Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 192027
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
327 PM CDT TUE AUG 19 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)

ISSUED AT 327 PM CDT TUE AUG 19 2014

THE MAIN CONCERN IN THE SHORT TERM FORECAST PERIOD IS EXPECTED
WIDESPREAD SHOWERS AND THUNDERSTORMS WEDNESDAY AND WEDNESDAY NIGHT.
THE PROBLEM IS LOW CONFIDENCE ON WHERE THE HEAVIEST RAINFALL TOTALS
CAN BE EXPECTED.

CURRENTLY...SURFACE LOW PRESSURE WAS OVER SOUTHWESTERN SASKATCHEWAN
AND NORTH CENTRAL MONTANA AHEAD OF AN UPPER LEVEL LOW/TROUGH OVER
UTAH. SURFACE DEWPOINTS WERE IN THE MID 50S WEST AND IN THE 60S OVER
EASTERN NORTH DAKOTA.

TONIGHT THE UPPER LOW LIFTS NORTHEASTWARD AND APPROACHES
SOUTHWESTERN NORTH DAKOTA. IN RESPONSE...THE SURFACE LOW/TROUGH
SHOULD DEVELOP EASTWARD SO THAT BY DAYBREAK WEDNESDAY IT IS ALONG
THE MONTANA/DAKOTAS BORDER. SOME MODELS ARE DEPICTING SOME ISOLATED
SHOWERS/THUNDER BEFORE DAYBREAK IN THE WEST...AND HAVE KEPT
ISOLATED/SMALL CHANCE PROBABILITIES FOR THE WESTERN QUARTER OF THE
STATE THROUGH DAYBREAK.

MODELS ARE IN GOOD AGREEMENT THAT SHORTLY AFTER/AT DAYBREAK THE
UPPER LEVEL ENERGY IMPULSES WILL BE SUFFICIENT FOR INCREASING
CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH THE DAYLIGHT MORNING
HOURS. AROUND/AFTER NOON SHOWERS AND THUNDERSTORMS SHOULD BE
WIDESPREAD AND NUMEROUS ACROSS WESTERN AND CENTRAL NORTH DAKOTA.
WEDNESDAY EVENING MOST OF THE PRECIPITATION FROM THE THUNDERSTORMS
SHOULD BE IMPACTING ALL BUT THE FAR WESTERN PORTION OF NORTH
DAKOTA...WITH DECREASING CHANCES FROM WEST TO EAST LATE WEDNESDAY
NIGHT.

THE MAIN PROBLEM IS THAT THE VARIOUS MODELS ARE NOT COMING TO A GOOD
CONSENSUS REGARDING PLACEMENT OF THE HEAVIEST PRECIPITATION. THE NAM
MODEL IS FARTHEST NORTH WITH THE PLACEMENT OF HEAVY
PRECIPITATION...WITH WESTERN AND NORTH CENTRAL NORTH DAKOTA (SOURIS
RIVER BASIN) TAKING THE BIGGEST HIT. THE GFS/ECMWF WANT TO SPLIT THE
ENERGY - AND HENCE RESULTING IN TWO HEAVIER PRECIP BULLSEYES - WITH
ONE OVER THE SOURIS BASIN...AND ANOTHER OVER CENTRAL NORTH DAKOTA.
THE OTHER SHORT TERM HIGH RESOLUTION MODELS ARE FAVORING SOUTH
CENTRAL NORTH DAKOTA.

FINAL PRECIPITATION FORECAST INVOLVES A SECTION OF SOUTH CENTRAL
NORTH DAKOTA INCLUDING THE JAMES RIVER VALLEY OF 1 TO 1.5 INCHES OF
RAIN...AND AROUND 0.75 TO 1 INCH OVER THE NORTHWEST/NORTH CENTRAL.

A HYDROLOGIC OUTLOOK (ESF) HAS BEEN ISSUED TO ADDRESS THIS FIRST
WAVE OF PRECIPITATION WEDNESDAY THROUGH WEDNESDAY NIGHT...THEN ALSO
ADDRESSES THE LONG TERM PERIOD EXPECTED PRECIPITATION THURSDAY NIGHT
THROUGH THE WEEKEND.


.LONG TERM...(THURSDAY THROUGH TUESDAY)

ISSUED AT 327 PM CDT TUE AUG 19 2014

A VERY ACTIVE/WET PATTERN THROUGH THE WEEKEND WILL HIGHLIGHT THE
EXTENDED FORECAST PERIOD.

WILL NOTE 12Z MODELS STILL SHOW CONSIDERABLE SPREAD IN REGARDS TO
PRECIPITATION...TIMING/PLACEMENT/AMOUNTS...FRIDAY NIGHT THROUGH
SUNDAY. BETTER AGREEMENT THURSDAY THROUGH FRIDAY.

FOR THURSDAY...SHOWERS/THUNDERSTORMS WILL BE IN THE PROCESS OF
LIFTING OFF TO OUR NORTHEAST DURING THE MORNING AS A MID LEVEL S/WV
IMPULSE EJECTS INTO CANADA AND ITS ASSOCIATED SFC TROUGH PUSHES EAST
INTO THE UPPER MISSISSIPPI VALLEY. CONVECTIVE REDEVELOPMENT WILL BE
VERY POSSIBLE THURSDAY AFTERNOON/EVENING AS WE REMAIN IN
SOUTHWESTERLY FLOW ALOFT ALONG WITH AMPLE INSTABILITY AND DECREASING
CIN AS THE DAY PROGRESSES.

MAIN AREA OF PRECIPITATION WILL ENTER WESTERN NORTH DAKOTA THURSDAY
NIGHT AS ANOTHER EMBEDDED WAVE LIFTS NORTHEAST ACROSS EASTERN
MONTANA INTO FAR SOUTH CENTRAL CANADA...ALONG WITH FORCING
ASSOCIATED WITH THE UPPER LEVEL JET NOSING INTO THE REGION RESULTING
IN DIVERGENCE ALOFT OVERSPREADING THE NORTHERN PLAINS. BASED ON THE
PROJECTED TRACK OF THE MID LEVEL S/WV DEPICTED BY BOTH THE 12Z
GFS/ECMWF...MOST FAVORABLE AREAS FOR HEAVY PRECIPITATION WILL BE
OVER THE WESTERN HALF OF THE STATE AND INTO THE NORTH CENTRAL THURS
NIGHT-FRIDAY MORNING.

UPPER LEVEL TROUGH DIGS ACROSS THE WESTERN CONUS
FRIDAY-SATURDAY...THEN LIFTS NORTH AND EAST ACROSS THE DAKOTAS SAT
NIGHT-SUN NIGHT. MODEL SPREADS RATHER HIGH IN REGARDS TO
PRECIPITATION DURING THE FRIDAY/SATURDAY TIMEFRAME...WITH LEAD S/WV
IMPULSES DIFFICULT FOR MODELS TO KEY IN ON AT THIS TIME. SOME
LOCATION DIFFERENCES AS WELL SAT NIGHT INTO SUNDAY WITH THE TRACK OF
THE MAIN UPPER LEVEL WAVE WHEN IT MOVES ACROSS THE LOCAL REGION.
LOOKS TO BE WET MOST LOCATIONS.

WE REMAIN IN A QUASI-ACTIVE FLOW PATTERN INTO EARLY NEXT WEEK AS
WELL WITH A BROAD TROUGH IN PLACE ALOFT MONDAY AND TUESDAY.

TEMPERATURES WILL COOL SIGNIFICANTLY FROM FRIDAY INTO SUNDAY WITH
THE PRECIPITATION EXPECTED AND STRONG CAA ON SUNDAY IN THE WAKE OF A
STRONG SURFACE LOW AND UNDERNEATH THE UPPER WAVE. HIGHS SUNDAY WILL
BE IN THE 60S COMPARED TO UPPER 70S AND MID 80S ON THURSDAY. A
SLIGHT MODERATION IN HIGHS FORECAST NEXT WEEK MONDAY AND
TUESDAY.


&&


.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)

ISSUED AT 1241 PM CDT TUE AUG 19 2014

VFR CONDITIONS ARE EXPECTED AT ALL TAF SITES. ISOLATED THUNDERSTORMS
ARE POSSIBLE AFTER 06Z AT KISN/KDIK...BUT ADDED MENTION OF VCTS
AFTER 12Z WEDNESDAY WHEN CONFIDENCE IS HIGHER FOR THUNDERSTORM
DEVELOPMENT.


&&

.HYDROLOGY...

ISSUED AT 327 PM CDT TUE AUG 19 2014

THERE WILL BE POTENTIALLY SIGNIFICANT RAINS ACROSS MUCH OF WESTERN
AND CENTRAL NORTH DAKOTA FROM WEDNESDAY MORNING THROUGH EARLY
THURSDAY...AND THEN AGAIN THURSDAY NIGHT THROUGH SUNDAY. THOSE AREAS
OF THE STATE WHICH RECEIVE MULTIPLE PASSES OF HEAVY RAINS OF HEAVY
RAIN WILL LIKELY EXPERIENCE EXCESSIVE RUNOFF AND A HIGHER LIKELIHOOD
OF OVERLAND AND SMALL STREAM FLOODING.

WHILE THE SOURIS RIVER BASIN OF NORTH DAKOTA HAS BEEN RELATIVELY DRY
TO NEAR NORMAL THE PAST FEW WEEKS...SOME OF THE MODELS DEPICT
WIDESPREAD RAINS BETWEEN TWO AND FOUR INCHES ACROSS THE UPPER
PORTIONS OF THE SOURIS IN NORTH DAKOTA AND SASKATCHEWAN. AREAS THAT
RECEIVE AN INITIAL WETTING DURING THE EARLIER EVENT ARE MORE LIKELY
TO EXPERIENCE EXCESSIVE RUNOFF DURING THE LATTER RAINS. SEVERAL
MISSOURI RIVER TRIBUTARIES WERE PARTICULARLY HARD HIT BY HEAVY RAINS
LAST WEEKEND, INCLUDING THE KNIFE AND HEART RIVERS ALONG WITH APPLE
CREEK. THESE RIVERS WILL STILL BE RUNNING WELL ABOVE NORMAL AS THE
NEXT FEW WEATHER SYSTEMS MOVE INTO THE STATE.

THE JAMES AND PIPESTEM CREEK BASINS HAVE NOT BEEN PARTICULARLY
AFFECTED BY RECENT HEAVY RAINS. HOWEVER...THERE HAS BEEN ENOUGH RAIN
TO KEEP THE SOIL MOISTURE LEVELS AT OR ABOVE NORMAL FOR THIS TIME OF
YEAR.


&&

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

&&

$$

SHORT TERM...JV
LONG TERM...NH
AVIATION...JV
HYDROLOGY...AJS








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