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000
FXUS63 KBIS 250626
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
126 AM CDT SAT MAY 25 2013

.UPDATE...
ISSUED AT 125 AM CDT SAT MAY 25 2013

BASED ON CURRENT TRENDS AND NAM12 MODEL FORECAST HAVE DECIDED TO
KEEP THE FORECAST DRY INTO SATURDAY FOR ABOUT 3 HOURS LONGER THAN
PREVIOUS FORECAST. HAVE ALSO REMOVED ALL POPS FOR SATURDAY
AFTERNOON IN THE EASTERN THIRD OF THE FORECAST AREA. NAM12
INDICATES THAT CONVECTION SOUTHWEST NORTH DAKOTA WILL SPREAD INTO
THE CENTRAL AND WEAKEN / DECAY AS IT MOVES INTO LESS UNSTABLE
AIR...NEVER MAKING IT INTO THE EAST UNTIL SATURDAY EVENING.

WILL KEEP THE RISK OF SEVERE WORDING / GRIDS FOR THE SOUTHWEST.

PATCHY FOG NORTHEAST FORECAST AREA OVERNIGHT WITH THE RISK OF IT
FORMING FARTHER WEST TOWARD DAYBREAK. NO CHANGES TO TEMPERATURES
OR WIND FORECAST.

UPDATE ISSUED AT 1002 PM CDT FRI MAY 24 2013

PATCHY FOG FORMING ACROSS THE NORTHEAST IN GOOD LOW LEVEL MOISTURE
WITH SOUTHEAST FLOW. ADDED PATCHY FOG AND DRIZZLE THERE TONIGHT.
OTHERWISE REMOVED ALL MENTION OF THUNDERSTORMS AND SHOWERS FROM
THE EAST. DRY ALSO WEST.

UPDATE ISSUED AT 657 PM CDT FRI MAY 24 2013

CANCELED THE WIND ADVISORY SOUTH CENTRAL AS WINDS HAVE NOW
DIMINISHED. SHOWERS HAVE MOVED A LITTLE MORE RAPIDLY EAST AND
CLEARED THE SHOWERS FROM CENTRAL NORTH DAKOTA...AND LEFT A SLIGHT
CHANCE OF A THUNDERSHOWER FAR EAST FOR A FEW MORE HOURS THIS
EVENING. CONCERNED ABOUT A LITTLE PATCH OF INSTABILITY SOUTHWEST
FAR SOUTH CENTRAL. THIS SHOWS UP AS CONVECTIVE LOOKING CLOUDS ON
VISIBLE SATELLITE BETWEEN DICKINSON AND BISMARCK. KEPT A SLIGHT
CHANCE OF A THUNDERSTORM THERE FOR THE EVENING. THEN DRY AFTER
MIDNIGHT. SATURDAY...ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS
MOVING IN FROM WEST TO EAST.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 334 PM CDT FRI MAY 24 2013

MAIN FORECAST CONCERN IN THE SHORT TERM PERIOD WILL BE
THUNDERSTORM CHANCES ON SATURDAY AFTERNOON.

CURRENTLY...SCATTERED SHOWERS ARE MOVING THROUGH FAR EASTERN
PORTIONS OF CENTRAL NORTH DAKOTA. AHEAD OF A SURFACE TROUGH MOVING
INTO THE WESTERN DAKOTAS. MESOSCALE MODELS HAVE BEEN HINTING AT AN
AREA OF DEVELOPMENT OVER THE SOUTHWEST/SOUTH CENTRAL LATER THIS
AFTERNOON INTO EARLY THIS EVENING IN AXIS OF MOISTURE/INSTABILITY.
WILL THEREFORE KEEP A SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM
OVER THE SOUTHWEST AND SOUTH CENTRAL THIS EVENING...MAINLY EAST OF
A LINE FROM DICKINSON TO HETTINGER. CURRENT DEW POINTS IN THE MIDDLE
50S FROM HETTINGER TO DICKINSON WITH LOW TO MID 40 DEW POINTS
MOVING INTO THE FAR WEST. WITH GUSTY WINDS CONTINUING OVER
CENTRAL NORTH DAKOTA WILL KEEP THE WIND ADVISORY IN PLACE THROUGH
7 PM. EVENING SHIFT MAY BE ABLE TO CANCEL IT EARLY.

THE SURFACE TROUGH IN THE WEST WASHES OUT TONIGHT AND WINDS BECOME
SOUTHEAST ACROSS ALL OF WESTERN AND CENTRAL NORTH DAKOTA AS THE
TROUGH BECOMES RE-ESTABLISHED OVER EASTERN MONTANA AHEAD OF THE
UPPER LEVEL LOW OVER THE NORTHWEST U.S. THIS WILL ALLOW LOW LEVEL
MOISTURE TO CONTINUE TO POOL OVER THE ENTIRE FORECAST AREA
OVERNIGHT AND INTO SATURDAY.

BY SATURDAY AFTERNOON...MODERATE INSTABILITY DEVELOPS OVER WESTERN
NORTH DAKOTA AND EASTERN MONTANA. A SOUTHEAST SURFACE FLOW SHIFTS
SOUTHWEST IN THE MID LEVELS AHEAD OF THE UPPER LEVEL TROUGH. THIS
WILL ALLOW FOR MID 50S TO UPPER 50 DEW POINTS TO ADVECTING INTO
SOUTHWEST NORTH DAKOTA WITH AROUND 40 KNOTS OF BULK SHEAR AND CAPE
VALUES AROUND 1000-1500 J/KG IN EASTERN MONTANA INTO SOUTHWEST
NORTH DAKOTA. PREVIOUS SHIFT HAD A MENTION OF SEVERE STORMS IN
THE WESTERN THIRD SATURDAY AFTERNOON AND SEE NO REASON TO CHANGE
THIS.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 334 PM CDT FRI MAY 24 2013

THE MAIN FORECAST ISSUE THROUGH THE LONG TERM PERIOD WILL BE
CONVECTIVE TRENDS...AND POTENTIAL FOR SEVERAL ROUNDS OF HEAVY
RAIN/SEVERE WEATHER. THE SEVERE WEATHER THREAT IS EXPECTED TO
CONTINUE SOUTHWEST INTO SATURDAY NIGHT AS A COMPACT SHORT WAVE
TROUGH INTERACTS WITH MODERATE INSTABILITY (ML CAPES AROUND 1000
J/KG) AND MOISTURE (DEWPOINTS UPPER 50S/AROUND 60). MOST MODELS ARE
ALSO HIGHLIGHTING POTENTIAL FOR AN MCS SATURDAY NIGHT INTO SUNDAY
MORNING...ACROSS THE NORTHWEST PORTION OF THE FORECAST AREA. THERE
IS STILL CONSIDERABLE UNCERTAINTY ABOUT THIS SCENARIO...BUT WILL BE
WATCHING CLOSELY AS HEAVY RAIN COULD IMPACT THE UPPER SOURIS BASIN
AND ASSOCIATED CANADIAN RESERVOIRS.

PERSISTENT SOUTHWEST FLOW ALOFT WILL CONTINUE SUNDAY INTO NEXT
WEEK...BEFORE A LARGE CLOSED LOW IS FORECAST TO MOVE INTO THE REGION
THURSDAY INTO FRIDAY. EXPECT SEVERAL ADDITIONAL ROUNDS OF HEAVY
RAIN/POTENTIAL SEVERE WEATHER THROUGH THE PERIOD. THE LATEST HPC QPF
THROUGH NEXT FRIDAY PROJECTS WIDESPREAD 1 TO 3 INCHES AMOUNTS ACROSS
THE FORECAST AREA...HEAVIEST IN WESTERN NORTH DAKOTA. THE WARMEST
DAYS WILL LIKELY BE TUES/WED...WITH HIGHS MOST LOCATIONS IN THE 70S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 125 AM CDT FRI MAY 24 2013

KMOT IS ON THE EDGE WITH MVFR CLOUDS JUST EAST. SATELLITE SHOWS NO
PROGRESS BACK WEST...TOWARD KMOT...SO LEFT THEM OUT OF PRIMARY TAF
SECTION. VFR CONDITIONS EXPECTED AT THE REST OF TAF SITES (KISN...
KDIK...KBIS...KJMS). PATCHY FOG EAST OF KMOT AND NORTH OF KJMS
COULD DEVELOP INTO THOSE TAF SITES TOWARD DAYBREAK. SCATTERED
THUNDERSTORMS IN VICINITY KISN-KDIK AFTER 15Z.

&&

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

$$

UPDATE...JPM
LONG TERM...RP KINNEY
AVIATION...JPM