146  
FXUS02 KWBC 141953  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
352 PM EDT TUE MAY 14 2019  
 
VALID 12Z FRI MAY 17 2019 - 12Z TUE MAY 21 2019  
   
..OVERVIEW AND WEATHER HIGHLIGHTS/THREATS
 
 
OVERALL, AMPLIFIED MEAN TROUGHING ALOFT WILL BRING A WET PERIOD TO  
A LARGE PORTION OF THE WESTERN U.S. AND PLAINS STATES DURING THE  
WEEKEND TO EARLY NEXT WEEK. MUCH OF THE WESTERN US TO THE  
NORTHERN HIGH PLAINS WILL TURN COLDER, WITH MUCH OF THE MID-LOWER  
MS VALLEY EASTWARD TURNING MORE SUMMERLIKE.  
 
GUIDANCE IS STEADILY TRENDING TOWARD RESOLVING THE LEADING STRONG  
TROUGH PROGRESSING FROM THE WEST AND ROCKIES FRI/SAT AND IN ERNEST  
OVER THE CENTRAL THEN EAST-CENTRAL STATES FROM THE WEEKEND INTO  
EARLY NEXT WEEK. THIS NEG-TILT SYSTEM WILL SPAWN SURFACE SYSTEM  
GENESIS AND OFFERS ROUNDS OF LOCALLY HEAVY CONVECTION/SEVERE  
WEATHER AS PER SPC. UNDERNEATH, A GRADUALLY WEAKENING CLOSED LOW  
IS EXPECTED TO MEANDER FROM THE NORTHERN TO EASTERN GULF OF MEXICO  
AND OFFER SOME HEAVY RAIN POTENTIAL FOR SOUTHERN FLORIDA.  
 
THERE IS SOME AGREEMENT THAT UPSTREAM FLOW WILL BRING ANOTHER  
ROUND OF STRONG HEIGHT FALLS AND WIDESPREAD PRECIPITATION/TERRAIN  
ENHANCED SNOWS TO THE WESTERN STATES FRI INTO THIS WEEKEND,  
CONTINUING INLAND EARLY WEEK ACROSS THE GREAT BASIN TO THE HIGH  
PLAINS. UPSTREAM, THERE IS A STILL UNCERTAIN GUIDANCE SIGNAL TO  
DEVELOP A DEEPER LOW IN THE EASTERN PACIFIC EARLY NEXT WEEK THAT  
OFFERS POTENTIAL TO REACH CA AND THE GREAT BASIN/SOUTHWEST BY  
TUESDAY 21 MAY ALONG WITH RENEWED UNSETTLED WEATHER/PRECIPITATION.  
 
MEANWHILE, MODEL AND ENSEMBLE SOLUTIONS CONTINUE TO SHOW ABOVE  
NORMAL FORECAST SPREAD WITH RESPECT TO DOWNSTREAM NORTHEASTERN  
U.S./MID-ATLANTIC FLOW THROUGH THE MEDIUM RANGE PERIOD AS A SERIES  
OF POTENT CANADIAN UPPER SYSTEMS PROGRESS WITHIN AN ENERGETIC  
NORTHERN STREAM. THESE UPPER SYSTEMS AND SURFACE SYSTEM  
REFLECTIONS HAVE TRENDED STRONGER INTO THE WEEKEND.  
TELECONNECTIONS RELATIVE TO THE NEGATIVE HEIGHT ANOMALY CENTER  
ASSOCIATED WITH THE WEST COAST MEAN TROUGH THEN FAVOR MODEST  
CYCLONIC FLOW ALOFT INTO EARLY NEXT WEEK.  
 
   
..GUIDANCE ASSESSEMNT AND PREFERENCE
 
 
THE LATEST DETERMINISTIC MODELS (06 UTC GFS/FV3 AND 00 UTC  
ECMWF/UKMET/CANADIAN) SEEM TO OFFER BETTER THAN EXPECTED FORECAST  
CLUSTERING FRI INTO SUN MORNING, BUT CONFIDENCE REMAINS SOMEWHAT  
MUTED DUE TO LESS THAN STELLAR CONTINUITY ISSUES. EVEN SO, THE WPC  
PRODUCT SUITE PRIMARILY WAS DERIVED FROM A COMPOSITE MODEL  
SOLUTION DURING THIS PERIOD THAT SEEMS INCREASINGLY REASONABLE  
BEFORE QUICKLY TRANSITIONING TO THE MUCH MORE COMPATABLE ENSEMBLE  
MEANS (06 UTC GEFS/00 UTC ECMWF ENSEMBLE MEAN) INTO EARLY NEXT  
WEEK AMID GROWING FORECAST SPREAD.  
 
SCHICHTEL  
 
ADDITIONAL 3-7 DAY HAZARDS INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
HAZARDS:  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE CENTRAL GREAT BASIN,  
CALIFORNIA, AND THE SOUTHWEST, FRI, MAY 17 AND SUN-TUE, MAY 19-MAY  
21.  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE  
CENTRAL GREAT BASIN, THE NORTHERN ROCKIES, THE NORTHERN GREAT  
BASIN, AND THE NORTHERN PLAINS, FRI-SAT, MAY 17-MAY 18AND SUN-TUE,  
MAY 19-MAY 21.  
- HEAVY RAIN ACROSS PORTIONS OF CALIFORNIA AND THE PACIFIC  
NORTHWEST, FRI-SAT, MAY 17-MAY 18AND SUN-MON, MAY 19-MAY 20.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE LOWER  
MISSISSIPPI VALLEY, THE NORTHERN PLAINS, THE GREAT LAKES, THE  
MIDDLE MISSISSIPPI VALLEY, THE UPPER MISSISSIPPI VALLEY, AND THE  
SOUTHERN PLAINS, FRI-SUN, MAY 17-MAY 19.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE LOWER  
MISSISSIPPI VALLEY, THE NORTHERN PLAINS, THE MIDDLE MISSISSIPPI  
VALLEY, THE UPPER MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS,  
MON-TUE, MAY 20-MAY 21.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE  
MISSISSIPPI VALLEY, THE SOUTHERN PLAINS, THE UPPER MISSISSIPPI  
VALLEY, AND THE NORTHERN PLAINS, FRI, MAY 17.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE  
MISSISSIPPI VALLEY, THE LOWER MISSISSIPPI VALLEY, THE SOUTHERN  
PLAINS, AND THE UPPER MISSISSIPPI VALLEY, SAT, MAY 18.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS AND THE  
SOUTHERN PLAINS, MON, MAY 20.  
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS, THE LOWER  
MISSISSIPPI VALLEY, THE NORTHERN PLAINS, THE MIDDLE MISSISSIPPI  
VALLEY, THE UPPER MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS,  
TUE, MAY 21.  
- SEVERE WEATHER ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI VALLEY,  
THE LOWER MISSISSIPPI VALLEY, THE GREAT LAKES, THE OHIO VALLEY,  
AND THE TENNESSEE VALLEY, SUN, MAY 19.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN ROCKIES.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE CENTRAL  
PLAINS, THE LOWER MISSISSIPPI VALLEY, THE NORTHERN PLAINS, THE  
GREAT LAKES, THE MIDDLE MISSISSIPPI VALLEY, THE UPPER MISSISSIPPI  
VALLEY, THE SOUTHEAST, THE SOUTHERN PLAINS, AND THE OHIO VALLEY.  
- FLOODING LIKELY ACROSS PORTIONS OF THE NORTHERN ROCKIES AND THE  
NORTHERN GREAT BASIN.  
- MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF CALIFORNIA,  
THE CENTRAL GREAT BASIN, THE PACIFIC NORTHWEST, AND THE NORTHERN  
GREAT BASIN, MON-TUE, MAY 20-MAY 21.  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDICES ARE 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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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