FXUS63 KDMX 031717 AAB
AFDDMX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
1117 AM CST THU DEC 3 2009
...UPDATED AVIATION DISCUSSION...
.SHORT TERM [TODAY]...
VORT MAX ROTATING AROUND UPPER LOW IN PLACE ACROSS THE NORTHERN
PLAINS TO BE THE MAIN FOCUS FOR TODAY. LIFT ASSOCIATED WITH THIS
WAVE TO INCREASE ACROSS THE NORTHERN CWA BY THIS MORNING...SPREADING
ACROSS MUCH OF THE REMAINDER OF THE CWA THIS AFTERNOON. DEEPEST
MOISTURE SITUATED ACROSS THE NORTHERN CWA...WITH TEMPERATURES COLD
ENOUGH THAT ALL PRECIP SHOULD BE IN THE FORM OF SNOW. BEST CHANCES
TO SEE SOME LIGHT SNOW SHOWERS WILL BE NORTH OF HIGHWAY 20...WITH AN
ISOLATED OR SCATTERED SHOWER POSSIBLE I-80 TO HWY 20...AND FLURRIES
EXPECTED FURTHER SOUTH. ONLY A FEW HUNDREDTHS OF MOISTURE
AVAILABLE...WITH SNOW RATIOS EXPECTED TO REMAIN AROUND 12 TO 15 TO
1. LAPSE RATES QUITE STEEP SO DO EXPECT MORE OF A SNOW SHOWER TYPE
EVENT THAN STRATIFORM SNOWFALL. THUS EXPECT ABOUT A HALF AN INCH TO
AN INCH ACROSS MOST AREAS...WITH A FEW PLACES THAT COULD SEE 1 TO 2
INCHES OF SNOW POSSIBLE THROUGH THIS AFTERNOON. WITH CLOUDS EXPECTED
ACROSS MUCH OF THE AREA TODAY...AND SNOW SHOWERS ANTICIPATE LITTLE
WARMING EVEN WITH THE WEAK WAA ALOFT. THEREFORE HAVE AROUND A 5 TO 7
DEGREE DIURNAL RANGE.
.LONG TERM [TONIGHT THROUGH WEDNESDAY]...
POTENTIAL FOR SNOW WILL CONTINUE THROUGH EARLY THIS EVENING...MAINLY
OVER THE NORTHEAST WHERE MINOR ADDITIONAL ACCUMULATIONS MAY OCCUR.
FLURRIES WILL REMAIN POSSIBLE ELSEWHERE. MID LEVEL DRYING WILL OCCUR
FROM WEST TO EAST THROUGHOUT THE EVENING AS THE FLOW BECOMES MORE
WESTERLY TO BRING AN END TO THE PRECIPITATION. DESPITE THE WESTERLY
FLOW CONTINUING ON FRIDAY...HIGH TEMPERATURES WILL REMAIN QUITE
COOL. MIXING WILL REACH UP TO 850 MB HOWEVER WITH TEMPERATURES AT
THAT LEVEL OF -14C TO -16C WILL RESULT IN HIGHS IN THE LOWER 20S
NORTH TO THE MID TO UPPER 20S SOUTH. A LITTLE WARMER ON SATURDAY
WITH HIGHS IN THE 30S.
THE NEXT SYSTEM TO AFFECT THE STATE WILL ARRIVE LATE SUNDAY AND
SUNDAY NIGHT. A STRONG SHORT WAVE CURRENTLY OFF THE WEST COAST OF
THE PACIFIC NORTHWEST NEAR THE GULF OF ALASKA...WILL DIVE SOUTHEAST
THROUGH THE INTERMOUNTAIN WEST FRIDAY NIGHT AND SATURDAY. A PORTION
OF THIS ENERGY WILL BE EJECTED OUT TOWARDS THE MIDWEST SATURDAY
NIGHT. CONFIDENCE IS INCREASING FOR THE POTENTIAL OF ACCUMULATING
SNOW TO BEGIN OVER WESTERN IOWA LATE SUNDAY AND SPREAD ACROSS THE
REMAINDER OF THE AREA SUNDAY NIGHT. ADVISORY CRITERIA TYPE SNOWFALLS
CAN NOT BE RULED OUT WITH THIS SYSTEM. THE SYSTEM WILL QUICKLY MOVE
OUT BY MONDAY. THE REMAINDER OF THE WESTERN ENERGY IS EXPECTED TO
CROSS THE ROCKIES SOMETIME TUESDAY. THIS SYSTEM LOOKS MORE POTENT
THOUGH ITS TRACK REMAINS UNCERTAIN. A MORE NORTHERLY TRACK WOULD
MAKE IT INTERESTING IN IOWA. ANOTHER ROUND OF COLD AIR WILL BE
PULLED DOWN BEHIND THIS SYSTEM. A LITTLE SNOW COVER WOULD MAKE A BIG
DIFFERENCE AS TO HOW COLD THIS INTRUSION WILL BE.
&&
.AVIATION...
03/18Z...LARGE MID/UPPER ATMOSPHERE LOW PRESSURE SYSTEM MOVING
ACROSS NORTHERN IA TODAY THEN OFF TO THE EAST OVERNIGHT. EXTENSIVE
MVFR STRATUS SHIELD AROUND THIS LOW WILL KEEP CIGS MVFR...BETWEEN
FL010 AND FL025...AT LEAST THROUGH SUNSET AND MORE LIKELY WELL INTO
TONIGHT. BRIEF IFR ALSO POSSIBLE AT KMCW AND KALO THIS AFTERNOON BUT
PROBABILITY IS TOO LOW TO ADVERTISE IN TAFS ATTM. SNOW AND/OR FOG
WILL ALSO PRODUCE MVFR OR LOWER VSBYS AT THE NORTHERN TERMINALS INTO
THIS EVENING...ESPECIALLY AT KMCW AND KALO...WHERE THIS WILL BE
HANDLED WITH TEMPOS IN THE 18Z ISSUANCE DUE TO THE SOMETIMES
CONVECTIVE NATURE OF THE SNOW. WILL NOT HOLD ONTO THE FOG INTO
TONIGHT AS GOOD WINDS/MIXING SHOULD PREVENT SIGNIFICANT FORMATION.
BY FRIDAY MORNING CLOUDS WILL BEGIN TO BREAK UP A BIT WITH RISING
CIGS INTO THE VFR RANGE...HOWEVER CLOUDS MAY THICKEN/LOWER AGAIN
RIGHT AROUND THE END OF THE 18Z TAF PERIOD AS ANOTHER SHORTWAVE
MOVES ACROSS NORTHERN IOWA.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...BEERENDS
AVIATION...LEE
LONG TERM...DONAVON
