Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 182021
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
321 PM CDT SAT OCT 18 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 253 PM CDT SAT OCT 18 2014

LITTLE IN THE WAY OF SENSIBLE WEATHER ANTICIPATED TONIGHT. STRONG
SUBSIDENCE IS ERODING CLOUDS OVER IA THIS AFTERNOON WITH LOW LEVEL
RIDGE CROSSING THE STATE. WEAK LOW LEVEL RETURN FLOW SHOULD THEN
DEVELOP OVERNIGHT AFTER ITS PASSAGE KEEPING TEMPS FROM FALLING TOO
MUCH. WEAK SHORT WAVE CROSSING THE DAKOTAS WILL INCREASE MID LEVEL
KINEMATIC FORCING THIS EVENING BUT WITH NOTHING MORE THAN SCATTERED
MID CLOUDS DUE TO LIMITED MOISTURE. WARM/THETA-E ADVECTION ALOFT
WILL FOLLOW AS WELL BUT WITH SIMILAR MOISTURE LIMITATIONS AND NIL
SENSIBLE REFLECTION.

.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 253 PM CDT SAT OCT 18 2014

HIGH PRESSURE WILL PUSH SE THROUGH THE DAY SUNDAY...WITH WEAK
FRONTAL BOUNDARY PUSHING IN BEHIND. MAIN CONCERN WITH FRONTAL
BOUNDARY WILL BE CLOUDS AND TEMPERATURES...WITH PRECIPITATION NOT
EXPECTED. TEMPERATURES WILL WARM THROUGH THE DAY AHEAD OF THE
BOUNDARY WITH GOOD SOUTHERLY FLOW...THOUGH GIVEN CLOUDS HAVE KEPT
TEMPERATURES DOWN SOMEWHAT. IF CLOUDS ARE LESS THAN
EXPECTED...TEMPERATURES COULD BE WARMER. BEHIND
BOUNDARY...TEMPERATURES WILL BE COOLER WITH HIGH PRESSURE
SHIFTING SOUTH SUNDAY NIGHT. HAVE DROPPED TEMPERATURES A FEW
DEGREES GIVEN AMOUNT OF DRY AIR WORKING IN AND LIGHTER WINDS.
SIMILAR TREND FOR MONDAY NIGHT AS WELL WITH CENTER OF HIGH PUSHING
SOUTH ACROSS NEBRASKA.

RIDGE BUILDS IN FOR MID WEEK AS SYSTEM PUSHES EAST WITH
TEMPERATURES WARMING. BEST CHANCE FOR PRECIPITATION WILL COME AS
UPPER LEVEL LOW PUSHES EAST FOR LATE IN THE WEEK. STILL
UNCERTAINTY IN TIMING ON SYSTEM. MODELS HAVE BEGUN TO SLOW DOWN
SLIGHTLY...WITH GFS MUCH SLOWER...BRINGING SYSTEM THROUGH LATE
THURSDAY. HAVE CONTINUED TO TREND TOWARDS ECMWF/GEM SOLUTION WITH
TIMING FOR NOW. HOWEVER...EASTERN EXTENT OF PRECIPITATION IS STILL
UNCERTAIN WITH DECENT DRY AIR AT MID LEVELS ACROSS CENTRAL AND
EASTERN IOWA. HAVE THEREFORE CUT BACK SLIGHTLY ON EXTENT OF CHANCE
POPS FOR THURSDAY. HOWEVER...LOWER CONFIDENCE IN MODEL HANDLING OF
SYSTEM AT THIS TEMPORAL DISTANCE. RIDGE EXPECTED TO BUILD IN AGAIN
BEHIND SYSTEM...WITH DRY AND WARMER CONDITIONS AGAIN EXPECTED FOR
WEEKEND.

&&

.AVIATION...18/12Z
ISSUED AT 700 AM CDT SAT OCT 18 2014

CLOUDS ARE BECOMING QUITE A FORECAST DILEMMA.  MVFR DECK WAS SLIDING
DOWN OUT OF MN OVERNIGHT AND BREAKING UP AS IT PROGRESSED INTO IA.
IT AS NOW FILLED BACK IN AND IS STEADILY PROGRESSING SOUTHWARD.
THERE APPEARS TO BE HOLES IN THE STRATUS BASED ON SATELLITE IMAGERY
AND MOISTURE PROFILES IN THE FORECAST SOUNDINGS ARE NOT IMPRESSIVE.
HOWEVER...I DO NOT BELIEVE THAT WE WILL SEE AS MUCH MIXING TODAY.  I
HAVE MVFR CONDITIONS MOVING INTO TAF LOCATIONS FROM N TO S THROUGH
THE MORNING BUT BREAKING UP AFTER 18Z.  SFC FLOW WILL BE NRLY AT 10-
15KTS BUT DIMINISH LATE AFTERNOON.  HIGH PRESSURE WILL SHIFT EAST
LATE IN THE TAF PERIOD AND WINDS WILL REMAIN LIGHT BUT SWITCH AROUND
TO THE SOUTH.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SHORT TERM...SMALL
LONG TERM...AWB
AVIATION...FAB



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