343  
FXUS02 KWBC 121446  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1045 AM EDT FRI OCT 12 2018  
 
VALID 12Z MON OCT 15 2018 - 12Z FRI OCT 19 2018  
 
...IMPRESSIVE RECORD COLD FOR THE CENTRAL/SOUTHERN PLAINS EARLY  
NEXT WEEK...  
 
   
..PATTERN OVERVIEW
 
 
AN UPPER LOW NEAR BAFFIN ISLAND/DAVIS STRAIT WILL SLOWLY TRANSLATE  
SOUTHEASTWARD AS UPPER RIDGING IN THE NORTHEAST PACIFIC BREAKS  
DOWN. THIS WILL ALLOW TROUGHING INITIALLY OVER THE GREAT LAKES TO  
SPLIT BETWEEN A NORTHERN AND SOUTHERN PORTION WITH THE FORMER  
EXITING MUCH QUICKER THAN THE LATTER. ACROSS FLORIDA, SUBTROPICAL  
RIDGING WILL HOLD IN PLACE, PREVENTING A COLD FRONT FROM SLIPPING  
SOUTHWARD TO LAKE OKEECHOBEE.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
A MULTI-MODEL DETERMINISTIC BLEND (INCLUDING THE ECMWF/GFS/UKMET)  
SERVED AS A STARTING POINT FOR THE FORECAST DURING DAYS 3-5  
(MON-WED). THE GFS REMAINS A BIT QUICKER THAN THE ECMWF/UKMET WITH  
SHORTWAVE ENERGY CROSSING THE GREAT LAKES ON MON, BUT HAS MOVED  
CLOSER TO THE SLOWER SOLUTIONS RELATIVE TO YESTERDAY AND IS NOW  
USABLE. CONSENSUS REMAINS HIGH THAT ENERGY WILL SEPARATE FROM THE  
TRAILING END OF THE CENTRAL U.S. TROUGH AND CUTOFF/LINGER ACROSS  
THE SOUTHWEST, AND THE DESCRIBED BLEND REPRESENTS THIS PROCESS  
WELL. BY DAYS 6-7 (THU-FRI) CONSENSUS SUGGESTS THAT THE ENERGY  
PREVIOUSLY CUTOFF OVER THE SOUTHWEST WILL BEGIN TO SLOWLY DRIFT  
EASTWARD TOWARD THE CENTRAL U.S. SPREAD AMONG THE DETERMINISTIC  
GUIDANCE/ENSEMBLE MEANS WITH RESPECT TO THIS IS RELATIVELY LOW,  
ALTHOUGH A NUMBER OF INDIVIDUAL ENSEMBLE MEMBERS (PARTICULARLY IN  
THE GEFS/NAEFS) SHOW SLOWER SOLUTIONS WHICH ARE NOT NECESSARILY  
OUT OF THE QUESTION GIVEN THE BROAD FLOW AMPLIFICATION IN PLACE.  
BOOSTED WEIGHTING OF ECENS/NAEFS ENSEMBLE MEANS IN THE FORECAST  
DURING DAYS 6-7, WITH A MAJORITY ENSEMBLE MEANS BY DAY 7 TO  
ACCOUNT FOR SOMEWHAT INCREASED SPREAD IN THE SOUTHWEST/CENTRAL  
U.S. AS WELL AS WITH ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY  
CROSSING CENTRAL CANADA.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
WELL BELOW AVERAGE TEMPERATURES (LIKELY BREAKING RECORD LOW MINIMA  
AND MAXIMA OVER MANY STATIONS AND STATES) WILL SINK SOUTHWARD  
BEHIND A STRONG COLD FRONT LATE THIS WEEKEND INTO NEXT MONDAY.  
HIGHS IN THE 40S ARE FORECAST FOR MOST OF THE CENTRAL PLAINS INTO  
TEXAS EVEN TO THE BIG BEND WHICH WILL BE ABOUT 25-35 DEGREES BELOW  
AVERAGE. SOME LOCATIONS MAY BREAK THEIR RECORD LOW DAYTIME HIGH  
TEMPERATURE BY 5-10 DEGREES EVEN WHERE RECORDS GO BACK OVER 100  
YEARS. THE COLD WILL START TO RELENT AFTER MONDAY AS IT SETTLES TO  
THE GULF COAST AND LOWER MISSISSIPPI RIVER VALLEY. THE COLD FRONT  
WILL HAVE LESS BITE FARTHER EAST FROM THE GREAT LAKES TO THE  
NORTHEAST/MID-ATLANTIC WHERE TEMPERATURES WILL ONLY BE A FEW  
DEGREES BELOW AVERAGE. TO THE SOUTH, FLORIDA WILL MAINTAIN ABOVE  
AVERAGE TEMPERATURES THANKS TO UPPER RIDGING.  
 
PRECIPITATION MAY BE HEAVY FROM TEXAS NORTHEASTWARD AS THE UPPER  
LOW BEHIND FUTURE EX-SERGIO MEANDERS EASTWARD THROUGH THE FOUR  
CORNERS REGION AND MOISTURE FROM THE WESTERN GULF FLOWS NORTHWARD  
ATOP THE FRONT. THE RAIN AXIS WILL EXTEND TO THE MID-ATLANTIC BUT  
IN LESSENED AMOUNTS. THE REST OF THE LOWER 48 BEHIND THE FRONT  
WILL BE LARGELY DRY WITH SOME SHOWERS AROUND THE LAKES (SOME SNOW,  
SOME RAIN). WIDESPREAD SNOW (SOME LOWER ELEVATION RAIN) WILL EXIT  
THE SOUTHERN ROCKIES ON MONDAY WITH SOME SNOW ACCUMULATION  
THEREAFTER AS THE UPPER LOW SWINGS THROUGH.  
 
RYAN/FRACASSO  
 
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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