Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson MS
415 am CST Monday Dec 22 2014
Short term...today through Tuesday night...the upper trough over
the nation's middle-section will continue to deepen over the next 48
hours as it slowly nudges east towards region. The first spoke of
energy associated with it is prognosticated to push a cold front east into
and through the region late this afternoon into tonight. As these
features approach the area late today...increasing isentropic
upglide...further aided by a warm front lifting north from the
coast...will result in scattered showers over the area through the
course of the day.
I'll maintain the limited potential for severe storms across the
forecast area for this evening into tonight. With the cold
front near the Mississippi River this evening...modest levels of
instability are expected over the forecast area ahead of it with
near 60 dew points oozing up along to just north of the Interstate
20 corridor...and middle/upper 50s dew points expected along the
Highway 82 corridor. Although much of this activity currently looks
to be elevated...the instability mentioned above...in addition to
50-60 knots of deep layer wind shear could yield some severe storms
during this time. With the best potential for any convection to
become surface-based being across southeast Mississippi during this
time...a tornado cannot be ruled out there.
Showers and storms remain in the forecast on Tuesday and Tuesday
night as the upper trough/low approaches and swings into the
forecast area. As this happens...a surface low is prognosticated to
develop on the tail end of Monday night's cold front...and race
northeast through the County Warning Area Tuesday afternoon and evening. Again
during this time...a limited potential for severe storms will exist
over at least the eastern two thirds of the forecast area.
Once again...very favorable moisture return with dew points climbing
into the low and middle 60s...strong forcing...and ample wind shear
will be the primary players in any severe weather potential Tuesday.
However...uncertainty remains in the models concerning the exact
track of this surface low across the County Warning Area. That said...models have
nudged east this go around.
The European model (ecmwf) is slightly further east...but the GFS is now the furthest
east. If correct...this GFS solution would limit any severe
convection to namely far east central and southeast Mississippi.
Due to this overall nudge east in the low's track by the
models...i'll follow suit in terms of the severe weather potential statement and focus the better
severe potential generally over the area along and east of a Natchez
to Jackson to Columbus line for this package. All that said...if
the low continues to track further to the east or if intense
convection along the coast cuts off moisture to the area...it could
potentially inhibit any severe weather potential over the County Warning Area.
Activity should wane in intensity as we move through Tuesday night
into early Wednesday morning as northerly flow quickly advects
colder drier air into the region. Light to moderate rain will
continue into early Wednesday morning behind the surface low...as
the upper trough/low begins swinging across the area squeezing out
any remaining moisture over the area. /19/
Long term...Wednesday through this weekend...the consensus model
solution is trending toward the trough responsible for pushing
through Tuesday nights cold front closing off before it clears the
lower MS valley. This evolution will tend to linger clouds and light
precipitation or drizzle longer behind the frontal boundary on
Wednesday...especially north of Interstate twenty. If temperatures
were truly cold then this could increase odds of a few flakes...but
alas temperatures just will not be cold enough...even in far
northwest arklamiss Delta zones.
But that does not mean the air coming in behind the front for
Christmas evening will not be chilly...because readings will be a tad
below normal through Christmas day. No worries this year about 70
degrees readings putting you out of the Holiday spirit. Skies will
be clear to partly cloudy too (after clouds gradually clear out
during the day wednesday).
Following Christmas day temperatures will moderate back to a little
above normal ahead of another cold front approaching for Saturday.
Rain associated with this front could begin in western zones as
early as during the day Friday...but more likely will wait until
Friday night or Saturday for most folks. Previously...this looked
like a frontal passage with little fanfare but now the latest op
Euro run has impressive cyclogenesis right atop the region and has
the atmosphere responding with lots of shower and embedded
thunderstorm production. For now...this latter solution is an
outlier...but the solution is more than conspicuous considering this
models usual good performance. Considering such...model blends have
been adjusted somewhat in the direction of the latest Euro for the
Saturday through Saturday night period.
For the start of next week there still is potential for a
consistently colder regime to build into our region...but latest
indications are that this evolution may be delayed closer to the
start of the New Year. In the interim inclement conditions may
persist a while longer. /Bb/
Aviation...IFR to MVFR ceilings and/or visibilities are being
observed at sites this morning as a result of low stratus and/or
patchy fog. Patchy fog will dissipate after sunrise this
morning...but MVFR ceilings are expected to continue through the
forecast period. Increasing convection through the period will also
bring a degradation in flight categories when observed on station.
Winds today will be southerly between 10-15 knots will higher gusts.
Preliminary point temps/pops...
Jackson 68 55 66 45 / 28 30 83 91
Meridian 66 58 69 51 / 36 38 84 98
Vicksburg 69 53 64 40 / 23 22 82 85
Hattiesburg 71 61 74 53 / 41 28 88 81
Natchez 69 56 66 42 / 20 18 86 77
Greenville 63 49 61 41 / 35 55 70 93
Greenwood 64 51 63 43 / 44 62 71 96