Weather Products for Phoenix Air Quality Forecast Wednesday, April 9, 2004

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NGM MOS Numerical Model PHX SCW NGM MOS GUIDANCE 4/09/ UTC DAY /APR 9 /APR 10 /APR 11 / Fri Sat Sun Fri Sat Sun HOUR MN/MX TEMP DEWPT CLDS BK BK BK SC SC SC SC SC CL CL CL CL CL CL CL CL CL CL CL WDIR WSPD POP POP QPF 0/ 0/ 0/0 0/ 0/0 0/ 0/0 0/ 0/0 TSV06 20/ 0 16/ 2 6/ 0 3/ 0 7/14 4/ 4 5/ 6 2/ 0 3/21 TSV12 28/ 0 8/ 0 10/17 6/ 4 PTYPE R R R R R R R R R R R R R R R POZP POSN SNOW 0/ 0/ 0/0 0/ 0/0 0/ 0/0 0/ 0/0 CIG VIS OBVIS N N N N N N N N N N N N N

GFS Numerical Model KPHX GFSX MOS GUIDANCE 4/09/ UTC FHR 24| 36 48| 60 72| 84 96| | | | FRI 09| SAT 10| SUN 11| MON 12| TUE 13| WED 14| THU 15| FRI 16 CLIMO X/N 84| 62 82| 59 83| 57 88| 62 92| 64 91| 63 87| TMP 81| 64 79| 61 81| 58 87| 64 90| 66 89| 64 84| DPT 40| 45 33| 32 21| 32 21| 31 26| 34 28| 35 28| CLD OV| PC PC| CL CL| CL CL| CL CL| CL CL| CL CL| CL PC WND 10| 12 16| 16 9| 10 10| 9 10| 9 11| 10 11| P12 16| 10 9| 9 1| 1 1| 1 2| 2 1| 2 3| P24 | 19| 10| 1| 2| 4| 3| 14 7 Q12 0| 0 0| 0 0| 0 0| 0 0| 0 0| 0 | Q24 | 0| 0| 0| 0| 0| | T12 9| 11 11| 3 1| 1 0| 0 0| 1 4| 2 1| 3 1 T24 | 17 | 11 | 1 | 0 | 2 | 5 | 3 Warming up!

National Weather Service Dicussion Phoenix, Arizona FXUS65 KPSR FXUS65 KPSR AFDPSR AFDPSR AZZ020>028-CAZ030> AZZ020>028-CAZ030> AREA FORECAST DISCUSSION AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ NATIONAL WEATHER SERVICE PHOENIX AZ 430 AM MST TUE APR AM MST TUE APR SOUTHWEST AND SOUTH-CENTRAL ARIZONA...AND SOUTHEAST CALIFORNIA SOUTHWEST AND SOUTH-CENTRAL ARIZONA...AND SOUTHEAST CALIFORNIA FORECAST DISCUSSION FORECAST DISCUSSION.SYNOPSIS... A COUPLE OF WEAK LOW PRESSURE SYSTEMS FROM THE NORTHWEST AND NORTH WILL MOVE OVER THE AREA TODAY AND SATURDAY. THE SYSTEM SATURDAY WILL BE SOMEWHAT STRONGER...BUT MUCH DRIER AIR WILL BE MOVING INTO SOUTHEAST CALIFORNIA AND FAR WESTERN ARIZONA BY THAT TIME. THERE WILL BE A THREAT OF THUNDERSTORMS OVER SOUTH- CENTRAL ARIZONA SATURDAY. AS FOR THIS SYSTEM TODAY...THE AIRMASS REMAINS MOIST AND UNSTABLE OVER THE ENTIRE REGION...BUT THIS SYSTEM IS QUITE WEAK. THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS MAINLY OVER SOUTH-CENTRAL ARIZONA TODAY AND TONIGHT. DRIER AIR WILL BE RULE SUNDAY AND INTO THE MIDDLE OF NEXT WEAK WITH HIGH PRESSURE ALOFT. HOWEVER...AT LEAST INCREASING CLOUDS MAY OCCUR LATER IN THE WEEK WITH ANOTHER PACIFIC WEATHER SYSTEM PUSHING INTO THE SOUTHWEST. &&.DISCUSSION... LIGHT DISSIPATING SHOWERS OR PERHAPS JUST VIRGA SHOWING UP OVER RIVERSIDE COUNTY EASTWARD ACROSS NORTHERN LA PAZ COUNTY AND NORTHWEST MARICOPA COUNTY THIS MORNING. HAVE ADDED SOME SINGLE DIGIT POPS FOR THOSE AREAS ON THE GRIDS...BUT NOT HIGH ENOUGH TO WARRANT THE MENTION OF SHOWERS OR THUNDERSTORMS. EARLIER DURING THE.SYNOPSIS... A COUPLE OF WEAK LOW PRESSURE SYSTEMS FROM THE NORTHWEST AND NORTH WILL MOVE OVER THE AREA TODAY AND SATURDAY. THE SYSTEM SATURDAY WILL BE SOMEWHAT STRONGER...BUT MUCH DRIER AIR WILL BE MOVING INTO SOUTHEAST CALIFORNIA AND FAR WESTERN ARIZONA BY THAT TIME. THERE WILL BE A THREAT OF THUNDERSTORMS OVER SOUTH- CENTRAL ARIZONA SATURDAY. AS FOR THIS SYSTEM TODAY...THE AIRMASS REMAINS MOIST AND UNSTABLE OVER THE ENTIRE REGION...BUT THIS SYSTEM IS QUITE WEAK. THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS MAINLY OVER SOUTH-CENTRAL ARIZONA TODAY AND TONIGHT. DRIER AIR WILL BE RULE SUNDAY AND INTO THE MIDDLE OF NEXT WEAK WITH HIGH PRESSURE ALOFT. HOWEVER...AT LEAST INCREASING CLOUDS MAY OCCUR LATER IN THE WEEK WITH ANOTHER PACIFIC WEATHER SYSTEM PUSHING INTO THE SOUTHWEST. &&.DISCUSSION... LIGHT DISSIPATING SHOWERS OR PERHAPS JUST VIRGA SHOWING UP OVER RIVERSIDE COUNTY EASTWARD ACROSS NORTHERN LA PAZ COUNTY AND NORTHWEST MARICOPA COUNTY THIS MORNING. HAVE ADDED SOME SINGLE DIGIT POPS FOR THOSE AREAS ON THE GRIDS...BUT NOT HIGH ENOUGH TO WARRANT THE MENTION OF SHOWERS OR THUNDERSTORMS. EARLIER DURING THE …Continued

…Continued NIGHT...THERE WERE SOME THUNDERSTORMS ASSOCIATED WITH THE WEAK TROUGH IN NORTHWEST ARIZONA...THAT IS CAUSING THE FEW LIGHT SHOWERS OR VIRGA PRESENTLY IN THE AREAS MENTIONED ABOVE. THE ETA AND NGM MODELS DO SUPPORT SOME INSTABILITY MOVING INTO SOUTH-CENTRAL ARIZONA THIS AFTERNOON. THE QUESTION REMAINS HOW FAR WEST TO INCLUDE THIS WEATHER FOR THE REMAINDER OF TODAY. AS OF NOW...ONLY MENTION OF SHOWERS AND THUNDERSTORMS IS OVER EASTERN MARICOPA COUNTY EASTWARD ACROSS SOUTHERN GILA AND NORTHWEST PINAL. MAY HAVE TO UPDATE TO INCLUDE AT LEAST ZONES 22 AND 27...BUT WILL WAIT FOR AWHILE. MEANWHILE...A SOMEWHAT STRONGER SYSTEM IS FORECAST TO AFFECT THE AREA LATER TONIGHT AND SATURDAY. BOTH THE 12Z ETA AND NGM ARE A LITTLE FURTHER TO THE SOUTHWEST WITH THIS SYSTEM THAN THE PREVIOUS RUN...WITH THE NGM BEING FURTHER TO THE SOUTHWEST THAN THE ETA. THERE ARE MORE DYNAMICS WITH THIS SECOND SYSTEM ON SATURDAY...MAINLY OVER THE EAST PORTION OF OUR CWA. HOWEVER...MUCH DRIER AIR IS BEING ADVECTED OVER SOUTHEAST CALIFORNIA AND FAR WESTERN ARIZONA DURING THIS TIME...SO WILL LIMIT ANY MENTION OF THUNDERSTORMS TO OUR EASTERN CWA FOR SATURDAY. LATEST ETA AND NGM MOS DO SUGGEST SOME INCREASE IN WINDS BOTH SATURDAY AND SUNDAY...AND THESE WINDS MAY HAVE TO BE INCREASED SOME ON THE GRIDS FOR THOSE PERIODS. MORE BENIGN WEATHER IS SLATED FOR SUNDAY INTO THE MIDDLE OF NEXT WEEK WITH HIGH PRESSURE ALOFT. DURING THE LATTER PART OF THE WEEK...THE LATEST EXTENDED GFS BRINGS IN A TROUGH THAT IS DEEPER AND STRONGER THAN PREVIOUS RUNS. THE MID SHIFT HAS WISELY DECIDED NOT TO CHANGE MUCH IN THE EXTENDED EXCEPT TO ADD MORE CLOUDS...SINCE THIS IS ONLY FIRST RUN SHOWING THIS TROUGH..PSR...WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. NIGHT...THERE WERE SOME THUNDERSTORMS ASSOCIATED WITH THE WEAK TROUGH IN NORTHWEST ARIZONA...THAT IS CAUSING THE FEW LIGHT SHOWERS OR VIRGA PRESENTLY IN THE AREAS MENTIONED ABOVE. THE ETA AND NGM MODELS DO SUPPORT SOME INSTABILITY MOVING INTO SOUTH-CENTRAL ARIZONA THIS AFTERNOON. THE QUESTION REMAINS HOW FAR WEST TO INCLUDE THIS WEATHER FOR THE REMAINDER OF TODAY. AS OF NOW...ONLY MENTION OF SHOWERS AND THUNDERSTORMS IS OVER EASTERN MARICOPA COUNTY EASTWARD ACROSS SOUTHERN GILA AND NORTHWEST PINAL. MAY HAVE TO UPDATE TO INCLUDE AT LEAST ZONES 22 AND 27...BUT WILL WAIT FOR AWHILE. MEANWHILE...A SOMEWHAT STRONGER SYSTEM IS FORECAST TO AFFECT THE AREA LATER TONIGHT AND SATURDAY. BOTH THE 12Z ETA AND NGM ARE A LITTLE FURTHER TO THE SOUTHWEST WITH THIS SYSTEM THAN THE PREVIOUS RUN...WITH THE NGM BEING FURTHER TO THE SOUTHWEST THAN THE ETA. THERE ARE MORE DYNAMICS WITH THIS SECOND SYSTEM ON SATURDAY...MAINLY OVER THE EAST PORTION OF OUR CWA. HOWEVER...MUCH DRIER AIR IS BEING ADVECTED OVER SOUTHEAST CALIFORNIA AND FAR WESTERN ARIZONA DURING THIS TIME...SO WILL LIMIT ANY MENTION OF THUNDERSTORMS TO OUR EASTERN CWA FOR SATURDAY. LATEST ETA AND NGM MOS DO SUGGEST SOME INCREASE IN WINDS BOTH SATURDAY AND SUNDAY...AND THESE WINDS MAY HAVE TO BE INCREASED SOME ON THE GRIDS FOR THOSE PERIODS. MORE BENIGN WEATHER IS SLATED FOR SUNDAY INTO THE MIDDLE OF NEXT WEEK WITH HIGH PRESSURE ALOFT. DURING THE LATTER PART OF THE WEEK...THE LATEST EXTENDED GFS BRINGS IN A TROUGH THAT IS DEEPER AND STRONGER THAN PREVIOUS RUNS. THE MID SHIFT HAS WISELY DECIDED NOT TO CHANGE MUCH IN THE EXTENDED EXCEPT TO ADD MORE CLOUDS...SINCE THIS IS ONLY FIRST RUN SHOWING THIS TROUGH..PSR...WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && && $$ $$

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