Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 221804
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1204 PM CST THU JAN 22 2015

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND FRIDAY
ISSUED AT 347 AM CST THU JAN 22 2015

SKY COVER AND TEMPERATURES TODAY AND TONIGHT...AND PCPN TRENDS AND
TYPE ON FRIDAY...ARE THE MAIN FCST CONCERNS.

STRATOCUMULUS CLOUDS COVERED MOST OF THE FORECAST AREA EARLY THIS
MORNING. A SFC RIDGE WAS SITUATED FROM THE MN ARROWHEAD SWWD INTO
THE CENTRAL PLAINS. PARTIAL CLEARING WAS NOTED NEAR THE RIDGE
AXIS IN MN.

MODELS ARE FAIRLY AGGRESSIVE WITH LOW-LEVEL DRYING OVER NORTHERN WI
THIS MORNING...AS THE SFC RIDGE BUILDS INTO THE REGION AND THE H8
THERMAL TROF SHIFTS EAST. HOWEVER...SATELLITE SHOWS SEVERAL LARGE
PATCHES OF LOW CLOUDS UPSTREAM...SO WIDESPREAD CLEARING SEEMS
UNLIKELY. BASED ON SATL AND COORD WITH NEIGHBORING OFFICES...HAVE
GONE WITH A MORE GRADUAL CLEARING TREND DURING THE DAY. HIGH TEMPS
SHOULD REACH 25 TO 30 DEGREES IN MOST PLACES...BUT MAY NEED TO BE
RAISED A FEW DEGREES IF MORE SUBSTANTIAL CLEARING OCCURS.

WAA WILL BRING AN INCREASE IN CLOUDS TO NORTHERN WI DURING THE LATE
EVENING AND OVERNIGHT...BUT PCPN SHOULD REMAIN NORTH OF THE REGION
UNTIL FRIDAY MORNING. MOST PLACES SHOULD HAVE LOW TEMPS IN THE
UPPER TEENS AND LOWER 20S TONIGHT.

AN UPPER TROF...RRQ OF AN UPPER LEVEL JET STREAK AND WEAK COLD
FRONT WILL BRING A CHANCE OF PCPN TO THE REGION ON FRIDAY. MODELS
HAVE SOME DIFFERENCES IN MOISTURE TRENDS...BUT GENERALLY AGREE
THAT THE HIGHEST QPF WILL OCCUR OVER NC/NE WI. MODELS ALSO SHOW
A WEAK WARM LAYER (0 TO +2 C)...WHICH IS MOST PRONOUNCED AND A BIT
WARMER ON THE NAM MODEL. MOST LIKELY PCPN TYPES WOULD APPEAR TO BE
SNOW/SLEET AT THIS TIME. WARM LAYER DOES NOT LOOK LIKE IT WILL BE
WARM ENOUGH FOR FZRA...THROUGH FZDZ COULD DEVELOP AS THE MOISTURE
LAYER SHALLOWS OUT TOWARD THE END OF THE EVENT. HAVE DECIDED NOT
TO MENTION ANY RAIN...EVEN WITH TEMPS IN THE 35-37 RANGE IN
NE/EC WI...AS LOW-LEVEL WET BULB TEMPS ARE EXPECTED TO REMAIN BLO
FREEZING.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 347 AM CST THU JAN 22 2015

500MB RIDGE ACROSS THE WESTERN UNITED STATES AND EAST COAST TROUGH
WILL DOMINATE THE WEATHER PATTERN DURING THE PERIOD. RIDGE AXIS
FAR ENOUGH EAST ACROSS THE WESTERN UNITED STATES...AND SPLIT FLOW
OVER THE EASTERN UNITED STATES WILL KEEP THE TRUE ARCTIC AIR
BOTTLED UP EARLY IN THE PERIOD. THERE IS SOME INDICATIONS THAT
RIDGE WILL RETROGRADE WHILE EAST COAST TROUGH DEEPENS WHICH SHOULD
OPEN THE DOOR FOR THE TRUE ARCTIC AIR TO PLUNGE SOUTHWARD INTO THE
AREA LATE NEXT WEEK INTO THE FOLLOWING WEEKEND.

FOR FRIDAY NIGHT...UPPER LEVEL DISTURBANCE AND COLD FRONT WILL MOVE
ACROSS THE REGION FRIDAY EVENING. PRECIPITATION TYPE ISSUES STILL
PROBLEMATIC ACROSS THE AREA DUE TO LOW LEVEL THERMAL PROFILES AND
MOISTURE CONCERNS AT MID LEVELS. WENT WITH THE PREVAILING TWO PRECIP
TYPES FRIDAY EVENING. WENT WITH A CHANCE OF LIGHT SNOW OR LIGHT FREEZING
DRIZZLE FRIDAY EVENING. MODELS HAVE TRENDED TO COLD AHEAD OF THESE FRONTS
OF LATE...SO COULD NOT RULE OUT SOME LIQUID PRECIPITATION FOR THE FIRST
FEW HOURS FRIDAY EVENING. DID COORDINATE PRECIPITATION TYPES WITH
THE SHORT TERM FORECASTER. AFTER MIDNIGHT...DRY CONDITIONS SHOULD
PREVAIL ACROSS MUCH OF THE REGION EXCEPT OVER THE FAR NORTH WHERE
LAKE EFFECT SNOW SHOWERS WILL LINGER IN SATURDAY. ABOVE NORMAL
TEMPERATURES WILL CONTINUE SATURDAY INTO SUNDAY BEFORE TEMPERATURES
RETURN CLOSER TO NORMAL EARLY NEXT WEEK.

NEXT AND MAYBE POTENT CLIPPER SYSTEM WILL AFFECT THE REGION SATURDAY
NIGHT INTO SUNDAY. AXIS OF HEAVIEST SNOWFALL PROBLEMATIC AS ALL
THE MODELS EXCEPT ECMWF ARE MUCH FURTHER NORTH. FOR EXAMPLE...GFS
WOULD GIVE NORTHERN WISCONSIN 2 TO 4 INCHES OF SNOW...WHILE ECMWF
WOULD SUGGEST LITTLE OR NO SNOW. PERUSAL OF WPC SNOW GRAPHICS AND
TRENDS OF THE LAST SEVERAL CLIPPER SYSTEMS...TRENDED TOWARDS A
COMPROMISE BETWEEN THE ECMWF AND THE CANADIAN/GFS/WRF SOLUTIONS.
LATER SHIFTS WILL BE BETTER ABLE TO PINPOINT SNOWFALL AMOUNTS.

TEMPERATURES SHOULD RETURN CLOSER TO NORMAL SUNDAY NIGHT INTO
EARLY NEXT WEEK. CLIPPER SYSTEM THAT MAY PASS TO THE NORTH OF THE
AREA DURING THE MIDDLE OF NEXT WEEK COULD BRING ABOVE NORMAL
TEMPERATURES TO THE AREA WEDNESDAY. 00Z ECMWF TONIGHT WOULD
SUGGEST A SURGE OF ARCTIC AIR NEXT FRIDAY (JAN 30) INTO THE
FOLLOWING WEEKEND.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1203 PM CST THU JAN 22 2015

PLENTY OF UNCERTAINTY DURING THE TAF VALID PERIOD. BASED ON
UPSTREAM INVERSIONS AND LOW LEVEL MOISTURE IT WAS QUESTIONABLE
WHETHER THERE WOULD BE MUCH/ANY CLEARING TODAY...BUT MOST OF
NORTHEAST WISCONSIN WAS VFR WITH NO CIGS BY 17Z. SOME OF THE
MODELS KEPT THE CLOUDS WHILE OTHERS HAD SKIES BECOMING CLR OR SCT.
CLOUDS SHOULD RETURN AS A CLIPPER SYSTEM APPROACHES. PRECIPITATION
SHOULD HOLD OFF UNTIL AROUND 12Z IN NORTH CENTRAL WISCONSIN BUT
TYPE IS A BIT OF A PROBLEM. BUFKIT SOUNDINGS AT RHI FROM THE 09Z
SREF/12Z NAM/12Z GFS ALL SHOWED A DRY LAYER AT LEAST 2000FT DEEP
THAT WILL PROBABLY RESULT IN MELTING OF ANY ICE CRYSTALS THAT FORM
ABOVE IT. MODELS SHOWED SOME DIFFERENCES REGARDING LOW LEVEL
MOISTURE AND AMOUNT OF LIFT...BUT WITH A SUBFREEZING MOIST LAYER
OFF THE SURFACE THERE COULD BE SOME FREEZING DRIZZLE WITH WEAK
LIFT. SINCE THERE IS NOT GREAT AGREEMENT ON THIS...HAVE ALSO
MENTIONED SNOW THERE. DEEPER MOISTURE AND STRONGER LIFT SHOULD
KEEP PRECIPITATION MAINLY AS SNOW IN EAST CENTRAL WISCONSIN. CIGS
AND VSBY SHOULD BE MVFR WITH ISOLATED IFR IN PRECIPITATION AND
CLOUDS.

WIND SHEAR IS LIKELY TO BECOME AN ISSUE TONIGHT AND PERSIST INTO
AT LEAST THE MORNING HOURS ON FRIDAY. WINDS AROUND 1500-2000FT AGL
ARE EXPECTED TO BE IN THE 35 TO 45 KNOT RANGE AND THERE IS SOME
DIRECTIONAL SHEAR AS WELL.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....KIECKBUSCH
LONG TERM......ECKBERG
AVIATION.......MG





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