000
FXUS63 KBIS 042014
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
310 PM CDT FRI JUL 4 2008
.SHORT TERM...TODAY THROUGH MONDAY NIGHT...
MAIN FORECAST CONCERN IS THE CHANGE OF THUNDERSTORMS TOMORROW AND
AGAIN LAST SUNDAY NIGHT INTO TUESDAY.
STRONG RIDGING CURRENTLY PLACE OVER THE NORTHERN PLAINS IS BEING
PUSHED EASTWARD DUE TO WAVE BEING KICKED OUT OF THE TROUGH OVER THE
PACIFIC NORTHWEST. THIS WAVE WILL MOVE A SURFACE LOW IN CANADA AND
ITS ASSOCIATED COOL FRONT EASTWARD TODAY THROUGH CENTRAL MONTANA.
THE FRONT IS EXPECTED TO BE ON OUR DOOR STEP BY 12Z SATURDAY
MORNING. NOT MUCH OF A TEMPERATURE CHANGE IS EXPECTED BEHIND THE
FRONT AS TEMPERATURES WILL BE IN THE LOWER TO MID 90S AHEAD IT AND
THE UPPER 80S TO LOWER 90S BEHIND IT. EXPECT THUNDERSTORMS TO BE ON
GOING AS THE FRONT APPROACHES WESTERN NORTH DAKOTA WHERE CAPE VALUES
WILL BE IN THE 500 TO 1000 J/KG RANGE AND LIFTED INDICES IN THE -1
TO -2 RANGE.
THE STORM PREDICTION CENTER PLACES CENTRAL NORTH DAKOTA UNDER SLIGHT
RISK FOR SEVERE THUNDERSTORMS DURING THE AFTERNOON AND EVENING
HOURS. EXPECT THE COOL FRONT TO REACH CENTRAL NORTH DAKOTA AROUND
18Z SATURDAY AND INTO EASTERN PORTIONS OF THE STATE BY 00Z. MODELS
INDICATE A MODERATELY UNSTABLE ATMOSPHERE AHEAD OF THE FRONT IN
CENTRAL NORTH DAKOTA WITH CAPE VALUES NEAR 2000J/KG AND LI`S NEAR -6
AND EXTREMELY UNSTABLE AIR OVER SOUTHEASTERN PORTIONS OF THE STATE.
THIS MODERATELY UNSTABLE ATMOSPHERE ALONG WITH BULK SHEAR VALUES OF
20 TO 25 KTS WILL SUPPORT THE DEVELOPMENT OF SEVERE THUNDERSTORMS
DURING THE AFTERNOON AND EVENING HOURS ACROSS THE AREA. EXPECT THE
MAIN SEVERE THREAT TO BE DAMAGING WINDS AND LARGE HAIL.
A TRANSITION FROM A HIGH AMPLITUDE PATTERN TO A MORE ZONAL FLOW WILL
OCCUR ON SUNDAY. WEAK RIDGING WILL TAKE OVER SUNDAY BUT ENOUGH
INSTABILITY WILL BE IN PLACE DURING THE AFTERNOON AND EVEN HOURS
THAT A FEW THUNDERSTORMS CAN`T BE RULED OUT. ANOTHER COLD FRONT WILL
MOVE THROUGH THE STATE LATE SUNDAY NIGHT INTO MONDAY BRINGING MORE
WIDESPREAD SHOWERS AND THUNDERSTORMS.
.LONG TERM......TUESDAY THROUGH FRIDAY NIGHT...
BOTH GFS AND ECMWF DEPICT AN UPPER LEVEL LOW OVER SOUTH CENTRAL
CANADA ON TUESDAY...THEN ANOTHER SHORTWAVE MOVING THROUGH WEDNESDAY
NIGHT/THURSDAY. MODELS DIVERGE AFTER THAT. KEPT SLIGHT CHANCE IN
EASTERN COUNTIES TUESDAY/TUESDAY NIGHT AND INTRODUCED SMALL CHANCES
WEDNESDAY NIGHT AND THURSDAY. REGARDING TEMPERATURES...HIGHS IN THE
UPPER 70S TO UPPER 80S AND LOWS 55 TO 65.
&&
.AVIATION...LOW DEVELOPING IN CENTRAL MONTANA AND WESTERN WYOMING
WITH SOUTH SOUTHERLY WINDS OVER THE DAKOTAS. THE LOW WILL DEEPEN AND
SOUTH WINDS WILL BRING HIGHER DEWPOINTS AND MUCH WARMER AIR IN LOWER
AND MID LEVELS...ESSENTIALLY BUILDING A THERMAL CAP OVER NORTH
DAKOTA. CLEAR SKIES EXPECTED ALL TAF SITES UNTIL AN UPPER LEVEL
SHORTWAVE ALONG AND BEHIND A SURFACE TROUGH/FRONT ENTERS WESTERN
NORTH DAKOTA BY 09Z-12Z SATURDAY MORNING. LINGERING SHOWERS/THUNDER
FROM TONIGHT`S CONVECTION IN MONTANA EXPECTED TO MOVE INTO WESTERN
NORTH DAKOTA BEFORE DAYBREAK. BY MID-LATE AFTERNOON EXPECT CAP TO
BREAK WITH MAXIMUM SURFACE HEATING AND UPPER LEVEL SHORTWAVE TO
DISTURB CAP AND THUNDERSTORMS TO ERUPT WELL AFTER 18Z OVER
CENTRAL/EASTERN NORTH DAKOTA TAF SITES.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DC/HW/JV
