058  
FXUS02 KWBC 091556  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1056 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 ZONAL TO WEST-SOUTHWEST UPPER-LEVEL FLOW IS FORECAST TO PERSIST  
OVER THE EASTERN U.S. THROUGH NEXT WEEK AS A CLOSED LOW FORMS OFF  
THE DESERT SOUTHWEST AND LINGERS INTO LATE NEXT WEEK. THIS WILL  
PROMOTE MILDER TEMPERATURES TO SPREAD INTO THE EASTERN U.S. WITH  
PERIODS OF RAIN/THUNDERSTORMS IN THE DEEP SOUTH WHILE UNSETTLED  
WEATHER CAN BE EXPECTED IN THE DESERT SOUTHWEST.  
 
   
..GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
MODEL GUIDANCE THIS MORNING GENERALLY AGREES THAT A ZONAL TO  
WEST-SOUTHWEST UPPER-LEVEL FLOW WILL BECOME THE DOMINANT PATTERN  
OVER THE EASTERN TWO-THIRDS OF THE COUNTRY THROUGH NEXT WEEK AS A  
CLOSED LOW IS FORECAST TO FORM OFF THE DESERT SOUTHWEST AND LINGER  
INTO LATE NEXT WEEK. BOTH THE GFS AND ECMWF SOLUTIONS HAVE COME  
INTO BETTER AGREEMENT ON THE PLACEMENT OF THE UPPER LOW TO BE  
CENTERED A COUPLE OF HUNDRED MILES OFF THE SOUTHWEST CALIFORNIA  
COAST BY LATE WEDNESDAY. THEREAFTER, ALL GUIDANCE BEGINS TO PUSH  
THE SYSTEM ONSHORE LATE NEXT WEEK BUT WITH VARYING SPEEDS. THE  
TREND FOR MOST GUIDANCE FOR THE PAST FEW RUNS IS TO BRING THE  
SYSTEM ONSHORE FASTER BY NEXT FRIDAY...ALTHOUGH THE LATEST 06Z GFS  
HAS GONE BACK TO A SLOWER SOLUTION. THE ENSEMBLE MEANS LOOK QUITE  
AGREEABLE BY THAT POINT IN TIME. THEREFORE...THE MORNING WPC  
MEDIUM-RANGE PACKAGE ADOPTED A GENERAL COMPROMISE BETWEEN THE 06Z  
GFS WITH THE 00Z ECMWF BEGINNING ON DAY 3 (MON) AND TRENDING  
TOWARD MOSTLY THEIR CORRESPONDING ENSEMBLE MEANS BY DAY 7.  
 
   
..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 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 THE ZONAL TO  
WEST-SOUTHWEST UPPER-LEVEL FLOW FORECAST TO PERSIST OVER THE  
EASTERN U.S. THIS PATTERN IN CONJUNCTION WITH UPPER RIDGING MOVING  
ACROSS FLORIDA WILL SUPPORT ABOVE AVERAGE TEMPERATURES ACROSS MUCH  
OF THE EASTERN THIRD OF THE LOWER 48...ALTHOUGH ARCTIC AIR SHOULD  
ATTEMPT TO MAKE ITS WAY BACK INTO THE NORTHEAST U.S. LATE NEXT  
WEEK. FARTHER SOUTH...STALLED FRONTAL BOUNDARY IN THE SOUTHEAST  
WILL FOCUS PRECIPITATION IN THE VICINITY EARLY IN THE WEEK WITH  
PERHAPS ANOTHER RESURGENCE LATER IN THE WEEK AS THE FRONT  
ASSOCIATED WITH THE AFOREMENTIONED ARCTIC INTRUSION DROPS IN FROM  
THE NORTHWEST. SOME MIXED PRECIP. IS POSSIBLE ACROSS THE MIDWEST  
NEXT FRIDAY BEHIND THE ARCTIC FRONT.  
 
KONG/FRACASSO  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page