570  
FXUS02 KWBC 040700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT THU OCT 04 2018  
 
VALID 12Z SUN OCT 07 2018 - 12Z THU OCT 11 2018  
 
...STORMY PATTERN FOR THE WEST/ROCKIES AND A CENTRAL U.S.  
EXCESSIVE RAINFALL THREAT...  
   
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
GUIDANCE IS OVERALL WELL CLUSTERED WITH LARGER SCALE DEVELOPMENT  
OF A HIGHLY AMPLIFIED WEATHER PATTERN FOR THE NATION THIS WEEKEND  
WELL INTO NEXT WEEK. THIS PATTERN OFFERS HEIGHT ANOMALIES OF 2+  
STANDARD DEVIATIONS ABOVE/BELOW NORMAL WITH A REINFORCING WESTERN  
U.S. TROUGH SANDWICHED BETWEEN RIDGES OVER THE EASTERN PACIFIC AND  
THE EAST COAST/ATLANTIC OCEAN. A DEEPENING/CLOSED LOW SETS UP OVER  
THE GREAT BASIN REGION AND MULTIPLE WAVES LIFT FROM THE GREAT  
BASIN/SOUTHERN AND CENTRAL ROCKIES INTO THE PLAINS WHERE A DEEP  
LAYERED SOUTHERLY FUNNEL OF GULF OF MEXICO MOISTURE POOLS TO 2+  
STANDARD DEVIATIONS FROM NORMAL INTO/OVER A SLOW MOVING BAROCLINIC  
ZONE. HOWEVER, DETERMINISTIC  
MODELS SHOW SIGNIFICANT RUN TO RUN VARIANCE WITH THE TIMING AND  
EMPHASIS OF SMALLER SCALE SYSTEMS EMBEDDED WITHIN THE SYNOPTIC  
SCALE FLOW ALOFT AND VARIED SPIN-UPS OF SURFACE FRONTAL LOWS.  
ACCORDINGLY, THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY  
DERIVED BY BLENDING THE 18 UTC GEFS MEAN AND 12 UTC ECMWF ENSEMBLE  
MEAN THAT SHOW A STRONG AND COMPATABLE PATTERN DEVELOPMENT SIGNAL.  
THIS MAINTAINS GOOD WPC CONTINUITY.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
HIGHLY UNSETTLED/WET WEATHER DEVELOPS AS A PERSISTENT AND HIGHLY  
AMPLIFIED TROUGH ALOFT SETS UP AND IS REINFORCED OVER THE WEST  
FROM THE GREAT BASIN/SOUTHWEST TO THE ROCKIES. TERRAIN/UPSLOPE  
FLOW SNOWS SPREAD DOWN TO FOCUS OVER THE NORTHERN GREAT  
BASIN/ROCKIES/PLAINS, ENHANCED BY A POST-FRONTAL COLD HIGH  
PRESSURE SURGES. WITH THE STRONG WARMING/BLOCKING RIDGE OVER THE  
EAST, WAVES ALONG/OVER CENTRAL U.S. FRONTS SHOW LITTLE EASTWARD  
PROGRESSION UNTIL LATE PERIOD. THIS SETS THE STAGE FOR A PROLONGED  
PERIOD FAVORING MULTIPLE ROUNDS OF HEAVY RAIN/CONVECTION AND AMPLE  
TRAINING IN A PRONOUNCED AXIS OFFERS AN EXTENDED THREAT OF  
EXCESSIVE RAINFALL. WARM SECTOR TEMPERATURES SOUTH OF THE FRONT  
WILL BE SUMMER-LIKE, SO A MAIN FRONTAL ZONE WILL REMAIN QUITE  
DEFINED.  
 
REGARDING TEMPERATURES, WELL BELOW AVERAGE NUMBERS ARE LIKELY FROM  
THE UPPER MIDWEST BACK TO THE WEST COAST. THE COLDEST AIR WILL  
RESIDE ACROSS THE NORTHERN/CENTRAL ROCKIES AND PLAINS WITH SOME  
DEPARTURES FROM CLIMATOLOGY UPWARDS TO 20 TO 30 DEGREES. HIGHEST  
ELEVATIONS WILL STRUGGLE TO GET OUT OF THE 30S FOR HIGHS WHILE  
OVERNIGHT LOWS PLUNGE INTO THE 20S. IN STARK CONTRAST, IT WILL  
FEEL LIKE SUMMER IN THE VAST WARM SECTOR WITH HIGHS AROUND 10 TO  
15 DEGREES ABOVE AVERAGE, ESPECIALLY NEAR THE GREAT LAKES/OHIO  
VALLEY. SOME DAILY RECORDS MAY BE BROKEN GIVEN THE VAST OVERNIGHT  
WARMTH.  
 
ELSEWHERE, A DEEP LAYERED EASTERLY FETCH OFF THE ATLANTIC  
FORTIFIES AND PERSISTS INTO NEXT WEEK ARCOSS THE SOUTHEAST,  
SPREADING SHOWERS ACROSS FLORIDA AND THE GULF COAST/ GULF OF  
MEXICO UNDERNEATH A NORTHWARD SHIFTING EASTERN U.S. CLOSED RIDGE  
ALOFT. A CARRIBEAN BASED TROPICAL DISTURBANCE MAY ALSO WORK INTO  
THE GULF OF MEXICO, BUT MODELS SHOW A WIDE ENVELOPE OF POTENTIAL  
DEVELOPMENTS THAT IS BEING MONITORED BY WPC/NHC.  
 
SCHICHTEL  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES 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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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