300
FXUS63 KDMX 091140 AAA
AFDDMX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
540 AM CST TUE FEB 9 2010
..UPDATED AVIATION DISCUSSION
SHORT TERM /TODAY/
DRY SLOT EXPECTED TO MOVE SOUTH AND EAST OF THE CWA BY AROUND 12Z OR
SHORTLY AFTERWORDS AS THE UPPER LOW AND INVERTED TROUGH BEGIN TO
PULL FURTHER AWAY FROM THE STATE. ONGOING BAND OF MODERATE SNOW WILL
CONTINUE TO SHIFT SOUTH AND WEST THROUGH THE DAY ACROSS THE WESTERN
EDGES OF THE CWA. KEPT WITH CURRENT HEADLINES AS WINDS WILL INCREASE
DURING THE REST OF THE MORNING AND LIMITED VISIBILITY IS ANTICIPATED
WITH THE BLOWING SNOW AND HEAVIER BANDS OF SNOW. WINDS THIS
AFTERNOON WILL BE THE STRONGEST AND WIDESPREAD THROUGHOUT THE CWA AS
CAA DEVELOPS BEHIND UPPER LOW. BUFR SOUNDINGS HAVE BEEN CONSISTENT
WITH THE MIXED LAYER WINDS AROUND 30KTS. IN ADDITION...STILL LOOKING
FOR ABOUT A 10-12MB DIFFERENCE IN SURFACE PRESSURE GRADIENT THIS
AFTERNOON. SO IT WILL BE TOUGH TO GET WIDESPREAD WHITE CONDITIONS
WITH WINDS NOT GUSTING MUCH OVER 30KTS THIS AFTERNOON.
WRAP-AROUND MOISTURE IN CONJUNCTION WITH WEAK TROWAL FEATURE AND
SUBTLE FN VECTOR DIVERGENCE KEEPS MODERATE SNOW BANDS GOING ACROSS
MUCH OF THE NORTHEAST CWA THROUGH THE EARLY AFTERNOON HOURS. THIS
MATCHES UP WELL WITH THE MAX OMEGA WITHIN THE DENDRITIC LAYER
THROUGH 18Z. FORCING QUICKLY DISSIPATES PAST 18Z OVER THE EAST...AND
HENCE LOWERED SNOW AMOUNTS/POPS THIS AFTERNOON...ESPECIALLY OVER THE
WESTERN CWA. THE 850MB TEMPS DIP DOWN INTO THE MID TEENS BELOW ZERO
WITHIN THE CAA...SO LIKELY WILL SEE TEMPS DROPPING DURING THE
AFTERNOON AND WIND CHILLS BELOW ZERO AT TIMES.
LONG TERM /WEDNESDAY THROUGH MONDAY/
SNOW WILL LINGER OVER THE FAR EAST EARLY THIS EVENING WITH DEDRETIC
TEMPERATURES REMAINING IN THE LOW LEVEL SATURATED LAYER. TIME HEIGHT
CROSS SECTIONS AT ALO AND OTM SHOW FORCING ENDING BETWEEN 22Z AND
00Z THIS AFTERNOON WITH SUBSIDENCE TAKING OVER AFTER 00Z.
THEREFORE...THE ACCUMULATING SNOWFALL SHOULD BE ALMOST OVER BY 6 PM
THOUGH SOME VERY LIGHT ACCUMULATIONS MAY OCCUR OVER THE FAR EAST DUE
TO PROCESS MENTIONED ABOVE WITH A FEW DENDRITES BEING PRODUCED IN
THE LOW LEVELS BEFORE THE DRIER AIR AND SUBSIDENCE PREVAIL. LOW
TEMPERATURES TUE NIGHT REMAIN PROBLEMATIC PENDING CLOUD COVER AND
1000-850MB THICKNESSES THAT RECOVER ON TUE FROM THE CURRENT MINIMUM
MOVING OVER SW IA. QUIET WED AND WED NIGHT WITH HIGH PRESSURE
TRANSVERSING EAST OVER THE STATE. ONCE AGAIN OVERNIGHT LOWS WILL BE
PROBLEMATIC WITH WARM ADVECTION CLOUD COVER TRYING TO IMMEDIATELY
FOLLOW THE SFC RIDGE LOCATION. EXPECT COLDEST IN THE EAST WITH SOME
RECOVERY LATE OVER THE WEST WITH A FEW CLOUDS AND LIGHT SLY WINDS
DEVELOPING.
HAVE ADDED LOW POPS TO THU AND THU NIGHT. CURRENTLY HAVE LIGHT SNOW
MENTION IN THE GRIDS HOWEVER...MAY NOT GET ICE INTRODUCED INTO THE
LOW LEVELS. A FEW FACTORS TO CONSIDER IS THE HINT AT A MID LEVEL
CLOUD DECK MOVING OVERHEAD TO SEED TO LOW LEVELS. ALSO SOME -8C TO
-10C TEMPS NEARING THE TOP OF THE SATURATED LAYER WHICH MAY
INTRODUCE ICE. CHOOSE TO STAY ALL SNOW FOR NOW DUE TO UNCERTAINTY
INSTEAD OF INTRODUCING FREEZING DRIZZLE. THE NEXT WAVE SHOULD ARRIVE
ON FRIDAY AND HAVE CONTINUED LOW POPS THOUGH EXPECT POPS WILL NEED
TO BE INCREASED IF TRENDS PERSIST.
A STRONGER SYSTEM IS DUE TO AFFECT THE MIDWEST THIS WEEKEND WITH A
CLOSED 500 MB LOW PROGGED. SOME TIMING AND PLACEMENT ISSUES REMAIN
THOUGH SATURDAY AND SATURDAY NIGHT ARE TARGETED AT THIS TIME.
SATURDAY IS JUST BEYOND THIS FORECASTS UPDATE PERIOD...THUS NO POPS
ADDED YET THOUGH EXPECT POPS TO BE ADDED SOON.
AVIATION
09/12Z...INVERTED TROUGH SEPARATING GUSTY NORTH WINDS ACROSS
NORTHERN IOWA...WHERE ALO REMAINS LIGHT WHILE MCW NEAR 15KTS ATTM.
BAND OF SNOW WILL CONTINUE TO SHIFT SOUTH...IFR VIS WITHIN BAND AND
LOOKS TO REACH DSM TAF SIT BY 14Z OR SHORTLY AFTER. EXPECTING STRONG
WINDS TO INCREASE LATE THIS MORNING WITH BLSN AND FALLING TO CAUSE
IFR/LIFR VIS THROUGH THE AFTERNOON HOURS. STRONGEST WINDS LOOK TO
RELAX LATE THIS EVENING...WITH MVFR CIGS PERSISTING TOWARDS
WEDNESDAY MORNING.
DMX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY UNTIL 6 PM CST TODAY FOR APPANOOSE-
BOONE-CALHOUN-DALLAS-DAVIS-GREENE-LUCAS-MONROE-PALO ALTO-
POCAHONTAS-POLK-WAPELLO-WARREN-WAYNE.
WINTER WEATHER ADVISORY FROM 3 AM TO 6 PM CST TODAY FOR ADAIR-
AUDUBON-CARROLL-CASS-CRAWFORD-GUTHRIE-MADISON-SAC.
WINTER STORM WARNING UNTIL 6 PM CST TODAY FOR BLACK HAWK-
BREMER-BUTLER-CERRO GORDO-EMMET-FRANKLIN-GRUNDY-HAMILTON-HANCOCK-
HARDIN-HUMBOLDT-JASPER-KOSSUTH-MAHASKA-MARION-MARSHALL-POWESHIEK-
STORY-TAMA-WEBSTER-WINNEBAGO-WORTH-WRIGHT.
WINTER WEATHER ADVISORY FROM 9 AM TO 6 PM CST TODAY FOR CLARKE-
DECATUR.
SHORT TERM...PODRAZIK
LONG TERM...DONAVON
AVIATION...PODRAZIK
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