A cool morning in NW Harris County with temperatures is the mid to upper 40's will warm up to the comfortable 70's today under sunny skies. Tomorrow will continue to warm as we begin to feel the response to the much advertised pattern change to a much colder pattern by Tuesday evening across the Lone Star State and much of North America. We are expecting a Omega Blocking Pattern that has several feature involved. Extratropical Storm Nuri played an important role in beginning the process of buckling the jet stream across N America, but other factors are in play such as tropical forcing, a robust Madden-Julian Oscillation (MJO) as well as rather strong Convectively Coupled Kelvin Wave (cckw) across the Pacific. At the High Latitudes across the North Pole and Arctic, very strong High Pressure extends across that area known as an Omega Block. Ridging in Alaska allows very cold air that has been building across Eurasia/Siberia to be pulled across the N Pole and plunge very far S into the United States and even Mexico. The blocking pattern extends into the NE Atlantic Ocean that does not allow the cold air to move E that far off the E Coast into the Atlantic as wee typically see in Winter. The main issue is this blocking regime does not appear to be transient and will be in place into the extended range that may well last into the week of Thanksgiving. If this blocking pattern persists, reinforcing shots of very cold air will continue to drop S in fairly rapid progression with the arrival of additional fronts about every 4-5 days. The main concerns are the embedded upper air disturbances under cutting the Western Ridge as well as those dropping S from Western Canada. Add to the mix a noisy sub tropical jet with over running moisture and upglide precipitation and you have a recipe for a very complicated forecast that is typical of a weak El Nino year. There will be periods of moderation, but the appear to be very short lived and the disturbances cross the Inter Mountain West and Plains will begin to lay down snow leading to less and less airmass modification as time goes on.
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1234 AM EST SUN NOV 09 2014
VALID 12Z WED NOV 12 2014 - 12Z SUN NOV 16 2014
...RELOADING UPPER PATTERN TO CONTINUE TROUGHING/COLD OVER MOST OF
THE CONUS...
...OVERVIEW...
WELL-ADVERTISED COLD SNAP WILL LEAD THE MEDIUM RANGE PERIOD
MIDWEEK NEXT WEEK AS STRONG RIDGING /500MB HEIGHT STND ANOMALY
NEARING +4 WHICH IS VERY RARE/ HOLDS OVER NORTHWESTERN NORTH
AMERICA. THIS FAVORS TROUGHING TO ITS SOUTHWEST AND SOUTHEAST IN
AN OMEGA BLOCK PATTERN... LOCKING IN THE COLD FOR MOST OF THE
CONUS OUTSIDE THE WEST COAST BUT PARTICULARLY FOCUSED OVER THE
CENTRAL STATES.
...GUIDANCE PREFERENCES...
SYNOPTIC AGREEMENT REMAINS GOOD AMONG THE 18Z PARALLEL GFS AND 12Z
ECMWF/ECENS MEAN... AND THEIR BLEND WAS USED AS THE BASE TO THE
FORECAST. THE DETAILS TO BE IRONED OUT LIE WITH THE EXODUS SPEED
OF THE UPPER TROUGH THROUGH THE NORTHEAST ON FRIDAY /WHERE THE
ECMWF MAY BE OVERLY WRAPPED UP/ AND ALSO THE STRENGTH OF THE RIDGE
ALONG THE WEST COAST UP INTO ALASKA. ECMWF ENSEMBLE MEMBERS
SUGGEST A STRONGER AND MORE RESILIENT RIDGE THAN THE GEFS MEMBERS
AND GIVEN THE LEAD-IN WAS INCLINED TO SIDE WITH MORE RIDGING
UPSTREAM WHICH SUPPORTS MORE DIGGING DOWNSTREAM INTO THE ROCKIES
BY THE END OF NEXT WEEKEND. 12Z GFS WAS NOT TOO FAR FROM THIS
CLUSTER OF SOLUTIONS AS WELL. THIS WOULD SUPPORT CYCLOGENESIS IN
THE UPPER MS VALLEY BY SUNDAY.
...SENSIBLE WEATHER HIGHLIGHTS...
PRECIP WILL FOCUS ALONG/AHEAD OF THE ARCTIC BOUNDARY PUSHING OFF
THE EAST COAST ON WEDNESDAY AND ALSO BACK THROUGH THE ROCKIES
WHERE THE COLD AIR WILL SPUTTER OVER THE DIVIDE. LAKE-EFFECT SNOW
SHOULD FLY IN EARNEST WITH NW FLOW OVER THE REGION AND A SFC-850
DELTA T OF ABOUT 15-20C. ENERGY THAT WILL SLIP BETWEEN THE RIDGE
CENTERS WILL SERVE AS THE MAIN PRECIP AREA WED-THU AS IT PUSHES
INTO OREGON AND NORTHERN CALIFORNIA. THE COLD TEMPERATURES REMAIN
THE TOP STORY WITH 30-40F BELOW AVERAGE TEMPERATURES POSSIBLE FROM
MT SOUTHEASTWARD AND EVEN 20-30F BELOW AVERAGE INTO TEXAS. SOME
RECORD LOW MINS/MAXES ARE POSSIBLE. SECONDARY SURGE NEXT WEEKEND
SHOULD BE INTERRUPTED BY BRIEF MODERATION BUT STILL COLDER THAN
AVERAGE FOR MID-NOVEMBER.
FRACASSO
The forecast late in the week is already presenting some challenges as a fairly strong upper air disturbance arrives from the Western US into the Southern Rockies/Southern Plains. There are some indications that a wave of low pressure may develop along the Lower Texas Gulf Coast and spread moisture over a shallow Arctic airmass at the surface. The best chance for wintry mischief will be across the Panhandle and Oklahoma and on E into Arkansas. As always we cannot not accurately predict what the sensible weather will be beyond the day 2 to 4 day range and as we know, that can even be challenging.

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Member: National Weather Association
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