FXUS63 KGRB 141325 AAC
AFDGRB
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GREEN BAY WI
725 AM CST MON DEC 14 2009
.UPDATE...COLDER AND DRIER AIR FLOWING IN FM THE NE WAS ALLOWING
FOR SOME EVAP COOLING AT LOW-LEVELS...AND WORSENING THE FREEZING
DRIZZLE SITN. SRN LAKESHORE AREAS ALSO HAVEN/T BENEFITTED FROM THE
WARMING EFFECTS OF THE LAKE...AS LAND-BREEZE KEEPING WLY COMPONENT
TO THE WIND. THAT EFFECT WL PROBABLY LESSEN IN THE NEXT FEW HRS.
RADAR INDICATED MID-LVL RETURNS INCREASING. 12Z RAOB ALSO LOOKS A
LITTLE MORE ENCOURAGING ABOUT SATURATING MID-LVLS THAN RUC HAD
BEEN SHOWING. WL CONTINUE TO HAVE PCPN EVENTUALLY CHANGING TO
SNOW. WL LIKELY TWEAK AMNTS DOWN IN SOME AREAS...ESP AREAS THAT
WERE IN THE INTIAL ADVISORY BUT HAVEN/T GOTTEN ANY ACCUMULATION
YET.
UPDATED PRODUCE SUITE WL BE OUT WITHIN A HALF HOUR OR SO.
SKOWRONSKI
&&
.PREV DISCUSSION...ISSUED AT 630 AM CST MON DEC 14 2009...
UPDATE...PCPN STILL VIRTUALLY ALL FZDZ ACRS THE SERN 3/4 OF THE
FCST AREA. NOT A LOT TO GRAB ONTO TO FIGURE OUT EXACTLY WHEN CHG
TO SNOW WL OCCUR. LATEST RUC ANALYSIS SHOWED VERY STG 700 MB MID-
LVL RH GRADIENT OVER THE FCST AREA...WITH DRY AIR ACRS THE FAR S.
SO WE ARE STILL A LONG WAY FM GETTING MID-LVLS MOIST ENOUGH TO
PRODUCE ICE CRYSTALS TO SEED INTO LOWER DECK. MODEL FCST
SOUNDINGS SUGGEST DEPTH OF LOW-LEVEL MOISTURE MAY EVENTUALLY
INCREASE TO WERE WE ARE COLD ENOUGH AT THE VERY TOP OF THE
CLDS...ARND 800 MB...TO PRODUCE ICE CRYSTALS. BUT TIMING THAT IS
VERY DIFFICULT. SNOWFALL TOTALS WE HAVE GOING IN THE FCST STARTING
TO LOOK HARD TO ACHIEVE GIVEN THAT THERE MAY NOT BE THAT MUCH PCPN
LEFT BY THE TIME WE CHANGE TO SNOW. HAVE ALREADY PUSHED BACK
CHANGEOVER ONCE AND TRIMMED SNOWFALLS. AM LEANING TOWARD DOING
THAT AGAIN. BUT WL WAIT ABOUT AN HOUR OR SO AND SEE IF WE START TO
GET SOME SITES CHANGING TO SNOW IN THE AREA SW OF GRB WHERE
RETURNS ARE NOW INCREASING ON RADAR.
PLAN ON PUSHING OUT FULL FCST UPDATE SUITE BETWEEN 730 AM AND 800
AM. HOW SIG THE CHANGES ARE WL DEPEND ON HOW THINGS EVOLVE BETWEEN
NOW AND THEN.
SKOWRONSKI
DISCUSSION ISSUED AT 357 AM CST MON DEC 14 2009...
SHORT TERM...TDA/TNGT/TUE. FZDZ BECOMG WIDESPREAD IN E-C WI.
EXTENDED ADVISORY SWD INTO THAT AREA. IF ROADWAYS ARE TREATED...
THEY/LL BE OKAY BECAUSE TEMPS ARE WARM ENOUGH. ALSO...ROADS STILL
COVERED IN SNOW FROM LAST WEEKS BLIZZARD PROBABLY WON/T SEE A CHANGE
IN CONDITIONS. BUT ROADS THAT WERE CLEARED TO PAVEMENT COULD TURN
ICY. SNOW FALLING ON TOP OF THAT COULD MAKE A REAL MESS. ALREADY GOT
REPORTS OF VERY SLICK ROADS BACK IN CENTRAL WI. IN GENERAL...
TWEAKED SNOWFALLS DOWN IN THE AREAS NOT GETTING SNOW YET.
NAM AND TO SOME EXTENT SREF SUGGEST NRN STREAM SHRTWV WL GENERATE
SECOND ROUND OF SHSN THIS AFTN AND INTO THIS EVENING. JUST WENT WITH
SCT SHSN FOR THAT FOR NOW. NEED TO WATCH AND MAY NEED TO ADD ANOTHER
INCH TO ACCUMULATIONS TO THE FAR N IF IT STARTS TO MATERIALIZE.
DAY SHIFT WL NEED TO DETERMINE IF THERE IS ENOUGH SEPARATION WITH
SYSTEM SNOWS TO LET ADVISORY FOR THE N EXPIRE...OR IF IT NEEDS TO
BE EXTENDED.
VERY COLD AIR OVER NRN PLAINS WL SURGE EWD STARTING TNGT. THE NAM
PERFORMED BEST WITH TEMPS THE LAST TIME. IT/S GENERALLY SLOWER TO
BRING COLD AIR EWD THAN THE OTHER MODELS. THAT/S BECAUSE IT KEEPS
WINDS MORE NLY IN NE WI...AS SFC TROF HANGS BACK FM DEPARTING SYSTEM
AND TOWARD APPROACHING NRN STREAM SHRTV. THAT MAKES SENS...BUT WOULD
LIKE TO SEE MORE SUPPORT FM OTHER MODELS. TWEAKED GRIDS TO HOLD
TEMPS UP IN THE FAR NE...BUT LET COLD AIR JUST SURGE ACRS THE REST
OF THE AREA. LIKELY WON/T GET MUCH RECOVERY TUE.
LONG TERM...TUESDAY NIGHT THROUGH NEXT SUNDAY. WEAK SHORTWAVES
MOVING THROUGH NORTHWEST UPPER FLOW MAY PRODUCE SOME LIGHT SNOW OR
FLURRIES WEDNESDAY NIGHT THROUGH THURSDAY AND AGAIN FRIDAY. THEN
THE MODELS DO AN UNUSUAL THING...RETROGRADING THE UPPER LOW THAT
IS OVER NEW BRUNSWICK AT 12Z FRIDAY TO LAKE SUPERIOR BY 12Z
SUNDAY. THIS IS LIKELY THE RESULT OF THE REX BLOCK (CLOSED UPPER
HIGH OVER SOUTHERN GREENLAND AND CLOSED UPPER LOW OVER QUEBEC).
THIS PATTERN IS NOT TOO COMMON TO BEGIN WITH...AND THE SPEED IN
WHICH THE LOW RETROGRADES IS VERY UNUSUAL. SO THE CONFIDENCE IN
THE FORECAST FOR SATURDAY AND SUNDAY IS LOW.
ONE THING THAT WE NOTICED THAT MIGHT BE SIGNIFICANT TO THE WEEKEND
FORECAST IS THE AMOUNT OF LOW LEVEL MOISTURE THAT WRAPS BACK INTO
THE WESTERN GREAT LAKES FROM THE NORTHEAST. THIS MIGHT INCREASE THE
CHANCE FOR LAKE EFFECT SNOW SATURDAY AND SUNDAY. YESTERDAY WE
THOUGHT THAT LOW LEVEL WINDS AND TEMPERATURES MIGHT BE SUITABLE
FOR LAKE EFFECT SNOW OVER THE WEKEND...BUT THAT THE AIR WOULD BE
TOO DRY. IF THIS MOISTURE DOES ARRIVE THEN IT IS POSSIBLE THAT
SIGNIFICANT LAKE EFFECT SNOWS COULD OCCUR IN NORTHERN WISCONSIN
SATURDAY AND POSSIBLY IN EASTERN WISCONSIN SUNDAY AND MONDAY IF
WINDS SHIFT TO NORTHEAST.
AVIATION...IFR CONDITIONS PRETTY WIDESPREAD. THINK ALL THE FZDZ
WL BE GONE BY 15Z. WOULD ANTICIPATE IFR CONDITIONS ACRS THE
N...AND MVFR ACRS THE S BY LATE AFTN.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR WIZ005-010>013-
018>022-030-031-035>040-045-048>050-073-074.
&&
$$
