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000
FXUS63 KBIS 170018
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
718 PM CDT THU MAY 16 2013

.UPDATE...
ISSUED AT 718 PM CDT THU MAY 16 2013

REGIONAL RADAR TRENDS INDICATE NUMEROUS SHOWERS ACROSS THE JAMES
RIVER BASIN CONTINUING TO PUSH EAST OF THE CWA THIS EVENING. WITH
THE ATMOSPHERE PRETTY WELL WORKED OVER...DECREASED POPS WEST AND
CENTRAL THROUGH THE REMAINDER OF THE EVENING HOURS.

HOWEVER...SHORT RANGE MODEL GUIDANCE CONTINUES TO PROG INCREASING PRECIP
CHANCES AFTER MIDNIGHT AS AN UPPER WAVE APPROACHES FROM THE
SOUTHWEST. SHOWALTER INDICES INDICATE THUNDER POTENTIAL DEVELOPING
ACROSS SOUTHWESTERN NORTH DAKOTA AFTER MIDNIGHT. AS A
RESULT...REMOVED THUNDER AREAWIDE TONIGHT AND ONLY INDICATED
ISOLATED THUNDER SOUTHWEST DEVELOPING AFTER MIDNIGHT.

UPDATED THE HOURLY SENSIBLE WEATHER GRIDS BASED ON CURRENT
OBS/TRENDS. THE UPDATED GRIDDED AND TEXT PRODUCTS HAVE BEEN SENT.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 300 PM CDT THU MAY 16 2013

LATEST WATER VAPOR IMAGERY SHOWS A SOUTHWEST FLOW INTO NORTH DAKOTA
AHEAD OF AN UPPER TROUGH WHICH IS SLIDING INTO THE NORTHWEST COAST.
FOR THE NEAR TERM...THROUGH THURSDAY EVENING...CATEGORICAL POPS
WILL CONTINUE FROM BALTA TO MCCLUSKY INTO BISMARCK AND AREAS TO
THE EAST AS A SHORTWAVE PROPAGATES THROUGH. THERE IS A BREAK IN
THE CLOUDS AND PRECIPITATION IN THE FAR WEST WITH MORE SHORTWAVES
MOVING INTO CENTRAL MONTANA. THESE WILL MOVE THROUGH TONIGHT INTO
FRIDAY GENERATING ISOLATED TO SCATTERED SHOWERS. BEST CHANCE FOR
AN ISOLATED THUNDERSTORM WILL RESIDE IN THE WEST AND SOUTH INTO
TONIGHT. LATEST VISIBLE IMAGERY SHOWS SOME CLEARING IN THE WEST
WITH CLOUDS BEGINNING TO BILLOW UP IN NORTHEAST MONTANA. FOR
FRIDAY...SOME INSTABILITY CONTINUES IN THE SOUTHWEST AND FAR SOUTH
CENTRAL FOR A MENTION OF THUNDERSTORMS...OTHERWISE SCATTERED
SHOWERS WILL GENERALLY BE THE RULE.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 300 PM CDT THU MAY 16 2013

A BROADENING UPPER LEVEL LOW POSITIONED OVER THE WESTERN CONUS EARLY
THE EXTENDED WILL ALLOW FOR MOIST SOUTHWESTERLY FLOW TO CONTINUE
ACROSS THE NORTHERN PLAINS SATURDAY INTO SUNDAY. AS THIS BROAD UPPER
LEVEL TROUGH SLOWLY SHIFTS EAST AND OVER THE REGION LATE SUNDAY AND
EARLY MONDAY THE FLOW WILL BECOME SOUTHERLY AS THE UPPER LEVEL
TROUGH CLOSES OFF OVER THE DAKOTAS. IT WILL REMAIN OVERHEAD MONDAY
AND TUESDAY BEFORE MOVING EAST THEREAFTER. 12Z GFS/GEM/NAM/ECWMF ARE
IN GOOD AGREEMENT REGARDING THIS PATTERN...BEFORE SOLUTIONS DIVERGE
LATE IN THE EXTENDED AS THE UPPER LEVEL LOW MOVES EAST.

THE MAIN ISSUE FOR THE EXTENDED WILL BE THE POTENTIAL FOR HEAVY RAIN
THROUGH EARLY NEXT WEEK. THERE IS DECENT AGREEMENT BETWEEN THE 12Z
MODEL RUNS REGARDING THE PLACEMENT AND AMOUNT OF PRECIPITATION
ACROSS THE AREA...WITH THE HEAVIEST AMOUNTS FOCUSED ON THE JAMES
RIVER VALLEY AND POINTS EAST. A SECOND AREA OF HEAVY PRECIPITATION
MAY BE POSSIBLE ACROSS THE NORTHWEST. HOWEVER...THERE IS A BIT
MORE UNCERTAINITY FOR THE NORTHWEST AREA. IN ADDITION...THE 12Z
GFS AND NAM CONTINUE TO PLACE PRECIPITABLE WATER VALUES OF 1.30 TO
1.50 INCHES ACROSS THE EASTERN TWO THIRDS OF NORTH DAKOTA SATURDAY
THROUGH EARLY SUNDAY MORNING. ACCORDING TO PW CLIMATOLOGY...THESE
FORECAST VALUES WILL BE IN THE 99TH PERCENTILE TO THE HIGHEST EVER
OBSERVED FOR THE MONTH OF MAY. CONFIDENCE IS INCREASING FOR 1 TO 2
INCHES (WITH LOCALLY HIGHER AMOUNTS ACROSS THE JAMES RIVER VALLEY)
OF RAINFALL THROUGH SUNDAY EVENING. ADDITIONAL LIGHT TO MODERATE
RAIN WILL CONTINUE THROUGH TUESDAY AS THE UPPER LEVEL LOW IS
OVERHEAD...BRINGING POTENTIAL RAINFALL TOTALS THROUGH TUESDAY INTO
THE 2 TO 4 INCH RANGE. THIS WILL HAVE TO BE MONITORED CLOSELY OVER
THE NEXT FEW DAYS AS POTENTIAL HYDRO ISSUES FOR THE JAMES RIVER
MAY COME INTO PLAY. ALSO...THIS HEAVY RAIN EVENT WILL POTENTIALLY
ALLEVIATE THE RAINFALL DEFICITS OBSERVED SO FAR FOR MAY.

REGARDING THE POTENTIAL FOR SEVERE WEATHER...THE BEST CHANCES FOR
ANY SEVERE WEATHER WILL COME SATURDAY AFTERNOON THROUGH EARLY SUNDAY
MORNING FOR LOCATIONS EAST OF STATE HIGHWAY 83 AND SOUTH OF
INTERSTATE 94. ISOLATED SEVERE MAY BE POSSIBLE FOR THE SOUTHWEST
LATE SATURDAY AFTERNOON AND EARLY EVENING. SUFFICIENT MOISTURE
WILL BE PRESENT DUE TO PREVIOUS MOISTURE RECEIVED ON THURSDAY AND
FRIDAY. BULK SHEAR VALUES WILL BE IN THE 40 TO 50 KT RANGE DURING
THIS PERIOD...WITH ML CAPE IN THE 1000 TO 2000 J/KG RANGE FOR THE
FAR SOUTH CENTRAL...AND 2000 TO 3000 J/LG VALUES ACROSS THE
SOUTHERN JAMES RIVER VALLEY. MU CAPE VALUES WILL BE IN THE 1200 TO
3000 J/KG RANGE AS WELL. HOWEVER...THE MAIN LIMITING FACTOR WILL
BE THE WARM AIR ALOFT...AS THE NAM/GFS BUFR SOUNDINGS FOR JMS/BIS
DEPICT A DECENT CAP INVERSION. THIS MAY BE OVERCOME BY DAYTIME
HEATING AND LARGE SCALE ASCENT ASSOCIATED WITH THE AFOREMENTIONED
UPPER LEVEL TROUGH.

BEYOND TUESDAY...THE UPPER LEVEL LOW WILL MOVE EAST AND IN ITS
WAKE...UPPER LEVEL RIDING WILL COMMENCE. A PERIOD OF DRIER AND
SEASONABLE TEMPERATURES ARE FORECAST FOR WEDNESDAY AND THURSDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 24Z FRIDAY EVENING)
ISSUED AT 718 PM CDT THU MAY 16 2013

MVFR CIGS ACROSS SOUTHWESTERN NORTH DAKOTA WILL GRADAULLY SPREAD
NORTHEAST OVER THE STATE TONIGHT. IFR CIGS ARE EXPECTED TO DEVELOP
OVER KDIK AROUND MIDNIGHT...THEN IMPROVE TO MVFR MIDDAY FRIDAY.

AN UNSETTLED WEATHER PATTERN WILL GENERATE CHANCES FOR SHOWERS AND
POSSIBLE THUNDERSTORMS PRIMARILY AFTER SUNRISE FRIDAY. THE THREAT
FOR SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH THE REMAINDER
OF THE TAF PERIOD.

&&

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

&&

$$

UPDATE...TM
SHORT TERM...KS
LONG TERM...LTH
AVIATION...TM