000
FXUS63 KBIS 161155
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
655 AM CDT THU MAY 16 2013

.UPDATE...
ISSUED AT 654 AM CDT THU MAY 16 2013

UPDATE TO REFINE POPS FOR MORNING RADAR TRENDS...OTHERWISE
PREVIOUS FORECAST IN GOOD SHAPE.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 352 AM CDT THU MAY 16 2013

MAIN CONCERN THIS SHORT TERM PERIOD WILL BE THE CHANCE OF SHOWERS
AND THUNDERSTORMS.

CURRENTLY...SURFACE HIGH PRESSURE WAS OVER MANITOBA WITH LOW
PRESSURE OVER WYOMING. AT UPPER LEVELS...THE LEADING EDGE OF A
SERIES OF SHORTWAVE ENERGY IMPULSES WAS MOVING INTO SOUTHWESTERN
NORTH DAKOTA FROM THE WEST.

THE MODELS INDICATE THAT H850 WINDS SHOULD BE INCREASING FROM A
SOUTHEASTERLY DIRECTION ACROSS WESTERN SOUTH DAKOTA INTO THE
SOUTHWEST CORNER OF NORTH DAKOTA. MEANWHILE SOUTHWESTERLY WINDS AT
H700 AND FINALLY WESTERLY WINDS AROUND H500 WERE SETTING UP AN
OVERRUNNING PRECIPITATION SCENARIO THIS MORNING. THE STRONGER H850
WINDS WERE EVIDENT IN THAT A LINE OF ELEVATED CONVECTION SEEN ON
REGIONAL RADARS EXTENDED FROM NEAR BEACH TO BEULAH. THESE HIGH-BASED
SHOWERS AND ISOLATED THUNDERSHOWERS WERE MOVING EASTWARD WITH THE
UPPER LEVEL WIND FIELD.

THE MODELS ARE IN GOOD AGREEMENT IN BRINGING IN GOOD MOISTURE...WITH
INCREASING LOW LEVEL DEWPOINTS AS WELL AS H850 AND H700 MOISTURE
FIELDS...WITH OVERRUNNING PRECIPITATION CONTINUING INTO TONIGHT.
INSTABILITY IS MARGINAL AS BEST CAPE VALUES OF 200-400 J/KG REMAIN
ACROSS THE SOUTHWEST TODAY AND ACROSS THE WEST AND SOUTH TONIGHT.
THUS KEPT THE MENTION OF RAIN SHOWERS WITH ISOLATED THUNDERSTORMS
MAINLY SOUTH AND WEST DURING THE DAY TODAY AND EXPANDED THE MENTION
OF THUNDER A BIT NORTH AND EAST TONIGHT. WENT WITH HIGHS IN TE 60S
MOST AREAS IN THE WEST AND PARTS OF CENTRAL NORTH DAKOTA WITH FAIRLY
WIDESPREAD RAIN SHOWERS. THE RAIN AND BETTER MOISTURE WILL KEEP THE
FIRE DANGER IN THE LOW TO MEDIUM TODAY.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 352 AM CDT THU MAY 16 2013

THE MAIN FORECAST ISSUES THROUGH THE LONG TERM PERIOD ARE CONVECTIVE
TRENDS...AND POTENTIAL FOR HEAVY RAIN AND SOME SEVERE WEATHER.
SOUTHWEST FLOW WILL TRANSPORT ABUNDANT MOISTURE INTO THE NORTHERN
PLAINS FRIDAY AND SATURDAY. HAVE INCREASED POPS BOTH DAYS. THE FAR
SOUTHWEST IS STILL OUTLOOKED IN THE SPC 5 PERCENT RISK
AREA...COINCIDENT WITH THE MAIN INSTABILITY AXIS. SIGNIFICANT WARM
AIR ALOFT SHOULD LIMIT THE COVERAGE OF SEVERE STORMS. SPC HAS ALSO
INCLUDED THE FAR SOUTH/SOUTHEAST IN SLIGHT RISK FOR SATURDAY...NEAR
THE SURFACE BOUNDARY. PRECIPITABLE WATER VALUES AROUND 1.5 INCHES
ARE EXPECTED...AND THE GFS IS SUGGESTING SB CAPE AROUND 2000 J/KG.
WIDESPREAD 1 TO 2 INCH RAINFALL AMOUNTS ARE EXPECTED THROUGH
SATURDAY NIGHT. THE FAR SOUTHEAST IS NOT OUT OF THE WOODS CONCERNING
SEVERE WEATHER POTENTIAL SUNDAY. A LARGE UPPER LOW WILL MOVE INTO
THE REGION SUNDAY AND MONDAY...BRINGING ADDITIONAL MODERATE TO
LOCALLY HEAVY RAIN...WHICH WILL LIKELY LINGER THROUGH AT LEAST
TUESDAY. TOTAL RAINFALL AMOUNTS THROUGH THE ENTIRE PERIOD COULD
REACH 3 TO 4 INCHES OVER MUCH OF WESTERN AND CENTRAL NORTH DAKOTA.
RENEWED HYDRO CONCERNS ARE LIKELY...ESPECIALLY IN THE SOURIS AND
JAMES RIVER BASINS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 654 AM CDT THU MAY 16 2013

SURFACE HIGH OVER MANITOBA AND SURFACE LOW WAS OVER WYOMING. WINDS
WERE GENERALLY LIGHT AND VARIABLE OVER NORTH DAKOTA BETWEEN THESE
TWO SURFACE PRESSURE SYSTEMS. LATER THIS MORNING AS THE LOW DEVELOPS
FARTHER EAST...WINDS SHOULD BECOME EAST/SOUTHEAST AT TAF SITES.
ELEVATED CONVECTION...WITH CLOUD BASES AT AROUND 8000 FEET...WAS
OCCURRING OVER SOUTHWEST AND SOUTH CENTRAL NORTH DAKOTA - NEAR KDIK
AND KBIS. EXPECT CONVECTION TO BECOME MORE WIDESPREAD DURING THE
MORNING AND CONTINUE SPREADING NORTH AND EAST ACROSS THE STATE.
SHOWERS MORE LIKELY AT KDIK AFT 15Z AND AT KBIS AND KISN AFT 18Z.
AFTER 00Z CONVECTION MORE LIKELY AT NORTHERN TAF SITES KISN/KMOT.

&&

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

$$

UPDATE/LONG TERM...RP KINNEY
AVIATION...JV