FXUS61 KCTP 220131
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
831 PM EST MON DEC 21 2009
.SYNOPSIS...
A PERSISTENT UPPER LOW NORTH OF PENNSYLVANIA WILL KEEP THE REGION
UNSEASONABLY COLD THROUGH THE MIDDLE OF THE NEW WEEK WHILE THE
TYPICAL DOWNWIND CLOUDS AND SNOW SHOWERS OFF OF LAKE ERIE WILL
AFFECT WESTERN AND NORTHWESTERN AREAS INTO TUESDAY. A STRONG LOW
PRESSURE SYSTEM OVER THE MIDWEST WILL LIKELY PRODUCE SOME WINTRY
PRECIPITATION FOR CHRISTMAS.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
VERY LIGHT OROGRAPHIC SNOW SHOWERS/FLURRIES CONTINUE ACROSS MY FAR
NORTH TONIGHT AS THE WEAK CLIPPER SNEAKS BY TO OUR NORTH. THIS
SHOULD CONTINUE FOR MOST OF THE NIGHT...WITH ACCUMULATIONS LIMITED
MAINLY TO THE FAR NORTHWEST ZONES WHERE A COATING TO AN INCH OR 2
MAY ACCUMULATE IN SOME AREAS. ESSENTIALLY NO CHANGES TO THE GOING
FORECAST FOR THE OVERNIGHT.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
NORTHWEST FLOW WILL PERSIST TUE...BUT LOWERING INVERSION HEIGHTS
AND DRY AIRMASS WILL SHUT OFF THE SNOW SHOWERS ACROSS THE NORTH
AND WEST AS HIGH PRESSURE BEGINS TO BUILD IN. TUE NIGHT AND WED
NIGHT WILL SEE TEMPS IN THE TEENS...AND PROB SOME SINGLE DIGIT
READINGS ACROSS THE AREA WITH SNOWPACK ON GROUND. TEMPS WILL WARM
BACK UP CLOSE TO FREEZING IN WED. WEATHER FOR LATER IN THE WEEK
CONTINUES TO LOOK INTERESTING AND POTENTIALLY WINTRY.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
SIGNIFICANT SNOW AND/OR ICE POSSIBLE FOR THE HOLIDAYS...
CONFIDENCE REMAINS HIGH WITH REGARDS TO A PERIOD OF WINTRY
PRECIPITATION AFFECTING CENTRAL PENN FROM AS EARLY AS LATE
CHRISTMAS EVE...AND LASTING POSSIBLY THROUGH THE FIRST HALF OF
CHRISTMAS DAY. THIS WILL UNDOUBTEDLY HAVE NEGATIVE IMPACTS ON
HOLIDAY TRAVEL. TIMING OF THE ONSET AND HEAVIEST PRECIPITATION IS
COMING INTO BETTER FOCUS BASED ON THE LATEST COMPUTER
GUIDANCE...BUT AS IS TYPICALLY THE CASE...THE DETAILS OF FCST
SUCH AS PRECIPITATION TYPE/LOCATION REMAIN INHERENTLY ELUSIVE AT
THIS RANGE.
WITH THE EXCEPTION OF THE NAM...MODEL AND ENSEMBLE SOLNS ARE
EXHIBITING A SLOWER...WWD TREND IN SFC LOW POSITION AS IT EJECTS
NNEWD FM THE SRN PLAINS THUR NGT INTO FRI. THIS IS PERHAPS MOST
EVIDENT IN THE 12Z CMC/UKMET...WHICH BOTH DEPICT A LOW CENTER AT
LEAST 300MI TO THE WEST OF THE YESTERDAYS 12Z CYCLE. THE 00/12Z
RUNS OF THE GEFS OUTPACE AN OPERATIONAL GFS/ECMWF MEAN SFC LOW
POSITION BY SEVERAL HUNDRED MILES TO THE NE OVR THE UPPER GRT LKS
BY 26/12Z. THIS GFS/ECMWF MEAN SOLN TAKES A 995-1000MB LOW FM SE
IA JUST NORTH OF CHICAGO ON SAT BEFORE FURTHER WEAKENING THE SYS
INTO SRN ONTARIO BY 27/00Z.
THE WRN TRACK SUGGESTS COLD AIR DAMMING E OF THE APPLCHNS WILL BE
MORE PREVALENT...AS STG HI PRES RETREATS INTO NRN NEW ENG/QUE. IN
ADDITION...A BLEND OF THERMAL PROFILES FROM THE GFS/GEFS/EC HINT
AT AN INTERESTING PTYPE TRANSITION...FROM FZRA TO BACK TO SNOW/IP
ACROSS PORTIONS OF THE AREA AS ENHANCED PRECIP RATES AND EVAP
COOLING/WETBULB DROPS 850MB TEMPS BLW 0C DURG THE AFTN ON
CHRISTMAS DAY. EXACT DETAILS AND CONFIDENCE IN PTYPE WILL GET
BETTER AS THIS STORM MOVES INTO THE REALM OF SHORTER
RANGE/MESOSCALE MODELS. UNTIL THEN...THE MESSAGE AND HIGH
PROBABILITY OUTCOME IS FOR A WINTRY MIX FOR THE HOLIDAYS.
MUCH COLDER AIR WILL FILTER INTO THE REGION LATER THIS WEEKEND
INTO EARLY NEXT WEEK AS A MEAN TROUGH TAKES HOLD OVER MUCH OF THE
ERN US. CYC FLOW WILL KEEP SCT LES SHWRS OVER THE WESTERN AND
NORTHERN MNTS. BLEND OF EC/GFS MEAN HEIGHTS SHOWS THE LW TROUGH
LIFTING OUT AS THE FLOW BECOMES MORE ZONAL INTO EARLY NEXT WEEK.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
PERSISTENT NW FLOW WILL CONTINUE AS A CLIPPER SHORTWAVE SLIDES BY
TO THE NORTH TONIGHT. THIS WILL KEEP LIGHT LAKE EFFECT AND OROGRAPHIC
SNOWS CONTINUING THROUGH THE NIGHT IN KBFD/KJST WITH CIGS BOUNCING
ARND BTWN 700FT AND 1500FT AND VSBYS VARIABLE BTWN 1SM AND 5SM.
EAST OF MTNS...OCCASIONAL MVFR CIGS BTWN 1500FT AND 2500FT
EXPECTED AT KAOO/KUNV ALONG WITH A FEW FLURRIES. ACROSS THE SUSQ
VALLEY...A HIGH CONFIDENCE OF VFR CONDS THE ENTIRE NIGHT AT
KIPT/KMDT.
HIGH PRES RIDGE WILL BUILD INTO THE REGION ON TUESDAY...CAUSING
LGT LAKE EFFECT SNOWS TO TAPER OFF. BY AFTN...CIGS EVEN AT KBFD
WILL LIKELY IMPROVE TO VFR. HOWEVER...LATEST MODEL DATA SUGGEST
MVFR CIGS MAY PERSIST ARND KJST.
OUTLOOK...
WED/THU...NO SIG WX EXPECTED.
FRI/SAT...FREEZING PRECIPITATION/IFR CONDS POSSIBLE.
SAT...IFR CONDS POSS EARLY.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...RXR
NEAR TERM...DEVOIR/RXR
SHORT TERM...RXR
LONG TERM...STEINBUGL
AVIATION...FITZGERALD
