021  
FXUS63 KBIS 271720  
AFDBIS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BISMARCK ND  
1220 PM CDT THU APR 27 2017  
   
UPDATE
 
 
ISSUED AT 1219 PM CDT THU APR 27 2017  
 
LOW CLOUDS ACROSS SOUTHERN ND HAVE MOVED SOUTH FOR THE MOST PART,  
WITH ONLY A FEW RESIDUAL CLOUDS AROUND THE HETTINGER AREA REMAINING.  
THE CUMULUS FIELD THAT HAD DEVELOPED A FEW HOURS AGO BETWEEN  
DICKINSON AND BISMARCK HAS BEGUN TO DISSIPATE. WE STILL MAY SEE SOME  
SCATTERED CUMULUS DEVELOP THIS AFTERNOON, BUT MOSTLY SUNNY SKIES  
SHOULD BE THE MAIN SKY CONDITION MOST AREAS. REGARDING TEMPERATURES,  
LOWERED EXPECTED HIGH TEMPERATURES IN EASTERN PORTIONS OF LAMOURE  
AND DICKEY COUNTIES - WHERE THERE WERE 2 TO 4 INCHES OF SNOW  
ACCUMULATION YESTERDAY. MELTING SNOW THERE SHOULD ACT TO LOWER  
EXPECTED HIGHS. OTHERWISE THE FORECAST FOR THE AFTERNOON IS ON  
TRACK.  
 
UPDATE ISSUED AT 936 AM CDT THU APR 27 2017  
 
ONLY CHANGES THIS UPDATE WAS TO REFINE CLOUD COVER. LATEST  
ITERATIONS OF THE SHORT TERM HIGH RES MODELS DO NOT EXPECT LOW  
CLOUDS THAT ARE CURRENTLY ACROSS FAR SOUTHERN ND TO CREEP NORTHWARD.  
THUS THINKING IS THAT SOME SCATTERED LATE MORNING/AFTERNOON CUMULUS  
MAY DEVELOP...BRINGING A MOSTLY SUNNY DAY ACROSS MOST OF WESTERN AND  
CENTRAL ND THIS AFTERNOON. MINOR HOURLY TEMPERATURE TRENDS WERE  
ADJUSTED BUT OTHERWISE FORECAST ON TRACK.  
 
UPDATE ISSUED AT 648 AM CDT THU APR 27 2017  
 
LITTLE CHANGE WITH THIS UPDATE OTHER THAN TO FURTHER REFINE THE  
CLOUD COVER FORECAST BASED ON THE LATEST TRENDS IN STRATUS FROM  
SATELLITE IMAGERY, WHICH SHOWS CLEARING PUSHING SOUTH FROM ROLLA  
TO HARVEY, AND A FRAGMENT OF LOW CLOUD INDEED PUSHING WESTWARD  
ACROSS SOUTHWEST ND THROUGH THE HETTINGER AND MOTT AREAS. THE 11  
UTC SURFACE ANALYSIS ALSO REVEALS TEMPERATURES OF 14 TO 16 F IN  
THE HAZEN AND GLEN ULLIN AREAS WHERE LIGHT WINDS AND A CLEAR SKY  
ALLOWED FOR EFFICIENT RADIATIONAL COOLING IN OUR DRY AIR MASS.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 459 AM CDT THU APR 27 2017  
 
DRY AND QUIET WEATHER IS EXPECTED TODAY AND TONIGHT.  
 
SYNOPTICALLY-SPEAKING, BROADLY CYCLONIC FLOW WILL PERSIST ACROSS  
THE WESTERN AND CENTRAL U.S. TODAY AND TONIGHT, WITH THE PRIMARY  
FEATURE OF INTEREST AN INTENSE UPPER-LEVEL SPEED MAXIMUM DENOTED  
BY 300 MB WIND SPEEDS OF AT LEAST 125 KT THAT WILL EXTEND FROM THE  
OREGON COASTLINE SOUTHEASTWARD INTO THE TEXAS PANHANDLE BY 00 UTC.  
THE EVOLUTION OF THE JET STREAK AND RELATED SUBTLE RECONFIGURATION  
OF HEIGHT FIELDS ALOFT WILL RESULT IN THE SLOW NORTHEAST MOVEMENT  
OF THE MID- AND UPPER-LEVEL LOW LOCATED IN NORTHWESTERN MN EARLY  
THIS MORNING INTO CENTRAL ONTARIO BY LATE TONIGHT. LOCALLY, THIS  
WILL YIELD WEAK HEIGHT RISES ACROSS WESTERN AND CENTRAL ND ALONG  
WITH WEAK WARM AIR ADVECTION. THE RESULT SHOULD BE A WARMER DAY  
WITH HIGHS RANGING FROM THE LOWER 40S F IN THE ROLLA AND JAMESTOWN  
AREAS TO AROUND 50 F IN WESTERN AND SOUTH CENTRAL ND. NOTE THAT WE  
DID WEIGHT THE FORECAST TODAY SLIGHTLY TOWARD WARMER MOS GUIDANCE  
FROM THE 00 UTC MODEL CYCLE IN RESPECT TO THE TRENDS OBSERVED IN  
WESTERN ND ON WEDNESDAY, AND IN RECOGNITION OF THE VERY DRY AIR  
MASS THAT WILL BE IN PLACE TODAY IN SUPPORT OF EFFICIENT DIABATIC  
HEATING GIVEN SUNSHINE. THE DRY AIR IS STATISTICALLY BORNE OUT BY  
THE 00 UTC NAEFS GUIDANCE, WHICH REVEALS THAT THE PRECIPITABLE  
WATER VALUES THAT WILL AVERAGE NEAR 0.20" ARE IN THE LOWEST 2.5  
PERCENT OF VALUES OBSERVED AT THIS TIME OF THE YEAR.  
 
NOTE THAT DESPITE THE DRY AIR MASS, LIGHT WIND FIELDS THROUGH THE  
LOWER AND MIDDLE ATMOSPHERE AND AN INVERSION LAYER BASED NEAR 850  
MB PER 00 UTC NAM AND GFS FORECAST SOUNDINGS SUGGESTS VERTICAL  
MIXING WILL BE RELATIVELY WEAK. THAT SHOULD TEND TO KEEP HUMIDITY  
VALUES FROM BOTTOMING OUT. THESE SAME CHARACTERISTICS WILL LIKELY  
ALLOW FOR GOOD RADIATIONAL COOLING TONIGHT, SO FORECAST LOWS ARE  
ONCE AGAIN IN THE LOWER TO MIDDLE 20S F.  
 
FINALLY, THE STRATUS OVER SOUTH CENTRAL AND EASTERN ND EARLY THIS  
MORNING WILL POSE SOME CHALLENGE TO TODAY'S FORECAST. THE PRIMARY  
UNCERTAINTY WITH THIS STRATUS IS HOW FAR WEST IT WILL ULTIMATELY  
BE ABLE TO BUILD. MOST GUIDANCE SUGGESTS ONLY FRAGMENTS OF STRATUS  
WILL WORK INTO WESTERN ND BY MORNING, BUT WE WILL BE MONITORING  
LATER MODEL CYCLES AND SATELLITE TRENDS DURING THE NEXT FEW HOURS  
TO SEE HOW THIS PROGRESSES. RECENT GRIDDED LAMP CYCLES APPEAR TO  
BE CAPTURING THE EXTENT OF THE STRATUS WELL, SO WE RELIED ON THEM  
TO CONSTRUCT THE SKY FORECAST FOR TODAY. THAT GENERALLY MEANS WE  
EXPECT THE STRATUS TO DISSIPATE FROM WEST TO EAST DURING THE LATE  
MORNING AND EARLY AFTERNOON, LINGERING THE LONGEST (UNTIL LATE  
AFTERNOON OR EARLY EVENING) IN THE JAMES RIVER VALLEY.  
   
LONG TERM
 
(FRIDAY THROUGH WEDNESDAY)  
ISSUED AT 459 AM CDT THU APR 27 2017  
 
A WARMING TREND IS FORECAST DURING THE LONG TERM FORECAST PERIOD  
WITH HIGHS GENERALLY IN THE UPPER 50S AND LOWER 60S F FOR SATURDAY  
THROUGH WEDNESDAY PER THE 00 UTC MULTI-MODEL CONSENSUS. NORTHWEST  
FLOW IS FORECAST TO PREVAIL ALOFT AS A MEAN 500 MB TROUGH SHIFTS  
OUT OF THE WESTERN AND INTO THE CENTRAL U.S., WHICH SHOULD ALLOW  
FOR HEIGHTS AND THERMAL FIELDS TO RECOVER FROM THEIR LOW POINTS  
THIS WEEK. THE 00 UTC GLOBAL MODELS CONTINUE TO SUGGEST THAT A FEW  
SHORTWAVE TROUGHS EMBEDDED IN THE NORTHWEST FLOW MAY BRING SOME  
SHOWERS TO THE REGION FROM MONDAY THROUGH WEDNESDAY, TOO.  
 
THE MOST INTERESTING PART OF THE FORECAST IS THE POWERFUL UPPER-  
LEVEL LOW CONSISTENTLY BEING FORECAST BY THE LAST SEVERAL CYCLES  
OF THE GLOBAL DETERMINISTIC AND ENSEMBLE GUIDANCE TO LIFT FROM  
THE SOUTHERN PLAINS INTO THE UPPER MIDWEST EARLY NEXT WEEK. THIS  
LOW IS SIMULATED TO CONTAIN STRONG DYNAMIC FORCING AND LOW ENOUGH  
850 MB TEMPERATURES IN ITS COLD SECTOR TO POTENTIALLY YIELD A MAY  
HEAVY SNOW EVENT SOMEWHERE IN THE UPPER MIDWEST. THE SYSTEM IS  
FORECAST TO STAY SOUTHEAST OF THE LOCAL AREA, BUT THE 00 UTC ECMWF  
DID MAKE A SHIFT FURTHER NORTHWEST WITH ITS SIMULATED DEFORMATION  
BAND SUCH THAT TAKEN AT FACE VALUE ITS PRECIPITATION WOULD INDEED  
IMPACT THE EASTERN PART OF ND. THE ECMWF SIMULATION DID THAT AS A  
RESULT OF A DEEPER AND FASTER NORTHERN-STREAM SHORTWAVE THAT  
MOVES FAR ENOUGH EASTWARD BY MONDAY TO CREATE A WEAKNESS IN THE  
HEIGHT FIELDS OVER ND, WHICH THE STRONG MIDWESTERN CYCLONE THEN  
TAKES ADVANTAGE OF IN A REGIME MARKED BY STRONG DOWNSTREAM 500 MB  
RIDGING OFF THE EASTERN SEABOARD. THE AMPLITUDE AND PROGRESSION OF  
THAT NORTHERN-STREAM SHORTWAVE TROUGH WILL BE THE KEY ITEM TO  
WATCH IN THE COMING DAYS AS IT DOES AFFORD A NON-ZERO PROBABILITY  
OF THE FORCING AND RESULTANT PRECIPITATION FROM THE DEEP UPPER-  
LEVEL TROUGH EXTENDING FURTHER NORTHWEST.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)  
ISSUED AT 1219 PM CDT THU APR 27 2017  
 
VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE 18Z TAF PERIOD.  
 

 
   
BIS WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
UPDATE...JV  
SHORT TERM...CJS  
LONG TERM...CJS  
AVIATION...AC  
 
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