Area Forecast Discussion
Issued by NWS Des Moines, IA

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KDMX 061140
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
540 AM CST SAT FEB 6 2016

...UPDATED FOR 12Z AVIATION DISCUSSION...

.SHORT TERM /TODAY/...
ISSUED AT 349 AM CST SAT FEB 6 2016

RATHER BENIGN SHORT TERM FCST IN TERMS OF SENSIBLE WX. AT 06Z
SAT...SFC TROUGH PASSING OVER CWA. FREEZING FOG OVER SIOUX FALLS CWA
SLOWLY ADVECTING EASTWARD. GIVEN VSBY FIELD AND CURRENT RATE OF
ADVECTION AT 06Z SAT...FOG MAY CLIP OUR NW TO NORTHERN CWA BY
SUNRISE...BUT VSBY NOT EXPECTED TO DROP MUCH BELOW 2 TO 3 SM FOR
ANY PROLONGED PERIOD OF TIME. FCST SOUNDINGS SHOW SOLID INVERSION
PERSISTING THROUGH SATURDAY...EVEN INTO SUNDAY MORNING ACROSS THE
NORTHERN TO NORTHEASTERN CWA. HAVE BUMPED UP CLOUD COVER AND
MODERATED DAYTIME "HEATING" SLIGHTLY AS A RESULT. 850MB TEMPS ON FRI
WERE IN THE -4C TO -7C RANGE. FOR SAT... 850MB TEMPS -1C TO -3C SO
SAT MAX TEMPS 5 TO 10 DEGREES WARMER FOR SAT VS FRI SEEMS
REASONABLE.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 349 AM CST SAT FEB 6 2016

THE LONG TERM FORECAST IS PUNCTUATED BY THE POTENTIAL FOR
BLIZZARD CONDITIONS ACROSS NORTHERN IOWA FROM SUNDAY AFTERNOON
THROUGH MONDAY MORNING.

AT 500 MB...A ROBUST SHORTWAVE TROUGH WILL SWEEP ACROSS THE
DAKOTAS AND MINNESOTA ON SATURDAY NIGHT...PROBABLY CLOSING OFF AS
A LOW CENTERED OVER NORTHERN MINNESOTA BY SUNDAY MORNING.
SUBSEQUENT REINFORCING SHORTWAVES WILL EXPAND THIS LOW INTO A
LARGE GYRE OVER THE GREAT LAKES WITH A DEEP LONGWAVE TROUGH
CARVING OUT ACROSS THE ENTIRE EASTERN HALF OF THE CONUS FOR THE
FIRST HALF OF THE WORK WEEK. A WESTERN U.S. RIDGE FORMING IN
RESPONSE WILL EVENTUALLY WORK ITS WAY EASTWARD TOWARD OUR REGION
AROUND THE END OF NEXT WEEK.

IN THE LOWER LEVELS AND AT THE SURFACE...SOUTHWEST FLOW AND WEAK
RIDGING THIS EVENING WILL KEEP THINGS PRETTY MILD AND DRY TONIGHT.
ON SUNDAY A SURFACE LOW PRESSURE CENTER WILL DEVELOP RAPIDLY
ACROSS NORTHERN MINNESOTA IN RESPONSE TO THE STRENGTHENING UPPER
LEVEL SYSTEM...WITH ITS ATTENDANT TROUGH SWEEPING FROM NORTHWEST
TO SOUTHEAST ACROSS IOWA AROUND SUNDAY AFTERNOON AND EVENING. A
STRONG SURFACE PRESSURE GRADIENT COUPLED WITH INTENSE WINDS ALOFT
AND THE DEVELOPMENT OF A SEASONALLY DEEP MIXED LAYER WILL PROMOTE
A SIGNIFICANT INCREASE IN WINDS AS THE TROUGH MOVES THROUGH. BY 6
PM SUNDAY FORECAST SOUNDINGS FOR MASON CITY FROM BOTH THE GFS AND
NAM INDICATE A MIXED LAYER EXTENDING UP TO NEARLY 800 MB WITH
WINDS AT THE TOP BLOWING AT 45 TO 50 KT. GIVEN THE FORCING
ASSOCIATED WITH THE UPPER LEVEL SYSTEM AND THE MEAGER BUT
POSITIVE INSTABILITY ASSOCIATED WITH THE FORECAST SOUNDINGS...IT
IS LIKELY THAT WE WILL SEE A SCENARIO IN WHICH SNOW SHOWERS FORM
WITHIN AND ENVIRONMENT CHARACTERIZED BY DEEP AND TURBULENT
BOUNDARY LAYER MIXING. COMBINED WITH THE DEEP SNOW PACK IN PLACE
ACROSS NORTHERN IOWA...GENERALLY AVERAGING BETWEEN 7 AND 14
INCHES...THIS CREATES AN IDEAL SET UP FOR BLIZZARD CONDITIONS AND
THE BLIZZARD WATCH REMAINS IN EFFECT. IN FACT THE WATCH HAS BEEN
EXPANDED INTO FIVE MORE NORTHERN IOWA COUNTIES WHERE A DEEP SNOW
PACK ALSO EXISTS...AND ALSO EXTENDED THROUGH NOON MONDAY AS IT
APPEARS THERE WILL BE LINGERING SNOWFALL ON MONDAY MORNING ALONG
WITH WHAT COULD BE THE STRONGEST WINDS OF THE ENTIRE EVENT. IN
SHORT...TRAVEL CONDITIONS WILL BECOME VERY HAZARDOUS ONCE THE
STRONG WINDS AND SNOW SHOWERS BEGIN LATE SUNDAY.

BY MONDAY AFTERNOON AND EVENING THE SNOW WILL DEPART AND WINDS
WILL DIMINISH AS THE LARGE STACKED LOW PRESSURE SYSTEM MOVES OFF
OVER THE GREAT LAKES. THE REMAINDER OF THE FORECAST IS THEN
GENERALLY QUIET. A WEAKER AND QUICK MOVING SYSTEM MAY PRODUCE
SOME LIGHT SNOW OVER PARTS OF IOWA ON WEDNESDAY...BUT SOLUTIONS
FOR THAT SYSTEM ARE CONTINGENT ON THE EVOLUTION OF THE EARLIER
WEEK STORM...AND IN ANY EVENT IT DOES NOT APPEAR THAT ANY
SIGNIFICANT ACCUMULATION IS LIKELY AND WINDS WILL BE FAIRLY WEAK
AROUND WEDNESDAY SO NO HAZARDOUS IMPACTS ARE ANTICIPATED AT THIS
TIME.

&&

.AVIATION...06/12Z
ISSUED AT 535 AM CST SAT FEB 6 2016

CURRENT CIGS AND VSBYS SHOULD EFFECTIVELY HOLD THROUGH SAT
MORNING. REMOVED WIDEPSREAD LIFR WORDING FROM PVS TAF PACKAGE.
GRADUAL VFR FROM KFOD TO KDSM AND TO KOTM MAY NEED TWEAKING ON
TIMING. KEPT KALO AND KMCW OUT OF VFR. KALO AND KMCW WILL LIKELY
NEED AT LEAST IFR SUNDAY NIGHT AS BLOWING SNOW VERY POSSIBLE.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WATCH FROM SUNDAY AFTERNOON THROUGH MONDAY MORNING FOR
BOONE-BUTLER-CALHOUN-CARROLL-CERRO GORDO-EMMET-FRANKLIN-GREENE-
GRUNDY-HAMILTON-HANCOCK-HARDIN-HUMBOLDT-KOSSUTH-PALO ALTO-
POCAHONTAS-SAC-WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

$$

SHORT TERM...KOTENBERG
LONG TERM...LEE
AVIATION...KOTENBERG


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.