Severe Thunderstorm Warning 55, NWS Bismarck, ND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
346 PM CDT FRI MAY 28 2010

.SYNOPSIS...SURFACE LOW PRESSURE IN WESTERN NORTH DAKOTA EXTENDING
SOUTHWEST INTO CENTRAL ROCKIES. STATIONARY FRONT EXTENDS EAST
THROUGH NORTH DAKOTA LOW TO BETWEEN FARGO AND GRAND FORKS...AND
EXTENDING SOUTHWEST TO CENTRAL ROCKIES UTAH LOW. DRY LINE IN
CENTRAL HIGH PLAINS. VERY MOIST AIR MASS IN PLACE OVER SOUTH
CENTRAL AND SOUTHWEST NORTH DAKOTA WITH DEW POINTS APPROACHING 70
F.

&&

.SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...
BROAD WESTERN TROUGH WITH STRONG RIDGING OVER NORTHERN PLAINS.
VERY MOIST CAPPED ATMOSPHERE OVER WESTERN AND CENTRAL NORTH DAKOTA
WAITING FOR LIFT AND COOLING ALOFT FROM SHORTWAVE CURRENTLY
LIFTING FROM NEVADA/UTAH INTO WESTERN MONTANA.

CONVECTION LOOKS TO START THIS EVENING ALONG FRONTAL ZONE OVER
HIGHER TERRAIN AND MOVE NORTHEAST INTO VERY MOIST BOUNDARY LAYER.
MUCAPES ON SPC MESOANALYSIS SHOW AROUND 5K JOULES. WRF 4KM/NAM/
AND ECMWF SHOW THIS CONVECTION MOVING THROUGH NORTHWEST TO NORTH
CENTRAL NORTH DAKOTA OVERNIGHT WITH CONVECTION BEGINNING AGAIN
TOMORROW AFTERNOON OVER EASTERN PORTIONS OF FORECAST AREA.

MID LEVEL LOW MOVES NORTH OF INTERNATIONAL BORDER ON SUNDAY WITH
COMMA HEAD PRECIPITATION WELL NORTH AND ALSO WELL EAST ALONG MORE
PROGRESSIVE FRONTAL ZONE THAN PAST SEVERAL DAYS. MID LEVEL LOW
OPENS AND MOVES EAST MONDAY WITH SURFACE HIGH PRESSURE BUILDING
OVER NORTHERN PLAINS. RIDGING BUILDS OVER CANADIAN ROCKIES
NEGATIVELY TILTED SOUTH THROUGH CENTRAL PLAINS WITH ZONAL TO
NORTHWEST FLOW OVER FORECAST AREA.

.LONG TERM...TUESDAY THROUGH FRIDAY...
LONG TERM MODELS REMAIN IN GOOD AGREEMENT WITH THE OVERALL
PATTERN. A BROAD/DIRTY RIDGE MOVES THROUGH NORTH DAKOTA TUESDAY. A
LEADING SHORTWAVE EJECTING FROM AN SHORTWAVE TROUGH IN THE INTER
MOUNTAIN WEST PASSES THROUGH. THIS COULD GENERATE A
SHOWER/THUNDERSTORM OVER WESTERN AND PORTIONS OF SOUTH CENTRAL
NORTH DAKOTA AND HENCE HAVE MAINTAINED A SLIGHT CHANCE IN THE
GRIDS. TUESDAY NIGHT THROUGH WEDNESDAY EVENING THE AFOREMENTIONED
INTER MOUNTAIN WEST TROUGH MOVES THROUGH NORTH DAKOTA WHICH BRINGS
A BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS TO WESTERN AND
CENTRAL NORTH DAKOTA. BROAD RIDGING THEN DEVELOPS AGAIN THURSDAY.
ANOTHER SHORTWAVE LOOKS TO MOVE THROUGH THE RIDGE FRIDAY AND
FRIDAY NIGHT. THE ECMWF IS MORE AGGRESSIVE WHILE THE GFS TRIES TO
DEFLECT MOST OF THE ENERGY NORTH ACROSS THE BORDER. TEMPERATURES
WILL SLOWLY MODERATE THROUGH THE LONG TERM PERIOD.

&&

.AVIATION...
LOW PRESSURE OVER NORTHWESTERN SOUTH DAKOTA WILL BEGIN
MOVING NORTHEAST TONIGHT DRAGGING A COLD FRONT ACROSS WESTERN AND
CENTRAL NORTH DAKOTA THROUGH EARLY SATURDAY MORNING. IN DOING SO
SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP ALONG AND BEHIND
THE FRONT. SOME THUNDERSTORMS MAY POSSIBLY BE SEVERE WITH LARGE
HAIL...DAMAGING WINDS...AND AN ISOLATED TORNADO. PRIOR TO THE
POTENTIAL SEVERE WEATHER...KI SN WILL REMAIN ON THE COOL AND MOIST
SIDE OF THE FRONT WHICH WILL CONTINUE RESULTING IN SOME FOG AND
LIGHT SHOWERS THROUGH EARLY EVENING. MVFR TO IFR CEILINGS WILL
CONTINUE AT KISN UNTIL THE COLD FRONT MOVES THROUGH AND LIFTS THE
CEILINGS TO MVFR/LOW VFR AROUND 02Z SAT. IFR CEILINGS ARE THEN
LIKELY AFTER THE COLD FRONT MOVES THROUGH...AFTER 06Z THROUGH 18Z
SATURDAY. WITH THE EXCEPTION OF KJMS...KMOT/KDIK/KBIS ARE EXPECTED
TO EXPERIENCE SOME MVFR/IFR CEILINGS FOR A COUPLE HOURS AS THE COLD
FRONT PASSES. KJMS SHOULD REMAIN VFR THROUGH 18Z SATURDAY.

&&

.HYDROLOGY...
WITH RECENT HEAVY RAINS OVER THE SOURIS RIVER BASIN THE
LAST FEW DAYS...RIVER LEVELS AT TOWNER AND BANTRY ARE RISING. FOR
THE SOURIS RIVER NEAR TOWNER...THE RIVER LEVEL MAY REACH FLOOD STAGE
BY LATE TUESDAY OF NEXT WEEK. THE RIVER LEVEL NEAR BANTRY SHOULD
REMAIN JUST BELOW FLOOD STAGE. HOWEVER...THIS ALL DEPENDS ON HOW
MUCH ADDITIONAL RAINFALL IS GENERATED BY THE SHOWERS AND
THUNDERSTORMS TONIGHT THROUGH SATURDAY. FOR THE MISSOURI RIVER NEAR
WILLISTON THE CURRENT RIVER LEVEL IS JUST BELOW FLOOD STAGE AND IS
FORECAST TO SLOWLY FALL THROUGH THE WEEKEND. MINOR FLOODING
CONTINUES AT THE JAMES RIVER NEAR LUDDEN WITH A FORECAST RISE TO
MODERATE FLOODING BY MONDAY OF NEXT WEEK. REISSUED FLASH FLOOD
WATCH FOR NORTHWEST AND NORTHCENTRAL WITH GOOD CHANCES LARGE
CONVECTIVE COMPLEX DEVELOPING OVERNIGHT AND MOVING ACROSS ALREADY
SATURATED SOILS OF WEST CENTRAL TO NORTH CENTRAL NORTH DAKOTA.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH SATURDAY AFTERNOON FOR NDZ001>005-
009>012-017.

&&

HW/CH/KS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
1208 AM CDT SAT MAY 29 2010

NDZ001>005-009>012-017-300515-
DIVIDE-BURKE-RENVILLE-BOTTINEAU-ROLETTE-WILLIAMS-MOUNTRAIL-WARD-
MCHENRY-MCKENZIE-
1208 AM CDT SAT MAY 29 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
NORTH DAKOTA AND NORTHWEST NORTH DAKOTA.

.DAY ONE...TONIGHT

A FLASH FLOOD WATCH IS IN EFFECT TONIGHT THROUGH SATURDAY MORNING.
THUNDERSTORMS ARE LIKELY TONIGHT AND INTO SATURDAY MORNING...SOME
POSSIBLY SEVERE. HEAVY RAINS OVER THE PAST FEW DAYS...COMBINED
WITH A PERSISTENT MOIST WEATHER PATTERN...WILL BRING THE POTENTIAL
FOR HEAVY RAIN AND FLASH FLOODING OVER NORTHWEST NORTH DAKOTA
TONIGHT AND SATURDAY MORNING.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THERE IS A CHANCE OF THUNDERSTORMS SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED.

NDZ013-019>023-025-034>037-042-045>048-050-051-300515-
PIERCE-MERCER-OLIVER-MCLEAN-SHERIDAN-WELLS-FOSTER-MORTON-BURLEIGH-
KIDDER-STUTSMAN-GRANT-SIOUX-EMMONS-LOGAN-LA MOURE-MCINTOSH-DICKEY-
1208 AM CDT SAT MAY 29 2010 /1108 PM MDT FRI MAY 28 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
NORTH DAKOTA...SOUTH CENTRAL NORTH DAKOTA AND SOUTHEAST NORTH
DAKOTA.

.DAY ONE...TONIGHT

THERE IS A CHANCE OF THUNDERSTORMS TONIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THERE IS A CHANCE OF THUNDERSTORMS SATURDAY...SOME POSSIBLY SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

NDZ018-031>033-040-041-043-044-300515-
DUNN-GOLDEN VALLEY-BILLINGS-STARK-SLOPE-HETTINGER-BOWMAN-ADAMS-
1208 AM CDT SAT MAY 29 2010 /1108 PM MDT FRI MAY 28 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST NORTH
DAKOTA.

.DAY ONE...TONIGHT

THERE IS A GOOD CHANCE OF THUNDERSTORMS TONIGHT...SOME POSSIBLY
SEVERE.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THERE IS A CHANCE OF THUNDERSTORMS SATURDAY...SOME POSSIBLY SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

JV