Issued by NWS Hastings, NE
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000 FXUS63 KGID 250459 AFDGID AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HASTINGS NE 1059 PM CST TUE NOV 24 2009 .AVIATION...06Z KGRI TAF. VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD. HIGH CLOUDS WILL CONTINUE TO INCREASE EARLY THIS MORNING AND THERE COULD BE A FEW FLURRIES TOWARDS DAYBREAK...BUT WILL LEAVE MENTION OF SNOW OUT OF THE TAF FOR NOW AS IT SHOULD NOT BE A BIG DEAL...MAYBE JUST A FEW FLAKES. CLOUDS WILL THEN THIN OUT AGAIN BUY MID MORNING. THE GREATER IMPACT WILL BE ANOTHER COLD FRONT SURGING SOUTHEAST WITH INCREASING NORTHWEST WINDS...ASSOCIATED WITH DECENT PRESSURE RISES BEHIND THE COLD FRONT. NORTHWEST WINDS WILL BE ESPECIALLY GUSTY BY LATE MORNING THROUGH MID AFTERNOON WITH GUSTS OF 25 TO 30 KTS. && .PREV DISCUSSION... /ISSUED 316 PM CST TUE NOV 24 2009/ SHORT TERM...TONIGHT THROUGH 12Z THURSDAY. BIGGEST FORECAST CHALLENGE WILL BE WIND SPEEDS FOR WEDNESDAY. WATER VAPOR LOOP REVEALS THE TROUGH AXIS OF THE VIGOROUS LONGWAVE THAT MOVED THROUGH LAST NIGHT CONTINUES ITS WAY INTO THE MISSISSIPPI VALLEY. THE PROGRESSIVE PATTERN CONTINUES AS A SHORTWAVE TROUGH IS DIVING SOUTH SOUTHEAST INTO THE NORTHERN HIGH PLAINS TODAY...WITH A SHORTWAVE RIDGE PRECEDING...AGAIN ALL WITHIN PROGRESSIVE NORTH NORTHWEST FLOW. A LONGWAVE RIDGE IS MOVING ONTO THE WEST COAST. FOR TONIGHT....THE AFOREMENTIONED SHORTWAVE RIDGE WILL MOVE THROUGH...WITH THE RIDGE AXIS CROSSING THE CWA ROUGHLY AROUND MIDNIGHT. THIS WILL LEAD TO ASSUREDLY DRY CONDITIONS FOR THE EVENING. THE AFOREMENTIONED SHORTWAVE TROUGH WILL BEGIN MOVING IN LATE IN THE PERIOD...WITH WEST WIND BECOMING MORE NORTHWEST AND WITH INCREASING SPEED BEHIND AN ATTENDANT COLD FRONT. SOME FLURRIES ARE POSSIBLE WITH THE COLD FRONT PASSAGE...BUT MOISTURE IS MEAGER AND I AM NOT EXPECTING MUCH OUT OF THIS. THE TREND IS A BIT FASTER FOR THIS PARTICULAR SHORTWAVE...SO I WILL PROBABLY BRING THE ISOLATED FLURRIES FROM THE PREVIOUS FORECAST SOUTH ANOTHER ROW OF COUNTIES TO THE STATE LINE FOR THE 06Z TO 12Z TIME PERIOD...A MINOR CHANGE. CONSIDERING THE PROGRESSIVE NATURE OF THE PATTERN...MODELS ARE IN REMARKABLE AGREEMENT WITH THE TIMING OF THIS WAVE AND THE CLOSED LOW ASSOCIATED WITH IT. WENT BELOW MODEL GUIDANCE FOR LOW TEMPERATURE. THE TEMPERATURE CURVE WILL PROBABLY NOT BE A TYPICAL DIURNAL CURVE THE PERIOD WILL BEGIN WITH CLEAR OR NEARLY CLEAR SKY...INCREASING LATER IN THE PERIOD. DEWPOINTS ARE ALSO IN THE LOWER TO MID 20S...WHICH WILL ALSO AID IN THE QUICK DROP OFF. ALSO...WIND SPEEDS PICK UP AFTER MIDNIGHT AS FRONT MOVES IN. THIS WILL LEND TO A SHARP DROP OFF IN THE FIRST FEW HOURS OF THE EVENING...AND THEN A STEADY OR SLOWLY FALLING TEMPERATURE FOR THE REST OF THE NIGHT. WILL GO GENERALLY BELOW MODEL GUIDANCE VALUES. I KNOCKED DOWN THE DEWPOINTS A BIT FOR TONIGHT IN THE GRIDS. FOR WEDNESDAY...A FEW MORNING FLURRIES MAY BE LEFT OVER IN THE SOUTHERN CWA ASSOCIATED WITH THE COLD FRONT PASSAGE...BUT AGAIN...NOT MUCH IS EXPECTED WITH THIS. MODELS SUGGEST THAT MIXING HEIGHTS WILL BE A BIT HIGHER THAN TODAY...NEAR 800 MB BY WEDNESDAY AFTERNOON...LEADING TO A BIT MORE BRISK CONDITIONS COMPARED TO CONDITIONS TODAY. MODELS HAVE GENERALLY BACKED OFF A BIT FOR POTENTIAL WIND GUSTS...BUT WE STILL COULD GET 35 KT WIND GUSTS AND SUSTAINED WIND SPEEDS LOOK LIKE THEY WILL FLIRT WITH WIND ADVISORY CRITERION FOR WEDNESDAY AFTERNOON. A CLOSED LOW IS EXPECTED WITH THE WAVE PASSING THROUGH...BUT ALL MODELS POINT TOWARD THIS FEATURE REMAINING WELL NORTHEAST OF THE CWA...KEEPING US OUT OF ANY MEASURABLE PRECIPITATION POTENTIAL. GOING BELOW MODEL GUIDANCE VALUES FOR HIGH TEMPERATURES...WITH A GOOD LITTLE PUNCH OF COLD AIR ADVECTION EXPECTED. FOR WEDNESDAY NIGHT...TROUGH AXIS MOVES EAST OF THE CWA AND HELPS DEEPEN THE LONGWAVE TROUGH TO THE EAST THAT WAS FIRST DEVELOPED FROM THE WAVE WHICH PASSED THROUGH LAST NIGHT. THE FIRST WAVE WEAKENS AND MOVES NORTHEAST INTO CANADA AS THE SECOND WAVE REINFORCES THE LONGWAVE TROUGH IN THE MISSISSIPPI/OHIO VALLEY. LONGWAVE RIDGING BEGINS TO BUILD IN ACROSS THE CWA...ONCE AGAIN ASSURING A DRY FORECAST. HOLDING RELATIVELY CLOSE TO MODEL GUIDANCE NUMBERS FOR LOW TEMPERATURES. I KNOCKED DOWN DEWPOINTS FOR THIS PERIOD BY A FEW DEGREES. LONG TERM...12Z THURSDAY THROUGH TUESDAY. PRIMARY FORECAST CONCERN LIES WITH PRECIPITATION CHANCES. FIRST PORTION OF THE LONG TERM PERIOD...THURSDAY THROUGH SATURDAY...STILL ON TRACK TO BE DRY. MODELS IN GOOD AGREEMENT AT 12Z THURSDAY...SHOWING A MORE AMPLIFIED UPPER LEVEL PATTERN ACROSS THE CONUS. TROUGH/POTENT LOW PRESSURE SYSTEM WHICH CROSSES THROUGH ON WEDNESDAY SHIFTS ON INTO THE MIDWEST REGION...WITH A RIDGE BUILDING IN ACROSS THE ROCKIES AS ANOTHER TROUGH APPROACHES THE WEST COAST. THIS RIDGE REMAINS THE PRIMARY UPPER LEVEL FEATURE ACROSS THE REGION THROUGH THE END OF THE WEEK. THE AXIS GRADUALLY SHIFTS OUT OF THE ROCKIES...EVENTUALLY DRAPED THROUGH THE PLAINS ON FRIDAY...BEFORE SHIFTING OFF FURTHER EAST AND BEGINNING TO BREAK DOWN AS THE NEXT SYSTEM APPROACHES. AT THE SFC...HIGH PRESSURE CENTERED TO THE SOUTH LINGERS AROUND THE CWA DURING THE FIRST PART OF THURSDAY...BEFORE SHIFTING TO THE EAST AS A TROUGH OF LOW PRESSURE DEVELOPS ALONG THE FRONT RANGE. THIS WILL BRING LIGHTER WEST WINDS ON THURSDAY...GRADUALLY SWITCHING TO SOUTH THURSDAY NIGHT AND CONTINUING ON THROUGH FRIDAY. AS WE GET INTO SATURDAY...THE UPPER LEVEL PATTERN ACROSS THE PLAINS HAS TRANSITIONED TO SOUTHWESTERLY FLOW...AS THE NEXT SYSTEM TO IMPACT THE AREA SITS OVER THE ROCKIES. A PIECE OF MID LEVEL SHORTWAVE ENERGY MOVING THROUGH WILL PUSH A SFC COLD FRONT INTO THE CWA DURING THE DAY...BUT NO PRECIPITATION IS EXPECTED. AS FAR AS TEMPERATURES GO THURS THROUGH SAT...WARMER HIGHS EXPECTED ON THURSDAY...WITH THE WARMEST READINGS ON FRIDAY AS THAT UPPER LEVEL RIDGE SITS OVERHEAD. HIGHS EXPECTED TO REACH WELL INTO THE 50S...WITH A FEW LOWER 60S POSSIBLE...ON FRIDAY BEFORE COOLING BACK DOWN INTO THE UPPER 40S/LOWER 50S FOR SATURDAY. CONFIDENCE IN THE FORECAST FROM SUNDAY THROUGH TUESDAY IS ON THE LOW SIDE...AS MODELS CONTINUE TO STRUGGLE WITH THE EVOLUTION OF THE SYSTEM MOVING OUT OF THE ROCKIES. TIMING OF THE SYSTEM HAS NOT BEEN QUITE AS MUCH OF AN ISSUE AS THE LOCATION/STRUCTURE HAS BEEN. MODELS HAVE NOT VERY CONSISTENT ON WHETHER ITS MORE OF AN OPEN TROUGH THAT PUSHES THROUGH OR A CLOSED LOW...AND WHETHER THE MORE ORGANIZED STRUCTURE/LIFT/PRECIP SHIFTS THROUGH THE NORTHERN OR SOUTHERN PLAINS. FORECAST IS TRENDED MORE TOWARDS THE SLIGHTLY MORE CONSISTENT ECMWF...AND KEPT PRECIP MENTION CONFINED TO THE SOUTHERN PORTIONS OF THE CWA...AS THE MAIN UPPER LEVEL SYSTEM CROSS THROUGH KANSAS. HAVE THE TIMING OF THE POPS RUNNING FROM SUNDAY THROUGH MONDAY...BUT ADJUSTMENTS OVER THE NEXT FEW DAYS ARE LIKELY AS MODELS COME INTO BETTER AGREEMENT. REGARDLESS TO THE EXACT PATH OF THE SYSTEM...COOLER TEMPERATURES ARE EXPECTED WITH THE PASSAGE OF THE COLD FRONT ON SATURDAY...AND TRENDED BACK HIGHS FOR SUN THROUGH TUES BACK INTO THE UPPER 30S/LOWER 40S. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$