Issued by NWS Topeka, KS
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000 FXUS63 KTOP 061746 AFDTOP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 1146 AM CST FRI FEB 6 2009 .UPDATE... UPDATE FOR 18 UTC AVIATION. && .DISCUSSION... SEE PREVIOUS DISCUSSION. && .AVIATION... FALLING SURFACE PRESSURES TO THE NORTHWEST WITH NEAR STEADY PRESSURES TO THE SOUTHEAST THIS MORNING HELPING BRING INCREASING SOUTH WINDS TO THE TERMINALS...WITH FURTHER INCREASES EXPECTED THIS AFTERNOON. DIURNAL COOLING ALONG WITH EXITING LOW PRESSURE SHOULD BRING SOME DECREASE IN THE WINDS THIS EVENING...BUT WINDS NOT FAR OFF THE SURFACE WILL REMAIN QUITE BRISK...ESPECIALLY IN THE TOP/FOE AREA. WILL NEED TO MONITOR POSSIBLE LLWS AS THE LATE EVENING HOURS APPROACH. NEARING COOL FRONT WILL BRING FURTHER WIND DECREASES OVERNIGHT. 65 && .PREV DISCUSSION... /ISSUED 420 AM CST FRI FEB 6 2009/ DISCUSSION... WATER VAPOR IMAGERY SHOWING INITIAL SHORTWAVE THAT CAME ASHORE OFF THE PACIFIC YESTERDAY MAKING NORTHEAST PROGRESS AND WEAKENING ACROSS THE CENTRAL ROCKIES. THIS WAVE IS AIDING THE UPPER RIDGING AND EASTWARD PROGRESSION OF WARMER AIR ALOFT INTO THE CENTRAL PLAINS. A STRONGER SHORTWAVE IS DIGGING SOUTHEAST TOWARDS THE SOUTHERN CA COAST...AND WILL BE THE MAIN PLAYER THE END OF THE WEEKEND INTO EARLY NEXT WEEK AS IT LIFTS OUT INTO THE CENTRAL PLAINS. AT THE SFC...MODIFIED AND SHALLOW LOW LEVEL MOISTURE IS CONTINUING TO SPREAD NORTHWARD INTO THE CWA WITH DEWPOINTS 20 TO 25 DEGREES HIGHER THAN 24 HOURS AGO...HOWEVER DRIER AIR REMAINS JUST WEST OF THE CWA. AS SFC TROUGH DEEPENS IN THE HIGH PLAINS TODAY WINDS WILL CONTINUE TO INCREASE WITH LOW LEVEL THERMAL AXIS ORIENTED SOUTHWEST TO NORTHEAST ACROSS THE CWA BY AFTERNOON. ALTHOUGH SOME HIGH CLOUDS WILL DRIFT ACROSS THE CWA TODAY...WAA AND MIXING SHOULD STILL PUSH HIGHS INTO THE 60S ALL AREAS WITH NEAR 70 IN THE SOUTHWEST CWA. THIS WILL RESULT IN RECORD OR NEAR RECORD HIGHS MANY AREAS AS RECORDS IN TOPEKA AND CONCORDIA ARE 71 AND 63 RESPECTIVELY. ALTHOUGH LOW LEVELS THROUGH 850MB IS NOT UNIDIRECTIONAL...IT IS NEARLY ADIABATIC TO NEAR 50KTS ACROSS THE SOUTHERN CWA BY MID AFTERNOON AND MOMENTUM TRANSFER MAY BE ENOUGH TO REACH WIND ADVISORY CRITERIA...SO HAVE ISSUED A WND ADVISORY ACROSS THE SOUTHERN CWA NOON TO 6PM TODAY FOR AREAS GENERALLY ALONG AND SOUTH OF THE HIGHWAY 56. ALSO...THERE IS CONCERN OVER THE FAR SOUTHWEST CWA THAT WINDS MAY ALLOW SHALLOW MOISTURE TO MIX OUT PRODUCING LOWER DEWPOINTS THAT INDICATED BY MODELS DURING PEAK HEATING. NO PLANS TO ISSUE A RED FLAG WARNING...BUT SOMETHING THE DAY SHIFT WILL NEED TO REEVALUATE LATER TODAY AS WINDS INCREASE...BUT FOR NOW EXPECT RH LEVELS TO REMAIN ABOVE 20 PERCENT THROUGH THE DAY. TONIGHT THE BOUNDARY WILL PUSH SLOWLY SOUTHEAST INTO THE SOUTHEAST CWA WITH DRIER AIR AND SLIGHTLY COOLER TEMPS FOR SATURDAY...BUT STILL IN THE 60S WITH MOSTLY SUNNY SKIES. AS THE MAIN SHORTWAVE APPROACHES THE SOUTHERN PLAINS SATURDAY EVENING...THE LOW LEVEL FLOW WILL BACK ACROSS THE CWA. LOW LEVEL CONVERGENCE/MOISTURE ADVECTION AND ISENTROPIC LIFT MAY BE ENOUGH TO PRODUCE A FEW SHOWERS/ISOLATED THUNDER OVER THE SOUTHEAST CWA AFTER MIDNIGHT SATURDAY NIGHT...BUT A MUCH BETTER CHANCE SHOWERS/EMBEDDED THUNDERSTORMS INTO SUNDAY NIGHT AS REMNANTS OF SQUALL LINE ASSOCIATED WITH COLD FRONT AND SURGING DRY SLOT WITH THE UPPER WAVE MOVE RAPIDLY NORTHEAST ACROSS THE AREA...LIKELY EXITING THE EASTERN CWA IN THE 12Z-18Z TIMEFRAME MONDAY...WITH A LINGERING SLIGHT CHC FOR SHOWERS NORTH AND EASTERN CWA MONDAY AFTERNOON. NEXT SHORTWAVE WILL MOVE EASTWARD INTO THE AREA WEDNESDAY WITH ANOTHER CHANCE FOR RAIN AND/OR SNOW. NO CHANGES MADE TO FCST BEYOND MONDAY OTHER THAN TO INCREASE HIGHS SLIGHTLY FOR TUESDAY. && .TOP WATCHES/WARNINGS/ADVISORIES...WIND ADVISORY UNTIL 6 PM FRIDAY FOR KSZ035-KSZ037-KSZ054-KSZ055-KSZ056-KSZ058-KSZ059. && $$
