with a few bands of heavier precipitation. Current guidance suggests precipitation amounts between 12z this morning and 12z tomorrow morning will be around an inch or more in Southeastern AZ and between 0.5 and 1 inch in Central and Western AZ. 




12z WRF-HRRR 24-hour QPF from 12z today to 12z tomorrow.



Considering that we just had a nice soaker yesterday evening, the ground is quite saturated so localized flooding is definitely a concern. Travel conditions will be hazardous particularly along I10 and I8. Snow levels will remain above 7000ft with heavy snow expected. 


12z WRF-HRRR 24 hour snowfall forecast from 12z this morning to 12z tomorrow.


Will provide more information regarding the forecast for tomorrow and Wednesday morning later this evening so stay tuned.









Comments

Post a Comment

Popular posts from this blog

February 1st, 2024: Starting February with a Potent Pacific Storm

Image
  Synopsis A pacific storm is expected to impact Arizona beginning this evening and persisting into tomorrow morning with post frontal convective showers expected tomorrow afternoon and evening. Total precipitation is expected to range between 0.50 and 1.00 inch in the lower deserts and between 1 and 3 inches over the higher terrain especially along southwestern/south facing slopes of the mountains. Snow levels will remain quite high with freezing levels starting around 8000 ft this evening a dropping to around 5000 ft tomorrow afternoon. The heaviest snowfall is expected mainly over the highest mountain peaks of the Mogollon Rim, White Mountains, and Sky Islands of Southeastern AZ with upwards of 1 to 2 feet of accumulated snowfall.  Current Conditions  At 9:00AM MST, IR satellite imagery displayed an atmospheric river impacting Southern California.  GOES-16 IR satellite imagery courtesy of College of Dupage. El Niño is in full swing as indicated by w...
Read more

April 4th, 2024: Windy, Cold, and Light Precipitation Tomorrow

Image
Synopsis A deep mid latitude trough will impact AZ beginning tomorrow and into early Saturday morning providing the region with gusty winds, cold temperatures, and a chance for precipitation. This system will be relatively moisture starved so mainly light precipitation is expected with the primary focus being strong winds and anomalously cold temperatures especially for this time of year. The majority of precipitation will occur over the higher terrain, but some very light rainfall accumulations are possible across the valleys. Rainfall amounts will range from a trace to 0.10 inch in the valleys and between 0.10 and 0.50 inch of SWE over the higher terrain favoring southwestern facing slopes of the mountains. Snow levels will remain above 4000 feet with between a trace to 6 inches expected and locally higher amounts possible over the highest peaks of the Mogollon Rim and White Mountains. Current Conditions At 10:54AM MST, visible satellite imagery displayed a mid latitude cycl...
Read more

February 5th, 2024: Another Pacific Storm to Impact Arizona Tomorrow and Wednesday

Image
  Synopsis Another Pacific Storm is expected to affect Arizona starting tomorrow and persisting into Wednesday evening. The main rain band/Atmospheric River will impact Western AZ late tomorrow morning and afternoon  then Eastern AZ late tomorrow afternoon into Wednesday morning. Scattered Post-frontal convective showers and isolated low-topped thunderstorms can be expected Wednesday morning and early afternoon as well. Current QPF is between 0.10 and 0.50 across the lower deserts and 1 to 3 inches over the higher terrain with highest amounts along the southwestern facing slopes of the Mogollon Rim, White Mountains, and Sky Islands of SE AZ. Snow levels will remain quite high with the initial rain band/AR with freezing levels above 9000 feet and dropping to around 6000 feet by Wednesday. Snow totals of 6 to 12 inches are expected for the highest mountain peaks above 9000 feet with less than 6 inches for mountains between 5000 and 9000 feet.    Current Conditions...
Read more