Area Forecast Discussion
Issued by NWS Des Moines, IA

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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 011924
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
124 PM CST MON FEB 1 2016

.UPDATE...
ISSUED AT 121 PM CST MON FEB 1 2016

STILL SEEING AREAS OF FOG IN THE FAR EAST...ALTHOUGH VISIBILITY
SHOULD GRADUALLY IMPROVE THIS AFTERNOON. DENSE FOG ADVISORY RUNS
THROUGH 21Z...AND MIGHT BE ABLE TO CANCEL EARLY BASED ON RECENT
OBSERVATIONAL TRENDS.

UPDATED 18Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM /TODAY/...
ISSUED AT 508 AM CST MON FEB 1 2016

AREAS OF FOG HAVE DEVELOPED OVER NORTH CENTRAL AND EASTERN IOWA
THIS MORNING AS WEAK SFC HIGH PRESSURE LIFTS NORTH ACROSS THE
STATE. HIRES SOLUTIONS SUGGESTING THAT THE STRATUS AND FOG WILL
EXPAND BACK WEST INTO CENTRAL IA THIS MORNING THEN LINGER OVER THE
NORTHERN PORTION OF IOWA INTO THE AFTERNOON. THESE SOLUTIONS ARE
CURRENTLY TOO AGGRESSIVE OVER CENTRAL IOWA. WILL NEED TO MONITOR
NORTH CENTRAL IOWA WHERE A FEW SITES HAVE DROPPED TO ONE QUARTER
MILE. POSSIBLE A DENSE FOG ADVISORY MAY BE REQUIRED.

PRECIPITATION CHANCES WILL BEGIN TO INCREASE BY LATE THIS AFTERNOON
AS THE WINTER STORM APPROACHES THE AREA FROM THE SOUTHWEST. THE
INITIAL WAVE OF THETA-E ADVECTION CENTERED NEAR 750 MB AND
ISENTROPIC LIFT WILL BEGIN TO ARRIVE OVER SOUTHWEST IOWA BY LATE
THIS AFTERNOON. A PERIOD OF SATURATION WILL NEED TO OCCUR DUE TO
DRY AIR LEFT BY THE DEPARTING HIGH BUT SOME LIGHT PRECIPITATION IS
POSSIBLE BY 00Z. GENERALLY A MIX OF RAIN OR SNOW IS POSSIBLE AS
TEMPERATURES ALOFT BEGIN TO COOL TOWARD WETBULB TEMPERATURES
THROUGH EVAPORATIVE COOLING AND SATURATION.

ANOTHER DIFFICULT HIGH TEMPERATURE FORECAST TODAY DUE TO THE
LINGERING STRATUS AND FOG THEN THE INCREASING CLOUDS FROM SOUTH TO
NORTH BY THE AFTERNOON. HAVE REMAINED COOLER THAN GUIDANCE DUE
TO LIMITED SUN ESPECIALLY BY NOON TODAY.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 508 AM CST MON FEB 1 2016

BLIZZARD/WINTER STORM STILL ON TRACK BEGINNING PAST 06Z TONIGHT
THROUGH MUCH OF THE DAY TUESDAY INTO TUESDAY EVENING. GREATEST
SNOWFALL RATES WILL BE TUESDAY MORNING FOLLOWED BY THE HIGHEST
WIND GUSTS BY THE AFTERNOON TUESDAY. UPGRADED WATCHES TO EITHER
BLIZZARD OR WINTER STORM WARNING FOR THE CENTRAL TO NORTHWEST.

MODELS HAVE CONTINUED TO GRADUALLY SHIFT THE HEAVIEST SNOW BAND
FURTHER WEST-NORTHWEST...MAINLY AFFECTING THE SOUTH TO SOUTHEAST
SECTIONS OF THE FORECAST AREA. OVERALL...LITTLE CHANGES TO THE
ONGOING HEAVY BAND OF SNOW FROM SOUTHWEST TO NORTHEAST PORTIONS OF
THE CWA. MODELS ARE AT LEAST IN BETTER AGREEMENT WITH THE SURFACE
LOW TRACK...THOUGH THERE REMAIN SUBTLE DIFFERENCES WRT TO THE
UPPER LOW. THAN NAM WANTS TO PLACE IT OVER SW MISSOURI WHILE THE
ECMWF/GFS AND EVEN THE SREF PLACE IT SLIGHTLY FURTHER WEST INTO SE
NEBRASKA/NE KANSAS. REGARDLESS...UTILIZED A BLEND OF THE
NAM/SREF/ECMWF/GFS FOR QPF/TEMPS/POPS.

TONIGHT INTO WEDNESDAY...CURRENTLY THE ROBUST WAVE IS CHURNING OVER
THE SOUTHWEST CONUS AND WILL RAPIDLY MOVE EAST ACROSS THE SOUTHERN
ROCKIES TODAY. IT WILL THEN TRACK ACROSS THE TX/OK PANHANDLES AND
INTO KANSAS PLACING THE SURFACE LOW IN EASTERN KANSAS BY AROUND 12Z
TUESDAY. TREMENDOUS AMOUNT OF ISENTROPIC LIFT...THETA-E ADVECTION
AND WAA ALOFT AHEAD OF THE LOW TONIGHT INTO TUESDAY MORNING. THE
850MB FRONT SETS UP ROUGHLY ALONG HIGHWAY 34 OR SLIGHTLY FURTHER
SOUTH (MORE ON THIS BELOW).

SOUNDINGS QUICKLY BECOME DEEPLY SATURATED B/T 03-06Z OVER
SOUTHWEST IOWA AND B/T 06-09Z FURTHER NORTH. VERY POTENT 300MB JET
PLACES IOWA IN THE LEFT EXIT REGION PROVIDING PLENTY OF DIVERGENCE
ALOFT AND UPWARD VERTICAL MOTION ACROSS THE STATE BETWEEN 06-18Z
TUESDAY. ONE OTHER THING TO NOTE...SOUNDINGS DO SUGGEST AN ABOVE
FREEZING LAYER NEAR THE SURFACE TONIGHT BUT THE FORCING WITHIN THE
DGZ IS STRONG ENOUGH TO COOL THE COLUMN AND KEEP PRECIP ALL SNOW
FOR SOUTHWEST TO CENTRAL PORTIONS OF IOWA. THE BEST CROSS SECTION
TO SHOW THE SIGNIFICANT NEGATIVE EPV AND THETA-E DECREASING WITH
HEIGHT EXTENDS FROM NW IOWA TO NE MISSOURI. LARGE CROSS HAIR OF
OMEGA WITHIN THE DGZ B/T 09-15Z WITH STRONG FRONTOGENETICAL
FORCING B/T 600-650MB AS WELL AS B/T 700-750MB SHOULD LEAD TO
HEAVY BANDED SNOW DURING THIS TIME IN THE WARNING AREAS. PLUS WITH
THE AFOREMENTIONED LARGE SCALE UVM...700-500MB LAPSE RATES MUCAPE
VALUES RANGE FROM 6.0 TO 7.5 C/KM AND 50-100 MB RESPECTIVELY. THIS
IS LIKELY ENOUGH TO RELEASE CSI AND CAUSE SOME BRIEF STINTS OF
THUNDERSNOW TUESDAY MORNING. ALTHOUGH A WIDESPREAD 6-12 INCH BAND
IS ANTICIPATED...EXPECTING SOME ISOLATED SPOTS TO SEE NEAR 15
WITHIN THE TSSN REGION. THIS ROUGHLY FROM DES MOINES TO CARROLL
EAST-NORTHEAST THROUGH AMES TO IOWA FALLS/MARSHALLTOWN...AND MAYBE
AS FAR EAST AS WATERLOO. EXPECTING SNOWFALL RATES FROM 1-2 INCHES
WITH OVER 3 INCH PER HOUR RATES POSSIBLE TUESDAY MORNING.

A VERY SHARP GRADIENT WILL SET UP FOR SNOW AMOUNTS AS DRY SLOT
PUNCHES INTO SOUTH-CENTRAL TO SOUTHEAST IOWA BY LATE TUESDAY MORNING
INTO THE AFTERNOON...WHICH SHOULD CUT DOWN ON SNOW RATIOS.
ALSO...DEPENDING ON WHICH MODEL...THE RAIN/SNOW OR ROUGHLY THE 0C
850MB LINE LOOKS TO ORIENT ITSELF FROM NEAR LAMONI TO MOUNT AYR
NORTHEAST TO INDIANOLA THEN TOWARD CEDAR RAPIDS BY MIDDAY TUESDAY.
EXPECTING A BREAK IN THE PRECIP...OR AT LEAST A SIGNIFICANT DECREASE
IN INTENSITY OVER THE SOUTHEAST TUESDAY AFTERNOON. THUS...LOWERED
POPS AND SNOW AMOUNTS IN THIS AREA.

TIGHT PRESSURE GRADIENT (ROUGHLY 18 MB DIFFERENCE ACROSS THE STATE)
AND WINDS ATOP THE MIXED LAYER INCREASE TO 30-40 KNOTS DURING THE
AFTERNOON HOURS TUESDAY. ALTHOUGH THE HEAVIEST SNOW WILL DECREASE IN
INTENSITY DURING THE AFTERNOON HOURS...THERE STILL WILL BE SNOW
FALLING WITH THE STRONG WINDS. NOT CONVINCED THE WINDS WILL BE
STRONG ENOUGH FURTHER SOUTH...SO LEANED TOWARD THE WINTER STORM
WARNING INSTEAD.

THE CAA CONTINUES THROUGHOUT THE DAY WEDNESDAY AND THE PATCHY
BLOWING SNOW MAY CONTINUE OVER NORTHERN IOWA. HIGH PRESSURE SETTLES
INTO THE REGION AND LOOKS TO PROVIDE A DECENT RADIATIONAL COOLING
NIGHT WEDNESDAY NIGHT INTO THURSDAY. WITH THE FRESH SNOW PACK IN
PLACE...FELT CONFIDENT ENOUGH TO COOL MINIMUM TEMPERATURES DURING
THIS TIME.

THURSDAY THROUGH SUNDAY...NO MAJOR CONCERNS DURING THIS PERIOD WITH
TEMPERATURES RANGING NEAR NORMAL WITH DRY CONDITIONS.

&&

.AVIATION...01/18Z
ISSUED AT 121 PM CST MON FEB 1 2016

FOG CONTINUES TO LINGER AT KALO AND KOTM...BUT EXPECT VISIBILITY
TO IMPROVE BY 20-21Z. VFR CONDITIONS ARE THEN EXPECTED FOR
ALL TERMINALS THOUGH THE EVENING HOURS.

MAJOR STORM SYSTEM WILL BEGIN TO IMPACT THE AIRFIELDS AFTER ABOUT 04Z
TONIGHT. EXPECT MVFR CIGS AND VSBYS ASSOCIATED WITH LIGHT SNOW TO
SPREAD FROM WEST TO EAST WITH CONDITIONS DETERIORATING TO
IFR BETWEEN 09Z AND 12Z. MODERATE TO HEAVY SNOWFALL WITH VSBYS
AOB 1/2SM SHOULD IMPACT MOST AIRFIELD BETWEEN 12-18Z.
CORRESPONDING CIGS WILL RANGE FROM IFR TO LIFR. SNOWFALL RATES
WILL LIKELY APPROACH 1 INCH PER HOUR AT TIMES CHALLENGING
RUNWAY MAINTENANCE. COULD SEE MORE OF A RAIN/SNOW MIX AT KOTM DUE
TO WARMER CONDITIONS NEAR THE SURFACE.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 AM CST WEDNESDAY
FOR ADAIR-ADAMS-AUDUBON-BOONE-CASS-DALLAS-GUTHRIE-MADISON-POLK.

WINTER WEATHER ADVISORY FROM 3 AM TUESDAY TO 6 AM CST WEDNESDAY
FOR JASPER-POWESHIEK-TAMA.

DENSE FOG ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR APPANOOSE-
BLACK HAWK-BREMER-BUTLER-DAVIS-GRUNDY-JASPER-MAHASKA-MARSHALL-
MONROE-POWESHIEK-TAMA-WAPELLO.

BLIZZARD WARNING FROM 3 AM TUESDAY TO 6 AM CST WEDNESDAY FOR
CERRO GORDO-EMMET-FRANKLIN-HAMILTON-HANCOCK-HUMBOLDT-KOSSUTH-
PALO ALTO-WINNEBAGO-WORTH-WRIGHT.

WINTER STORM WARNING FROM 3 AM TUESDAY TO 6 AM CST WEDNESDAY FOR
BLACK HAWK-BREMER-BUTLER-GRUNDY-HARDIN-MARSHALL-STORY.

BLIZZARD WARNING FROM MIDNIGHT TONIGHT TO 6 AM CST WEDNESDAY FOR
CALHOUN-CARROLL-CRAWFORD-GREENE-POCAHONTAS-SAC-WEBSTER.

&&

$$

UPDATE...FOWLE
SHORT TERM...DONAVON
LONG TERM...PODRAZIK
AVIATION...FOWLE


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