602  
FXUS02 KWBC 071604  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1103 AM EST THU FEB 07 2019  
 
VALID 12Z SUN FEB 10 2019 - 12Z THU FEB 14 2019  
 
...OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT AND  
PREFERENCES...  
 
PACIFIC FLOW REMAINS FRAUGHT WITH UNCERTAINTY SURROUNDING A  
STUBBORN UPPER HIGH NEAR THE GULF OF ALASKA. TROUGHING WILL  
GENERALLY STAY FOCUSED NEAR/ALONG THE WEST COAST OF THE LOWER 48,  
REINFORCED EITHER FROM THE NORTH (ON THE EAST SIDE OF THE UPPER  
RIDGE) OR FROM THE WEST (UNDERNEATH THE UPPER RIDGE). AN UPPER  
HIGH OVER THE FLORIDA STRAITS WILL WEAKEN AND SPLIT E-W FROM  
MEXICO TO THE GREAT ANTILLES, OPENING UP BROAD TROUGHING INTO THE  
EAST. HOWEVER, HOW THIS UNFOLDS IS QUITE UNCERTAIN AS EVIDENCED BY  
THE NOTABLE TIMING/TRACK DIFFERENCES AMONG THE GUIDANCE FROM AS  
EARLY AS 48 HRS NEAR ALASKA.  
 
BY DAY 4 (MON), THE 00Z ECMWF AND ITS ENSEMBLE MEAN, ALONG WITH  
THE UKMET AND TO SOME EXTENT THE CMC, SPLIT THE TROUGHING ACROSS  
THE WESTERN U.S. INTO TWO DISTINCT AREAS AS UPSTREAM ENERGY COMING  
IN KICKS THE FIRST TROUGH FARTHER EAST. THE 00Z AND 06Z GFS AND  
GEFS, ON THE OTHER HAND, HAD A SINGULAR TROUGH THAT HANGS FARTHER  
WEST AS THE UPSTREAM ENERGY JOINS WITH THE PREEXISTING TROUGH. THE  
FORMER SEEMS MORE LIKELY, AND SINCE THE MODEL CONSENSUS LEANS THAT  
WAY, THE MEDIUM RANGE PRODUCTS MAINLY INCORPORATED THOSE SOLUTIONS  
THROUGH DAY 5. BY DAYS 6-7, THE GFS AND GEFS BECAME USEFUL AGAIN  
AS, AFTER A DIFFERENT EVOLUTION TO GET THERE, THE TWO MAIN SYSTEMS  
OF THE UPPER LOW OVER THE GREAT LAKES AND THE UPPER LOW OFFSHORE  
OF THE WESTERN U.S. LOOK FAIRLY SIMILAR AT DAY 6. ADDITIONALLY,  
THE GENERAL TROUGHING THE 00Z GEFS MEMBERS HAVE IN THE  
SOUTHWESTERN U.S. AT DAY 7 FIT BETTER WITH WHAT TELECONNECTIONS  
(BASED ON THE PERSISTENT UPPER RIDGE IN THE GULF OF ALASKA) WOULD  
SUGGEST.  
 
AT THE SURFACE, THERE IS BETTER AGREEMENT TODAY THAT A SURFACE LOW  
AND ASSOCIATED FRONTS WILL DEVELOP IN THE LEE OF THE ROCKIES, MOVE  
ACROSS THE MISSISSIPPI VALLEY ON MONDAY NIGHT AND TUESDAY, AND  
INTO THE UPPER MIDWEST TUESDAY NIGHT AND WEDNESDAY. HOWEVER,  
DETAILS IN TIMING, PLACEMENT, AND STRENGTH OF THE LOW WILL HAVE TO  
BE IRONED OUT LATER. A COUPLE MORE SYSTEMS WILL SINK THROUGH THE  
WEST AS WELL.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
LATE THIS WEEKEND AND INTO EARLY NEXT WEEK ANOTHER ROUND OF  
POTENTIALLY HEAVY PRECIPITATION WILL SPREAD INTO THE LOWER TO  
MID-MISSISSIPPI AND TENNESSEE VALLEYS AS MOISTURE SURGES NORTHWARD  
ATOP A WARM FRONT ALONG THE GULF COAST. AS THE LOW PRESSURE SYSTEM  
STRENGTHENS INTO THE MIDWEST ON TUESDAY, PRECIPITATION IS EXPECTED  
TO PUSH THROUGH THE OHIO VALLEY AND INTO THE  
MID-ATLANTIC/NORTHEAST. WITH TEMPERATURES NEAR/BELOW FREEZING,  
WINTRY PRECIPITATION WILL BE POSSIBLE ON THE NORTHWEST/NORTH SIDE  
OF THE LOW AND WELL AHEAD OF THE WARM FRONT. IN THE WEST WHERE  
PERSISTENT TROUGHING WILL REMAIN, MODERATE PRECIPITATION (VALLEY  
RAIN AND MOUNTAIN SNOW) IS EXPECTED ACROSS THE PACIFIC NORTHWEST  
AT DAYS 4-5, SHIFTING SOUTHWARD ON DAY 6-7 TO TAKE AIM AT MAINLY  
CALIFORNIA.  
 
MUCH BELOW AVERAGE TEMPERATURES WILL REMAIN ANCHORED OVER THE HIGH  
PLAINS THROUGHOUT THE MEDIUM RANGE PERIOD (MT/ND/SD). THE REST OF  
THE WEST IS FORECAST TO SEE BELOW AVERAGE TEMPERATURES DUE TO THE  
PERSISTENT TROUGHING AND EPISODIC COOLER SURGES OF CANADIAN AIR.  
THIS MAY RESULT IN SOME RECORD COLD TEMPERATURES FOR COASTAL WA/OR  
AND NORTHERN CALIFORNIA SUN/MON. SLIGHTLY BELOW AVERAGE  
TEMPERATURES WILL BLEED INTO THE UPPER MIDWEST AND THEN GREAT  
LAKES BEHIND THE MIDWEEK SYSTEM. A SURGE OF ABOVE AVERAGE  
TEMPERATURES WILL PRECEDE THE COLD FRONT ESPECIALLY TUESDAY.  
 
TATE/FRACASSO  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION AND WINTER WEATHER OUTLOOK  
PROBABILITIES ARE FOUND AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
 

 
 
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