964  
FXUS02 KWBC 151545  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1144 AM EDT FRI JUN 15 2018  
 
VALID 12Z MON JUN 18 2018 - 12Z FRI JUN 22 2018  
 
...HEAVY RAINS POSSIBLE FOR PORTIONS OF THE NORTHWESTERN GULF  
COAST AND PORTIONS OF THE CENTRAL/NORTHERN ROCKIES AND ADJACENT  
PLAINS...  
 
...HOT/HUMID FOR PORTIONS OF THE MIDWEST TO THE MID-ATLANTIC AND  
SOUTHEAST EARLY NEXT WEEK...  
 
   
..PATTERN OVERVIEW AND GUIDANCE ASSESSMENT/PREFERENCES
 
 
AN UPPER LEVEL LOW OVER THE GREAT BASIN ON MONDAY SHOULD SLOWLY  
BEGIN TO WEAKEN AS RIDGING IN THE EAST GIVES WAY TO CYCLONIC FLOW  
THROUGH THE GREAT LAKES. THIS BRINGS A SURFACE COLD FRONT SLOWLY  
SOUTHWARD OUT OF THE GREAT LAKES ON MONDAY, EVENTUALLY LINGERING  
ACROSS THE MID-ATLANTIC AND BACK TO THE PLAINS THROUGH THE REST OF  
THE WEEK. TO THE SOUTH, A WEAKNESS ALOFT AND A TROPICAL WAVE AT  
THE SURFACE IS EXPECTED TO PRODUCE HEAVY RAINFALL ALONG THE  
NORTHWEST GULF COAST REGION NEXT WEEK.  
 
FOR DAYS 3-5, THE GFS/ECMWF AND THEIR ENSEMBLE MEANS WERE IN VERY  
GOOD AGREEMENT SO A MAJORITY DETERMINISTIC GFS/ECMWF BLEND SERVED  
AS A GOOD STARTING POINT. BY DAYS 6-7, THE MOST NOTABLE DIFFERENCE  
WAS THE 06Z GFS WAS FASTER TO ERODE THE WESTERN LOW AND EJECT THE  
ENERGY EASTWARD INTO THE PLAINS. THE ECMWF ALONG WITH THE EC AND  
GEFS ENSEMBLE MEANS WOULD SUPPORT HOLDING BACK THE LOW ACROSS THE  
GREAT BASIN EVEN INTO DAY 7. THE GFS THE PAST FEW DAYS HAS BEEN  
FLIP-FLOPPING BOTH SOLUTIONS, SO FOR DAYS 6-7 THE WPC BLEND LEANED  
HEAVILY TOWARDS THE ECMWF/GEFS ENSEMBLE MEANS AND THE  
DETERMINISTIC ECMWF ALL OF WHICH HAVE SHOWED BETTER OVERALL  
RUN-TO-RUN CONTINUITY.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
LOCALLY HEAVY (AND REGIONALLY MODEST) RAIN IS PROBABLE FOR THE  
NORTHWESTERN GULF COAST AS THE BROAD TROUGH/AREA OF DISTURBED  
WEATHER MOVES ONSHORE EARLY IN THE PERIOD. MULTI-INCH RAINFALL  
TOTALS APPEAR POSSIBLE, FOCUSED OVER PORTIONS OF SOUTHEASTERN  
TEXAS AND SOUTHWESTERN LOUISIANA. TO THE WEST AND NORTHWEST, THE  
UPPER LOW AND MOISTURE FROM (BY THEN) THE REMNANTS OF BUD WILL  
COMBINE TO PRODUCE SEVERAL DAYS OF WET WEATHER FOR THE  
CENTRAL/NORTHERN ROCKIES AND THE ADJACENT HIGH PLAINS. MOISTURE  
MAY ALSO POOL EASTWARD ALONG THE QUASI-STATIONARY FRONTAL BOUNDARY  
AS IT LINGERS ACROSS THE CENTRAL PLAINS FOR MUCH OF THE PERIOD.  
TOTALS OF 1-2+" MAY BE COMMON FOR THE 5-DAY QPF TOTAL.  
 
TEMPERATURES IN THE EAST WILL BE WELL ABOVE AVERAGE (+10 TO +20F)  
TO START THE MEDIUM RANGE (MONDAY) FROM THE MIDWEST TO THE  
NORTHEAST/MID-ATLANTIC WITH READINGS WELL INTO THE 80S/NORTH AND  
90S/SOUTH, AND APPROACHING 100 IN SOME LOCATIONS. MANY DAILY  
RECORD MAXES WILL LIKELY BE TIED/BROKEN ALONG THE I-95 CORRIDOR.  
WITH DEW POINTS RANGING FROM THE UPPER 60S TO MID 70S, HEAT  
INDICES WILL BE OVER 100F AND CLOSE TO 110F FOR SOME AREAS. THE  
PACIFIC NORTHWEST WILL ALSO SEE WELL ABOVE AVERAGE TEMPERATURES  
(ESPECIALLY INLAND) AS THEY WILL BE LOCATED TO THE NORTHWEST OF  
THE UPPER LOW AND COINCIDENT WITH RIDGING MOVING OUT OF THE  
NORTHEAST PACIFIC. TEMPERATURES WILL RISE INTO THE 70S/80S WEST OF  
THE CASCADES AND 90S IN THE INTERIOR OF WASHINGTON/OREGON.  
MEANWHILE, ACROSS THE INTERMOUNTAIN WEST AND MUCH OF THE PLAINS  
STATES, TEMPERATURES ARE FORECAST TO BE BELOW NORMAL UNDER THE  
INFLUENCE OF THE STUBBORN UPPER LOW AND COPIOUS AMOUNTS OF  
MOISTURE STREAMING INTO THE REGION.  
 
SANTORELLI/FRACASSO  
 
WPC MEDIUM RANGE FORECASTS OF 500 MB HEIGHTS, SURFACE SYSTEMS,  
WEATHER GRIDS, QUANTITATIVE PRECIPITATION, AND WINTER WEATHER  
OUTLOOK PROBABILITIES CAN BE FOUND AT:  
 
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTP://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTP://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTP://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
 

 
 
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