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Pittsburgh/Western Pa Weather


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I'm sure this is mostly due to the pending storm, but this discussion is tremendous. This guy (or girl) "Fries" might be "our guy" from now on....

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE PITTSBURGH PA

722 PM EDT SUN APR 22 2012

.SYNOPSIS...

A RAPIDLY INTENSIFYING LOW PRESSURE SYSTEM WILL MOVE UP THE EAST

COAST THIS EVENING AND MOVE OVER EASTERN PENNSYLVANIA BY MORNING.

THIS SYSTEM WILL SPREAD RAIN ACROSS MUCH OF THE AREA THIS EVENING

AND TONIGHT...BEFORE GRADUALLY TRANSITIONING TO SNOW LATE TONIGHT

AND MONDAY. MANY AREAS WILL SEE HEAVY SNOWFALL DURING THE MORNING

HOURS ON MONDAY...WITH SIGNIFICANT ACCUMULATIONS POSSIBLE IN SOME

AREAS. CONDITIONS SHOULD GRADUALLY IMPROVE INTO MID-WEEK.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...

WITH 6PM UPDATE...PRIMARY CHANGE WAS TO DELAY PRECIPITATION IN

MOST LOCATIONS BY A FEW HOURS. WHILE SOME LIGHT SHOWERS HAVE

DEVELOPED AROUND THE PITTSBURGH METRO AREA...MAIN SHIELD OF

PRECIPITATION REMAINS EAST OF THE FORECAST AREA. HAVE SLOWED DOWN

ARRIVAL OF WIDESPREAD PRECIPITATION BY 2-3 HOURS IN SOME

LOCATIONS...BUT HAVE BLENDED BACK TO PREVIOUS PRECIP TIMING BY

2-3AM. THIS WILL NOT REQUIRE ANY CHANGE TO ADVISORIES AND

WARNINGS. PREVIOUS DISCUSSION FOLLOWS.

A COMPLICATED LARGE SCALE WEATHER PATTERN IS CONTINUING TO UNFOLD

OVER THE EASTERN THIRD OF THE CONUS AS AN UPPER LOW IS SLOWLY

SAGGING SOUTHEASTWARD THROUGH THE LOWER GREAT LAKES REGION WHILE

ANOTHER UPPER LOW HAS ALREADY STARTED ITS HARD LEFT TURN TO RACE

UP THE COAST OVERNIGHT. A RATHER COMPLICATED INTERACTION BETWEEN

THESE TWO FEATURES BOTH AN INCREASINGLY CURVED AS WELL AS

INCREASINGLY COUPLED JET STREAK STRUCTURE OVER THE REGION THROUGH

MORNING. THE TRACK OF THIS UPPER LEVEL DIVERGENCE MAXIMA WILL

LIKELY DETERMINE THE TRACK OF A SURFACE SYSTEM THAT IS CURRENTLY

ALONG THE NORTH CAROLINA COAST AS IT SURGES NORTHWARD OVERNIGHT.

THE MODEL CONSENSUS GENERALLY BRINGS THE SURFACE LOW FROM ITS

CURRENT LOCATION TO SOMEWHERE BETWEEN PHILADELPHIA AND NEW YORK BY

MORNING. A VERY STRONG SURFACE PRESSURE GRADIENT IS PRESENT AROUND

THE SURFACE LOW AS IT HEADS NORTHWARD. THE GRADIENT COUPLED WITH

A RELATIVELY CONTINUOUSLY MIXED SURFACE LAYER WILL ALLOW NORTHERLY

WINDS TO CONTINUOUSLY INCREASE OVERNIGHT INTO MORNING. IN

ADDITION...JUST OFF THE SURFACE...GFS AND NAM SOUNDINGS INDICATE

UPWARDS OF 50-60 KTS OF FLOW PRESENT PER BUFKIT. WITH AT LEAST THE

SURFACE LAYER BEING MIXED...GUSTY WINDS OF UP TO 40-45 MPH SEEM

REASONABLE AS A RESULT. THIS LOW LEVEL FLOW WILL BRING IN

CONTINUOUSLY COLDER AIR OVERNIGHT LIKELY FROM A SOURCE REGION

INCLUDING LOWER MICHIGAN AND SOUTHWESTERN ONTARIO. WHAT`S

IMPORTANT ABOUT THIS IS THAT SURFACE DEW POINTS IN THE

AFOREMENTIONED AREAS ARE CURRENTLY RUNNING IN THE 25-30F

RANGE...WHICH SHOULD HELP THE CASE FOR WET BULB COOLING AS THIS

AIR WORKS ITS WAY SOUTHWARD INTO OUR REGION. AS A RESULT...WHEN

LIFT FIRST SPREADS FROM THE SOUTHEASTERN ZONES TOWARD THE

NORTHWEST...PRECIPITATION SEEMS LIKELY TO BEING AS RAIN ALMOST

EVERYWHERE...HOWEVER AS THE COMBINATION OF A COLDER SOURCE AIR AS

WELL AS INCREASED COLUMN ADIABATIC COOLING DUE TO INTENSELY

NEGATIVE OMEGAS IN ASSOCIATION WITH THE SYSTEM COMING INTO THE

REGION...MOST AREAS ARE LIKELY TO CHANGE TO SNOW BY AROUND

DAYBREAK.

TEMPERATURES OVERNIGHT ARE RATHER TOUGH TO DETERMINE. GUIDANCE

SEEMS FAIRLY WARM GIVEN THAT WE FAILED TO REACH THE HIGHS ANY

MODELS OR MOS SUGGESTED TODAY...NOT TO MENTION THE IMPRESSIVE LIFT

THAT TRANSITS THE REGION. AS A RESULT...TEMPERATURES WERE

GENERALLY CUT A COUPLE OF DEGREES BELOW GUIDANCE...WHICH PUTS A

PRECARIOUSLY LARGE PORTION OF THE REGION WITHIN A DEGREE OR TWO OF

FREEZING BY MORNING. FRIES

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...

WHILE ALL THE FUN STARTS TONIGHT...THE MOST FUN PART OF THE

FORECAST REALLY OCCURS DURING THE DAY MONDAY. AS THE SURFACE

SYSTEM CONTINUES NORTHWARD ON MONDAY...THE NAM AND GFS BOTH

PORTRAY A VERY WELL DEVELOPED TROWAL WRAPPING AROUND THE NORTHERN

AND NORTHWESTERN PERIPHERY OF THE SYSTEM...WITH ITS APEX PLANTED

SQUARELY IN WESTERN PENNSYLVANIA. IMPRESSIVE THETA-E ADVECTION IS

PRESENT IN A DEEP LAYER FROM ABOUT 850 UP TO 500 MB INTO WESTERN

PENNSYLVANIA SUCH THAT A STRONG AND PROLONGED MAXIMA OF

FRONTOGENETICAL FORCING SETS UP IN AN AXIS BASICALLY STRINGING THE

RIDGES OF THE EASTERN PART OF THE CWA...PARTICULARLY IN THE

850-600 MB LAYER. ADDITIONALLY...ON THE UPWARD BRANCH OF THE

DEVELOPING FRONTOGENETICAL CIRCULATION...THE GFS AND NAM BOTH

DEPICT SOME AMOUNT OF EPV REDUCTION. THIS...ALONG WITH THE

AFOREMENTIONED JET COUPLING...AND THE NOSE OF A NORTHEASTERLY LOW

LEVEL JET PLACING A SOLID AMOUNT OF LOW-LEVEL CONVERGENCE OVER

WESTERN PENNSYLVANIA...WILL ALLOW ABUNDANT SYNOPTIC AS WELL AS

MESOSCALE COMPONENTS TO SUPPORT PROLONGED AND ANOMALOUSLY STRONG

LIFT TO SIT OVER WESTERN PENNSYLVANIA THROUGH MOST OF THE DAY ON

MONDAY. THE MAGNITUDE OF THE LIFT COUPLED WITH CONTINUOUS COLD

ADVECTION SEEMS LIKELY TO ALLOW FOR A VERY TIGHT DIURNAL

TEMPERATURE CURVE DURING THE DAY ON MONDAY. AS SUCH...HIGHS SEEM

UNLIKELY TO WANDER MUCH FROM WHAT THE READINGS WILL BE AT

SUNRISE...WHICH AT THIS TIME SEEM LIKELY TO BE PRIMARILY IN THE

LOWER TO MIDDLE 30S.

GIVEN BUFKIT PROFILES FROM THE NAM AND GFS AS WELL AS LAYER

TEMPERATURES OF THE CANADIAN REGION AND ECMWF THAT STRING FREEZING

BELOW 900 MB...AND GENERALLY COOL INTO THE -5 TO -6C RANGE AT 850

MB...THE PRECIPITATION TYPE IN THE BEST LIFT SEEMS LIKELY TO BE

SNOW THROUGHOUT THE DAY ON MONDAY. ONLY DURING THE LIGHTER PERIODS

OF PRECIPITATION DOES IT SEEM POSSIBLE THAT WE WILL SEE A

MIX/CHANGE TO RAIN. HOWEVER...GIVEN THE PROFILES STRADDLING

FREEZING...THE WARM GROUND...AND HIGH SUN ANGLE...HIGH SNOW RATIOS

WILL BE EXCEEDINGLY DIFFICULT TO COME BY. THE ONLY CAVEAT TO THIS

RELATIVE TO THE FORECAST ISSUED YESTERDAY IS THAT MODEL TIME

HEIGHT SECTIONS FROM BOTH THE NAM AND GFS INDICATE THE BEST

NEGATIVE OMEGA CENTER IS LOCATED IN THE -12 TO -15C RANGE ON

MONDAY MORNING. THIS IS SEVERAL DEGREES COLDER THAN ON PREVIOUS

RUNS...AND DOES LEND ITS HAND TO HIGHER RATIOS DUE TO A BETTER ICE

CRYSTAL GROWTH HABIT IN THE DENDRITIC GROWTH ZONE. ALL FACTORS

CONSIDERED...BUFKIT FROM THE NAM AND GFS FAVORED RATIOS BETWEEN 10

AND 15:1...HOWEVER WITH THE HIGH SUN ANGLE...WARM GROUND...AND

MARGINAL SURFACE LAYER TEMPERATURES...RATIOS WERE RESTRICTED TO

BELOW 9:1 EVERYWHERE...AND IN THE LOWER ELEVATIONS (INCLUDING

PITTSBURGH) THESE RATIOS WERE FURTHER RESTRICTED TO BELOW 5:1

OWING TO A MIX OF PRECIPITATION TYPES ON THE TEMPORAL PERIPHERIES

OF THE SYSTEM`S PROGRESSION THROUGH THE AREA. ALL IN ALL...WATCHES

WERE UPGRADED TO EITHER WARNINGS OR ADVISORIES WITH ONLY SMALL

CHANGES TO PREVIOUS ACCUMULATION EXPECTATIONS. IN ADDITION...ONE

MORE ROW OF COUNTIES WERE ADDED AS WINTER WEATHER ADVISORIES ON

THE WESTERN FLANGE OF THE PRODUCTS...THAT NOW INCLUDES MORGANTOWN.

ANY OF THE AREAS UNDER THE ADVISORIES OR WARNINGS SEEM LIKELY TO

EXPERIENCE A SIGNIFICANT SNOWFALL FOR THIS LATE IN THE SEASON.

COUPLING THE HEAVY WET SNOW AND WIND WILL LIKELY CAUSE PROBLEMS

WITH BROKEN LIMBS ON THE NEWLY LEAFED TREES AROUND THE AREA. AS

SUCH...THE LOGIC FOR PRODUCT ISSUANCE WAS MORE FOR THIS PROBLEM

AND THE ACCOMPANYING POWER OUTAGES THAN FOR LARGE AMOUNTS OF SNOW

TO IMPACT THE ROADWAYS.

AFTER THE BIG STORM...SNOW WILL BE SLOW TO EXIT THE NORTHERN ZONES

AS WEAK DEFORMATION COUPLED WITH SOME LAKE EFFECT INFLUENCE LINGER

INTO TUESDAY. HOWEVER...BOUNDARY LAYER TEMPERATURES WARM BY THAT

TIME...SO PRECIPITATION TYPE SHOULD MIX WITH OR CHANGE TO SNOW AND

END ACCUMULATIONS EVERYWHERE. DRY WEATHER SHOULD ENSUE FOR A SHORT

PERIOD THEREAFTER. FRIES

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r u guys leafed out at all? if so i had 8 -10 inches(depending on elevation) in october and it was devastating. trees and tree limbs down all over and with some people out of power for over a week.

Pretty much, yeah. At least in my particular area I am. Most trees are "fully leafed" here in southern Allegheny County.

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I'm down to 39 degrees with a 2 degree drop in the last hour.....although I know this may be a slightly weenie-ish post as dynamics will probably be more imporant for a rapid changeover than starting temp.

Just reporting....

EDIT: 38 now at 9:16.

37 now at 9:37

OK back up to 38 at 9:45, along with forcing myself to take a timeout until 10:30

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I'm down to 39 degrees with a 2 degree drop in the last hour.....although I know this may be a slightly weenie-ish post as dynamics will probably be more imporant for a rapid changeover than starting temp.

Just reporting....

EDIT: 38 now at 9:16.

I just dropped to 39.9. I was at 43 about 2 hours ago.

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Not per the NAM and it's dreams of 15"+ a couple days ago and consistant 8"+ today

Something is up with this run....I mean even northwest PA gets shafted

Those guys will get synoptic and LE snow which is why the terrain above 1500' is getting hit hard by the NWS. Obviously how and when the band develops has been the biggest question.

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Not per the NAM and it's dreams of 15"+ a couple days ago and consistant 8"+ today

Something is up with this run....I mean even northwest PA gets shafted

It is really weird how the precip almost disappears up to the NY/Pa border.

I have been looking at the HRRR and it still has that band move in and set up North to South through our area. Could the model have an error across Pa? Just asking.

http://rapidrefresh.noaa.gov/hrrrconus/Welcome.cgi?dsKey=hrrr&domain=t7&run_time=22+Apr+2012+-+23Z

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It is really weird how the precip almost disappears up to the NY/Pa border.

I have been looking at the HRRR and it still has that band move in and set up North to South through our area. Could the model have an error across Pa? Just asking.

http://rapidrefresh....rrr&ptitle=HRRR Model Fields - Experimental&maxFcstLen=15&fcstStrLen=-1&resizePlot=1&domain=t7&wjet=1

The HRRR looks like it gives about .25 of QPF through the next 15 hrs...unfortunately, that won't be more than an inch and might not even stick.

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It's also why we have ranges in situations like this. It's a very anomalous pattern so nobody should focus on the highest amounts.

Well yes certainly.....which is why we were at no point expecting the NAM's 16" and 18" totals from the past 36 hours. My point was that there has been a high level of consistency showing this as a significant event. If this is correct, it's a pretty dramatic change in modeling by the NAM.

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Well yes certainly.....which is why we were at no point expecting the NAM's 16" and 18" totals from the past 36 hours. My point was that there has been a high level of consistency showing this as a significant event. If this is correct, it's a pretty dramatic change in modeling by the NAM.

It still will be, but for your area..might be more into JST.

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Well yes certainly.....which is why we were at no point expecting the NAM's 16" and 18" totals from the past 36 hours. My point was that there has been a high level of consistency showing this as a significant event. If this is correct, it's a pretty dramatic change in modeling by the NAM.

It's not every day you see a model go from 10 inches of snow to 1 inch in 12 hours less than 24 hours from the event.

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It still will be, but for your area..might be more into JST.

I understand that...but even the GFS and Euro as of last night were showing around an inch or so of QPF in the Pittsburgh area. IN the last 24 that modeling has gone down to near nothing at this point.

The NAM is just an absolutely huge swing. I was watching the models through out the day, and I went from thinking that this was a probable 6 inch storm at least for the Pittsburgh when I woke up to now thinking we might be getting an inch.

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I understand that...but even the GFS and Euro as of last night were showing around an inch or so of QPF in the Pittsburgh area. IN the last 24 that modeling has gone down to near nothing at this point.

The NAM is just an absolutely huge swing. I was watching the models through out the day, and I went from thinking that this was a probable 6 inch storm at least for the Pittsburgh when I woke up to now thinking we might be getting an inch.

The thing is, QPF means nothing in a marginal event. You have to look at where the banding sets up, because that will dictate cities like PIT on whether or not they will get snow. The best banding was still questionable as PIT was right on the edge. One move, and that's it. The models earlier today imo did not look great for PIT. I thought they would be on the edge and they will be.

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It's not every day you see a model go from 10 inches of snow to 1 inch in 12 hours less than 24 hours from the event.

Man, I completely put this winter to bed over a month and a half ago, and was ready for spring. I let this rope me back in, and like the rest of the winter, a bust.

Oh well, maybe there will be a baseball game I can go to tomorrow now.

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Man, I completely put this winter to bed over a month and a half ago, and was ready for spring. I let this rope me back in, and like the rest of the winter, a bust.

Oh well, maybe there will be a baseball game I can go to tomorrow now.

Yeah, I was thinking the same thing. We all let this past winter go weeks ago and then this little surprise came up and pulled us back in. This one may just end up like the rest. Another near miss for the area. It's given us something unusual for this time of year to track and talk about anyway.

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Yeah, I was thinking the same thing. We all let this past winter go weeks ago and then this little surprise came up and pulled us back in. This one may just end up like the rest. Another near miss for the area. It's given us something unusual for this time of year to track and talk about anyway.

Typical storm tracking for Southwestern pa. All the posts start out as "Western Pa. gets clobbered...gets crushed...Look out"

Then we usually end up on the edge with a minor accumulation. Just like every year we get modeled for about 150 inches of snow every year only to end up with our average of 40 which comes 1 or 2 inches at a time.

I too got sucked in and yes it was something to track but now I would rather have sunny and 55 than 1/2 inch of slush which will cancel my kids ball games early this week.

Oh well.

No I can say it with confidence.

"I am ready for warm, humid air with Thunderstorms."

(Of course I will still be on here tomorrow with my observations of the wet snow we do get...haha)

The life of a weather nut.

And we will all be back in November for more frustration. It's what we do.

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Typical storm tracking for Southwestern pa. All the posts start out as "Western Pa. gets clobbered...gets crushed...Look out"

Then we usually end up on the edge with a minor accumulation. Just like every year we get modeled for about 150 inches of snow every year only to end up with our average of 40 which comes 1 or 2 inches at a time.

I too got sucked in and yes it was something to track but now I would rather have sunny and 55 than 1/2 inch of slush which will cancel my kids ball games early this week.

Oh well.

No I can say it with confidence.

"I am ready for warm, humid air with Thunderstorms."

(Of course I will still be on here tomorrow with my observations of the wet snow we do get...haha)

The life of a weather nut.

And we will all be back in November for more frustration. It's what we do.

At least it isn't January, this would've hurt. LoL.

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Not everyone is quite so down....

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE PITTSBURGH PA

1118 PM EDT SUN APR 22 2012

.SYNOPSIS...

DEEP LOW PRESSURE WILL SPREAD RAIN AND SNOW ACROSS THE UPPER OHIO

VALLEY REGION THROUGH MONDAY. SIGNIFICANT ACCUMULATION IS POSSIBLE

IN SOME AREAS...ESPECIALLY OVER THE HIGHER ELEVATIONS.

&&

.NEAR TERM /THROUGH MONDAY/...

MID/UPR LEVEL LOW PRESSURE CONTINUES TO DEVELOP TOWARD THE UPPER

OHIO REGION TONIGHT AS SURFACE LOW MOVES UP THE EAST COAST. NO

CHANGE TO FORECAST OF RAIN TO SNOW TRANSITION WITH AREAS OF HEAVY

SNOW OVER AREAS NORTH AND EAST OF PITTSBURGH FOR THE NEAR TERM.

MUCH WILL DEPEND ON BOUNDARY LAYER TEMPERATURES...DEVELOPMENT OF

MID LEVEL FRONTOGENESIS AREAS...WHICH WOULD SUPPORT HIGHER

SNOWFALL RATES...AS WELL AS ENCROACMENT OF MID LEVEL DRY SLOT.

IN ADDITION...DEEPENING SURFACE LOW...OFFSET BY MIDWRN HIGH

PRESSURE WILL INTENSIFY THE PRESSURE GRADIENT OVR THE REGION

TODAY. WIND GUSTS OVER WESTERN COUNTIES MAY APPROACH ADVISORY

CRITERIA AS MIXING LEVEL DEEPENS THIS AFTERNOON.

BOTTOM LINE IS THAT MODELS CONTINUE TO SUPPORT HEAVY SNOWFALL

EVENT AND NO CHANGES WILL BE MADE TO HEADLINES TONIGHT.

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