861 
FXUS63 KBIS 270008
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
708 PM CDT SUN MAY 26 2013

.UPDATE...
ISSUED AT 658 PM CDT SUN MAY 26 2013

UPDATE MAINLY TO REFINE POPS OVERNIGHT...KEEPING THE HIGHER POPS
CONFINED MAINLY TO THE WEST AND EVENTUALLY THE CENTRAL COUNTIES
LATE. RADAR/VISIBLE SATELLITE IMAGERY INDICATING SOME SHOWERS AND
ENHANCED CUMULUS DEVELOPING AROUND HETTINGER AND MOTT. ML CAPES IN
THAT AREA ARE AROUND 1500 J/KG...ALTHOUGH DEEP LAYER SHEAR IS
RELATIVELY WEAK. STRONG TO SEVERE STORMS ARE CURRENTLY LOCATED WELL
WEST OF THE FORECAST AREA IN MONTANA AND WYOMING. SHORT WAVE
ENERGY IS EXPECTED TO MOVE INTO THE SOUTHWEST THIS EVENING...AND
THE 22Z RUN OF THE HRRR BRINGS STORMS INTO THE SOUTHWEST BETWEEN
02Z-03Z. NOT ANTICIPATING WIDESPREAD SIGNIFICANT SEVERE
WEATHER...BUT WILL LIKELY HAVE A FEW STRONGER STORMS TO MONITOR
LATER ON.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)

ISSUED AT 320 PM CDT SUN MAY 26 2013

FORECAST PROBLEM IN THE SHORT TERM WILL BE THUNDERSTORM CHANCES
THROUGH THE PERIOD. OVERALL MODEL TREND HAS BEEN TO LESSEN OR PUSH
BACK PRECIPITATION CHANCES ESPECIALLY LATE THIS AFTERNOON AND THIS
EVENING. BEYOND THIS THERE IS LITTLE FORECAST CONFIDENCE REGARDING
PRECIPITATION TIMING AND PLACEMENT AS MODELS ARE HAVING A HARD TIME
RESOLVING THIS IN THE BROAD SOUTHWEST UPPER FLOW.

CURRENTLY...MVFR-IFR STRATUS REMAIN ACROSS THE SOURIS TO JAMES
RIVER BASINS...WHILE STRATUS HAS DISSIPATED BUT WELL DEVELOPED CU
FIELD HAS BROKEN OUT OVER THE WEST AND SOUTH CENTRAL. THIS HAS
RESULTED IN TEMPERATURES PUSHING INTO THE LOW TO MID 70S WITH MID
50S DEWPOINT TEMPERATURES FROM WESTERN NORTH DAKOTA INTO EASTERN
MONTANA AND NORTHWEST SOUTH DAKOTA. CURRENT SPC ANALYSIS IS
SHOWING CAPES OF 1000-1500 J/KG WITH DIMINISHING CIHN OVER THE
MONDAK REGION WITH INCREASING LAPSE RATES. CONVECTION HAS RECENTLY
INITIATED OVER THE BIGHORNS AND BLACK HILLS. GGW 18Z SOUNDING AND
CURRENT LAPS SOUNDING NEAR KOLF INDICATE A NEAR COMPLETE ERODED
CAP OVER EASTERN MONTANA. LATEST WATER VAPOR SATELLITE IMAGERY
SHOW AN APPROACHING SHORTWAVE TROUGH LIFTING NORTHEAST THROUGH
WYOMING WHICH SHOULD HELP TO INITIATE CONVECTION AWAY FROM THE
MOUNTAINS. WITH THIS SAID...MODELS ARE NOT POINTING TO STRONG
CONVECTION OVER WESTERN AND CENTRAL NORTH DAKOTA THIS AFTERNOON
AND EARLY EVENING. GFS/ECMWF BRING BEST CHANCES INTO THE FAR WEST
LATE TONIGHT WITH CONVECTION CONTINUING EAST ACROSS THE AREA ON
MONDAY. 12 UTC NAM AND 17 UTC HRRR BRING CONVECTION FIRING OFF THE
BIGHORNS INTO SOUTHEAST MONTANA BUT THEN SUPPRESS REFLECTIVITIES
AS THEY MOVE INTO WESTERN NORTH DAKOTA. 12 UTC HIRES ARW/NMM EAST
BOTH POINT MORE TOWARD LATE NIGHT CONVECTION MOVING INTO THE WEST
AND LINGERING INTO MONDAY...WITH YET ANOTHER ROUND OF CONVECTION
ON MONDAY.

FOR NOW WILL LEAN TOWARD SLIGHT CHANCE POPS EAST TO CHANCE POPS
WEST THIS EVENING...THEN INCREASING AFTER MIDNIGHT WITH HIGHEST
POPS REMAINING IN THE WEST. THEN BASICALLY A BROAD BRUSH OF HIGH
CHANCE POPS ON MONDAY DUE TO SO MUCH UNCERTAINTY ON
TIMING/PLACEMENT. WITH AFOREMENTIONED SEVERE WEATHER INGREDIENTS
WILL KEEP A MENTION OF SEVERE LATE THIS AFTERNOON AND THIS
EVENING. IF CONVECTION WOULD DEVELOP AND MOVE INTO WESTERN NORTH
DAKOTA...THE GREATEST THREAT WOULD LIKELY BE LARGE HAIL AND VERY
HEAVY RAIN CAUSING LOCALIZED FLOODING PROBLEMS. 

ALTHOUGH SPC SLIGHT RISK DOES INCLUDE A PORTION OF THE FAR
SOUTHWEST ON MONDAY...WILL HOLD OFF ON MENTIONING THIS IN THE
FORECAST FOR NOW. WILL LET LATER SHIFTS RE-EVALUATE.

MODELS DO INDICATE INCREASING 925MB MOISTURE TONIGHT. CONSIDERED
ADDING A MENTION OF FOG...BUT THINK THE BIGGEST ISSUE WILL BE LOW
STRATUS AND LIFR CEILINGS. COULD SEE SOME MVFR VISIBILITIES BUT
WILL HOLD OFF ON ADDING FOG FOR NOW.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)

ISSUED AT 320 PM CDT SUN MAY 26 2013

A VERY ACTIVE WEATHER PATTERN WILL PERSIST ACROSS THE NORTHERN 
PLAINS THROUGH MUCH IF NOT ALL OF THE EXTENDED PERIOD.

LONG WAVE TROUGH WEST AND RIDGING EAST WILL MAINTAIN SOUTHWESTERLY 
FLOW ALOFT ACROSS THE DAKOTAS MONDAY NIGHT. SHOWERS AND POSSIBLY 
SEVERE THUNDERSTORMS WILL BE ONGOING AT THE START OF THE PERIOD 
MONDAY EVENING AS A STRONG S/WV LIFTS NORTHEAST THROUGH THE REGION. 
SCALED BACK PRECIPITATION CHANCES TUESDAY/TUESDAY EVENING AS A S/WV 
RIDGE ADVANCES NORTHEAST THROUGH THE STATE ALONG WITH DRIER AIR INTO 
MY WEST. SHOWER/THUNDERSTORM CHANCES INCREASE TUESDAY NIGHT AS THE 
RIDGE CONTINUES OFF TO OUR NORTH AND EAST RESULTING IN FLOW ALOFT 
TRANSITIONING TO SOUTHWEST ONCE AGAIN...WITH A LEAD IMPULSE MOVING 
NORTH THROUGH THE WESTERN DAKOTAS. 

BY WEDNESDAY MORNING THE BASE OF THE WESTERN CONUS TROUGH WILL BE 
OVER THE SOUTHERN ROCKIES...WHICH IS DEPICTED BY BOTH THE 12Z 
GFS/ECMWF TO SWING NORTH THROUGH THE CENTRAL PLAINS INTO THE DAKOTAS 
WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. FOR THURSDAY...THE BASE OF 
THE TROUGH MORPHS INTO A CUTOFF LOW WHICH MAY LINGER ACROSS THE 
NORTHERN PLAINS INTO SATURDAY IF THE 12Z ECMWF VERIFIES. THE 12Z GFS 
IS MORE PROGRESSIVE...WITH THE LOW BECOMING AN OPEN WAVE AND MOVING 
OVER THE WESTERN GREAT LAKES REGION BY SATURDAY MORNING. BOTH MODEL 
SOLUTIONS RESULT IN HIGH CHANCES FOR SHOWERS AND THUNDERSTORMS 
WEDNESDAY-WEDNESDAY NIGHT-THURSDAY...WITH A CHANCE OF STRONG TO 
SEVERE STORMS AS WELL. FORECAST UNCERTAINTY INCREASES AFTERWARDS FOR 
FRIDAY THROUGH THE WEEKEND WITH THE ABOVE MENTIONED DIFFERENCES 
BETWEEN THE GFS/ECMWF.       

TEMPERATURES WILL AVERAGE NEAR TO SLIGHTLY ABOVE NORMAL EARLY NEXT 
WEEK...THEN WILL AVERAGE NEAR TO SLIGHTLY BELOW NORMAL FOR THE END 
OF THE WORK WEEK THROUGH NEXT WEEKEND. 

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 658 PM CDT SUN MAY 26 2013

SOUTHEAST FLOW WILL CONTINUE THROUGH THE FORECAST PERIOD. THIS WILL 
KEEP A THREAT OF MVFR-IFR CEILINGS IN THE FORECAST AT ALL TAF SITES. 
THE PRESENCE OF ABUNDANT LOW LEVEL MOISTURE TONIGHT WILL ALLOW FOR 
LOWERED CEILINGS DOWN TO IFR-LIFR IN STRATUS AROUND 06-10Z AT ALL 
SITES...WITH SOME MVFR FOG. BROUGHT A MENTION OF LIGHT RAIN FOR ALL 
SITES EXCEPT FOR KJMS AFTER 18 UTC..WHERE VCSH WAS MORE APPROPRIATE 
SINCE THREAT FOR RAIN WILL BE LATER THERE. 

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...RP KINNEY
SHORT TERM...TWH 
LONG TERM...NH 
AVIATION...LTH