000
FXUS63 KEAX 212331
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
631 PM CDT THU AUG 21 2008
...UPDATED AVIATION DISCUSSION...
.DISCUSSION...
/324 PM CDT THU AUG 21 2008/
SHORT RANGE (TONIGHT-SATURDAY)...
COOL WEATHER PREVAILED ACROSS THE REGION TODAY AS AN PERSISTENT
CUTOFF LOW CIRCULATED ACROSS THE LOWER MISSOURI RIVER VALLEY. WATER
VAPOR IMAGERY TODAY SHOWS THE LOW BEGINNING TO SHEAR OUT AS THE MAIN
LEADING CIRCULATION CAN BE SEEN MOVING NORTH OF MISSOURI LEAVING
BEHIND A SHEAR AXIS STRETCHING BACK INTO OKLAHOMA. THE AXIS WILL
CONTINUE TO STRETCH OUT ACROSS THE PLAINS THROUGH SATURDAY...WHEN A
PROGRESSIVE SHORTWAVE MOVING EAST ALONG THE CANADIAN BORDER WILL
DRAG A COLD FRONT SOUTH INTO THE PLAINS AND DISLODGING WHAT IS LEFT
OF THE CIRCULATION.
FOR TONIGHT...MODEL SOUNDINGS AND SATELLITE TRENDS ALL SUPPORT THE
GOING IDEA THAT THE CLOUD COVER WILL SCATTERED A BIT IN THE EVENING
HOURS. HOWEVER...ABUNDANT GROUND MOISTURE AND THE SOUTHERLY FETCH OF
SUBTROPICAL MOISTURE SHOULD SOCK THE REGION BACK IN LATE IN THE
OVERNIGHT HOURS. WITH DEW POINT DEPRESSIONS DROPPING INTO THE 2-4C
RANGE TONIGHT...MORE AREAS OF FOG LOOK REASONABLE AGAIN FOR FRIDAY
MORNING. HOWEVER...WINDS IN AND JUST ABOVE THE BOUNDARY LAYER LOOK
TO REMAIN UP JUST ENOUGH TO MITIGATE THE POTENTIAL FOR DENSE FOG.
FOR FRIDAY...LINGERING FOG SHOULD BURN OFF DURING THE FIRST HALF OF
THE MORNING HOURS...LEAVING SOME CLEARING SKIES TO MOVE IN FROM THE
WEST. HOWEVER...THE PERSISTENT SHEAR AXIS SHOULD PREVENT THE
CLEARING FROM MOVING TOO FAR EAST OF THE STATE LINE. HAVE CONTINUED
TO GO WITH A RIBBON OF CHANCE POPS ALONG OUR EASTERN BORDER FOR
FRIDAY AFTERNOON AS AFTERNOON DIURNAL INSTABILITY AND THE SHEAR AXIS
MIGHT JOIN FORCES TO AND DEVELOP A FEW THUNDERSTORMS...THOUGH MAIN
THREAT OF THIS OCCURRING LOOKS TO BE FOCUSED ACROSS THE EAST HALF OF
THE STATE.
OTHERWISE...HAVE INCREASED THE TEMPERATURE GRADIENT ACROSS THE
REGION FOR FRIDAY. H8 THERMAL RIDGE LOOKS TO LAY OVER INTO THE
NORTHWEST CORNER OF MISSOURI IN ADVANCE OF THE COLD FRONT MOVING
SOUTH THROUGH THE PLAINS. AS A RESULT...I HAVE OPTED TO USE A BLEND
OF MAV AND MET TEMPERATURES ACROSS THE CWA. EDGING TOWARDS THE
COOLER MET NUMBERS ALONG THE EAST (CLOUDY) SIDE OF THE CWA...AND THE
WARMER MAV NUMBERS ON THE WEST (PARTLY CLOUDY) SIDE.
SATURDAY WILL SEE THE ARRIVAL OF A COOL FRONT INTO THE CENTRAL
PLAINS. LATEST GFS RUNS KEEP THE FRONT MORE PROGRESSIVE ON
SATURDAY...WHILE THE NAM-WRF SLOWS IT DOWN AND WASHES IT OUT ACROSS
CENTRAL MISSOURI. ECMWF SEEMS TO AGREE MORE WITH THE GFS...AT LEAST
IN SO FAR AS IT MOVES THE FRONT INTO SOUTHERN MISSOURI BEFORE IT
WASHES OUT. WHILE THE EASTWARD PROGRESSION OF THE PARENT SHORTWAVE
WOULD FOCUS THE BEST FORCING ON THE FRONT OFF TO THE EAST...STILL
BELIEVE THERE MIGHT BE ENOUGH WEIGHT IN THE POST FRONTAL AIRMASS TO
FORCE THE TAIL OF THE FRONT INTO THE OZARKS. HOWEVER...IN EITHER
CASE...PRECIPITATION CHANCE FOR SATURDAY CONTINUE TO LOOK
POSSIBLE...SO HAVE BUMPED POPS INTO THE 40% RANGE. THREAT OF SEVERE
WEATHER WITH THE FRONT CONTINUES TO LOOK VERY MINIMAL DUE TO A LACK
OF ORGANIZING SHEAR.
CUTTER
MEDIUM RANGE (SUNDAY-THURSDAY)...
THE PROGRESSIVE UPPER TROUGH PATTERN CONTINUES THROUGH MEDIUM RANGE
OF THE FORECAST. THE UPPER TROUGH CURRENTLY OVER SOUTHWEST CANADA
WILL TRACK ACROSS SOUTHERN CANADA/NORTHERN TIER OF STATES THROUGH
THE END OF THE WEEK...BEFORE LIFTING RATHER QUICKLY NORTHEAST ACROSS
EASTERN CANADA THROUGH THE WEEKEND. UPPER RIDGING WILL BUILD ACROSS
THE MIDDLE OF THE NATION FOR THE FIRST PART OF NEXT WEEK...BEFORE
ANOTHER PROGRESSIVE TROUGH ENTERS SOUTHERN CANADA...ONCE AGAIN
TRACKING GENERALLY TO THE EAST.
AS THE SURFACE FRONT DRIFTS SLOWLY SOUTH THIS WEEKEND...IT IS
FORECAST TO CONTINUE A SLOW PROGRESSION AS IT WASHES OUT ACROSS
SOUTHERN MISSOURI ON SUNDAY. KEPT LOW END PRECIPITATION CHANCES FOR
THE SOUTHERN FORECAST SECTIONS ON SUNDAY...WITH WEAK SHORTWAVE
ENERGY SLIDING ACROSS BUT LITTLE CONVERGENCE LEFT ALONG THE POSSIBLY
LINGERING FRONT. HAVE A SLIGHT WARMING TREND THROUGH THE WORK WEEK
AS WARM ADVECTION SETS UP.
THE MEDIUM RANGE MODELS THEN START TO DIVERGE A BIT MORE TOWARD THE
MIDDLE OF NEXT WEEK...AS ONE WOULD EXPECT. WENT CLOSER TO THE ECMWF
AND HPC GUIDANCE IN THE SLOWER PROGRESSION OF A SURFACE FRONT
PUSHING EAST AHEAD OF THE ADVANCING UPPER TROUGH...KEEPING
PRECIPITATION CHANCES LIMITED THROUGH MID WEEK.
STOFLET
&&
.AVIATION...
FOR THE 00Z TAFS...VFR CONDITIONS WITH ONLY SCATTERED CLOUD COVER
EXPECTED THROUGH MIDNIGHT. ONLY KSTJ WILL SEE A TEMPORARY CEILING
AROUND 7K FT FOR THE FIRST FEW HOURS OF THE FORECAST. CONSIDERABLE
MOISTURE IS PRESENT IN THE LOWER PORTION OF THE ATMOSPHERE AND
CONDITIONS FAVOR IFR FOG/STRATUS FORMATION STARTING IN THE PRE-DAWN
HOURS AND ENDING A FEW HOURS AFTER SUNRISE. HAVE MADE A FEW MINOR
TWEAKS TO THE PREVIOUS FORECAST CONCERNING FORMATION/DISSIPATION OF
FOG/STRATUS. BY MID MORNING FRIDAY EXPECT VFR CONDITIONS TO PREVAIL
FOR THE REST OF THE FORECAST.
MJ
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
$$
