FXUS63 KDMX 101726 AAA
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1130 AM CST WED DEC 10 2009
...UPDATED AVIATION DISCUSSION...
.SHORT TERM /TODAY/...
LO PRES EXITING THE REGION RPDLY AS RIDGE OF HI PRES MOVS ACRS THE
AREA THIS MRNG. WINDS WILL REMAIN FAIRLY LGT TDA...BUT WITH TEMPS
BLO ZERO OVER THE CWA AND WCI'S -15 TO -25 WILL KEEP THE WIND CHILL
ADVY GOING THRU THE EARLY MRNG HRS. AREAS OF CLOUDS SWEEPING OUT OF
MT INTO ND AND SD THIS MRNG WILL BRUSH THE NRN THIRD OF THE CWA. DO
NOT XPCT TO SEE PCPN WITH THIS BEYOND A FEW FLURRIES AS SOUNDINGS
ARE QUITE DRY AS SYS MINORS OUT AS IT PROGRESSES EWD. CUT MOS TEMPS
TDA DUE TO EXTENSIVE SNOW COVER. TYPICALLY IN THESE STTNS WRMG IS
LMGT TO ABT 6 DEG OR SO. WITH SOME WAA AHEAD OF APCHG S/WV...WILL
ALLOW FOR RISES CLOSER TO 15 FROM THE AM MINS.
.LONG TERM /TONIGHT THROUGH TUESDAY/...
COLD AIR IN PLACE NOW WILL SLOWLY BE DISPLACED BY A GRADUAL RETURN
TO MORE ZONAL FLOW IN THE NEXT 36 TO 60 HOURS. TONIGHTS COLDEST AIR
HAS MOVED INTO THE PLAINS AND ALREADY SOME WARMING TAKING PLACE IN
MT WHERE TEMPS YESTERDAY WERE CLOSE TO -20F AS COMPARED TO 5F
TONIGHT. ALONG WITH THAT SOME LEE SIDE TROUGHING COMMENCES BY FRIDAY
WHICH ALLOWS SOUTHERLY WINDS TO INCREASE ACROSS THE REGION. TEMPS
THU NIGHT TO MODERATE FROM LOWS OF THIS MORNING. SOME CLOUDS AND
LIGHT SOUTH WINDS WILL HELP PREVENT LOWS FROM BOTTOMING OUT TOO LOW.
UNTIL THEN VERY COLD TEMPERATURES WILL BE THE RULE FOR NOW WITH SOME
CLOUDS AND WEAK IMPULSES TRACKING SOUTHEAST IN THE NEXT 24 TO 30
HOURS. BOTH AT H850 AND TO A LESSER EXTENT AT H700...A THERMAL
GRADIENT BEGINS TO APPEAR OVER THE NORTHERN PLAINS. THIS ALLOWS FOR
MID TO HIGH LEVEL CLOUDS TO FORM ALONG WITH THE POTENTIAL FOR SOME
LOW CONFIDENCE LIGHT PRECIP. FOR NOW WILL NOT INCLUDE ANY POP
THROUGH FRIDAY. WITH A CONTINUATION OF LEE SIDE TROUGHING INTO THE
WEEKEND...A STRONGER SOUTHERN STREAM UPPER LEVEL WAVE BEGINS TO
DEVELOP AS A NORTHERN STREAM SFC LOW ALSO DEVELOPS. THE COMBINATION
OF A SFC WARM FRONT...UPPER LEVEL FEATURE AND RETURN OF SOME
MOISTURE SUGGESTS THAT CLOUD COVER AND A PERIOD OF FREEZING DRIZZLE
OR LIGHT SNOW WILL BREAK OUT SAT EVENING AND CONTINUE SAT NIGHT OVER
THE EAST SECTIONS OF THE FORECAST AREA. THOUGH MODELS ATTM ARE
AGGRESSIVE WITH .20 TO .30 QPF...WILL NOT GET TOO EXCITED ABOUT
POTENTIAL SNOW ACCUMS FOR NOW. OTHER CHALLENGES WILL BE THE
FORMATION OF FOG. CURRENT DEEP SNOW COVER HERE AND LACK OF SNOWCOVER
OVER SOUTHERN KS AND MO WILL RESULT IN QUICK RETURN OF ANY MILDER
AIR...BUT IT WILL OVERRUN THE SNOWPACK. LIGHT WINDS SAT NIGHT SHOULD
ALLOW FOR FOG TO DEVELOP AND CONTINUE INTO SUNDAY. BEST PERIOD OF
FORMATION LOOKS TO BE SAT NIGHT. WITH STRONG WARM AIR ADVECTION OVER
THE REGION THROUGH SUN NIGHT CLOUDS AND SOME FOG SHOULD REMAIN.
ARCTIC FRONT TO ARRIVE ON MONDAY WITH NORTHERN STREAM WAVE WILL
USHER IN COLDER AIR AND THE RETURN OF BELOW NORMAL TEMPS. THIS WILL
LAST THROUGH THE END OF THE FORECAST PERIOD THOUGH SOME MODERATION
IS EXPECTED BY WED.
&&
.AVIATION...
10/18Z...PRIMARILY VFR CONDITIONS ACRS TAF SITES DURING THE PERIOD.
A COUPLE OF UPPER LEVEL DISTURBANCES WILL PASS ACROSS THE STATE
TODAY AND TONIGHT. THE FIRST WILL BRING SCT CLOUD DEVELOPMENT OVER
NORTHERN IA AND MAY PRODUCE LOCALIZED MVFR CEILINGS AND FLURRIES TO
KMCW AND KALO. DUE TO ISOLATED COVERAGE OF MVFR CONDITIONS...DID NOT
INCLUDE IN FORECAST. ANOTHER DISTURBANCE WILL PASS ACROSS OVERNIGHT.
EXPECT VFR CONDITIONS TO PERSIST AS THIS SYSTEM PASSES THROUGH. HAVE
DIMINISHED POTENTIAL WIND GUSTS FOR THIS AFTERNOON WITH SNOW PACK
LIMITING MIXING TODAY.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL NOON TODAY FOR ENTIRE FORECAST AREA.
&&
$$
SHORT TERM...MS DEC 09
AVIATION...DONAVON
LONG TERM...REV
