Areal Flood Advisory 2, NWS Grand Forks, ND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND FORKS ND
242 PM CDT THU JUL 12 2012

.SHORT TERM (TONIGHT-SUNDAY)...MAIN CONCERN WILL BE SEVERE CHANCES
THIS AFTERNOON AND EVENING. 12Z MODELS IN DECENT AGREEMENT THROUGH
SATURDAY...THEN DIVERGE ON SUNDAY. SOME SORT OF BLENDED SOLUTION
SHOULD WORK JUST FINE.

LATEST LAPS ANALYSIS INDICATES MLCAPE 1500-2500 J/KG ACROSS
EASTERN NORTH DAKOTA INTO NORTHWEST MINNESOTA...WITH MLCIN LESS
THAN -20 J/KG. SATELLITE IMAGERY INDICATES A CIRCULATION JUST
NORTH OF THE INTERNATIONAL BORDER AND ANOTHER CIRCULATION AROUND
DEVILS LAKE. SFC BOUNDARY/COLD FRONT IS ACROSS THE WESTERN EDGE
OF THE VALLEY...AND DEWPOINT VALUES ARE POOLING TO NEAR 70F HERE.
THE STAGE APPEARS SET FOR SCATTERED THUNDERSTORMS. THE MAIN
QUESTIONS WILL BE HOW WIDESPREAD AND HOW STRONG GIVEN WEAK DEEP
LAYER SHEAR/SLOW STORM MOTIONS AND A REMAINING WEAK CAP. DEEP
LAYER SHEAR IS STRONGER ACROSS THE SOUTHERN FA...BUT THUNDER
POTENTIAL IS LESS GIVEN WEAKER LOW-LEVEL CONVERGENCE AND A BIT
STRONGER CIN. ANYWAY...LIKELY WILL BE PULSE TYPE STORMS WITH A FEW
SEVERE LARGE HAIL/WIND REPORTS. THERE WILL ALSO BE THE POTENTIAL
FOR NON-SUPERCELL TORNADOS NEAR THE INTERNATIONAL BORDER WITH MAIN
UPPER LEVEL LOW IN THE VICINITY ALONG WITH STRONG LOW-LEVEL CAPE
AND LAPSE RATES. THIS ACTIVITY SHOULD DECREASE AFTER SUNSET. THIS
ENTIRE SYSTEM PROPAGATES EAST...WITH SIMILAR ACTIVITY ACROSS THE
FAR EASTERN FA ON FRIDAY. RIDGING BUILDS INTO THE REGION ON
SATURDAY (WITH VERY LOW PRECIP CHANCES ACROSS THE EASTERN FA
DEPENDING ON HOW FAST THE PATTERN EVOLVES).

BY SUNDAY...AN UPPER WAVE FROM THE SOUTHWEST CONUS WILL ROUND THE
UPPER RIDGE AND SET UP AN INTERESTING SCENARIO. THERE WILL LIKELY
BE A WARM FRONT SOMEWHERE WITHIN OR NEAR THE REGION BY SUNDAY
AFTERNOON. THE NAM IS STRONGEST WITH THIS FEATURE INDICATING AN
AFTERNOON TEMP OF 70F ALONG THE INTERNATIONAL BORDER TO OVER 100F
AROUND AND SOUTH OF GRAND FORKS. OTHER MODELS ARE NOT AS DEFINED
WITH THIS FEATURE OR A BIT SLOWER WITH THE MAIN UPPER WAVE. IT
DOES SEEM THAT WARM AIR ALOFT WILL INHIBIT THUNDER DEVELOPMENT
THROUGH MUCH OF SUNDAY WITH BEST CHANCES AFTER 00Z MONDAY. USED A
MODEL BLEND FOR DETAILS.

TEMPERATURES THROUGH THE PERIOD WILL REMAIN ABOVE NORMAL.

.LONG TERM (SUNDAY NIGHT-THURSDAY)...GFS/ECMWF/GEM HAVE TIMING
DIFFERENCES...WILL LEAN TOWARD ECMWF SOMEWHAT FOR THIS FCST CYCLE.
AN UPPER LEVEL S/WV TROF MOVES ALONG THE INTL BORDER THEN INTO THE
GTLKS REGION AT THE BEGINNING OF THE PERIOD WITH THE ASSOCIATED
SFC LOW AND FNTL BNDRY MOVING THRU THE FCST AREA MON. UPPER
RIDGING BUILDS INTO THE UPPER MIDWEST WED INTO THU BEFORE THE NEXT
S/WV RIDES THE RIDGE INTO THE FCST AREA. WILL CONT THE ALLBLEND
LOW END CHC POPS THRU THE EXTENDED THO TUE NITE INTO WED APPEAR TO
BE THE BEST OPPORTUNITY FOR A DRY PERIOD. TEMPS WILL BE WELL ABOVE
NORMAL ON MON AHEAD OF THE FRONT BEFORE COOLING DOWN INTO THE 80S
MOST PLACES EXCEPT FOR SOME 70S IN THE NE FCST AREA FROM MIDWEEK
ON.

&&

.AVIATION...AN UNSTABLE AIRMASS AND UPPER LEVEL S/WV TROF OVER
SRN MANITOBA/ND THIS AFTN HAS LED TO WIDELY SCTD TSTMS DEVELOPING
ACROSS THE REGION...THIS CONVECTION WILL PERSIST INTO THE EVENING.
HAVE INCLUDED VCTS FOR ALL SITES EXCEPT KDVL. VFR CONDS ACROSS THE
TAF SITES THIS AFTN WILL PERSIST INTO THIS EVENING WITH A SCTD
DECK OF 4K TO 6K FT MOST SITES FROM 22Z UNTIL 03Z. MVFR CONDS WILL
PERSIST AT KTVF AND KBJI FURTHER INTO THE NIGHT. THE SFC BNDRY
CURRENTLY LOCATED FROM THE LOW OVER THE NRN VALLEY SSWD THRU THE
VALLEY WILL SLOWLY ADVECT EAST OVERNIGHT. A WIND SHIFT FROM SSW TO
NW WILL OCCUR FROM THE VALLEY EAST OVERNIGHT. NW WINDS AT KDVL
WILL PERSIST THRU THE FCST PERIOD.

&&

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

TG/FRAZIER