Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 222021
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
321 PM CDT FRI AUG 22 2014

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 321 PM CDT FRI AUG 22 2014

THE MAIN FORECAST ISSUE IN THE SHORT TERM PERIOD IS THE POTENTIAL
FOR FLOODING. THE DETERMINISTIC MODELS ARE COMING INTO BETTER
AGREEMENT WITH THE EVOLUTION OF A STRONG UPPER LEVEL LOW PRESSURE
SYSTEM MOVING ACROSS THE NORTHERN ROCKIES THROUGH SATURDAY THEN
LIFTING INTO THE NORTHERN PLAINS SATURDAY NIGHT INTO SUNDAY.

THERE HAS BEEN A GOOD CONSENSUS REGARDING A PRECIPITATION MAX OVER
EASTERN MONTANA. MODELS HAVE DIFFERED IN A SECOND MAX ACROSS THE
NORTHERN PLAINS. THE GFS/ECMWF/GEM WERE FARTHER EAST WITH A
SECONDARY MAX... WHILE THE NAM HAS BEEN MORE CONSISTENT WITH
BRINGING A SWATH OF HIGHER QPF ACROSS MUCH OF THE CWA. MODELS ARE
NOW MORE IN LINE WITH THE SECONDARY MAX LIFTING NORTH THROUGH
CENTRAL NORTH DAKOTA...WITH TWO DAY QPF GREATER THAN 1 INCH ACROSS
A MAJORITY OF THE CWA...AND A MAX OF OVER 2 INCHES OVER THE NORTH
CENTRAL...ENDING SUNDAY AFTERNOON.

TYPICALLY A BIG RAIN EVENT LIKE THIS IN AUGUST MIGHT NOT CAUSE TOO
MUCH OF A PROBLEM. HOWEVER...WITH OUR CURRENT SOIL MOISTURE
CONDITIONS GIVEN RECENT HEAVY RAINS...THE THREAT OF EXCESSIVE RAIN
INCREASES. WITH MANY AREA NEAR SATURATED OR SATURATED...WILL ISSUE
A FLOOD WATCH FOR MOST OF WESTERN AND CENTRAL NORTH DAKOTA. SEE
THE SEPARATE FLOOD DISCUSSION BELOW FOR ADDITIONAL DETAILS.



.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 321 PM CDT FRI AUG 22 2014

BY SUNDAY EVENING THE MODELS ARE DEPICTING AN UPPER LEVEL LOW OVER
EASTERN MONTANA/NORTHERN NORTH DAKOTA...WITH THE LOW LIFTING
NORTHEASTWARD INTO MANITOBA BY DAYBREAK MONDAY MORNING. MEANWHILE AN
UPPER LEVEL TROUGH REMAINS OVER THE ROCKIES. THIS TROUGH MOVES
EASTWARD ACROSS MONTANA MONDAY AND MONDAY NIGHT...AND ACROSS THE
DAKOTAS ON TUESDAY/TUESDAY NIGHT.

THUS ON SUNDAY NIGHT...THE LINGERING SHOWERS SHOULD BE MAINLY
CONFINED TO THE NORTHERN COUNTIES. SMALL CHANCES OF SHOWERS CAN BE
EXPECTED MONDAY AND TUESDAY AS THE WESTERN LONGWAVE TROUGH MOVES
THROUGH THE REGION.

WEDNESDAY UPPER LEVEL RIDGING TAKES PLACE...KEEPING THE FORECAST
AREA MAINLY DRY MID-WEEK THROUGH THE END OF THE WEEK.

REGARDING TEMPERATURES...COOLER THAN AVERAGE WITH HIGHS IN THE 60S
MONDAY AND TUESDAY...WARMING TO THE 70S WEDNESDAY...AND UPPER 70S
AND LOWER 80S BY THURSDAY/FRIDAY. LOWS IN THE 40S TO LOWER 50S
SUNDAY NIGHT AND MONDAY NIGHT...WITH LOWS IN THE 50S THROUGH NEXT
WEEK.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 321 PM CDT FRI AUG 22 2014

MVFR CONDITIONS SHOULD IMPROVE TO VFR DURING THE AFTERNOON...BUT
THEN DETERIORATE BY 06Z TO MVFR/IFR IN CIGS AND VSBYS. AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS POSSIBLE AND VCSH OR VCTS IN TAFS.
LATER THIS EVENING EXPECTING SHOWERS AND THUNDERSTORMS TO DEVELOP
SOUTHWEST AND SPREAD NORTH AND EAST OVERNIGHT. INCREASING CHANCES OF
PRECIPITATION. MOST OF SATURDAY AFTER 12Z SHOULD BE MVFR WITH RAIN
SHOWERS AND SOME EMBEDDED THUNDERSTORMS.

&&

.HYDROLOGY...
ISSUED AT 321 PM CDT FRI AUG 22 2014

GOING INTO THE COMING WEEKEND...THERE IS NO AREA OF THE CWA WHERE
LOCALIZED FLOODING CAN BE RULED OUT. MODERATE TO HEAVY RAINS OVER
THE PAST WEEK HAVE KEPT SOIL MOISTURE ABNORMALLY HIGH ACROSS THE
CWA. HEAVY RAINS ARE LIKELY TO OVERWHELM THE CURRENT INFILTRATION
RATES OF THE SOIL AND LEAD TO OVERLAND FLOODING AND CREATE A GREATER
THAN NORMAL RUNOFF. THIS ENHANCED RUNOFF RATES WILL ENCOUNTER
ALREADY WELL ABOVE NORMAL FLOW IN NEARLY EVERY SIGNIFICANT SMALL
STREAM AND RIVER IN THE AREA. WHILE THERE IS NO REASONABLE
EXPECTATION OF MAJOR RIVER FLOODING...AT A MINIMUM THERE WILL BE
SIGNIFICANT WITHIN BANK RISES...AND MINOR RIVER FLOODING CANNOT BE
RULED OUT.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH FROM 1 AM CDT /MIDNIGHT MDT/ SATURDAY THROUGH SUNDAY
AFTERNOON FOR NDZ017>020-031>034-040>046-050.

FLOOD WATCH FROM SATURDAY MORNING THROUGH SUNDAY AFTERNOON FOR
NDZ001>005-009>013-021>023-035-036-047.

&&

$$

SHORT TERM...TWH
LONG TERM...JV
AVIATION...JV
HYDROLOGY...TWH






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