Area Forecast Discussion
Issued by NWS Jackson, MS

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286
FXUS64 KJAN 270550
AFDJAN

Area Forecast Discussion
National Weather Service Jackson MS
1150 PM CST Sun Feb 26 2017

...ACTIVE WEATHER EXPECTED THROUGH MID WEEK...

.UPDATE...
Updated for 06Z aviation discussion

&&

.AVIATION...
06Z TAF discussion:
A complex of SHRA/TSRA continues to approach the region from NW
tonight and will progress through the entire area throughout the
period. Flight categories will deteriorate as the complex
approaches each site. Expect MVFR/IFR conditions to prevail with
some sites falling briefly to LIFR. Some improvement is expected
tomorrow afternoon but conditions will degrade once again late in
the period due to low CIGs and BR. /jpm3/


&&

.DISCUSSION...

The latest few runs of the HRRR have been showing rain showers
start to develop in southern Louisiana and move into the
southeastern portion of region in the early morning hours. An
increase to the forecasted POPs have been made to reflect this
latest development. Take note that a slight chance of thunder
can`t be ruled out for this area.

The progression of the disturbance that is currently
moving through central Arkansas and Northern Mississippi is still
timed to move through our region shortly after midnight. /12/

Prior discussion below:

Now through the day tomorrow:

It has been another very dry (in terms of humidity) day across the
region with temperatures more pleasant than yesterday as the
overall trend to above average readings has kicked back in.
Despite southeast winds at the surface, moisture has yet to return
to the boundary layer and the combination of the somewhat gusty
winds and low relative humidity is again increasing fire weather
concerns. More on the specifics of the fire concerns is mentioned
in the dedicated section below. Fortunately, fire danger will not
be a concern anytime in the near future (after this afternoon)
since starting tonight the increasing southerly flow above the
surface will be bringing back moisture from the Gulf of Mexico
quickly.

A fast-moving upper level disturbance headed at the region tonight
will be the impetus for the rapid moisture return as the
disturbance effectively shoves the nearby surface high quickly off
to the east and strengthens return flow up the Lower Mississippi
Valley. Model consensus suggests the current rash of showers
breaking out to our west will consolidate and grow this evening
into a larger complex of showers and thunderstorms, which will
then translate east into western zones before dawn. After daybreak
this convection should continue to shift east through the heart
of the region, probably anchored at the nose of maximum warmth and
moisture advection a few thousand feet above the surface (which
basically should be along the I-20 corridor). Instability
overnight into mid morning tomorrow should be based above the
surface, greatly limiting the potential for severe weather (although
some small hail is still possible in this time window over
western zones). More worrisome will be mid morning through early
afternoon tomorrow as there will likely be an outflow boundary
laid down over southern zones by the main convection where non-
negligible surface-based instability could build and help trigger
some storms more capable of severe weather. The available suite of
high resolution guidance is not in high agreement concerning
convective evolution tomorrow, but we feel over central and zones
it is still worth mentioning the potential for at least one or two
storms getting up to severe potential.

By late in the afternoon tomorrow the main upper level short wave
will be shifting to the east and subsidence in its wake should be
shutting down the threat for deep convection. Many locations,
especially over east-central MS, will have struggled to warm much
before this time, but will likely get a chance to make a run up
toward 70 degrees before the afternoon is totally done. /BB/

Monday night through next week:

We will be looking at an active period with rain chances coming for
Monday night through Wednesday night with mild temperatures.
This will be followed by dry and cool weather for Thursday through
Saturday before some rain comes back in the south on Saturday night.
The best severe potential looks to be on Wednesday with the cold
front passage. There will be some limited severe potential for
Tuesday night in the northwest.

On Monday night convection will be increasing over the northern
counties in the vicinity of the warm front and the upper level jet.

On Tuesday a midlevel trough will be pushing toward the Plains. This
will push a cold front toward the Ozarks for Tuesday night. Surface
based instability will be prevalent with lapse rates 7-8C,
increasing low level shear 35 knots and deep layer shear 60-70
knots in the delta region, showalter indices -2 to -4, vertical
totals 28-30, and most unstable CAPE around 1800 j/kg. The main
axis of the upper jet will be north of the region. However we will
have a good low level jet of around 40 to 50 knots. With warm
heights over the region we will be rather capped with the approach
of the midlevel trough, which will affect the convective coverage
in the south half. The best chance of storms will be in the
northwest for Tuesday night with the approach of the system. SPC
has a marginal risk for severe storms over our northwest Delta
region with a slight risk just to our northwest. With this in
mind will keep a limited severe threat graphic for the northwest
Delta region with the approaching system for Tuesday night. The
primary risks will be damaging winds, and hail.

On Wednesday the midlevel trough will be pushing toward the
region from the Plains. This will send a cold front into the
region. Ahead of the cold front we will have low level shear 30-40
knots, deep layer shear 60-70 knots, storm relative helicity of
200-300, VT 28- 30, and showalters -2 to -4. This will be enough
for some tornado potential across the region ahead of the cold
front. SPC has put a 30 percent risk for our northern counties and
a 15 percent risk elsewhere. So with this in mind will keep the
Elevated risk across the north and limited risk across the central
and south. So will keep the primary risk being damaging winds,
hail and a tornado can not be ruled out. Conditions look to favor
a squall line to develop along the frontal boundary as it sweep
across the region with some damaging winds. The front will sweep
across most of the region by Wednesday night. Models were still
having some timing issues with the frontal passage. The rains will
end from the northwest in the wake of the front on Wednesday
night. Cool High pressure will build in from the plains on
Thursday into Friday. On Saturday high pressure will track east of
the region which will bring back southerly low level return flow.
Pwats will increase from the west to around one inch, which will
help some isolated showers to develop across the south on Saturday
night.

As far as temperatures are concerned we will be looking at a
warming trend as we push through the work week with highs peaking
at the upper 70s to the lower 80s on Tuesday. Lows will rise to
the 60s by Tuesday night. In the wake of the cold front highs will
be in the 60s for Thursday through Saturday. Lows will dip into
the 40s for Wednesday night then 30s and 40s for Thursday night
and Friday night. Lows will recover into the 40s and 50s for
Saturday night.

Looking into Sunday into early next week it looks like our rain
chances will spread across the region on Sunday into Monday. This
will be associated with an strong upper trough to the north which
will drag a cold front through for early next week./17/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       52  72  63  81 /  66  81  23  20
Meridian      47  70  61  79 /  43  81  23  20
Vicksburg     54  74  64  82 /  66  90  25  23
Hattiesburg   49  75  63  81 /  39  66  16  12
Natchez       57  77  66  82 /  51  74  18  20
Greenville    50  68  62  78 /  88  70  45  34
Greenwood     49  67  61  80 /  79  87  44  33

&&

.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.

&&


$$

JPM3



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