810  
FXUS02 KWBC 090546  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1246 AM EST FRI FEB 09 2018  
 
VALID 12Z MON FEB 12 2018 - 12Z FRI FEB 16 2018  
   
..WIDESPREAD PRECIPITATION EXPECTED IN THE SOUTHWEST NEXT WEEK
 
 
   
..OVERVIEW
 
 
A STRONG JET OFF THE EASTERN ASIAN CONTINENT WILL FAVOR SPLIT FLOW  
BETWEEN HAWAI'I AND ALASKA AND A CLOSED LOW NEAR CALIFORNIA NEXT  
WEEK. UPPER RIDGING IN THE NORTHERN/NORTHWESTERN ATLANTIC IS  
FORECAST TO MIGRATE TOWARD THE GULF OF MEXICO DURING THE PERIOD,  
ALLOWING BROAD CYCLONIC FLOW TO DOMINATE THE CENTRAL/EASTERN TWO  
THIRDS OF THE LOWER 48.  
 
   
..GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
LATEST GFS/ECMWF AND THEIR ENSEMBLE MEANS OFFERED GOOD CLUSTERING  
WITH THE UPPER LOW FORMATION BY NEXT TUESDAY NEAR COASTAL CENTRAL  
CALIFORNIA AND ITS TRACK SOUTHWARD JUST WEST OF 120W TO NEAR 30N  
LATE WEDNESDAY. THEREAFTER, THE ENSEMBLES FAVOR A SLOWER TURN  
EASTWARD BACK INLAND COMPARED TO WHAT THE 12Z/18Z GFS SHOWED.  
GIVEN THE ENSEMBLE TREND TOWARD SUCH A SLOWER SOLUTION AND THE  
TYPICAL FAST BIAS OF THE GFS BEYOND ~5 DAYS, OPTED TO RELY ON THE  
SLOWER CLUSTER OF THE 12Z ECMWF/ECMWF ENSEMBLE MEAN AND THE 18Z  
GEFS MEAN WHICH MATCHED THE ECMWF ENSEMBLE MEAN QUITE NICELY.  
PREVIOUS GFS RUNS WERE MUCH SLOWER WITH THIS CLOSED LOW BUT IT HAS  
WAVERED BACK AND FORTH. IN THE EAST, BLENDED/CONSENSUS FORECAST  
RESOLVED THE FRONTAL BOUNDARIES FAIRLY WELL GIVEN TYPICAL  
TIMING/STRENGTH DIFFERENCES.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
SOUTHERN CALIFORNIA INTO THE DESERT SOUTHWEST AND FOUR CORNERS  
REGION STAND THE BEST CHANCE FOR APPRECIABLE RAIN AND HIGHER  
ELEVATION SNOW LATER NEXT WEEK. A SLOWER CLOSED LOW WILL ALLOW  
MOISTURE TO STREAM NORTHWARD AND NORTHEASTWARD FROM THE  
SUB-TROPICS/TROPICS (SW OF BAJA CALIFORNIA) FOR A FEW DAYS,  
FOCUSED PRIMARILY INTO AZ/NM. THIS COULD BRING WIDESPREAD  
0.25-0.50" RAINFALL TO AZ/NM (LOCALLY HEAVIER) NEXT THU-FRI.  
TEMPERATURES WILL BE GENERALLY BE ABOVE AVERAGE OVERNIGHT BUT  
BELOW AVERAGE DURING THE DAY GIVEN CLOUD COVER AND PRECIPITATION.  
 
TO THE NORTH, GENERALLY BELOW AVERAGE TEMPERATURES ARE EXPECTED  
FROM MONTANA AND THE HIGH PLAINS INTO THE UPPER MIDWEST AS A  
COUPLE WEAKER SHORTWAVES GET SWEPT ALONG IN THE QUICK N/NW FLOW.  
UPPER RIDGING MOVING ACROSS FLORIDA WILL SUPPORT ABOVE AVERAGE  
TEMPERATURES IN MUCH OF THE EASTERN THIRD OF THE LOWER 48. STALLED  
FRONTAL BOUNDARY EARLY NEXT WEEK IN THE SOUTHEAST WILL FOCUS  
PRECIPITATION ALONG IT EARLY IN THE WEEK WITH PERHAPS ANOTHER  
RESURGENCE LATER IN THE WEEK AS ANOTHER FRONT DROPS IN FROM THE  
NORTHWEST.  
 
FRACASSO  
 

 
 
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