National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KFGF 200858
AFDFGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
358 AM CDT THU JUN 20 2013

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 330 AM CDT THU JUN 20 2013

MAIN CONCERN WILL BE SEVERE THUNDER AND HEAVY RAIN POTENTIAL THIS
AFTERNOON AND OVERNIGHT.

AREA OF THUNDERSTORMS CURRENTLY ONGOING ACROSS THE SOUTHERN FA
(AND BUILDING INTO THE WESTERN FA) WHERE WATER VAPOR IMAGERY
INDICATES AN UPPER WAVE AND THE RAP INDICATES 30-40 KNOT 850MB JET
INDUCED BY THIS UPPER WAVE. ANTICIPATE THIS ACTIVITY TO CONTINUE
INTO THE DAYLIGHT HOURS AND THEN DISSIPATE WITH SUBSIDENCE BEHIND
THE WAVE. SEVERE POTENTIAL IS VERY LOW CONSIDERING WEAK
INSTABILITY. THE MAIN THREAT WILL BE HEAVY RAIN WITH PWATS AROUND
1.5 INCHES AND SLOW STORM MOTIONS.

ANTICIPATE A BREAK IN THE ACTIVITY DURING THE MID-DAY HOURS WHICH
SHOULD ALLOW FOR SOME HEATING AND MOISTURE ADVECTION...WITH MLCAPE
VALUES AOA 2000 J/KG SOME AREAS. FORCING FOR REDEVELOPMENT SHOULD
COME WITH A POSSIBLE MCV FROM ACTIVITY TO THE WEST (ACROSS
NORTHERN MONTANA) AS WELL AS AN UPPER WAVE FROM THE SOUTHWEST THAT
SOME MODEL INDICATE. PREFER TO FOLLOW THE ECMWF FOR DEWPOINT
VALUES CONSIDERING LACK OF EVAPOTRANSPIRATION DUE TO LATE CROPS
THIS YEAR. THIS SOLUTION WOULD HAVE MLCAPE 2000-2500 J/KG INTO SE
NORTH DAKOTA BY 21Z...WITH DECREASING INSTABILITY TO THE NORTH
AND EAST (AND THE INSTABILITY AXIS INTO NORTH CENTRAL NORTH
DAKOTA). MOST LIKELY SCENARIO IS THAT THUNDER INITIATES ALONG THE
LOW LEVEL BOUNDARY/DRY LINE ACROSS CENTRAL NORTH DAKOTA...AND
EVENTUALLY BECOMES SOME SORT OF MCS THAT BUILDS INTO THE HIGHER
STABILITY (WHICH MOST LIKELY WILL BE TO THE SOUTH). THE MAIN
THREATS WILL LIKELY BE LARGE HAIL AND ESPECIALLY WIND GUSTS. A
TORNADO OR TWO IS ALSO POSSIBLE...ESPECIALLY INITIALLY. OTHER
MODELS ARE MORE ROBUST WITH DEWPOINTS VALUES (INTO THE LOW/MID
70S...AND WELL NORTH INTO THE FA)...WHICH LIKELY ACCOUNTS FOR THEM
WANTING TO MOVE THE MCS TO THE EAST INTO NORTHERN
MINNESOTA...OPPOSED TO THE ECMWF WHICH MOVES THIS FEATURE INTO
SOUTHERN MINNESOTA. HEAVY RAIN ALSO A THREAT WITH PWATS ABOVE 1.5
INCHES. NOT SURE EXACTLY WHERE THE HEAVIEST RAIN WILL OCCUR
TONIGHT...BUT A FLASH FLOOD WATCH MAY BE NEEDED ACROSS THE
SOUTHERN FA WHERE THE HEAVY RAIN IS CURRENTLY OCCURRING.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 330 AM CDT THU JUN 20 2013

FRIDAY-SATURDAY NIGHT...REGION WILL BE IN SOUTHWEST FLOW
ALOFT...AND CONVECTIVE CHANCES WILL HINGE ON TIMING OF SHORTWAVES
EJECTING FROM THE WESTERN TROUGH. FOLLOWING THE ECMWF FOR
TIMING...KEPT THE LIKELY POPS FOR FRIDAY EVENING INTO SATURDAY
MORNING...AND AGAIN FOR SATURDAY NIGHT. SEVERE STORMS AGAIN A
POSSIBILITY...AND DEPENDENT ON INSTABILITY VALUES. THE SOUTHERN FA
APPEARS TO HAVE THE BEST CHANCE FOR SEVERE STORMS. HEAVY RAIN ALSO
A POSSIBILITY...AND FUTURE SHIFTS MAY NEED TO CONSIDER FLOOD/FLASH
FLOOD WATCHES DEPENDING ON WHAT HAPPENS TODAY.

SUNDAY-WEDNESDAY...LONG WAVE TROUGH RE-ESTABLISHES FARTHER WEST
OVER THE EASTERN PACIFIC. A LONG WAVE RIDGE BUILDS OVER THE
CENTRAL US BY THE END OF THE PERIOD. GFS AND ECMWF ARE SIMILAR
TIMING WISE AT 84 HOURS BUT THE ECMWF BECOMES THE FASTER SOLUTION
FOR THE REST OF THE PERIOD. WILL USE A BLEND OF THE ECMWF AND GFS.

PRECIPITATION IS A LITTLE FASTER WITH TODAYS RUNS AND WILL BE SUED.

LITTLE CHANGE TO TEMPS THROUGH THE PERIOD COMPARED TO YESTERDAY
PACKAGE.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1125 PM CDT WED JUN 19 2013

THE CHANCES FOR SHOWERS AND THUNDERSTORMS WILL INCREASE FROM WEST
TO EAST OVERNIGHT AND THURSDAY. HAVE STARTED TO MENTION SOME
CONVECTION...ALTHOUGH TIMING REMAINS TOUGH. FOR NOW HAVE KEPT ALL
CIGS IN VFR CATEGORY...AND WILL CONTINUE TO REVISE FORECAST ONCE
TIMING AND AREAL COVERAGE BECOMES A BIT MORE CERTAIN.


&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...NONE.
MN...NONE.
&&

$$

SHORT TERM...TG
LONG TERM...TG/HOPPES
AVIATION...DK