AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LITTLE ROCK AR 250 PM CST SUN JAN 4 2015 .SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT THE MAIN CONCERN FOR THE SHORT TERM PERIOD REALLY IS HOW COLD TEMPERATURES WILL GET. BROAD UPPER TROUGHING WILL REMAIN IN PLACE ACROSS THE EASTERN HALF OF THE UNITED STATES THROUGH THE SHORT TERM...WITH RIDGING OUT WEST. THE PATTERN WILL AMPLIFY HEADING INTO WEDNESDAY NIGHT...SIGNALING THE ARRIVAL OF A VERY COLD AIR MASS TO ROUND OUT THE SHORT TERM. CLOUDS ARE CLEARING ACROSS THE STATE THIS AFTERNOON AS COLD ARCTIC AIR POURS INTO ARKANSAS. WINDS SHOULD BE LIGHT ENOUGH TONIGHT SUCH THAT NO WIND CHILL ADVISORIES WILL BE NEEDED...HOWEVER WITH TEMPERATURES EXPECTED TO DROP INTO THE TEENS TO LOW 20S...OR POSSIBLY SOME SINGLE DIGITS IN SHELTERED LOCALES IN THE NORTHWEST...ANY BREEZE THIS EVENING OR OVERNIGHT WILL MAKE FOR FRIGID WIND CHILL VALUES. SINGLE DIGIT WIND CHILLS WILL BE THE NORM IN THE NORTH TONIGHT...WITH LOW TEENS EXPECTED ELSEWHERE. A 1035-1040 MILLIBAR SURFACE HIGH WILL SLIDE INTO SOUTHERN MISSOURI AND NORTHERN ARKANSAS MONDAY THEN SHIFT EAST OF THE STATE ON MONDAY NIGHT. A DISTURBANCE IN THE NORTHWEST UPPER FLOW WILL THEN BRING A SYSTEM FRONT OFF THE COLORADO HIGH PLAINS ACROSS THE CENTRAL PLAINS AND INTO THE TENNESSEE RIVER VALLEY LATE MONDAY NIGHT INTO TUESDAY. THE ASSOCIATED COLD FRONT WILL PASS THROUGH ARKANSAS ON TUE BUT WILL BE A DRY FRONTAL PASSAGE. THIS WILL BE FOLLOWED BY ANOTHER DRY FRONTAL PASSAGE ON WEDNESDAY...BUT THIS WILL BE AN ARCTIC FRONT BEING DRIVEN BY A FRIGID 1050-1060 MILLIBAR SURFACE HIGH MOVING DOWN THE PLAINS. HIGHS IN THE 30S TO LOW 40S ARE EXPECTED MONDAY...FOLLOWED BY UPPER 30S TO LOW 40S BEFORE THE DRY FRONTAL PASSAGE ON TUESDAY. HOWEVER THIS WILL DIFFER DRAMATICALLY FROM WEDNESDAY WHEN TEMPERATURES WILL HOLD STEADY OR FALL THROUGH THE DAY BEHIND THE ARCTIC FRONT...YIELDING DAYTIME HIGHS THAT MAY FAIL TO RISE ABOVE FREEZING FOR MUCH OF THE STATE. ALSO...LOWS WEDNESDAY NIGHT WILL LIKELY DROP INTO THE SINGLE DIGITS FOR A GOOD PORTION OF THE NORTHERN HALF OF ARKANSAS. IN FACT...SOME ENSEMBLE MODEL OUTPUT STATISTICS PRODUCTS INDICATE THAT OVERNIGHT LOWS BETWEEN ZERO AND NEGATIVE 7-10 DEGREES MAY OCCUR UP NORTH WEDNESDAY NIGHT. HAVE NOT GONE THAT FAR YET...BUT THE LATEST GUIDANCE IS COLDER THAN PREVIOUS SHIFTS FORECAST AND AS SUCH HAVE TRENDED THE FORECAST IN THAT DIRECTION. WOULD NOT BE SURPRISED TO SEE THIS TREND CONTINUE. WILL DEFINITELY NEED TO LOOK AT POSSIBILITY OF WIND CHILL ADVISORY FOR WEDNESDAY NIGHT AND POSSIBLY THURSDAY TOO...BUT THERE IS A LOT OF TIME TO DECIDE ON THAT. INCIDENTALLY...FROM A CLIMATE PERSPECTIVE...MANY LOCATIONS IN CENTRAL AND NORTHERN ARKANSAS HAVE RECORD LOWS FOR FOR JANUARY 7TH AND 8TH THAT ARE IN THE ZERO TO NEGATIVE TEN DEGREE RANGE AND RECORD LOW-HIGH TEMPERATURES THAT ARE IN THE TEENS TO LOW 20S. A HANDFUL OF LOCATIONS MAY APPROACH RECORD COLD VALUES...BUT BY IN LARGE EVEN THIS COLD OF AN AIR MASS DOES NOT APPEAR TO BE A RECORD BREAKING ONE. AT LEAST NOT IN A WIDESPREAD SENSE ANYWAY. .LONG TERM...THURSDAY THROUGH SUNDAY ARCTIC HIGH PRESSURE WILL BE CENTERED OVER THE REGION AND BRING THE COLDEST AIR OF THE WINTER SEASON TO ARKANSAS. LOWS WILL BE IN THE TEENS TO SOME SINGLE DIGITS...WHILE HIGHS FROM THE 20S TO AROUND 40. THURSDAY NIGHT TO FRIDAY...A REINFORCING COLD FRONT SAGS SOUTH INTO NORTHERN ARKANSAS...WHILE THEN MODELS STALL THE BOUNDARY OVER CENTRAL TO NORTHERN ARKANSAS. ABOVE FREEZING TEMPERATURES WILL BE SOUTH OF THE BOUNDARY...WHILE ALONG AND TO THE NORTH...AT OR BELOW FREEZING TEMPERATURES WILL BE SEEN. ADDITIONALLY...THE UPPER PATTERN SHOWS A SHORT WAVE SYSTEM WITHIN THE UPPER NORTHWEST FLOW IN THE SOUTHERN STREAM...AND PRECIPITATION IS BACK IN THE FORECAST. OF COURSE RAIN WILL BE SEEN SOUTH OF THE FREEZING LINE...WHILE A MIX AROUND AND THEN SNOW NORTH IN THE COLDEST AIR. MODELS ARE IN BETTER AGREEMENT TODAY BUT SOME UNCERTAINTY IS IN THE FORECAST WHERE THE LOCATION OF THE BOUNDARY SETS UP...AND HOW MUCH MOISTURE ADVECTS INTO ARKANSAS. LATE FRIDAY AND EARLY SATURDAY AND THEN AGAIN LATE SATURDAY TO SUNDAY MORNING...BEST CHANCES OF WINTER WINTER WILL BE OVER NORTH CENTRAL AND NORTH ARKANSAS...WHILE MAINLY RAIN DURING THE DAY SATURDAY AND SUNDAY CENTRAL AND SOUTH. THE PRECIPITATION FINALLY MOVES OUT LATE SUNDAY TO EARLY MONDAY.
Posted on: Sun, 04 Jan 2015 21:44:29 +0000
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