000
FXUS63 KBIS 171138
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
638 AM CDT FRI MAY 17 2013

.UPDATE...
ISSUED AT 637 AM CDT FRI MAY 17 2013

UPDATE FOR MINOR CHANGES TO POPS ACROSS THE NORTH THIS MORNING AS
BATCH OF SHOWERS AND ISOLATED THUNDERSTORMS CONTINUES TO HEAD
NORTHEAST. OTHERWISE...MAINTAINED GENERALLY INCREASING POPS
THROUGH LATE AFTERNOON AND EVENING.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 349 AM CDT FRI MAY 17 2013

THE MAIN CONCERN FOR TODAY INTO TONIGHT WILL BE THE CHANCE OF
THUNDERSTORMS AND POTENTIAL SEVERE WEATHER. EARLY MORNING RADAR
MOSAIC SHOWED ISOLATED SHOWERS FROM SOUTHWEST NORTH DAKOTA INTO
NORTHWEST MINNESOTA. MUCH OF THIS ACTIVITY DEVELOPED IN AN AREA OF
H85 WARM AIR ADVECTION THAT HAS BEEN MOVING FROM SOUTH TO NORTH
ACROSS THE REGION. THE STRONGEST WARM AIR ADVECTION SHIFTS NORTH BY
AFTERNOON AS SOUTHWESTERLY FLOW ALOFT BRINGS A SERIES OF WAVES ACROSS
THE STATE. WILL MAINTAIN FAIRLY HIGH POPS TODAY...ESPECIALLY IN
THE NORTH AND WEST WHERE THE MAJORITY OF MODEL SOLUTIONS FAVOR THE
HIGHER PRECIPITATION CHANCES.

THE FOCUS THEN TURNS FARTHER SOUTH AS SURFACE LOW PRESSURE GATHERS
IN EAST CENTRAL WYOMING. A WARM FRONT STRETCHING OUT OF THE LOW
INTO SOUTHERN SOUTH DAKOTA IS EXPECTED TO LIFT NORTH TONIGHT...BRINGING
INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS TO CENTRAL AND
WESTERN NORTH DAKOTA. CAN NOT RULE OUT AN ISOLATED SEVERE STORM
LATE THIS AFTERNOON / EVENING ACROSS THE SOUTHERN PART OF THE
FORECAST AREA WHERE INSTABILITY WILL BE GREATEST. THE SPC DAY 1
SEVERE WEATHER OUTLOOK KEEPS THE SLIGHT RISK SOUTH OF THE FORECAST
AREA...HOWEVER THE 5 PERCENT PROBABILITIES FOR SEVERE HAIL / WIND
ARE DRAWN SOUTH OF I-94 INTO SOUTHERN NORTH DAKOTA WHICH APPEARS
REASONABLE.

TEMPERATURES TODAY WILL BE TRICKY DUE TO THE CLOUDS AND RAIN. WILL
GENERALLY STAY ON THE COOL SIDE OF GUIDANCE WHICH SUGGESTS MID
60S NORTH TO LOWER 70S SOUTH.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 349 AM CDT FRI MAY 17 2013

THE MAIN FORECAST ISSUES THROUGH THE LONG TERM PERIOD ARE CONVECTIVE
TRENDS...AND POTENTIAL FOR PROLONGED MODERATE TO HEAVY RAIN AND
SOME SEVERE WEATHER ON SATURDAY. THE LATEST 17/00Z MODEL RUNS HAVE
SOME SIGNIFICANT DIFFERENCE IN THE PROGRESSION OF A CLOSED UPPER
LOW THROUGH THE REGION THROUGH EARLY NEXT WEEK. THE NAM IS AMONG
THE FARTHEST WEST...WHILE THE GFS FAVORS A FASTER...MORE EASTERLY
PATH. THE ECMWF REPRESENTS A REASONABLE COMPROMISE...AND WOULD
KEEP SHOWERS AROUND INTO TUESDAY BEFORE PUSHING EAST. THE FAVORED
PERIOD FOR SEVERE WEATHER WILL BE SATURDAY...WITH SOUTHWEST FLOW
ALOFT AND A WARM FRONT NOSING INTO THE SOUTHEAST PORTION OF THE
FORECAST AREA. SPC CONTINUES TO HAVE THE SOUTHEAST OUTLOOKED IN
SLIGHT RISK FOR DAY 2. BUFR SOUNDINGS SUGGEST STORMS WILL DEVELOP
RELATIVELY EARLY IN THE DAY. AM EXPECTING SOME STRONG TO SEVERE
STORMS WITH LARGE HAIL/STRONG WIND GUSTS THE PRIMARY THREATS.
STRONG MOISTURE TRANSPORT INTO THE BOUNDARY WILL CONTINUE THROUGH
SATURDAY NIGHT AS A DECENT SHORT WAVE TROUGH MOVES THROUGH EASTERN
NORTH DAKOTA. THE SEVERE WEATHER THREAT DIMINISHES SUNDAY...BUT
MODERATE TO LOCALLY HEAVY RAIN IS EXPECTED TO CONTINUE OVER MUCH
OF WESTERN AND CENTRAL NORTH DAKOTA. THIS SCENARIO WILL LIKELY
CONTINUE MONDAY...BEFORE SHOWERS TAPER OFF IN COVERAGE AND
INTENSITY ON TUESDAY. TOTAL RAINFALL AMOUNTS OF 1 TO 3 ARE
EXPECTED THROUGH THE PERIOD...WITH AMOUNTS AROUND 4 INCHES
POSSIBLE...ESPECIALLY IN THE JAMES RIVER VALLEY. CONDITIONS ARE
SUCH THAT SOILS CAN ABSORB SIGNIFICANT RAINFALL. THUS...SIGNIFICANT
RISES ON MAIN STEM RIVERS SUCH AS THE SOURIS AND JAMES ARE NOT
EXPECTED. HOWEVER...ENHANCED RAINFALL RATES OR SEVERAL ROUNDS OF
STORMS COULD PRODUCE LOCALIZED RUNOFF...LEADING TO RISES ON SMALL
CREEKS AND STREAMS...AND POSSIBLY FLASH FLOODING.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 637 AM CDT FRI MAY 17 2013

SHOWERS AND ISOLATED THUNDERSTORMS MOVING NORTHEAST ACROSS WESTERN
NORTH DAKOTA COULD APPROACH KMOT DURING THE FIRST FEW HOURS OF THE
TAF.  THE REMAINDER OF THE TAF SITES SHOULD STAY DRY THIS
MORNING...THOUGH THE CHANCES OF SHOWERS AND A FEW THUNDERSTORMS WILL
INCREASE LATE THIS AFTERNOON INTO TONIGHT.

CEILINGS IN PARTICULAR ARE A CHALLENGE RIGHT FROM THE BEGINNING WITH
PARTS OF CENTRAL AND WESTERN NORTH DAKOTA ALREADY SHOWING LOCATIONS
WITH MVFR / IFR CONDITIONS.  KMOT BRIEFLY FELL TO IFR...WHILE KISN
AND KDIK ARE CURRENTLY MVFR.  FORECAST SOUNDINGS SUGGEST CEILINGS
SHOULD IMPROVE LATER THIS MORNING BEFORE THEY DECLINE AGAIN TONIGHT
IN THE RAIN.  GENERALLY STAYED MVFR WITH CEILINGS / VISIBILITIES IN
THE RAIN...BUT COULD SEE THOSE BEING DROPPED LOWER ONCE MORE
CONFIDENCE IN THE TIMING CAN BE ESTABLISHED.

&&

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

$$

UPDATE/LONG TERM...RP KINNEY
SHORT TERM/AVIATION...CK