Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 081813
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1213 PM CST MON FEB 8 2016

.UPDATE...
ISSUED AT 1011 AM CST MON FEB 8 2016

ALL HEADLINES HAVE BEEN EXTENDED TO END TIME OF 00Z TO BLEND INTO
THINKING OF ADJACENT OFFICES FOR CONSISTENT MESSAGING. THE LATEST
HRRR AND RAP SUGGEST CONTRIBUTIONS OF ADDITIONAL SNOW WILL
DIMINISH DURING THE AFTERNOON...BUT STRONG GUSTY WINDS MAY STILL
BE SUFFICIENT FOR CONTINUE DRAMATIC VISIBILITY
RESTRICTIONS...ESPECIALLY IN RURAL OPEN AREAS.

&&

.SHORT TERM /TODAY/...
ISSUED AT 314 AM CST MON FEB 8 2016

TRICKY FORECAST CONTINUES FOR THE SHORT TERM...WITH GUSTY
NORTHWEST WINDS TO CONTINUE THROUGH THE DAY WITH INTERMITTENT SNOW
SHOWERS. STRONGEST PRESSURE RISES AND CAA COMING THROUGH NOW
TOWARD SUNRISE...WITH ISALLOBARIC COMPONENT OF WINDS EXPECTED TO
WEAKEN THROUGH THE DAY. STEEP LAPSE RATES ALOFT...WITH SATURATION
AND WEAK LIFT IN THE DENDRITIC LAYER TO KEEP THREAT FOR DECENT
SNOW SHOWERS GOING THROUGH THE DAY. NAM/GFS SEEM OVERDONE ON WINDS
WITH AROUND 50 TO 55 KTS AT THE TOP OF THE MIXED LAYER WINDS
THROUGH THE DAY...WITH THE SREF/RAP MUCH LESS AROUND 40-45KTS.
NAM/GFS INDICATING THAT THOSE HIGHER WINDS GUSTS ALREADY EXPECTED
TO BE PRESENT ACROSS THE CWA...AND CURRENTLY GETTING GUSTS TOPPING
OUT AROUND 45 TO 50 MPH. THEREFORE TRENDED WINDS DOWN A BIT
THROUGH THE DAY GOING CLOSER TO THE RAP/SREF VALUES. WITH THE
LOWERED WINDS...HAVING A HARD TIME GETTING MUCH VSBY REDUCTIONS
OUTSIDE OF THE SNOW SHOWERS...THEREFORE HAVE DOWNGRADED SOME OF
THE FRINGES OF THE BLIZZARD WARNING TO A WINTER WEATHER ADVISORY.
STILL SOME PARTIALLY COVERED/COMPLETELY COVERED ROADWAYS THAT ARE
SLICK DUE TO DRIFTING SNOW...BUT OVERALL VISIBILITIES/BLIZZARD
CONDITIONS NOT BEING REALIZED IN THE SOUTHERN MOST/EASTERN-MOST
AREAS OF THE WARNING. REMAINDER OF THE AREA GETTING REPORTS OF
TRAVEL NOT ADVISED AND CONSISTENT LOWERED VSBYS AT A FEW NORTHERN
LOCATIONS...SO WILL KEEP THE REST OF THE WARNING AS IS. ONLY OTHER
CHANGE WAS TO SHORTEN THE DURATION ON THE WESTERN SIDE OF THE
HEADLINES...WITH WINDS EXPECTED TO LOWER AND SNOW SHOWERS TO COME
TO AN END TOWARD MID AFTERNOON.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 314 AM CST MON FEB 8 2016

THE LONG TERM FORECAST IS PRETTY QUIET OVERALL. AT 500 MB A LARGE
GYRE WILL BE CARVED OUT OVER THE GREAT LAKES REGION WITH THE
ENTIRE EASTERN HALF OF THE CONUS LYING BENEATH ITS CYCLONIC FLOW
FOR THE NEXT FEW DAYS. AROUND THE END OF THE WORK WEEK...EVEN AS
THE ASSOCIATED WESTERN U.S. RIDGE ATTEMPTS TO ENCROACH UPON THE
MIDWEST...ANOTHER COMPACT BUT VIGOROUS SHORTWAVE WILL MOVE OVER OR
NEAR IOWA AND REINFORCE THE EASTERN GYRE...DELAYING ANY
SIGNIFICANT WARMING. FINALLY...AT THE END OF THE FORECAST
PERIOD...THE PATTERN SHOULD BREAK DOWN ALLOWING FOR THE RIDGE TO
MOVE EASTWARD.

IN TERMS OF LOWER LEVELS AND SENSIBLE WEATHER...THE SNOW SHOWERS
AND STRONG WINDS AFFECTING THE AREA TODAY SHOULD MOVE EASTWARD
TONIGHT...WITH LIGHT SNOW LIKELY ENDING IN OUR EAST BY MIDNIGHT.
NORTH NORTHWEST BREEZES WILL THEN PERSIST THROUGH TUESDAY NIGHT
BEFORE A SURFACE RIDGE SETTLES ACROSS IOWA...BRINGING LIGHT AND
VARIABLE WINDS ON WEDNESDAY AND WEDNESDAY NIGHT. THE COLDEST
TEMPERATURES WITHIN THIS REGIME WILL LIKELY COME ON WEDNESDAY
MORNING WITH WIND CHILLS GETTING DOWN TO 10 TO 15 BELOW ZERO IN
OUR NORTHERN AND NORTHEASTERN COUNTIES. MEANWHILE VARIOUS MODEL
SOLUTIONS HAVE BEEN DEPICTING A ZONE OF WEAK FRONTOGENETICAL
FORCING ALOFT MOVING OVER THE AREA AROUND WEDNESDAY OR WEDNESDAY
NIGHT AND POSSIBLY PRODUCING LIGHT SNOWFALL...HOWEVER THESE
SOLUTIONS HAVE BEEN HIGHLY VARIABLE IN TIME AND SPACE OVER THE
LAST FEW DAYS SO CONFIDENCE IS LOW. IN ADDITION...WITH THE SURFACE
HIGH DRAPED ACROSS IOWA DURING THAT TIME FRAME FORECAST SOUNDINGS
INDICATE LOW LEVEL DRY AIR THAT WOULD INHIBIT ANY MEANINGFUL
PRECIPITATION. THEREFORE HAVE KEPT THE FORECAST DRY FOR NOW.

A BETTER CHANCE FOR PRECIPITATION MAY COME AROUND FRIDAY WHEN THE
AFOREMENTIONED VIGOROUS SHORTWAVE MOVES OVER THE REGION.
HOWEVER...ONCE AGAIN THERE IS A LOT OF RUN TO RUN VARIABILITY IN
THE LOCATION AND TIMING OF ANY RESULTING PRECIPITATION. IF THE
PROGNOSTIC MODELS ARE ABLE TO CONVERGE ON A SOLUTION THEN IT IS
POSSIBLE THAT WE COULD SEE SOME ACCUMULATING SNOWFALL AT THE END
OF THE WORK WEEK....PROBABLY FOLLOWED BY MORE COOL AIR TO BEGIN
THE WEEKEND. FINALLY...AT THE END OF THE FORECAST...THE DEEP LAYER
RIDGE MOVING EASTWARD SHOULD BRING A RETURN OF SOMEWHAT MILDER
WEATHER TOWARD SUNDAY AND MONDAY OF NEXT WEEK.

&&

.AVIATION...08/18Z
ISSUED AT 1212 PM CST MON FEB 8 2016

MAINLY MVFR/IFR CONDITIONS ACROSS CENTRAL IA DUE TO CLOUDS AND
VISIBILITY RESTRICTIONS IN SNOW SHOWERS AND BLOWING SNOW. LITTLE
CHANGE IS ANTICIPATED INTO THE AFTERNOON...BUT VERY GRADUAL
IMPROVEMENT SHOULD OCCUR BY THE LATE AFTERNOON AND EARLY EVENING
HOURS AS CONTRIBUTIONS OF SNOW SHOWERS BEGIN TO WANE. AT LEAST
MVFR STRATUS AND/OR BLOWING SNOW IS EXPECTED TO LINGER INTO TUE
MORNING IN MOST LOCATIONS. WINDS WILL ONLY SLOWLY DECREASE THROUGH
THE PERIOD BUT REMAIN BRISK.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR ADAIR-
ADAMS-AUDUBON-BLACK HAWK-BREMER-CASS-CLARKE-DALLAS-DECATUR-
GUTHRIE-JASPER-MADISON-MARSHALL-POLK-POWESHIEK-RINGGOLD-STORY-
TAMA-TAYLOR-UNION.

BLIZZARD WARNING UNTIL 6 PM CST THIS EVENING FOR BOONE-BUTLER-
CALHOUN-CARROLL-CERRO GORDO-CRAWFORD-EMMET-FRANKLIN-GREENE-
GRUNDY-HAMILTON-HANCOCK-HARDIN-HUMBOLDT-KOSSUTH-PALO ALTO-
POCAHONTAS-SAC-WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

$$

UPDATE...SMALL
SHORT TERM...BEERENDS
LONG TERM...LEE
AVIATION...SMALL


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