Sorry for my tardiness. First, happy Saint Patrick's Day. Second, our snowstorm is poised to begin tomorrow, in theory. Third, I believe we can all breath easier if you are
NOT wanting snow.
First, here is the FOUS data from the 17/00Z GFS...
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41.12N 95.90W
OUTPUT FROM GFS 00Z MAR 17 2006
FL150 FL200 FL250
TTTPTT DPR1R2R3 VVVLI PSQNHDDFF HHSTT1T2T3 W TB IC TB IC TB IC TCCCLB
033001 98778681 00914 260291210 3803029897 S NEG MOD NEG LGT NEG NEG 100087
036002 98798076 02513 260271211 3802019897 S NEG MOD NEG LGT NEG NEG 100077
039001 98808781 02513 260271211 3803019797 S NEG MOD NEG LGT NEG NEG 100063
042003 99789392 02013 240221112 4004019897 S NEG MOD NEG LGT NEG NEG 100060
045002 99809595 04412 210131112 4104029897 S NEG NEG NEG NEG NEG NEG 100050
048002 99839296 03213 210140912 4102029897 S NEG LGT NEG NEG NEG NEG 100044
051006 99859395 03612 210151014 4102019897 S NEG MOD NEG LGT NEG NEG 100033
054006 99879898 08411 200111112 4001019897 S NEG MOD NEG LGT NEG NEG 100033
057013 00939998 03509 200091113 4001009797 S NEG MOD NEG LGT NEG NEG 100033
060005 99949997 -0110 180051114 4000999797 P LGT MOD NEG LGT NEG NEG 100032
063004 99949999 03709 200071013 4000999696 P NEG LGT NEG NEG NEG NEG 100035
066007 99939999 00909 190050914 4099999696 P NEG MOD NEG LGT NEG NEG 100033
069005 99939999 03008 169970915 4199999696 P NEG MOD NEG LGT NEG NEG 100031
072010 99939999 01709 179980815 4199999696 P NEG MOD NEG NEG NEG NEG 100031
075007 99949999 00711 180020714 4099999695 S NEG LGT NEG NEG NEG NEG 100031
078006 99959999 01411 179990714 3898989595 S LGT NEG LGT NEG NEG NEG 100031
081004 98959999 02512 169950613 3698979494 S NEG NEG LGT NEG LGT NEG 100031
084003 98959998 09412 159930513 3697979394 S NEG NEG MOD NEG LGT NEG 100031
087004 98949996 02713 159920416 3597969393 S NEG NEG MOD NEG NEG NEG 100033
090006 98929997 04915 159920215 3397969292 S LGT LGT LGT LGT LGT NEG 100032
093008 98919987 02116 169940116 3197969292 S LGT MOD LGT NEG LGT NEG 100037
096003 97919982 -0217 180000014 3096959291 S LGT MOD LGT NEG LGT NEG 100048
In theory, that would yield to around 7.7 inches of snow.
Whoa... why the decrease in snow totals?!
Well, I've mentioned some of it before and now I'm going to set up the game plan on why we won't see any LARGE amounts of snowfall.
First... a few days ago, the temperatures forecast were a few degrees below freezing at both the surface and 850mb levels. However, now that the storm system has more observation data inserted into the models, the forecast solution expects to see a little warmer temperatures. What does this mean? Well... a few things: A) with the warmer temperature, the snow:water ratio decreases since warmer air can hold more water. That would yield less snow. B) with the warmer temperature, the chances of mixed precipitation increase. You can see that even in the above FOUS bulletin. Before it was forecasting all snow. Now, it's forecasting some sleet. It also wouldn't surprise me to see some big, fat raindrops. C) with the warmer temperature, the ground doesn't have a chance to cool off. Currently the ground temperature is around 40F. Therefore, some of the snow will melt before accumulations begin.
Secondly, blame the southern and central Plains. These locations will see convection (ie thunderstorms) with this system. While the Gulf is technically "open", the convection between us (Nebraska) and the Gulf will steal moisture. With less moisture to work with, less snow will fall.
Third, blame Canada. (I've been wanting to say that!) Seriously, though... an area of high pressure currently north of the Great Lakes is forecast to build (strengthen) and sag southward. With the southerly motion, this will force easterly winds in our direction while shifting the storm track. This means, as the low is forced to track more southward than before... this will keep the heaviest snows away from us. Also, the easterly winds are a dry wind. That's right... yet another dry slot.
In summary, the convection to our south and dry air from our east may spoil our hyped-up storm. There are too many documented cases (according to the local terminal forecast reference notebook) where strong convection in the southern plains steals the northward moisture flow leading to reduced snowfall amounts in the central and northern plains. Furthermore, the strengthening, southward moving high north of the Great Lakes this weekend will be feeding low-level dry air in from the east and also tend to force the surface low on a more southerly track than is optimal for heavy local snow. Together, these factors may well combine to drastically limit local snowfall.
Very heavy snow is likely in upslope regions of the high plains to our west (ie western Nebraska) and perhaps also over portions of KS, but not here.
Now... let's look at some AFDs...
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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
1034 AM CST FRI MAR 17 2006
///snip///
GFS AND NAM THEN SUGGEST A PROLONGED ISENTROPIC LIFT EVENT
CONTINUING THROUGH SUNDAY AS SHORTWV RIDGING SPREADS ACROSS PLAINS
SATURDAY AND THEN UPR FLOW BECOMES EVEN MORE SRLY SUNDAY AS RIDGE
EITHER FLATTENS OUT OR MOVES EAST AND LARGE UPR LOW BEGINS TO DRIFT
EWD. DRY SFC-850 MB FLOW WILL KEEP A SHARP POP GRADIENT NEAR ERN
ZONES BOTH SATURDAY AND SUNDAY BUT NEVERTHELESS THE LIFT FORECAST
APPEARED GREAT ENOUGH TO RAISE MOST POPS FROM SATURDAY THROUGH
SUNDAY. QPF AMOUNTS STILL LOOKED LIKE THEY WILL BE ON THE LIGHTER
SIDE SATURDAY AS FORCING WILL HAVE TO OVERCOME LOW LVL DRY AIR.
TEMPERATURES COULD MODERATE ENOUGH SAT TO ALLOW A CHANGE TO RAIN OR
RAIN SNOW MIX AS FAR N AS A OLU-OMA-HNR LINE BY AFTN WITH PCPN ALL
RAIN FAR S...AGAIN NO BIG CHANGES FM PREV FCST. H6-H7 FRONTOGENESIS
SETS UP AGAIN FROM LATE SAT NIGHT INTO SUNDAY NRN ZONES AS
ISENTROPIC LIFT CENTERED ON 300K SFC CONTINUES. IN ADDITION...
VERTICAL CROSS SECTIONS FROM GFS SHOWED A LONGER PERIOD OF SATURATED
THETA E SFC SURFACES DECREASING WITH HGT OVER MUCH OF THE CWA
INDICATING POSSIBLY HEAVIER QPF DUE TO ELEVATED CONVECTION AND/OR
BANDING. HOWEVER...LOW LVL TRAJECTORIES ACROSS THE ECNTRL AND NERN
ZONES REMAIN QUITE DRY WHICH COULD CONTINUE TO PROVIDE A SHARP BREAK
IN SNOW/PCPN AMOUNTS. NONETHELESS...AS MENTIONED ABOVE FORCING
APPEARED STRONG ENOUGH TO INCREASE MOST POPS SAT NGT THRU SUNDAY.
FORECAST SOUNDINGS SRN ZONES INDICATED RAIN/SNOW MIX OR SLEET
REMAINED POSSIBLE SUNDAY BUT MOVED UP BEGINNING TIME OF MENTION OF
SLEET TO SAT NGT. SINCE HEAVIEST PCPN WRN ZONES WAS CENTERED ON THE
5TH PERIOD DID NOT ISSUE ANY HEADLINES WITH THIS FORECAST
PACKAGE...BUT WILL CONTINUE HIT SNOW HARD IN THE HWO AND FORWARD A
48 HOUR SNOW FORECAST ENDING 12Z MONDAY TO THE WEB SITE. TOTAL
SNOWFALL FROM QPF FROM GFS STILL LOOKS LIKE IT MAY BE OVERALL TOO
HIGH...SPCLY OUTSIDE OF NWRN ZONES...GIVEN MARGINAL TEMPERATURES AND
PROBABLE CONVECTION DVLPG OVER THE SRN PLAINS ROBBING SOME LOW LVL
MOISTURE FOR SRN ZONES AND DRY ERLY/ESERLY FLOW OVER ECNTRL/NERN
ZONES.
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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
401 AM CST FRI MAR 17 2006
///snip///
THE REGION WILL THEN BE HEADED TOWARD A MUCH MORE ACTIVE PATTERN
OVER THE NEXT FEW DAYS AS THE WEST COAST WAVE WILL DIG OVER THE
INTERMOUNTAIN WEST REGION SATURDAY INTO EARLY SUNDAY...BUT WILL THEN
KICK EAST INTO THE PLAINS LATE SUNDAY INTO MONDAY. AHEAD OF THIS
WAVE...THE STAGE WILL BE SET FOR A PROLONGED PERIOD OF ISENTROPIC
LIFT AND WAA/THETA E ADVECTION ACROSS NEBRASKA AND NORTHERN KANSAS
STARTING TONIGHT AND LASTING INTO EARLY SUNDAY. INDIVIDUAL SPOKES
OF ENERGY WILL ROTATE OUT OF THE INTERMOUNTAIN WEST AND INTO THE
PLAINS THROUGH EARLY SUNDAY AND WILL PROVIDE THE EXTRA KICK TO PUSH
MOISTURE INTO THE DENDRITIC LAYER AND BEGIN PRECIPITATING. LOOKS AS
THOUGH LIGHT TO OCCASIONALLY MODERATE PRECIPITATION WILL BEGIN AFTER
MIDNIGHT TONIGHT AND WILL NOT STOP THROUGH EARLY SUNDAY. THE MAIN
QUESTION AT HAND IS WHERE THE TEMPERATURE PROFILE WILL SUPPORT RAIN
VERSUS SNOW. LOOKING AT THICKNESS PROGS...FORECAST SOUNDINGS AND
ESTIMATED SURFACE TEMPERATURES IT APPEARS AS THOUGH SNOW WILL BE THE
DOMINATE PRECIP TYPE ALONG AND NORTH OF INTERSTATE 80 WHILE RAIN
DOMINATES ACROSS NORTHERN KANSAS WITH A MIX PREVAILS BETWEEN THESE
AREAS. PRECIP RATES SHOULD BE LIGHT ENOUGH THROUGH EARLY SUNDAY
THAT SNOW ACCUMULATIONS PER 6 HOURS WILL BE UNDER 2 TO 3
INCHES...BUT SNOW ACCUMULATIONS OVER 5 TO 7 INCHES MAY BE POSSIBLE
NEAR ORD BY EARLY SUNDAY AFTERNOON. THIS WILL HAVE TO BE WATCHED
VERY CLOSELY BY THE DAY CREW TO SEE IF SNOW RATES WILL BE HIGH
ENOUGH TO TRIGGER ANY TYPE OF HIGHLIGHT.
THE UPPER LOW THEN TRACKS ACROSS THE PLAINS SUNDAY NIGHT INTO EARLY
MONDAY. THE MODELS ARE HAVING TROUBLE AS USUAL AT KEEPING
CONSISTENT WITH THE TRACK OF THIS SYSTEM. NOT EXTREMELY CONFIDENT
IN ANY SOLUTION AT THIS POINT AS THE MODELS ARE VARYING FROM A
CENTRAL PLAINS TRACK TO A SOUTHERN PLAINS TRACK. WILL CHANGE LITTLE
OVER THIS TIME PERIOD GIVEN THE UNCERTAINTY BUT WILL KEEP HIGH
CHANCES OF PRECIP GOING THROUGH MONDAY WITH SNOW ACCUMULATIONS
EXPECTED. GIVEN THIS SYSTEM IN COMBINATION WITH THE PROLONGED
PERIOD OF PRECIP LEADING UP TO THE UPPER LOW MOVING ACROSS THE
REGION...THE DAY CREW MAY NEED TO ISSUE A WINTER STORM WATCH FOR
LATE SUNDAY INTO MONDAY AS WELL.
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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTH PLATTE NE
257 AM CST FRI MAR 17 2006
///snip///
MAJOR WINTER STORM IS STILL APPROACHING...AND LOOKS TO TAKE AIM AT
MOST OF THE FORECAST AREA OVER THE WEEKEND INTO THE START OF NEXT
WEEK.
PACIFIC MOISTURE IS STREAMING ACROSS THE ROCKIES THIS MORNING WITH
SCATTERED MID AND HIGH LEVEL CLOUDS BEGINNING TO CROSS THE REGION. AT
THE SURFACE PESKY STRATUS BLANKETS CENTRAL NEBRASKA STRETCHING INTO
PORTIONS OF NORTHWESTERN NEBRASKA. STRATUS EXPECTED TO SLOWLY ERODE
FROM THE SOUTHWEST TODAY...HOWEVER THE NORTHEASTERN ZONES WILL
LIKELY REMAIN CLOUDY MOST OF THE DAY. VTN REMAINED UNDER STRATUS
ALL DAY YESTERDAY AND HAD A HIGH OF 27 DEGREES...AND EXPECT THE
STRATUS WILL KEEP HIGHS DOWN AGAIN.
WINDS WILL CONTINUE TO VEER THIS MORNING BECOMING SOUTHEAST...AND
INCREASING TO BREEZY BY AFTERNOON. THE SOUTHEAST WINDS WILL BEGIN TO
USHER IN GULF MOISTURE...WHICH WILL CONTINUE TO INCREASE THE NEXT
SEVERAL DAYS.
MAIN TROUGH OF LOW PRESSURE WILL DIVE ALONG THE PACIFIC COAST TODAY
REACHING THE DESERT SOUTHWEST BY SATURDAY. THEN THE TROUGH WILL
MOVE ON AND ACROSS THE SOUTHERN PLAINS TO BEGIN NEXT WEEK. TROUGH
WILL SENT SEVERAL WAVES AHEAD...INFLUENCING THE REGION STARTING
SATURDAY.
WATCH WAS ISSUED DURING THE DAY SHIFT YESTERDAY FOR AREAS ALONG AND
NORTH OF I 80...AND ALTHOUGH CONTEMPLATED UPPING THE START TIME...
HAVE DECIDED TO LEAVE AS IS. SATURDAY AFTERNOON AND EVENING...
GENERALLY LIGHT SNOW OR RAIN...SOUTH...WILL BEGIN HOWEVER ONLY LIGHT
AMOUNTS EXPECTED. MAJOR WAVE INFLUENCES THE REGION BY SATURDAY
NIGHT WITH SIGNIFICANT SNOWFALL POSSIBLE. SUNDAY WILL CONTINUE TO BE
SNOWY...ALTHOUGH WITH HIGH MARCH SUN ANGLE...ACCUMULATIONS MAY NOT
BE THAT HIGH. BY SUNDAY NIGHT ACCUMULATIONS WILL GET CRANKED UP
AGAIN.
MONDAY WILL BEGIN TO FINALLY SEE THE SNOW DIMINISH. THE UNUSUALLY
LONG DURATION IS CAUSE FOR CONCERN AS SOME AREAS MAY SEE UP TO A
FOOT OR MORE. MARCH 24 HR RECORD SNOWFALL FOR BOTH VTN AND LBF ARE
GREATER THAN A FOOT THUS HIGH SNOWFALL TOTALS VERY POSSIBLE THIS TIME
OF YEAR. WILL CONTINUE TO MONITOR THIS MAJOR WINTER STORM.
LITTLE CHANGES DONE FOR THE REMAINDER OF THE EXTENDED...HOWEVER
MODELS NOW BRINGING ANOTHER...ALTHOUGH WEAKER...SYSTEM FOR LATE IN
THE WEEK. WILL OPT TO WAIT FOR ANOTHER RUN TO SEE A MORE CONSISTENT
TRACK.
Here are the HWOs from OAX, GID, and LBF, respectively. I believe these forecast numbers are relatively reasonable...
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HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
511 AM CST FRI MAR 17 2006
///snip///
SATURDAY THROUGH THURSDAY
SNOW IS LIKELY SATURDAY...ESPECIALLY OVER NORTHEAST NEBRASKA WHERE
THERE COULD BE SOME LIGHT ACCUMULATIONS BY EVENING. SLIGHTLY
WARMER TEMPERATURES OVER SOUTHEAST NEBRASKA COULD EITHER CHANGE
THE SNOW TO RAIN OR MELT MUCH OF THE SNOW AS IT FALLS LIMITING ANY
SNOW ACCUMULATIONS. OVERALL PRECIPITATION AMOUNTS SHOULD BE LIGHTER
OVER SOUTHWEST IOWA.
DURING THE PERIOD SATURDAY NIGHT THROUGH SUNDAY NIGHT...THERE IS
A HIGHER POTENTIAL FOR ACCUMULATING SNOW.
PRELIMINARY INDICATIONS SUGGEST THAT POTENTIAL 48 HOUR SNOWFALL
AMOUNTS FROM SATURDAY MORNING THROUGH MONDAY MORNING COULD BE 7 TO
12 INCHES FROM MUCH OF NORTHEAST NEBRASKA SOUTHEASTWARD TO DAVID
CITY AND SEWARD. MOST OF THE REST OF EASTERN NEBRASKA COULD SEE
AMOUNTS OF 4 TO 7 INCHES. ACROSS SOUTHWEST IOWA AND THE SOUTHERN
PART OF SOUTHEAST NEBRASKA...AMOUNTS FROM 2 TO 5 INCHES ARE
POSSIBLE AS A MIX OF RAIN OR SLEET COULD LIMIT SNOW ACCUMULATIONS.
ACTUAL SNOW DEPTHS MAY VARY BECAUSE THERE MAY BE SOME MELTING...
AND IT WILL PROBABLY NOT BE SNOWING DURING THIS ENTIRE PERIOD.
LATER FORECASTS WILL PROVIDE ADDITIONAL INFORMATION AND POSSIBLE
ADJUSTMENTS TO ACCUMULATIONS.
ADDITIONAL SNOW IS POSSIBLE MONDAY INTO EARLY TUESDAY.
A LARGE UPPER LEVEL SYSTEM MOVING ONTO THE WEST COAST WILL BE RESPONSIBLE
FOR THE UNSETTLED WEATHER EXPECTED THROUGH MONDAY. DISTURBANCES
LIFTING NORTHEAST AHEAD OF THE MAIN SYSTEM WILL BRING SEVERAL
PERIODS OF SNOW THIS WEEKEND WITH THE MAIN SYSTEM ITSELF FORECAST
TO MOVE ONTO THE PLAINS MONDAY.
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HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HASTINGS NE
546 AM CST FRI MAR 17 2006
///snip///
SATURDAY THROUGH THURSDAY
A PROLONGED PERIOD OF ACCUMULATING SNOW IS EXPECTED TO START SATURDAY
NIGHT AND MAY LAST THROUGH EARLY TUESDAY. TOTAL SNOW ACCUMULATIONS
WELL OVER 6 INCHES MAY BE POSSIBLE OVER THIS TIME PERIOD. STRONG
WINDS MAY ALSO CAUSE AREAS OF BLOWING AND DRIFTING SNOW RESULTING
IN REDUCED VISIBILITIES AND HAZARDOUS DRIVING CONDITIONS THROUGH
THE PERIOD.
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HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORTH PLATTE NE
531 AM CST FRI MAR 17 2006
///snip///
SATURDAY THROUGH THURSDAY.
A POWERFUL LATE WINTER STORM CONTINUES TO TAKE AIM ON WESTERN AND
NORTH CENTRAL NEBRASKA. SNOWFALL WILL BEGIN EARLY SATURDAY MORNING
OVER PORTIONS OF WERSTERN NEBRASKA. THE HEAVIEST SNOWFALL IS
EXPECTED OVER THE AREA SUNDAY INTO EARLY MONDAY MORNING AS THE
MAIN UPPER LOW MOVES OUT OF THE FOUR CORNERS AREA ONTO THE CENTRAL
PLAINS. ABUNDANT GULF MOISTURE WILL BE DRAWN NORTH INTO THE
NORTHERN AND CENTRAL PLAINS AND SNOWFALL TOTALS IN EXCESS OF 6 INCHES
WILL BE POSSIBLE WITH THIS STORM.