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000
FXUS63 KBIS 200634
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
134 AM CDT MON MAY 20 2013

.UPDATE...

ISSUED AT 135 AM CDT MON MAY 20 2013

OVERALL CHANGES WITH THIS UPDATED FORECAST PACKAGE WERE MINIMAL
WITH THE INHERITED FORECAST ON TRACK. DID ADD THE MENTION OF
SCATTERED THUNDERSTORMS OVER MY SOUTHEAST WITH A FEW
CELLS/LIGHTNING STRIKES POPPING UP THE LAST HOUR OR SO OVER
SOUTHEASTERN NORTH DAKOTA MOVING WEST TOWARDS THE JAMES RIVER
VALLEY.

ALSO WILL ADD ADAMS AND HETTINGER COUNTIES IN SOUTHWEST NORTH
DAKOTA...AND MCLEAN AND MERCER COUNTIES IN CENTRAL NORTH DAKOTA TO
THE WIND ADVISORY...AND WILL EXPAND THE ADVISORY IN TIME TO 06Z
TUESDAY (1AM MONDAY NIGHT/EARLY TUESDAY MORNING). WINDS GUSTING TO
OVER 40 MPH NOW AT HETTINGER AND AT A FEW RAWS SITES IN WESTERN
MCLEAN COUNTY. WINDS WILL CONTINUE THROUGH MONDAY BEFORE STARTING
TO TAPER OFF MONDAY NIGHT.


UPDATE ISSUED AT 842 PM CDT SUN MAY 19 2013

LATEST SURFACE ANALYSIS SHOWS 3HR PRESSURE FALLS MAXIMIZED NEAR
MANDAN WITH LOW PRESSURE BETWEEN LINTON...MOBRIDGE...AND ASHLEY. THE
LOW WILL CONTINUE TO PROGRESS TOWARDS THE MAX PRESSURE FALLS
OVERNIGHT RESULTING IN A CONTINUED WESTBOUND RETROGRESSION. THE
PRESSURE GRADIENT CONTINUES TO REMAIN TIGHT IN THE WEST AND NORTH
AND HAVE DECIDED TO ADD ROLETTE...MCHENRY...AND PIERCE COUNTIES TO
THE CURRENT WIND ADVISORY...AS RAP BOUNDARY WINDS ARE FORECAST AROUND
30KT INTO EARLY MONDAY MORNING.

WATER VAPOR IMAGERY SHOWS THE MAIN UPPER LOW ESTABLISHING ITSELF
OVER CENTRAL NEBRASKA. THIS IS FORECAST TO MOVE INTO THE EASTERN
DAKOTAS MONDAY INTO TUESDAY. RADAR IMAGERY SHOWS STEADY LIGHT TO
MODERATE RAIN CONTINUES IN THE WEST AND NORTH...WITH A LULL
CONTINUING FOR THE MOST PART ACROSS THE JAMES RIVER BASIN. EXPECT
MORE SHOWERS TO PIVOT AROUND AFTER MIDNIGHT AS PREVIOUSLY
FORECAST.

PLEASE REFER TO THE UPDATED HYDROLOGY SECTION AT THE BOTTOM FOR EVENING
UPDATES.

ONLY OTHER CHANGE TO THE GRIDDED EVENING FORECAST WAS TO LOWER
POPS IN THE JAMES RIVER VALLEY THROUGH MIDNIGHT...THEN GRADUALLY
INCREASED THEM AS THE NEXT WAVE APPROACHES FROM NEBRASKA.

UPDATE ISSUED AT 545 PM CDT SUN MAY 19 2013

LATEST WATER VAPOR IMAGERY/SURFACE ANALYSIS ALONG WITH RAP/HRRR
MODEL DATA...SHOW MULTIPLE CIRCULATIONS AND RESULTANT PRECIPITATION
BANDS INTO WESTERN/CENTRAL NORTH DAKOTA...ALL EMANATING AROUND
THE MAIN UPPER LOW OVER CENTRAL NEBRASKA. THE LATEST RADAR
IMAGERY SHOWS ONE LARGE RAIN SHIELD PIVOTING ACROSS WESTERN NORTH
DAKOTA THIS EVENING...WITH SOMEWHAT OF A LULL IN SOUTHEASTERN
NORTH DAKOTA...FROM KBIS TO KJMS. HOWEVER...A SURFACE LOW NEAR ASHLEY
THIS EVENING WILL RETROGRADE WEST OVERNIGHT AS MAX PRESSURE FALLS
ARE OCCURRING OVER SOUTH CENTRAL NORTH DAKOTA. THIS WILL ALLOW FOR
ISOLATED SHOWERS AND A POSSIBLE THUNDERSTORM THIS EVENING IN THE
SOUTHEAST...BUT MORE LIKELY WILL HELP TO CIRCULATE MORE SHOWERS
INTO THE JAMES RIVER VALLEY AFTER MIDNIGHT...AND INTO SOUTH
CENTRAL NORTH DAKOTA BEFORE SUNRISE MONDAY. THE MAIN UPPER LOW IN
NEBRASKA WILL ROTATE INTO THE EASTERN DAKOTAS MONDAY INTO MONDAY
NIGHT...PROVIDING FOR MODERATE TO HEAVY RAINFALL...AS DISCUSSED
BELOW. LITTLE IF ANY CHANGE FROM THE PREVIOUS FORECAST DISCUSSION
IN THIS UPDATE.

THE WIND ADVISORY AND FLOOD WATCH WILL CONTINUE AS PREVIOUSLY
FORECAST...WITH A CLOSE METWATCH ON EVENING CONVECTIVE TRENDS IN
THE SOUTHERN JAMES RIVER VALLEY. LOCAL RIVERS/STREAMS WILL ALSO BE
MONITORED THROUGH THE NIGHT FOR ADDITIONAL UPDATES.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 330 PM CDT SUN MAY 19 2013

THE HIGHLIGHT OF THE SHORT TERM IS THE CONTINUED HEAVY RAINFALL
AND FLOODING THREAT ACROSS WESTERN AND CENTRAL NORTH DAKOTA
THROUGH MONDAY NIGHT AND A FLOOD WATCH REMAINS IN EFFECT.

OVERALL...THE DETERMINISTIC GUIDANCE IS IN GOOD AGREEMENT ON
RETROGRADING THE DEEP SURFACE LOW CURRENTLY ACROSS NORTHEAST SOUTH
DAKOTA WEST THROUGH TONIGHT...BEFORE PROPAGATING AGAIN EAST ON
MONDAY. GIVEN THE GOOD AGREEMENT...FOLLOWED A BLEND OF THE 12 UTC
GFS/GEM/ECMWF AND 15 UTC SREF FOR ALL FIELDS. THIS PLACES THE
LOW LEVEL DEFORMATION ZONE AND ASSOCIATED MODERATE TO HEAVY
RAINFALL GENERALLY ACROSS THE HIGHWAY 85 CORRIDOR AND INTO THE
NORTH CENTRAL THROUGH TONIGHT. WILL CONTINUE TO MONITOR THE JAMES
RIVER VALLEY LATE THIS AFTERNOON THROUGH EARLY EVENING AS BREAKS
IN THE CLOUD COVER IS ALLOWING SOME SURFACE BASED DESTABILIZATION
TO OCCUR. BEING SO CLOSE TO THE SURFACE LOW...DEEP LAYER SHEAR IS
MARGINAL FOR THIS PART OF THE CWA...HOWEVER...IT WOULD BE FAVORED
FOR A POSSIBLE WEAK SPIN- UP TORNADO/LAND SPOUT WITH THE LOW LEVEL
VORTICITY SHOULD SUFFICIENT NEAR SURFACE DESTABILIZATION OCCUR.
ALSO FOR TONIGHT...DID ISSUE WIND ADVISORY FOR WESTERN AND NORTH
CENTRAL NORTH DAKOTA FROM 00 UTC TO 15 UTC MONDAY. NAM/GFS BUFR
SOUNDINGS INDICATE 40-45 KTS TO MIX IN THE 900-875 MB LAYER AS THE
PRESSURE GRADIENT STRENGTHS WITH THE RETROGRADING SURFACE LOW.

FOR TOMORROW...AS ENERGY CURRENTLY ACROSS NEBRASKA PIVOTS AROUND
THE MAIN UPPER LEVEL LOW INTO NORTH DAKOTA...MODERATE TO HEAVY
RAIN WILL ONCE AGAIN BECOME WIDESPREAD ACROSS ALL OF WESTERN AND
CENTRAL NORTH DAKOTA. BY TUESDAY MORNING...AN ADDITIONAL TWO TO
THREE INCHES OF RAINFALL IS POSSIBLE FOR MUCH OF THE AREA. SEE THE
HYDROLOGY DISCUSSION BELOW FOR DETAILS.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 330 PM CDT SUN MAY 19 2013

THE MAIN FORECAST ISSUE THROUGH THE LONG TERM PERIOD IS CONTINUED
HEAVY RAIN AND POTENTIAL FOR FLOODING. THE LATEST SUITE OF 19/12Z
MODELS IS IN VERY GOOD AGREEMENT REGARDING THE TRACK OF THE CLOSED
UPPER LOW THROUGH THE REGION. THE UPPER LOW MONDAY NIGHT IS FORECAST
TO BE OVER THE EASTERN DAKOTAS/WESTERN MINNESOTA BORDER...AND MOVE
SOUTHEASTWARD GRADUALLY TO SOUTHERN MINNESOTA BY DAYBREAK WEDNESDAY
MORNING...THEN MOVE EASTWARD INTO THE OHIO VALLEY AS ANOTHER UPPER
LEVEL LOW MAKES ITS WAY INTO THE WEST COAST. THIS CONSENSUS
INDICATES A PROLONGED PERIOD OF MODERATE TO HEAVY RAIN CONTINUING
MONDAY NIGHT INTO TUESDAY...IMPACTING MOST IF NOT ALL OF WESTERN AND
CENTRAL NORTH DAKOTA. SHOWERS ARE EXPECTED TO BECOME MORE SCATTERED
TUESDAY NIGHT INTO WEDNESDAY. RAINFALL AMOUNTS IN THE 24-HOUR PERIOD
FROM MONDAY NIGHT THROUGH TUESDAY NIGHT ARE EXPECTED TO RANGE FROM
AROUND 1/3 TO 2/3 OF AN INCH OVER A LARGE AREA OF WESTERN AND
CENTRAL NORTH DAKOTA. THIS IN ADDITION TO WHAT HAS ALREADY BEEN
RECEIVED THROUGH THIS WEEKEND...AND WHAT IS FORECAST FOR SUNDAY
NIGHT AND MONDAY...WILL KEEP FLOODING ISSUES THE MAIN THREAT ACROSS
THE REGION. IN ADDITION TO FLOODING CONCERNS ALONG SMALL
STREAMS...AND LOW LYING AREAS...WILL BE MONITORING RIVERS CLOSELY
THIS WEEK...ESPECIALLY THE FASTER RESPONDING POINTS SUCH AS APPLE
CREEK NEAR MENOKEN.

IN ADDITION TO THE RAINS...GUSTY WINDS ARE EXPECTED TO CONTINUE
MONDAY NIGHT THROUGH TUESDAY NIGHT...AS THE INTENSE UPPER LEVEL LOW
IS STACKED OVER THE SURFACE LOW...AND NORTHERLY WINDS FROM THE
SURFACE THROUGH H700 REMAIN UNIDIRECTIONAL FROM THE NORTH. EXPECTING
20 TO 30 MPH SUSTAINED WINDS WITH GUSTS TO NEAR 35 MPH AT TIMES.

UPPER LEVEL RIDGING WILL BECOME ESTABLISHED OVER THE REGION
BEGINNING WEDNESDAY AFTERNOON...AHEAD OF THE NEXT LARGE LOW PRESSURE
SYSTEM OVER THE WEST COAST/ROCKIES. THIS SYSTEM IS EXPECTED TO
REMAIN OVER THE ROCKIES AND BEGIN TO SET UP A SOUTHWESTERLY FLOW
ALOFT OVER THE NORTHERN PLAINS BY FRIDAY.

THE NEXT BEST CHANCE OF RAIN SHOWERS AND THUNDERSTORMS IS
FRIDAY...AND CONTINUING THROUGH THE WEEKEND.

EXPECT COOL WEATHER CONDITIONS TUESDAY WITH HIGHS IN THE
50S...WARMING GRADUALLY TO THE UPPER 60S AND 70S BY SATURDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)

ISSUED AT 135 AM CDT MON MAY 20 2013

MODERATE TO HEAVY RAINFALL WILL CONTINUE THROUGH THE TAF PERIOD
WITH MVFR/IFR CIGS/VSBYS. KISN/KDIK/KMOT AERODROMES WILL
EXPERIENCE THE CONDITIONS MENTIONED ABOVE THROUGH MONDAY.
KBIS/KJMS WILL SEE A RESPITE IN THE PRECIPITATION THIS SUNDAY
NIGHT WITH MORE RAIN DEVELOPING AFTER 06Z AT KJMS AND THEN SPREAD
WEST TO KBIS BY 10-12Z MONDAY. THEREAFTER...MODERATE TO HEAVY
RAINFALL WILL COMMENCE AT KBIS AND KJMS. A THUNDERSTORM THIS EARLY
MONDAY MORNING REMAINS POSSIBLE AS WELL FOR KJMS.

&&

.HYDROLOGY...
ISSUED AT 842 PM CDT SUN MAY 19 2013

TWO MAIN CONCERNS THIS EVENING...HAVE COORDINATED WITH THE
MISSOURI BASIN RIVER FORECAST CENTER/MBRFC THIS EVENING...AND WILL
DO THE FOLLOWING...

1) APPLE CREEK AT MENOKEN HAS NOT RESPONDED TO THE RAPID RISE
THAT WAS FORECAST TO OCCUR ALREADY. THIS HAS BEEN DELAYED UNTIL
LATER TONIGHT. WITH THE RIVER FORECAST TO REMAIN JUST A HARE BELOW
MINOR FLOOD STAGE...WILL ISSUE AN RVS THIS EVENING WITH LATER
SHIFTS RE-EVALUATING...ESPECIALLY WITH MONDAYS RAINFALL.

2) WILL ISSUE A FLOOD WARNING FOR THE LITTLE MUDDY CREEK NEAR
WILLISTON. BELIEVE WE CAN ADD SOME VALUE/LEAD TIME HERE WITH
PROJECTIONS MAINTAINING A STEADY RISE WELL INTO MINOR FLOOD STAGE
BY LATE MONDAY NIGHT AND TUESDAY. WITH ADDITIONAL RAINS COMING
MONDAY...HAVE A HIGH DEGREE OF CONFIDENCE THAT CURRENT RISING
TRENDS WILL CONTINUE.

3) A FEW MORE RIVER FORECAST POINTS ARE FORECAST TO REACH MINOR
FLOOD STAGE IN THE COMING DAYS...BUT ENOUGH TIME REMAINS TO
MONITOR RAINFALL AMOUNTS MONDAY AND TUESDAY. WILL HOLD OFF ON
ISSUING ANY OTHER PRODUCTS PER COORDINATION WITH MBRFC...AND WILL
BRIEF THE ONCOMING SHIFT OF THESE DECISIONS.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH THROUGH TUESDAY MORNING FOR NDZ001>005-009>013-
017>023-025-031>037-040>048-050-051.

WIND ADVISORY UNTIL 1 AM CDT /MIDNIGHT MDT/ TUESDAY FOR
NDZ001>005-009>013-017>019-021-031>033-040-041-043-044.

&&

$$

UPDATE...NH
SHORT TERM...AYD
LONG TERM...JV
AVIATION...NH
HYDROLOGY...KS/AYD